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c. WIS-91

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INFLUENCE OF CROP LEVEL ON LEAF AND
WHOLE VINE PHOTOSYNTI-IESIS
AND DRY MATI’ER PARTITIONING
IN SEYVAL GRAPEVINES (Vitis .57).)

By

Charles E. Edson

A DISSERTATION

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

DOCTOR OF PHILOSOPHY

Department of Horticulture

1991

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xv

 

ABSTRACT
INFLUENCE OF CROP LEVEL ON LEAF AND
WHOLE VINE PHOTOSYNTHESIS
AND DRY MATTER PARTITIONING
IN SEYVAL GRAPEVINES (Vitis .57).)
By

Charles E. Edson

The inﬂuence of crop level on single leaf (SL) and whole vine (WV) photosynthesis
and dry matter partitioning was studied. 'I‘wo-year-old, own rooted Seyval grapevines
trained to two shoots/vine and grown in 20 L pots were used for this study. Crop level
ranged from 0 to 7.7 clusters/vine. All laterals were removed to eliminate intra—vine
shading. In 1988, laterals were retained on one treatment (LAT). Assimilation (A),
several vegetative and reproductive indices and dry matter partitioning were measured at
several phenological stages of development (phenophases). SLA was measured at four
node positions: basal cluster (BAS), basal + 1 (BAS+1), mid-shoot (MID) and the most
recently fully expanded leaf (ALFE). *

Vines with strong sink activity (high crop level or LAT) showed reductions in shoot
growth, rate and extent of shoot maturation and leaf size. Total leaf area was inversely
related to cr0p level except when laterals were retained, then LAT vines had the highest
leaf area/vine. Yield was correlated with clusters/vine. Leaf area differences were
CVident as early as fruit set, but differences in dry matter allocation did not emerge until
mid-season. Total dry weight/vine was similar for all crop levels, but increased at each

phenophase.

 

 

WVA was expressed as WVA/unit leaf area (WVA/L) and WVA/vine (WVA/V).

SLA and WVA increased from fruit set to mid-season and veraison, then declined. SLA
was positively correlated with crop level in at least one leaf position each phenophase.
SLA increased from the HAS to the ALFE leaf position except at fruit set, when BAS
leaf A was highest. WVA/L was positively correlated with crop level only at harvest.
WVA/V and crop level were not related except at midseason when an inverse correlation
existed, showing that vegetative, as well as fruiting sinks can create a large demand for
assimilates. There appeared to be a strong interaction between vegetative and fruiting
sinks on a whole vine basis, that tended to balance their effects on WVA and total dry
weight/vine. Over the season the ALFE leaf was best correlated with WVA/L, however,
there was no relationship between SLA and WVA/V. Inferring whole vine response from

SIA is not recommended.

 

 

 

 

 

 

 

Copyright by

CHARLES EDWARD EDSON

1991

 

Dedicated to dear friends and the roses.

 

 

 

ACKNOWLEDGMENTS

I would like to thank the members of my guidance committee, Drs. Jim Flore, Don
Dickmann, Ken Poff, Wayne Loescher and Art Cameron for their support and input
during my research and the preparation of this dissertation.

I would like to express my gratitude to my major professor, Dr. Stan Howell for his
guidance, enlightening discussions, and support during my tenure on this project. The
Opportunity to study viticulture under his tutaledge has certainly been rewarding. The
discussions with Dr. Howell and colleagues in the lab will be missed.

Dr. Jim Flore was instrumental to the success of this research project. His
equipment, time, helpful suggestions and support were invaluable and much appreciated.

A special thanks goes to Dr. G.L. Edson, Mrs. C.W. Johnson, D.R. Peony and
family, and to my family and close friends for their patience and moral support during
this endeavor.

I thank Mr. Dave Miller, who offered assistance, insight and friendship. Thanks to
my fellow graduate students in the Viticulture and Enology program: Dr. Keith Striegler,
Mr. Mike McLean, Ms. Teresa Barros and Mr. Russ Smithyman; to Ms. Lynn Teichmann
and Mr. Tom Dittmer for their technical support; and Ms. Gloria Blake, who smoothes
the way for graduate students in the Department of Horticulture. Lastly, I thank Ms.

LuAnn Gloden who did such a wonderful job helping me prepare this manuscript.

vi

 

 

TABLE OF CONTENTS

Baa:

LIST OF TABLES ............................................ ix
LIST OF FIGURES .......................................... xiii
INTRODUCTION ............................................. 1
LITERATURE REVIEW ................................. ' ........ 4
Crop Control .............................................. 4
Vine Growth, Morphology, and Leaf Area .......................... 6
Assimilate Distribution and Translocation .......................... 8
Grapevine Photosynthesis, Canopy Attenuation and the Environment ........ 9
Leaf and Whole Vine Photosynthesis ............................ 14
Inﬂuence of Sink Activity on Photosynthesis ....................... 15
Literature Cited ........................................... 19

Chapter I. Inﬂuence of Cr0p Level on Estimates of Single Leaf and Whole Vine
Photosynthesis of Potted Seyval Grapevines.

Abstract ................................................ 32
Introduction...:............; ............................ .33
Materials and Methods ...................................... 36
Results and Discussion ...................................... 40
Conclusions .............................................. 62
Literature Cited ........................................... 63

Chapter II. Inﬂuence of Crop Level on Grapevine Photosynthesis and Dry Matter
Partitioning at Several Stages of Phenological DeveIOpment. 1. Comparisons of Whole
Vine and Single Leaf Assimilation.

Abstract .................................. ' .............. 69
Introduction .............................................. 69
Materials and Methods ...................................... 72
ResultsandDiscussion ......................... 76
Conclusions .............................................. 93
Literature Cited ........................................... 95

vii

 

 

 

 

Chapter III. Inﬂuence of Crop Level on Grapevine Photosynthesis and Dry Matter
Partitioning at Several Stages of Phenological Development. II. Vine Morphology, Yield,
Fruit Composition,__and Dry Matter Partitioning.

Abstract ............................................... 100
Introduction ............................................. 100
Materials and Methods ..................................... 102
Results and Discussion ..................................... 105
Conclusion ............................................. 129
Literature Cited .......................................... 130
CONCLUSIONS ............................................ 134

Appendix I. The Inﬂuence of Vine Architecture on Gas Exchange
Parameters and Dry Matter Partitioning in Seyval Grapevine .............. 138

Appendix 11. Inﬂuence of Crop Level on the Diurnal Response of
Assimilation in Seyval Grapevines ................................ 157

viii

 

   

LIST OF TABLES

CHAPTERI

Effect of crop level on shoot vigor components and cane

maturation ........................................

Effect of cr0p level on leaf area, leaf size, and leaf area to

fruit and vegetative component ratios of Seyval grapevines .......

Effect of crOp level on dry weight partitioning expressed as

percent of total dry weight. Partitioned September 24, 1988 ......

Effect of cr0p level on yield components (fresh weights)

of pot grown Seyval plants harvested August 30, 1988 ..........

Inﬂuence of cr0p level on the fruit quality indices of

potted Seyval blanc grapes. Harvested August 30, 1988 ........

Comparison of whole plant A and single leaf A by node
position of potted Seyval grapevines, pro-harvest. All values

calculated on a leaf area basis, mol CO2 m’2 s‘1 .............

Effect of cr0p level on whole plant photosynthesis (A) and
related components measured 5-10 days prior to harvest

(8/30/88). All values calculated on a per vine basis ...........

Effect of cr0p level and leaf position on A of potted Seyval

grapevines on selected dates ............................

CHAPTERII

Inﬂuence of crop level on the yield response of Seyval

grapevines harvested September 18, 1989 ...................

Inﬂuence of crop level on total dry weight accumulation at

several phenophases of Seyval grapevines ..................

ix

 

Page

...... 41

.......43

...... 44

...... 46

...... 48

...... 53

...... 56

...... 58

......77

...... 79

 

 

Inﬂuence of crop level on leaf area accumulation at several
phenophases in Seyval grapevines .............................. 80

Inﬂuence of cr0p level and leaf position on single leaf
photosynthesis of Seyval grapevines at several phenophases ............ 82

Inﬂuence of cr0p level and phcnOphase on single leaf
photosynthesis at several leaf positions of Seyval grapevines ............ 84

Inﬂuence of cr0p level on whole vine photosynthesis
calculated on a leaf area basis in Seyval grapevines .................. 87

Inﬂuence of crop level on whole vine photosynthesis at
several phenophases for Seyval grapevines ........................ 88

Inﬂuence of cr0p level on carbon assimilated per gram of
cluster or total vine dry weight at several phenophases
of Seyval grapevine ....................................... 91

CHAPTER III

Inﬂuence of crop level on yield components of Seyval
grapevines at veraison, August 22, 1989 and harvest,
September 18, 1989 ...................................... 106

Inﬂuence of crop level on fruit composition at three
dates post veraison through harvest, September 18, 1989 ............. 108

Inﬂuence of crOp level on shoot growth parameters. of
Seyval grapevines at several phenOphases ........................ 109

Inﬂuence of cr0p level on cane maturation of Seyval
grapevines ............................................. 1 1 1

Inﬂuence of vine size class on partitioning of Seyval
grapevines, partitioned at planting, June 10, 1989 and bud
burst, June 23, 1989 ...................................... 116

Inﬂuence of crop level on dry weight partitioning of Seyval
grapevines. Partitioned at fruit set, July 1, 1989 ................... 117

Inﬂuence of crop level on dry weight partitioning of Seyval
grapevines. Partitioned at veraison, August 22, 1989 ................ 118

 

10.

11.

12.

 

Inﬂuence of crop level on dry weight partitioning of Seyval
grapevines. Partitioned at harvest, September 22, 1989 .............. 119

Inﬂuence of crop level on dry matter partitioning patterns
in Seyval grapevines. 1989 ................................. 120

Inﬂuence of crop level on the root system development in
Seyval grapevines at several phenophases, 1989 ................... 122

Inﬂuence of crop level on the relationship between leaf area
at several phenophases and fresh fruit yield at harvest of
Seyval grapevines ........................................ 123

Inﬂuence of crop level on the relationship between leaf area
and cluster dry weight or total vine dry weight at several
phenophases of Seyval grapevines ...................... . ....... 124

APPENDIX I

Inﬂuence of vine architecture and crop level on leaf area
characteristics of Seyval grapevines ............................ 142

Inﬂuence of crop level on leaf area characteristics of Seyval
grapevines. 1990. Spur trained vines .......................... 143

Inﬂuence of vine architecture and cr0p level on yield indices
of Seyval grapevines harvested 9/27/90 ......................... 144

Inﬂuence of vine architecture and crop level on fruit quality .
indices of Seyval grapevines harvested 9/27/90 .................... 145

Inﬂuence of vine architecture and crop level on shoot growth
parameters and vegetative maturity indices of Seyval grapevines ......... 146

Inﬂuence of vine architecture and crop level on berries per vine,
shoot length and dry weight partitioning of Seyval grapevines .......... 147

Inﬂuence of vine architecture and crop level on dry weight
partitioning of Seyval grapevines (expressed as a percent of
total dry weight) ......................................... 148

Inﬂuence of vine architecture and crop level on single

leaf assimilation (umol C02/m2/sec) of Seyval grapevines
measured on two dates. Fruit was harvested 9/27/90 ................ 149

xi

 

 

10.

11.

12.

13.

14.

15.

 

Inﬂuence of vine architecture, cr0p level, and leaf position on

carbon assimilation (A), stomatal conductance (GS), transpiration

(E), water use efﬁciency (WUE), meSOphyll conductance (Gm),

and internal C02 (Ci) of Seyval grapevines, measured 8/28/90 'L ........ 150

Inﬂuence of crop level (borne on spurs) and leaf position on

carbon assimilation (A), stomatal conductance (Gs), transpiration

(E), internal C02 (Ci), meSOphyll conductance (Gm) and water

use efﬁciency (WUE) of Seyval grapevines, measured 8/28/90 ......... 151

Inﬂuence of vine architecture, crop level, and leaf position on

carbon assimilation (A), stomatal conductance (Gs), tranSpiration

(E), water use efﬁciency (WUE), meSOphyll conductance (Gm),

and internal CO2 (Ci) of Seyval grapevines, measured 9/11/90 ......... 152

Inﬂuence of cr0p level (borne on spurs) and leaf position on
carbon assimilation (A), stomatal conductance (Gs), transpiration

(E), and water use efﬁciency (WUE) of Seyval grapevines,
measured 9/11/90 ........................................ 153

Inﬂuence of vine architecture and crOp level on yield, fruit set,
and assimilation measured on two dates ......................... 154

Inﬂuence of vine architecture and cr0p level on yield, leaf area

parameters and assimilation of Seyval grapevines. 1990 ............. 155

Correlation coefﬁcients for the relationship between crop

level and assimilation (A) .................................. 156
APPENDDI II

Diurnal inﬂuence on leaf temperature at midseason (July 16,
1989) veraison (August 21, 1989), and harvest (August 28,
1988) ................................................ 159

xii

 

 

 

LIST OF FIGURES

Figure

CHAPTERI

Inﬂuence of cr0p level and leaf position on the diurnal response
of Seyval grapevine assimilation, measured 2 days pre-harvest

on August 28, 1988 ....................................... 49

Inﬂuence of leaf position on assimilation in Seyval grapevines

following harvest ......................................... 60
CHAPTER III

Inﬂuence of crop level on leaf area accumulation at several

phenophases in Seyval grapevines ............................. 1 13

Inﬂuence of crop level on whole vine assimilation (per vine

basis) at several phen0phases for Seyval grapevines ................. 127
APPENDDI I

Schematic of A) standard (clusters borne on shoots), and

B) Spur (clusters borne on defoliated spurs) vine architecture .......... 140
APPENDIX II

Diurnal response of grapevine Basal leaf SLA to crop level

inﬂuences at mid-season, measured 2 weeks post bloom ............. 160

Diurnal response of grapevine ALFE leaf SLA to crop level

inﬂuences at mid—season, measured 2 weeks post-bloom ............. 162

Diurnal response of grapevine mid-shoot leaf SLA to crop
level inﬂuences at veraison (fruit soluble solids = 10° Brix

on August 18, 1989) ...................................... 164

xiii

 

 

Diurnal response of grapevine ALFE leaf SLA to cr0p level
inﬂuences at veraison (fruit soluble solids = 10° Brix on
August 18, 1989) ........................................ 166

Diurnal response of grapevine SLA to crop level 2 days
pro-harvest, August 28, 1988 ................................ 168

xiv

 

 

 

INTRODUCTION

Grapevine canopy management has been an area of great interest and research
efforts over the course of the last several years. Increased appreciation of the work done
by Dr. Nelson Shaulis and his colleagues in New York State, U.S.A., and further work
and popularization of the related concepts by Dr. Richard Smart and his colleagues in
New Zealand has been largely responsible for this impetus. Several other researchers
both in the USA. and abroad have also made contributions to our understanding of
proper canopy design, structure, and function. Among these are Dr. W. Koblet, Dr. A.
Carbonneau, Dr. W.M. Kliewer, Dr. P.E. Kriedemann, Dr. G.S. Howell, Dr. J .R. Morris
and Dr. A.G. Reynolds. Many others (including the researchers mentioned above) have
worked in basic research areas studying photosynthesis and other aspects of grapevine
physiology.

Through their efforts we have begun to understand how the factors that inﬂuence
the vine's capacity for growth (both vegetative and reproductive) interact with cultural
management systems and ultimately the environment to produce seasonal canopy grth
and quality yields. Further, the importance of light penetration into the canopy and its
positive effects on vine photosynthesis (Carbonneau et al., 1983; Kriedemann, 1977;
_Kriedemann and Smart, 1971; Smart, 1974a), fruitfulness (Buttrose, 1970; 1974; Howell

et al., 1991; Shaulis and Smart, 1984), fruit composition (Kliewer and Lider, 1968;

 

 

Koblet, 1987; Morris et al., 1984; Reynolds, 1986; Reynolds and Wardle; 1989a,c; Smart,

1987), yields (Morris et al., 1984; Shaulis et al., 1966; Shaulis and Smart, 1974), and
winter hardiness (Howell et al., 1978; Howell, 1988; Shaulis and Smart, 1974; Stergios
and Howell, 1977) have been elucidated.

Crop level plays an important role and has been shown to affect vine morphology
(Reynolds et al., 1986), physiology (Kliewer and Weaver, 1972; Morris and Cawthon,
1982; Winkler et al., 1974), fruit quality (Howell et al., 1987), vine size (Howell et al.,
1987; Reynolds et al., 1986) and winter hardiness (Howell et al., 1987). The presence
of fruiting sinks has been associated with increased rates of assimilation (A) in grapevine
when A was measured at single leaf positions (Chaves, 1984; Downton et al., 1987;
Hoﬁcker, 1978; Kaps and Cahoon, 1989). However, to this author's knowledge whole
vine response of A to source/sink adjustments has not been characterized.

As Dejong (1986a) points out, inferring whole vine response from individual leaf
measurements is difficult due to the complexity of the photosynthetic inputs and
assimilate outputs that plants experience on a‘whole plant basis. Lakso (1991) also
discusses the problems that can occur when interpreting plant response to a single stress
(cg. water) without considering or measuring additional and related factors (eg.
temperature). Further, Lakso (1986) suggests that cropping can be thought of as a stress
on the plant.

Dr. G.S. Howell's research group at Michigan State University, USA. has
undertaken a series of studies aimed at better understanding the physiological and
morphological responses of grapevine to crop level, defoliation, and drought. This study

is a component of those efforts, undertaken to quantify whole vine response to the

 

     

3

inﬂuence of crOp level on: 1) whole vine A; 2) dry matter partitioning; 3) comparisons
of whole vine measurements of A with single leaf A; and 4) interactions of factors 1-3

above.

 

 

LITERATURE REVIEW

Cmpﬁontml

Seyval (S.V. 5276) is an important French-American hybrid wine cultivar in the
Eastern United States. Seyval is used to produce an array of wine styles, but as with
many wine grape varieties has some cultural problems. Seyval is a large clustered
cultivar with a tendency to overproduce. Overcropping can have negative effects on fruit
quality (Howell et al., 1987; Kliewer and Weaver, 1972; Morris et al., 1984; Reynolds
et al., 1986; Weaver and Pool, 1969), wood maturity (Howell et al., 1978; Howell, 1988;
Mansfield and Howell, 1981), and vine size maintenance (Fisher et al., 1977; Howell et
al., 1978; Howell et al., 1987; Reynolds et al., 1986; Reynolds and Wardle, 1989b). Crop
control is usually achieved through a combination of balanced pruning, a concept ﬁrst
described by Partridge (1925 a,b; 1926) and further reﬁned by Kimball and Shaulis
(1958), followed by cluster thinning. Balanced pruning uses the weight of 1 year dormant
cane prunings (as an estimate of vine size) to assess the vine's capacity for grth (Bell
et al., 1958; Partridge, 1925b). Capacity is defined as the vine's ability for total
production (W inkler et al., 1974). Vegetative and cropping capacity can then be balanced
to adequately ripen fruit and maintain vine size (Howell et al., 1987; Morris et al., 1984;

Weaver, 1976).

