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Michigan Statzs
University

 
 

 

t

This is to certify that the

thesis entitled

CANOPY ARCHITECTURE, LIGHT DISTRIBUTION, AND

PHOTOSYNTHESIS OF DIFFERENT DRY BEAN (Phaseolus
vulgaris L.) PLANT TYPES

presented by

Carlos Antonio Burga Mendoza

has been accepted towards fulfillment
of the requirements for

Ph. D. . cfiop SCIENCE
degree 1n

 

Maj0r professor.

Date é / r

0-7639

 

 

CANOPY ARCHITECTURE, LIGHT DISTRIBUTION, AND PHOTOSYNTHESIS

OF DIFFERENT DR! BEAN (Phaseolus vulgaris L.) PLANT TYPES

 

By

Carlos Antonio Burga Mendoza

A DISSERTATION

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

DOCTOR 0F PHILOSPHY

Department of Crop and Soil Sciences

1978

Iv Afr. _\.,
\ \ -2

ABSTRACT
CANOPY ARCHITECTURE, LIGHT DISTRIBUTION, AND PHOTOSYNTHESIS

OF DIFFERENT DR! BEAN (Phaseolus vulgaris L.) PLANT TYPES

 

By

Carlos Antonio Burga Mendoza

Crop architecture characteristics related to light penetration in
the canopy, crop photosynthesis, and dry weight partitioning were
studied in four dry bean (Phaseolus vulgaris L.) plant types: a) MSU
experimental line 31908, a narrow bush type (CIAT type I), b) cultivar
Seafarer, a normal bush type (CIAT type I), c) cultivar NEE-2, a narrow
erect, short vine type (CIAT type II), and d) MSU experimental line
0686, a determinate but very vigorous vegetative-type (resembling CIAT
type III). Plant spacing (47, 20,, and 9 plants/m2) and light environ-
ments (full and 502 sunlight) were used to modify canopy architecture.

The vertical distribution of the area of green leaves in the crop
profile varied during the course of the growing season. Seafarer
attained its mm at approximately the same plant height, 10 to
30 cm from.the bottom, during the period of 30 to 72 days after
planting (dap). NEP-Z, lines 31908 and 0686 had distribution curves
nearly symmetrical with respect to maximum.LAI at the middle of the
plant height at 30 to 72 dap, thereafter the maximum shifted to higher
plant layers.

Light distribution in the plant canopy changed with plant height

in an exponential manner and fit Bouguer-Lambert's law. Relative light

Carlos Antonio Burga Mendoza

interception was closely associated with LAT and both had similar trends
during plant development. Light penetration was greatest in Seafarer
and lowest in the line 31908. NEP-Z and line 0686 showed intermediate
values. LAI, leaf angle, percent of ground cover, and extinction
coefficient accounted for 99.22% of the variance in light penetration.

Seafarer and NEP-Z could be classified as erectophile and
planophile foliar structure, respectively, using de Wit's system.
Neither Seafarer nor NEP-Z had leavesroriented with more frequency in
or toward any azimuth. Light environments did not affect spatial bean
leaf orientation.

Photosynthesis rates increased from bottom to top leaves of
Seafarer and NEP-Z. Maximum C02 uptake rates for each plant stratum
occurred at the time of initial pod filling. The shade environment
decreased C02 uptake rates but similar trends were observed under
both light environments.

The ontogenetic patterns of dry weight distribution among plant:
organs suggested a movement of materials from leaves to stems to pods.
Similar trends were observed for stem dry weight and starch accumula-
tion in the stems during the growing season. Storage material trans-

location from stems to pods was affected by plant spacing.

To Cesar and Carol, my lovely children

ii

ACKNOWLEDGEMENTS

The author would like to express gratitude to Dr. M. W. Adams,
his major professor, for his assistance and guidance during this
study. Appreciation is also extended to Dr. J. Wiersma for his
helpful suggestions.

I thank the members of my guidance committee; Drs.‘M. W. Johnston,
A. W. Saettler, and Di.EL Linvill for their efforts.

I am indebted and grateful to the Rockefeller Foundation for
financial support which has enable me to complete this study.

Special thanks is expressed to my wife, Bertha, for her encourage-
ment and patient understanding during the completion of these graduate

studies.

iii

LIST OF

LIST OF

TABLE OF CONTENTS

Tums; . O O O O O O O O O I O O O O O I

FIGURES O O O O O O O O O O O O O O O O O 0

INTRODUCTION . . . . . . . . . . . . . . . . . . .

CHAPTER

CHAPTER

CHAPTER

1: LITERATURE REVIEW. . . . . . . . . .

'Canopy structure . . . . . . . . . . . . .

Light environment within plant canopies. .

Photosynthesis in relation to canopy struéturez.'. . . . .

Light limitation of photosynthesis . . . .

References . . . . . . . . . . . . . . . .

2: CANOPY ARCHITECTURE, LIGHT PENETRATION,

AND GROWTH

CHARACTERISTICS OF FOUR DRY BEAN (Phaseolus vulgaris L

 

PLANT TYPES. . . . . . . . . . . . . .
Abstract . . . . . . . . . . . . . ... .
Introduction . . . . . . . . . . . . . . .
Materials and Methods. . . . . . . . . . .
Results and Discussion . . . . . . . . . .
References . . . . . . . . . . . . . . . .
3: CANOPY ARCHITECTURE AND PHOTOSYNTHESIS

(Phaseolus vulgaris L.) PLANT TYPES. .
Abstract . . . . . . . . . . . . . . . .
Introduction . . . . . . . . . . . . . .

Materials and Methods. . . . . . . . . . .

