0...? 1a ,
3 . a. ‘
$51. a?!
11.3.

2:}. ‘ . , V
. . . . ‘ . . U , . ‘ {Taibrfu
. ‘ . , al...ix a...
V . 4.91., hr.” V
V ‘ ‘ . 3..»....§«..muwhcf

 

.

.1517. 3...: 9. o
,...n.w.m.mfi:fl1.
‘ a !.!\..9t I‘ ‘

21...}:
‘ . v!

o. .3151.

.2 k..\s v

hbuhfl 137 r
?i

to

In}... ‘2
, . 1.x-
, 32.2.:
V I:

 

\ A 358:.
. ..1 :x!

:

tux!
. )xrtv‘

1.x...

. 1‘;

3.6;:
it!
:0
‘1!
‘1...
If

‘3‘!

 

l

 

THEfi‘i-fi

a
t m {‘3

 

J
M

LEEERARY " W
Michigan State
University

Willi"! m." m

1121i! {MINIMUM Ill!)Ill/Illlllllll

3 1 93 01390 4390

 

 

 

 

 

 

This is to certify that the

dissertation entitled

Effect of Shoot Number and Crap Load on
Dry Matter Partitioning and Canopy
Morphology of Potted Chambourcin

Grapevines
presented by

David Philip Miller

has been accepted towards fulfillment
of the requirements for

Ph D Ckwfifin_HorticuLture

 

Major profe or

Date March 11% 1995

MS U i: an Affirmative Action/Equal Opportunity Irun'mrion 0-12771

 

I.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MSU I. An Affirmative WM Oppomnlv Intuition

______—_———-—

 

 

 

 

EFFECT OF SHOOT NUMBER AND
CROP LOAD ON DRY MATTER PARTITIONING
AND CANOPY MORPHOLOGY OF
PO'l'I'ED CHAMBOURCIN GRAPEVINES

By

David Philip Miller

A DISSERTATION
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Horticulture

1995

ABSTRACT

EFFECT OF SHOOT NUMBER AND
CROP LOAD ON DRY MATTER PARTITIONING
AND CANOPY MORPHOLOGY OF
POTTED CHAMBOURCIN GRAPEVINES
By

David Philip Miller

The effects Of shoot number and crop load on canopy morphology, shoot
fruitfulness and dry matter production were studied in potted Chambourcin
grapevines. Increasing shoot number per vine increased early-season leaf area but
had no effect on dry matter production until veraison. Between veraison and harvest,
continued carbohydrate sink activity caused vines with greater shoot numbers to
produce about 20 % more dry matter than single-shoot vines. Greater shoot numbers
caused profound alterations in canopy morphology. ' Three- and six- shoot vines had
shorter shoots, smaller leaves and lower specific shoot and leaf weight than did one-
shoot vines, but greater shoot length and leaf area per vine. Flower cluster size and
flower number per cluster were also reduced with increasing shoot numbers leading to
a reduction in shoot fruitfulness but an increase in flower number per vine.

Growing vines with one- or four- shoots and no clusters (1/0 and 4/0), one-
shOOt and one—cluster (1/1), or four- shoots and one- (4/1), two- (4/2), three- (4/3) or
four- (4/4) clusters, demonstrated that shoot number had a greater influence on
canopy morphology than crop load. Four-shoot vines had shorter shoots and smaller
leaves than did one-shoot vines, but crop load had little effect on most canopy

parameters. Dry matter production was linearly related to berry number at harvest

even though differences among treatments were small. Dry matter used in fruit
production was derived from preferential partitioning of carbon to fruit at the expense
of vegetative tissues, and at high crop loads, an increase in dry matter production
relative to low crop load vines, particularly between veraison and harvest.

Increasing shoot number and early-season leaf area does not lead to greater
early-season dry matter production. Increasing shoot number does alter canopy
morphology and allow the vine to set more fruit. This increases the possibilities to
balance the crop load with the vine’s dry matter production capacity. As
carbohydrate sink strength increases to a point, dry matter production per vine
increases, maximizing the potential for production of both dry matter and fruit.
Balancing carbon partitioning to fruit and vegetative tissues maximizes sustained fruit

production.

iii

DEDICATION

Dedicated to good friends, good times and good wines

ACKNOWLEDGEMENTS

I would like to thank my parents for their support and encouragement to
pursue higher education from the outset -- they got the ball rolling; my wife Sandy,
for all Of her help in data collection and preparation of the dissertation, and more
importantly, her support and patience during my degree program; the members Of my
Guidance Committee for their time and suggestions; the Michigan Grape and Wine
Industry Council for supporting this research; the many people who have freely given
advice and/or friendship; and my friend and colleague, Stan Howell for his support,
encouragement and guidance over the last decade and a half, and for sharing his

philosophy Of science and life with me.

TABLE OF CONTENTS

LIST OF TABLES ...................................... x
LIST OF FIGURFS ..................................... xii
LIST OF SYMBOLS, ABBREVIATIONS OR NOMENCLATURE ...... xv
LITERATURE REVIEW .................................. l
CANOPY DEVELOPMENT ............................ 3
FRUITFULNESS ................................... 5
CARBOHYDRATE RELATIONS ......................... 6
MINIMALLY PRUNED VINES ......................... ll
LITERATURE CITED ............................... 14

1. AN INEXPENSIVE, WHOLE PLANT, OPEN GAS EXCHANGE
SYSTEM FOR THE MEASUREMENT OF Pn IN PO'ITED

WOODY PLANTS ................................ 19
ABSTRACT ..................................... 19
INTRODUCTION ................................. 19
MATERIALS AND METHODS ......................... 22
Chamber Construction ................ - ........... 22
Chamber Calibration ............................ 26
Chamber Use For Pn Measurement ................... 26
Single Leaf Pn Measurements ...................... 27

vi

PLANT MATERIALS ............................... 27

RESULTS AND DISCUSSION ......................... 28
CONCLUSION ................................... 30
LITERATURE CITED ............................... 31
EFFECT OF SHOOT NUMBER ON POTTED GRAPEVINES: I.
CANOPY DEVELOPMENT AND MORPHOLOGY ........... 37
ABSTRACT . . .‘ .................................. 37
INTRODUCTION ................................. 38
MATERIALS AND METHODS ......................... 40
Plant Material ................................ 40
Leaf Area and Canopy Measurements ................. 41
Vine Dry Weight .............................. 41
Photosynthesis ............................... 41
Data Analysis ................................ 42
RESULTS ...................................... 42
Leaf Area .................................. 42
Shoot Growth ................................ 44
Flower Cluster Development ....................... 44
Dry Weight of Vines ........................... 45
Photosynthesis ............................... 45
DISCUSSION .................................... 46
CONCLUSION ................................... 49
LITERATURE CITED ............................... 50

vii

EFFECT OF SHOOT NUMBER ON POTTED GRAPEVINES: H.

DRY MATTER ACCUMULATION AND PARTITIONING ...... 60
ABSTRACT ..................................... 60
INTRODUCTION ................................. 61
MATERIALS AND METHODS ......................... 62
Plant Material ................................ 62
Vine Dry Weight .............................. 63
Leaf Area .................................. 64
N on-Structural Carbohydrate Analysis ................. 64
Data Analysis ................................ 65
RESULTS ...................................... 65
Leaf and Shoot Dry Weight ....................... 65
Root and Trunk Dry Weight ....................... 66
Total Vine Dry Weight .......................... 66
Specific Leaf and Shoot Weights .................... 67
Root Dry Weight cm’2 Leaf Area .................... 67
Weight Ratios of Canes (Vine Size) to Storage Organs ....... 68
Starch Data ................................. 68
DISCUSSION .................................... 68
CONCLUSION ................................... 72
LITERATURE CITED ............................... 74

INFLUENCE OF SHOOT NUMBER AND CROP LOAD ON
POTTED CHAMBOURCIN GRAPEVINES. I: MORPHOLOGY
AND DRY MATTER PARTITIONING ................... 82

viii

INTRODUCTION ................................. 83
MATERIALS AND METHODS ......................... 85

Plant Material ................................ 85

Vine Dry Weight .............................. 85

Leaf Area .................................. 86

Fruit Chemistry ............................... 86

Data Analysis ................................ 86

RESULTS AND DISCUSSION ......................... 87
Canopy Morphology ............................ 87

Dry Weight Partitioning ......................... 88

Yield ..................................... 93

Carbohydrate Source/ Sink Relationships ................ 95
CONCLUSION ................................... 96
LITERATURE CITED ............................... 98
CONCLUSION ....................................... l l 1
APPENDIX A ........................................ 115
APPENDIX B ................................ i ........ 117
APPENDIX C ........................................ 121

ix

LIST OF TABLES

Table 1. Shoot and cluster number treatments used on potted Chambourcin
grapevines ........................................... 101

Table 2. Dry weight differences Of vine organs between selected crop load treatments
of Chambourcin grapevines. Vines with lower crop loads were subtracted from vines
with higher crop loads. A negative value indicates that the organ was Of greater size
in vines with lower crOp load ............................... 101

Table 3. Components Of yield for potted Chambourcin grapevines with one shoot and
one cluster (1/1), or four shoots and one (4/1), two (4/2), three (4/3) or four (4/4)
clusters ............................................. 102

Table 4. Crop load and leaf area gram-1 fruit fresh weight for Chambourcin
grapevines with one shoot and one cluster (1/1), or four shoots and one (4/1), two
(4/2), three (4/ 3) or four (4/4) clusters ......................... 102

Table 5. Fruit chemistry of Chambourcin grapevines with one shoot and one cluster
(III), or four shoots and four (4/1), two (4/2), three (4/3) or four (4/4) clusters 102

Table 1. Starch concentration (mg g-l dry weight) of vegetative tissues Of
Chambourcin grapevines with one-, three- or six-shoots ............... 115

Table 2. Total starch content (mg) Of vegetative tissues Of Chambourcin grapevines
with one-, three- or six-shoots ............................... 116

Table 1. Photosynthesis data Obtained from m easuring individual leaves of
Chambourcin grapevines with one or four shoots and no fruit (1/0 and 4/0,
respectively); one shoot and one cluster (1/ 1) or four shoots with one (4/1), two (4/2),
three (4/3) or four (4/4) clusters. VPD = vapor pressure deficit (lma); A = net C02
assimilation rate (umol m-2 sec-l); Gs = stomatal conductance (mmol C02 m-2 sec-
l); E = transpiration rate (mmol H20 m-2 sec-1); WUE = water use efficiency (mol
C02/mo] H20); Ci = intracellular CO2 concentration (umol C02/mol C02); and Gm
= mesophyll conductance (mmol CO2 m-2 sec-l) ................... 117

Table 2. CO2 assimilation by Chambourcin grapevines with one shoot with 0 (1/0)
or one (1/ 1) cluster or four shoots and zero (4/0) or four (4/4) clusters. Data were

collected using either the whole plant gas exchange system described in Chapter 1 or
a Parkinson broad leaf chamber .............................. 119

Table 1. Parameters effectiving fruitfulness of potted Chambourcin grapevines with
one shoot and one cluster (1/1) or four shoots and one (4/1), two (4/2), three (4/3) or
four (4/4) clusters ...................................... 121

xi

LIST OF FIGURES

CHAPTERI

Figure 1a. Whole plant gas exchange system showing both chambers, air supply
system, location of air flow measurement ports and IRGA hookup ......... 33

Figure 1b. Detail Of chamber base showing, non-porous foam collar sealing the
trunk, latches for fastening chamber halves, air diffuser, and attachment of Mylar
balloon with elastic band. Inset shows detail of elastic band positioning and
attachment ........................................... 33

Figure 2. Relationship between actual flow rate (as determined by dilution of C0,)
and flow as measured by hot-wire anemometer ..................... 34

Figure 3. CO, assimilation (A) of Chambourcin grapevines. Measurment using a
Parkinson broad-leaf chamber (I); or whole-plant chambers (O). A) C02
assimilation per unit leaf area (mmol C02 111'2 sec") and; B) CO; assimilation per

vine (mmol CO2 vine‘1 sec“). Bars represent the LSD at p=.05 .......... 35
Figure 4. Relationship between whole vine CO2 uptake at veraison and vine dry
weight at harvest for potted Chambourcin grapevines ................. 36
CHAPTER II

Figure 1. Leaf area (cmz) for individual shoots (A), whole vines (B) and leaves (C) of
potted Chambourcin grapevines with 1 shoot (I), 3 shoots (O), or 6 shoots (A).
Bars represent the LSD at p=0.05 ............................ 53

Figure 2. Rate Of leaf area increase (cm2 day “) (A) and leaf number
of individual shoots (B) and whole (C) Chambourcin grapevines with 1 shoot (I), 3
shoots (O), or 6 shoots (A). Bars represent the LSD at p=0.05 .......... 54

Figure 3. Length (cm) of individual shoots (A), entire vines (B) and intemodes (C)

Of potted Chambourcin grapevines with I shoot (I), 3 shoots (O), or 6 shoots (A).
Bars represent the LSD at p=.05 ............................. 55

xii

Figure 4. Relationship between individual cluster length and leaf size (A); flower
cluster length per shoot and shoot length per shoot (B); and flower cluster length per
vine and shoot length per vine (C) from bud burst to bloom in potted Chambourcin
grapevines ........................................... 56

Figure 5. Dry weight Of vine organs at harvest of potted Chambourcin grapevines
with 1, 3 or 6 shoots. Bars followed by different letters are different at p=0.05 57

Figure 6. Relationship between leaf area and vine dry weight (g) of potted
Chambourcin grapevines with I shoot (I), 3 shoots (O), or 6 shoots (A) . . . 58

Figure 7. A) Single leaf CO2 assimilation rate (A) (mmol C02 m2 s-l); B) whole
vine A (mmol C02 vine-l sec-1 ), and ; C) the relationship between whole vine A
and vine dry weight (g) at harvest, measured with whole-plant chambers using potted
Chambourcin grapevines with I shoot (I), 3 shoots (O), or 6 shoots (A) . . . 59

CHAPTERHI

Figure 1. Dry weight (g) of A) leaves; B) shoots; and C) shoots and leaves combined
of potted Chambourcin grapevines with I shoot (I), 3 shoots (O), or 6 shoots (A).
Bars represent the LSD at p=0.05 ............................ 77

Figure 2. Dry weight (g) of A) trunks; B) roots; C) roots and trunks combined, and;
D) whole Chambourcin grapevines with 1 shoot (I), 3 shoots (O), or 6 shoots (A).
Inset in "D" shows the relationship between dry weight (g) and shoot number at
harvest (y = 3.596lx + 83.5382; 1'2 = .5263) .................... 78

Figure 3. Relationship between A) leaf area and specific leaf weight; B) shoot length
and specific shoot weight; and C) leaf area and shoot dry mass for Chambourcin
grapevines with I shoot (I), 3 shoots (O), or 6 shoots (A). Inset in "B” shows
change in specific shoot weight over the growing season ............... 79

Figure 4. The relationship between root dry weight (g) and leaf area (cm2) of potted
Chambourcin grapevines with I shoot (I), 3 shoots (O), or 6 shoots (A). Bars
represent the LSD at p=0.05 ............................... 80

Figure 5. Relationship between cane fresh weight in grams (vine size) and the dry

weight (g) of trunks, roots, or trunks + roots (total storage), of Chambourcin
grapevines with 1-, 3- or 6-shOOts. Bars represent the LSD value at p =0.05 . . 81

xiii

CHAPTER IV

Figure 1. Leaf area vine-1 (A), shoot-1 (B) and leaf size (C) of potted Chambourcin
grapevines with 1(Cl) or 4(0) shoots and no clusters: I shoot, 1 cluster (I) and; 4
shoots with 1(O), 2(A) 3( o)or 4(*) clusters. Bars represent the LSD at p=0.05 103

Figure 2. Shoot length vine-1 (A) and shoot-l (B) of potted Chambourcin grapevines
with 1(El) or 4(0) shoots and no clusters: I shoot, 1 cluster (I) and; 4 shoots with
1(O), 2(A) 3( 0 )Or 4(*) clusters. Bars represent the LSD at p=0.05 ....... 104

Figure 3. Leaf number vine-1 (A) and shoot-1 (B) of potted Chambourcin grapevines
with 1(0) or 4(0) shoots and no clusters: I shoot, 1 cluster (I) and; 4 shoots with
1(O), 2(A) 3( 0 )Or 4(*) clusters. Bars represent the LSD at p=0.05 ...... 105

Figure 4. Dry weight (g) Of leaves (A), shoots (B) and fruit (C) of Chambourcin
grapevines with 1(8) or 4(0) shoots and no clusters: I shoot, 1 cluster (I) and; 4
shoots with 1(O), 2(A) 3( 0 )Or 4(*) clusters. Bars represent the LSD at p=0.05 106

Figure 5. Dry weight (g) of roots (A) and trunks (B) of Chambourcin grapevines
with 1(El) or 4(0) shoots and no clusters: I shoot, 1 cluster (I) and; 4 shoots with
1(O), 2(A) 3( O )or 4(*) clusters. Bars represent the LSD at p=0.05 ....... 107

Figure 6. Dry weight (g) of canopies (A); trunks + roots (B); and whole vines (C)
of Chambourcin grapevines with 1(El) or 4(0) shoots and no clusters: I shoot, 1
cluster (I) and; 4 shoots with 1(O), 2(A) 3( 0 )Or 4(*) clusters. Bars represent the
LSD at p=0.05. Inset in C shows the relationship between vine dry weight at harvest
and berry number ...................................... 108

Figure 7. Relationship between vine dry weight and leaf area Of potted Chambourcin
vines with 1(0) or 4(0) shoots and no clusters: I shoot, 1 cluster (I) and; 4 shoots
with 1(O) or 3(0) clusters ................................ 109

Figure 8. Mean total sugar content of fruit at harvest in potted Chambourcin

grapevines with 1 or 4 shoots and 1 cluster (1/1 and 4/1 respectively) or, 4 shoots
and 2 (4/2), 3 (4/3) or 4 (4/4) clusters. Bars represent the LSD at p=0.05 . . . . 110

xiv

°Brix
Ci
GDD
gs

8m

Pi
PPFD

SLW
SPS
SSW

LIST OF SYMBOLS, ABBREVIATIONS OR NOMENCLATURE

CO2 assimilation

Sugar content

Internal CO, concentration
Growing degree days

Leaf conductance
Mesophyll conductance
Minimally pruned vines
Inorganic phosphate

Net photosynthesis
Photosynthetic photon flux density
Relative humidity

Specific leaf weights
Sucrose-phosphate synthase
Specific shoot weigh

Leaf temperature

LITERATURE REVIEW

Grapevines are cultivated on six of the seven continents and in nearly every
country on the face of the earth. They have been grown for the production of fresh
fruit, raisins, grape seed Oil and wine from before recorded history. Many of the
cultivars used for grape and wine production today are traditional varieties which have
been propagated for centuries by vegetative cuttings. While the varieties are ancient,
the methods employed in growing them have changed rapidly during this century.
Mullins (35) states that: ”In viticulture, the main response to biological constraints or
economic change has been to manipulate the existing traditional cultivars by applying
progressively higher inputs Of husbandry. Included are innovations in standard
husbandry (rootstocks, pruning, training), in chemical-based husbandry (fertilizers,
pesticides, herbicides, growth regulators), in mechanization (mechanical harvesting
and pruning) and in postharvest technology and processing (winemaking)". The
present economic climate has caused many growers to attempt to increase profitability
by mechanizing vineyard Operations. Mechanized harvesting has been used now for
decades, but mechanical pruning has only recently met with success in some areas
(7,34,37). The primary advantage of mechanization is reduced production costs (34).
However, researchers have reported yield increases Of as much as 200% in minimally
pruned vines as compared to controls with no negative effects on fruit composition

(7 ,8, 10,37). It is thought that rapid canopy development resulting from the growth of

2
many shoots found on hedged or minimally pruned vines leads to greater, season-long

carbohydrate assimilation by the vine, effectively increasing the vine’s "capacity” over
a normally pruned vine (7,10,28,44). Capacity is defmd by Winkler (52) as "the
quantity of action with respect to total growth. The term refers to a vine’s ability for
total production rather than to rate Of activity". It is known that the total annual
carbohydrate assimilation by a plant is affected by the total exposed leaf surface
(14,46,47) and the length of time that leaf surface is exposed to the sun
(28,29,49,50). Of course, many other factors influence total carbon assimilation such
as light intensity (3,14,28,29,35), water availability (14,35), nutrition (35), leaf age
(27,36) and carbohydrate source/sink relations (6,14,17,49,50).

In the case Of grapevines, studies with minimally pruned (MP) vs. spur prumd
(spur) vines have shown clear, season-long leaf area differences (7,44). Other
researchers have shown, however, that the leaf area of spur vines equaled that Of MP
vines by mid-season and surpassed it by veraison (10). It is not clear if the greater
leaf area of the MP vines for several weeks early in the season produced a carbon
assimilation advantage over the spur vines. Nonetheless, MP vines produced fruit
yields Of approximately twice that Of controls. However, when canopy dry weights
(both vegetative and reproductive tissues) were compared, no differences were found
among treatments (10). Similar results were demonstrated when crop load was varied
in potted vines (11,12,13). Thus, the larger crop produced by the MP vines may
have resulted from greater partitioning of carbohydrates from other organs rather than

greater total carbon assimilation relative to spur vines.

CANOPY DEVELOPMENT

As stated above, the rapid canopy deployment characteristic of MP vines is
thought to increase annual carbon assimilation thereby "increasing” vine capacity
(7,28,44). Starch reserves are mobilized in the spring to support the spring growth
flush (21,35,38,53,54,55). During this period of leaf development, assimilated
carbon is utilized for building leaf and later, shoot tissues (18,54,55). The basal
leaves become net carbon exporters only after the fifth leaf has emerged from the
shoot (18,54). By the time the seventh leaf emerges, vines are nearing bloom and the
reserves are spent. At the end of the growth flush (around bloom), the new leaves
support growth (54). Because leaves become net carbohydrate exporters so late in the
growth flush, it is not clear what advantage there is in having large amounts of leaf
area during the growth flush. It is possible that greater shoot numbers (i.e. vegetative
sink strength) more efficiently utilize stored carbohydrates during the growth flush as
compared to severely pruned vines thereby taking full advantage of a vine’s ability to
generate a canopy. This, however, has not been demonstrated.

Empirical data suggest that vines compensate for a small number of shoots
relative to the size of the reserve pool by causing the few shoots to grow faster.
Koblet and Perret (25) reported that Muller-Thurgau vines with a greater volume of
perennial wood had more fruitful shoots and higher yields than did control vines. The
increase in shoot fruitfulness was due to a slight increase in berry weight and berries
per cluster which in turn lead to significant yield increases with no negative effect on
fruit composition. These findings are supported by Howell et al. (20) where the

volume of perennial wood varied greatly with vine training system. These studies

4
maintained a similar vegetative sink strength (or shoot number) while varying the size

of the carbohydrate source during the spring growth flush. Although leaf area was
not determined, the increases in berry and cluster weight and the slight increase in
berry number per cluster at similar fruit soluble solids suggests that more leaf area
was available both at bloom and at harvest on vines with greater carbohydrate
reserves. Greater leaf area at bloom has been shown to improve fnrit set (4) and it
may have been responsible for the higher berry mrmber per cluster reported (20).