 

 

Flower cluster thinning is nomrally employed for French-American hybrids

(Looney, 1981), but recently interest has shifted towards post bloom thinning of Seyval
as a means to reduce second crop and cluster compactness (Reynolds et al., 1986).
Retention of excess clusters can result in reduced berry size (Reynolds et al., 1986;
Weaver and Pool, 1969, 1973). Additionally, intra-vine competition for carbohydrates
and endogenous growth hormones by both fruiting (Weaver and Pool, 1969) and
vegetative sinks (Coombe, 1973) can have a negative impact on fruit set. One would
expect reduced cluster compactness to result from reduced fruit set in late thinned (or
heavily cr0pped) vines. This effect has been observed in DeChaunac (Looney, 1981),
Carignane, and Thompson Seedless (Weaver and Pool, 1969), but was not observed in
Seyval (Reynolds et al., 1986). Cultural recommendations for many cultivars have
commonly been based on empirical observations in vineyard trials (Howell et al., 1987;
Howell et al., 1991; Morris ct al., 1984; Reynolds et al., 1986). Reynolds et al. (1986)
have determined an optimum cropping level of 17 clusters per 500 grams of cane
prunings for Seyval. -

Within limits, the greater the crop, the lower the fruit quality (Perold, 1927). High
crop levels can negatively inﬂuence berry weight, berries per cluster, Brix, and cluster
weight (Howell et al., 1987; Kliewer and Weaver, 1972; Perold, 1927; Reynolds et al.,
1986), but this may vary with cultivar (Bravdo et al., 1984; Weaver and Pool, 1969,
1973) and year (Reynolds et al., 1986). Cluster weight is related to cluster number
(Howell et al., 1987; Perold, 1927; Reynolds et al., 1986). High crop levels tend to delay
fruit maturity (Weaver and Pool, 1969; Morris and Cawthon, 1982; Reynolds et al., 1986;

Lider et al., 1975) and wood maturity (Howell et al., 1978; Howell, 1988; Shaulis and

 

Smart, 1984). While total leaf area per cluster appears to be a critical factor for vine

hardiness (Mansﬁeld and Howell, 1981), Wolpert and Howell (1985) found no effect of

clusters per shoot on vine acclimation in the fall.

WWW

Crop level affects vine morphology, as well. High cr0p levels are inversely related
to shoot growth, leaf size and leaf area (Bravdo et al., 1984; Eibach and Alleweldt, 1983).
This competitive effect by fruiting sinks can help improve canopy microclimate (Reynolds
and Wardle, 1989a,b) by reducing internal vine shading (Barros, 1991) and increasing
potential photosynthetic efﬁciency (Smart et al., 1990). While improved light levels in
the canopy using this approach may increase the potential for maximum assimilation (A),
sufficient leaf area (7- 14 cm’) per gram fruit must be present to insure adequate ﬁ'uit
ripening (Jackson, 1986; Kingston and Epenhuijsen, 1989; Kliewer and Weaver, 1972;
Smart et al., 1990). Production of adequate carbohydrates to meet both the daily and
metabolic and vine growth demands is necessary for adequate; productivity and vine
survival. Increases in A per unit leaf area are associated with higher cr0p levels
(Candolfi-Vasconcelos, 1990; Chaves, 1984; Hunter and Visser, 1988; Kaps and Cahoon,
1989) and are inversely related to changes in leaf area (Choma et al., 1982; Schaffer et
al., 1986). Thus leaf area is an important morphological parameter related to
photosynthetic efﬁciency. Reduced vegetative growth associated with fruiting has also
been observed in apple (Avery, 1969; Hansen, 1971; Maggs, 1963), strawberry (Choma
et al., 1982; Schaffer et al., 1986), peach (Chambers and van den Ende, 1975; Miller and

Walsh, 1988), and cherry (Kappel, 1991).

 

Many studies have manipulated crop level by removing leaves, lateral shoots, or

vegetative terminals (Buttrose, 1968; Candolfi-Vasconcelos, 1990; Hofacker, 1978;
Hunter and Visser, 1990a,b; Kaps and Cahoon, 1989; Koblet, 1987; Koblet, 1988;
Mansfield and Howell, 1981; Reynolds and Wardle, 1989a,b; Stergios and Howell, 1977;
Wolf et al., 1986). As pointed out in the previous paragraph, a critical factor in crop
level studies is leaf to fruit ratios. However, the competitive effect supplied by vegetative
growth (Carbonneau, 1983; Coombe, 1973; Reynolds and Wardle, 1989b; Flore and
Lakso, 1989) should not be overlooked when making source/sink adjustments. There is
evidence for compensation in photosynthetic efﬁciency (Candolﬁ—Vasconcelos, 1990;
Candolfi—Vasconcelos and Koblet, 1990; Gucci, 1988), assimilate transport (Quinlan and
Weaver, 1970) and in leaf area development (Candolfi-Vasconcelos and Koblet, 1990;
Hunter and Visser, 1990a; Koblet, 1987) to adjustments in source/sink relationships.
Candolfi-Vasconcelos (1990) has recently shown that partially defoliated vines
compensate for the reduction in leaf area by increasing both stomatal and mes0phyll
conductance. .
New shoot growth in the spring is dependent on carbohydrate remobilized from
storage reserves in the perennial portions of the vine (Koblet and Perret, 1982; Scholefield
et al., 1978; Yang and Hori, 1979; Yang et al., 1980). Clusters do not become strong
sinks until post fruit set (Hale and Weaver, 1962), so the negative effects of crop level
on shoot extension might not be expected to emerge until later. Overcropping is not
necessary to measure a reduction in total shoot growth. Eibach and Alleweldt (1983)
observed 17% reductions in shoot length on bearing vines at low yields, compared with

non-bearing vines.

 

 

Whﬂtion and T ‘ A:I III

Assimilate distribution patterns are altered by the presence of fruiting sinks (Eibach
and Alleweldt, 1985; Quinlan and Weaver, 1970), although total dry weight is similar for
both bearing and non—bearing grapevines (Eibach and Alleweldt, 1985) and for fruiting
and deblossomed strawberry (Schaffer et al., 1986). This was not the case for sweet
cherry, where fruiting trees accumulated less dry weight than non—fruiting trees (Kappel,
1991); however, the root system dry weight was not measured. The root system appears
to be an important carbohydrate sink in non-bearing apple (Avery, 1969).

Translocation of photosynthates in Vitis sp. is affected largely by stage of shoot
development (Balcar and Hernandez, 1988; Hale and Weaver, 1962; Hunter and Visser,
1988a), and factors that affect sink/source relationships. Modiﬁcations of sink strength
by methods such as gibberellin application to encourage shoot growth (Roper and
Williams, 1989), tipping (Hofacker, 1978; Quinlan and Weaver, 1970), girdling (Hofacker,
1978; Roper and Williams, 1989; Weaver and McCune, 1959), partial defoliation
(Hofacker, 1978; Quinlan and Weaver, 1970), deblossoming (Quinlan and Weaver, 1970),
and fruit removal (Gucci, 1988; Hofacker, 1978); or modiﬁcation of source strength by
shading (Koblet, 1975; Quinlan and Weaver, 1970) or by carbon dioxide enrichment
(Johnson et al., 1982) can affect movement of assimilates.

Young leaves are initially importers of assimilate (Koblet, 1977). Leaves expand
quickly after unfolding if environmental conditions are favorable, becoming net exporters
of assimilate at 30—50% of full expansion (Hale and Weaver, 1962; Koblet, 1977).
Lateral leaves must reach about 75% of full expansion before they begin to export

(Koblet, 1969). When leaves ﬁrst begin to export, movement is entirely acropetal (Balcar

 

 

and Hernandez, 1988; Hale and Weaver, 1962). Later, at the 3 to 4 leaf stage (Koblet,

1977) or 5 to 6 leaf stage (Hale and Weaver, 1962) or at berry set (Hunter and Visser,
1988a) assimilate movement becomes bi-directional, but is mainly basipetal for basal
leaves. Subsequent to bloom, only those leaves nearest the apex export assimilate
acropetally (Hale and Weaver, 1962). Initially the ﬂower cluster is a very weak sink,
unable to exert more than a localized effect on redirection of photosynthates (Hale and
Weaver, 1962; Koblet, 1977). During berry development and the ripening stage, berries
become strong sinks for photosynthates (Hale and Weaver, 1962; Hunter and Visser,
1988a; Koblet, 1977). lateral shoots become important sources of assimilate for the
clusters borne on the main shoot (Koblet, 1969; Koblet, 1975). Interestingly, Koblet
(1977) reports that assimilate supplied to clusters borne on lateral shoots is translocated
from main shoot leaves, rather than leaves borne on the laterals themselves. There is
little movement of labelled assimilate out of shoots into the trunk or roots prior to fruit
set (Balcar and Hernandez, 1988; Hale and Weaver, 1962; Yang et al., 1980) although
some movement to the roots shortly after fruit set has been reported (Yang et al., 1980).
Significant movement of assimilate from leaves to the roots does not occur until post

veraison (Scholeﬁeld et al., 1978; Yang et al., 1980).

G . El l . C E . l l E .

Environmental factors exert a major impact on plant physiology (Lakso, 1986). Of
these factors, solar radiation has a major inﬂuence on fruit quality (Kliewer et al., 1988;
Morrison, 1988; Morrison and Nobel, 1990; Reynolds and Wardle, 1989a,c), fruitfulness

(Buttrose, 1970, 1974), photosynthetic efﬁciency (Kriedemann, 1968; Kriedemann and

 

 

10

Smart, 1971; Smart, 1973, 1974) and wood maturity (Howell, 1988; Shaulis and Smart,
1974). Recent papers have shown the beneﬁts of an open canopy design that encourages
increased interception of photon ﬂux density (PFD) (Carbonneau and Huglin, 1980;
Gaudillere and Carbonneau, 1986; Howell, 1988; Intrieri, 1987; Kliewer et al., 1988;
Morris et al., 1985; Reynolds and Wardle, 1989a,b; Smart, 1984; Smart et al., 1982a,b;
Wolf et al., 1990; for a general review see Smart, 1985 and Smart et al., 1990). Shaulis
and Smart (1974) concluded "Canopy characteristics obtainable by canopy manipulation
were dominant over vine size, vine spacing, and pruning severity". Response to light is
interactive with temperature (Buttrose and Hale, 1971; Kriedemann, 1968; Kriedemann
and Smart, 1971) and vine water status (Kriedemann and Smart, 1971; Smart, 1974).
The grapevine canopy strongly attenuates incident solar radiation (Shaulis and
Smart, 1974; Smart, 1973, 1984). Individual leaves absorb up to 90% of the ambient
PFD in the photosynthetically active wavelengths of 400—700 run, with 6% reﬂected and
only 4% transmitted (V. vinifera cv. Gewurtztrarniner) (Smart, 1984). The younger
leaves contain less chlorophyll and transmit more light (Kriedemann, 1968). A leaf at
node—1 (apical) has a soft and translucent lamina (0.46 mg chlorophyll/dmz) and transmits
35% of the intercepted PFD, while a mature leaf at node-6 has a hardened lamina (1.75
mg chlorophyll/dmz) and transmits only 10% of the intercepted PFD (V. vinifera cv.
Shiraz) (Kriedemann, 1968). Leaves developed in full sunlight show saturation at one
fourth to one—third full sunlight (Kriedemann, 1968; Kriedemann and Smart, 1971; Smart,
1984).
I Chaves (1984) observed that gross photosynthetic rates always increased from the

basal leaf to the midshoot and then decreased to the apical leaf, which was not yet fully

 

 

11

expanded. This is consistent with observed leaf age effects (Koblet, 1969; Kriedemann,
1968; Kriedemann et al., 1970). Once leaves become fully expanded, they are maximally
productive, gradually decreasing as they senesce. Scholefield et al. (1978) measured
reductions in A of 90% between late summer and autumn. Hunter and Visser (1988c)
observed the highest photosynthetic rates on apical leaves, although the exact node
position of the apical leaf was not clear.

Leaf ontogeny for many species involves both structural changes and changes in
metabolism as the leaf expands (Sestak, 1981). Stomatal conductance reaches a
maximum just prior to full expansion with concomitant changes in enzyme activity
(Sestak, 1981). Increased activity of ribulose-1,5-biophosphate carboxylase/oxygenase
(Rubisco) have been reported to coincide with maximum rates of A observed at full leaf
expansion, although some authors disagree (Sestak, 1981).

Young leaves have densely packed palisade and mesophyll cells, which may
decrease mesophyll conductance compared with mature leaves (Kriedemann et al., 1970).
Assimilation increases from fruit set to midseason and then gradually declines (Candolﬁ-
Vasconcelos, 1990; Chaves, 1984; Pandy and Farmahan, 1977). Hunter and Visser
(1988c) reported reductions in photosynthetic rate for all node positions except their
apical leaf position, which maintained a similar rate until veraison and then increased at
harvest.

CanOpies several leaf layers thick can reduce light levels to 1% of the incident solar
radiation (Smart, 1984). This level is near the compensation point for vine leaf
photosynthesis, 20 mol mas", where full sunlight = 2500 pmol m'zs‘1 (Shaulis and

Smart, 1974; Smart, 1984). At low light, photosynthetic assimilates are insufﬁcient to

 

12

support the rapid ovary grth required for fruit set of the current year’s crop (Roubelakis
and Kliewer, 1976) or ﬂoral initiation for the subsequent year's crop (Kliewer et al., 1988;
Shaulis and Smart, 1974; Smart, 1984). Shade leaf photosynthesis is saturated at lower
light levels (Kriedemann, 1968; Kriedemann and Smart, 1971) and responds to a lower
compensation point (Kriedemann and Smart, 1971). Dark respiration of shade leaves
(glasshouse grown at 30—50% full sun) is about 50% less than that of leaves grown
under full sun (Kriedemann, 1968). If shade leaves are moved into full sun, the initial
response to high light intensity is inhibitory, causing a decrease in photosynthesis
(Kriedemann, 1968; Lakso, 1990). Shade leaves tranSpire more slowly. than sun leaves
(Lakso, 1990). Leaf temperature in Concord, a large leafed cultivar, rose 6 to 10°C above
normal sun leaves, when moved from the shade to the sun (Lakso, 1990). Kriedemann
(1968) observed that after 5 days in full sun, the inhibitory response was lost, although
photosynthesis was reduced by 50% compared with leaves that developed under full sun
exposure.

Even in dense canOpies interior leaves are exposed to sun ﬂecks (intermittent light)
(Kriedemann, 1968; Smart, 1984; for a review see Percy, 1990). Illuminating 8.5% of
the lamina for 8.4% of the time (at about 30% full sun) resulted in achieving
compensation, with continuous light achieving 25% the rate of whole lamina
photosynthesis (Kriedemann, 1968). However, PFD of sun ﬂecks may be well below
saturation. Limitations of CO2 assimilation under transient light conditions may be under
different control than ﬁxation under steady-state conditions, and is poorly understood
(Percy, 1990). Recent work with spinach suggests that the transition time to reach

steady—state high PFD A, is related to starting levels of PFD (Jackson et al., 1991).

 

13

Factors involved in activation of Rubisco have been implicated in this response (Jackson
et al., 1991).

Leaf orientation is also important (Kriedemann, 1971; Smart, 1974, 1984).
Kriedemann and Smart (1971) determined that "the intensity of direct light falling on a
leaf is proportional to the cosine of the incident angle between the normal to the leaf
surface and the incoming radiation". This means shoot orientation and its effect on leaf
angle could be an important training consideration.

Grapevine photosynthesis is most efﬁcient at 25-30°C (Kriedemann, 1968;
Kriedemann and Smart, 1971). Temperatures above 35°C are inhibitory, with rapid drops
in photosynthetic rate at 45-50°C (Kriedemann, 1968; Kriedemann and Smart, 1971).
Low temperatures (<10—15°C) are also inhibitory (Kriedemann, 1968). Reuther (1975)
found that maximum A occurred at 15-20°C in June, 25—30°C in August, and 15-20°C
in October for cultivars adapted to growth in northern Europe. He found that the
depression in A that occurs at both 10-15°C and 30—35°C was related to the ability to
withstand winter temperature minima. Resistant and susceptible cultivars had relatively
higher photosynthetic rates at 10—15°C and 30-35°C, respectively (Reuther, 1975).
Buttrose and Hale (1971) theorized that in addition to structure (grana stacks were rare
at 12°C day/night, but more plentiful with increasing temperature), metabolic pathways
were also affected by temperature. Cultivar differences in photosynthetic response may
be traced to both structural and metabolic differences. Environment may favor one over

another.

 

 

14

MW:

Photosynthesis of grapevine leaves is typically measured using single leaf
measurements. Measurements are generally made at optimum temperature (Alleweldt et
al., 1982; Kriedeman, 1968; Kriedemann and Smart, 1971) and light conditions
(Kriedemann, 1968; Kriedemann and Smart, 1971; Smart, 1985) to compare treatments.
Selection of the leaf to measure varies with author, but frequently several leaves are
measured in an attempt to better characterize plant response. Leaf photosynthesis (Hunter
and Visser, 1988c, 1989) and translocation (Balcar and Hernandez, 1988; Hale and
Weaver, 1962; Hunter and Visser, 1988a; Koblet, 1969,1977) are affected by proximity
to carbon sinks. This same effect has also been observed in apple (Barlow, 1979;
Hansen, 1971) and cherry (Kappes and Flore, 1989). Translocation in grapevine may also
be limited, as in sour cherry (Kappes and Flore, 1989), by leaf orthostichy. Hale and
Weaver (1962) found labelled carbon moved preferentially into clusters on the same side
of the shoot as the fed leaf.

Leaf respiration on a fresh weight basis was considerably higher for fully expanded
leaves than berry tissue (Pandy and Farmahan, 1977), however, when calculated on a dry
weight basis, reSpiration of mature leaves was 2—3 times and 25% lower than the ﬂower
cluster and berries post set, respectively (Niimi and Torikata, 1979). Meristemmatic and
rapidly expanding plant tissue respire at a relatively high rate (Amthor, 1989) and
dramatic reductions in berry respiration (on a dry weight basis) after Stage I have been
observed (Niimi and Torikata, 1979). Additionally, patterns of speciﬁc rates of
respiration vary at different leaf positions and may‘not‘ be the sarrie at similar leaf age

(Amthor, 1989).

 

 

 

15

Assimilation varies with leaf ontogeny, phyllotaxy and proximity to sinks and the
latter two also inﬂuence carbon allocation patterns. __ Respiration rate also varies with
ontogeny and tissue type. These factors make one question whether a measurement of
A on a single leaf would accurately reﬂect A for the whole vine. As pointed out by
DeJong (1986a), relating rates of A measured on individual leaves to the whole plant is
difﬁcult, given the complexity of photosynthetic inputs and assimilatory outputs
experienced by the whole plant. Choma et al. (1982) reported that strawberry fruiting
increased A on a leaf area basis, but not A per plant. Schaffer et al. (1986) found A per

plant to be greater in deblossomed strawberry plants than in ﬁ'uiting plants.

I E] E S' l E . . El I .

The presence of a fruiting sink enhances photosynthetic activity when measured at
a single leaf position in grape (Candolﬁ—Vasconcclos, 1990; Chaves, 1984; Downton et
al., 1987; Eibach and Alleweldt, 1984; Hofacker, 1978; Hunter and Visser, 1988c; Kaps
and Cahoon, 1989; Kriedemann and Lenz, 1972; Loveys and Kriedemann, 1974), cherry
(Gucci, 1988; Sams and Flore, 1983), apple (Avery, 1977; Fujii and Kennedy, 1985;
Hansen, 1971), peach (Crews et al., 1975; DeJong, 1986b), strawberry (Choma et al.,
1982; Shaffer et al., 1986), plum (Gucci, 1988) avocado (Schaffer et al., 1987), and bean
(Geiger, 1976). However, stimulation of single leaf A is not always observed in grape
(Williams, 1986), cherry (Roper et al., 1988) or apple (Rom and Feree, 1986).

Lack of differences between rates of A in fruiting vs. non-fruiting plants may be
attributed to: 1) time during the season the measurement occurred; or 2) relative

inﬂuence of vegetative sinks. Chaves (1984) showed stimulation of A by fruiting sinks

 

16

in grapevines late in the season (harvest) but not earlier during the vegetative phase. The
strong fruit sink effect gradually increases as the season progresses (Hale and Weaver,
1962). Kappel (1991) recently reported that current season's growth (wood and leaves)
was a greater sink for photosynthates than fruit in sweet cherry. He based these
conclusions on dry matter allocation patterns observed for fruiting and non-fruiting trees.

Downton et al. (1987) investigated the diurnal response to cropping on A, showing
a gradual reduction from a peak early in the day for both fruiting and non-fruiting V.
vinifera cv. Riesling, although fruiting vines maintained higher rates of A throughout the
day. Carbonneau (1984), measuring fruiting vines, observed a similar response.