Results and Discussion . . . . . . . . . .

iv

OF TWO DRY BEAN

Page

11
15

17

22
22
24
24
27

70

73
73
75
75

85

Page
References . . . . . . . . . . . . . . . . . . . . . . . . 121

CHAPTER 4: SUMMARY AND CONCLUSIONS. . . . . . . . . . . . . . . . 125

LIST OF TABLES
Page
CHAPTER 2

1. Extinction coefficient (k) at three plant spacing and
maximum LAI of four dry bean genotypes. . . . . . . . . . . . 38

2. Simple correlations of nine characteristics of four dry
hem genotypes C O O O O O O O O O O O O O O O O O O O O O O O 44

3. Analysis of Variance (ANOVA) of overall regression of
light interception by four dry bean genotypes . . . . . . . . 45

4. A model of light interception relationship with some
characteristics of four dry bean genotypes. . . . . . . . . . 45

5. Final yield and yield components of four dry bean geno-
types at three plant spacings: 5, 10 and 15 cm. . . . . . . . 47

6. Polynomial equations of total dry weight and LAI, of
four dry bean genotypes at 5 cm plant spacing, as
function of days after planting (t) . . . . . . . . . . . . . 48

7. Growth analysis characteristics of Seafarer at three “
plant spacings: 5, 10 and 15 cm . . . . . . . . . . . . . . . 50

8. Growth analysis characteristics of NEP-Z at three‘plant
spacings: 5, 10 and 15 cm . . . . . . . . . . . . . . . . . . 51

9. Growth analysis characteristics of line 31908 at three
plant spacings: 5, 10 and 15 cm . . . . . . . . . . . . . . . 52

10. Growth analysis characteristics of line 0686 at three
plant spacings: S, 10 and 15 cmg. . . . . . . . . . . . . . . 53

11. Harvestzindex values of four dry bean genotypes at three
plant spacings: 5, 10 and 15 cm . . . . . . . . . . . . . . . 58

12. Changes in dry weight/m2 of stems (WS) and pods (WP)
during the last two weeks of the growing period of four
dry bean genotypes at three plant spacings. . . . . . . . . . 64

13. Changes in dry weight/m2 of stems (WS) and pods (WP) by

plant strata during the last two weeks of the growing
season of Seafarer at 5 cm. . . - . . . . . . . . . . . . . . 65

vi

Page

14. Changes in dryweight/m2 of stems (WS) and pods (WP) by
plant strata durwng the last three weeks of the growing
season of NEP-Z at 5 cm. . . . . . . . . . . . . . . . 66
15. Changes in dry weight/m2 of stems (WS) and pods (WP) by
plant strata during the last two weeks of the growing
season of line 31908 at 5 cm . . . . . . . . . . . . . . . . 67
16. Changes in dry weight/m2 of stems (WS) and pods (WP) by
plant strata during the last two weeks of the growing
season of line 0686 at 5 cm. . . . . . . . . . . . . . . 68
CHAPTER 3
11. Average leaf angle by plant strata of Seafarer at 45 dap
grown under the sun environment. . . . . . . . . . . . . 89
2. Average leaf angle of canopy profile of Seafarer and NEP-Z
during the growing season. . . . . . . . . ... . . . . . . . 91
3. X2 (Ch-square) Test for random azimuth leaf orientation for
Seafarer and NEP-Z during the growing season . . . . . . . . 93
4. Leaf area distribution (2 of total) as a function of azimuth
? for Seafarer and NEP-2 after 49 and 59 dap, respectively . . 93
5. Analysis of Variance (ANOVA) for leaf size during the
growing season . . . . . . . . . . . . . . . . . . . . . 101
6. Leaf dry weight/plant dry weight ratio of Seafarer and _;”
NEP-Z during the growing season. . . . . . . . . . . . . . 102
7. Analysis of Variance (ANOVA) for specific leaf dry
weight (SLDW) during the growing season. . . . . . . . . . 103
8. Photosynthesis rates of canopy profiles of Seafarer
and NEP-Z during the growing season. . . . . . . . . . 105
9. Analysis of Variance (ANOVA) of photosynthetic rates
of Seafarer and REP-2 during the growing season. . . . . . 106
10. Simple correlation coefficients between C0 -uptake,
plant strata, leaf PAR, and specific lead dry weight
(SLDW) for Seafarer and REP-2. . . . . . . . . . . . . . . 111

vii

LIST OF FIGURES
Page
CHAPTER 2

1. Light attenuation (Z) and LAI profiles of Seafarer at
35 cm plant spacing during the growing season. . . . . . . . 28

2. Light attenuation (Z) and LAI profiles of NEP-Z at
5 cm plant spacing during the growing season. . . . . . . . 29

3. Light attenuation (Z) and LAI profiles of line 31908
at 5 on plant spacing during the growing season . . . . . . 3o

4. .Light attenuation (Z) and LAI profiles of line 0686 at
5 cm plant spacing during the growing season. . . . . . . . 31

5. Light attenuation (Z) and LAI profiles at maximum LAI
and 5 cm plant spacing of four dry bean genotypes: A)
Seafarer, B) HEP-2, 6) line 31908 and D) line 0686. . . . . 32

6. Attenuation of sunlight by the canopy of four dry bean:
genotypes at 5 cm plant spacing at the time of maximum
LAI O O C O O O O O O O C O O O O O O C C O O O O O O O O O 34

7. Attenuation of sunlight at 5 cm plant spacing during the
growing season. The line is at the time of maximum LAI . . 35

8. Attenuation of sunlight at 5 cm plant spacing during the
growing season. The line is at the time of maximum LAI . . 35

9. Leaf number distribution of three dry bean genotypes, at
S cm plant spacing at maximum LAI, as a function of leaf
inelination O O O O O O O O O O O O O O O O O O O O O O O O 40

10. Time course of relative light interception (Z of full

sunlight) by four dry bean genotypes at 5 cm plant

spacing . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11. Time -
11. Time course of LAI of four dry bean genOtypes at 5 at

plant spacing . . . . . . . . . . . . . . . . . . . . . . . 42

12'. 'ITimecrtoursetof RGR of four dry bean plan genotypes at
5 cm plant spacing. . . . . . . . . . . . . . . . . . . . . 55