The production of greater fruit yields with no effect on fruit composition suggests that
there may have been additional leaf area available from veraison through harvest to
support fruit maturation on the higher yielding vines. In support of these hypotheses,
Koblet et al. (26) demonstrated a positive relationship between trunk volume and total
leaf area, lateral leaf area, yield per vine, shoot fruitfulness, cluster weight, berries
per cluster, must soluble solids and must pH. By increasing source size (trunk
volume) at constant sink strength (shoot number) during the growth flush, greater leaf
area was made available for the developing clusters. The precise mechanism by
which this occurred is not clear, but it has been suggested that individual shoots grow
at a faster rate (and apparently generate more leaf area per cluster) when shoot
numbers are reduced relative to source size (40,41,42).

By contrast, other researchers have varied vegetative sink strength while
maintaining a relatively constant source size during the growth flush
(7,8,10,33,43,44). This approach demonstrated that as vegetative sink (shoot and
leaf) number increased, shoot fruitfulness and fruit soluble solids decreased

(7,8,33,44). The decrease in shoot fruitfulness was due to fewer berries per cluster,

5
reduced berry weight and fewer clusters per node (7,33). These data indicate that

leaf area was limiting at bloom (evident in the reduced fruit set) and again from
veraison through harvest as fruit matured as shown by the reduction in fruit soluble
solids with increasing bud numbers and crop load. When leaf area was determined on
lightly pruned vines, it was found that they had greater leaf area overall than did
controls (44). However, individual shoots were shorter with smaller leaves and there
was an inverse relationship between the number of buds retained at pruning and the
number of buds producing shoots. Clingeleffer suggests that this is a means by which
vines "self regulate” the amount of crop produced (7). It is known that as crop load
increases, shoot length decreases (11,12). It appears that the presence of many shoots
also causes a reduction in shoot length relative to severely pruned vines (7,8,10).
Shoot length may be less in MP vines relative to severely pruned controls even before
bloom suggesting that the large numbers Of shoots are competing for limited resources
(e. g. carbohydrate reserves, water, nutrients and root-produced growth regulators).
The relative effects of crop load and competition among shoots on the length of
individual shoots over the course of the growing season are difficult to separate.
Thus, the relative influence that increasing crop load or increasing shoot numbers
have on shoot length, either separately or combined, remains unclear.

FRUITFULNESS

The fruitfulness of a shoot might be influenced by the carbohydrate
source/ sink relationships during shoot development as discussed above. This
apparently occurs even though buds Of similar developmental morphology were used.

It seems important to make a distinction between "bud" and "shoot” fruitfulness. Bud

6

fruitfulness refers to the development of flower cluster primordia within a dormant
bud (35.40.51). Shoot fruitfulness, by contrast, is the actual quantity of fruit
produced on a shoot. It integrates environmental and vine growth variables in the
current growing season while bud fruitfulness is a reflection of environmental and
vine growth variables from the previous growing season. It has been shown that both
bud (32,40,51) and shoot (7,33,39,44) fruitfulness can be influenced by carbohydrate
availability. Given the strong fruit sinks on MP vines, carbohydrates may be limited
for bud development since the developing bud is a relatively weak sink (32,49,50).
However, it has also been shown that increasing the number of buds on a vine can
cause a reduction in shoot fruitfulness (7,8,10,33,44). Thus, it is not clear if the
reduction in fruitfulness Observed in MP vines is due to poorer bud development
relative to controls, increased carbohydrate competition during fruit set, or some
combination of the two.

CARBOHYDRATE RELATIONS

The greater crop carried by MP vines represents a strong carbohydrate sink
(49,50). The strength of a sink is defined as the sink size multiplied by its activity
(29,48,49,50). It follows that doubling the size Of the fruiting sink would double its
strength if there is no change in metabolic activity. Chandler and Heinecke (6)
demonstrated as early as 1926 that a strong fruiting sink in apple caused trees to
produce a greater quantity of dry matter over a growing season as compared to a
lightly cropped tree. Leaf photosynthesis can respond to increased sink demand by
increasing the rate of CO2 assimilation (4,14,17,29,49,50). This is known as

photosynthetic compensation and is an important mechanism by which a plant

7
maintains growth after losing foliage to disease or insects, or responds to increased

carbohydrate demand such as occurs with high crop loads (4,30,31). As the leaf area
ratio (LAR) is reduced, or sink strength increased, Pn per unit leaf area increases up
to a maximum which is delimited by the rate of Rubisco (ribulose-l ,5-bisphosphate
carboxylase-oxygenase) regeneration (4,50). Photosynthetic compensation may reduce
the expected differences in dry matter production caused by varying canopy size. For
example, CandOlfi-Vasconcelos (4) demonstrated that removing leaves from
grapevines (effectively reducing the LAR) caused an increase in the rate of C02
assimilation per unit leaf area in the remaining leaves. It has been suggested that this
phenomenon may be due to an increase in the quantity of water and root-supplied
compounds available to the remaining leaves via the transpiration stream since the
size Of the root system remains unchanged (14). Severely pruned vines have a
reduced LAR relative to MP vines for the early part of the growing season (10). This
might lead to an increase in CO2 assimilation per unit leaf area as a result Of
photosynthetic compensation. However, field vines did not show an increase in Pn
per unit leaf area Of spur pruned vines early in the season as suggested. Rather, MP
vines had higher average rates of Pn per unit leaf area (10). Spur pruned vines in
that study never had higher average rates of Pn than MP vines. The results are
confounded though due to the fact that MP vines also had a much stronger fruiting
sink than did controls.

More recently, attention has focused on the control of photosynthetic carbon
fixation since it is the first step in dry matter production in higher plants. What has

emerged is the hypothesis that photosynthetic carbon fixation is controlled by end-

8
product inhibition of two important enzymes: fructose 1,6 phosphatase and sucrose-

phosphate synthase (SPS) (16,47). As cytosolic sucrose levels rise due to low rates of
sucrose utilization at sinks, sucrose production slows and the levels of hexose
phosphates increase (45,46,47). This causes an increase in fructose 2,6 bisphosphate
(47). As fructose 2,6 bisphosphate increases, synthesis of fructose 1,6 bisphosphate
from triose phosphates is inhibited. Fructose 1,6 bisphosphate is the first six-carbon
sugar formed from photosynthetically fixed carbon so it is an efficient control point
from which carbon can be partitioned into sugar or starch production. When
synthesis of hexose phosphates is inhibited, triose-phosphate concentrations in the
cytosol increase. Triose-phosphate movement into the cytosol from the chloroplast is
dependent upon a strict counter-exchange with inorganic phosphate (Pi) catalyzed by
the phosphate translocator (47). When hexose synthesis slows, Pi remains bound to
triose-phosphates and is unavailable for exchange with the chloroplast. Under this
condition, the triose-phosphates accumulating in the chloroplast are diverted to starch
production (16,47).

The control of sucrose production by SP5 is also critical to cytosolic carbon
partitioning (19). High rates of sucrose synthesis reduce the hexose pool and slow
starch accumulation. Control Of SP8 is complex. It is influenced by light, increasing
hexose-phosphates and decreasing inorganic phosphate (for a recent review, see Huber
and Huber (19)). SP8 is the final enzyme in the sucrose synthesis pathway and is
therefore an important control point for the partitioning of carbon to sucrose for

export to carbohydrate sinks.

9
If conditions exist in the whole plant which lead to continuing high levels of

cytosolic hexose and starch in the chloroplast (such as a high ratio of carbohydrate
sources to carbohydrate sinks), there may be a reduction in the rate of
photosynthetically fixed carbon by Rubisco (15,16,3l,46). By contrast, if sucrose
utilization rates are high, the rate of sucrose synthesis rises to meet the demand. The
rates of Rubisco regeneration and possibly sucrose transport are thought to limit the
absolute rate of photosynthesis and plant growth. However, the ultimate controls
regulating expression of the genes coding for photosynthetic proteins have yet to be
fully deduced (for a recent review see Stitt and Quick (47)). Inhibition of sucrose
synthesis due to low utilization rates by carbohydrate sinks is a condition where
photosynthetic carbohydrate production is "sink limited" (14,49,50). When sink
demand is greater than the available sugars supplied via photosynthesis, dry matter
production is ”source limited” (14,31,49,50). Prunus cerasus trees which were
partially defoliated increased net CO, assimilation (A) and decreased leaf starch
concentration within 24 hours (30,31). Exposure to continuous light caused a
decrease in A within 24 hours. Chandler and Heinecke (6) and Edson (11)
demonstrated higher rates of dry matter production per plant or per unit leaf area
respectively when sink strength increased relative to source size. These facts lead one
to the deduction that by increasing the crop on MP vines, it is possible to cause
higher rates of Pn in leaves due to the greater sink demand represented by the
developing fruits.

Source/ sink relationships are complex and change as the growing season

progresses (4,14,21,49,50). During the spring growth flush, shoot tips and expanding

10
leaves are the primary carbohydrate sink and starch reserves are the primary source

(18,53,54,55). By bloom, starch reserves are depleted and fully developed leaves
become the primary carbohydrate source (18,54). While shoot tips and leaves are
strong sinks during the growth flush, flower clusters become relatively strong sinks
during bloom (1,2,22). After anthesis, fruit becomes an active sink as berries grow
(11,13,14,35,49,50). Vegetative sinks are active between anthesis and veraison as
well. During fruit ripening, berries are a very active sink but this is also a very
important period for building the reserves which will support growth the following
spring (55). The actual strength Of the fruit sink, as mentioned above, is dependent
on the number of berries present. Several researchers have determined that a
minimumof10cm2Ofexposedleafareaarerequiredtomamreonegramoffruit
(23,24,27,52). ' This is the relationship which must exist at harvest. If the leaf area
per gram of fruit drops below this value because of overcropping or loss of leaf area
to biotic or abiotic factors, insufficient carbohydrates are produced to either mature
fruit for commercial use or rebuild reserves. In this case, both the current season’s
crop and the subsequent season’s vine capacity will suffer. Between harvest and leaf
fall, root tissues are the most active carbohydrate sink (35,52) so a period Of active
photosynthesis between harvest and leaf fall is beneficial to the building of starch
reserves and vine capacity for the following season.

The timing of sink activity in grapevines and the effects of varying the relative
strength of sinks have been demonstrated in several studies (11,35,52). When potted
grapevines were grown with varying crop loads, the total quantity of dry matter

produced by vines was not different among treatments ranging from one to six

11
clusters (11). However, the partitioning Of carbohydrate was altered so that less was

allocated to vegetative sinks and more was partitioned to fruit. In general, there is an
inverse relationship between crop load and leaf size (11), leaf area and shoot length
(11,12) resulting from preferential partitioning of carbohydrate to fruit. Given these
data, it is apparent that some of the carbohydrates used to produce crap in MP vines
is derived from greater allocation Of carbohydrate to fnrit at the expense of vegetative
organs. The higher crop loads of MP vines may cause higher rates of photosynthesis
’ and therefore dry matter production because of the strength of the fruiting sink. High
sink activity has been shown to increase the rate of A per unit leaf area
(11,12,14,l7,30,31), so it is possible that the greater sink activity present on MP
vines is actually in closer ”balance" with the vine’s capacity, thereby causing the
leaves to be more efficient at carbohydrate production. In summary, the higher
productivity of MP vines likely results from the interplay Of several factors rather
than being caused solely by higher photosynthetic rates.

MINIMALLY PRUNED VINES

Minimally pruned vines have produced large crops in both warm (7,8) and
cool (37) climates. Results are in conflict, however, regarding the estimate of whole-
canopy photosynthesis over the course of the growing season (7,10). It is not clear if
MP vines actually assimilate more carbon over the growing season or if they even
need to produce more dry matter in order to produce larger crops. Large
morphological changes occur in the vegetative structures of MP vines compared to
spur pruned vines (7,8, 10,44) including shorter shoots, smaller leaves and a reduction

in shoot fruitfulness. It has also been shown that MP vines produce a smaller

12
quantity of lignified, one-year-old wood than a spur pruned vine at a similar vine

capacity (7,10). Altered shoot morphology has been observed in MP vines even
though the shoot fruitfulness is reduced (7), indicating that factors other than
fruitfulness are involved. Thus, the relative influences of crop load and vine "self
regulation" are not clear regarding their effects on bud and shoot fruitfulness, shoot
length and leaf size. Similarly, the relative influences of filling the canopy early and
increasing the strength of the reproductive sink(s) on whole-season carbohydrate
assimilation remain to be resolved. Finally, the amount of carbohydrate either
selectively partitiomd to fruit during normal growth, or remobilized from other vine
organs for fruit maturation with increasing crop load are not known.

To summarize, a number of morphological and physiological changes
accompany light pruning of grapevines as compared to severely prumd controls. The
relative strengths of the greater numbers of vegetative and fnriting sinks in MP vines
and their influence on vine physiology and morphology are not known. The purpose
of this research was to broaden our understanding of these factors.

There are several working hypotheses to be tested: (1) greater shoot numbers
present during the spring growth flush more completely utilize stored reserves thereby
allowing a vine to maximize its capacity for dry matter production; (2) competition
among shoots for carbohydrates, water, nutrients and growth regulators during both
the spring growth flush and the remainder of the growing season has a large effect on
shoot, leaf and cluster morphology; (3) there is a positive relationship between shoot
number, early-season leaf area and whole vine C02 assimilation/ seasonal dry matter

production; (4) the source of carbohydrates used for the production of fruit as crop

13
load increases is due largely to a preferential partitioning to fruit at the expense of

vegetative organs; and (5) the stronger fruiting sink on MP vines causes more dry
matter assimilation per unit exposed leaf area.

Four chapters describe the experiments conducted to test the above hypotheses.
The first chapter describes a whole plant photosynthesis chamber which was
developed to measure the rate of CO, exchange of whole grapevines when grown with
varying numbers of vegetative and reproductive sinks. The second chapter focuses on
the rate of canopy development, canOpy morphology and whole vine carbon exchange
when increasing numbers of shoots are retained. The third chapter examines the rate
of starch utilization during the growth flush, dry matter partitioning during the
growing season and the rate of dry matter production during the growing season when
vines are allowed to develop leaf area more rapidly in the spring. This experiment is
designed to test the hypothesis that by simply having more leaf area, vines will
accumulate more dry matter. The fourth chapter is an experiment in which both leaf
area and fruit-sink strength are varied to determine (a) the contribution of greater leaf
area; and (b) the contribution of greater sink strength, in affecting seasonal dry matter
production. This experiment is also designed to determine the source of carbohydrate

used to produce fruit as crop load increases.

l4

LITERATURE CITED

1. Blanke, M.M. Carbon economy of the grape inflorescence. 5. Energy
requirement of the flower bud of grape. Wein-Wiss. 45:33-5 (1990).

2. Blanke, M.M. and A. Leyhe. Carbon economy of the grape inflorescence. 1.
Carbon economy in flower buds of grape. Wein-Wiss. 44:33-6 (1989).

3. Buttrose, M.S. Some effects of light intensity and temperature on dry weight
and shoot growth of grapevines. Ann. Bot. 32:753-65 (1968).

4. Candolfi-Vasconcelos, MC. and W. Koblet. Yield, fruit quality, bud fertility,
and starch reserves of the wood as a function of leaf removal in m m -
Evidence of compensation and stress recovering. Vitis 29: 199-221 (1990).

5. Candolfi-Vasconcelos, M. C. and W. Koblet. Influence of partial defoliation
on gas exchange parameters and chlorophyll content of field-grown grapevines -
Mechanisms and limitations of the compensation capacity. Vitis 30:129-41 (1991).

6. Chandler, W.H. and AJ. Heinicke. The effect of fruiting on the growth of
Oldenberg apple trees. Proc. Am. Soc. Hort. Sci. 23:36-46 (1926).

7. Clingeleffer, P.R. Vine response to modified pruning practices. In:
Proceedings of the Second NJ. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 20—30. Cornell University Press, Geneva (1993).

8. Clingeleffer, P.R. and LR. Krake. Responses of Cabernet Franc grapevines
to minimal pruning and virus infection. Am. J. Enol. Vitic. 43:31-7 (1992).

9. Downton, W.J.S., W.J.R. Grant and B.R. Loveys. Diurnal changes in the
photosynthesis of field-grown grapevines. New Phytol. 105:71-80 (1987).

10. Downton, W.J.S. and W.J.R. Grant. Photosynthetic physiology of spur
pruned and minimal pruned grapevines. Aust. J. Plant Physiol. 19:309-16 (1992).

11. Edson, C.E. Influence of crop level on single leaf and whole vine
photosynthesis and dry matter partitioning in Seyval grapevines (Vitis sp.). Doctoral
dissertation, Michigan State University, East Lansing, MI. p 169 (1991).

15

12. Eibach, R. and G. Alleweldt. Einfluss der wasserversorgung auf wachstum,
gaswechsel und substanzproduktion traubentragender Reben. I. Das vegetative
wachstum. Vitis 22:231-40 (1983).

13. Eibach, R. and G. Alleweldt. Einfluss der wasserversorgung auf wachstum,
gaswechsel und substanzproduktion traubentragender Reben. 111. Die
substansproduktion. Vitis 24:183-98 (1985).

14. Flore, J .A. and AN. Lakso. Environmental and physiological regulation of
photosynthesis in fruit crops. Horticultural Reviews 11:111-46 (1989).

15. Flore, J.A. Stone Fruit. In: Handbook of Environmental Physiology of Fruit
Crops. I. Temperate Crops. B. Schaffer and RC. Andersen (Eds), pp 233-70. CRC
Press, Boca Raton, FL (1994).

16. Goldschmidt, BE. and SC. Huber. Regulation of photosynthesis by
end-product accumulation in leaves of plants storing starch, sucrose, and hexose
sugars. Plant Physiol. 99:1443-8 (1992).

17. Gucci, R., C. Xiloyannis, and J.A. Flore. Gas exchange parameters, water
relations and carbohydrate partitioning in leaves of field-grown Prunus domestica
following fruit removal. Physiol. Plant. 83:497-505 (1991).

18. Hale, CR. and R]. Weaver. The effect of developmental stage on the
direction of translocation of photosynthate in Vitis vimfera. Hilgardia 33:89-131
(1962).

19. Huber, SC. and J. L. Huber. Role of sucrose-phosphate synthase in sucrose
metabolism in leaves. Plant Physiol. 99:1275-8 (1992).

20. Howell, G.S., D.P. Miller, C.E. Edson and R.K. Striegler. Influence of
training system and pruning severity on yield, vine size and fruit composition of
Vignoles grapevines. Am. J. Enol. Vitic. 42:191-8 (1991).

21. Keller, JD. and W.H. Loescher. Nonstructural carbohydrate partitioning in
perennial parts of sweet cherry. J. Am. Soc. Hort. Sci. 144:969-75 (1989).

22. Keller, M. and W. Koblet. Is carbon starvation rather than excessive nitrogen
supply the cause of inflorescence necrosis in Vitis vinrfera L.? Vitis 33:81-6 (1994).

23. Kliewer, W.M. and AJ. Antcliff. Influence of defoliation, leaf darkening and
cluster shading on the growth and composition of Sultana grapes. Am. J. Enol. Vitic.
21:26-36 (1970).

16

24. Kliewer, W.M. Effect of time and severity of defoliation on growth and
composition of Thompson Seedless grapes. Am. J. Enrol. Vitic. 21:37-47 (1970).

25. Koblet, W. and P. Perret. The role of old wood on yield and qualtiy of
grapes. In: Proc. Univ. of California, Davis Grape and Wine Centennial Symposium.
A.D. Webb (Ed), pp 164-8. University of California Press, Berkley (1990).

26. Koblet. W., M.C. Candolfi-Vasconcelos, W. Zweifel, and 6.8. Howell.
Influence of leaf removal, rootstock, and training system on yield and fruit
composition of Pinot Noir grapevines. Am. J. Enol. Vitic. 45:181-7 (1994).

27. Kreideman, P.E., W.M. Kliewer, and I.M. Harris. Leaf age and
photosynthesis in Vitis vinifera. Vitis 7 :213-20 (1970).

28. Lakso, A.N. Viticultural and physiological parameters limiting yield. In:
Proceedings of the Second N .J. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 9-14. Cornell University Press, Geneva (1993).

29. Lakso, A.N . Apple. In: Handbook of Environmental Physiology of Fruit
Crops. I. Temperate Crops. B. Schaffer and P.C. Andersen (Eds), pp 3-42. CRC
Press, Boca Raton, FL (1994).

30. Layne, D.L. Physiological responses of Prunus cerasus to whole plant source
manipulation. Ph.D. dissertation, Michigan State University, East Lansing. p 189
(1992).

31. Layne, DR. and J.A. Flore. End-product inhibition of photosynthesis in
Prunus cerasus L. in response to whole-plant source-sink manipulation. J . Amer.
Soc. Hort. Sci. 120:583-99 (1995).

32. May, P., N .J . Shaulis, and AJ. Antcliff. The effect of controlled defoliation
in the Sultana vine. Am. J. Enol. Vitic. 20:237-50 (1969).

33. Miller, D.P., G.S. Howell, and R.K. Striegler. Reproductive and vegetative
response of mature grapevines subjected to differential cropping stresses. Am. J.
Enol. Vitic. 44:435-40 (1993).

34. Mitchell, T.G. Vineyard mechanization and its impact on production costs in
the Taylor Wine Company vineyards. In: Proceedings of the Second NJ. Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), pp 66-8. Cornell
University Press, Geneva (1993).

35. Mullins, M.G., A. Bouquet and LE. Williams. Biology of the grapevine.
Cambridge University Press, Cambridge. 239 pp. (1992).

17

36. Poni, S., C. Intrieri, and O. Silvestroni. Interactions of Leaf age, fruiting,
and exogenous cytokinins in Sangiovese grapevines under non-irrigated conditions. H
Chlorophyll and nitrogen content. Am. J. Enol. Vitic. 45:278-84 (1994).

37. Pool, R.M., R.E. Dunst, D.C. Crowe, H. Hubbard, G.E. Howard, and G.
Degolier. Predicting and controlling. crop on machine or minimal pruned grapevines.
In: Procwdings of the Second N.J. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 31-45. Cornell University Press, Geneva (1993).

38. Quinlan, J.D. Mobilization of 1‘C in the spring following autumn assimilation
of 1‘CO, by an apple rootstock. J. Hort. Sci. 44:107-10 (1969).

39. Reynolds, A.G., R.M. Pool and LR. Mattick. Effect of shoot density and
crop control on growth, yield, fruit composition and wine quality of ’Seyval blanc’
grapevines. J. Amer. Soc. Hort. Sci. 111:55-63 (1986).

40. Shaulis, NJ. and RE. Smart. Grapevine canopies: management,
microclimate and yield responses. 20th International Horticultural Congress,
Warzawa. pp. 255-65 (1974).

41. Smart, R.E. Climate, canopy microclimate, vine physiology and wine quality.
In: Proceedings of the International Symposium on Cool Climate Viticulture and
Enology. D.A. Heatherbell, P.B. Lombard, F.W. Bodyfelt and SF. Price (Eds), pp
1-18. Oregon State University Experiment Station Technical Publication No. 7628
(1985).

42. Smart, R.E. Principles of grapevine canopy microclimate manipulation with
implications for yield and quality. A review. Am. I. Enol. Vitic. 36:230-9 (1985).

43. Smithyman, R.P. Canopy and cropping influence on vine growth, physiology,
and cluster disease incidence of Seyval and Vignoles grapevines. MS Thesis,
Michigan State University. p 165 (1994).

44. Sommer, KI. and P.R. Clingeleffer. Comparison of leaf area development,
leaf physiology, berry maturation, juice quality, and fruit yield of minimal and cane
pruned Cabernet Sauvignon grapevines. In: Proceedings of the Second NJ. Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), pp 149. Cornell
University Press, Geneva (1993).