The mechanisms involved in regulating source/sink modiﬁcation of A are not
known. Several mechanisms have been proposed (for reviews see: Flore and Lakso,
1988; Herold, 1980; Neales and Incoll, 1968): 1) end product inhibition (Gucci, 1988;
Neales and Incoll, 1968; Schaffer et al., 1987; Shaw et al., 1986); 2) hormonal control
(Roper and Williams, 1989; Geiger, 1976); 3) enzyme regulation (Hammond et al., 1984;
Ho, 1979); and 4) energy charge regulation (regulating the pool of organophosphate (P)
in the chloroplast) (Herold, 1980).

Several authors have shown a correlation between a buildup of carbohydrates in the
leaf and reduced rates of A (Gucci, 1988; Neales and Incoll, 1968; Schaffer et al., 1987;
Shaw et al., 1986). Increased levels of starch, rather than soluble sugars are usually
observed. Ho (1976) has correlated rates of carbon export to sucrose concentrations in
the leaf and maintains that enzyme regulation is likely (Hammond et al., 1984; Ho, 1979).
Stitt (1990) observes that photosynthetic sucrose synthesis in the chloroplast is regulated

by the metabolite fructose-2,6—bisphosphate. Fructose-2,6—bisphosphate acts to control

 

 

17

pool sizes of Pi and triose P, to regulate starch/sucrose partitioning, and Pi availability for
photosynthesis.

Herold (1980) noted that regulating the Pi pool may be an important factor, but that
separating the Pi and triose P components is difﬁcult. Pradet and Raymond (1983), in
their review, discuss the ongoing debate about the importance of adenine nucleotide
regulation of photosynthetic ﬁxation of C02.

Roper and Williams (1989) performed girdling experiments on grape, and showed
no correlation between carbohydrates in the leaves and rates of A. They hypothesized
that a buildup of abscisic acid (ABA) in the leaves may be responsible for reductions in
A, and further that applied gibberellic acid (GA) could negate the effects of ABA. Hoad
et al. (1977) observed an increased concentration of cytokinin—glucoside and decreased
levels of gibberellin—like substances following fruit removal. Competition between
vegetative sinks and fruiting sinks for both hormones and growth substances (Coombe,
1973) may also be a factor. Herold (1980), in his review, indicated that no conclusive
hormonal mechanism regulating carbon ﬁxation and allocation has been elucidated. The
question of mechanism is a complex one, and further research will be needed to provide
conclusive answers.

The following questions in respect to crop level effects on whole vine
photosynthetic reswnse remain unanswered: 1) Is the whole vine response of A in
grapevine similar to that measured on a single leaf basis? 2) Which leaf or combination
of leaves, if any, are correlated with whole vine A? 3) What changes occur in, and what

relationships exist between whole vine A and dry matter partitioning? 4) Are the

 

18

relationships queried in 1-3 above consistent during the season or do they vary with stage
of development?

It was the purpose of the research reported here to ﬁnd answers to these questions.

 

19
I'l | C. l

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25

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min-K ..

 

CHAPTERI

Inﬂuence of Crop Level on Estimates of Single Leaf

and Whole Vine Photosynthesis of Potted Seyval Grapevines

31

 

Abstract

Two year old own-rooted Seyval gapevines trained to two shoots per vine and
gown in 20 liter pots were used for this study. Crop level was adjusted to 1.0 (LCL),
3.0 (MCL) or 7.7 (HCL) clusters/vine. HCL vines were trained to three shoots/vine. All
laterals were removed to eliminate intra-vine shading. A fourth treatment, MCL with
laterals retained (LAT) was also included. Single leaf CO2 assimilation (SLA) was
measured at harvest at four node positions: basal cluster (BAS), basal+1 (BAS+1),
mid-shoot (MID) and the most recent fully expanded leaf (ALFE). Vines with strong
fruiting (HCL) or vegetative (LAT) sinks showed reduction in main shoot gowth, node
number, intemode length, rate and extent of shoot maturation and leaf size. Total leaf
area was inversely related to crop level, except when laterals were retained, then LAT
vines had the geatest leaf area/vine. HCL increased total yield and berries/vine, reduced
cluster weight and reduced berries/cluster. Cr0p level was positively correlated with SLA
at the MID and ALFE positions. SLA increased from the BAS to the ALFE position
except SLA at BAS and BAS+1 was lowest for HCL. Whole vine A (WV A) on a leaf
area basis (WVA/L) was also correlated with crop level, however, only SLA at the ALFE
position was signiﬁcantly correlated with WVA/L Whole vine A calculated on a per
vine basis (WVA/V) was not significantly different between treatments and not correlated
with SLA. WVA/L and WVA/V were not correlated. LCL sigliﬁcantly enhanced CO2

ﬁxed/gm fruit but not CO2 ﬁxed/gm total vine dry weight. Leaf area/fruit was correlated

32

 

 

 

33

with the vine's ability to accumulate storage carbohydrates. Total dry weight/vine was

not different among treatments.

Introduction

Seyval (S.V. 5276) is an important French-American hybrid wine cultivar in the
Eastern United States. Under Michigan conditions Seyval has a tendency to overcrop,
which can be problematic given its large cluster size. Overcropping can have negative
affects on fruit quality (Howell et al., 1987; Kliewer and Weaver, 1972; Reynolds et al.,
1986), wood maturity (Howell, 1988), and vine size maintenance (Howell et al., 1987;
Reynolds et al., 1986). Crop control is usually achieved through a combination of
balanced pruning (Kimball and Shaulis, 1958; Partridge, 1925) and cluster thinning.
Current Michigan recommendations call for a balanced pruning formula of 15+10 (15
nodes retained for the ﬁrst 454 gn of dormant one year cane prunings, and 10 nodes
retained for each additional 454 gm), with additional crop control achieved by ﬂower
cluster thinning to 1.5 clusters/node retained. Reynolds et. al. (1986) similarly, have
determined an optimal cropping level of 17 clusters/500 gm. of cane prunings. These
recommendations are based on empirical observations of the effects of pruning severity
and cluster thinning on yield, fruit quality, and vine size maintenance. Seyval's cropping
characteristics make it excellent for studying source-sink effects.

Recently, research has placed emphasis on proper canopy design to achieve canopy
densities that minimize internal shading (Howell et al., 1991; Hunter and Visser, 1989;
Shaulis and Smart, 1984; Smart, 1985). Crop level retained after cluster thinning

inﬂuences shoot vigor through the competition of the various carbon sinks (Eibach and

 

 

34

Alleweldt, 1983). Morphological characteristics such as shoot length, leaf size, cluster
size, cluster weight, and berry weight are affected (Bravdo et al., 1985; Eibach and
Alleweldt, 1983, 1985; Kaps and Cahoon, 1989; Weaver and Pool, 1969).
Physiological responses are altered as well. Several researchers have found the
presence of fruit to stimulate the leaf photosynthesis rate in gapevine (Chaves, 1984;
Downton et al., 1987; Eibach and Alleweldt, 1984; Hofhcker, 1978; Kaps and Cahoon,
1989) and tree crops (DeJong, 1986; Flore and Lakso, 1989; Gucci, 1988; Sams and
Flore, 1983). Fruit removal studies (Gucci, 1988; Hofacker, 1978) and studies that alter
leaf area to fruit ratios by defoliation (Candolfi-Vasconcelos, 1990; Hofacker, 1978;
Hunter and Visser, 1988b), topping (Hofacker, 1978; Kaps and Cahoon, 1989) or girdling
(Hofacker, 1978; Kriedemann and Lenz, 1972; Roper and Williams, 1989) generally
report an inverse correlation. Eibach and Alleweldt (1984) showed a similar reSponse
using potted bearing and non-bearing gapevines. The response of ﬁeld gown vines is
less conclusive. Williams (1986) found no difference in photosynthesis between fruiting
vs. non-fruiting vines. A similar lack of response has also been observed in sweet cherry
(Roper et al., 1988) and apple (Rom and Ferree, 1986) which may have been the result
of a comparative stimulation of A by vegetative sinks in the absence of fruit (Gucci,
1988; Kappel, 1991). Chaves (1984) found differences only late in the season. Downton
et al. (1987) investigated the diurnal response to cropping on A, showing a gadual
reduction from a peak early in the day for both fruiting and non—fruiting Vitis vinrfera cv.
Riesling, although fruiting vines maintained higher rates of A throughout the day.

Carbonneau (1984), measuring fruiting vines, observed a similar diurnal response.

 

35

PhOtosynthesis of gapevine leaves is typically measured using single leaf
measurements. Measurements are generally made at optimum temperature (ZS-30°C)
(Alleweldt et al., 1982; Kriedemann, 1968; Kriedemann and Smart, 1971) and light (above
saturation) conditions (Kriedemann, 1968; Kriedemann and Smart, 1971; Smart, 1985) to
compare treatments. Leaf age studies have indicated that photosynthesis is geatest in
leaves that are fully expanded and medial in age (Alleweldt et al., 1982; Kriedemann,
1968; Kriedemann et al., 1970). Selection of the leaf by node position, age or
morphology varies by author, but frequently, several leaves of the same or different ages
are measured in an attempt to better characterize plant response. Leaf photosynthesis
(Hunter and Visser, 1988b, 1989) and translocation of carbon (Balcar and Hernandez,
1988; Hale and Weaver, 1962; Hunter and Visser, 1988a; Koblet, 1969, 1977) are affected
by proximity to carbon sinks. Translocation in gapevine may also be limited, as in sour
cherry (Kappes and Flore, 1989) by the leaf orthostichy. Hale and Weaver (1962) found
labeled carbon moved preferentially into clusters on the same side of the shoot as the fed

,leaf.

Berry and leaf respiration rates differ (Pandy and Farmahan, 1977; Niimi and
Torikata, 1979). Additionally, patterns of Speciﬁc rates of respiration vary at different
leaf positions and may not be the same at Similar leaf age (Amthor, 1989). Assimilation
varies with leaf ontogeny, phyllotaxy and proximity to sinks and the latter two also
inﬂuence carbon allocation patterns (Balcar and Hernandez, 1988; Hale and Weaver,
1962; Hunter and Visser, 1988a). Respiration rate also varies with ontogeny (Amthor,
1989; Niimi and Torikata, 1979) and tissue type (Amthor, 1989; Niimi and Torikata,

1979; Pandy and Farmahan, 1977). These factors make one question whether a

36

measurement of A on a single leaf would accurately reﬂect A for the whole vine. In
strawberry, Choma et al. (1982) reported that cropping increased A on a leaf area basis ,
but not A per plant. I am unaware of any studies conducted to correlate Single leaf and
whole vine determinations of photosynthesis in gapevine.

The objectives of this study were: 1) to provide quantifiable information on the
interactions between cr0p level, A, and carbon partitioning in gapevine, and 2) to
determine if leaf A measured at several node positions could be used to predict A

measured on a whole plant basis.

Materials and Methods

ElanLMatcrial

Two year old own-rooted Seyval gapevines trained to two shoots per vine and
grown in 20 liter pots were used for this study. Treatments were applied as follows: 1)
High crop level (HCL) vines were unthinned, and all clusters were allowed to develop.
HCL vines were trained to three Shoots per vine to generate sufﬁcient cluster numbers to
represent a high crop level; 2) Medium crop level (MCL) vines were thinned to 1.5
clusters per Shoot retained; 3) Low cr0p level (LCL) vines were thinned to 0.5 clusters
per Shoot retained. To eliminate variances in intra-vine shading which could have been
created by differential lateral shoot gowth due to cr0p level (Candolﬁ-Vasconeelos,
1990), laterals were removed weekly except for treatment 4) which was the same as MCL
plus laterals retained (LAT). LAT was analogous to ﬁeld Seyval where laterals are

I

retained.

 

 

 

 

37

Soil was a loam, sand and peat mix with good water holding and aeration
properties. Vines were watered and fertilized as needed using a Peters 20-20-20
solution. They were maintained on a concrete pad at the Horticulture Research Center,
Michigan State University, East Lansing, MI, US A. The pots were painted white to help
reduce soil temperature. Vines were spaced 0.9 x 15 meters and trained to 2 or 3 stakes
per pot. Pesticide applications were not necessary to maintain undamaged leaves for
photosynthesis measurements. Vines were netted to prevent bird predation on fruit.

Vegetative terminals were never cut.

WVA was determined with an open gas exchange system in a chamber constructed
of plexiglass and polypropylene designed to enclose the vine in an upright position
(modiﬁed after Sams and Flore, 1983). Pots were wrapped in polypropylene ﬁlm so that
root respiration would not increase CO2 levels within the chamber. Transmission of
incident radiation by the chamber was 88-95%. Vines were positioned in the chamber
for maximum exposure of all leaves. Measurements were made at 26°C:1.5° within the
chamber which falls within the Optimum range for gapevine photosynthesis (Alleweldt
et al., 1982; Kriedemann, 1968; Kriedemann and Smart, 1971). Chamber temperature was
controlled using an internal cooling unit coupled to a temperature controller that
maintained the temperature at +/- 0.5 °C. All determinations were made at a minimum
of 1000 mol m"2 s“1 photon ﬂux density (PFD) within the chamber, assuring saturating
light levels (Kriedemann and Smart, 1971; Smart, 1985). Flow rates were initially 70

liters/minute, but this generated C02 depletions of up to 80 ppm in the chamber. CO2

 

 

 

38

3590033 curves generated in the laboratory confirmed this was excessive (data not Shown)
and values were adjusted to reﬂect this CO2 response. Subsequently, ﬂow rate was
increased to 124 liters/minute and no further adjustments were necessary. Air within the
chamber was well mixed by three fans. Gas exchange measurements were made using
an Analytical Development Corporation (ADC) LCA-2 portable gas analyzer adapted for
use with this chamber.

Assimilation was measured between 1130 H and 1400 H on full sun days. This
time window was selected because it fell on the maximal and relatively ﬂat part of the
diurnal response of the vines. A was calculated using a Basic computer progam
developed and written by Moon and Flore (1986). A was calculated on both a per leaf

area and a per vine basis for comparison.

5' l I E E . 'l .

Single leaf determinations were made using a Parkinson broad leaf chamber
(manufactured by ADC) on leaves at four node positions along the shoot: 1) leaf
opposite the basal cluster (BAS); 2) 1 leaf above the basal leaf (BAS + 1); 3) mid-shoot
leaf (MID); and 4) most recently fully expanded leaf (ALFE). Ambient environmental
conditions were PFD > 1000 ,umol m‘2 5", leaf temperature 24-28°C and inlet humidity
0-5%. The leaf blade was positioned perpendicular to the sun. Single leaf
measurements were made at the following stages of development: 1 day pre-harvest, 1
day post harvest, and 16 days post harvest to assess fruit removal effects. Assimilation

was calculated as mentioned above. SLA for individual vines was always measured on

the same day as WVA for comparisons between SLA and WVA.

 

 

39

Periderm browning was rated on two separate occasions to determine the effect of
crop level on the progession of cane maturation. A node was considered mature if the
entire node, bud and basipetal intemodes had browned. Shoot length was measured at
harvest. Leaf area measurements necessary to calculate pre-harvest A were made using
a non destructive method devised in our laboratory for Seyval, by which leaf area can be
calculated from a single linear leaf measurement. The procedure was as follows: 1) the
distance between the tip of the petiolar vein (L4) and the tip of the midvein (L1) (see
Galet, 1979), was measured in centimeters to give 1.; 2) Calculated leaf area = L2/1.6625.
Linear correlation with leaf area measured using a LiCor leaf area meter was Signiﬁcant
with r2 = 0.94 (Escamilla, et. al. unpublished). Final leaf area was determined once
leaves were removed from the vines for partitioning, using a LiCor leaf area meter. Fruit
was harvested on August 30, 1988. Clusters and berries were counted and weighed. All
the clusters on a vine were sampled and a composite 50 berry sample consisting of apical
berries (i.e., distal berries on the cluster rachis) was collected from each vine, weighed
and then frozen for later analysis. Analysis of soluble solids, titratable acidity, and pH
were made using standard methods (Amerine and Ough, 1988).

Plants were maintained for 16 days post harvest and then destructively harvested.
Vines were partitioned into vegetative components and fresh weight was determined. All
components were oven dried at 66°C until no further loss of moisture was observed to

determine dry weight.

 

The experimental design was a completely randomized design. I was interested in

several comparisons in this study. To make comparisons between all treatments, analysis
was by ANOVA, with mean separation calculated using Duncan's Multiple Range Test
(Steel and Torrie, 1980). AN OVA was also used for a speciﬁc comparison between MCL
and LAT vines. Regession analysis was most appropriate for comparisons between cr0p
level for the HCL, MCL, and LCL vines (Chew, 1976). Crop level can be expressed as
clusters per vine, berries per vine or total fruit yield per vine. Clusters and berries per
vine may actually be considered as components of total yield per vine. Linear and
polynomial regessions using clusters per vine, berries per vine, and yield per vine as
independent variables were calculated for dependent variables of interest. Statistics were

calculated using the MSTAT-C and PLOTIT statistical computer packages.

Results and Discussion

Winters

Cr0p level inﬂuenced vine gowth signiﬁcantly. Mean Shoot gowth on HCL vines
was 43.8 and 91.7 cm shorter than MCL and LCL vines respectively (Table 1). The main
shoots on the LAT vines were also shorter, however total shoot length including laterals
was similar to the MCL vines (Table 1). Intemode length, shoot fresh weight and node
number were inversely related to crop level. Clusters per vine was the independent
variable best correlated with shoot gowth parameters (except fresh shoot M.) The
response appeared to be curvilinear with a relatively large percentage accounted for by

clusters per vine. Leaf area per vine and leaf Size were inversely related to crop level,

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42

with LAT and HCL vines producing the smallest main Shoot leaves. However, leaves on
the lateral shoots of the LAT vines were smallest at 23 cm2 (Table 2). LCL vines
produced fewer, larger leaves (Fable 2). Total leaf area on the HCL vines was only 68%
that of the ICL treatment, yet showed only a 10% reduction when compared to the MCL
vines (Table 2). Once again the response appeared to be more curvilinear than linear
(Table 2), however, yield per vine was usually the independent variable best correlated
with leaf area parameters. Reynolds (1988) observed a similar response when he used
a simulated mechanical pruning (SMP) system which retained high Shoot numbers per
vine and a high crop level. Light penetration into the canopy was improved for the SMP
vines, but fruit and wine quality were reduced.

Reynolds (1988) also concluded that the effects on cold hardiness were minimal.
However, we consider that negative effects on cold hardiness are possible due to a
reduction in Storage carbohydrates from overcropping (Table 3) (Howell, 1989; Reynolds
et al., 1986). Difficulties maintaining vine size have also been associated with
overcropping (Kimball and Shaulis, 1958; Reynolds et al., 1986). Crop reduction to

‘ increase vine size as an adjunct to balanced pruning is a Standard recommendation in
Michigan.

Ten to fourteen cm2 of leaf area/gn of fruit are generally considered adequate to
achieve suitable fruit quality (Jackson, 1986; Kliewer and Weaver, 1972). Both the LCL
and LAT vines had geater leaf area than required according to those Studies. Both HCL
and MCL treatments fell below recommended levels, although they would be consistent
with levels required for Italia glasshouse gown gapes (Kingston and van Epenhuijsen,

1989). Perhaps a more informative ratio would be leaf area/gm of total vine dry weight

 

43

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45

(tabh 2). Although not useful in a field situation, for potted vine studies where
destructive sampling can be used, this value should more clearly express the relationship
between leaf area, vegetative vigor, and yield. LAT and LCL vines still had significantly
higher leaf area/dry weight, but differences were not as dramatic as those generated by
the leaf area/fruit parameter.

HCL vines appeared to lose more basal leaves at harvest, but differences were

significant only for the quadratic relationship with berries per vine (Table 2).

Wm

Yields on the HCL vines were greatest, although yields on the MCL vines were not
significantly different when analyzed by ANOVA (Table 4). Berries per cluster were
inversely related to clusters per vine indicating reduced fruit set due to the presence of
a greater number of competitive sinks at bloom was possible (Weaver and Pool, 1969).
It was necessary to retain apical clusters to achieve a suitable crop level for the HCL
treatment. Typically, in Seyval, apical clusters are smaller than basal clusters. This was
likely a contributing factor to the berries per cluster response. ‘

LAT yield was significantly lower than MCL yield, at equal clusters per shoot when
compared separately (Table 4). Lower cluster weight was a result of smaller berry size,
likely caused by competition by the large number of vegetative sinks present on the LAT
vines (37 compared to 3, 2, and 2 for HCL, MCL, and LCL respectively). This conforms
with Coombe's (1973) observations at fruit set.