13. Ontogenetic trends in NAR, LAR (A), LW/TW and LA/LW (B)
of Seafarer at 5 cm plant spacing . . . . . . . . . . . . . 55

viii

l4. Ontogenetic distribution of dry weight of Seafarer:
total (T), leaves (L), stems (8), flowers (F), and
pOdS (P) o o o o o o o o o o o o o o o o s o o o o o o o
15. Ontogenetic distribution of dry weight of NEP—Z: total
(T), leaves (L), stems (S), flowers (F) and pods (P). .
l6. Ontogenetic distribution of dry weight of line 31908:
total (T), leaves (L), stems (S), flowers (F) and
pads (P) O O O O I O O O O O O O O O I O O O O O O O O O C O
17. Ontogenetic distribution of dry weight of line 0686:
total (T), leaves (L), stems (S), flowers (F) and
pOdS (P) o o o o o o o~ o o o o o o o o o o‘ o o o o n e o o 0
CHAPTER 3
l. Plots under the shade environment . . . . . . . . . . . . .
2. Metal structure used to separate the crop canopy by
heights (10 cm eaCh) O O O O O O O O O C O O O O O O O O O
3. Apparatus used to expose leaves to 14C02 labeled 002. .
4. Closeup of the aluminum handpiece . . . . . . . . . .
5. The apparatus used for 14CO2 uptake measurements under
field conditions. . . . . . . . . . . . . . . . . . . . . .
6. Some of the complementary materials used in the 14002
uptake determinations in the field. . . . . . . . . . . . .
7. Leaf area distribution of Seafarer (A) and NEP-Z (B),
as a function of leaf indlination, during the growing
season and under the sun environment. . . . . . . . . . .
8. Leaf area distribution of Seafarer at 42 dap and under
"'c the sun environment: A) as a function of leaf inclination
during the day, and B) as a function of leaf inclination
and canopy height at 3:00 EDT . . . . . . . . . . . . . . .
9. Azimuthal density functions for Seafarer under the sun
eDVironment at 49 dap . o o o o o o o o o o o o o o o o o o
10. Leaf area distribution with plant height for Seafarer
under: A) the sun environment, and B) the shade environ-
ment. 0 O O O C O O O O O O O O O O O O O O O O O O O O O 0
11. Leaf area distribution with plant height for NEP-Z under:
A) the sun environment, and B) the shade environment. . .
12. LAI of Seafarer and NEP-Z during the growing season at

two light environments. . . . . . . . . . . . . . . .

ix

Page

59

60

61

62

77

77
80

80

82

82

87

88

94

96

97

99

13.

14.

.15.

16.

17.

18.

19.

20.

21.

Size of the central leaflet (A) and specific leaf dry
weight (B) of Seafarer and NEP—Z during the growing

season 0 O O O O O O O

Photosynthetic rates
function of leaf PAR

Photosynthetic rates
function of leaf PAR

Photosynthetic rates
function of leaf PAR

Photosynthetic rates
function of specific

dap . . . . . . . . . .

Photosynthetic rates
function of specific
dap O O O O O O O O 0

Starch determination on roots of A) HEP-2 and B) Seafarer

of Seafarer and NEP-Z canopies as a
at: A) 43 and B) 50 dap. . . . . . .

of Seafarer and NEP-Z canopies as a
at 58 dap O O O O O O O O O O O O O O

of Seafarer and NEP-Z canopies as a
at 65 dap O O O O C O O O O O O O O O

of Seafarer and NEP-Z canopies as a
leaf dry weight at: A) 43 and B) 50

of Seafarer and NEP-Z canopies as a
leaf dry weight at: A) 58 and B) 65

during the growing season in two light environments.. . .

Starch determination

on stems at the 3th internode of A)

REP—2 and B) Seafarer during the growing season in two

light environments. .

Ontogenetic changes in stem dry weight of Seafarer and
NEP-Z in two light environments . . . . . . . . . . . . .

Page

. 100

. 108-

109

110

114

115

118

119

120

 

 

 

 

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INTRODUCTION

Two principal physiological processes can be considered for
improvement of crop yields: photosynthate production and photosynthate
partitioning to the economically important organs. Photosynthate
production is affected by: 1) the properties of the leaves comprising the
stands, such as their stomatal number and behavior, response of the
mesophyll cells to irradiance, reflectance and transmittance properties,
effects of temperature on dark respiration and photorespiration, and
their physical resistances and carboxylation characteristics, 2) by the
architecture of the stands, including the total leaf area covering a
unit area of ground, leaf distribution along the stem, and the angle of
leaf inclination from the horizontal, and 3) by ambient climatic factors,

such as air temperature, wind speed, CO concentration, relative humidity,

2
soil moisture, and nutrient availability.
The potential for increasing crop productivity by optimizing canopy
structure has been documented by experimental research, modeling, and
computer simulation. PendletOn‘gggal, (1968) working with isogenic corn
hybrids differing in leaf angle and mechanically changed the leaf orienta-
tion obserVed increases in grain yield on corn.hybrids with more vertically
oriented leaves. Tenaka'gt_al: (1969) working with rice, demonstrated by
(mechanical manipulation that a horizontally-oriented leaf canopy showed

low~photosynthetic rates and a plateau-type response of photosynthesis to

LAI while an erect-leaved canopy showed a high photosynthetic rate and

 

 

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increased its photosynthesis with increasing LAI. The higher photo-
synthetic activity of an erect—leaved canopy produced a higher grain
yield.

Assimilate partitioning is a very dynamic process and varies with
the stage of plant development. In the vegetative stage of dry bean
(Phaseolus vulgaris L.) plants the distribution of assimilates is
dominated by proximity between the "source" and "sink", although a
phyllotactic pattern is superimposed. After flowering, when the
developing pods become major sinks, there is a more complex pattern,
although the relationship between leaves and pods in their own axils
still predominates. Both the use of 14002 as a tracer, and changes in
dry weight of specific organs have been important tools in helping to
understand assimilate distribution, but many important aspects of this
process, i.e., mechanism(s) of regulation, redistribution of storage
assimilates, etc., still remain to be studied in order to provide guide-
lines for the increase of yields by manipulation of photosynthate
partitioning.

The objectives of this investigation were to define comprehensively
those canopy architecture characteristics relevant to light penetration in
the canopy, to measure light penetration, canOpy photosynthesis and
ontogenetic carbohydrate partitioning. For these purposes four dry bean
genotypes differing in growth habit were selected and grown under conditions
of differential plant spacing and light environments in order to modify the

above mentioned characteristics.