45. Stitt, M. , B. Kurzel, and H.W. Heldt. Control of photosynthetic sucrose
synthesis by fructose 2,6-bisphosphate. Plant Physiol. 75:554-60 (1984).

46. Stitt, M., H. Grosse, and K. Woo. Interactions between sucrose synthesis and
C02 fixation II. Alterations of fructose 2,6-bisphosphate during phosynthetic
oscillations. J. Plant Physiol. 133:138-43 (1988).

18

47. Stitt, M. and W.P. Quick. Photosynthetic carbon partitioning: its regulation
and possibilities for manipulation. Physiol. Plant. 77:633-41 (1989).

48. Sung. S.S., W.J. Sheih, D.R. Geiger and QC. Black. Growth, sucrose
synthase, and invertase activities of developing Phaseolus vulgaris L. fruits. Plant,
Cell and Environ. 17:419-26 (1994).

49. Wardlaw, I.F. The Control of carbon partitioning in plants. Tansley
Review No. 27, pp 341-381 (1990).

50. Wareing, RF. and J. Patrick. Source-sink relations and the partition of
assimilates in the plant. In: Photosynthesis and Productivity in Different
Environments. J.P. Cooper (Ed), pp 481499. Cambridge University Press,
Cambridge, UK (1975).

51. Winkler, A.J. Pruning and thinning experiments with grapevines. California
Agr. Exp. Sta. Bull, 519:1-56 (1931).

52. Winkler, A.J., J.A. Cook, W.M. Kliewer and LA. Lider. General
viticulture. University of California Press, Berkley, CA. 710 pp. (1974).

53. Yang, Y.S. and Y. Hori. Studies on the retranslocation of accumulated
assimilates in ’Delaware’ grapevines. I. Retranslocation of 1‘C assimilates in the
following spring after l‘C feeding in summer and autumn. Tohoku J. Agric. Res.
30:43-56 (1979).

54. Yang, Y.S. and Y. Hori. Studies on the retranslocation of accumulated
assimilates in ’Delaware’ grapevines. III. Early growth of new shoots as dependent
on accumulated and current year reserves. Tohoku J. Agric. Res. 31:120-9 (1980).

55. Yang, Y., Y. Hori and R. Ogata. Studies of retranslocation of accumulated
assimilates in ’Delaware’ grapevines. II. Retranslocation of assimilates accumulated
during the previous growing season. Tohoku J. Agric. Res. 31:109-19 (1980).

19
I. AN INEXPENSIVE, WHOLE PLANT, OPEN GAS EXCHANGE

SYSTEM FOR THE MEASUREMENT OF Pn IN POTTED WOODY

PLANTS

ABSTRACT

The measurement of whole plant CO, exchange integrates leaf to leaf
variability which arises from sources such as angle of incident radiation, source/ sink
relationships, age and biotic or abiotic factors, and respiration of above ground
vegetative and reproductive sinks into the final determination of whole plant CO,
assimilation. While estimates of whole plant C02 uptake based on single leaf
determinations have been used, they do not accurately reflect actual whole plant
assimilation. Chambers were constructed to measure gas exchange of entire potted
grapevines. The design and construction are simple, inexpensive and easy to use,
allowing for the measurement of many plants in a relatively short period of time.
This enables the researcher to make replicated comparisons of the whole plant C02
assimilation of various treatments throughout the growing season. . While CO,
measurement was the focus of this project, it is also possible to measure whole plant
transpiration with this system.

INTRODUCTION

Measurement of leaf gas exchange is an important technique used to estimate
photosynthesis. However, individual leaf photosynthetic determinations have
limitations when used to estimate whole plant CO, exchange. Leaf Pn can be highly
variable due to differences in leaf age (Poni et al. , 1994a), chlorophyll content
(Candolfi-Vasconcellos and Koblet. 1991; Flore and Lakso, 1989; Poni et al. 1994b),

angle of incident radiation (Flore and Lakso, 1989), leaf shading (Flore, 1994) leaf

20
age (Poni et al. , 1994a), respiration of leaves, perennial structures and fruit (Corelli-

Grappadelli and Manganini, 1993) or due to biotic Or abiotic stress. In addition,
variability may result from differences within and between plants due to crop load,
the proximity of carbohydrate sinks and other source/sink relationships (Edson, 1991;
Flore, 1994; Gucci et al., 1991). Consequently, individual leaf measurements
indicate the relative carbon uptake per unit leaf area, but they are problematic when
used to extrapolate whole plant assimilation.

An accurate assessment of the total, net carbon uptake of whole plants is
essential if production per unit land area is to be maximized. One approach is to
place the entire plant in a whole plant gas exchange system. This integrates all
factors which influence Pn as well as respiration of the various plant parts (Corelli-
Grappadelli, 1993; Katerji et al., 1994). Heinecke and Childers (1937) first devised a
system for a whole apple tree in 1935. Since then, modern materials and portable gas
analysis equipment have allowed for construction of chambers which are easier to use
(Long and Hallgren, 1985). The expense, power requirements and the mcessity for
cooling have been limitations of these systems. Recently, the performance of
polyethylene chambers used continuously in the field on apple trees (Corelli-
Grappadelli, 1993) and grapevines (Katerji et al., 1994) was reported. These
chambers have the advantage of being inexpensive, easy to build, and they do not
require cooling because they do not trap significant quantities of infra-red radiation,
and the high flow rates used insure rapid exchange of air within the chamber.
Additionally, polyethylene blocks very little of the incident radiation in the

photosynthetically active range aloowing full sun to provide saturating light

21

conditions. The authors were able to monitor whole plant photosynthesis for extended
periods. The chambers described here are not easily moved from plant to plant so the
number of treatments or replicates which could be monitored was limited, but the
results suggest the utility of this approach.

The goal of this project was to design, build and test an open, gas exchange
system for whole, potted plants. I wanted the following attributes: (1) low cost; (2)
easily constructed from off-the-shelf items; (3) low volume relative to plant size so
high flow rates could be used; (4) no need for cooling; (5) rapid equilibration for
higher throughput of plant materials; and (6) easily assembled and disassembled
making it somewhat portable. I also wanted chamber conditions to be near ambient
so leaf temperature and gas environment would not affect photosynthetic processes.
To maximize the number of plants which could be measured in a given interval, two
chambers were employed: one in which a plant could equilibrate while the other was
being measured.

Work by other researchers (Corelli-Grappadelli, 1993; Alan Lakso, personal
communication) suggested that the easiest and least expensive approach to achieve
these goals was to construct open system chambers that were essentially "balloons"
made of Mylar. Such chambers operate under a slight positive pressure, thus no
other means of support is generally necessary and any small leaks in the system flow
out of the chamber so there is no affect on ACO, readings. A benefit of an open

system is that small chamber leaks are acceptable.

22
MATERIALS AND METHODS

Chamber Construction

Building materials available at a local hardware store, with the exception of
the Mylar" film were used in system construction. The plant chambers were
constructed around a wood base (Figure. 1) 43.0 cm in length and 39.5 cm in width.
This was cut in an obovate shape from 1.6 cm thick plywood. Holes were cut to
accommodate the plant stem (in this case a grapevine) [3.8 cm dia.] and the air inlet
pipe [5.7 cm dia.]. The base was then cut in half through the trunk opening so it
could be moved on and off of vines (Figure 1b). To hold the halves together during
operation, two chest-latches were used, one on each side of the vine opening.
Wooden ”biscuits" were inserted into the faces of the two halves of the base to aid in
alignment during assembly and to insure that the base would not fold when the latches
were secured. A sleeve of non-porous foam, the type used to insulate hot water
pipes, was placed around the vine trunk. This was slightly larger in diameter than the
opening for the vine trunk which enabled the chamber base to compress the sleeve
and form a relatively tight seal around the trunk. This design separated the vine from
the potting soil to eliminate the effects of soil and root respiration on CO2
determinations.

The actual chambers consisted of Mylar M-3O film (polyethylene terephthalate,
polyvinylidene chloride coated, DuPont Inc. , Wilmington, DE) which had been rolled
into a cylinder of a diameter slightly larger than that of the wood bases to facilitate
assembly of the base/chamber system. This cylinder was sealed with clear box tape

along the seam. An outlet port of 5.1 cm i.d. PVC pipe was attached using tape and

23
rubber bands to draw the distal end of the chamber together forming a roughly

hemispherical top above a cylindrical chamber. The chambers were attached to the
base using an elastic band fitted into a groove cut around the periphery of the base
(Figure lb inset). The bands used here was the type used to attach garbage bags to
30 gallon garbage containers.

Mylar’s light transmition and gas permeation qualities are excellent. Light
transmission in the photosynthetically active range of radiation was about 90%
(similar to polyethylene) (R. Richmond, DuPont Inc. , Wilmington, DE, personal
communication), and permeability to C02, H20 and 02 is quite low relative to other
films (Pauly, 1989). In addition, the high flow rates used here reduced gaseous losses
or gains which might occur through the film thereby reducing variation arising from
this source. However, light quality and quantity may be influenced by any
commercially available film, and this should be considered when interpreting data
collected with a film between the light source and leaves.

The air supply system consisted Of a small, squirrel-cage fan of the type used
for forced-air heating systems with a maximum, unrestricted output of 4530 l min"
(Model #IC982B, Dayton lnc., Dayton, OH). This was attached to a 10.2 cm i.d.
PVC pipe ”T" which served as a manifold to distribute the air to the two chambers.
After the flow was divided by the manifold, air flowed through two, 1.2m lengths of
10.2 cm i.d. PVC pipe. This section of the air supply system was kept at 10.2 cm
i.d. because it was necessary to have piping of this diameter or larger in order to
accurately measure air flow using a hot-wire anemometer. The air supply pipe

diameter was reduced to 5.1cm before the inlet into the chambers. Using a smaller

24
inlet pipe reduced the diameter of the chamber base and helped keep chamber volume

low. Air flow was regulated using a 120 V, 10 A rheostat to control fan speed.
Air flow and temperature measurement were accomplished using a thermal
anemometer (Cole-Farmer Model #37000-00, Cole-Parmer Inc. , Chicago, IL). Air
flow was measured midway on the inlet pipe by taking 8 readings of equal cross-
sectional area and then averaging these (Dr. R. Beaudry, personal communication).

Volume of air was calculated from linear flow data by the equation:

2
V= III 1
1000

Where: V = volume of air in liters sec'l
r= the inside radius of the air supply line in cm
l=the linear flow rate of air in cm sec'1
Once the volume of air flow was calculated, it was corrected using the
chamber calibration curve described below. Laminar flow from the chamber inlet to
its outlet was prevented by placing an air diffuser over the chamber inlet. The
diffuser, a piece of tape, created turbulence in the air stream thereby insuring that
chamber air was completely mixed. This was later verified by introducing smoke to
visualize flow into a chamber containing a vine.
Chamber influence on leaf temperature was determimd by comparing a leaf on
a vine inside a chamber with a leaf on a vine outside of the chamber simultaneously
over a range of air flow rates. This was accomplished by inserting a copper-

constantan ”needle” thermocouple probe into a leaf on each vine. leaf temperatures

were determined using an Omega model I-IH23 handheld microprocessor

25
thermometer. Temperature data (not shown) indicated that leaf temperatures inside

the chamber were 1 to 2°C higher when air flow rates were similar to those used for
determination of A. At very low flow rates, leaf temperature increased inside the
chamber 5 to 6°C above that of vine leaves under ambient conditions, indicating the
need to use the highest flow rates that will still allow accurate determination of ACO,
(ACO, readings in the 15 to 35 ppm range).

Measurement of ACO, was accomplished using an ADC LCA-2 portable
infrared gas analyzer (IRGA) (Analytical Development Co. , Hoddesdon, U.K.). A
reference sample was obtaimd from one of the inlet pipes in the same region that the
air flow was measured. The sample CO, measurement was then taken at the chamber
outlet. ACO, concentrations were determined only after vines had equilibrated in the
chambers for about 5 minutes after which the IRGA readings had stabilized.

Whole vine CO, assimilation (umol vine" see") was calculated as follows:

(AC02)p.l .Z’1 x (flow)l min'1

A(umol vine‘1 sec‘l) = .
29 .2511 umol'1 x 6OSeC ruin"1

 

Where: AC02 = [C0,],, - [C0,]out

"Flow” was calculated from anemometer readings. The value of 29.2 #1
[1111014 to convert CO, volume to CO, concentration was calculated at standard
temperature (20°C). At the higher temperatures often encountered in the chambers
(26 - 36°C), 292“] was less than lumol. However, the change in CO, concentration

only introduced about a 0.5 % error over the range of temperatures listed above.

26
Chamber Calibration

Air flow in the inlet pipe was more turbulent than expected in the area of air
flow measurement due to the reduction of inlet pipe diameter at the chamber. This
required verification of flow readings from the thermal anemometer which was
accomplished by calculating air flow into an empty chamber by measuring the dilution
of a stream of C0, of known concentration and flow rate. The values obtained over a
range of flow rates were then regressed on values obtained using the thermal
anemometer at the same flow rates. The regression equation (Y = .51x -0.10.
r2=0.99) was used to correct the flow calculated from the anemometer readings (see
Figure 2).

Chamber Use For Pn Measurement

To use the chambers, the air supply system was set up, connecting the pipes
with duct tape. Typically, the air supply system was shaded to reduce heat buildup in
the system. Two vines were placed in position at the ends of the air inlet pipes and
air flow was set on high. The non-porous foam sleeves were placed around the vine
tnmks and the chamber bases latched into place, resting on the pot. The elastic bands
were then placed loosely around the pot so they would be in place when nwded for
bag attachment. The Mylar balloons were carefully lowered over the vines, taking
care to not damage leaves, shoot tips or fruit and their bases constricted around the
chamber base and allowed to fill with air. Finally, the elastic bands were moved into
place to attach the balloons to the chamber base.

Once inflated, air flow to the balloons was reduced to a rheostat setting of

between 20% and 35% of maximum (air flow of 80 to 250 L min") depending on

27
vine leaf area, and the IRGA sample line was placed in the chamber outlet. After air

flow and chamber pressure had stabilized, air flow was measured and recorded. A
ACO,determination was made when the IRGA readings stabilized. The IRGA was
then set up to sample the second chamber, which at that point was in dynamic
equilibrium, and the measurement process used for the first chamber repeated.

After completing readings for two vines (about 15 to 20 minutes), the air flow
was increased and the balloons removed. Bases and foam sleeves were removed.
Two more vines were then set up. It was possible to measure twelve vines in as little
as 1.5 hours. Data were collected on four replicate vines.

Single Leaf Pn Measurements

Pn of single leaves was measured at the same physiological growth stages as
were whole vines with the exception of harvest. Data were collected on a recently,
fully expanded leaf using an ADC LCA-2 portable, open gas exchange system
equipped with a Parkinson broad leaf chamber and an air supply unit (Analytical
Development Co. , Hoddesdon, U.K.). These data were then used to estimate whole
vine Pn by multiplying the Pn rate per unit leaf area by the estimated leaf area of the
vines. It was then possible to compare the actual whole vine data with the calculated
values.

PLANT MATERIALS

The plant materials used were one-year-old Chambourcin grapevines grafted to
5-C rootstock and potted in 19-L pots using 45% sand, 45% loam and 10% peat.

The vines were watered regularly and fertilized monthly. Vines were divided by their

28
fresh weight prior to planting, into four blocks and and trained to 3-shoots per

individual vine.

The relationship between leaf area and shoot length was determined previously
(10) to be (y = 15.69 x -27.83; r2 = .88). Shoot length measurements were then
used to estimate leaf area at each date of measurement.

RESULTS AND DISCUSSION

The chamber calibration curve is shown in Figure 2. Actual flow rates were
lower than those indicated by the hot-wire anemometer which was likely due to
turbulence caused by the reduction of inlet pipe diameter at the chamber entrance.
The observed differences demonstrate the necessity for chamber calibration for
accurate and precise data.

CO, assimilation per unit leaf area (umol CO, rn'2 see") was measured on an
individual leaf or was calculated from whole vine measurements (Figure 3a). Net
assimilation determined using a single leaf measurement was less than the average
assimilation rate per unit leaf area as determined from the whole vine only at
veraison.

Net CO2 assimilation per vine (umol CO, vine‘l see“) was either measured for
entire vines or estimated from single leaf measurements (Figure 3b). Whole vine Pn
measured for entire vines was greater than the single leaf estimate at veraison only.
The data indicate that using single leaf Pn measurements to estimate whole vine A (in
a potted-vine system with no fruit present) gives good results early in the season.
However, as the season progresses and more leaf area is generated (about 3000 cm2 at

harvest), estimates of whole vine A using a recently, fully expanded leaf, are too low.

29
If one were measuring the carbon uptake of the most rapidly photosynthesizing

leaf and using it to estimate whole plant Pn, an overestimation would occur. This,
however, was not the case here. Compared to the whole vine data, the estimate of
whole plant A from single leaf determinations was similar at bloom and at the 5mm
berry stage and low at veraison. While we used a recently fully expanded leaf for
consistency among treatments (as do many studies -Edson, 1991; Gucci et al., 1991),
this leaf position was shown by Poni et al. (1994a) to be photosynthesizing at the
highest rate on the plant only during mid-season in grape. Earlier in the season
(around bloom), more basal leaves showed the highest photosynthetic rates whereas
apical leaves had the highest rates late in the season (veraison through harvest).

Apparently, as the plant grows and the canopy becomes more complex, it is
increasingly difficult to select a leaf which will give a meaningful estimate of the
average Pn of the plant. It is for this reason that whole plant Pn chambers are
necessary for accurate and precise whole plant Pn measurement. Whole plant
chambers integrate Pn from all leaf types as well as respiration from the various
aerial organs of the plant and give a good estimate of whole plant carbon assimilation
(Figure 4). In addition, using potted, one-year old grapevines at veraison, there was a
positive, linear relationship between whole vine Pn and whole vine dry weight.
However, more data are required to verify this observation both at veraison and at
other phenological stages.

Corellii-Grappadelli and Manganini (1993) demonstrated the use of the

Parkinson broad leaf chamber to measure total transpirational losses from trees in

30
their chamber. While this was not attempted, it is possible that it could work on the

whole-plant chambers described herein as well.

Considerable variability exists among vines in their photosynthetic responses to
treatments. Pre-selection of plant materials is therefore recommended prior to
attempting whole plant measurements (e.g. blocking by fresh weight prior to
planting). It would also be useful to have a group of plants from which those to be
measured could be selected based on uniformity of growth.

CONCLUSION

Use of whole plant, open gas exchange systems gives a more accurate
indication of carbon assimilation under various conditions. Attempting to infer whole
plant responses from single leaves involves many assumptions (e. g. all leaves
photosynthesize at the same rate; all leaves are perpendicular to incident radiation)
and cannot integrate respiration by organs other than leaves. The whole plant gas
exchange system described measures Pn of potted plants, integrating respiration and

other factors affecting Pn to give a better measure of whole plant carbon assimilation.

31

LITERATURE CITED

Candolfi-Vasconcelos, MC. and W. Koblet. 1991. Influence of partial defoliation on
gas exchange parameters and chlorophyll content of field grown grapevines -
Mechanisms and limitations of the compensation capacity. Vitis 30: 129-41.

Corelli-Grappadelli, L. and E. Magnanini. 1993. A whole-tree system for gas
exchange studies. Hort. Sci. pp 2841-5.

Edson, CE. 1991. Influence of crop level on single leaf and whole vine
photosynthesis and dry matter partitioning in Seyval grapevines (V itis sp.) Doctoral
Dissertation, Michigan State University. p 169.

Flore, J.A. 1994. Stone fruit. In: Environmental Physiology of Fruit Crops Vol. I:
Temperate Crops. B. Schaffer and P.C. Andersen (Eds) CRC Press, Inc. pp 233-70.

Flore, J.A. and A.N. Lakso. 1989. Environmental and physiological regulation of
photosynthesis in fruit crops. Hort. Rev. 11:111-46.

Gucci, R., C. Xyiloyannis and J.A. Flore. 1991. Diurnal and seasonal changes in
leaf net photosynthesis following fruit removal in plum. Physiol. Plant. 41:497-505.

Heinecke, A.J. and NF Childers. 1937. The daily rate of photosynthesis during the
growing season of 1935, of a young apple tree of bearing age. Cornell Univ. Agr.
Expt. Sta., Ithaca, N.Y. Mem. 201.

Katerji, N., F.A. Daudet, A. Carbonneau and N. Ollat. 1994. Photosynthesis and
transpiration studies with traditionally and lyre-trained vines. Vitis 33: 197 -203 .

Long, SP. and LE. Hallgren. 1985. Measurement of CO, assimilation by plants in
the field and in the laboratory. In: Techniques in bioproductivity and photosynthesis.
J.Coombs, D.O. Hall, S.P. Long, and J.M.O. Scurlock (Eds), pp 62-94.

Miller, D.P., G.S. Howell and J.A. Flore. 1995. Effect of varying numbers of shoots
on grapevines: I. Canopy development and morophology. In press.

Pauly, S. Permeability and diffusion data. 1989. In: Polymer handbook, 3rd. Ed.
Wiley, New York pp 435-49.

32

Poni, S., C. Intrieri and O. Silvestroni. 1994a. Interactions of leaf age, fruiting, and
exogenous cytokinins in Sangiovese grapevines under non-irrigated conditions I Gas
Exchange. Am. J. Enol. Vitic. 45:71-8.

Poni, S., C. Intrieri and O. Silvestroni. 1994b. Interactions of leaf age, fnriting, and
exogenous cytokinins in Sangiovese grapevines under non-irrigated conditions. II
Chlorophyll and nitrogen content. Am. J. Enol. Vitic. 45:278-84.

    
   
  

.mylar bag

-reference

V Q " if, ADC unit
r

m J)” n sampling port

for air flow

\
A

 

 

 

 

Figure la Whole-plant gas-exchange system showing both chambers, air supply system,
location of air flow measurement ports and IRGA hookup.

non-porous mylar bag
foam collar

airflow diffuser

 

Figure lb. Detail of chamber base showing, non-porous foam collar sealing the trunk,
latches for fastening chamber halves, air diffuser, and attachment of Mylar balloon with
elastic band. Inset shows detail of elastic band positioning and attachment.

34

 

35“ y= .sosoox+ -.10317
r2 = .9999

 

Flow (1 sec'l) from C0, dilution

 

 

 

IIIW'I I I I I THY—I

-l
Anemometer flow (1 sec )

Figure 2. Relationship between actual flow rate (as determined by dilution
of C02) and flow as measured by hot-wire anemometer.

35

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12
A 10': A
'70 q
a ..
r: 8'2
E d
o" o i
U .
'5 i
i 4- J
v d
< I
2-
1
1
0 1 l 1 J l l l 1 LI glM l l l l l I l l I J. l l 1 L4 1 J 1 1 l l l 1 EL 1 1
3 d
2.5-:
A q
'7 1
r 2‘.
'7 I
E 1.51
N
0 .
U 1...
'5 :
g .
1
V 0.5-l
< :
0 I I IITT Y I I I fir I I r I Eff j—TT T Tfi I I l I Ij T l I I I I

 

T * ' I
300 400 500 600 700 800 900 1000 l 100
Growing Degree Days (base 10 C)

Figure 3. CO2 assimilation (A) of Chambourcin grapevines. Measurment using a Parkinson broad-leaf
chamber (I); or whole-plant chambers (O). A) CO2 assimilation per unit leaf area (umol CO2 m'2
sec“) and; B) CO2 assimilation per vine(umol CO2 vine'l sec"). Bars represent the LSD at p = 0.05.

36

135

 

y = 1.01293x + 5.77849 I
r = .5299 .