HCL vines had small clusters with few berries compared with large clusters

containing many berries for the LCL vines (Table 4). Weaver and Pool (1969) and

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47

Reynolds et. al. (1986) also reported a lower incidence of Bonytis cinerea infection in
looser clusters and that may be a related consideration. These vines were not rated for
disease infection; none was present. Visually, the LCL clusters appeared to be more
compact than other treatments.

Fruit were harvested late (at too high a pH for optimum wine quality) in order to
complete pre—harvest photosynthesis measurements. HCL vines showed a delay in
ripening associated with high crop levels, although only soluble solids were signiﬁcantly
different (Table 5). Presence of laterals had no significant effect on fruit composition
(Table 5). ‘

W

The diurnal response of grapevine photosynthesis (decreasing after midday) has
been thought to be mediated by nonstomatal factors (Downton et al., 1987), however,
recent evidence indicates that putative non-stomatal inhibition of photosynthesis induced
by water stress is rather caused by heterogeneous stomatal closure (Downton et al., 1988):
Diurnal response is not limited to water-stressed vines, and in non-stressed vines
declining photosynthetic rates are not necessarily correlated with changes in vine water
status (Downton et al., 1987). This presented a measurement time frame problem we
approached in two ways. First, single leaf determinations were used to generate diurnal
reSponse curves (Figure 1) that allowed one to identify a time window during which
whole plant photosynthesis measurements could be made. There was no significant
difference in the diurnal response between ALFE and BAS leaves, although for HCL

vines ALFE leaves always exhibited higher rates of A (Figure 1). At saturating PFD and

 

Table 5. Inﬂuence of crop level on the fruit quality indices of potted Seyval blanc

grapes. Harvested August 30, 1988.

 

 

Titratable Soluble
Treatment pH Acidity Solids
HCL 3.71 0.81 20.2 b
MCL 3.75 0.84 21.5 ab
LCL 3.80 0.69 22.2 a
LAT 3.85 0.78 23.3 a
ns2 ns *
MCL/LAT" ns ns ns
Linear‘
Clusters ns ns —0.74"
Berries ns ns ns
Yield ns ns 0.43"
Quadratic-
Clusters ns ns -0.74"‘
Berries ns ns ns
Yield ns ns -0.67*

 

zMeans separated by Duncan's multiple range test for F values significant at 5% (‘), 1% (") or

not significant (as).

’Comparison by analysis of variance of laterals vs no laterals at the MCL crop level.
‘Independent variables; significant r2 shown (LAT excluded from regression analysis).

 

 

 

49

Figure 1. Influence of cr0p level and leaf position on the diurnal response of Seyval

grapevine assimilation measured 2 days pre-harvest on August 28, 1988.

 

50

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51

consistent temperature (23.4-27.4°C, see Appendix II, Table 1), HCL vines maintained
higher (albiet slowly decreasing) rates of A throughout the day, until 1900 H after which
PFD soon dropped below saturation.

LCL vines on the other hand, exhibited a slower rise to maximum rates of
photosynthesis that continued from 1200H to 1400H (all points were statistically similar)
(data not shown) before the onset of decline (Figure 1). A time window of 1130H to
1400H was selected as acceptable for comparable measurements. Additional diurnal
measurements taken 16 days post—harvest confirmed the pre—harvest response (data not
shown).

Secondly, to minimize variation, we measured replicates 1-3, early, mid, and late

in the time window respectively.

There were no differences in dry weight accumulation among all treatments when
compared by Al‘IOVA (Table 3). Fruit was produced at the expense of vegetative growth
and storage reserves. LCL resulted in a significant increase in percent dry weight
allocated to storage tissues (Table 3). The response was curvilinear, especially with
respect to clusters per vine (Table 3). This is in agreement with Eibach and Allewelt
(1985) who also observed changes in the pattern of distribution, but not in total dry matter
production when comparing fruiting and non-fruiting grapevines. A similar response has
been observed for strawberry (Shaffer et al., 1986). There was a significant inverse
relationship between berries per vine and total dry weight when comparing HCL, MCL

and LCL vines separately. Given the observations of Eibach and Alleweldt (1985), this

 

52

suggests the HCL vines were in an overcropped condition, depressing total dry weight
accumulation. Vines with laterals (LAT) present had increased storage tissue dry weight
when directly compared to MCL vines (Table 3). In Michigan, and other cool climate
regions, we must carefully balance yield and the accumulation of storage carbohydrates,
to insure vine survival in winter (Howell, 1988). Current season and storage tissue values
for both HCL and MCL vines were similar (Table 3), however, root growth (Table 3) and
vine size (Table 1) were lower for HCL vines and could become problematic over time
if crop level was increased for ﬁeld vines. The HCL treatment delayed cane maturation

(9/8/88), but all treatments were nearly equal two weeks later (Table 1).

W

Response of WVA to crop level differs depending on the method of calculation.

To date, photosynthesis research in grapes has relied primarily on single—leaf
determinations. At the onset of this study, I was interested in determining the whole plant
response of A to crop level, and wished to determine which leaf (node position) or
combinations of leaves were appropriate to measure to accurately reﬂect this whole vine
response. SLA at different node positions was compared with WVA (Table 6). All rates
of A for this comparison were calculated on a leaf area basis. WVA/L increased with
crop level (Table 6). These differences were only signiﬁcant by linear correlation with
yield per vine. This pattern of response was similar to that observed for single leaf
measurements made at the MID and ALFE node positions. However, basal leaves of
MCL vines exhibited higher rates of A than those of HCL vines (Table 6).

Photosynthetic efﬁciency is reduced as leaves senesce (Flore and Lakso, 1989; Hunter and

 

53

Table 6. Comparison of whole plant A and single leaf A by node position of potted
Seyval grapevines, pre-harvest. All values calculated on a leaf area basis,

pmol CO2 m'2 s".

 

 

 

Whole Single leaf determinations
Treatment Plant Basal Basal+1 Mid-Shoot ALFE i
HCL 9.4 6.9 10.3 14.2 a 13.0 a 11.1 a
MCL 8.6 9.6 11.8 11.9 ab 12.3 a 11.4 a
LCL 6.1 7.2 7.4 7.4 7.0 b 6.5 b
LAT 6.0 3.9 -- 6.0 b 6.6 b 5.6 b
nsz ns ns 3* t I
MCL/LAT" ns ns -— ns ns ns
Linear’
Clusters ns ns ns ns ns
Berries ns ns ns 0.56’ 0.55“
Yield 0.56” ' ns ns 0.55" 0.69"
Quadratic
Clusters ns ns ns 0.75“ ns
Berries ns ns ns ns ns
Yield ns ns ns 0.66" ns

 

zMeans separated by Duncan's multiple range test for F values significant at 5% C“), 1% (”) or
not signiﬁcant (ns).

’Comparison by analysis of variance of laterals vs no laterals at the MCL crop level.
xIndependent variables; signiﬁcant 1'2 shown (TAT excluded from regression analysis).

 

 

54

Visser, 1988a, 1989; Koblet, 1977; Kriedemarm, 1968) and increased senescence was
- observed on the basal leaves of HCL vines (Table 2). The fact that significant treatment
differences were observed at both the MID and ALFE node positions suggested that either
of those positions might be acceptable for showing treatment response of SLA. The
greater signiﬁcance values associated with MID leaf A response to crop level indicated
that the MID—node position may be most appropriate for measuring the SLA response.
Regression analysis for comparisons of SLA and WVA/L indicated that ALFE leaf A was
best correlated with WVA/L (r2=0.59, probability of F = .003). No combination of leaves
proved more accurate for estimating WVA/L (data not shown). There are several factors
involved in this lack of correlation that we consider important.

Several metabolic and physiological processes are integrated by the whole plant to
produce net carbon gains (or losses). Much of this response is expressed morphologically
as demands for assimilate vary (Tables 1-3) (Eibach and Alleweldt, 1983, 1985; Kliewer
and Weaver, 1972). WVA/L was lower in most cases than A calculated using single leaf
means (Table 6). This occurred for several reasons. When measuring a single leaf only
a single tissue type (leaf age and condition) is normally evaluated. I observed effects of
both leaf age and position in addition to that of cropping effects on A. This is consistent
with the ﬁndings of other researchers (Alleweldt et al., 1982; Hunter and Visser, 1988b).
Ambient light level and leaf angle to the sun (Kriedemann and Smart, 1971) were
optimized when measuring single leaves. This was done to increase consistency in
treatment comparisons. When measuring whole plants, we can optimize PFD levels, but
leaf angle for all leaves is rarely optimal. Therefore, single leaf determinations likely

overestimate WVA.

 

55

Whole plant measurements represent the mean activity of the entire continuum of
leaves including young, actively expanding leaves (especially LAT vines), which
assimilate carbon at reduced rates if compared with midshoot or even basal leaves
(Alleweldt et al., 1982; Kappes and Flore, 1989; Kriedemann et al., 1976). It has been
hypothesized that young apical leaves with partially developed vascular connections may
not receive the signal to increase photosynthesis (mechanism as yet unelucidated) ﬁ'om
fruiting sinks (Kappes and Flore, 1989). Fruit respiration is also a factor, and although
not measured, could be expected to reduce A CO2 values (Niimi and Torikata, 1979;
Pandy and Farmahan, 1977), leading to an underestimation of A. .

In an attempt to better integrate the above factors to more realistically reﬂect whole
vine response, A was also calculated on a per vine basis. These calculations lead to a
completely different conclusion, that is, crop level does not directly affect WVA/V (Table
7). Rather, the response was morphological (Tables 1—3), based on a reallocation of
resources within the vine driven by sink priority (Table 3). The lower photosynthetic
efﬁciency of the LCL vines (Table 6, leaf area basis) was compensated for by the large
increase in leaf area (Table 2). In strawberry, leaf area compensation was large enough
that deblossomed plants had higher photosynthesis rates than fruited plants (Schaffer et
al., 1986). C02 ﬁxed/gm of fruit was calculated as a measure of productivity and there
was an increase in assimilate production as cr0p level decreased (Table 7). However,
vines produce more than fruit. CO2 ﬁxed/gm total dry weight was nearly the same for
all crop levels, indicating a systematic reallocation as vine needs change.

In the event reproductive sinks are reduced, or removed (cg. poor fruit set, insects,

disease, or pruning) photoassimilate can be allocated to vegetative sinks, to enhance each

 

56

Table 7. Effect of crop level on whole plant photosynthesis (A) and related components

measured 5-10 days prior to harvest (8/30/88). All values calculated on a per

 

 

vine basis.
Assimilation CO2 ﬁxed/ CO2 ﬁxed/
Treatment (mg C02 vine'l 5") gm fruitz gm total dry wt.
HCL 561.0 4.84 c 2.09
MCL ' 567.7 5.00 b 1.96
LCL 573.1 11.60 a 1.86
LAT 657.5 7.23 b 2.24
ns’ * ns

MCL/TAT“ ns ns ns
linearw

Clusters ns ns ns

Berries ns —0.83*" ns

Yield ns —O.89*" ns
Quadratic

Clusters . ns —0.72* ns-

Berries ns -0.96*"”" ns

Yield ns —0.98*" ns
BosLHamest’
HCL 432.17

 

'Mg CO,/vine/grn dry fruit wt. or mg COZ/vine/gm total dry wt.

’Means separated by Duncan's multiple range test for F values significant at 5% (*), 1% (”),
0.1% (*”) or not significant (ns).

‘MCI{U:T gives the comparison by analysis of variance of laterals vs no laterals at the MCL
crop eve.

"Independent variables; signiﬁcant r2 shown (LAT excluded from regression analysis).

'1 day post harvest - based on 1 vine whose pre-harvest A = 513.69, not included in the analysis.

 

57

individual vine's chances for reproduction by increasing storage carbohydrates (hence,
contributing to vine survival) and its future ability to reproduce by generating more nodes,
or sites for ﬂower initiation. This results in shifts in the localized metabolic balance of
the vine. It is these localized changes which are measured on a single leaf basis, rather
than the integrated whole plant reSponse.

Although WVA/V was not statistically different (T able 7), there were trends which
indicate a differential response to varying sink strength may actually be occurring. CO2
ﬁxed/hr/vine/gm total dry weight tended to increase as carbon demand (either
reproductive or vegetative) increased (T able 7). If these differences were maintained over
the course of a growing season (see Chapter II), they would be magniﬁed. Given the
similarity of total dry weight (Table 3), this suggested that there were differences in
respiration associated with the morphological differences observed. These trends (Table
7) lead me to suggest that those vine systems with higher amounts of vegetative tissue
and/or sinks respond with slightly elevated rates of A to meet increased respiratory
demands. The strong negative quadratic correlation between yield per vine and CO2

ﬁxed/gm fruit would support this suggestion (Table 7).

W

To complete the harvest cycle of single leaf measurements, we also measured the
effects of fruit removal on A. Twenty-four-hour post harvest reductions in A of 8%,
13%, and 17% were observed for LCL, MCL, and HCL, respectively (Table 8). Further
reductions of 38—47% for all treatments were observed after 16 days. A gradual

reduction this late in the season has been demonstrated in both non—fruiting vines

 

58

Table 8. Effect of crop level and leaf position on A of potted Seyval grapevines on

 

 

 

selected dates.
1 day 16 days
Treatment Pre-harvestz post harvest post harvest
A (ymol C02 m'zs“)
CropJexel
HCL 11.1 a 9.3 a 5.8
MCL 10.8 a 10.0 a 7.1
LCL 7.0 ab 6.5 ab 4.2
LAT 5.6 b 4.4 b 4.3y
In 1! us
I E E . .
BASAL 6.9 c 5.7 c 2.9 c
BASAL +1 8.9 b 7.0 b 5.3 b
MID ' 9.7 a . 8.1 ab 5.3 b -
ALFE 9.6 a 9.3 a 7.9 a
#* ** it
Mid—Shoot LAT" 7.5 —- 5.5

 

‘Measured 24-48 hours before harvest.

’As a comparison, LAT treatment with fruit retained measured A = 5.0 same date.

‘Means separated by Duncan's multiple range test for F values signiﬁcant at 5% (‘), 1% (") or
not significant (ns).

" Mid—shoot leaf on a lateral shoot, for LAT treatment only. Not included in the analysis.

 

59

(Hofacker, 1978; Striegler, 1990) and vines with fruit retained (Hofacker, 1978; Hunter
and Visser, 1988b). LAT A was reduced by 23% after 16 days. We hypothesize that
rates of A for LAT vines were reduced proportionately less due to the presence of many
active apical sinks. This is consistent with the ﬁndings of Hunter and Visser (1988b), who
observed an increase in photosynthesis rates for leaves proximal to the apex at harvest.
ALFE leaves retained the highest activity and showed reductions of 3% after 1 day and
17% after 16 days, compared to mean reductions of 18% and 48%, respectively for all
other node positions (Figure 2). This differential response demonstrated the stimulatory
effect an active vegetative sink could exert in the absence of strong fruiting sinks.
Evidence to support this conclusion has been reported in grape (Hofacker, 1978;
Kriedemann and Lenz, 1972) and plum (Gucci, 1988). This is interesting since assimilate
translocation is largely basipetal late in the season (Chaves, 1984; Hale and Weaver,

1962; Koblet, 1977).

 

 

Figure 2. Inﬂuence of leaf position on assimilation in Seyval grapevines following

harvest.

61

1111

3 >00 60 $0205 980

 

 

 

mp m: .1 N— OF m 6 1% N o NI .6!
PL_._u_u_L_L_Lbuh.w._.N
_ H... m
- d
to w
- O
. O
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8.8.. F + .88 .I. _ . (x
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. 30.. .007? I _ ..

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62

Conclusions

The data presented in this paper lead me to conclude that .crop level does not have
a direct effect on WVA. Rather, the effect is indirect, mediated initially through
allocation of assimilate to meet carbon demands. This results in morphological changes
which lead to a localized physiological response, i.e. if the vine grew fewer leaves
because it was growing fruit, carbon assimilation by each individual leaf must occur at
a higher rate if total vine demands for assimilate remain unchanged. The vine represents
a balanced system, responding to changes in sink demand to achieve the primary goals
of reproduction and survival. These data also lead me to conclude that vegetative sinks
can create a large demand for assimilate, and may actually be stimulatory to WVA if a
large mass of vegetative tissue with a large maintenance respiration quotient was present.
Two very interesting questions remain unanswered: 1) Does the presence of fruit directly
affect leaf re5piration? and 2) What physiological signal directs the vine's allocation of
carbon?

One must use caution when interpreting single leaf photosynthesis measurements.
While they accurately reﬂected the localized changes in leaf A to the treatment variable
of crop level, they did not have any predictable correlation to the whole vine response.
Inferring whole plant response from single leaf determinations without consideration of

other factors (eg. morphological) appears unwarranted.

 

63

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Amthor, LS. 1989. Respiration and crop productivity. pp. 44-104. Springer-Verlag.
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Chaves, M.M. 1984. Photosynthesis and assimilate partitioning in fruiting and
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Downton, WJ.S., WJ.R. Grant and BK. Loveys. 1987. Diurnal changes in the
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Downton, W.J.S., B.R. Loveys and W.J.R. Grant. 1988. Non-uniform stomatal closure
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Eibach, R. and G. Alleweldt. 1983. Einﬂuss der Wasserversorgung auf Wachstum,
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Eibach, R. and G. Alleweldt. 1985. Einﬂuss der Wasserversorgung auf Wachstum,
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Substanzproduktion. Vitis 24:183-198.

Flore, J.A. and AN. Lakso. 1989. Environmental and physiological regulation of
photosynthesis in fruit crops. Hort. Rev. 11:111—157.

Galet, P. 1979. A practical ampelography. pp. 26—32. Cornell University Press. ISBN
0—8014-1240—4.

Gucci, R. 1988. The effect of fruit removal on leaf photosynthesis and carbohydrate
partitioning in sour cherry and plum. Ph.D. Dissertation. Mich. State University,
East Lansing, Michigan, U.S.A. 199 pp.

Hale, CR. and P.J. Weaver. 1962. The effect of developmental stage on direction of
translocation of photosynthate in Vitis vinifera. Hilgardia 33:89-131.

Hofacker, W. ' 1978: Untersuchungen zur Photosynthese der Rebe. Einﬂuss der ‘
Entblatterung, der Dekapitierung, der Ringelung und der Entfemung der Traube.
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Howell, G.S., T.K. Mansfield and J.A. Wolpert. 1987. Inﬂuence of training system,
pruning severity and thinning on yield, vine size and fruit quality of Vidal blanc
grapevines. Am. J. Enol. Vitic. 38:105—112.

Howell, GS. 1988. Cultural manipulation of vine cold hardiness. Proc. Second Intl.
Symp. Cool Climate Vitic. and Enol. R.E. Smart, R. Thornton, S. Rodriguez, and
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Auckland.

Howell, G.S., D.P. Miller, C.E. Edson and R.K. Streigler. 1991.' Inﬂuence of training
system and pruning severity on yield, vine size and fruit maturity of Vignoles
grapevines. Amer. J. Vitic. Enol. (in press).

 

 

65

Hunter, 1.]. and J.H. Visser. 1988a. Distribution of 14C—Photosynthate in the shoot of
Vitis vinifera L. cv. Cabernet Sauvignon. I. The effect of leaf position and
developmental stage of the vine. S. Afr. J. Enol. Vitic. 9 (1):3-9.

Hunter, LI. and J .H. Visser. 1988b. The effect of partial defoliation, leaf position, and
developmental stage of the vine on the photosynthetic activity of Vitis vinifera L.
cv. Cabernet Sauvignon. S. Afr. J. Enol. Vitic. 9 (2):9-15.

Hunter, 1.]. and J .H. Visser. 1989. The effect of partial defoliation, leaf position, and
deve10pmental stage of the vine on leaf chlor0phyll concentration in relation to the
photosynthetic activity and light intensity in the canopy of Vitis vinifera L. cv.
Cabernet Sauvignon. S. Afr. J. Enol. Vitic. 10(2):67-73.