CHAPTER 1

LITERATURE REVIEW

Canopy structure

Measurements of canopy structure. The canopy structure of a plant
stand can be characterized by the vertical and horizontal distribution
of leaf area and by its spatial inclination and orientation. Several
methods and kinds of equipment have been devised and used for determining
canopy structure.

The stratified foliage clipping method of Mouse and Saeiki (1953)
was devised to determine the vertical profiles of each plant element
within the canopy. For stratified sampling, a number of horizontal
layers are cut from a rectangular or circular sampling area and the
foliage area in each layer is determined separately.

Foliage inclination and orientation can be measured directly by
holding a compass and a protractor against the foliage (Nichiporovich,
1961; de Witt, 1965; Ross and Nilson, 1967). The leaves are then
classified in intervals of 10 or 15-6 degrees with respect to inclination
and 20 or 45° degrees with respect to azimuth. It is often desirable
to use a frame to delimit the sampling area and to harvest each piece
of foliage as it is measured.

Loomis 32421. (1968) measured leaf area index (LAI), the inclination
of leaves, and leaf arrangements in corn canopies by using the so-called
silhouette method. The plants are placed vertically against a chart with
horizontal lines drawn at 10 cm intervals. Then, each leaf is marked at

3

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the points where its midrib intersects the horizontal grid lines. The
length and width of each leaf segment is measured; its inclination and
stratum position are also noted.

The inclination point quadrat method was developed by Warren Wilson
(1959) for non-destructive sampling of foliage area index.and foliage
area index and foliage inclination. The method uses a quadrat which
has a probe with a sharpened steel knitting needle at its top. The
probe is passed slowly through the vegetation, and each time the point
touches foliage, this is recorded, together with the position, azimuth
and inclination of the probe. Ten probes are generally moved in each
direction (North, South, East, and West) and inclination; and the.mean
number of contacts fl.6 for a given probe inclination is calculated.
The mean inclination angle of leaves, 81’ and the leaf area density f1,

can be estimated by using the following relations:

tan 81 3 g' (0.1 £1.0/ £1.90) (1)
f1 - £1.90 X sec 81 (2)
where f and f are the mean number of contacts with leaves in the

1.0 1.90

horizontal and vertical direction, respectively.

‘Wide-angle lens photography has been suggested by Anderson (1964)
as a quick technique for recording crop structure. However, it has
more often been used for measuring light penetration through tall trees
than for plant architecture.

vertical profiles of leaf area density. M9031.££Hé£r (1973)
indicated that in spite of wide differences in plant species, it is

possible to recognizentwo main types of vertical profiles, namely grass

and forb types. The grass type characterized by a leaf area density
profile with its maximum in the middle height of the canopy. This
plant type has been observed in rice'(9_lzgg§1:_ix_a L.), corn (Leg EELS.
L.), and wheat (Triticum aestivum.L. em. Thell.) (Ito, 1969; Ross and
Nilson, 1967). The forb type has the maximum.leaf area density in the
upper 8th and 9th tenths of the canopy. This plant type was observed
in soybean (Glycine ma§.(L.) Herr.) and broad bean (Vicia faba L.)
(Ito and Udawa, 1971; Ross and Nilson, 1967). Other types of vertical
profiles of leaf area have also been observed; the sorghum (Sorghum
bicolor (L.) Mbench.) canopy has two peaks of leaf area density, one
at the upper (7th and 8th tenths) and onezat the lower (2nd and 3rd
tenths) level of the canopy (Ross, 1975); and the ryegrass (£21123,
multiflorum L.) canopy has most of its leaf area density in the lower
3rd level of the canOpy (Warren Wilson, 1959). The difference between
the leaf area density profile types is closely associated with the
difference in canopy structure, particularly in leaf angle distribution.
Ross and Nilson (1967) observed no changes in leaf density profile
function of a corn stand during the growing season, but there was a
shift of the maximum leaf density from the middle of the plant canopy,
at the initial stage of growth, to a lower canopy height, as the season
progressed.

'Leaf distribution with respect to azimuthgnglg. Although crop
plants seem to display leaf area equally with respect to azimuth angle,
plant arrangement and planting rates may change this.

Nichiporovich (1961) presented data showing no preferred azimuth
directions for wheat and corn. Similar results have been reported for
soybean.(Blad and Baker, 1972; Ito and Udagawa, 1971; Lemeour, 1973),

Jerusalem artichoke (Helianthus tuberosus L.) (Lemeour, 1973) , and broad

 

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bean (Ross and Nilson, 1967). However, Ross and Nilson (1967) and
Loomis and Williams (1969) reported a marked preference of corn
canopies for azimuthal directions perpendicular to the direction of
the planting rows. Probably this preferential orientation was related
to the.adaptation of the corn plant to the distribution of radiation
in the canopy. Lemeour (1973) also showed that sunflower (Helianthus
annuus L.) leaves have three preferential azimuthal directions due to
the spiral phyllotaxis of sunflower and to a superimposed effect of
heliotropism.

Leaf distribution with respect to inclination angle. de Wit
(1965) distinguished four types of canopies based on the corresponding
leaf inclination function. These functions are represented by plotting
the cumulative frequency of occurence of the inclinations against the
inclination, ranging from.0° for a horizontal leaf to 90° for a
vertical one. Planophile canopies are characterized by a predominance
of horizontal leaves, erectophile canopies by vertical leaves,
plagiophile canopies by obliquely inclined leaves, and extremophile
canopies by high frequencies by both horizontal and vertical leaves.

Nichiporovich (1961) suggested that the relative frequency of leaf
inclinations of corn leaves was the same as the relative frequency of
the inclinations of the surface elements of a sphere. This leaf angle
distribution.function is a special erectophile type in terms of de Wit's
classification scheme, since vertical leaves still occur with more
frequency.

Loomis and Williams (1969) cited several studies showing that the
canopy morphology of different cultivars of corn varies widely from

strongly erectophile to strongly planophile. Soybeans also have

ill

and

than:

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canopy structures that are dependent on cultivar: Chippewa 64 and Bark
cultivars are moderately planophile (Blad and Baker, 1972) while Amsoy
is erectophile (Lemeur, 1973).