125-

Vine dry weight (g)
a ”3‘ E
l l l

 

 

 

 

85-
75- .
‘ I
65-
QANWHAAWW...,..,.,.e-,,....,-...
2 2.5 3 3.5 4 4.5 5 5.5

Whole vine A (umol CO2 m"2 sec'l)

Figure 4. Relationship between whole vine CO2 uptake at veraison and
vine dry weight at harvest for potted Chambourcin grapevines.

37

H. EFFECT OF SHOOT NUMBER ON POTTED GRAPEVINES: I.
CANOPY DEVELOPMENT AND MORPHOLOGY

ABSTRACT

Potted, one-year-old Chambourcin grapevines grafted to 5-C rootstock were
grown with one- three- or six-shoots in the absence of fruit to determine the effect of
competition between vegetative sinks on canopy morphology and development. As
shoot number increased, leaf area per shoot, shoot length, leaf size and flower cluster
length decreased for individual organs. On a whole vine basis, total leaf area, shoot
length and flower cluster length increased with increasing shoot number. Leaf area of
three- and six-shoot vines was 38% greater than that of one-shoot vines at harvest.
Vine dry weight at harvest, however, was greater for three- and six-shoot vines only
at p 2 0.10. Whole vine photosynthesis (Pn) measurements showed no differences
among treatments at bloom, but Pn had a positive, linear relationship to shoot number
both at 5mm-berry size and at veraison. These data indicate that: (1) smaller flower
clusters and less leaf area per shoot are responsible in part for the reduction in shoot
fruitfulness observed in vines with many shoots; (2) many shoots allow a vine to
develop greater leaf area relative to vines with few shoots earlier in the growing
season and produce more vegetative sinks for carbohydrates; and (3) the presence of
relatively large shoot numbers causes important morphological changes in canopy
vegetative structure. These include shorter shoots and smaller leaves and flower

clusters but greater shoot length, leaf area and flower cluster length per vine.

38
INTRODUCTION

Grapevine canopy management seeks to maximize leaf capture of solar
radiation, while at the same time providing an optimum environment for fruit
maturation and development (17 , 18, 19,20). Research has shown that the high bud
numbers retained on minimally pruned (MP) vines allow the canopy to develop more
rapidly during the spring growth flush (3,4,5,14). Studies using vines which were
skirted to remove low-hanging canes (3 ,4) or hedged (14) showed dramatic increases
in yields over controls. The authors of those studies hypothesized that the large,
early-season canopy surface increased the capacity of MP vines to produce crop,
thereby causing the large yields. However, since the MP vines also had larger cluster
and berry numbers relative to spur pruned controls, it is unclear if the large early-
season leaf surface of MP vines is the sole cause of the increased yields, particularly
in the absence of vine dry weight data over a growing season. Wilson (23)
demonstrated that growth in Brassica and Helianthus was sink limited; the factor most
limiting to growth rate was rate of leaf production (sinks during development). This
may also be true in severely pruned grapevines. Additionally, the relatively small
number of shoots on severely pruned vines may carry insufficient fruit to fully utilize
the vines fruit production potential.

Carbohydrate reserves support canopy development during the spring growth
flush (9,15,26,27,28). It follows that as the quantity of reserves varies, so will the
quantity of growth that they can support or, conversely, that a given quantity of
reserves will support a finite amount of growth. Yang and Hori (26,27) and Yang, et

al. (28) demonstrated that carbohydrate reserves are utilized to support shoot growth

39
up to appearance of the tenth leaf. Mobilization of reserves increased through the

expansion of the sixth leaf, then declined. By contrast, basal leaves began exporting
current assimilates after the fifth leaf emerged. Maximum shoot growth rates
occurred when both reserves and current assimilate were available as energy
substrates. McLaughlin et al. (9) calculated the energy required to support the growth
flush of the canopy of a mature white oak (Quercus alba L.). However, to our
knowledge, no work has been done to quantify the amount of canopy that can be
generated during the growth flush by grapevines with a given quantity of reserves or
toquantifytheinfluenceofvaryingcanopyleafareaattheendofthegrowthflushon
net, annual dry weight accumulation for whole vines.

To maximize the production potential of grapevine’s , it is critical to have a
better understanding of source/ sink relationships which occur during the growth flush
as the canopy is developing. The objectives of this experiment were to determine: (1)
if competition from vegetative sinks alters canopy morphology; (2) whether greater
shoot numbers result in greater dry matter production; (3) at what point during the
growing season shoot number might influence dry matter production; and (4) if
changes in canopy morphology can influence shoot fruitfulness.

Fruit are active sinks that are very competitive with vegetative tissues for
carbohydrates (2,6,23,24,25). It is difficult for experimental purposes, however, to
establish fruiting sinks of the same relative strength on vines with varying canopy
morphologies. Therefore, to study the effect of competition among shoots on canopy

morphology, it is necessary to conduct the experiments in the absence of fruit. It is

40
also necessary to use potted vines to adequately assess canopy morphology and tissue
dry weights.

MATERIALS AND METHODS

Plant Material

One-year-old Chambourcin grapevines grafted to 5-C rootstock were planted in
19 liter plastic pots with a 45% sand, 45 % loam and 10% peat sterile potting mix on
May 26, 1993. The potted vines were placed on pea-gravel in full sun and watered
regularly. Fertilizer was applied as a balanced N,P,K solution once per month.
Pesticides were applied occasionally as conditions warranted.

When buds were at the swell-two stage (7) of development (elongated sphere
prior to burst), their numbers were adjusted to retain three treatments in which one,
three or six buds which were allowed to develop. As the vines grew, all laterals were
removed once per week. Flower clusters were retained for measurement until bloom
at which time they were removed. Fruit was retained on several additional monitor
vines not in the experiment but selected from the same group of vines so fruit
phenology could be followed and used as a reference as the season progressed. While
the non-fruiting vines may have had slightly altered phenology from the fruited vines,
this approach gave a reasonable estimate of phenological stage of development.
Phenological stages used in the study were: "bloom” (50% of flowers in bloom);
5mm berries; veraison (30% of berries showing coloration); harvest (fruit at 20 ”brix
and pH 3.45); and dormancy (all leaves fallen).

Vines were blocked by fresh weight prior to planting producing four blocks.

Treatments were randomly assigned to 12 vines for each treatment in each block. At

41

various intervals (described below), one vine of each treatment within each block was
selected for destructive harvest. The experimental design was a randomized complete
block with three treatments and four replicates, harvested on nine dates for a total of
108 vines.
leaf Area and Canopy Measurements
Vines were destructively harvested at approximately five-day intervals
(reported as growing degree days (GDD) base 10°C) during the period from bud
burst through bloom, on dates when monitor vines achieved 5mm berry diameter,
veraison and at fruit harvest for a total of nine harvests. leaf area was determined
using a Li-Cor LI-3000 portable leaf area meter (Lambda Instrument Corp. , Lincoln,
Nebraska). length was recorded for individual shoots and cluster primordia until the
time of cluster removal, after which only vegetative structures were measured.
Vine Dry Weight
Dry weight was determined at each destructive harvest by partitioning the
vine into its various organs and recording the fresh weight of each. The tissues were
then placed into paper bags in a drying oven at 600C until no further weight
reduction occurred (approximately 4 days). After drying, tissue weights were
recorded and percentage water content calculated. Only the dry weight recorded at
the date of monitor vine fruit harvest is reported here.
Photosynthesis
CO, assimilation(A), leaf conductance (g,), photosynthetic photon flux density
(PPFD), leaf temperature (T) and air relative humidity (RH) were determined for

single leaves and CO, assimilation only was determined for whole vines. Single leaf

42
A was determined on a recently fully expanded leaf using an ADC LCA-2 portable

open gas exchange system equipped with a Parkinson broad leaf chamber and an air
supply unit (Analytical Development Co. , Hoddesdon, UK). Whole vine A was
determined using a whole plant open gas exchange, Mylar chamber as described in
Chapter 1. Air flow rates of 400 ml min" were used for single leaf measurements
and 180-250 L min‘1 used for whole vines. Measurements were at 20% full bloom,
after anthesis when berries of monitor vines were 5 mm diameter, and at veraison for
single leaves and whole vines. Only single leaf A was determined at harvest as
weather conditions would not permit a whole vine determination. Both single leaf and
whole vine measurements were made between 11:00 and 13:00 hours (solar time)
when PPFD levels were at least 1000 umols m‘2 sec".
Data Analysis

Means were calculated on a per shoot and per vine basis using Lotus 123
Release 4 (Lotus Development Corp. , Cambridge, MA). These data were further
analyzed with the MSTATC statistical package (MSTATC, Michigan State University,
East Lansing, MI) using a two-way Analysis of Variance and orthogonal contrasts
where appropriate. Regression analyses were performed using DeltaGraph (Delta
Point Inc. , Monterey, CA).

RESULTS

Leaf Area

leaf area per shoot was inversely related to shoot number at every destructive

harvest (Figure 1a). Leaf area per shoot of three-shoot vines was greater than that of

six-shoot vines only at bloom, veraison and harvest.

43
leaf area per vine varied after bud burst until about l-week before bloom (305

GDD) (Figure 1b). After that point, there was a positive, quadratic relationship
between leaf area per vine and shoot number at every date. leaf area per vine
differences were established by 385 GDD. Leaf area per vine increased in all
treatments from bud burst through veraison but continued to increase from veraison
through harvest (1020 to 1141 GDD) for three- and six-shoot vines only (Figure 1b).
The rate of leaf area increase per vine was similar for all treatments between 385 and
1020 GDD (Figures 1b and 2a). The rate of leaf area increase for three- and six-
shoot vines reached a maximum at 384 and 219 GDD, respectively, while one-shoot
vines reached a maximum rate at 219 GDD (Figure 2a). Three— and six-shoot vines
had approximately 1.3 and 1.6 x the leaf area of one-shoot vines at veraison and
harvest, respectively (Figure 1b).

Leaf size was inversely related to shoot number on every date (Figure 1c).
leaf size of three- and six-shoot vines was always similar.

leaf number per shoot was inversely related to shoot number on every date
(Figure 2b). Three-shoot vines had more leaves per shoot than did six-shoot vines
after 305 GDD. Leaf number per shoot in one-shoot vines was nearly twice that of
six-shoot vines at bloom (8.3 vs. 4.4) and harvest (20.5 vs. 11.7).

There was a positive, linear relationship between leaf number per vine and
shoot number starting shortly after bud burst (Figure 2c). leaf numbers of three- and
six-shoot vines were 2 and 2.5 x respectively those of one-shoot vines on nearly every
date. After veraison, leaf production ceased on one-shoot vines but continued on

three- and six-shoot vines.

Shoot Growth

Mean individual shoOt length was inversely related to shoot number per vine
throughout the growing season (Figure 3a). Shoots of three-shoot vines were longer
than those of six-shoot vines at harvest only.

A positive relationship existed between shoot length per vine and shoot number
at each date except at bloom and in dormant vines when no differences were found
(Figure 3b). Dormant cane lengths and shoot lengths at harvest of one-shoot vines
were similar. Dormant cane lengths of three-and six-shoot vines, however, were
dramatically less than their harvest shoot length due to a loss of non-lignified tissue to
frost. The percentage of nodes which lignified was inversely related to shoot number
(90%, 70%, and 57% for one, three and six shoots, respectively).

Intemode length varied among treatments before bloom but was inversely
related to shoot number at every date between bloom and dormancy (Figure 3c).
lntemode length was generally the shortest in six-shoot vines. However, at bloom
intemode length of six-shoot vines was intermediate to that of one- and three-shoot
vines.

Flower Cluster Development

Flower cluster development was linearly related to both mean leaf size and
mean shoot length per shoot (Figures 4a and 4b). The result was flower clusters
which were nearly twice as long on one-shoot vines as those on six-shoot vines
(70.3 mm vs. 38.3 m). At bloom, mean cluster length per shoot was 27 mm for

six-shoot vines compared to 123 mm for one-shoot vines. One- and six-shoot vines

45
had 1.8 and 0.7 clusters per shoot, respectively. Cluster length per vine was linearly

related to shoot length per vine (Figure 4c) resulting in greater flower cluster length
per vine as shoot number (and shoot length) per vine increased.
Dry Weight of Vines

Dry weights of trunks, roots, shoots and whole vines were not different among
treatments at 1141 GDD (harvest in this experiment) (Figure 5). Whole vine dry
weight increased linearly with shoot mrmber (y = 3.59x + 83.53; r2 = .526) at that
time but the relationship was significant only at p5 0.10. leaf dry weight was
greatest in three- and six-shoot vines. Shoots of three- and six-shoot vines had a
higher water content than did one-shoot vines (59.2%, 60.0% and 56.3%,
respectively). This reflects the lower percentage of lignified nodes on three- and six-
shoot vines compared to one-shoot vines. Fresh weight of whole three- and six-shoot
vines was greater than that of one-shoot vines at p50.05 (298g, 293g and 238g,
respectively).

A regression of whole vine dry weight on leaf area shows that leaves of one-
shoot vines were more efficient at dry weight assimilation than were leaves of three-
and six-shoot vines (Figure 6). leaves of one-shoot vines assimilated 0.040g of dry
weight per cm2 leaf area, whereas three- and six-shoot vines assimilated only 0.035 g
dry weight per cm’.

Photosynthesis
Single leaf assimilation rates were not different among treatments on any of

the four measurement dates (Figure 7a). Stomatal conductance and transpiration rate

46
were higher, and vapor pressure deficit lower for one-shoot vines than for three- and

six-shoot vines only at harvest (data not shown).

Whole vine CO, assimilation increased linearly with shoot number at 5mm
berry size and veraison (r2 = 0.966 and 0.918, respectively) (Figure 7b). Vines of
all treatments were assimilating at nearly the same rate prior to bloom.

DISCUSSION

Rate of leaf area development increased as shoot numbers increased,
apparently due to greater leaf numbers as shoot number per vine increased. A
grapevine has the potential to assimilate a finite amount of carbon during a given
growing season (6). However, the amount of carbon assimilated is dependent on
environmental conditions, and the balance of carbohydrate sources and sinks. If the
number of shoot apical meristems is limited (e. g. by severe pruning), they will grow
rapidly and the leaf blades will expand to their maximum possible size but canopy
development may be slowed by the low number of shoots and points of leaf initiation
(i.e. canopy development is "sink” limited) (22,23). In this situation, there are
adequate carbohydrate reserves and root-supplied substances to support the maximum
rate of growth per shoot. As shoot numbers increase, they begin to compete with one
another for available carbohydrates, water, nutrients and root-supplied resources such
as cytokinins. At this point, the actual amount of growth per shoot is reduced but
canopy development potential and shoot length per vine are maximized.

Changes in leaf and shoot morphology with increasing vegetative competition
are similar to those caused by water stress (8). This result would be expected if the

demand for water by apical meristems and leaf blades was greater than the supply of

47
water provide by the roots and xylem. There appears to be a point at which shoot

numbers are in optimum balance with the vine’s growth potential (in our experiment it
was when three shoots were present). In "small" field-grown Concord vines, yields
were similar when pruned to either 90 or 120 nodes (11). By contrast, ”large” vines
had higher yields with 120 nodes compared to 90 nodes. Beyond the point of
maximized growth, there is no obvious benefit of having additional shoots but there is
a morphological effect; the additional shoots are shorter with fewer, smaller and less
efficient leaves. In this case, shoot growth is source limited (22).

There apparently is an upper limit to the mrmber of shoots a vine can support
above which the vine becomes source limited. In this experiment, six shoots were
originally retained from 12 or more swelling buds on the six-shoot vines. As growth
began, some shoots ceased growth and some buds never burst. Of the shoots which
remained, two or three often grew at a higher rate than did others, suggesting that a
competition was occurring for available resources. Clingeleffer (3) demonstrated that
as the node number retained at pruning increases, the percentage of nodes producing
shoots decreased; 48 nodes produced 59 shoots (123%) and 336 nodes produced 204
shoots (61%).

Shoot length, leaf size, leaf area and flower cluster length on a given shoot are
linearly related. Flower cluster length and the number of florets per cluster are also
linearly related (data not shown), so shorter shoots have fewer flower clusters and
fewer flowers per cluster. In itself this would result in reduced fruitfulness.
However, fruitfulness may be further reduced if the carbohydrates available at bloom

are reduced relative to severely pruned vines (1). The combination of smaller flower

48

clusters, fewer flower clusters per shoot and lower carbohydrate production per unit
leaf area on lightly pruned vines would explain in part the large reduction in shoot
fruitfulness observed with increasing shoot numbers in field studies (3,4,5,10). As
shoot number and shoot length per vine increase, total flower mrmber per vine
increases as well. It is thus possible to increase the total number of berries per vine
even as the fruitfulness of individual shoots declines.

The greater leaf area of three- and six-shoot vines was responsible for greater
whole vine Pn and slightly greater dry weight at harvest. Further research will
determine how both potted and mature vines will respond in the presence of fruit.
Whole vine Pn was similar for all treatments prior to bloom. The small additional
dry matter production was apparently the result of greater carbohydrate sink activity
and greater exposed leaf area from bloom through harvest. These data indicate that
canopy surface area at bloom influences annual carbohydrate assimilation only slightly
in potted vines under the conditions imposed in this study.

More research using mature vines is necessary to find the optimum number of
shoots which will maximize annual dry matter production and produce sufficient berry
numbers to maximize the vines production of high quality fruit while building
reserves in preparation for the subsequent growing season. This concept was first
outlined by Partridge in 1926 as "balanced pruning” (13). Since current approaches
will likely employ both pruning and crop reduction to achieve the desired crop load, a

more accurate name might be "balanced cropping" (16).

49
CONCLUSION

In young, potted vines with no fruit, increasing shoot number results in an
alteration of canopy morphology. Vines with a relatively large number of shoots
present a larger leaf surface for a greater portion of the growing season, but one that
is less productive per unit leaf area, than vines with fewer shoots. The result is a
small increase in dry matter production with increasing shoot number, that occurs
between bloom and harvest in the absence of fruit. The effect of shoot competition
on canopy morphology may explain the reduction in shoot fruitfulness observed in
minimally pruned vines in commercial vineyards. Shoot competition results in shorter
shoots with smaller flower clusters and fewer flowers per cluster. This phenomenon
may be utilized to produce less compact clusters in tight-clustered varieties by
reducing fruit set and berry size, and be useful as a tool in an integrated approach to

viticulture.

50

LITERATURE CITED

1. Candolfi-Vasconcelos, M.C. and W. Koblet. Yield, fruit quality, bud fertility,
and starch reserves of the wood as a function of leaf removal in Vitis yjr_ri_fe;a -
Evidence of compensation and stress recovering. Vitis 29:199-221 (1990).

2. Chandler, W.H. and A.J. Heinicke. The effect of fruiting on the growth of
Oldenberg apple trees. Proc. Am. Soc. Hort. Sci. 23:36-46 (1926).

3. Clingeleffer, P.R. Vine response to modified pruning practices. In:
Proceedings of the Second N .J . Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 2030. Cornell University Press, Geneva, New York (1993).

4. Clingeleffer, P.R. and LR. Krake. Responses of Cabernet Franc grapevines
to minimal pruning and virus infection. Am. J. Enol. Vitic. 43:31-7 (1992).

5. Downton, W.J.S. and W.J.R. Grant. Photosynthetic physiology of spur
pruned and minimal pruned grapevines. Aust. J. Plant Physiol. 19:309-16 (1992).

6. Edson, C.E. Influence of crop level on single leaf and whole vine
photosynthesis and dry matter partitioning in Seyval grapevines (Vitis sp.). Doctoral
dissertation, Michigan State University, East Lansing, MI. p 169 (1991).

7. Johnson, DE. and GS Howell. Factors influencing critical temperatures of
primary buds on grape canes. J. Am. Soc. Hort. Sci. 106:545-9 (1981).

8. Liu, Z. and DJ. Dickrnann. Responses of two hybrid Populus clones to
flooding, drought and nitrogen availability. 1. Morphology and growth. Canadian
Journal of Botany. 70:2265-70 (1992).

9. McLaughlin, S.B., R.K. McConathy, R.L. Barnes and N.T. Edwards.
Seasonal energy allocation by white oak (Mus alga). Can. J. For. Res. 10:379-88
(1980).

10. Miller, D.P. and GS Howell. Effect of shoot number on potted grapevines.
II. Dry matter accumulation and partitioning. Am. J. Enol. Vitic. 47 (accepted for
publication, 1996).

51

11. Miller, D.P., G.S. Howell and R.K. Striegler. Reproductive and vegetative
response of mature grapevines subjected to differential cropping stresses. Am. J.
Enol. Vitic. 44:435-40 (1993).

12. Mitchell, T.G. Vineyard mechanization and its impact on production costs in
the Taylor Wine Company vineyards. In: Proceedings of the Second N .J . Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), pp 66-68. Cornell
University Press, Geneva, New York (1993).

13. Partridge, N.L. The use of the growth-yield relationship in field trials with
grapes. Proc. Am. Soc. Hort. Sci. 23:131-4 (1926).

14. Pool, R.M., R.E. Dunst, D.C. Crowe, H. Hubbard, G.E. Howard and G.
Degolier. Predicting and controlling crop on machine or minimal pruned grapevines.
In: Proceedings of the Second N.J. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed) pp 31-45. Cornell University Press, Geneva, New York (1993).

15. Quinlan, I.D. Mobilization of 1‘C in the spring following autumn assimilation
of 1“CO, by an apple rootstock. J. Hort. Sci. 44:107-110 (1969).

16. Reynolds, A.G., R.M. Pool and LR. Mattick. Effect of shoot density and
crop control on growth, yield, fruit composition and wine quality of ’Seyval blanc’
grapevines. J. Amer. Soc. Hort. Sci. 111:55-63 (1986a).

17. Reynolds, A.G., R.M. Pool and LR. Mattick. Influence of cluster exposure
on fruit composition and wine quality of Seyval blanc grapes. Vitis 25:85-95
(1986b).

l8. Shaulis, NJ. and R.E. Smart. Grapevine canopies: management,
microclimate and yield responses. 20th International Horticultural Congress,
Warzawa. pp 255-65 (1974).

19. Smart, R.E. Climate, canopy microclimate, vine physiology and wine quality.
In: Proceedings of the International Symposium on Cool Climate Viticulture and
Enology. D.A. Heatherbell, P.B. Lombard, F.W. Bodyfelt and SF. Price (Eds), pp
1-18. Oregon State University Experiment Station Technical Publication No. 7628
(1985).

20. Smart, R.E. Principles of grapevine canopy microclimate manipulation with
implications for yield and quality. A review. Am. I. Enol. Vitic. 36:230-39 (1985).

21. Sommer, K.J. and P.R. Clingeleffer. Comparison of leaf area development,
leaf physiology, berry maturation, juice quality, and fruit yield of minimal and cane
pruned Cabernet sauvignon grapevines. In: Proceedings of the Second N.J. Shaulis

52

Grape Symposium, Fredonia, New York. R.M. Pool (Ed), pp 14-9. Cornell
University Press, Geneva, New York (1993).

22. Wareing, RF. and J. Patrick. Source-sink relations and the partition of
assimilates in the plant. In: Photosynthesis and Productivity in Different
Environments. J.P. Cooper (Ed), pp 481-99. Cambridge University Press,
Cambridge ( 1975).

23. Wilson, J . Warren. Ecological data on dry-matter production by plants and
plant commumities. In: The Collection and Processing of Field Data. E.F. Bradley
and O.T. Denmead (Eds), pp 77-123. New York: Interscience (1967).