Jackson, DJ. 1986. Factors affecting soluble solids, acid, pH, and color in grapes. Am.
J. Enol. Vitic. 37:179-183.

Kappel, F. 1991. Partitioning of above-ground dry matter in 'Lambert' sweet cherry
trees with or without fruit. J. Amer. Soc. Hort. Sci. 116(2):201—205.

Kappes, EM. and J .A. Flore. 1989. Phyllotaxy and stage of leaf and fruit development
inﬂuence initiation and direction of carbohydrate export from sour cherry leaves.
J. Amer. Soc. Hort. Sci. 114:642—648.

Kaps, ML. and GA. Cahoon. 1989. Berry thinning and cluster thinning inﬂuence
vegetative growth, yield, fruit composition and net photosynthesis of 'Seyval blanc'
grapevines. J. Amer. Soc. Hort. Sci. 114:20-24.

Kimball, K. and N. Shaulis. 1958. Pruning effects on the growth, yield and maturity of
. Concord grapes. Proc. Amer. Soc. Hortic. Sci. 71:167-176.
Kingston, CM. and CW. van Epenhuijsen. 1989. Inﬂuence of leaf area on fruit
development and quality of Italia glasshouse table grapes. Am. J. Enol. Vitic.
40:130-134.

Kliewer, W.M. and RJ. Weaver. 1972. Effect of crop level and leaf area on growth,
composition and coloration of "Tokay' grapes. Am. J. Enol. Vitic. 23:172-177.

Koblet, W. 1969. Wanderung von Assirnilaten in Rebtrieben und Einﬂuss der
Blattﬂache auf Ertrag und Qualitat der Trauben. Wein-Wiss. 24:277-319.

Koblet, W. 1977. Translocation of photosynthate in grapevines. In: Pr0c. OIV
International Symp. on the Quality of the Vintage. pp. 45-5 1. OVRI, Stellenbosch,
South Africa. '

 

66

Kriedemann, RE. 1968. Photosynthesis in vine leaves as a function of light intensity,
temperature and leaf age. Vitis 7:213—220.

Kriedemann, RE. and F. Lenz. 1972. The response of Vineleaf photosynthesis to shoot
tip excision and stem cincturing. Vitis 11:193-197.

Kriedemann, P.E., W.M. Kliewer and J .M. Harris. 1970. Leaf age and photosynthesis
in Vitis vinifera L. Vitis 9:97-104.

Kriedemann, RE. and RB. Smart. 1971. Effects of irradiance, temperature and leaf
water potential on photosynthesis of vine leaves. Photosynthetica 526-15.

Moon, J.W., Jr. and J.A. Flore. 1986. A basic computer program for calculation of
photosynthesis, stomatal conductance and related parameters in an open gas
exchange system. Photosynthesis Res. 7:269—279.

Niimi, Y. and Y. Torikata. 1979. Changes in photosynthesis and reSpiration during berry
development in relation to the ripening of Delaware grapes. J. Japan Soc. Hort. Sci.
47:448-453.

Partridge, N.L. 1925. Growth and yield of Concord grapevines. Proc. Amer. Soc. Hort.
Sci. 22:84-87.

Pandy, R.M. and H.C. Farmahan. 1977. Changes in the rate of photosynthesis and
respiration in leaves and berries of Vitis vinifera grapevines at various stages of
berry development. Vitis 16:106-111.

Reynolds, A.G. 1988. Response of Okanagan Riesling vines to training system and
simulated mechanical pruning. Am. J. Enol. Vitic. 39:205-212.

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

Rom, CR. and DC. Ferree. 1986. Inﬂuence of fruit on spur leaf photosynthesis and
transpiration of ‘Golden Delicious' apple. HortScience 21:1026-1029.

Roper, T.R., J.D. Keller, WH. Loescher and CR. Rom. 1988. Photosynthesis and
carbohydrate partitioning in sweet cherry: Fruiting effects. Physiol. Plant.
72:42-47.

Roper, T.R. and LE. Williams. 1989. Net assimilation and carbohydrate partioning of
grapevine leaves in response to trunk girdling and gibberillic acid application. Plant
Physiol. 89:1136-1140.

   

67

Sams, CE. and J .A. Flore. 1983. Net photosynthetic rate of sour cherry (Prunus cerasus
L. 'Montmorency') during the growing season with particular reference to fruiting.
.Photosyn. Res. 4:307-316.

Schaffer, B., J .A. Barden and J .M. Williams. 1986. Net photosynthesis, dark respiration,
stomatal conductance, speciﬁc leaf weight and chlorophyll content of strawberry
plants as inﬂuenced by fruiting. J. Amer. Soc. Hort. Sci. 111:430-433.

Shaulis, N. and R. Smart. 1974. Grapevine canopies: management microclimate and
yield responses. In: Proc. XIXth International Hort. Congress. pp. 255-265.
11-18 Sept., Warsaw.

Smart, RE. 1985. Principles of grapevine canOpy microclimate manipulation with
implications for yield and quality. A review. Am. J. Enol. Vitic. 36:230-239.

Steel, R.G.D. and J.H. Torrie. 1980. Principles and procedures of statistics. McGraw-
Hill. 633 pp. ISBN 0-07-060926—8.

Streigler, R.K. 1990. Inﬂuence of rootstock on the response of Seyval grapevines to
environmental stress. Ph.D. dissertation. Michigan State University, East Lansing,
Michigan, U.S.A. 219 pp.

Weaver, RJ. and R.M. Pool. 1969. Effect of various levels of cr0pping on Vitis vinifera
grapevines. Am. J. Enol. Vitic. 20:185-193.

Williams, LE. 1986. Net CO2 assimilation of Vitis vinifera L. leaves as affected by
alterations in source/sink relationships of the vine. In: Proc. International
Workshop on Regulation of Photosynthesis in Fruit Crops. T.M. Dejong (ed.) pp.
35-40. Univ. of California, Davis.

.
‘

 

 

CHAPTERII

Inﬂuence of Crop Level on Grapevine Photosynthesis and Dry Matter Partitioning
at Several Stages of Phenological Development. I.

Comparisons of Whole Vine and Single Leaf Assimilation.

68

Abstract

The inﬂuence of crop level (0, 1, 2, 4 or 6 clusters/vine) in two-year-old, own
rooted Seyval grapevines grown in 20 L pots, was studied. Assimilation (A) was
measured at four phenological stages of development (phenophases). Single leaf A (SLA)
was measured at four node positions. Leaf area/vine and yield/vine were inversely and
positively correlated with clusters/vine, respectively. Total dry weight/vine was similar
for all crop levels, but increased at each phenOphase. Whole vine A (WVA) was also
measured and expressed as WVA/unit leaf area (WVA/L) and WVA/vine (WVA/V).
SLA and WVA increased from fruit set to mid-season and veraison, then declined. SLA
was highest at midseason, and WVA at veraison. SLA was positively correlated with
cr0p level in at least one leaf position each phenOphase. WVA/L was positively
correlated with cr0p level only at harvest. WVA/V was usually not related to cr0p level
but was inversely correlated at midseason indicating that vegetative, as well as fruiting
Sinks, can strongly inﬂuence WV photosynthetic rates. Over the season, the most recently

fully expanded leaf was best correlated with WVA/L, however, there was no relationship

between SLA and WVA/V.

Introduction
Seyval (S.V. 5276) is an important French-American hybrid wine cultivar in the

I

Eastern United States. Seyval is used to produce an array of wine styles, but as with

69

 

 

 

 

70

many wine grape cultivars has some cultural problems, as well. Cultural
recommendations have commonly been based on empirical observations from vineyard
trials (Reynolds et al., 1986). We have initiated a series of studies in an attempt to better
understand the effects of cultural manipulations on vine physiology so that we might
make more precise grower recommendations. Seyval is a large clustered cultivar with a
tendency to overproduce, making Seyval excellent for investigating the inﬂuence of crop
level on physiological and morphological factors.

Recent papers have shown the inﬂuence of canopy design on light penetration and
air movement within the canopy (Intrieri, 1987; Reynolds and Wardle, 1989; Smart, 1985;
Smart et al., 1990; Wolf et al., 1990). These authors discuss speciﬁc physiological
responses to environmental inﬂuences (e.g. light, temperature), but many times the overall
balance within the vine (e.g. the interaction between vegetative and fruiting sinks and the
effects of this interaction on morphological development and physiological response) are
not made clear. These interactions are complex. High crop levels are inversely related
to shoot growth, leaf size and leaf area (Bravdo et al., 1984; Eibach and Alleweldt, 1983).
This competitive effect by fruiting sinks can help improve canopy microclimate (Reynolds
and Wardle, 1989) by reducing internal vine shading (Barros, 1991) and increasing
potential photosynthetic efﬁciency (Smart et al., 1990). However, production of adequate
carbohydrates to meet both the daily metabolic and vine growth demands is necessary for
adequate productivity and vine survival. While improved light levels in the canopy using
this approach may increase the potential for maximum A, sufficient leaf area (7—14 cm’)
per gram of fruit must be retained to insure adequate fruit ripening (Jackson, 1986;

Kingston and Epenhuijsen, 1989; Kliewer and Weaver, 1972; Smart et al., 1990). In

 

71

Chapter I, I also reported delayed wood maturity at 8.2 cm2/g fruit in potted Seyval
grapevines. Additionally, there is evidence for compensation in photosynthetic efﬁciency
(Candolﬁ-Vasconcelos, 1990; Gucci, 1988), assimilate transport (Quinlan and Weaver,
1970) and in leaf area deve10pment (Candolﬁ-Vasconcelos and Koblet, 1990; Koblet,
1987) to adjustments in source/sink relationships. Candolﬁ-Vasconcelos (1990) has
recently shown that leaves on partially defoliated vines compensate for the reduction in
leaf area by an increase in both stomatal conductance to CO2 and. by enhancing the
carboxylation efﬁciency of ribulose-l,5-bisph05phate carboxylase oxygenase.

The presence of a fruiting sink stimulates photosynthetic activity when measured at
a single leaf position (Chaves, 1984; Eibach and Alleweldt, 1984; Hofacker, 1978) (for
review of this subject, see Flore and Lakso, 1989; Herold, 1980; Neales and Incoll, 1968).
Recently I reported similar results when the photosynthetic rate was measured on a
whole vine basis and expressed as ﬂm0| m‘2s°l (see Chapter 1). When WVA was
expressed as A per vine (WVA/V), cr0p level had no effect at harvest. In fact, the
presence of additional vegetative sinks (in the form of laterals) tended to stimulate rates
of A per vine.

Sink activity changes as the season progresses with the clusters gradually increasing
in their ability to attract carbon (or sink strength increases as the fruit develops) after fruit
set (Balcar and Hernandez, 1988; Hale and Weaver, 1962). Leaf age (Kreidemann et al.,
1970) and leaf position are also factors. Apical leaves which are fully expanded generally
have higher rates of A (Chaves, 1984) and maintain them over the course of the growing
season (Hunter and Visser, 1988) when compared to leaves at more basal positions.

Partially defoliated Pinot noir vines maintained higher rates of A early in the season, but

 

 

 

72

showed no differences at harvest when A was measured on a single leaf basis (Candolﬁ-
Vasconcelos, 1990). In contrast, Chaves (1984) found the fruiting effect to be geatest
at harvest.

Clearly, internal response to source/sink alterations changes as the gowing season
progesses. Previously, I expressed concern that single leaf measurements of A made at
several node positions were not well correlated with WVA/V at harvest (see Chapter I).
Similar observations have been made in strawberry (Choma et al., 1982; Schaffer, et al.,
1986).

This study was undertaken to detail the seasonal changes in WVA and dry matter
partitioning as inﬂuenced by crop level in potted Seyval gapevine. The objectives were
to determine: 1) whether the previous conclusions concerning whole vine response and
correlation with SLA were valid over the entire growing season; 2) at what phenophase
the whole vine responses I had observed at harvest became evident and significant; and
3) whether seasonal dry matter allocation patterns would suggest modiﬁcation of cultural
practices or recommended cr0pping levels for Seyval. This paper will be primarily

concerned with the photosynthesis data.

Materials and Methods
ElanLMaterial
Two year old, own rooted, Seyval gapevines gown in 20 liter pots were used for
this study. Soil was a loam and peat mix with good water holding and aeration
properties. Vines were watered and fertilized as needed using a Peter's 20-20-20

solution. They were maintained on a gavel pad at the Horticulture Research Center,

 

73

Michigan State University, East Lansing, MI, USA. The pots were painted white to help
reduce soil temperature. Vines were spaced 0.9 x 1.5 meters.

Pesticides were applied as necessary to maintain an undamaged leaf surface for
photosynthesis measurements. Vines were netted near harvest to prevent bird predation

on fruit.

A special vine architecture was devised for this study so that large cluster numbers
per vine could be produced while still retaining only two vegetative shoots per vine.
Vines were trained to 8 shoots following bud burst, and were allowed to gow for 3
weeks (this was 2 weeks prior to bloom). Flower clusters were removed from the apical
and the basal shoots. These shoots were retained as vegetative shoots. The remaining
shoots were tipped at 2-3 nodes distal to the basal cluster and all leaves were removed.
Fruit retained on these spurs provided variable levels of fruiting sinks without providing
additional leaf area per vine. Spurs were maintained in this condition throughout the
season. The validity of this unique experimental approach was tested in a separate study
(see Appendix I). Although fruit set was reduced for vines which bore their fruit on
Spurs, compared to standard shoots (clusters and leaves on the same shoot) the
photosynthetic response and carbon partitioning were similar.

Crop level was adjusted to 0, 1, 2, 4, or 6 clusters per vine. To eliminate variances
in intra-vine shading, which could have been created by a differential response of lateral
shoot gowth to crop level (Candolﬁ-Vasconcelos, 1990), laterals were removed weekly.

Vegetative terminals were never cut.

 

74

WVA was measured using an open gas exchange system in a chamber previously
described in Chapter I. Measurements were made at 25°C : 05°C. All measurements
were taken at a minimum of 1000 ,umol m'zs'l ambient light within the chamber, assuring
saturating light levels (Kreidemann and Smart, 1972; Smart, 1985). Flow rate in the
chamber was 124 liters/minute. Gas exchange measurements were made using an
Analytical Development Corporation (ADC) portable gas analyzer adapted for use with
this chamber.

Measurements were always taken between 1130 H and 1400 H. Selection of this
time window was based on the predetermined diurnal response curve of the vines (see
Chapter I and Appendix II). Assimilation was calculated using a Basic computer progam
developed and written by Moon and Flore (1986). This method calculates A on a leaf
area basis. Assimilation was also calculated on a per vine basis using the formula:

= Flow (1 min") "‘ 60 (min hr“) " Kl * A CO2 (ppm) ,.
1

A

 

K2

where: . ‘
A C02 = differential between inlet and outlet C02 concentration
K1 = constant for mg CO2 liter‘l at temperature T
K, =[(-6.4 * 10*)* °C]+(1.971 ' 10")
K2 = constant to convert mg CO2 vine'l hr‘l to umol CO2 vine"s"

K2 = 6.3125 * 10-3

 

75

DiumaLAdjustmsnts

We have previously discussed using a mid-day time window for whole vine
measurements of A to reduce inter-vine variability associated with the diurnal effect.
Partly cloudy days are common in Michigan, and procurring A data at a speciﬁc
phenOphase can be difficult. As a result, it was necessary to make some whole vine
measurements outside our preferred time window. Reductions in A are observed after
1400 H (Downton, 1987; see Appendix II). This was handled statistically by measuring
replicates across time during the day. These values are reported as observed values
(OBS). . Alternatively, for those vines measured after 1400 H, OBS was adjusted as
follows to reﬂect mid-day values. The mean value of A between 1130 H and 1400 H
was calculated. Percent reduction of A (compared to the mean) for time outside this
window was also calculated. Assimilation for vines measured after 1400 H was adjusted

accordingly (ADJ).

5.].1 IE! .1.

Single leaf measurements of A were made with an ADC portable gas exchange

\ Q

system on leaves at four node positions along the shoot: 1) leaf Opposite the basal cluster
(BAS); 2) 1-2 leaves above the basal cluster leaf (BAS+2); 3) midshoot leaf (MID); and
4) most recently, fully expanded leaf (ALFE). Ambient environmental conditions were
PFD z 1000 pmol m‘zs“; leaf temperature 24°-30°C; inlet humidity 0-5%. Single leaf
measurements were made at the following phenOphases (to correspond with whole vine
measurements): fruit set, midseason, veraison and harvest. Assimilation was calculated

on a leaf area basis as mentioned above.

w-w.

 

w mww

- A’WMJC' 9M

 

 

76

 

The experimental design was a randomized complete block desigr with vines blocked
on initial vine fresh weight as an estimate of vine size. Crop level was the main plot
factor. For comparisons over time (at different phenophases) analysis was by ANOVA
with phenophase split on crop level. Mean separation was calculated using Duncan's
Multiple Range Test (Steel and Torrie, 1980). Regression analysis was most appropriate
for comparisons between crop level at the individual dates (Chew, 1976). Crop level can
be expressed as clusters per vine, berries per vine or total fruit yield per vine. Clusters
and berries per vine may actually be considered as components of total yield per vine.
Linear and quadratic regessions were calculated using the above crop level parameters
as the independent variable for dependent variables of interest. Comparisons between
SLA and WVA were made using regession analysis. Statistics were calculated using the

MSTAT—C and PLOTIT statistical computer packages.

Results and Discussion

W

In this study, crop level had a significant effect on vine morphology. Total shoot
gowth, nodes per vine and intemode length were inversely related to crop level. Yield
per vine and berries per vine were siglificantly higher for those vines having greater
cluster numbers (Table 1), although at 6 clusters per vine total vine yield was actually
lower than the 4 cluster per vine treatment. Berries per vine were most highly correlated
with yield, suggesting that fruit set was adversely affected at 6 clusters per vine. The

reduced number of berries per cluster (43) for those vines bearing 6 clusters per vine,

 

 

77

Table 1. Inﬂuence of cr0p level on the yield response of Seyval gapevines harvested

September 18, 1989.

 

 

Clusters/ Yield/ Berries/
- vine vine (g) vine
6 507.2 262
4 520.7 271
2 384.1 198
1 288.2 150
0 0 O
1 I i t I *
Linear"
Clusters 0.63‘ * T 0.61 e e e
berries 0.95 "* --
. Vic” . -- 0.95m
Quadratic
clusters 0.60'" 055*"
berries 0.91"” --
yield —- 091“"

 

‘Independent variables; rz signiﬁcant at the 0.1% level.

 

 

78

compared to those bearing 4 clusters per vine (67) (see Chapter [11, Table I) support that
.. conclusion. Intra-vine competition for carbohydrates and gowth substances by both
fruiting (Weaver and Pool, 1969) and vegetative sinks (Coombe, 1973) can have a
negative impact on fruit set. The Spur fruiting system used for this study may have
exacerbated intra-vine competition, since high rates of organogenesis were observed on
spurs as the vine physiology was mobilized to replace the leaves removed from those
spurs. Potted vine studies have shown that total vine dry weight at harvest is similar
between fruiting and non-fruiting vines (Eibach and Allewelt, 1985) and across a range
of leaf area to cr0p ratios (see Chapter I, III). That relationship remained consistent from

fruit set through harvest in this study also (Table 2).

leaLArea

Previously I concluded that the increase in A per unit leaf area associated with higher
crop levels (Candolﬁ-Vasconcelos, 1990; Chaves, 1984; Hunter and Visser, 1988; Kaps
and Cahoon, 1989) was a secondary effect associated with changes in morphological
response. That response could be based on a reallocation of photosynthate resulting from
changes in sink demands. Thus, leaf area is an important morphological parameter related
to photosynthetic efﬁciency.

The inﬂuence of crop level on leaf area was evident as early as fruit set, being
negatively correlated with clusters per vine (Fable 3). This difference was measured only
16 days following crop level adjustments. The ﬂower cluster is reported to be a weak
sink for attracting labelled carbon (Balcar and Hernandez, 1988; Hale and Weaver, 1962).