Leaf inclination functions may show marked changes during plant
growth and with position in the plant. de Wit's data (1965) showed
that for perennial ryegrass, there was an increased proportion of
horizontal leaves as the season progressed. Loomis 32 31. (1968)
observed that the upper leaves of corn shifted to a more horizontal
position after tasseling. Warren Wilson (1959) reported that clover
(Trifolium.r§pens L.) leaves adopted a more vertical position from the
top to the bottom of the plant. Lemeur (1973) found that sunflower has
a uniform horizontal foliage, older leaves have a plagiophile structure
while the upper part of the plant is extremely planophile. Thus,
younger leaves are more horizontal.

Heliotropic response of leaf orientation. It is known that many
plants grow or move their leaves in response to the direction of
illumination.

Shiman (1967) noted that sycamore maple (Acer pseudoplatanus L.)
and lettuce (Letuca sativa L.) leaves had leaf inclination values which
changed during the day. The maximum number of sycamore leaves with
horizontal position occurred at noon, while for lettuce it was in the
morning and evening. Lang (1973) found that cotton (Gossypium
hirsutnmIRDTplants had leaves with orientation, azimuth angle and
inclination values which were different in the morning compared to those
in the afternoon. As such, 67% of the leaf area was illuminated in the

morning and 712 in the afternoon.

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Shell 35 a1. (1974) observed and measured the leaf inclination of
sunflower and beans (Phaseolus-vulgaris L.) in the morning, noon, and
afternoon. Sunflower leaves faced east to northeast in the morning,
tended to disperse during the day and then turned with the sun in the
afternoon to take up a new westerly azimuth. This response decreased
with age of plants; however, the younger third of the leaves of old
plants exhibited similar behaviour to the leaves of young plants. Leaf
inclination apparently did not change with time of day. Bean leaves
had a net northeasterly azimuth in the early morning and middle of the
day; this changed.to a northerly azimuth in the afternoon. Again with
increasing age, the tendency for a net preferred azimuth diminished.
For sunflower the average phase angle (angle between the sun’vector
and the vector which is the projection of the leaf, normal to the solar
plane) varied from a lead angle of 16° in the morning to a lag.of'15°
at midday and 38° in the afternoon. For beans the average phase angle
varied from.a lead angle of 38° in the morning to a lag of 13° at
midday and 44° in the afternoon; Wien and Wallace (1973) demonstrated
that the pulvinules are the light receptor organs controlling leaflet
movements in dry beans and that there are cultivar differences in this
response.

Grancher and Bohomme (1972), comparing measurements on young
leaves which orient in relation to the sun and using a single model in.
which the leaves were Considered fixed, showed that the heliotropism of
the leaves of cowpea (Zigng_unguiculata L.) favored the interception of
light in the early hours of the day, with a decrease in energy absorbed

during the hot part of the day.

pe1
mer

pl;

It:
so]
det

tio

trai

veg
rad:

diSp

Popu
radi
sect
Canoj
zero

ray :

 

Light environment within_plant canopies

The radiation environment within plant canopies is composed of four
kinds of radiant fluxes, i.e., direct and diffuse solar radiation fluxes
penetrating the canopy and the upward and downward fluxes of comple-
mentary diffuse radiation due mainly to transmission and reflection by
plant elements.

‘Light penetration: theoretical approach. The study of radiative
transfer in a plant canopy is complicated and no satisfactory general
solution has yet been found. The radiation regime in a plant canopy is
determined by the following factors: a) conditions of incident radia-
tion: direct and diffuse solar radiation and complementary radiation,

b) optical properties of leaves, stems, flowers, and fruits: reflection,
transmission, and absorption coefficients, and c) canopy structure.

One of the main problems in the study of radiation climatology of
vegetation is how the penetration function of direct and diffuse solar
radiation should be determined. Nilson (1971) classified leaf
dispersion of the plant canopies into:

1. Random leaf dispersion. The random dispersion is the most
popular distribution function and as such is most frequently used in
radiation models. With this dispersion it is assumed that each leaf
section can be found with the same probability at each position in the
canopy. This leaf arrangement has a Poisson distribution. Po, the
zero term of the distribution, represents the probability that a light

ray is not intercepted within a layer of the canopy. It is equal to:

'Po - igfz = exp <-kL) <3)
0

 

lea:
fon
pro!

905:

is

are

radi

nay

det
Ande

(1975

flux

(Bake

 

”alt:

than:

 

10

where I(f) = the intensity of solar radiation penetrating to a
depth f in.the canopy
Io - the intensity of direct radiation above the canopy
K - extinction coefficient
L - downward accumulation of leaf area index (LAI)

2. “Eggular leaf dispersion. With regular leaf dispersion the
leaves are assumed to be arranged in a systematic way which tends to
form a closed mosaic. Mutual shading of leaves is small. The
probability of light interception in the canopy is defined by a
positive binomial distribution.

3. Clumped leaf‘dispersion.‘ With clumped leaf arrangement there
is a strong tendency for mutual shading and frequent gaps of large size
. are possible. The probability of light interception in the plant
canopy is defined by the negative binomial distribution.

Calculation of the penetration and interception of diffuse
radiation with both clear and overcast conditions is difficult and this
may explain why few publications present detailed explanations of the
calculations (Cowan, 1968, Anderson and Denmead, 1969). For more
details the reader is encouraged to see the excellent reviews by
Anderson (1966, 1971), Lemeur and Blad (1974), Ross (1975), and Saeki
(1975).

nggrpenecration: measurements.- For the measurements of radiant
flux density at different heights in a crop, the Epply solarimeter
(BakerandMeyer, 1966) or tube solarimeter (Szeicz, 1965) have been
widely used. Photochemical methods of integrating light energy, i.e.,
ozalid paper, also haVe been used (Friend, 1961). The photosyn-

thetically active radiation (PAR), spectrum of 400 - 700 nm wavelength,

is

pix

 

vi:
the-
by

of

dep

blu

OhSe:

 

and 1.
rate ‘
until

and t5

 

 

11

is adequately measured by instruments with selenium or silicon
photovoltaic cells, or photo-emmission cells (Rubin, 1971).