24. Winkler, A.J. Pruning and thinning experiments with grapevines. California
Agr. Exp. Sta. Bull. 519:1-56 (1931).

25. Winkler, A.J., J.A. Cook, W.M. Kliewer and LA. Lider. General
viticulture. University of California Press, Berkley, CA, p 710 ( 1974).

26. Yang, Y.S. and Y. Hori. Studies on the retranslocation of accumulated
assimilates in ’Delaware’ grapevines. I. Retranslocation of “C assimilates in the
following spring after 1‘C feeding in summer and autumn. Tohoku J . Agric. Res.
30:43-56 (1979).

27. Yang, Y.S. and Y. Hori. Studies on the retranslocation of accumulated
assimilates in ’Delaware’ grapevines. III. Early growth of new shoots as dependent
on accumulated and current year reserves. Tohoku J. Agric. Res. 31:120-9 (1980).

28. Yang, Y.S., Y. Hori and R. Ogata. Studies of retranslocation of accumulated
assimilates in ’Delaware’ grapevines. II. Retranslocation of assimilates accumulated
during the previous growing season. Tohoku J. Agric. Res. 31:109-19 (1980).

53

 

. Leaf area shoot'l(cm2)
u—I u—I N
e ‘5? § 8 §
I J l l

veraison harvest

 

 

"(cm
.i.

Leaf area vine

 

8???

 

 

 

 

 

 

 

 

 

 

 

 

rze(cm)
83838
Lrlrlnlrl.

m

‘13 3o-‘
20-:
10-

 

 

 

 

 

I

 

 

 

0

' 1
200

fiI‘l Ii I1 I I I I I I I I l'

, . .
400 600 800 1000 1200
Growing Degree Days (base 10 C)

Figure 1. Leafarea (cm2) for individual shoots (A), whole vines (B) and leaves
(C) of potted Chambourcin grapevines with I shoot (I), 3 shoots (O), or 6

shoots (A). Bars represent the LSD at p = 0.05.

2

Leaf area increase (cm d

54

 

—I— I shoot

 

 

bloom —O— 3 shoots

33’
8
r

  
  
 
 

 

 

 

on
O
l

+ 6 shoots

 

 

 

Os
0
l r

   

veraison
,- -., harvest

A
O
l 1

5mm berries

  
 

N
O
l r

O
.14

 

 

:1)

O
L
F.
r
j.
i-
L.

 

N
III

 

 

 

 

-l
8
.l.r..

In:

Leaf number shoot
b—l f—l
Ll. O U.
l l r l 1 r r
l
H
H
' H
H
r—r
f-—f

 

 

 

 

a 20_ I II
‘a ’1

 

 

 

0-—-r-1—r l

. . . , . . . , . . .
0 200 400 600 800 1000 1200
Growing Degree Days (base 10 C)

I r fT ' I T 7 I

Figure 2. Rate of leaf area increase (cm2 day ’1) (A) and leaf number
of individual shoots (B) and whole (C) Chambourcin grapevines with l shoot

(I), 3 (O) shoots, or 6 (A) shoots. Bars represent the LSD at p=0.05.

55

120

 

Lé

. veraison h est

1

Shoot lenght shoot (em)

dormant

bloom Swedes I I I

N ch 0\ co
0 O ' O O
J l r L l

 

 

 

 

 

 

 

 

 

 

 

M
l

 

A
l

 

N w
L

 

Intemode length (cm)

id
4 l

 

 

O
O

 

'I"‘l"‘l"‘l"‘l"'l“'

200 400 600 800 1000 1200 1400
Growing Degree Days (base 10 C)

Figure 3. Length (cm) of individual shoots (A), entire vines (B) and

intemodes (C) of potted Chambourcin grapevines with l shoot (I),
3 (O) shoots, or 6 (A) shoots. Bars represent the LSD at p=.05.

Flower cluster length (mm)

l

Flower cluster length vine (nun)

 

 

56

 

 

 

 

120 i'—I_'_l
q y=l.278x+-7.8l2
100‘ r'.8259 I
801
so.“
1
4o;
204
‘
o‘I‘l‘I'I'llI'l'l
0 10 20 30 40 50 60 70 80 90 100
2
Leafsize(cm)
350
I

y - 2.127): + 4.470
r - .5763

§
ll AJJJMALAIJA

N
M
O

    

- N
‘1’"?

?

[El

 

 

l I l l

‘7'ill
0 10 20 30 40 50 60 70 80

Shoot length vine.1

Figure 4. Relationship between indin'dual cluster length and leaf size (A); flower cluster length per shoot
and shoot length per shoot (B), and, flower cluster length per vine and shoot length per vine (C) from bud
burst to bloom in potted Chambourcin grapevines.

 

' I
90 100

Flower cluster length shoot (mm)

 

250

'5’
O
l

1 LI. 1 l

u

M

o
1

~
I A A A l

 

y '- 4.967x + -3l.18
r- .8862

 

 

 

..,. .., ..,....,.
lo 20 30 4o
Shoot length shoot" (em)

50

60

Dry weight (g)

120

57

 

    
 

 

 

 

 

 
    

   
    
   

      
  
 
   

     

 

 

: E lshoot

11 El 3shoots

i

.- 6shoots E
I b a a \V 3:;— E
i E a E E
JEI§ El§ E E
j E ,\\\\ E :\\\\ E E

    

  

Leaves Shoots Trunks Roots Whole-vine

Figure 5. Dry weight of vine organs “at harvest of potted Chambourcin

grapevines with l, 3 or 6 shoots. Bars followed by difi‘erent letters are different

mp=005

 

58

 

     
 

 

 

 

14o
; y = .03450x + -5415 A
120; r2=.9220 o
: y: .04014X + 6.795 3 shoots .
_ = I
7,3100- r2 .9014 I
:2 _ I shoot
.4: q
no _ A
.5 80 _ \
3 - _
.5 60—
o I
.5 -
> 40-_ y=.03231x+.38l9
I r2=.858l
20-_ éshoots
O‘"l""l""l""l""l""l""
o 500 1000 1500 2000 2500 3000 3500

Leaf area (cm2)

Figure 6. Relationship between leaf area and vine dry weight (g) of
potted Chambourcin grapevines with 1(I), 3 (O) or 6(A) shoots.

59

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A12,
"a 10: A
E 8-j
8" 6-5 5mmberries
"" .3 veraison
E 4 bloom
3 2- harvest
< o 4._L I In 1 l l l E l 41.-.-lnr
a; 3
m 1
'0 2_ ,
E J -I— lshoot
c?
e
g + OShOOtS
<0 -.. .,.-E.j.t..,.fi.,...+,-e..T-.

., . . . A 1
300 400 500 600 700 800 900 1000 1 100 1200
Growing Degree Days (base 10 C)

Figure 7. A) Single leaf CO2 assimilation rate (A) (umol CO2 m2 s'l); B) whole vine A
(umol CO2 vine’1 sec'l ), measured with whole-plant chambers using potted
Chambourcin grapevines with 1 (I), 3 (O) or 6 (A) shoots.

60

HI. EFFECT OF SHOOT NUMBER ON POTTED GRAPEVINES: H. DRY
MATTER ACCUMULATION AND PARTITIONING

ABSTRACT

Potted, one-year old Chambourcin grapevines were grown with one, three or
six shoots in the absence of fruit to determine the impact of increasing early-season
leaf area on dry weight accumulation throughout the growing season. No fruit was
retained so the role of vegetative sinks could be more carefully studied. Very few
differences in dry weight were found for vegetative organs (roots, trunks, shoots and
leaves) among the three treatments. Six-shoot vines had greater shoot weight just
after bud burst, but at veraison and harvest, there was an inverse, linear relationship
between shoot number and shoot dry weight. Three- and six-shoot vines had greater
leaf and total canopy dry weights (leaves + shoots) at harvest only. Total plant dry
weight was slightly greater with increasing shoot number at harvest only. No other
differences were detected in vine dry weight during the growing season. While dry
weight differences were not large, increasing shoot numbers affected canopy
morphology. Specific leaf and shoot weights decreased as shoot numbers increased,
but leaf area per unit shoot weight increased. Additionally, the ratio of cane fresh
weight to storage tissues (roots + trunks) was inversely related to shoot number.
These results support the hypothesis that cane fresh weights are of questionable value

when used to estimate the cropping capacity of minimally pruned vines.

61
INTRODUCTION

A goal of grape growers is to maximize the yield of fruit of a desired
composition per unit land area while keeping production costs low. Since the limits
of acceptable fruit composition differ among processors, each grower must decide
between increasing yields or better fruit composition. When machines are used to
prune or "hedge" a dormant vineyard, there is a cost savings over the use of hand
labor (16). Dramatic yield increases have been reported in both cool climate and
semi-arid vineyards when vines were subjected to minimal pruning (MP) or ”skirting"
(removing only low hanging canes by machine) as compared to hand-pruned controls
(3,4,5,17,23). MP vines, it is thought, assimilate more carbon over a growing season
than do spur pruned vines, because of the rapid canopy development caused by the
growth of many shoots. It is suggested that this enables MP vines to produce and
ripen larger crOps (3,4,12,23). MP vines, however, bear many more clusters and
berries than do spur pruned vines. Without vine dry weight data, it is unclear if the
larger canopy is solely responsible for the larger yields of MP vines (5,12,15,17,23).
It is possible that redirection of carbohydrates to fruit at the expense of vegetative
tissues supports fruit development with no net change in canopy dry weight.
Substantial effort has been invested to understand the effects of canopy microclimate
on fruit quality (l9,20,2l,22), but little effort has been expended to investigate
canopy development during the spring growth flush and whole-vine carbon
assimilation over the course of the growing season with varying early-season canopy

area.

62
Whole vine CO, assimilation (A) increased with shoot number in potted vines

with no fruit (15). The differences were greatest between bloom and veraison; the
time between bud burst and bloom was a period of relatively low carbon uptake.
Vine dry weight was only slightly greater at harvest in vines with greater shoot
numbers. In addition, the relationship between increasing shoot numbers and
photosynthesis is asymptotic: carbohydrate assimilation increases with shoot number
to a point, and then plateaus. There is an effect, however, on shoot, leaf and cluster
morphology with increasing shoot numbers which resembles a drought response
(8,26). Water availability to "sinks” may be limited if demand outstrips the water
supply from the roots and xylem, even under well-watered conditions. The influence
that early-season (bud burst through bloom) canopy area has on carbon assimilation at
various times throughout the growing season remains in question, however.

The objective of this research was to monitor the dry weight accumulation and
partitioning of potted grapevines with increasing numbers of shoots to determine; (1)
the rate at which reserves are utilized during the growth flush when different numbers
of vegetative sinks are present; (2) if and at what periods during the growing season
greater dry matter production occurs with increasing shoot numbers; and (3) the
relationship between the dry weights of various organs with increasing numbers of
vegetative sinks.

MATERIALS AND METHODS

Plant Material
On May 26, 1993, one-year old Chambourcin grapevines grafted to 5-C

rootstock were planted in 19-liter plastic pots with a 45% sand, 45% loam and 10%

63
peat sterile potting mix. Potted vines were placed on pea-gravel in full sun and

watered regularly. Fertilizer was applied as a balanced N,P,K solution once per
month. Pesticides were applied occasionally, as conditions warranted.

When buds were at the swell-2 stage (9) of development (elongated sphere
prior to burst), their numbers were adjusted to give either 1, 3 or 6 developing buds.
As the vines grew, all laterals were removed once per week. Flower clusters were
retained for measurement until bloom at which time they were removed. Fruit was
retained on several "monitor" vines not in the experiment but selected from the same
group as the experimental vines so fruit phenology could be followed and described as
the season progressed. Phenological stages used in the study were: bloom (50% of
flowers in bloom); 5mm berries; veraison (30% of berries showing coloration);
harvest (fruit at 20°brix and pH 3 .45); and dormancy (all leaves fallen).

Vines were blocked according to their fresh weight prior to planting,
producing four blocks. Treatments were randomly assigned to 12 vines for each
treatment in each block. At various intervals (described below), one vine of each
treatment within each block was selected for destructive harvest. The experimental
design was a randomized complete block with three treatments, four replicates and
nine harvest dates for a total of 108 vines.

Vine Dry Weight

Vines were destructively harvested at approximately five-day intervals
(reported as growing degree days (GDD) base 10°C) during the period from bud burst
through bloom, at 5mm berry diameter, veraison, harvest and when vines were

dormant. One group of vines was also destructively harvested prior to planting to

64
provide baseline weight data. Short time intervals were used between bud burst and

anthesis to determine the rate of reserve utilization during the storage-dependent
growth flush. Dry weight was determined at each destructive harvest by partitioning
the vine into its various organs and recording the fresh weight of each. The tissues
were then placed into paper bags in a drying oven at 60 °C until no further weight
reduction occurred, generally about four days. After drying, tissue weights were
recorded and percentage water content was calculated.
leaf Area

leaf area was determined using a Li-Cor LI-3000 portable leaf area meter

(Lambda Instrument Corp. , Lincoln, Nebraska) at each destructive harvest date.
Non-Structural Carbohydrate Analysis

Samples for non-structural carbohydrate analyses were collected at the time of
vine partitioning. Tissue samples were selected as follows: (a) 2 or 3 leaves from the
mid-shoot; (b) approximately a 2 cm long segment from the basal five node region of
the shoot; (c) approximately a 2 cm long complete cross-section from the mid-trunk;
(d) old, suberized roots (2.5-4 mm dia.); and (e) young non-suberized (1-2 mm dia.)
roots in roughly equal quantities, which were then combined. Samples were weighed
and immediately frozen in liquid N. Within 24 hours of collection, the tissues were
lyophilized for approximately 72 hours and were then placed in a freezer at -20 °C
where they remained until analyzed. Samples were ground to pass through a 40 mesh
screen and 100 mg used for extraction. Sugars were extracted by suspending the
tissue in 80% ethanol three times and then combining the three aliquots. After

removing sugars, the starch was digested using a—amylase and amyloglucosidase. The

65

tissue starch content was then assayed spectrophotometrically as described previously
(13).
Data Analysis
Data were analyzed with the MSTATC statistical package (MSTATC,
Michigan State University, East Lansing, MI) using a two-way Analysis of Variance
and orthogonal contrasts, or where appropriate, by regression analyses using
DeltaGraph (Delta Point Inc. , Monterey, CA).
RESULTS
leaf and Shoot Dry Weight
A positive relationship existed between leaf dry weight and shoot number
(p50.05) at harvest only (Figure 1a). leaf weight increased rapidly during the
spring growth flush, slowed for about 10 days around bloom and then increased until
veraison at roughly the same rate as before bloom. After veraison, leaf dry weight of
three- and six-shoot vines continued to increase while that of one-shoot vines
decreased slightly.

Shoot dry weight accumulation followed a pattern similar to that of leaves,
slowing slightly around bloom. There was an inverse, linear relationship between
shoot number and total shoot dry weight in dormant vines (y = 13.36x -0.80;
r2 = 0.98) only (Figure 1b).

leaf and shoot dry weight were combined to give "canopy dry weight” (Figure
1c). A positive relationship existed between canopy dry weight and shoot number on
the first sampling date and at harvest. The pattern of dry weight accumulation in the

vegetative tissues of the canopy resembles that described for many types of fruit; it

66
forms a roughly double-sigmoid shaped curve (11). The first increase occurred

immediately after bud burst, followed by a lag phase around bloom and a second
increase from bloom until veraison. After veraison, the rate of dry weight
accumulation in the canopy decreased in one-shoot vines but three- and six-shoot
vines contimred to accumulate dry matter at approximately the same rate as they had
from bloom through veraison. As vines entered dormancy, canopy dry weight
dropped precipitously due to loss of non-hardy vegetative tissues (i.e. leaves and the
non-lignified portion of shoots) after a freeze of -2 °C.

Root and Trunk Dry Weight

Trunk dry weight decreased during bud burst and through the spring growth
flush (the first 350 GDD) (Figure 2a). It then stabilized around bloom (about 400
GDD) before increasing. Trunk dry weight increased from bloom through harvest
for all treatments. The only exception was that three-shoot vine trunk weight changed
little between veraison and harvest. The period from harvest until the vines became
dormant found little change in trunk dry weight for any treatment.

Treatment did not affect root dry weight at any time (Figure 2b). Root weight
increased for all treatments from bloom through harvest. Root weight increased
slightly between harvest and dormancy in one-shoot vines but decreased in three- and
six-shoot vines during the same period.

Total Vine Dry Weight

There was a positive relationship (p S 0.10) between shoot number and vine

dry weight at harvest only (Figure 2d inset). Dry weight differences among

treatments were small relative to leaf area differences, however. No net dry matter

67
production occurred from bud burst through bloom (the first 400 GDD or 25 days

post-burst). After anthesis, vine dry weight increased through harvest and then
decreased going into dormancy as non-tardy tissues abscised.
Specific leaf and Shoot Weights

An inverse relationship existed between specific leaf weight (SLW) and shoot
number at similar leaf area (Figure 3a). SLW increased with leaf area for all
treatments from bud burst through harvest. At harvest (maximum LA in Figure 3a),
SLW was similar in all treatments.

Specific shoot weight (SSW) was inversely related to shoot number at similar
shoot length (Figure 3b). SSW increased in all treatments as the season progressed
(Figure 3b inset), but the magnitude of the difference among treatments was greater
late in the season due to a more rapid increase of SSW in one-shoot vines than in
three- and six-shoot vines (Figure 3b).

leaf area per gram shoot dry weight was positively related to shoot number
particularly after shoot weight exceeded about 2 grams (around bloom) (Figure 3c).
The difference was greatest from 5 mm berries through harvest (530 GDD to 1110
GDD).

Root Dry Weight cm’2 Leaf Area

Root dry weight per cm2 leaf are varied from bud burst through bloom (Figure
4). An inverse relationship existed between root dry weight per cm2 leaf and shoot
number at 220 GDD, at bloom and again at veraison (Figure 4). The initial root dry
weight per cm2 leaf area at bud burst was quite high due to the small amount of leaf

area, so it was omitted from Figure 4. As leaf area increased post-burst, root dry

68
weight changed little, resulting in decreasing root dry weight per unit leaf area. This

reached its lowest value at bloom and then increased slowly through harvest for all
treatments.
Weight Ratios of Canes (Vine Size) to Storage Organs

There was an inverse, linear relationship between the ratio of cane fresh
weight and the weights of perennial tissues, and the mrmber of shoots (Figure 5).
Differences in cane weight were responsible for the decreasing ratio of lignified, one-
year wood to perennial storage tissues as shoot number increased.

Starch Data

Tissue starch content showed few differences among treatments when the data
were expressed either as a concentration or as total starch weight (Appendix A).
Starch content of roots and trunks declimd as shoots began growth and did not begin
to increase until bloom. After bloom, starch concentration and total starch of all vine
organs increased through harvest. Shoot number had no influence on starch reserve
mobilization rate during the spring growth flush or on tissue contentration throughout
the growing season.

DISCUSSION

Vine capacity is defined by Winkler (28) as, " . . .the quantity of action with

respect to the total growth and total crop of which the vine is capable". To
paraphrase, it is a vines capacity for dry matter production under a given set of
environmental conditions. In this experiment, vines of similar fresh weight produced
similar quantities of dry matter regardless of canopy morphology. This suggests that

vine capacity is based on the quantity of reserves available to support the spring

69
growth flush, and the size ofthe root system to support the canopy. Since canopy

development is supported by reserves and reserves were similar among treatments at
the end of the experiment, it is likely that vine capacity was also similar among
treatments as vines entered dormancy.

It has been suggested that cane fresh weight is an estimate of leaf area and
vine capacity (4). Increasing the leaf area and/or storage tissue mass per gram shoot
weight (as occurred here with increasing shoot number) indicates an increase in vine
capacity per unit cane weight with increasing shoot numbers. This Observation is in
agreement with results from studies using mature vines and suggests the need to find
an alternative method for estimating vine capacity in MP vines.

Measurements of root dry weight during the spring growth flush showed no
change in any of the treatments from bud burst through bloom. Starch
determinations, however, showed a sharp drop in the tissues of all treatments while
observations of vine roots during destructive harvests indicated that the roots were
actively growing during this time. Thus, a large portion of root growth during the
spring growth flush is likely dependent upon the carbohydrate reserve pool available
in the roots themselves.

A loss of trunk weight was detected in all treatments as starch levels declined
with the onset of growth. A nearly equal amount of weight was found as new shoot
and leaf growth. Clearly, there is not a 100% conversion from storage into new
tissue and several studies have shown that basal leaves begin to export photosynthate
once the fifth leaf is beginning to expand, which would add to the dry weight of the

canopy (29,30). The data herein, however, provide evidence that trunk (above

70
ground) reserves of one-year-old vines are responsible for a large portion of canopy

growth during the spring flush. Koblet et al. (10) reported similar conclusions from
studies using mature vines. They found a positive correlation between the volume of
perennial, above ground tissue (i.e. trunks and cordons) and bud fruitfulness, total
and lateral leaf area, yield, cluster weight, berries per cluster and must soluble solids.
Since no differences were found among treatments in the present study from bud burst
through bloom in dry weight or starch content of roots or trunks, I conclude that the
numbers of vegetative sinks employed did not cause differences in the rate of
carbohydrate reserve mobilization or in the absolute quantity of carbohydrate reserves
utilized during the spring growth flush. In addition, the size of the canopy which can
be generated by reserves during the growth flush appears to be indicative of the vines
capacity. Further work is necessary to confirm this.

Three- and six-shoot vines had nearly identical root dry weight/unit leaf area
throughout the season but always less than one-shoot vines. The similarity between
values for three- and six-shoot vines suggests that available root mass may ultimately
limit canopy development becasue of a functional equilibrium between roots and tops
(6,18). This conclusion is supported by the fact that canopies of three- and six-shoot
vines were quite similar in their morphologies but differed from one-shoot vines (15).
The morphological changes closely resemble those associated with water stress e.g.
shorter shoots, smaller leaves and lower specific leaf and shoot weights (8,14,26) as
would be expected if water availability were limiting growth. Additionally, no further
decline in root weight/ leaf area occurred when shoot numbers were increased from

three to six. In fact, some shoots either failed to develop beyond a single leaf or

71

grew very slowly on six-shoot vines suggesting that availability of water, nitrogen,
cytokinins or some combination of these was limiting development.

Dry weight of whole vines was different only at harvest. leaf area differences
between one-shoot and three- or six-shoot vines were about 2x at bloom. This
difference, however, did not result in increased dry weight production during the
early growing season. Dry weight production is driven not by the supply of
photosynthetically produced sugars; rather, it is driven by sink activity (13,24,25). In
one-shoot vines where less leaf area had developed by the end of the spring growth
flush, the leaves had a higher SLW and were more effective at carbon assimilation
per unit leaf area (15). Photosynthetic compensation in leaves has been demonstrated
in Vitis (1,2) and Prunus (13) when leaf area is reduced relative to the carbohydrate
sinks present. Photosynthetic compensation occurs in response to the carbohydrate
source/ sink relationship. As carbohydrate sources (leaves) are removed, the supply of
photosynthate is reduced. Because the reduced supply is utilized more rapidly by the
sinks, there are fewer end products of photosynthesis (hexose phosphates) in leaf cells
to inhibit the rate of photosynthesis (12). It also possible that the increase in the
available transpiration stream to leaves as leaf surface decreases relative to root mass,
causes an increase in photosynthetic activity in leaves (7) concomitant with increasing
sink demand.