Given the similarity of total dry weight (Table 2) and the differences in leaf area (Table

 

 

   

 

79

Table 2. Inﬂuence of crap level on total dry weight accumulation at several

phenOphases of Seyval gapevines.

 

Total dry weight/vine (g)

 

Clusters/ Fruit setz Veraison’ Harvest
vine 7/1/89 8/18/89 9/18/89
6 54 207 277
4 50 201 307
2 48 193 299
1 53 209 289
0 -- -- 285
Linear and Quadratic‘
clusters ns ns ns
berries / . ns . ns ns
yield ns ns ns

 

‘5 days post full bloom date.
’Berry soluble solids = 10° Brix.
'Independent variables; r2 not signiﬁcant (n.s.).

 

 

80

Table 3. Inﬂuence of crap level on leaf area accumulation at several phenophases in

Seyval gapevines.

 

 

 

 

Leaf area (cmz)
Clusters/ Fruit setz Midseason Veraison’ Harvest
vine 6/30/89 7/26/89 8/18/89 9/18/89
6 1176 2602 4127 3634
4 1166 3655 4461 4684
2 1449 3992 4480 4870
1 1378 4177 5391 5082
0 -— —- -- 6221
Linear"
clusters -0.53* -0.65*" ns -O.57*"
berries ns -0.36"' ns ns
yield ns -0.43* ns -0.48*"
Quadratic”
clusters ns -0.70" ns -O.57"*
berries ns ns ns -0.45"
yield ns ns ns -O.48"

 

14 days post full bloom.

’Berry soluble solids at 10° Brix.
’Independent variables; r2 signiﬁcant at 5% (*), 1% ("), 0.1% (*") or not signiﬁcant (ns).

 

 

 

81

3) observed at fruit set, it appears that the vine has already perceived the additional
clusters, and that allocation patterns have begun to shift resulting in changes in leaf area

per vine (Table 3). How the vine establishes and senses sink strength is unknown.

W

References to WVA values will be to OBS unless speciﬁcally mentioned. We have
previously concluded that harvest measurements of SLA are useful for characterizing the
individual leaf response of A to changes in source/sink relationships, but do not correlate
well with WVA (see Chapter I). In this study I explored this localized response at several
node positions and made comparisons with both WVA/L and WVA/V at several

phenophases.

S' l I E E . 'l .
Localized effects of crop level on SLA became evident as early as fruit set (Tables
'4 and 5), but a signiﬁcant correlation existed only at the ALFE position (Table 4). By
veraison there were significant correlations between crop level parameters and SLA at
every leaf position (Table 4). There was a sigrificant correlation for each date only at
the ALFE position. The localized stimulatory effect of crop level on A has been observed
by other authors (Hofacker, 1978; Hunter and Visser, 1988; Kaps and Cahoon, 1986;
Pandy and Farmahan, 1977).
Chaves (1984) observed that goss photosynthetic rates always increased from the
basal leaf to the midshoot leaf and then decreased to'the apical leaf, which was not yet

fully expanded. This is consistent with the leaf age effects observed by Kriedemann et

82

 

 

 

Table 4. Inﬂuence of crop level and leaf position on single leaf photosynthesis of
Seyval gapevines at several phenophases.

Leaf position Assimilation ol m'zs'1

x clusters/vine Bloom‘ Midseason Veraison Harvest
BAS

6 15.4 13.3 12.5 10.1

4 15.2 14.4 12.2 5.7

2 15.2 10.9 11.0 5.0

1 12.9 10.5 8.7 2.9

0 —- 9.8 6.4 2.9
Linear’

clusters ns 0.40’ 0.50" ‘ 0.65"

berries ns 0.34’ 0.53‘ ‘ ns

yield as 0.36“ 0.54‘ * ns
Quadratic

clusters ns 0.44’ 0.61" ‘ 0.68”

berries ns ns 0.56’ ns

yield ns ns 0.55‘ ns
BAS+2

6 14.4 13.1 14.2

4 13.5 14.9 10.6

2 N.A. 14.5 13.3 8.1

1 12.9 13.2 6.5

0 8.9 9.8 6.6
Linear .

clusters NA. 0.33‘ ns 0.73" ’ "

berries N.A. 0.63"" 0.30‘ 0.39‘

yield NA. 0.57"" 0.42‘ 0.42'
Quadratic

clusters N.A. 0.53' 0.49“ 0.75”

berries NA. 0.68" 0.48“ ns

yield N.A. 0.63” 0.48‘ 0.56’
MID

6 14.5 17.3 18.9 13.0

4 13.8 18.2 17.8 10.3

2 13.1 18.0 16.6 10.2

1 11.8 15.5 11.3 5.9

0 -- 14.0 9.3 -9.3

 

—continued-

 

   

 

Table 4. (continued)

83

 

 

Leaf position Assimilation (£01 m‘zs")

x clusters/vine Bloomz Midseason Veraison Harvest
Linear

clusters ns ns 0.78" " "' 0.44‘

berries ns ns 0.73‘ " ‘ ns

yield ns ns 0.85’ ” ns
Quadratic

clusters ns ns 0.9 1 ’ ‘ ‘ ns

berries ns ns 0.79“ ‘ " ns

yield ns ns ns ns
ALFE

6 11.5 15.9 16.4 13.5

4 8.1 18.4 18.5 11.7

2 6.1 16.3 18.3 11.6

1 3.1 13.4 13.4 9.5

0 - 12.1 10.7 9.3
Linear

clusters 0.85‘ ‘ "‘ ns 0.3 1 ’ 0.60* "

berries 0.79" 0.27‘ 0.38‘ ‘ ns

yield 0.84"" 0.30‘ 0.51" 0.38‘
Quadratic

clusters 0.85“ " 0.43“ 0.69" "‘ 0.61 "

berries 0.79“ ns 0.61 * "' ns

yield 0.84“ ns 0.59" ns

 

‘See footnote, Table 3.
’lndependent variables; r2 sigriﬁcant at 5% (’), 1% C"), 0.1% ("‘) or not signiﬁcant (ns). NA
is not available.

 

 

 

 

Table 5. Inﬂuence of crop level and phenophase on single leaf photosynthesis at
several leaf positions of Seyval grapevines.
Assimilation (umol m‘zs")
Treatment BAS BAS + 2 MID ALFE
Clusters/Vine
6 12.8 a2 13.9 a 15.9 a 14.3 a
4 11.9 ab 13.0 a 15.1 a 14.2 a
2 10.5 ab 11.9 ab 14.5 a 13.1 ab
1 8.7 be 10.9 ab 11.1 b 9.8 b
0 6.4 c 8.4 b 11.5 b 9.9 b
it ti #1 it
Lineary
clusters 0.26"" 0.30"" 0.24"” 0.13"
berries 0.17" 0.28‘" 0.18" 0.13“
yield 0.16" 0.30"" 0.19" 0.17’
Quadratic
clusters 0.28"" 033*" 0.27'" 0.16'
berries 0.19" 0.19" 0.18" 0.12"
yield 0.17‘ 0.30" 0.19" 0.18”“
Phenophase
Fruit set 14.7 3 NA. 13.2 b 7.2 c
Mid—season 11.8 b 12.8 a 16.6 a 15.2 a ~
Veraison 10.2 b ‘ 12.8 a 14.8 ab '15.5 a '
Harvest 5.3 c 9.2 b 9.8 c 11.1 b
til 3!! ##II It!
Linear
clusters 026*" 0.30'" 0.24"" 0.13’
berries 0.17‘ 0.24" 0.18" 0.12”“
yield 0.16" 0.30"" 0.19" 0.17"
QUadratic
clusters 0.28"" 0.33"" 028*" 0.16'
berries 0.19" 0.27" 0.18" 0.12“
yield 0.17“ 0.30" 0.19" 0.17"

 

'Mean separation for clusters/vine and phenophase by Duncan's Multiple Range Test, signiﬁcant
F at the 1% (”) or 0.1% (“‘) levels.

signiﬁcantly different.

’Independent variables; r2 signiﬁcant at 5% (‘), 1% (“), or 0.1% (”’).

Same letter within each column and goup not

 

85

al. (1970) and Koblet (1969) (e.g. once leaves become fully expanded, they are maximally
productive, gadually decreasing towards senescence). Leaf age effects were also
observed in this study. Leaves in the BAS position were the geatest contributors to A
at fruit set, but later, from mid-season to harvest, MID and ALFE leaves had higher rates
of A (Table 5). Hunter and Visser (1988) observed the highest photosynthetic rates on
apical leaves, although the exact leaf position was not obvious from that paper.
Measurements of leaves at various stages of leaf expansion indicated that variation in A
was high when using young leaves not yet fully expanded (data not shown). Rates of A
were nearly as high in leaves that were 75-80% expanded as those of fully expanded
leaves, but this was not always consistent until leaves were 100% expanded. Analysis
of the data by ANOVA lead to the conclusion that differences in SLA induced by crop
level could be expected only between high (4-6 clusters/vine) and low (0—1 cluster/vine)
crop levels. Regession analysis, however, provided evidence that differences between
all crop levels exist. Although the contribution by crop level (as the independent
variable) was relatively small, it was signiﬁcant. .

Assimilation increased from fruit set to midseason and veraison and then decreased
following veraison to harvest, except for BAS, which was maximal at fruit set (Table 5).
These results are similar to those observed by Candolfi-Vasconcelos (1990) measuring
A at node 11. She also observed that cropped vines maintained higher photosynthetic
rates later in the season than uncropped vines. Pandy and Farmahan (1977) observed a
gradual reduction in photosynthesis following the lag phase in development and Chaves
(1984) observed photosynthetic rates at veraison only 30% of those observed during the

vegetative phase of development. These rates were the means of determinations made at

 

86

several node positions. Hunter and Visser (1988) reported reductions in photosynthetic
rate consistent from berry set onward for all node positions except their apical leaf

position which maintained a similar rate until veraison and then increased until harvest.

Assimilation determined on a whole vine basis leads to a somewhat different
conclusion; WVA, calculated per unit leaf area was highest at veraison (Table 6).
Metabolic demands on the vine may be highest at this time since: 1) the fruit is
beginning to accumulate sugar at a rapid rate; 2) vegetative gowth continues; and 3) root
sinks are active (Yang and Hori, 1980). Assimilation was correlated with clusters per
vine only at harvest and berries per vine only at veraison, the only real similarity to the
SLA measurement (Tables 5, 6). Once again, the variability that could be attributed to
the crop level parameters on those occasions was relatively small, but signiﬁcant.

There are several factors which can cause values to differ between single leaf and
whole vine determinations. of A (see Chapter I). Among these are: 1) angle of
inclination to the sun (which is optimized for single leaf determinations, but can not be
adjusted from the normal leaf orientation on the vine in the chamber); 2) respiration of
plant tissues other than the leaf being measured is not considered; and 3) neither the
variation in leaf age, nor the inﬂuence of phyllotaxy for a given plant system are
considered.

I also calculated whole vine photosynthesis on a per vine basis to better reﬂect the
whole vine response (Table 7). In Chapter I it was previously concluded that crop level

had little effect on WVA/V at harvest. In fact, vines having the geatest number of

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89

vegetative sinks in that study had the highest (albiet, not significant) photosynthetic rate
per vine. Interestingly, in this study the same response occurred at midseason and
veraison, with the highast photosynthetic rates for the 1 cluster/vine treatment (Table 7).
The relationship appears to be strongest at mid—season when the grapevine is in a strong
vegetative growth phase. The relationship weakens at veraison and is absent by harvest
(Table 7). At the time of harvest, apical grth had all but ceased, making the fruiting
sink the only major sink at that time. I draw these conclusions with caution since
WVA/V ADJ reduces the strength of this trend at both mid—season and veraison (Table
7). However, Choma et al. (1282) reported that whole plant photosynthesis of
deblossomed strawberry plants was higher than that for fruiting plants during the last half
of the fruiting cycle, so this response does not appear to be limited to grapevines.
Leaf respiration on a fresh weight basis is considerably higher for leaf tissue than
berry tissue (Pandy and Farmahan, 1977). When calculated on a dry weight basis,
respiration rate of mature leaves is 2—3 times lower and 25% lower than that of the
ﬂower cluster and berries. (post set), respectively (Niimi ' and Torikata, 1979).
Meristematic and actively expanding tissues respire at a relatively high rate compared to
mature leaf tissue (Amthor, 1989) and dramatic reductions in berry respiration (on a dry
weight basis) after Stage I have been observed (N iimi and Torikata, 1979). Additionally,
patterns of speciﬁc rates of respiration vary at different leaf positions and may not be the
same at similar leaf age (Amthor, 1989). With respect to respiration, it is important to
consider the total amounts (dry weight) of each type of tissue and how they change
seasonally (see Chapter III). Differences in respiration rate may be an important factor

in this evaluation, unfortunately respiration was not measured during this study.

 

 

Assimilation at mid-season was inversely related to crop level (Table 7), yet there were

no differences in carbon ﬁxed per unit of total dry weight (Table 8). This suggests a
lower metabolic cost for producing fruit than vegetative structures. Cell structure for the
fruit is produced early, with remaining fruit growth being the result of cell expansion as
water and sugars move into pre-existing cells (Pratt, 1971). Vegetative growth, by
comparison, involves a process of constantly generating new cells, and on a whole vine

basis likely requires greater metabolic energy.

CmnparisnuLSIAandﬂA

I was also interested in two questions involving SIA and WVA measurements: 1)
Does any individual SLA determination correlate with WVA?; and 2) If we restrict our
inquiries to localized effects of treatment on SLA, which leaf is most appropriate to
measure? The present data indicate that the ALFE leaf position most consistently showed
correlation with crop level parameters (Table 5). However, it is important to be speciﬁc
in the question asked. For instance, at fruit! set there were only negligible differences '
among crOp level at the BAS and MID leaf positions.

Correlation between SIA and WVA per unit leaf area was almost nonexistent when
regression coefﬁcients were calculated at each stage of phenophase. SLA for the BAS
leaf was positively correlated with WVA/L only at harvest (r2=0.47, sig. ‘). Previously
I had concluded that the ALFE leaf was best correlated at harvest with WVA/L. It should
be noted that there was greater senescence of basal leaves associated with high crop level
in that study (see Chapter I). Correlations made across the season lead to different

conclusions. SIA at both the MID and ALFE leaf positions were highly correlated with

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WVA/L (r2=0.43, sig. *** and r2=0.44, sig. "", respectively). No correlations between

SLA and WVA/V were signiﬁcant. It seems appropriate to again conclude that caution
must be exercised when extrapolating whole vine response from single leaf

determinations.

Eieldﬁmwnieﬂal

Stimulation of SLA by fruiting sinks has not always been observed in ﬁeld grown
grapevines (Williams, 1986). I investigated the effect of crop level on SLA at 3 leaf
positions along fruiting shoots in ﬁeld grown Seyval, both at fruit set and post veraison
to investigate this apparent discrepancy. CrOp levels were 0.5, 1.5 clusters per node
retained, and an unthinned treatment (2.2 clusters per node retained). Recommended crop
level for ﬁeld Seyval in Michigan is 1.5 clusters per node retained at a 15+10 pruning
severity (G.S. Howell, personal communication). There were no crop level effects on A
at any given date or node position, although as in potted Seyval, A increased between
fruit set and‘post-veraison (data not shown). Similarly, at fruit set, A for BAS leaves
was greatest, while post veraison ALFE had the highest A. The leaves selected were all
well exposed and measured at optimal environmental conditions. This apparent
contradiction between the potted and ﬁeld vine response to crop level can be explained
by differences in canopy structure. In the potted vine study there was no canopy shading
and all the leaves were maximally active in respect to photosynthetic activity (although
there were differences between leaf positions). Therefore, response of A was based
largely on the interaction between total leaf area per vine and crop level effects. Field

vines, on the other hand, developed shaded canopy interiors, especially by the end of the

 

 

93

season (Barros, 1991). Shading was greatest in the 0.5 cluster level vines which had
more vigorous vegetative growth. Hunter and Visser (1988) observed that the
photosynthetic contribution of interior canopy leaves was lower than those that were
exposed. This is consistent with the observations of Smart (1985) and others (Smart et
al., 1990; Gaudillere and Carbonneau, 1986) that a vigorous canopy greatly attenuates (i.e.
reduces) light penetration into the canopy interior. I would hypothesize that the
photosynthetically functional leaf area/total sink ratio (expressed as leaf area/total dry wt.
in the potted vine study) was similar for all ﬁeld vine crop levels. The ﬁeld vines for this
study were blocked on vine size (measured as the weight of dormant one year canes at
pruning) and I would anticipate that the relationships described would only be consistent
only for vines within a similar vine class. Further work will be presented in a later paper

to help detail and elaborate on this hypothesis.

Conclusions

There was a seasonal progression in the data presented. One must interpret A _data
carefully. Under the conditions of this study single leaf determinations of A appear useful
only to elaborate localized treatment effects on A. Inference of whole vine response of
A to treatment will likely be in error regardless of the phenophase at the time of
measurement. Further, even whole vine trends in A calculated on a leaf area basis may
not correlate with A determined on a single leaf basis given the differences in correlation

observed at different phenophases in this study.
. I conclude that the vine possesses a balanced system of allocation of photosynthate,

and that throughout the season resources are allocated based on a ranking of sink priority.

 

 

94

Localized photosynthetic ratw may increase with sink stimulus (vegetative or
reproductive). This may be a secondary response to metabolic changes (e.g. leaf area
increases as crop level decreases), which are then balanced through respiratory or other
mechanisms, so that total A per vine is relatively unaffected. This balance of resources
is most evident if one views the partitioning data which indicates that at any time during

the season total dry weight production is the same regardless of the crop level.

 

 

95
I' C' I

Amthor, LS. 1989. Respiration and crop productivity. pp. 44—104. Springer-Verlag.
ISBN 3-540—96938—1.

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durante el periodo vegetativo. Vitis 27:13—20.

Barros, M.T. 1991. Personal communication, unpublished data. Michigan State
University, East Lansing, Michigan, U.S.A.

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level in a high yielding Caragnane vineyard on growth, yield, and wine quality.
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Candolfi-Vasconcelos, M.C. 1990. Compensation and stress recovering related to leaf
removal in Vitis vinifera. PhD dissertation. Swiss Federal Institute of
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starch reserves of the wood as a function of leaf removal in Vitis vimfera.
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356.

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(2):212-213.

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Downton, WJ.S., W.J.R. Grant and B.R. Loveys. 1987. Diurnal changes in the
photosynthesis of ﬁeld-grown grapevines. New Phytol. 105:81—88.

Eibach, R. and G. Alleweldt. 1983. Einﬂuss der Wasserversorgung auf Wachstum,
Gaswechsel und Substanzproduktion Traubentragender Reben. 1. Das vegetative
Wachstum. Vitis 22:231—240.

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Substanzproduktion. Vitis 24:183-198.

 

 

96

Flow, J.A. and AN. Lakso. 1989. Environmental and physiological regulation of
photosynthesis in fruit crops. Hort. Rev. 11:111-157.

Gaudillere, J .P. and A. Carbonneau. 1986. Training system and photosynthetic activity
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partitioning in sour cherry and plum. Ph.D. Dissertation. Mich. State University,
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development and quality of Italia glasshouse table grapes. Am. J. Enol. Vitic.
40:130-134.

Kliewer, W.M. and RJ. Weaver. 1972. Effect of crop level and leaf area on growth,
composition and coloration of 'Tokay' grapes. Am. J. Enol. Vitic. 23:172-177.

Koblet, W. 1977. Translocation of photosynthate in grapevines. In: Proc. OIV Symp.
on the Quality of the Vintage. pp. 45— 51. OVRI, Stellenbosch, South Africa.

 

 

 

97

Koblet, W. 1987. Effectiveness of shoot tipping and leaf removal as a means of
improving quality. Acta. Hort. 206:141-156.

Kriedemann, P.E., W.M. Kliewer and J.M. Harris. 1970. Leaf age and photosynthesis
in Vitis vinifera L. Vitis 9:97—104.

Kriedemann, RE. and RE. Smart. 1971. Effects of irradiance, temperature and leaf
water potential on photosynthesis of vine leaves. Photosynthetica 526-15.