Niilisk‘egggl. (1970) and Ross (1975) found that the spectral
distribution of penetrating direct and diffuse radiation does not change
with canopy depth and is the same as for incident radiation. However,
the spectral composition of complementary radiation (radiation scattered
by the leaves and the ground) depends strongly on the optical properties
of the foliage, and therefore its pattern is wavelength dependent.

The spectral distribution of the mean total radiation changes with
depth in the canopy. The fraction of PAR decreases, especially in the
blue and the redregions, whereas the fraction of near infrared radiation
(NIR) increases considerably. Federer and Tanner (1966) observed that
the spectral composition of total radiation differs in sunflecks and
shaded areas; in sunflecks the spectral distribution is similar to that
of incident total radiation, but in the shaded areas NIR predominates.

The review of thevalues of extinction coefficients (k) for various
crops and grasses by Monteith (1969) indicates that k ranges from 1.05
for crops with horizontal leaves (cotton and clover) to 0.24 for grasses
with vertical leaves (ryegrass), and exhibits diurnal variation depending
on the angle of incident radiation.

Photosynthesis in relation to canopy structure~

Measurements of canopy photosynthesis: Tanaka 33 31. (1966)
observed a relationship between the photosynthetic rates of a rice stand
and light intensity at different growth stages. The photosynthetic
rate and saturation point of the plant population increased with age
until panicle initiation, at which time there was no saturation point,

and then declined. At high light intensity the upper leaves received

 

1m

c
1'8T

 

whi
The

V6!

(Ho:
cam
due

the

tech
loca;
leave
Pendl
leaf
corn
with

leaVe

 

lower

field~'

leaVes

 

12

light in excess of their saturation point, while the lower shaded
leaves were below the saturation point and would still respond to
increased light.

Tanaka (1972) demonstrated by mechanically manipulating leaf
inclination that a horizontal-leaved rice canopy shows a plateau type
response of photosynthetic rate to radiation, whith low photosynthesis,
while an erect-leaved rice canopy shows a higher photosynthetic rate.
The rice yield of the horizontal-leaved rice canopy was 702 that of the
vertical-leaved rice canopy.

Pearce RENEE: (1967) reported that seedlings of Weng barley

(Hordeum.vulgare L.) with more vertically oriented leaves had higher

 

canopy photosynthetic rates than seedlings with more horizontal leaves,
due to better light penetration. Angus and Wilson (1972) investigated
the vertical profile of net photosynthesis in two wheat cultivars, one
an erect leaf type and the other a lax leaf type, using a 14C02-
technique. The patterns of net photosynthesis indicated that the
localization of carbon dioxide uptake was near the top of the horizontal-
leaved canopy and at the middle of the vertical-leaved canopy.
Pendleton'gggél. (1968), working with isogenic corn hybrids differing in
leaf angle and mechanically changing the leaf orientation of another
corn hybrid, observed increases in grain yield of the corn hybrids
‘with.more vertically oriented leaves. They suggested that upright
leaves permit better light penetration into the plant canopy and allow
lower leaves to receive higher light intensity.

Beuerlein and Pendleton (1971) found that leaves at the top of
:field-grown soybean plants have higher net photosynthesis (NP) than

leaves at the bottom of the plants due not to leaf age, but to acclima-

13

tion to a low light regime after having been shaded by young leaves.
Older leaves of debranched plants kept in full sunlight retained high
NP. Johnston‘s; El. (1969) found apparent photosynthetic rates of
naturally shaded bottom.and middle leaves to be 13 and 60% less than
those of top leaves. Rates of the same bottom and middle leaves
exposed to full sunlight increased by 258 and 502 respectively, but the
rates were only 26 to 902 those of top leaves in full sunlight.

Turner and Incoll (1971), working with sorghum and tobacco
(Nicotiana tabacum-L.), reported that photosynthesis declined with
depth in the canopy during day light hours and was correlated with the
attenuation of light by the crop and by stomatal resistance. Peet ggugl.
(1977) measured the photosynthetic rates of nine bean cultivars at
first flowering, early pod develOpment, and late pod development. They
found that photosynthetic rates in all cultivars differed at different
developmental stages with the highest rates occurring at early pod
development.

Theoretical approaches to canopy phatogynthesis. Canopy photo-
synthesis has been theoretically studied by two methods. The first
method is based upon the light interception theory and the second is
based on carbon dioxide transfer theory.

Canopy photOsynthesis models based on light interception theppy.
One Of the first models for canopy photosynthesis was that of Mbnsi
and Saeki (1953). This model was constructed on the basis of the light
attenuation law within plant canopies and on the basis of light photo-
synthesis curves of leaves. They expressed net photosynthesis

Gq_' p - r) per unit of leaf area by the following equation:

14
q a 'I‘bI i - r (4)
14+ aI

where £_indicates respiration per unit leaf area, and §_and p are
coefficients related to the photosynthetic capacity of a single leaf.
By substituting light intensity in equation (4) by equation (3) and
integrating from 0 to F for LAI, the equation for total net photo-
synthesis of a plant canopy (P) becomes:

P-_l_>_ln' l+aho -rF(5)

aK 1 + aho. exp (-kF)

As the use of high speed digital electronic computers has stimulated
the development of procedures for calculating and simulating canopy
photosynthesis in relation to canopy structure, and as more mathematical
theories have been developed for describing light penetration within
plant canopies (warren Wilson, 1968; Ross, 1971) numerous models for
crop photosynthesis have been proposed. Advanced models have included
leaf transmissibility (Saeki, 1960), type of radiation flux in the
canopy (de Wit, 1965; Duncan SE 31., 1967), sunlit leaves on which
direct and diffuse radiation flux acts.(Ross, 1975), and age of the
leaf (Holt 3: $1., 1975).

Models and computer simulation of canopy photosynthesis have
permitted broad generalizations as follows:

- Leaf inclination is an important factor in total crop photo-
synthesis. Maximum photosynthesis is found when leaf inclination
changes gradually from 90° at the top layer to 0° at the lowest layer
of the canopy. It has been stated that the "ideal foliage" consists
of layers with continuously changing inclination so that available

light is evenly spread over all available leaf area.