The strength of carbohydrate sinks was apparently the limiting factor for dry
matter accumulation in this study since vines with greater leaf area did not assimilate
greater amounts of carbohydrates between bud burst and veraison. By contrast,

between veraison and harvest continuing carbohydrate sink activity in three- and six-

72
shoot vines resulted in their contimring accumulatiOn of dry matter. The dry weight

of one-shoot vines changed very little during the same period. Sink strength is
def'md as the sink’s size times its activity (27) and this can be estimated by the rate
of dry weight accumulation (24). By this definition, all tissues of three- and six-shoot
vines continued as active carbohydrate sinks between veraison and harvest (with the
exception of roots in three-shoot vines). Organs of one-shoot vines were very weak
sinks during the same period. The cause of the continuing sink activity in three- and
six-shoot vines is not clear.

Generally, vine productivity will be determined by (a) the amount of leaf
canopy exposed to the sun; (b) the length of time the canopy is exposed; (c) the
temperature during this exposure; and (d) the amount of sunlight the canopy receives
during its exposure. The variable that is vine-dependent is the leaf surface area that
can be generated. The amount of canopy that will be produced by the vine is
dependent on (a) the quantity of reserves available to support the spring growth flush;
(b) the number of growing points able to utilize those reserves; and (c) the quantity of
roots available to support the canopy once it is developed. This listing is a great
simplification since it ignores many biotic and abiotic factors influencing plant
growth. It addresses however, the interrelationship between roots and canopy that
results in a relatively constant root to shoot ratio (6,11).

CONCLUSION

For small, potted vines without fruit, I conclude that: (a) the rate at which
reserves are utilized was not different with increasing numbers of vegetative sinks; (b)

dry weight accumulation was only slightly greater for vines with greater leaf area and

all

73

only between veraison and harvest; and (c) the ratio of mature cane fresh weight to
perennial tissues (trunk and roots) was less in six-shoot vines than in one-shoot vines,
supporting the observation that the use of pruning weights as an indicator of vine
capacity in MP vines must be reevaluated. Vine capacity is defmd by Winkler (28)
as "the quantity of action with respect to total growth. The term refers to a vine’s
ability for total production rather than to rate of activity”. Estimates of vine capacity
may be possible by measuring trunk diameter or leaf area per vine at the end of the
growth flush.

Developing a better understanding of the dynamics of grapevine canopy
development and dry weight accumulation should allow fine ttrning of vineyard
management programs to maximize yields on a sustainable basis. Displaying greater
leaf area early in the growing season does not necessarily lead to greater carbon

assimilation in young, potted vines, and competition between vegetative sinks for

available resources can alter canopy morphology and physiology.

74

LITERATURE CITED

1. Candolfi-Vasconcelos, M.C. and W. Koblet. Yield, fruit quality, bud fertility,
and starch reserves of the wood as a function of leaf removal in Vitis vinifera -
Evidence of compensation and stress recovering. Vitis 29:199-221 (1990).

2. Candolfi-Vasconcelos, M.C. and W. Koblet. Influence of partial defoliation
on gas exchange parameters and chlorophyll content of field-grown grapevines -
Mechanisms and limitations of the compensation capacity. Vitis 30:129-41 (1991).

3. Clingeleffer, P.R. Vine response to modified pruning practices. In:
Proceedings of the Second N .J . Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 20-30. Cornell University Press, Geneva (1993).

4. Clingeleffer, P.R. and LR. Krake. Responses of Cabernet Franc grapevines
to minimal pruning and virus infection. Am. J. Enol. Vitic. 43:31-7 (1992).

5. Downton, W.J.S. and W.J.R. Grant. Photosynthetic physiology of spur
pruned and minimal pruned grapevines. Aust. J. Plant Physiol. 19:309-16 (1992).

6. Geisler, D. and DC. Feree. Response of plants to root pruning. In:
Horticultural Reviews Vol. 6. J. Janick (Ed). Westport Publishing Inc. , Westport,
Connecticut. pp 155-88 (1984).

7. Flore, J.A. and A.N. Lakso. Environmental and physiological regulation of
photosynthesis in fruit crops. Hort. Reviews. 11:111-46 (1989).

8. Flore, J .A. Stone fruit. In: Environmental physiology of fruit crops. I.
Temperate crops. B. Schaffer and P.C. Andersen (Eds) CRC Press, Boca Raton,
FL. pp 233-70 (1994).

9. Johnson, DE. and GS Howell. Factors influencing critical temperatures of
primary buds on grape canes. J. Amer. Soc. Hort. Sci. 106:545-9 (1981).

10. Koblet, W., M.C. Candolfi-Vasconcelos, W. Zweifel, and GS Howell.
Influence of leaf removal, rootstock, and training system on yield and fruit
composition of Pinot Noir grapevines. Am. J. Enol. Vitic. 45:181-7 (1994).

11. Kramer, P.J. and T.T. Kozlowski. Physiology of Woody Plants. p 811
Academic Press, New York (1979).

75

12. Lakso, A.N . Viticultural and physiological parameters limiting yield. In:
Proceedings of the Second N .J . Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 9-14. Cornell University Press, Geneva, New York (1993).

13. Layne, D. Physiological responses of Prunus cerasus to whole plant source
manipulation. Ph.D. dissertation. Michigan State University, East Lansing, MI
(1992).

14. Liu, Z. and DJ. Dickmann. Responses of two hybrid Popular clones to
flooding, drought and nitrogen availability. 1. Morphology and growth. Can. J . Bot.
70:2265-70 (1992).

15. Miller, D.P., G.S. Howell and J.A. Flore. Effect of shoot number on potted
grapevines: I. Canopy morphology and development. Am. J. Enol. Vitic. 47:_
(accepted for publication 1996).

16. Mitchell, T.G. Vineyard mechanization and its impact on production costs in
the Taylor Wine Company vineyards. In: Proceedings of the Second N .J. Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), pp 66-8. Cornell
University Press, Geneva, New York (1993)

17. Pool, R.M., R.E. Dunst, D.C. Crowe, H. Hubbard, G.E. Howard and G.
Degolier. Predicting and controlling crop on machine or minimal pruned grapevines.
In: Proceedings of the Second NJ. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 31-45. Cornell University Press, Geneva, New York (1993).

18. Reynolds, A.G., R.M. Pool and LR. Mattick. Influence of cluster exposure
on fruit composition and wine quality of Seyval blanc grapes. Vitis 25:85-95 (1986).

19. Richards, D. The grape root system. In: Horticultural Reviews Vol. 5. J.
Janick (Ed) AVI Publishing Inc., Westport, Conmcticut. pp 127—68 (1983).

20. Shaulis, N. and R.E. Smart. Grapevine canopies: management, microclimate
and yield responses. 20th International Horticultural Congress, Warzawa. pp 255-65
(1974).

21. Smart, R.E. Climate, canopy microclimate, vine physiology and wine quality.
In: Proceedings of the International Symposium on Cool Climate Viticulture and
Enology. D.A. Heatherbell, P.B. Lombard, F.W. Bodyfelt and SF. Price (Eds), pp
1-18. Oregon State University Experiment Station Technical Publication N o. 7628
(1985).

22. Smart, R.E. Principles of grapevine canopy microclimate manipulation with
implications for yield and quality. A review. Am. J. Enol. Vitic. 36:230—9 (1985).

76

23. Sommer, K.J . and P.R. Clingeleffer. Comparison of leaf area development,
leaf physiology, berry maturation, juice quality, and fruit yield of minimal and cane
pruned Cabernet Sauvignon grapevines. In: Proceedings of the Second N.J. Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), pp 14-9. Cornell
University Press, Geneva, New York (1993).

24. Sung, S.S., W.J. Sheih, D.R. Geiger and CC. Black. Growth,sucrose
synthase, and invertase activities of developing Phaseolus vulgaris L. fruits. Plant,
Cell and Environ. 17:419-426 (1994).

25. Wareing, PF and J. Patrick. Source-sink relations and the partition of
assimilates in the plant. In: Photosynthesis and Productivity in Different
Environments. J .P. Cooper (Ed) Cambridge University Press, Cambridge, UK. pp
481-499 (1975).

26. Williams, L.E., N.K. Dokoozlian and R. Wample. Grape. In: Handbook of
Environmental Physiology of Fruit Crops. I. Temperate Crops. B. Schaffer and
P.C. Andersen (Eds) CRC Press, Boca Raton, FL. pp 85-133 (1994).

27. Wilson, J. Warren. Control of crop processes. In: Crop Processes in
Controlled Environments (A.R. Rees, K.E. Cockshull, D.W. Hand and R.G. Hurd
(Eds) Academic Press, New York, NY. pp 7-30 (1972).

28. Winkler, A.J., J.A. Cook, W.M. Kliewer and LA. Lider. General
Viticulture. University of California Press, Berkley, CA. p 710 (1974).

29. Yang, Y.S. and Hori, Y. Studies on the retranslocation of accumulated
assimilates in ’Delaware’ grapevines. III. Early growth of new shoots as dependent
on accumulated and current year reserves. Tohoku J. Agric. Res. 31:120-9 (1980).

30. Yang, Y.S., Y. Hori and R. Ogata. Studies of retranslocation of accumulated
assimilates in ’Delaware’ grapevines. II. Retranslocation of assimilates accumulated
during the previous growing season. Tohoku J. Agric. Res. 31:109-19 (1980).

77

 

 

 

 

   

 

 

 

 

 

 

 

25
I A Leaves . harvest
201 veraison
8 15‘:
a .
.3 10-
2 1 (I) shoot
5.; 3 (O) shoots
Z 6 (A) shoots
0 1 l 4 l r l r l M l r l ’

 

Dry weight (g)

 

 

 

Leaves + Shoots

 

 

 

 

 

 

 

 

O
_i

r I r r r I f I ‘ ' I I

0 200 400 600 800 1000 1200
Growing Degree Days (base 10 C)

Figurel. Dry weight (g) of A) leaves; B) shoots; and C) shoots and leaves combined of potted
Chambourcin grapevines with 1(I), 3(O) or 6(A) shoots. Bars represent the LSD at p = 0.05.

Dry weight (g)

Whole vines

 

 

78

 

 

 

 

 

5mm berries

10 l l 1 l l l J. l I l 1 l I I 1 l l 1 l i L 4 J l L l 4

 

 

 

 

 

 

C Whole vines

 

 

 
 
   
 

 

 

 

 

 

 

 

 

 

30: 1(I) shoot
60-2‘ 3 (O) shoots
; 6 (A) shoots
40 -}
20% V o 1 2 3 4 5 6
1 Shoot #
O ‘3' I 7 I T I I r T l I l r I I ‘C Ifi ' I 1' 1 I j j T
o 200 400 600 800 1000 1200 1400

Growing Degree Days (base 10 C)

Figure 2. Dry weight (g) of A) trunks; B) roots, and; C) whole Chambourcin
grapevines with 1(I), 3(0), or 6(A) shoots. Inset in ”C" shows the relationship
between whole vine dry weight (g) and shoot number at harvest (y = 82.85 (x"0. 1303)

r2 = 0.2724. p=o. 10).

79

 

>1
r r I

as

 

   
 

 

 

 

 

 

Specific leaf weight (g cm'z) x 103
wuvhmm‘LFOvrxlucn

4. - l (I) shoot
._ 3 (0) shoots
3. - [Ki 6 (A) shoots
' ’ ‘ ‘ l ‘ ' T r I T f ‘ r I ‘ ‘ ‘ ‘ | ' ' ' ‘ l ' ‘ ‘ T I ' ' fl
0 500 1000 1500 2000 2500 3000 3500
GDD (base 10C)

 

0.1

 

fic shoot weight (g cm )
.o .o .o
.9 :3 $°°

 

 

 

 

o 0.02-
D 4
q 4
W n 1

 

 

 

‘ ' ' ‘ ' ' ‘ ‘ ' ‘ l ‘ ' l ‘ ‘ ' | ‘ ‘ ' l ‘ ' r l ' ‘ ‘ l ‘ ‘
0 20 40 60 80 100 120 140 160 180 200
Total shoot length (cm)

 

 

 

 

0 2 4 6 8 10 12 I4
Shoot dry weight (g)
Figure 3. Relationship between A) leaf area and specific leaf weight; B) shoot length and specific shoot

weight; and C) leaf area and shoot dry mass for Chambourcin grapevines with 1(I), 3(0) or 6(A) shoots.
Inset in 'B" shows change in specific shoot weight over the growing season.

8O

 

 

 

0.035

g 0.03d

3 0.025 -
‘fi

5 0 02 _ veraison harvest
E ‘ bl

“' _‘ oom

i) 0.015 I / I

‘3’ :

-u - I /

§ 0.005 — 5 mm berries

°‘ :

0 ' . I r I I I I . I . I . I
100 300 500 900 1100
Growing Degree Days (base 10 C)

Figure 4. The relationship between root dry weight (g) and leaf area (cm2) of
potted Chambourcin grapevines with l (I), 3 (O) or 6 (A) shoots. Bars
represent the LSD at p = 0.05. -

 

81‘

 

 

 

 

 

 

I I shoot I] 3 shoots :25: 6 shoots
0.81
J __
0° ‘
‘3 0.6d

0.4 -

0.2 4

 

.—

————_—.
_—_—.

_—.___—_._.

——
—_
_—
-——_—_
.—
——_—_
—_
—__._.____
—_
————_
W

W
——
———_—.
—.———
—_
——
—_
—————_—
——_————.—
_—
—-—————_—
__
——————_—
———_———.
——
——.—————
——
——
__———-
—____—_
—_
—_——-—
W
~.—.—
——
.—————-
——————-
.—_____
_—.
_—
——-—-———
_—
——

__
_—
——
—_
##—
.———--.———

,lHI!iIllllllllllllllllllllltlllllllllllll

Ii!HHHIIIIIHIIIEHHH

 

 

 

canes/trunks canes/roots canes/trunlrs-t-roots

Figure 5. Relationship between cane fresh weight in grams (vine size) and the dry
weight (g) of trunks, roots, or trunks + roots (total storage), of Chambourcin
grapevines with l-, 3- or 6-shoots. Bars represent the LSD value at p 8 0.05.

82
IV. INFLUENCE OF SHOOT NUMBER AND CROP LOAD ON POTTED

CHAMBOURCIN GRAPEVINES. I: MORPHOLOGY AND DRY

MATTER PARTITIONING

ABSTRACT

Two-year-old Chambourcin grapevines were grown in 19-liter pots with the
following treatments: one- or four-shoots and no clusters (1/0 and 4/0 respectively);
one-shoot and one-cluster (1/1), and; four-shoots with one (4/1), two (4/2), three
(4/3) or four (4/4) clusters. Four-shoot vines had greater leaf area, shoot length and
leaf numbers per vine but l-shoot vines had longer shoots, larger leaves, and greater
leaf area and leaf number per shoot. Crop load effects on canopy morphology were
relatively small. Berry number per cluster, berry weight and fruit soluble solids were
not different among treatments but 4/2, 4/3, and 4/4 vines had two to three times
greater fruit fresh weight than did U] and 4/1 vines. Whole vine dry weight was
never different among treatments, but there was a positive linear relationship between
berry number and vine dry weight at harvest. More dry weight was partitioned to the
fruit at the expense of roots, shoots and leaves in cropped vines vs. non-cropped
vines. Dry weight differences of vegetative organs were small among crop load
treatments. The combination of differences in individual organ weights, when
partitioned to fruit rather than to vegetative tissues, resulted in increased in fruit dry
weight with increasing berry numbers. Since fruit is approximately 75 % H20 by
weight at harvest, small differences in dry weight result in large increases in yield.
These data indicate that: (a) vegetative sinks have a greater impact than fruit on
canopy morphology; and (b) carbohydrates used in fruit production are derived

primarily from greater partitioning to fruit at the expense of vegetative tissues, and to

83

a lesser degree, greater dry matter production between veraison and harvest in vines
with increasing fruiting sink strength.

INTRODUCTION

Reducing the cost of dormant pruning is very important as competition
increases in global grape and wine markets (16). Researchers have shown that the
use of mechanical or ”minimal" pruning (MP) has resulted in greater yields than
traditionally pruned controls (6,8,18,20). Winkler demonstrated that controling crop
load on unpruned vines by removing clusters gave higher yields and fruit quality than
did crop control by traditional, severe pruning, but was uneconomical (25,26). Thus,
crop control by dormant pruning has been the method of choice due to economic
considerations. Research conducted in cool climates has supported Winkler’s
conclusions (18,26), but recent investigations into crop thinning on mechanically
pruned vines have focused on the use of mechanized thinning (6,7,8,12,18,20). If
perfected, mechanized thinning could allow producers to maximize yield and fruit
quality per unit land area on a sustainable basis.

To thin to the desired level, it is essential to first have an estimate of: (a) the
vines’ cropping potential or "capacity" (defined by Winkler (18) as " . .the quantity of
action with respect to the total growth and total crop of which the vine is capable");
and (b) the amount of fruit that is on the vine before thinning. Partridge suggested
that a vine’s crop be "balanced" with its capacity (17). Shaulis (19) followed this
suggestion with a formula that increased the number of buds (and thereby crop) as the

amount of mature, one-year old canes (and presumably capacity) increased.

84
It has been suggested that MP vines produce yields as much as two times

greater than traditionally pruned vines because the capacity of MP vines is greater
(6,8,12,20). Rapid canopy development by MP vines during the spring growth flush
is thought to cause greater annual dry matter production (6,12). However, while
some research has shown large, season-long differences in leaf area between spur and
MP vines (20), other research showed that leaf area differences disappear by mid-
season and spur vines actually had greater leaf area by harvest (8). In addition, when
canopy dry weight was determined (including vegetative and reproductive growth),
there was no difference among treatments. These data suggest that the greater yields
of minimally prumd vines may be due to greater carbohydrate partitioning to fruit at
the expense of vegetative tissues as opposed to increased vine capacity. The
physiological basis for higher yields of minimally pruned vines remains unclear.

The purpose of this experiment was to: (a) study carbohydrate assimilation and
partitioning in vines with differing canopy structure and crop load; (b) develop a
better understanding of how changing carbohydrate source/ sink relationships affect
vine capacity; and (c) determine the physiological difference between severely and
lightly pruned vines in terms of intravine carbohydrate relations. Specifically, the
following were addressed: (1) which sink (vegetative or reproductive) has the greatest
effect on canopy morphology; and (2) what is the source of carbohydrate used to

sustain additional fruit as crop load is increased?

85
MATERIALS AND METHODS

Plant Material

Two-year old Chambourcin (J .8. 26-205) grapevines grafted to 5-C rootstock
were planted in 19-liter plastic pots with a 45% sand, 45% loam and 10% peat sterile
potting mix on May 11, 1994. Potted vines were placed on pea-gravel in full sun and
watered regularly. Fertilizer was applied as a balanced N ,P,K solution once per
month. Pesticides were applied as necessary.

When buds were at the swell-two stage (10) of development (elongated sphere
prior to burst), their numbers were adjusted to give either one or four buds which
would be allowed to develop. As the vines grew, all laterals were removed once per
week. Flower cluster numbers were adjusted about one week before anthesis to give
the following treatments: one- or four-shoots with zero clusters (1/0 and 4/0,
respectively); one-shoot with one-cluster (III); or four-shoots with one, two, three or
four clusters (4/1, 4/2, 4/3 and 4/4, respectively) (Table 1).

Vines were blocked according to their fresh weight prior to planting,
producing four blocks. Treatments were randomly assigned to five vines for each
treatment in each block; one vine for each treatment-block to be used at each
destructive harvest. At various intervals (described below), vines were selected for
destructive harvest. The experimental design was a randomized complete block with
seven treatments, four replicates and five partitioning dates for a total of 140 vines.

Vine Dry Weight
Vines were destructively harvested at five phenological stages: (1) pre-bloom

(about five days before any flowers opened); (2) post-anthesis (S-mm berry diameter);

86
(3) veraison (30% of berries showing coloration); (4) harvest; and (5) dormant (all

leaves abscised). Shoot length, leaf number and dry weight were determined at each
destructive harvest. Dry weights were determined by partitioning the vine into its
various organs and recording the fresh weight of each. Tissues were then placed into
paper bags in a drying oven at 60°C until no further weight reduction occurred (about
four days; seven to ten days for fruit). After drying, tissue weights were recorded
and percentage water content calculated.
Leaf Area
Leaf area was determined using a Li-Cor LI-3000 portable leaf area meter
(Lambda Instrument Corp. , Lincoln, Nebraska) at each destructive harvest date.
Fruit Chemistry
Ten-berry samples, collected from vines partitioned at harvest, were weighed
and placed in sealed plastic bags at -20°C until analyzed. Berries were crushed and
the juice strained through cheese cloth in preparation for analysis. Sugar content,
expressed as °Brix, was determined with a bench top, temperature compensating
refractometer, and titratable acidity and pH were determined using previously
described methods (2).
Data Analysis
Data were analyzed with the MSTATC statistical package (MSTATC,
Michigan State University, East Lansing, MI) using a two-way Analysis of Variance
and orthogonal contrasts and, where appropriate, by regression analyses using

DeltaGraph (Delta Point Inc. , Monterey, CA).

87
RESULTS AND DISCUSSION

Canopy Morphology

The number of shoots on vines had the greatest influence on whole vine leaf
area until veraison (Figure 1a.). Four-shoot vines had 200% more leaf area than one—
shoot vines pre-bloom. At that time, 4/0, 4/1 and 4/2 vines had leaf area
intermediate to 1/0 and 1/1, and 4/3 and 4/4 vines. No leaf area differences existed
at 5mm berry diameter. At veraison, 1/1 and 1/0 vines had the least and four-shoot
vines the greatest leaf area. The only exception was 4/ 3 vines which had leaf area
intermediate to the remaining four-shoot and one-shoot treatments. Leaf area
increased between veraison and harvest in non-fruited and l/ 1 vines only. Leaf area
and shoot length were shown to be closely related (14) and this was true in the
present study. Leaf area per shoot (Figure lb) and shoot length per shoot (Figure
2b) were always greatest on one-shoot vines, and each increased faster on one-shoot
vines throughout the growing season as compared to four-shoot vines. Crop load did
not effect leaf area per shoot or shoot length per shoot at any date. Leaf area per
vine (Figure 1a) and shoot length per vine (Figure 2a) were related. Shoot length
per vine was effected both by shoot number and crop load from anthesis through leaf
abscission. Pre-bloom and at 5mm berries, treatments were grouped by shoot number
with one-shoot vines having the least and four shoot vines the greatest shoot length
per vine (Figure 4a). By veraison, crop load had caused a reduction in the rate of
shoot elongation of 4/ 3 and 4/4 vines so they had shoot length per vine intermediate
to one-shoot vines and 4/0, 4/1 and 4/2 vines. Shoot growth stopped after veraison

in all cropped treatments but continued in non-cropped vines. At harvest, 4/0 vines

88
had the greatest shoot length per vine and 1/1 vines the least. The remaining

treatments (1/0, 4/1, 4/2, 4/3 and 4/4) were intermediate.

Leaf size was always greater in one-shoot vines (Figure 1c). Crop load had no
effect on leaf size in either one- or four-shooted vines. Four-shoot vines had a
greater number of leaves per vine, but fewer leaves per shoot than one-shoot vines
(Figures 3a and 3b, respectively). Increasing the crop load caused 43 and 4/4 vines
to have lower leaf numbers than 4/0 and 4/1 vines at veraison and harvest.