Neales, T.F. and L.D. Incoll. 1968. The control of leaf photosynthesis rate by the level
of assimilate concentration in the leaf: a review of the hypothesis. Bot. Rev.
34:107-125.

Niimi, Y. and H. Torikata. 1979. Changes in photosynthesis and respiration during berry
development in relation to the ripening of Delaware grapes. J. Japan Soc. Hort
Sci. 47:448-453.

Pandy, R.M. and HG Farmahan. 1977. Changes in the rate of photosynthesis and
respiration in leaves and berries of Vitis vinifera grapevines at various stages of
berry deve10pment. Vitis 16:106-111.

Pratt, C. 1971. Reproductive anatomy in cultivated grapes - a review. Am. J. Vitic.
Enol. 22:92-109.

Quinlan, J .0. and RJ. Weaver. 1970. Modification of the pattern of the photosynthate
movement within and between shoots of Vitis vinifera L. Plant Physiol. 46:527-
530.

Reynolds, A.G., R.M. Pool and LR. Mattick. 1986. Effect of shoot density and crop
control on‘g‘rowth, yield, fruit composition and wine quality of 'Seyval blanc'
grapevines. J. Amer. Soc. Hort. Sci. 111:55— 63.

Reynolds, A.G. and DA. Wardle. 1989a. Impact of various canopy management
techniques on growth, yield, fruit composition and wine quality of
Gewurtztraminer. Am. J. Enol. Vitic. 40:121—129.

Schaffer, B., J.A. Barden and J.M. Williams. 1986. Whole plant photosynthesis and
dry—matter partitioning in fruiting and deblossomed day neutral strawberry plants.
J. Amer. Soc. Hort. Sci. 111:430-433.

Smart, RE. 1985. Principles of grapevine canOpy microclimate manipulation with
implications for yield and quality. A review. _ Am. J. Enol. Vitic. 36:230-239.

 

98

Smart, R.B., J.K. Dick, I.M. Gravett and B.M. Fisher. 1990. Canopy management to
improve grape yield and wine quality — principle and practices. S. Afr. J. Enol.
Vitic. 11:3—17.

Steel, R.G.D. and J .H. Torrie. 1980. Principles and procedures of statistics. McGraw—
Hill. ISBN 0-07—060926-8.

Weaver, RJ. and R.M. Pool. 1969. Effect of various levels of cropping on Vitis vinifera
grapevines. Am. J. Enol. Vitic. 20:185—193.

Williams, LE. 1986. Net CO2 assimilation of Vitis vinifera L. leaves as affected by
alterations in source/sink relationships of the vine. Proc. International Workshop
on Regulation of Photosynthesis in Fruit Crops. T.M. Dejong (ed.). pp. 35—40.
University of California, Davis.

Wolf, T.K., B.W. Zoecklein, M.K. Cook and CK. Cottingham. 1990. Shoot topping and -
ethephon effects on White Riesling grapes and grapevines. Am. J. Enol. Vitic.
41:330-341.

Yang, Y.S. and Y. Hori. 1980. Studies on retranslocation of accumulated assimilates in
'Delaware' grapevines. II. Retranslocation of assimilate accumulated during the
previous growing season. Tohoku J. of Agr. Res. 312109-119.

 

 

CHAPTER HI

Inﬂuence of Crop Level on Grapevine Photosynthesis and Dry Matter Partitioning
at Several Stages of Phenological Development. II.

Vine Morphology, Yield, Fruit Composition, and Dry Matter Partitioning

 

 

 

Abstract

The inﬂuence of crop level (0, 1, 2, 4, or 6 clusters/vine) in two—year—old, own
rooted Seyval grapevines grown in 20 L pots was studied. Whole vine assimilation
(WVA) and several vegetative and reproductive indices were measured at four
phenological stages of development (phenophases). Vines were also partitioned into fresh
and dry weight components at several phenophases. Yield and berries/vine were
correlated with clusters/vine. Leaf area/vine, leaf size, shoot length, node number,
intemode length, berries/cluster, and cluster weight were inversely related to crop level.
Vines lost an average of 31.5% total fresh weight between planting and bud burst. Leaf
area differences were evident as early as fruit set, but differences in dry weight
partitioning did not become evident until mid-season. Leaf and shoot dry weight were
inversely related and fruit dry weight, positively correlated with crop level. Root dry
weight was inversely related to crop level only at harvest. Sugar accumulation and shoot
maturation were delayed by high cr0p levels. WVA/vine was usually not related to crop

level, but was negatively correlated at midseason.

Introduction
This paper is the second in a series detailing investigations into the inﬂuence of crop
level and phenophase on carbon assimilation (A) and partitioning of Seyval (S.V. 5276)

grapevines. Seyval is a large clustered cultivar with a tendency to overproduce, making

100

 

 

   

101

Seyval excellent for investigating the inﬂuence of cr0p level on physiological and
morphological factors.

Manipulations of cr0p level result in an alteration of the source/sink relationship.
High cr0p levels may delay fruit (Jackson, 1986; Kliewer and Weaver, 1972; Morris and
Cawthon, 1982; Weaver and Pool, 1969) and wood maturity (Howell, 1989).
Overcr0pping is also associated with reduced levels of carbohydrates in roots (Weaver
and McCune, 1960; Weaver and Pool, 1969) and may adversely affect winter cold
hardiness (Howell et al., 1978; Howell, 1989).

The ability of the vine to balance the allocation of carbohydrates produced during
photosynthesis is an important consideration when viewing the vine as a whole vine
system. Changes in morphology accompany changes in carbon allocation if the vine has
sufficient time to adjust to alterations in source/sink relationships (Candolfi-Vasconcelos,
1990; Candolfi-Vasconcelos and Koblet, 1990; Koblet, 1987).

High crop levels are inversely related to shoot growth, leaf size, and leaf area
(Eibach and Alleweldt, 1983; Bravdo et al., 1984). Although vines with higher crop
levels allocate a greater proportion of their carbon resources to fruit production, total dry
matter production is similar between differentially fruited vines at harvest (Eibach and
Alleweldt, 1983).

Low leaf area to fruit ratios enhance photosynthetic activity when measured at a
single leaf position (Candolfi-Vasconcelos, 1990; Chaves, 1984; Eibach and Alleweldt,
1984; Hofacker, 1978) (for reviews of this subject see Flore and Lakso, 1989; Herold,
1980; Neales and Incoll, 1968). Sink priority changes as the season progresses with the

clusters gradually increasing their ability to attract carbon after fruit set (Balcar and

 

 

 

102

Hernandez, 1988; Hale and Weaver, 1962), and subsequently their ability to enhance
single leaf photosynthetic rate (Candolfi-Vasconcelos, 1990; Hunter and Visser, 1988; see
Chapter 11).

Measuring each of these important responses quantifies discrete portions of the vine
response to crop level. However, the individual response (eg. single leaf A or yield) is
not isolated, but rather generated from a complex set of interacting physiological and
morphological factors. Measuring the response of a portion of the plant may not
accurately reﬂect the whole vine response. Assimilation when measured on a whole plant
basis does not correlate well with single leaf rates of A (SLA) (Shaffer et al., 1986; see
Chapter I, II). Similarly, yield does not correlate well with total vine dry weight at
harvest (Eibach and Alleweldt, 1983).

In Chapter II, I discussed the seasonal relationships between SLA and WLA. In this
paper, crop level effects on yield, fruit composition, vine morphology and dry matter
partitioning will be discussed. I will relate these results to the previous investigations of

A.

Materials and Methods
E] II 'I 111' I ..
Two year old, own rooted, Seyval gapevines gown in 20 liter pots were used for
this study. Soil used and vine maintenance were described in Chapter II.
Vines were trained to two vegetative shoots per vine and crop level adjusted to 0,
1, 2, 4, or 6 clusters per vine. Clusters were borne on defoliated spurs to allow large

cluster numbers to be generated without additional leaf area. Details of this vine

 

 

 

103

architecture system are described in Chapter II and Appendix I. To eliminate variances
in intra-vine shading which could have been created by a differential response of lateral
shoot gowth to crop level (Candolfi-Vasconcelos and Koblet, 1990), laterals were

removed weekly. Vegetative terminals were never cut.

3 . 'l . l I
WVA and SLA were measured using an open gas exchange system in chambers
previously described in Chapter I and II. Environmental conditions and measurement

parameters were also described in Chapter II.

MomhongLandﬁaneMammiQn

Shoot length, node number and leaf area per vine were measured at four
phenophases: fruit set, mid-season, veraison, and harvest. Leaf area was determined
once leaves were removed from the vines for partitioning. Wood maturity was
determined subjectively on two occasions. A node was considered mature if the bud
scales and periderrn at, and basal to that node had browned.

Root system development was also subjectively rated on a scale from 1—5, where
class 1 was poor quality (i.e. small root systems, with few actively gowing roots) and

class 5 was very good quality with many vigorous new roots. These ratings were made

after partitioning, without knowledge of treatment.

 

 

     

104

tt‘llC ”3.: ..

Fruit was harvested on September 18, 1989. Clusters and berries were counted and
weighed. All the clusters on a vine were sampled and a composite SO berry sample
consisting of apical berries (i.e. distal berries on the cluster rachis) was collected, weighed
and frozen for later analysis. Analysis of percent soluble solids, titratable acidity, and pH

were made using standard methods (Amerine and Ough, 1988).

DIIE'"

Vines were partitioned into vegetative and reproductive components on four
sampling dates during the season: bud burst, fruit set, veraison, and harvest. Vine
components were separated as follows: leaves; clusters; current year shoots; 2 year and
older wood; and roots. Using the soil line as the demarcation point between wood and
roots is unacceptable in potted vines, since soil and planting depth may vary somewhat
from pot to pot. Therefore, vines were divided at a point 2 cm above the ﬁrst node
where roots originated. All components were oven dried at 66°C until no further loss of

moisture was observed to determine dry weight.

E' ”1' ”UNI.

The experimental design was a randomized complete block design with vines
blocked on initial vine fresh weight as an estimate of vine size. Regession analysis was
most apprOpriate for comparisons between crop level at the individual dates (Chew,
1976). Crop level can be expressed as clusters per vine, berries per vine or total fruit

yield per vine. Clusters and berries per vine may actually be considered as components

 

   

105

of the total yield per vine. Linear and quadratic regessions using clusters per vine,
berries per vine, and yield per vine as independent variables were calculated for the
dependent variables of interest. Statistics were calculated using the MSTAT-C and

PLOTIT statistical computer packages.

Results and Discussion

Yield per vine and berries per vine were significantly higher for those vines having
geater cluster numbers at both veraison and harvest (Table 1); Berries per vine and yield
were strongly correlated, indicating that berries per vine was an important component of
total yield. There have been reports that high crop levels negatively inﬂuence berry
weight (Kliewer and Weaver, 1972; Reynolds et al., 1986) but this varies with cultivar
(Bravdo et al., 1984; Weaver and Pool, 1969) and year (Reynolds et al., 1986). Berry
weight was not affected in an earlier study with Seyval (see Chapter I) nor during this
study. Fruit set (considered here as berries per cluster) was inversely correlated with
clusters per vine (Table 1). Clusters on the 6 cluster per vine treatment carried only 30%
of the berries per cluster compared to the l-cluster per vine treatment (Table 1). Intra—
vine competition for carbohydrates and gowth substances by both fruiting (Weaver and
Pool, 1969) and vegetative sinks (Coombe, 1973) can have a negative impact on fruit set.
Intra—vine competition at higher cluster numbers per vine may have been exacerbated by
the vine architecture system used in this study.

The reduced cluster compactness I observed at high cr0p levels may have some

practical application. Flower cluster thinning is a standard cr0p control recommendation

 

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107

for Seyval in Michigan (Reynolds et al., 1986). Late thinned (post fruit set) clusters tend
to be less compact and less susceptible to bunch .rot (Bonytis cinera and other secondary
infections such as Acetobacter 3p.) (Reynolds et al., 1986).

Fruit composition was also affected by cr0p level with higher cr0p levels tending
to delay maturity (Table 2). This would concur with other workers (Morris and Cawthon,
1982; Reynolds et al., 1986; Weaver and Pool, 1969). The response was not consistent
for all independent variables tested. Titratable acidity was not signiﬁcantly different at
any date. Sugar accumulation was the only compositional index consistently correlated

with at least one cr0p level parameter past veraison through harvest (Table 2).

Win

No differences in shoot gowth were observed between cr0p levels at fruit set (Table
3). New shoot gowth in the spring is dependent on carbohydrate remobilized from
storage reserves in the perennial portions of the vine (Koblet and Perret, 1982; Scholefield
et al., 1978; Yang and Hori, 1979). Shoot gowth (measured as nodes per shoot) between
bud burst and anthesis has been shown to be similar within the same vine vigor class
(Pratt and Coombe, 1978). Moreover, clusters do not become strong sinks until post fruit
set (Hale and Weaver, 1962; Chapter II). Therefore, significant differences in vine vigor
as inﬂuenced by cr0p level would not have been established until later in the season.

Total shoot gowth, nodes per vine and intemode length were inversely related to
cr0p level as early as midseason (Table 3). This relationship continued through harvest,
when total shoot length for the 6-cluster vines was nearly 40% less than defruited vines

(Table 3). Even 1 cluster per vine reduced shoot length by a factor of 20%. Intemode

 

 

 

 

 

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110

length was similarly affected. The relationship was only slightly improved using the
quadratic comparisons (Table. 3). Eibach and Alleweldt (1983) observed similar
reductions in shoot gowth on bearing vines at low yields.

Current cultural recommendations suggest that young vines or weak vines be
defruited in order to increase vine size (measured as kilogams of dormant cane prunings)
(G.S. Howell, personal communication). Total fresh shoot weight is roughly equivalent
to vine size and was increased by 37% and 100% when comparing 1—cluster vines and
6-cluster vines with defruited vines at harvest, respectively (data not shown).

Shoot maturity was-delayed as crop level increased (T able 4). The sequence of
periderm browning in Seyval at each speciﬁc node was strongly inﬂuenced by sink
demand of the cluster. Normally, the bud scales on the auxiliary bud began to brown
ﬁrst. When this bud was nearly mature (completely brown), the intemode immediately
distal to the node bearing the bud had begun to turn light brown and the intemode
immediately below this node was already dark brown (although in some cases the entire
periderm may not have completely matured at that point). Several nodes below
(depending on shoot vigor), the periderm was completely mature. Even when the entire
bud and node appeared to be completely mature, periderm browning at the petiolar point
of attachment was sometimes delayed. Maturation of nodes bearing clusters was often
delayed, with several nodes apical to the cluster bearing node already matured.

Although 6—cluster vines matured a similar percentage of their total nodes as
defruited vines, the absolute number of mature nodes is the critical value when
considering winter cold hardiness and potentially fruitful buds for producing next season's

fruit (Howell, 1989).

 

 

111

Table 4. Inﬂuence of crop level on cane maturation‘ of Seyval gapevines.

 

 

 

Clusters/ Total Mature Nodes Percent total nodes
vine 9/15/89 9/‘22/89y mature on 9/22/89
6 11.7 30.7 53.4
4 14.0 32.7 53.6
2 16.3 36.0 56.1
1 16.3 35.3 53.5
0 21.0 38.7 51.4
Linear’
clusters —0.45" -0.41" ns
berries -0.36"' -0.38" ns
yield -0.32"‘ -0.30* ns
Quadratic
. clusters -0.47"' -0.41"‘ ns
berries ns ns ns
yield ns ns ns

 

zMaturity rating based on browning of the periderm (see text).

’Fruit harvested September 18, 1989.

‘Independent variables; r2 significant at the 5% (*), 1% (") level or not significant (ns).

 

 

 

 

   

112

We

Increases in A per unit leaf area are associated with higher cr0p levels (Candolﬁ-
Vasconcelos, 1990; Chaves, 1984; Hunter and Visser, 1988; Kaps and Cahoon, 1989) and
are inversely related to changes in leaf area (Choma et al., 1982; Schaffer et al., 1986).
Thus leaf area is an important morphological parameter related to photosynthetic
efﬁciency. Leaf area per vine increased throughout the season for all cr0p levels, but at
a geater rate for l-cluster vines (Figure I). The inﬂuence of cr0p level on leaf area was
already evident by fruit set (Figure I; see Chapter 11), suggesting that leaf area is more
sensitive to cr0p level effects than is shoot gowth. Leaves expand quickly after
unfolding if environmental conditions are favorable, becoming net exporters of assimilate
as early as 30-50% full expansion (Hale and Weaver, 1962; Koblet, 1977). Thus they
are less reliant on stored carbohydrates than shoots (prior to fruit set), and more likely
inﬂuenced by competition with developing fruiting sinks. The resmnse in this study was
consistent with earlier reports that cr0p level is inversely related to leaf size (Smart,
1985), especially if only fully expanded leaves are considered (see Chapter I). Seasonal
changes in maximum leaf size also occur (Hale and Weaver, 1962). Mean leaf size for
all crop levels increased at midseason and veraison and then decreased (i.e. fully
expanded basal leaves and fully expanded leaves that emerged after veraison were smaller
than those which emerged mid-season) (data not shown). This response concurs with
that observed by Hale and Weaver, 1962.

Speciﬁc leaf density has been positively correlated with A (Herold, 1980), but there

were no differences due to crop level in this "or an earlier study (see Chapter I).

 

 

 

 

 

113

Figure I. Inﬂuence of crop level on leaf area accumulation at several phenophases in

Seyval gapevines.

 

 

 

 

 

114

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DNE"'

Initial vine ﬂesh weight was measured prior to planting (May 10, 1989) and then
used as a blocking variable. Vine size classes are shown in Table 5. Two weeks post
ﬂuit set I determined that vine vigor and cluster size were unacceptable in the smaller
vine size classes, so they were dropped ﬂom the study. Only vines ﬂom the largest three
vine size classes were used for analysis or A measurements throughout the study. Data
for all classes are shown in Table 5 for comparison.

Vines lost an average of 31.5 % ﬂesh weight between planting and bud burst (May
23, 1989), evidence of respiratory losses that occur during this time ﬂame (Eifert and
Eifert, 1963). The magnitude of this loss was not affected by vine size class. Large
vines had a greater percentage of their carbohydrate stores in the root system than the
smaller vines (Table 5). This difference was significant only if the largest three vine size
classes were compared.

Total dry weight comparisons between crop levels were not signiﬁcantly different
at any phenophase (Fables 6:9), but patterns of allocation were affected for several
components. By ﬂuit set only ﬂuit dry weight was affected, and was largely inﬂuenced
by cluster number (Table 6). Even though leaf area was negatively correlated with
clusters per vine at ﬂuit set (r2=-0.53, sig. at the 5% level) (see Chapter I), these
differences did not translate into leaf dry weight differences, given the low speciﬁc leaf
density at that time (mean=4.18 mg/cm’).

By August 22, 1989, differences in percent of total dry weight allocated to both
leaves and shoots were beginning to emerge (Table 7). However, differences in the.

percent of total dry matter allocated to the storage sinks (wood and roots) were not yet

 

 

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117

 

Table 6. Inﬂuence of cr0p level on dry weight partitioning of Seyval grapevines.

Partitioned at ﬂuit set, July 1, 1989.2

 

 

 

Clusters/ Percent of Total Total dry
vine Fruit Leaf Shoot Wood Root weight (g)
6 2.7 8.8 8.3 18.9 61.3 54
4 2.0 10.0 8.6 26.3 53.2 50
2 1.0 11.4 9.0 24.2 54.4 48
1 0.7 11.9 8.6 20.6 58.3 53
Linear’
clusters 0.84 ns ns ns ns ns
berries ns ns ns ns ns ns
yield 0.34 ns ns ns ns ns
Quadratic .
clusters 0.87" * * ns ns ns ns ns
berries 0.51" ns ns ns ns ns
yield 0.48"" ns ns ns ns ns

 

'5 days post full bloom date.

’Independent variables; r2 significant at the 5% (*), 0.1% (*") level or not significant (n.s.).

 

 

 

 

 

 

118

 

Table 7. Inﬂuence of crop level on dry weight partitioning of Seyval grapevines.