15

- Light saturation points for photosynthesis in a plant population
becomes higher with increasing leaf area. The light-photosynthesis
curve is markedly affected by the extinction coefficient as well as by
leaf area.

- Net photosynthesis of a plant population with vertical foliage
is greater than that with horizontal foliage, at a high LAI. However,
at low LAI the plant population with horizontal oriented leaves shows
greater photosynthesis per unit land area.

Canopy~photosynthesis models based-on carbon dioxide transfer
theogz. An alternative approach for studying canopy photosynthesis is
the carbon dioxide transfer model based on the following differential
equation which describes carbon dioxide exchange between the plant
canopy and the surrounding atmosphere.

-' 11. (Keri) - -fl<z)p(z) + £1(z)r<z) (5)
dz dz'

where:
K a turbulent transfer coefficient
C - CO2 concentration in the air among leaves
fl(z) - the height-leaf area distribution function
p(z) - height function of photosynthesis
r(z) ‘ height function of respiration
The CO2 transfer model is suitable; and it has been used for
assessing the influence of micrometereological factors, wind velocity,
soil CO flux, and artificial CO

2 2
CPartridge, 1970; Allen ggwgl., 1971; Lemon, 1973; Allen 25 El. 1974).

enrichment on canopy photosynthesis

Light limitation of phatosynthesis
It is well documented that the photosynthetic characteristics

(if many species of plants, i.e., light-dependent CO uptake curves,

2

 

 

 

 

Bra.

 

lOng

 

with
ligh:
leis".

Spec:

___-—_=

 

16

are influenced by the spectral composition and intensity of radiation
under which the plant is grown.

Light intensity during growing affects leaf morphology, chloroplast
structure, and a number of component processes of photosynthesis.

High intensity radiation: induces additional development of the palisade
and spongy mesophyll regions, resulting in thicker leaves (Pearce and
Lee, 1969; Ludlow and Wilson, 1971; Bjorkman EEnélr: 1972; Mobel'egngl.,
1975); increases stomatal frequency (Holmgren, 1968; Crookston ggngl.,
1971; Bjorkmaniggngl., 1972); changes mesophyll resistance(rm), rm is
higher in plants grown at low light (Holmgren, 1968; Ludlow and Wilson,
1971; Crookston SE $1., 1975); and changes the content of solube
protein per unit leaf area and amount and activity of RdDP carboxylase
(Blenkinsop and Dake, 1974; Crookston ggngl., 1975). Several factors
are modified when plants are grown at different light intensities, and
there is no consensus concerning any factor as the prime cause of the
altered photosynthetic capacity.

Dale (1965), working with bean plants, found that leaf number was
greater with high light intensity treatments and also that this effect
was due to development of leaves on lateral branches. There was also
an effect of radiation on leaf expansion and on the unfolding rate of
leaves on the main stem. Maximum rate of leaf growth was similar for
different light intensities, but the maximum rate was maintained for a
longer period under high light regimes. .Rajan.ggugl. (1971), working
with bean and corn plants, observed that the spectral composition of
light, red/infra red ratio (ri), greatly affected plant growth. Plant
height and leaf area increased as ri increased from 2.4 to 7.6, while

specific leaf dry weight decreased.

REFERENCES

Anderson, M. C. 1966. Stand structure and light penetration, II.
A.theoretical analysis. J. Appl. Ecol. 3: 41-54.

Anderson, M. C. and O. T. Denmead. 1969. Short wave radiation on
inclined surfaces in model plant communities. Agron. J. 61:
867-872.

Anderson, M. C. 1971. Radiation and crop structure. lg_Sestak, 2.,
J. Catsky, and P. G. Jarvs (ed.) Plant Photosynthesis Production.
Manual of Methods. pp. 412-466. Dr. W. Junk N.V. Publishers,
The Hague.

Angus, R. and J. H. Wilson. 1972. A comparison of barley cultivars
with different leaf inclination. Aust. J. Agr. Res. 23: 945-947.

Allen, L. H., Jr., S. E. Jensen and E. R. Lemon. 1971. Plant response
to carbon dioxide enrichment under field conditions: Assimilation.
Science 173: 256-258.

Allen, L. H., Jr., D. W. Steart and E. R. Lemon. 1974. Photosyn-
thesis in plant canopies: Effect of light response curves and
radiation source geometry. Photosynthetica. 8: 184-207.

Baker, D. N. and R. E. Meyer. 1966. Influence of stand geometry on

light interception and net photosynthesis in cotton. Crop Sci.
6: 15-19.

Beuerlein, J. E. and J. W. Pendleton. 1971. Photosynthetic rates and
light saturation curves of individuals soybean leaves under field
conditions. Crop Sci. 11: 217-219.

Bjorkman, 0., N. K. Boardman, J. M. Anderson, S. W. Thorne, ..
D. J. Goodchild and N. A. Pyliotis. 1972. Effect of light
intensity during growth of Atriplex patula on the capacity of
photosynthetic reactions, chloroplast components and structure.
Carnegie Inst. Washington Yearb. 71: 115-135.

Blad, B. and D.G. Baker. 1972. Orientation and distribution of leaves
within soybean canopies. Agron. J. 61: 26-29.

Bleuikinshop. P.G. and J.E. Dale. 1974. The effect of shade treat-
ment and light intensity on ribulose-l,5-diphosphate carboxylase
activity and fraction I protein level in the first leaf of barley.
J. Exp. Bot. 25: 899-912.

17

18

Cowan, I. R. 1968. The interception and absorption of radiation in
plant stands. J. Appl. Ecol. 5: 367-379.

Crookston, R. K., R. J. Treharne, P. Ludford and J. L. Ozbun. 1975.
Response of beans to shading. Crop Sci. 15: 412-416.

Dale, J. E. 1965. Leaf growth in Phaseolus vulgaris L. I. Tempera-
ture effects and the light factor. Ann. Bot. 29: 293-308.

Duncan, w. G., R. S'..Loomis, w. A. Williams and R. Hanan. 1967. A
model for simulating photosynthesis in plant communtieis.
Hilgardia 38: 181-205.