Canopy morphology is clearly affected more by competing vegetative sinks
than by competition from reproductive sinks from bud burst through veraison.
Similar observations have been made in minimally pruned grapevines in the field
(6,7,8). However, the relative effects of vegetative and reproductive sinks on
canopy morphology at different phenological stages have not been clear from past
studies. The data presented here demonstrate that shorter shoots and smaller, thinner
(data not shown) leaves are the result of competing vegetative sinks. It is the
presence of many vegetative sinks (shoot tips and expanding leaf blades) that produce
the rapid canopy deployment and morphology characteristic of minimally pruned vines
(12,20)

Dry Weight Partitioning

One-shoot vines had lower leaf dry weights at veraison only (Figure 4a). At
veraison, the higher crop load of 4/3 and 4/4 vines caused them to have leaf dry
weight intermediate between 1/0 and Ill vines and 4/0, 4/1 and 4/2 vines. Between
veraison and harvest, leaf dry weight declined in all vines with fruit, possibly due to a

retranslocation of carbohydrates to ripening fruit. Leaf dry weight increased in non—

89
cropped vines during the same interval, however, but at a slower rate than the period

from bud burst through veraison suggesting that the relative sink strengths of leaves
and storage tissues had changed. At harvest, 4/0 vines had the greatest leaf dry
weight, 1/0 vines were intermediate and all other treatments were similar with the
least amount of leaf dry weight.

Shoot dry weight increased from pre-bloom through veraison, but was similar
in all treatments (Figure 4b). Treatment had no effect on shoot dry weight until
veraison. At harvest, 1/1 vines had the greatest, 4/0 and 1/1 vines intermediate and
4/1, 4/2 and 4/3 vines the least shoot weight. By contrast, in dormant vines, 1/0, 1/ l
and 4/0 vines had the greatest shoot weights. Even though heat accumulation was
low, the post-harvest period was a time of rapid increase in shoot dry weight. The
percentage of lignified nodes also increased during this time in all treatments (data not
shown). The percentage of lignified nodes of 1/ l vines increased the most (50.8% to
87.75%) and of 4/4 vines the least (44.5% to 57.7%) between harvest and leaf fall.

Shoot dry weight decreased rapidly between veraison and harvest in four-shoot
vines with crop. The observed change may be due to a retranslocation of
carbohydrates from shoots to fruit during fruit loading (5,14). Differences in dry
weight loss from shoots of fruiting one-and four-shoot vines may be due to differences
in shoot structure. Specific shoot weights were always greater in one-shoot vines
indicating a greater amount of structural tissue (data not shown). Since shoots of
four-shoot vines contained less structural tissue, a greater percentage of the total dry

weight may have been available for retranslocation as non-structural carbohydrates.

90
Fruit dry weight was not different among treatmems until harvest (Figure 4c).

However, the rate of carbon allocation to fruit was greater in vines with higher crop
loads from bloom through harvest reflecting the greater sink strength represented by
higher crop loads. At harvest, fruit dry weight was greatest in 4/2, 4/3, and 4/4
vines and least in 1/1 vines. Dry weight accumulation by fruit of 4/2, 4/3 and 4/4
vines occurred at a much higher rate between veraison and harvest as compared to
fruit of 1/1 and 4/1 vines.

Root dry weights were similar for all treatments from bud burst until veraison
(Figure 5a). Root dry weights were greater for non-fruiting vines at harvest and in
dormancy only. Vines with a high crop load (4/3 and 4/4) and 1/1 vines had the least
root dry weight in dormancy in contrast to NO, 4/0 and 4/1 which had the greatest.
Root weight was nearly static between veraison and harvest in cropped vines
indicating that the strength of roots as a carbohydrate sink had virtually ceased while
fruit was ripening. By contrast, roots of non-cropped vines accumulated dry weight
between veraison and harvest faster than any other organ.

Trunk dry weight was similar among treatments until veraison (Figure 5b). At
veraison, trunk weight was least in 4/0 vines and greatest in 4/4 vines. All other
treatments were intermediate and their was no relationship between crop load or shoot
number and trunk dry weight. Trunk dry weights declined slightly on all fnrit-
bearing vines between veraison and harvest. These data again indicate a strong
possibility that carbohydrates were retranslocated from trunks as well as shoots and

leaves to promote fruit maturation. The post-harvest period was again marked by an

91

increase root and trunk dry weights, demonstrating the importance of even short
recovery periods following harvest for the replenishment of storage reserves.

The dry weight of current-season canopy tissues was nearly identical for non-
cropped one- and four-shoot vines (Figure 6a). Carbohydrates were allocated
differently however, so that four-shoot vines had greater leaf weight and one-shoot
vines had greater shoot weight at veraison (F igurcs 4a and 4b). Canopy dry weight
of 4/ 3 vines was greater than non-fruiting vines at both veraison and harvest due to
the weight of fruit. The 1/1, 4/1, 4/2 and 4/4 vine canopy weights were intermediate
between 4/3 and 1/0 and 4/0 vines at veraison. By contrast, at harvest, canopy dry
weights of 4/2, 4/3 and 4/4 vines were greatest, 1/1 and 4/1 vines intermediate, and
non-fruited vines least. Trunk + root weights were similar in all treatments until
harvest when non-fruited vines had more storage mass (Figure 6b). The ratio of root
dry weight to shoot + leaf dry weight was not different among treatments at any time
(data not shown).

Differences in canopy dry weights account for most of the dry weight
difference among crop-bearing treatments. A comparison of vine organ dry weights
among treatments for evidence of differential carbon partitioning to fruit is shown in
Table 2. The presence of fruiting sinks caused a large amount of the total vine dry
weight (approximately 25 % depending on crop load) to be partitiomd to fruit at the
expense of vegetative tissues (In - 1/0 and 4/1 - 4/0 comparison). The roots were
most affected by reallocation of carbohydrates to the fruit. The addition of increasing
mrmbers of berries (fruiting sinks) caused small additional amounts of dry matter

partitioning to the fruit (4/4-4/1; 4/34/1; 4/2-4/1 comparisons). There was evidence

92
that vines with larger fruiting sinks assimilated as much as 10% additional

carbohydrate over the growing season relative to non-cropped controls. Remarkably,
there was no difference in the weight of whole, dormant vines suggesting similar vine
capacity during the following season. However, root weight of l/ l , 4/3 and 4/4 vines
was less than 1/0, 4/0 and 4/1 vines and 4/2 vines were intermediate. It is likely that
a reduction in root mass would have detrimental effect on the following seasons vine
capacity (26,27), but it is not clear from these data if a mature vine would maintain
the same capacity as in the current growing season. The root mass of vines in all
treatments increased during the course of this experiment. In an established vineyard
the goal would be to simply reutrn to the same status that existed at the beginning of
the growing season, assuming that condition was acceptable.

Whole vine dry weight differed among treatments at veraison only (Figure 6c).
At that time, 4/1, 4/2, 4/3 and 4/4 vines had greater dry weight than 1/0 and 4/0
vines, and 1/1 vines were intermediate. Vine dry weight was linearly related to berry
number in fruiting vines at harvest (y=0.52x + 9.37, r=.691. Figure 6c inset).
These data indicate that greater reproductive sink strength caused greater carbon
assimilation, and the additional carbon was responsible for a portion of the increased
yield of 4/2 and 4/3 vines. When vine dry weight was regressed against leaf area
(Figure 7), 4/3 vines showed a higher rate of assimilation per unit leaf area than 4/1
vines (.065 g cm‘2 and .045 g cm'z, respectively) which would be expected with a
decreasing carbohydrate source/sink ratio (8,22). Unlike earlier work (15), the
presence of more leaf area at bloom in 4/0 vines did not result in greater seasonal

carbon assimilation than in 1/0 vines. The 4/0 vines had an average of 5% more dry

93
weight at harvest than 1/0 vines. The reason for the discrepancy between these and

earlier data is not known. It may be due to variation between seasons and/or vines.

Yield

Components of yield data appear in Table 3. Fruit yields were greater in 4/ 2
and 4/3 vines. The 1/1 and 4/1 vines had similar, low yields and 4/4 vines were
intermediate. The 4/2 and 4/3 vines had 2.4 and 2.9 times greater yield
(respectively) than 1/1 vines. Yield differences were due to cluster and berry
number. Treatment did not effect berry weight but there was an inverse, linear
relationship between cluster mrmber and berries per cluster in four-shoot vines (y = -
5 .92x + 48.60;
r = .941). Cluster weight was greatest in 4/1, 4/2 and 4/3 vines, intermediate in 1/1
vines, and least in 4/4 vines. The difference in cluster weights is the result of
varying numbers of berries per cluster. The lower mrmber of berries per cluster
observed in four-shoot vines with increasing cluster numbers may be caused by one,
or a combination of two factors. First, less leaf area (and carbohydrate) per cluster
available at bloom (data not shown) results in a lower percentage of flowers that will
set fruit (4). Second, as competition among vegetative sinks increases, cluster length
and flower number per cluster decrease (15). Calculations showed that the leaf area
per flower on 4/1 vines was the highest of any treatment (Appendix C) because of
pre-bloom flower cluster thinning, and these vines had the highest percentage fruit
set. By contrast, 4/4 vines had the least leaf area per flower and the lowest

percentage fruit set. .

94

Total soluble solids, pH and total acidity were not different among treatments
(Table 4). Total sugar accumulation, however, was much greater in the fruit of 4/2,
4/3 and 4/4 vines by comparison with fruit of 1/1 and 4/1 vines (Figure 8).

Crop load (weight of fruit/weight of dormant cane prunings) is considered to
be an effective indicator of the carbohydrate source/reproductive sink relationship in
grapevines (3). Because leaves are borne on canes, greater cane weight is thought to
equal more leaves and a larger canopy. The efficacy of this approach has recently
been questioned (6). Crop load calculated for the various treatments appears in Table
5. The 1/1 vines had the lowest crop load and 4/3 vines the greatest. The observed
range of crop load would indicate that 4/3 vines were overcropped and 1/1 and 4/1
vines undercropped. Yet fruit quality was not different among treatments (Table 4).
A careful examination however, indicates that there is a difference between the
highest and lowest crop loads in the quantity of root tissue. This indicates that there
may be an effect of high crop loads resulting in a reduced capacity for canopy
development and growth the following season.

Leafarea per gram fruit fresh weight was greater in 1/1 and 4/1 vines than in
the remaining treatments which were similar (Table 5). However, even the 4/ 3 vines
with the highest crop load had over 15 cm2 of leaf area per gram fruit and this is
considered more than adequate (11,25). These data support the suggestion that cane
pruning weight (vine size) does not have the same meaning in a vine system where
vegetative competition leads to short shoots with low specific weights (6,7,15 ,20).
The higher leaf area per gram shoot weight found under these circumstances (15)

coupled with the higher yields associated with this type of vine system (6.8.18) lead

95
to crop load estimates that are not indicative of the true carbohydrate

source:reproductive sink relationship. Crop load assessments, therefore, must be
based on actual leaf area per unit fruit weight measurements.
Carbohydrate Source/Sink Relationships

Increasing shoot numbers caused an alteration of canopy morphology in four-
shoot vines, but it is not clear from the data presented how this occurs. However,
shorter shoots and reduced specific leaf weight are characteristic responses to water
stress (13,24). More research is necessary to determine if the size of the root or
xylem systems ultimately limit water supply, whether the supply of growth regulators
is limiting, or if some combination of the two cause the observed changes in wow
morphology. On a whole vine scale, the additional buds allow for early canopy
development as observed earlier (6,8, 12,25). By bloom, four-shoot vines had nearly
twice the leaf area of one-shoot vines, although this difference was nearly gone by
veraison. An additional benefit of retaining more buds is the production of more
flower clusters which give the vine the potential to set more fruit.

In the absence of fruit or with a small number of berries, a vine’s carbon
assimilation appears to be sink limited. In this situation, end-product inhibition of
photosynthesis occurs when sugars are not utilized as rapidly as they are synthesized
in the leaf (9,23). If that condition continues, there is a down-regulation of
production of photosynthetically active proteins, the net result being a decrease in
photosynthetic efficiency per unit leaf area (1,21). The addition of more fruiting
sinks within the range used in this study resulted in greater total carbon assimilation

and a greater portion of the total carbohydrate being budgeted to fruit at no cost to the

96
perennial parts of the vine (i.e. tissues not lost to frost or pruning) as compared to

vines with lower crop loads. In other words, yield was brought into balance with the
vines capacity. By contrast, a comparison of fruiting and non-fruiting vines shows
that the presence of fruit results in less carbon allocation to vegetative tissues,
especially roots, after veraison. Root mass increased in low crop-load vines between
harvest and leaf fall but not in high crop—load or 1/1 vines. More research is
necessary to determine the long-term effects of this phenomeno.

Sink strength can be estimated by the rate of dry weight accumulation in a
given organ (22). Root weight increased at the highest rate between veraison and
harvest on non-fruiting vines, so roots are the strongest carbohydrate sink during this
period in the abscence of fruit. When fruit is present, it becomes the strongest
carbohydrate sink between veraison and harvest. The results of the present study
suggest that a benefit of minimal pruning in field vines is that fruit production is in
closer balance with the vines capacity, and the vines are neither sink limited nor
source limited. Pool (18) suggested that crop load could be adjusted on minimally
pruned field vines after danger of spring frost and after an assessment of bud
fruitfulness to more fully utilize vine capacity. It appears that within limits, small
amounts of additional carbon allocated to fruit or assimilated due to the presence of
fruit translate into large additional yields of fresh fruit. This is due to the fact that
fruit is nearly 75% water at harvest when fully ripe (21°Brix in this study). For each

gram of carbon allocated to fruit, there is a return of about four grams of fresh fruit.

97
CONCLUSION

Retaining large numbers of buds at pruning insures that the maximum amount
of leaf area (i.e. carbohydrate sources) is expressed at the earliest possible time. This
large source is then available to supply a strong fruiting sink while at the same time
maintaining the vines vegetative structure. The large number of shoots resulting from
light pruning produce many flower clusters which usually produce sufficient crop so
that it can be balanced with the vines capacity. Yet it is obvious that vines can be
overcropped. So we must develop methods to determine when sources and sinks are
in balance at a time sufficiently early during the growing season to allow adjustments
to be made.

Data presented in this and previous chapters support the hypothesis that the
quantity of leaf area that a lightly-pruned vine can generate during the spring growth
flush is indicative of that vine’s relative capacity for dry matter production under a
given set of environmental conditions. More research is necessary to determine how
the genotype of scion and rootstock interacting under varying environmental
conditions will affect vine capacity as determimd by the canopy size at the end of the

growth flush.

98

LITERATURE CITED

1. Allen, J .F. Protein phosphorylation in regulation of photosynthesis. Biochem.
Biophys. Acta 1098:275-335 (1992).

2. Amerine, M.A. and CS. Ough. Methods for analysis of musts and wines.
John Wiley and Sons, Inc., New York. pp 377. (1988).

3. Bravdo, B., Y. Hepner, C. Loinger, S. Cohen, and H. Tabacman. Effect of
irrigation and crop level on growth, yields and wine quality of Cabernet sauvignon.
Am. J. Enol. Vitic. 36:132-9 (1985).

4. Candolfi-Vasconcelos, M.C. and W. Koblet. Yield, fruit quality, bud fertility,
and starch reserves of the wood as a function of leaf removal in ng's mm -
Evidence of compensation and stress recovering. Vitis 29:199-221 (1990).

5. Candolfi-Vasconcelos, M.C. , M.P. Candolfi, and W. Koblet. Retranslocation
of carbon reserves from the woody storage tissues into the fruit as a response to
defoliation stress during the ripening period in Vitis Men L. Planta 192:567-73
(1993).

6. Clingeleffer, P.R. Vine response to modified pruning practices. In:
Proceedings of the Second N.J. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 20-30. Cornell University Press, Geneva, New York (1993).

7. Clingeleffer, P.R. and LR. Krake. Responses of Cabernet Franc grapevines
to minimal pruning and virus infection. Am. J. Enol. Vitic. 43:31-7 (1992).

8. Downton, W.J.S. and W.J.R. Grant. Photosynthetic physiology of spur
pruned and minimal prumd grapevines. Aust. J. Plant Physiol. 19:309-16 (1992).

9. Flore, J .A. and A.N. Lakso. Environmental and physiological regulation of
photosynthesis in fruit crops. Horticultural Reviews. 11:111-46 (1989).

10. Johnson, DE. and GS. Howell. Factors influencing critical temperatures of
primary buds on grape canes. J. Amer. Soc. Hort. Sci. 106:545-9 (1981).

11. Kliewer, W.M. and A.J. Antcliff. Influence of defoliation, leaf darkening,
and cluster shading on the growth and composition of Sultana grapes. Am. J. Enol.
and Vitic. 21:26-36 (1970).

99

12. Lakso, A.N. Viticultural and physiological parameters limiting yield. In:
Proceedings of the Second N.J. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), pp 9-14. Cornell University Press, Geneva, New York (1993).

13. Liu, Z. and DJ. Dickrnann. Responses of two hybrid mtg clones to
flooding, drought and nitrogen availability. 1. Morphology and growth. Canadian
Journal of Botany. 70:2265-70 (1992).

14. Mansfield, T.K. and 6.8. Howell. Response of soluble solids accumulation,
fruitfulness, cold resistance, and onset of bud growth to differential defoliation stress
at veraison in Concord grapevines. Am. J. Enol. and Vitic. 32:200-5 (1981).

15. Miller, D.P. and 6.8. Howell. Impact of shoot number on potted grapevines.
I. Canopy development and morphology. Am. J. Enol. Vitic. (In press, 1995).

16. Mitchell, T.G. Vineyard mechanization and its impact on production costs in
the Taylor Wine Company vineyards. In: Proceedings of the Second N .J. Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), Cornell University Press,
Geneva, New York pp 66-8 (1993).

17. Partridge, N.L. The use of the growth-yield relationship in field trials with
grapes. Proc. Am. Soc. Hort. Sci. 23:131-4 (1926).

18. Pool, R.M., R.E. Dunst, D.C. Crowe, H. Hubbard, G.E. Howard and G.
Degolier. Predicting and controlling crop on machine or minimal pruned grapevines.
In: Proceedings of the Second N.J. Shaulis Grape Symposium, Fredonia, New York.
R.M. Pool (Ed), Cornell University Press, Geneva, New York, pp 31-45 (1993).

19. Shaulis, N. and R.E. Smart. Grapevine canopies: management, microclimate
and yield responses. 20th International Horticultural Congress, Warzawa, pp 255-65
( 1974).

20. Sommer, K.J. and P.R. Clingeleffer. Comparison of leaf area development,
leaf physiology, berry maturation, juice quality, and fruit yield of minimal and cane
pruned Cabernet sauvignon grapevines. In: Proceedings of the Second N.J. Shaulis
Grape Symposium, Fredonia, New York. R.M. Pool (Ed), Cornell University Press,
Geneva, New York, pp 14-9 (1993).

21. Stitt, M. and D. Schulze. Does Rubisco control the rate of photosynthesis and
plant growth? An excercise in molecular ecophysiology. Plant, Cell and Eviron.
17:465-87 (1994).

22. Sung, S.S., W.J. Sheih, D.R. Geiger and CC. Black. Growth,sucrose
synthase, and invertase activities of developing Phaseolus vulgaris L. fnrits. Plant,
Cell and Environ. 17:419—26 (1994).

100

23. Wareing, RF. and J. Patrick. Source—sink relations and the partition of
assimilates in the plant. In: Photosynthesis and Productivity in Different
Environments. J .P. Cooper (Ed) Cambridge University Press, Cambridge, UK. pp
481-99 (1975).

24. Williams, L.E., N.K. Dokoozlian and R. Wample. Grape. In: Handbook of
Environmental Physiology of Fruit Crops. I. Temperate Crops. B. Schaffer and
P.C. Andersen (Eds) CRC Press, Boca Raton, FL, pp 85-133 (1994).

25. Winkler, A.J. Pruning and thinning experiments with grapevines. California
Agr. Exp. Sta. Bull., 519:1-56 (1931).

26. Winkler, A.J., J.A. Cook, W.M. Kliewer and LA. Lider. General
viticulture. University of California Press, Berkley, CA. p 710 (1974).

27 . Yang, Y.S. and Y. Hori. Studies on the retranslocation of accumulated
assimilates in ’Delaware' grapevines. 111. Early growth of new shoots as dependent
on accumulated and current year reserves. Tohoku J. Agric. Res. 31:120-9 (1980).

101

.5!» as ea. saw... as. 8.5.? e 88s.... 35.... 2.. .583... .3 .3333 .
.83.... .3. e... .55 .86... use. a. 8.88%....513 be... 8... 2.. 3.8853. n

 

    

  
  
  

 

  

 

o... E. S- we. to. n... o. _- 3 - v...
adu Won 9N- .N- «N w. .t h. T 1v - flv
ad. ndn w. T h. .t ed .6 N6. —.v o NV

.33 .89

.6. Van “an- ham- Md Gd- .6- 6.! n V...
«.3 N.K.? “an- Emu. n6 .6. N... :6 . n6

«.6 n. .v 0...”- Nd"- a... v6. Em- Q? t «.9

.d- EON de. wan- h.n We. Wm- 96. .. —.v
0.0. Y: aim. n67 nd of. Mn. 6; .. —.—

.833 a no.9
INNS-II «.— 13 .. u u... e 83»— s........—. 835m 8:...— ..enta :30
Sum... 2.... .835 .88
.35. .15 E...» 3. 8.8.0.5.. 2.».03 DA—

...3. no... 830. a 5.3 8:... e. 8.... 8.85.0 83 in... o... 8... 8.3.2.. 2...... 3.38.. <
.33. no.9 8.3... 5.3 8...?! 80... So... 1885...... 983 63. no... 836. 5.3 8:... 8.. 8....a> 8:32....»
528.56... sense. So. as 38.3 8233 same as... 85s.... 3%... be .N as...

 

v v 3..
n v Qv
N v N?
. v :v
. . .\ .
o v 9v
o . o\ .

 

a .835 a 2.3m 2.258....

. 8:32....»
52.5.2320 .832. .8 .8... 88.58..
.38.... .22.... v.8 .026 .. 03a...

102

Table 3. Components of yield for potted Chambourcin grapevines with I shoot
and 1 cluster (1/1) or, 4 shoots and K4“), 2 (4/2), 3 (4/3) or 4 (4/4) clusters.

 

Yield Cluster fruitfhlnees Berry Berry Berry
(g) weight (g) (g shoot-1) number number fresh weight

Treatment vine-1 cluster-1 gems
111 66.7 66.7 66.7 31.5 31.5 2.1
‘4/1 81.2 81.2 20.3 41.3 41.3 2.0
412 162.1 82.5 41.3 76.0 38.0 2.2
413 190.6 74.8 47.6 89.0 36.0 2.1
4/4 145.5 46.1 36.4 84.3 27.3 1.7
F 818. are e are u: n.s. n".

LSD .05 77.5 24.6 22.6 35.8

 

Table 4. Fruit chemistry of Chambourcin grapes fiom vines
with l shoot and 1 cluster (1/1) or, 4 shoots and 1 (4/1)

 

 

2 (4/2), 3 (413) or 4 (4/4) clusters.
Berry Chemistry
Treatment SS 2g TA
III 21.5 3.23 7.9
4/1 20.6 3.34 7.4
4’2 21.5 3.32 7.8
4/3 21.1 3.31 7.2
4/4 21.8 3.31 7.3
F sig. n.s. n.s. n.s.
LSD .05
SS - soluble solids (brix)
TA - total acidity (g/l)

Table 5. Cr0p load and leaf area gram-lfiuit fresh weight
for Chambourcin grapevines with 1 shoot and 1 cluster (“1) or,
4 shoots and 1 (4/1), 2 (4/2), 3 (4/3) or 4 (4/4) clusters.