Partitioned at veraison, August 22, 1989.2

 

 

 

Clusters/ Percent of Total Total dry
vine Fruit Leaf Shoot Wood Root weight (g)
6 32.3 16.6 11.0 11.3 28.8 207
4 28.9 17.1 13.9 9.6 30.5 201
2 25.0 18.3 13.6 12.1 31.0 193
1 15.1 21.0 19.2 9.7 35.0 208
Linear’
clusters 0.55" -0.33* ns ns ns ns
berries 076*" -0.73""' -0.78*" ns ns ns
yield 0.56" -0.69"* «0.60" ns ns ns
Quadratic
clusters 0.63“ -0.56* ns ns ns ns’
berries 0.71" -0.63* -0.68" ns ns ns
yield 0.71" -0.72" -0.70" ns ns ns

 

'Berry soluble solids = 10° Brix on August 18, 1989.

’Independent variables; r2 significant at 5% (’), 1% C"), 0.1% (*") or not signiﬁcant (ns).

 

 

 

119

 

Table 8. Inﬂuence of crop level on dry weight partitioning of Seyval grapevines.

Partitioned at harvest, September 22, 1989.2

 

 

 

Clusters/ Percent of Total Total dry
vine Fruit Leaf Shoot Wood Root weight (g)

6 43.0 11.1 10.6 8.8 27.0 276

4 41.0 12.7 12.2 8.0 26.0 306

2 28.0 14.8 15.9 8.0 33.0 295

1 22.0 15.1 17.0 11.1 35.0 299

0 0 19.1 29.8 10.4 41.0 286

Linear’
clusters 076*" —0.68""' -0.63"* ns -0.71"* ns
berries 0.96"" -0.84"* —0.85"'" ns -0.87"'" ns
yield 0.98"" -0.82"" -0.8 "* ns -0.86*" ns

Quadratic. ..
clusters 090"" -0.73"* -0.78""‘ ns -0.82*" ns
berries 0.97"" -0.84"'" -—0.90"'" ns -0.87"'" ns
yield 098*" -0.83"'" -0.89"" ns —0.88"'" ns

 

zFruit harvested September 18, 1989.

’Independent variables; r2 significant at the 0.1% level or not significant (n.s.).

 

 

 

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121

sigﬁficant (Table 7,9). The correlation between crop level parameters and dry weight
components was slightly improved if the quadratic response was considered. There is
little movement of labelled assimilate out of shoots into the trunk or roots prior to fruit
set (Balcar and Hernandez, 1988; Hale and Weaver, 1962; Yang et al., 1980). Further,
significant movement of assimilate from leaves to the roots does not occur until post
veraison (Scholefield et al., 1978; Yang et al., 1980). It is not surprising then, that I did
not observe differences in dry weight allocations to the roots until harvest (Table 8). I
did, however, observe differences in root quality as early as veraison (Table 10), although
the difference appeared to be mostly between the 1 cluster vines and the rest of the crop
levels. Similarly, at harvest, the best quality root systems were found on defruited vines
(Table 10). There were also differences between moderately cropped (1 and 2 cluster)
and higher cropped (4 and 6 cluster) vines. Yang et al. (1980) using potted 'Delaware'
vines, recovered nearly 40% of 1“C fed to leaves at ﬂowering from the roots, showing
that root activity can function as a moderately strong sink at that time.

Sufﬁcient leaf area (7-14 cm’) per gramJof fruit must be retained to insure adequate
fruit ripening (Jackson, 1986; Kingston and Epenhuijsen, 1989; Kliewer and Weaver,
1972; Smart et al., 1990). Inﬂuences of crop level on this ratio developed by midseason
(Table 11). Differences were based largely on emerging trends in leaf area accumulation,
since yield for this comparison was constant across dates.

Leaf area per gram of fruit is not directly representative of the relationship between
leaf area accumulation and total vine growth. The much smaller differences between crop
level expressed by leaf area per total dry weight would seem to be more representative,

of the whole vine system (Table 12). But, a comparison of the three leaf area ratios

 

 

 

122

 

 

Table 10. Inﬂuence of cr0p level on the root system development in Seyval grapevines

at several phenophases, 1989.

 

 

 

Clusters/ Root system class
vine Fruit setz Veraison Harvth
6 2.8’ 2.3 1.8
4 3.0 2.7 1.8
2 3.0 2.5 2.8
1 2.8 4.5 2.7
0 NA. NA. 4.5
Linear‘
clusters ns ns -0.41"
berries ns —0.40* -O.55"*
yield ns -0.33"' -0.51"‘"
Quadratic
clusters .-0.57"”" ns ns
berries -O.58" ns ns
yield -0.56" ns ns

 

zFruit set: 5 days post full bloom date. Veraison: fruit soluble solids = 10° Brix on 8/17/89.

’Ratings are subjective, conducted without knowledge of treatment on a scale of 1-5 where 1 =
poor, few active roots; 5 = good root system with many vigorous new roots. Comparisons
between crop level are appropriate only for each given date. Direct comparisons between dates

do not apply.

‘Independent variables; r2 = signiﬁcant at the 5% (’), 1% ("), 0.1% (”*) level or not
signiﬁcant (ns); NA (not available).

 

 

123

Table 11. Inﬂuence of crop level on the relationship between leaf area at several

phenophases and fresh fruit yield at harvest of Seyval grapevines.

 

Leaf area (cm2)/fruit (g)

 

 

Clusters/ Fruit setz Midseason Veraisony Harvest
vine 6/30/89 8/26/89 8/18/89 9/18/89
6 2.5 5.2 8.2 7.2
4 2.1 7.1 9.4 9.5
2 3.5 9.8 10.6 12.9
1 4.4 15.0 18.9 18.9
Linear‘
clusters ns -0.52* * —0.46" -0.42"' "
berries ns —0.61" -0.65*** -O.36"
yield ns -0.78"" —0.80"* -0.49*"
Quadratic ~
clusters ns —0.58“ £0.55* —0.66"‘"
berries -0.82" -O.84"* —0.91"* -0.83*"
yield -0.96*" -0.92"* —0.72"‘* —0.889""‘

 

‘4 days post full bloom date.

yFruit soluble solids = 10° Brix.

‘Independent variables; r2 significant at the 5% (‘), 1% C”), 0.1% ("*) levels or not signiﬁcant

(ns).

 

 

 

124

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125

expressed in Tables 11 and 12, shows similar trends in significance (deSpite large

numerical differences).

B l . l . B E I E . . .
I had previously observed that localized effects of crop level on SLA become

evident as early as fruit set (see Chapter II). This coincides with reductions in leaf area
that occur in response to increasing cr0p level discussed in this paper. Candolﬁ-
Vasconcelos (1990) has recently shown that partially defoliated vines compensate for the
reduction in leaf area by increasing both stomatal and mesophyll conductance. She
concluded that compensation due to the mes0phyll component was primarily responsible
for increased A and that enhanced carboxylation efﬁciency of ribulose—1,5-bisphosphate
carboxylase/oxygenase was likely involved although this conclusion is controversial (J A
Flore, personal communication). This interpretation was based on the relationship
between internal C02 concentration (C) and A, which assumes a homogenous stomatal
response (Daley et al., 1989). If stomatal response to cr0p level is heterogenous, as .
shown recently for water stress (Downton et al., 1988) and for exogenous ABA
applications (Daley et al., 1989), then leaf compensation to reductions in leaf area may,
in fact, be due primarily to increased somatal conductance.

Herold (1980) points out that artiﬁcial manipulations of source-sink relationships
may affect hormone synthesis and availability, (i.e., increases in root/shoot ratios may
increase the availability of cytokinins to the remaining sinks). Root/shoot ratios were
highest for the 6 cluster vines at harvest (data not shown), suggesting the possibility for

higher concentrations of cytokinin in the leaves of those vines. Exogenously applied

 

 

 

 

 

 

 

126

cytokinins act rapidly to Open stomates (Incoll and Jewer, 1987), providing a possible
explanation for the compensatory effect measured by Candolfi-Vasconcelos (1990).
Roper and Williams (1988) have also suggested that abscisic acid (ABA) and gibberellin
(GA) may be involved in regulating photosynthetic rate adjustments to source/sink
changes. They hypothesized that accumulations of ABA in the leaves (following girdling)
may be responsible for reductions in A and further, that exogenously applied GA could
partially negate the effects of ABA. However, they did not discuss the stimulatory effect
that GA can have on vegetative growth (W inkler et al., 1974). Herold (1980) concluded
that the integration between sink activity, hormones and photosynthetic rate has not been
conclusively shown.

Though compensation in SLA was evident, WVA/V showed a different trend
(Figure II). The only significant differences between crop level occurred at midseason,
when WVA/V was inversely related to cr0p level. This occurred when the grapevine was
in a strong vegetative grth phase. It is at midseason that shoot growth differences
began to emerge (Table 3), as well as indications that root activity was negatively affected
by crop level (Table 10).

I have contended that differences in the respiration rate that are observed for
different tissues (Amthor, 1989; Pandy and Farmahan, 1977) may help explain the lack
of correlation between SLA and WVA (see Chapter I, II). Patterns of dry matter
allocation observed in this study tend to support that view.

The changes in hormone distribution and availability discussed by Herold (1980)
may be as strongly related to determining sink strength and hence reallocation of

assimilates as they are to controlling photosynthetic rate directly.

 

 

l

 

 

 

 

127

Figure II. Inﬂuence of crop level on whole vine assimilation (per vine basis) at several

phenophases for Seyval grapevines.

 

 

 

128

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129

Conclusions

There was a seasonal progression in the data presented. We conclude that the vine
possesses a )alanced system of allocation of photosynthate, and that throughout the season
resources a “e allocated based on a ranking of sink priority. Cr0p level signiﬁcantly
affected vi 1e morphology, most importantly, reducing the leaf area available for
producing l hotosynthates.

In efft ct, fruit was produced at the expense of vegetative structures, since total dry
matter prod lCtiOll was not affected by crop level. On a localized basis, the reduced leaf
area functic red at a higher photosynthetic rate, but an internal mechanism balanced whole

vine respon e so that total A per vine was relatively unaffected.

 

 

 

     

130
I . C. l

Amerine, M.A. and C. Ough. 1988. Methods of must and wine analysis. 377 pp. ISBN
0—471-62757—7.

Amthor, LS. 1989. Respiration and crop productivity. pp. 44-104. Springer-Verlag.
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Balcar, J. and J. Hernandez. 1988. Translocacién de fotosintatos en sarmientos de la vid
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level in a high yielding Carignane vineyard on wine quality. Am. I. Enol. Vitic.
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Candolfi—Vasconcelos, M.C. 1990. Compensation and stress recovering related to leaf
removal in Vitis vinifera. Ph.D. dissertation. Swiss Federal Institute of Technology,
Zurich. 59 pp.

Candolfi, Vasconcelos, M.C. and W. Koblet. 1990. 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.

Chaves, M.M. 1984. Photosynthesis and assimilate partitioning in fruiting and
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Chew, V. 1976. Comparing treatment means: A compendium. HortScience 11.348-

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Coombe, B.G. 1973. Regulation of set and development of the grape berry. Acta
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Daley, P.F., K. Raschke, J.T. Ball and J.A. Berry. 1989. T0pography of photosynthetic
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Downton, WJ.S., B.R. Loveys and W.J.R. Grant. 1988. Non-uniform stomatal closure
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Eibach, R. and G. Alleweldt. 1985. Einﬂuss der Wasserversorgung auf Wachstum,
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Eifert, J. and A. Eifert. 1963. Maximum of starch during Spring in the woody plants
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Flore, J.A. and AN. Lakso. 1989. Environmental and physiological regulation of
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Hale, CR. and P.J. Weaver. 1962. The effect of developmental stage on direction of
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Howell, GS. 1989. Cultural manipulation of vine cold hardiness. Proc. Second Intl.
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Jackson, DJ. 1986. Factors affecting soluble solids, acid, pH, and color in grapes. Am.
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133

ROPer, T.R. and LE. Williams. 1989. Net assimilation and carbohydrate partitioning of
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'Yang, Y.S. and Y. Hori. 1979. Studies on retranslocation of accumulated assimilates in
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Yang, Y.S., Y. Hori and R. Ogata. 1980. Studies on retranslocation of accumulated
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CONCLUSIONS

134

 

 

The data presented in this dissertation lead me to conclude that crop level does not

have a direct effect on WVA. Rather, the effect is indirect, mediated initially through
allocation of assimilate to meet carbon demands. This results in morphological changes
which lead to a localized physiological response. The vine represents a balanced system,
in which carbon is allocated in response to changing sink demand.

There was a seasonal progression in vine response. Significant relationships in dry
matter allocation patterns evolved as the season progressed. Initially, at fruit set, only
current season components were significantly inﬂuenced by crop level, but later, near
harvest, storage tissues were similarly affected. In effect, fruit was produced at the
expense of vegetative structures, since total dry matter production was not affected by
crop level.

SLA was affected by both leaf age and phenophase and was positively correlated
with crop level. Although the contribution due to crop level components was relatively
small, it was statistically significant. On a localized basis, the reduced leaf area present
on the higher crop level vines functioned at a greater photosynthetic rate, but an internal
mechanism balanced whole vine response so that WVA/V was relatively unaffected.
WVA appeared to respond more to total vine sink activity. This was evidenced by the
signiﬁcant negative correlation with crop level observed at mid—season. This factor,
combined with the relatively low r2 values observed for correlations of SLA and crop
level, suggest further comparisons using both vegetative and reproductive components

might better explain vine response of A to sink activity.

135

 

 

 

136

There appeared to be no relationship between SLA and WVA/V. I would conclude
that measurements of SLA are only useful for describing the localized response of vine
A to source/sink adjustments, and should not be used to infer whole vine response. There
are several factors which could cause values to differ between SLA and WVA
measurements. Among these are: 1) angle of inclination to the sun. Leaf angle was
optimized for the single leaf measurements but no adjustments were possible during
whole vine determinations. Assimilation is optimized when the leaf blade is
perpendicular to the sun's rays but does not decline dramatically until the angle of
inclination is greater than 60° (Smart, 1974a; see literature review for citation). Although
I did not measure leaf angle, my observation of these vines leads me to conclude that this
was not a major cause of differences between SLA and WVA; 2) respiration of plant
tissues other than the leaf being measured is not considered during SLA measurements,
but may affect gas exchange measurements in a whole vine chamber. Unfortunately, I
did not consider this possibility until WVA failed to show differences to crop level on a
seasonal basis; and 3) the variation in leaf age nor the inﬂuence of phyllotaxy for a given _
plant system are considered for STA, but may inﬂuence WVA. The above factors require
further study to accurately determine which, if any, inﬂuence comparisons between SLA
and WVA.

The hypothesis discussed in Chapter H concerning functional leaf area in ﬁeld vines
with shaded canopies may have some practical implications as to how we interpret canopy
management studies. Further whole vine studies of ﬁeld grown vines should help
elucidate the interactions between crop level, morphology and A, and may help explain

the inconsistent SLA response reported by different researchers (see Chapter II).

 

 

137

As viticulturists, it would be useful to determine which component of yield (either
clusters per vine or berries per vine) is most important in determining vine response to
crop level. Although the data presented in this dissertation are not conclusive, they are
suggestive, if one views trends in significance observed for the different correlations
between these crop level parameters and the various dependent variables. In general
shoot grth parameters and photosynthesis were most responsive to clusters per vine,
yet leaf area appeared most signiﬁcantly correlated with berries per vine. Response of
dry matter components varied, but early in the growing season, clusters per vine were
important, and by harvest total yield and the berries per vine component of yield appeared
most important. Total yield was highly correlated with berries per vine which can be
inﬂuenced at fruit set by environmental as well as cultural factors. Further analysis of
the vine architecture data presented in Appendix I may help resolve this question.

Lastly, based on the factors discussed in this dissertation, I would reiterate that
caution must be used when interpreting single leaf photosynthesis measurements. While
they accurately reﬂected the localized changes in SIA, they did not have any predictable

correlation to the whole vine response.

 

 

 

 

 

 

 

 

APPENDICES

 

 

Appendix I

The Inﬂuence of Vine Architecture on Gas Exchange Parameters

and Dry Matter Partitioning in Seyval Grapevines

138

 

 

Summary

We found during our investigations in 1988 (see Chapter I) that it was necessary
to retain 3 shoots per vine in order to generate high cluster numbers per vine. This also
meant an increase in the number of active vegetative sinks (3) compared to the other
treatment vines (2). We wished to design a training system that would allow us to
generate high crop levels without a concomitant increase in vegetative sinks or. leaf area.

We devised a unique vine architecture in which the clusters were borne on spurs
that were separate from the vegetative shoots (Figure 1B). The basic training is described
in the materials and methods section of Chapter II.

We made comparisons between vines trained to our unique architecture and those
trained to a standard 2 shoots per vine (clusters borne on the vegetative shoot) (Figure
1A) at 2 crop levels (2 or 4 clusters/vine). We measured gas exchange parameters at
several node positions, dry matter allocation,‘yield indices and fruit quality of those vines.
There was no difference in the parameters measured between training systems that could
not be associated with total yield differences. Differential response was related more to
crop level than to vine architecture. Fruit set was lower for the spur architecture system
compared to the standard system.

Detailed analysis and discussion will be presented in a separate publication.

139

 

 

140

Figure I. Schematic of A) standard (clusters borne on shoots), and B) Spur

(clusters borne on defoliated spurs) vine architecture.

 

 

 

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Appendix II

Inﬂuence of Crop Level on the Diurnal Response

of Assimilation in Seyval Grapevines

157

 

 

Summary

Downton et al. (1987) demonstrated a clear diurnal response in grapevine
assimilation (A) (a gradual reduction from a peak early in the day), and further, that there
were fruit (sink) induced differences that were maintained through the course of the day.
Whole plant measurements of A are time consuming and must be made over several
hours to include multiple treatments and replicates.

[n 1989, I measured the diurnal response at two alternate phenophases, 2 weeks
post bloom (Figure 1, 2) and veraison (Figure 3, 4). SLA measurements were taken at
2 node positions each date. In 1988, I measured the diurnal response of A for the harvest
phenophase (Figure 5) (see Chapter I).

We observed a response similar to that observed by Downton et al. (1987),
however, early morning rates ofA at veraison and harvest were lower- than mid—day rates

due to cooler early morning temperatures (Fable 1).

158

159

 

Table 1. Diurnal inﬂuence on leaf temy erature at midseason (July 16, 1989), veraison

(August 21, 1989), and harve t (August 28, 1988).

 

 

 

Leaf temperature‘

Hour of day 7/16/1989 8/21/1989y 8/28/1988‘
8 -—— 21.0 17.0
9 25.0 22.0 17.9

10 26.0 24.0 23.4
11 29.0 26.0 24.5
12 29.4 29.0 25.7
13 30.0 28.1 25.5
14 30.5 29.5 26.9
15 30.8 29.1 27.4
16 31.0 30.0 26.9
17 31.5 29.0 27.1
18 30.5 29.0 26.7
19 --- 27.5 26.0

 

‘Mean leaf temperature of all leaves me; ;ured; PFD always above saturation.
’Diumal response measured on two days, ;/19/89 and 8/21/89. Temperatures reported for
8—11 are from 8/19/89; temperatures re} mm for the rest of the day are from 8/21/89.
Early morning temperatures for 8/21/89 were the same as those reported on 8/19/89.
Assimilation reported in Figures 3,4 wa: also measured on those days. TWO days were
required due to cloud cover developing 0 8/19/89 and equiptment problems on 8/21/89.
‘Harvest date in 1988 was August 30; E rvest date in 1989 was September 18.

 

 

 

 

160 l

Figure 1. Diurnal response of grapevine Basal leaf SLA to crop level inﬂuences at

mid-season, measured 2 weeks post bloom.

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162

Diurnal response of grapevine ALFE leaf SLA to crop level inﬂuences at

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163

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at veraison (fruit soluble solids = 10° Brix on August 18, 1989).

 

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Figure 4.

166

Diurnal response of grapevine ALFE leaf SLA to crop level inﬂuences at

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Figure 5.

168

Diurnal response of grapevine SLA to crop level 2 days pre—harvest, August
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