Crop Load Leaf area
(yieldl (cm2) g-l
Treatment vine size) nlt wt (fresh)

1!] 2.89 36.8
4/1 5.03 32.1
4l2 10.97 15.3
413 20.16 15.6
4/4 13.41 19.4
F “g. a u

LSD .05 10.35 13.0

103

 

3500‘
A ”0°“ Leaf area vine’1(cm2)
2500-
2000-
1500-

1000- \

2
in

  
  

(c

a

are

Total leaf

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3500-—
. 1/0(D) 4/2(A) 1 2
”£300“ 4,0(0) 4/3(0) Leaf area shoot' (cm) I
3 _‘ 1/1 (I) 4/4(*)
-.- 2500. 4mm 1
*gzoooq
%31500;
g. .
5310004.
3 5..-
. . +
o L , . l » l g 1 L l L I J P
100-
2
907 Leaf size (cm) I
g; 80-
E 70-
.§ 60-
m .
“a 50-
D .
'-‘ 4o-
303 C
20‘ , 1.....,...,...,...
0 200 400 600 800 1000 1200 1400

Growing Degree Days (base 10 C)

Figure l.Leaf area vine.l (A), shoot.l (B) and leaf size (C) of potted Chambourcin grapevines
with 1(0) or 4(0) shoots and no clusters: lshoot, lcluster (I) and; 4 shoots with 1(O), 2(A),

3(9) or 4(*) clusters. Bars represent the LSD at p - 0.05.

104

 

1/0 ([3) 412(1)
2007 4/0(0) 4/3 (0) ,
180- 1/1 (I) 4/4(*) Shoot length vine" "°““‘°“ hm:

Ema-3 4/1 (0) //
7V1“): —-—-——-----"H'
g 120: I / f -

 

 

 

 

 

 

 

 

0'...L.hm4.a.1.n.l...1...1

 

 

180-
160;
1401
120;

j

28'

13

Shoot length shoot (cm)
:6 .8

 

w

 

 

 

 

 

 

O
J
4
.1
.4
...

l T I I I

800 1000 1200 1400
Growing Degree Days (base 10 C)

0
§
.5
8
§

Figure 2. Shoot length vine" (A) and shoot-1 (B) of potted Chambourcin grapevines with 1(0) or
4(0) shoots and no clusters: lshoot, lcluster (I) and; 4 shoots with 1(O), 2(A), 3(0) or 4(*) clusters.

Bars represent the LSD at p - 0.05.

105

 

Leaf number vine'l I
veraison -

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4o
35; 1/0 (a) 4/2 (A) Leaf number shoot'1 I
'7“ 3o; 4/0(O) ,
. l/l(I)
@251 mm
.820-
515..
33..
5; E
o ...,...T...,. .r...,...fi...
o, 200 400 600 800 1000 1200 1400

Growing Degree Days (base 10 C)

Figure 3. Leafnumber vine"l (A) and shoot.1 (B) of potted Chambourcin grapevines with 1(0) or
4(0) shoots and no clusters: lshoot, lcluster (I) and; 4 shoots with 1(O), 2(A), 3(0) or 4(*)

clusters. Bars represent the LSD at p = 0.05.

106

 

   
 
    

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

25
; _ -l veraison harvest

320% Leaf drywt (g) vme

E015:

3

.310—

‘g . pre-bloom

.3 5-

20 Shoot drywt(g) vine'1 do 1

£9 31/0 (:1) 4/2(A)

@151 4/0(0) 4/3(e)

g : 1/1 (I) 4/4(*)

510; 4/1(0)

.5 .

‘g :

.'—." 5‘

m g

A 50; Fruit drywt(g) vine'1

an

:404

a .

'5 so-

: .

b20—

'U .

-‘=':' 10—

.5 0.
T

10 .j.,......,. ,...,.,.,...

o zoo 400 600 800 1000 1200 1400

Growing Degree Days (base 10 C)

Figure 4. Dry weight (g) of leaves (A), shoots (B) and fruit (C) of Chambourcin grapevines with: 1(0) or
4(0) shoots and no clusters; lshoot, lcluster (I) and; 4 shoots with 1(O), 2(A), 3(0) or 4(*) clusters.
Bars represent the LSD at p = 0.05.

V_—_~—“'T

360% 1/1 (I)
£550.} 4/1(O)
o

A

107

 

 

. 1/0(:1) 40(1) Root drywt(g) hamst\ ““le
: 4/0(0) 5 ~

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

f

 

 

1 I I I I I I I I

. . . . , . . , . . . . .
0 200 400 600 800 1000 1200 1400
Growing Degree Days (base 10 C)

Figure 5. Dry weight (g) of roots (A) and trunks (B) of Chambourcin grapevines with: 1(0) or 4(0)
shoots and no clusters; lshoot, lcluster (I) and; 4 shoots with 1(O), 2(A), 3(0) or 4(*) clusters.
Bars represent the LSD at p-0.05.

108

 

7o-: Shoots + leaves + fruit dry wt (g) “m“

     
 
  
  
 

20 _ pre-bloom 5mm berries

 

 

 

 

 

 

 

100;? Trunk + roots dry wt (g)

 

1/0 (:1) 4/2 (A)
4/0 (0) 4/3 (0)
. 1/1 (I) 4/4 (at)
60.3 mm

  
  
  
  

 

 

Storage dry weight (g)
<73

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

40-; B
301 .
160‘
A :A _ l -
31401 ~33: u.- Whole vmedrywt(g)
{5'0 _1 125- y-.51849x+9.3749
75120: 'SIOO- .- r-.69l4 ,
3100: '5’ "'
5‘ 3 5 75 TI 1 l l I
g m: °336§§§
-; . Berrynumber
o u
g 40-: C
20‘...,-.fi,...,...,...jj..,..
0 200 400 600 800 1000 1200 1400
Growing Degree Days (base 10 C)

Figure 6. Dry weight (g) of canopies (A); trunks + roots (B); and whole vines (C) of Chambourcin
grapevines with: 1(0) or 4(0) shoots and no clusters; lshoot, lcluster (I) and; 4 shoots with 1(O), 2(A),
3(0) or 4(*) clusters. Bars represent the LSD at p a 0.05. Inset in C shows the relationship between vine

dry weight at harvest and hem number.

109

 

 

  
 
  

3 1/0 ([3) = -
180—: 4,0 (0) y2-.096:7011x+ 23.465 \ 0
160—: 1/1(l) r "'
: 4/1 (0)
14°: 4/3 (9) o

 

 

 

 

Vine dry weight (g)
:s‘ $

   

 

 

 

40‘; y- .03445x+ 9.8936
20€ r2 = .8786
n I
V ' ' ' ' I ' ‘ ff 1 ‘ ‘ ' I 1 ‘ ' T ‘ I Y ' ' ' l ' ' ' ‘ l ' ' ' ‘ I ' ' ‘ 1
o 500 1000 1500 2000 2500 3000 3500 4000

Leaf area (cm2)
Figure 7. Relationship between vine dry weight and leaf area of potted Chambourcin
vines with 1(D ) or 4 (O ) shoots and no clusters; 1 shoot, lcluster (I ), and; 4 shoots
with 1(0) or 3 (0) clusters.

110

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1/1 4/1 4/2 4/3 4/4

Figure 8. Mean total sugar content of fruit vine'1 at harvest in potted Chambourcin
grapevines with l or 4 shoots and 1 cluster (1/1 and 4/1 respectively) or, 4 shoots

and 2 (4/2), 3 (4/3) or 4 (4/4) clusters. Bars represent the LSD at p = 0.05.

111

CONCLUSION

Shoot number was varied by a factor of six in the first experiment reported in
this dissertation with no apparent effect on the rate of starch utilization from reserves
during the spring growth flush. The canopies of three- and six-shoot vines developed
leaf area more rapidly, however, than did one-shoot vines leading to the conclusion
that the rapid leaf area development was due to greater numbers of leaf development
sites with larger numbers of apical meristems. Secondly, the mere presence of a
larger leaf area during the growth flush and during the growing season did not result
in greater dry matter production by three- and six-shoot vines. Between veraison and
harvest, three- and six-shoot vines continued to produce dry matter, apparently in
response to continued sink demand, while the dry matter content of one-shoot vines
was essentially unchanged during the same period. The result was greater dry weight
of three- and six-shoot vines at harvest, but only at harvest. This leads to the
conclusion that greater leaf area by itself does not cause greater dry matter
production; C02 assimilation and dry matter production are equally dependent on
sink activity.

Canopy morphology was profoundly altered by varying shoot numbers. The
changes that occurred resembled morphological changes associated with water stress,
suggesting that the ability of the roots and/or vascular system to supply water to the

growing shoot tips may ultimately limit shoot elongation and leaf expansion in vines

l 12
with a relatively large number of shoots. The morphological changes led to fewer

flowers per cluster and less leaf area per flower which would result in reduced shoot
fruitfulness. This appears to be a means by which vines regulate the amount of fruit
they produce.

The final experiment demonstrated that competition among shoots for root
supplied growth factors (e. g. water, nutrients and growth hormones) has a much
greater influence on canopy morphology than does competition for carbohydrates by
fruit. Shoot length per shoot, leaf area per shoot and leaf size were inversely related
to shoot number but were not significantly affected by crop load.

Carbon utilized for fruit production was derived from preferential partitioning
to fruit at the expense of vegetative organs. Dry weight of non-fruitcd control and
low-crop—load vines was not different but the relative dry weights of vegetative tissues
were altered as carbon was used for fruit production. In addition to changes in dry
matter partitioning, there was an increase in the amount of dry matter production all
of which was used for fruit production at high crop loads. Because fruit is about 75 %
water, a one gram increase in dry weight results in a four gram increase in fresh
weight.

Roots were the vegetative tissue most negatively affected by the redirection of
carbon to fruit between veraison and harvest. In the absence of fruit, roots appear to
be the strongest carbohydrate sink during the veraison-harvest period. When fruit is
present, it is the strongest sink during that time. Root weights recovered in low crop-

load vines between harvest and dormancy but not in high crop-load or one-shoot vines

1 13
with crop. This may result in reduced vine capacity in the latter treatments during the

following growing season.

The data presented in this dissertation indicate that vines will be most efficient
at sustained fruit production when the fruiting sink is in balance with the carbohydrate
source, leaves. The higher yields observed in minimally pnmd vines result from
crop loads which are in balance with vine capacity. It appears that the control vines
in many studies, which are pruned to a standard node level, are not cropped to their
capacity.

Data collected on cane fresh weight (typically referred to as "vine size")
support the hypothesis that this variable does not accurately reflect vine capacity. An
inverse relationship exists between shoot number and cane fresh weight in the absence
of crop. The presence of crop causes a further decrease in cane fresh weight.
However, the traditional use of "vine size” is to represent vine leaf area. The
hypothesis is that a given weight of canes will support some fixed amount of leaf
area. If cane weight increases, then leaf area must also increase. Because the
amount of fruit which a vine can ripen is directly related to the amount of exposed
leaf area which that vine can produce, an indication of greater leaf area is also an
indication of the capacity for more fruit production. The assumption that a given
weight of canes will support some fixed amount of leaf area, however, is in error.
The data presented here show that a given cane weight can support varying amounts
of leaf area depending on shoot number and crop load. This means that some other

method must be employed to estimate vine capacity of minimally pruned grapevines.

114

The term ”vine vigor” is related to vine capacity. It is used in reference to the
growth rate of individual shoots. However, it is apparent that individual shoots may
grow slowly while a vine still maintains a high capacity for dry matter production. In
this context a vine may have two or three rapidly growing (vigorous) shoots but low
capacity. It would be more appropriate to speak in terms of shoot vigor in this
circumstance. By contrast, a vine may have 150 slowly growing shoots but high
capacity (vigor) for dry matter production. The total amount of shoot growth a vine
can produce appears to be an indicator of "vine vigor" or vine capacity. Shoot length
is directly related to leaf area, so it is possible to integrate the concepts of vine vigor
and vine capacity with measurements of leaf area and shoot length. The concepts of
vine vigor and vine capacity were first identified by Winkler et al.(1974) and it seems
appropriate in light of the information contained herein, to reiterate them here.

Results from this study indicate that the total amount of leaf area (or shoot
length) a vine can produce during the growth flush may be related to the total dry
matter production (i.e. vine capacity) for that season. Further work is necessary to
confirm these results and develop the appropriate mathematical models which will
allow for a precise adjustment of crop load to maximize sustained yields of high
quality fruit. It is likely the results obtained with Chambourcin grafted to 5-C
rootstock will not apply directly to other rootstock/scion combinations and under
different environmental conditions (e. g. growing season length, water and nutrient
availability, and soil type). Thus it is necessary to test the hypotheses developed in

this dissertation under various conditions and with various plant materials.

Appendix A

Starch content

115
Appendix A

Table 1. Starch concentration (mg g-l dry weight) of vegetative tissues of Chambourcin grapevines with one-,
three- or six-shoots.

 

 

 

 

 

 

Mean concentration (myg dry weight)
Date, 1993 GDD Shoot # Trunk Root Leaf Shoot Cane
(base 10 C)
6-16 139 1 55.77 91.34 n.a. 3.24 n.a.
3 37.40 109.93 as. 11.52 n.a.
6 40.55 95.99 n.a. 11.86 an
F sig na n.s n.s.
LSD .05
6-28 273 1 18.05 45.07 18.13 12.08 10.38
3 35.44 60.51 14.18 15.68 20.89
6 19.75 41.48 2245 17.12 9.24
F sig " n.s. n.s. n.s. ”
LSD .05 8.93 8.67
7-7 384 1 30.42 64.02 5.89 36.53 15.19
3 23.81 25.33 6.38 38.76 18.82
6 23.70 52.78 7.70 53.27 27.19
F sig as n.s. n.s. "' n.s.
LSD .05 15.64
7-20 545 1 40.75 57.36 16.10 5237 39.88
3 49.22 76.39 26.24 48.87 42.48
6 52.58 74.88 17.53 45.81 53.32
F sig. n.s. n.s. n.s. n.s. n.s.
LSD .05
8-26 959 1 66.94 80.83 25.49 5272 na
3 71.77 93.41 21.28 54.09 na
6 75.23 75.41 29.94 55.61 n.a
F sig. n.s. us. n.s. n.s.
LSD .05
9-16 1111 l 96.60 131.71 13.42 0.84 n.a.
3 89.90 141.93 6.55 1.25 n.a.
6 100.86 123.97 19.08 1.25 n.a.
F sig n.s. n.s. ns. n.s.

 

Table 2. Total starch content (mg) of vegetative tissues of Chambourcin grapevines with one-,

1'16

 

 

 

 

 

 

three-, or six-shoots.
Mean total starch content of tissues
(In!)
Date, 1993 GDD number Trunk Root Leaf Shoot Cute
(base 10 C) of shoots
6-16 139 1 566.10 637.40 n.a. 1.17 na
3 692.50 420.20 n.a. 5.95 n.a
6 685.30 436.80 na 9.49 as.
F sig. ns. n.s. n.s.
LSD .05
6-28 273 1 223.10 297.07 35.95 10.95 36.03
3 525.60 388.80 38.85 13.22 58.72
6 335.30 259.50 64.09 20.25 27.58
F sig. n.s. n.s. na n.s. n.s.
LSD .05
7-7 384 1 426.10 416.90 21.80 53.02 49.09
3 329.90 179.30 34.56 69.47 55.93
6 352.20 331.30 39.28 78.89 1 10.68
F sig. n.s. n.s. n.s. n.s. n.s.
LSD .05
7-20 545 1 556.50 505.50 66.80 123.20 167.09
3 80210 825.40 195.70 11260 141.95
6 901.90 738.10 125.60 117.80 189.83
F sig n.s. n.s. " n.s. n.s.
LSD .05 65.68
8-26 959 1 1521.60 2703.40 249.20 487.20 na
3 1753.30 2854.80 379.00 427.80 na
6 1815.90 1569.20 51290 377.80 as
F sig ns. ns. n.s. n.s.
9-16 1111 1 229260 4570.20 176.90 8.30 n.s.
3 2113.10 6907.30 128.90 14.20 as.
6 2828.50 5663.90 386.80 1.25 ms.
F sig ns. "' n.s. us.
LSD .05 1870.10

 

Appendix B
Photosynthesis

l 17
Appendix B

Table 1. Photosynthesis data obtained from measuring individual leaves of Chamborucin

grapevines with l or4 shootsandnofruit(1/0and4/0respectively); l shootand 1 cluster(1/1)

or 4 shoots with 1 (4/1), 2 (4/2), 3 (4/3), or 4 (4/4) clusters. VPD - vapor pressure deficit (kpa);

A - net C02 assimilation rate (umol m-2 sec-1); Gs - stomatal conductance (mmol C02 m—2 sec-1);
E - transpiration rate (mmol H20 m-2 sec-1); WUE - water use eficiency (mol C02 / mol H20);
Ci - intracellular C02 concentration (umol C02 / mol C02) and; Gm - mesophyll conductance
(mmol C02 m-2 sec-1).

118'

 

 

 

 

 

 

 

Pro-bloom
GDD base
Treatmurt 10 C VPD A Gs B WUE Ci Gm
1/0 250 4.66 7.42 68.11 4.19 0.002 153.09 56.40
1/1 250 5.38 4.89 29.45 261 0.002 92.53 11.36
4/0 250 5.31 3.59 28.05 223 0.004 13.83 27.75
4/1 250 5.14 4.70 25.71 210 0.003 68.63 27.57
4/2 250 4.90 5.28 40.84 264 0.003 57.66 24.32
4/3 250 6.00 3.24 10.88 1.04 0.005 221.93 3.73
4/4 250 4.85 4.61 4209 3.26 0.001 201.00 23.81
F sig n.s. n.s. n.s. n.s. n.s. n.s. n.s.
LSD .05
5mm berries _
1/0 497 248 15.21 187.87 7.72 0.002 253.64 60.25
1/1 497 246 13.74 185.89 7.48 0.002 259.94 5275
4/0 497 245 13.52 209.42 8.50 0.002 268.85 50. 55
4/1 497 256 1224 184.35 7.75 0.002 266.06 46.27
4/2 497 242 1296 206.84 8.31 0.002 271.51 47.77
4/3 497 243 13.65 204.84 8.07 0.002 268.01 50.90
4/4 497 2.55 13.17 204.66 8.06 0.002 260.12 50.37
F sig n.s. n.s. n.s. n.s. n.s. n.s. n.s.
LSD .05
mid-seam
1/0 619 1.94 11.40 139.29 4.32 0.003 233.97 48.67
1/1 619 239 10.54 98.49 3.55 0.003 200.78 51.73
4l0 619 221 7.96 97.81 3.31 0.003 219.42 36.39
4/1 619 217 10.34 113.73 3.84 0.003 196.92 56.81
4/2 619 206 11.33 135.57 4.11 0.003 211.50 53.76
4/3 619 1.99 11.11 119.78 3.63 0.003 211.37 5246
4/4 619 219 9.10 98.37 3.26 0.003 205.02 43.74
F sig n.s. n.s. n.s. n.s. n.s. n.s. n.s.
LSD .05
var-aim
1/0 961 3.10 5.48 55.78 241 0.004 181.39 29.32
1/1 961 2.64 8.86 127.00 4.91 0.002 226.39 43.16
4/0 961 3.40 6.30 59.55 3.10 0.003 164.42 48.11
4/1 961 3.55 5.05 44.61 244 0.003 170.69 48.85
4/2 961 3.56 3.12 47.87 2.80 0.001 249.37 13.00
4/3 961 3.11 6.35 71.44 3.36 0.002 227.64 29.66
414 961 3.37 4.46 48.40 261 0.002 198.91 19.49
F sig ‘ n.s. n.s. n.s. n.s. n.s. n.s.
LSD .05 0.55
harvest
110 1065 1.68 7.91 131.06 3.53 0.002 250.42 31.48
Ill 1065 1.51 9.09 157.83 3.84 0.002 255.81 35.82
4l0 1065 1.60 8.95 148.92 3.90 0.002 253.14 35.53
4/1 1065 1.51 9.26 154.33 3.77 0.002 253.22 36.61
4/2 1065 1.34 10.04 205.02 4.42 0.002 264.43 38.35
4.8 1065 1.50 8.55 191.75 4.19 0.002 269.91 31.78
4/4 1065 1.52 9.66 163.22 3.99 0.002 254.67 37.95
F sig ” n.s. ” ‘ na n.s. n.s.
LSD .05 0.16 35.08 0.48

 

 

 

 

119

Table 2. C02 assimilationbyChambomcin grapevineswith 1 shootwith0(1/0)or1 (1/1) cluster
or, 4 shoots and 0 (4/0)or 4 (4/4) clusters. Data were collectedusingeitherthewhole—plant gas-exchmge
systemdescribedinchapterloraParirinsonbroadleafchamber.

120

bloom
Whole-vine chamber Parkinson broad-leaf chamber

Treatment GDD base A (umol C02 A (umol C02 A (umol C02 A (umol C02

10C vine-lsec-I) m-2sec-1) vine-leec-I) m-2sec-1)

 

 

 

 

 

 

 

 

 

 

 

 

110 330 0.72 10.85 0.33 7.42
1/1 330 1.26 17.50 0.34 4.89
4/0 330 0.82 8.18 0.19 4.7
4/4 330 0.99 11.00 0.41 4.61
F sig n.s. n.s. n.s. n.s.
LSD .05
5mm berries
1/0 512 1.17 1251 1.69 15.21
1/1 512 1.64 19.98 2.15 13.74
4/0 512 1.47 10.86 1.47 1224
4/4 512 1.56 16.21 1.97 13.17
F sig n.s. "' n.s. n.s.
LSD .05 6.97
mid summer
1/0 631 1.53 15.00
1/1 631 1.23 13.42 N.A N.A.
4/0 631 1.50 11.05
4/4 631 1.48 14.88
F sig n.s n.s. n.s. n.s.
LSD .05
late summer
1/0 884 , 2.68 17.07 1.78 11.40
1/1 884 3.08 23.36 216 10.54
4/0 884 270 1274 1.20 7.96
4/4 884 273 16.76 1.88 9.10
F sig n.s. " n.s n.s.
LSD .05 4.05
veraison
1/0 1018 4.29 21.32 1.04 5.48
1/1 1018 3.29 19.94 234 8.86
4I0 1018 4.39 15.78 1.20 6.30
4/4 1018 3.53 16.76 1.10 4.46
F sig n.s. n.s n.s n.s.
LSD .05
m t
1/0 1089 1.75 6.67 2.05 7.91
1/1 1089 1.99 8.72 2.98 9.08
4/0 1089 1.77 5.83 201 8.95
4/4 1089 1.05 4.07 252 9.66
F sig n.s. n.s. n.s. n.s.

LSD .05

 

Appendix C
Fruitfulness

121

Appendix C

 

 

 

«.2 8.. 8.... can 3. amel-
.ud .3. 3 so 3 ad a... dd a... .m: m
8.2 n: n.a. 3... a... 28 28 3.. 5.8 3..
2.3 can on. 2.." a... n.s... won. 3.. Sn 2..
8% can 2:. 28 2... .32 2.: Sn 2.... N;
8.3 n... n... .3 8.: 3:. no: Sh 98 S.
2.... 2n n: 2." S... 32 3.. 9% 3.. S
.2 reels... .35... 83oz 3 7.83... 28... cap
is...» .38.... Pa. .2. Ban... 8.5: .336 sun...
the ass 8.. an... 3.: .286

£33... #5 e a SE n .53 N .23 . e... :8... v .3
E: 8.3... . a... .8... . as. 89>»... .3 52:38.30 88...... 358.3 958.... Ease... .. 2.3.