Friend, D. G. C. 1961. A.simple method for measuring integrated light
values in the field. Ecology 42: 577-580.

Grancher, C. V. and R. Bonhomme.~ l972.~ Utilisation de 1'energie
solaire par une culture de‘Vigga'Sinensis L. I. Etude theorique
de l'influence de l'heliotropisme des feuilles sur l'intercion
des rayonnements. Ann. Agron..23: 407-417.

Holgren, P. 1968. Leaf factors affecting light-saturated photo-
synthesis in ecotypes of Solidago virgaurea from exposed and
shaded habitats. Physiol. Plant. 21: 676-698.

Holt, D. A., R. J. Bula, G. E. Miles, M. M. Schreiber and R. M; Peart._
1975. Environmental physiology, modeling and simulation of
alfalfa.growth: I. Conceptual development of SIMED. Agr. Exp.
St., Purdue University. Research Bull. 907. pp. 1-26.

Ito, A. 1969. Geometrical structure of rice canopy and penetration
of direct solar radiation. Proc. Crop Sci. Sco. Jap. 38: 355-363.

Ito, A. and T- Udagawa. 1971. Phytometrical studies of crop canopies.
I. Geometrical structure of soybean canopy and sunlight penetration.
J. Agr. Meteorol. 26: 187-195.

Johnston, T. J., J. W. Pendleton, D. B. Peters and D. R. Hicks. 1969.
Influence of supplemental light on apparent photosynthesis, yield,
and yield components of soybeans (Glycine max. L.). Crop Sci.

9: 577-480.

IKubin, S. 1971. Measurement of radiant energy. .15 Sestak, Z., J.
Catsky, and P. G. Jarvis (ed.) Plant Photosynthetic Production.
Manual of Methods. pp. 703-765. Dr. W. Junk N. V. Publishers..
The Hague.

iLang, A. R. G. 1973. Leaf orientation of a cotton plant. Agric.
Meteorol. 11: 37-51.

Lemeur, R. 1973. A method for simulating the direct solar radiation
regime in sunflower, jerusalem.artichoke, corn, and soybean
canopies using actual stand structure data. Agr. Meteorol.
12: 229-247.

 

.‘lc

Ni

Ni

 

 

19

Lemon, E. 1973. Predicting crop climate and net dioxide exchange.
Photosynthetica 7: 408-413.

Loomis, R. S., W. A. Williams, W. G. Duncan, A. Dovrat, and F. Nunez.
1968. Quantitative deseriptions of foliage display and light

absorption in field communities of corn plants. Crop Sci. 8:
352-356.

Loomis, R. W} and W. A. Williams. 1969. Producitivity and the
morphology of crop stands: Pattern with leaves. .Ig_Eastin,
J. D., F. A. Haskins, C. Y. Sullivan and C. H. M. Van Bavel. (ed.)
Physiological Aspects of Crop Yield. pp. 27-47. Am. Soc. Agron.
Madison, Wisconsin.

Ludlow, M. M. and G. L. Willson. 1971. Photosynthesis and illuminance
history. Aust. J. Biol. Sci. 24: 1065-1075.

Monsi, M. and T. Saeiki. 1953. Uber den lichtfaktor in den
pflanzengesellschften und seine bedeutung fur die stoffproduktion.
Jap. J. 301:. 14: 22-520

Mbnsi, M., Z. Uchijima and T. Oikawa. 1973. Structure of foliage
canopies and photosynthesis. Ann. Rev. Ecol. Syst. 4: 301-327.

Monteith, J. L. -l969. Light interception and radiative exchange in
crop stands. .13 Eastin, J. D., F. A. Haskins, C. Y. Sullivan
and C. H. M. Van Bavel (ed.) Physiological Aspects of Crop Yield.
pp. 89-111. Am. Soc. Agron. Madison, Wisconsin.

Nichiporovich. A. A. 1961. Properties of plant crops as an optical
system. Sov. P1. Physiol. 8: 428-435.

Niilisk, H., T. Nilson and J. Ross. 1970. Radiation in plant canopies
and its measurements, IE Prediction and Measurement of Photo-
synthetic Productivity. pp. 165-177. Proc. of the IBP/PP
Technical Meeting, Trebon, 14-21 Sept. 1969.

Nilson, T. 1971. A theoretical analysis of the frequency of gaps in
plant stands. Agric. Meterol. 8: 25-38.

Nobel, P. S., L. J. Zaragoza and W. K. Smith. 1975. Relation between
mesohyll surface area, photosynthetic rate and illumination level
during developmentof leaves of Plectranthus parviflorus Henckel.
Plant Physiol. 55: 1067-1070.

Nerman, J. M., E. E. Miller and C. B. Tanner. 1971. Light intensity
and sunfleck-size distribution in plant canopies. Agron. J.
63: 743-748.

Paltridge, G. W. 1970. A model of a growing pasture. Agr. Meteorol.
7: 93-130.

Pearce, R. B., R. H. Brown and R. E. Blaser. 1967. Photosynthesis in
plant communities as influenced by leaf angle. Crop Sci. 7: 321-
324.

 

in

See

Sae

She

d;

Tana '

 

20

Pearce, R. B. and D. R. Lee. 1969. Photosynthetic and morphological
adaptation of alfalfa leaves to light intensity at different
stages of maturity. Crop Sci. 9: 791-794.

Peet, M. M., A. Bravo, D. E. Wallace and J. C. Ozbun. 1977. Photo-
synthesis, stomatal resistance and enzyme activities in relation
to yield and field-grown dry bean varieties. Crop Sci. 17: 287-
293.

Pendleton, J. W., G. E. Smith, S. R. Winter and T. J. Johnston. 1968.
Field investigation of the relationships of leaf angle in corn
(Egg_Mazs L.) to grain yield and apparent photosynthesis.

Agron. J. 60: 422-424.

Rajan, A. K., B. Betteridge and G. E. Blackman. 1971. Interaction
between the nature of the light source, ambient air temperature,
and the vegetative growth of different species within growth
cabinets. Ann. Bot. 35: 323-343.

Ross, Y. K. and T. Nilson. .1967a. The vertical distribution of
biomass in crop stands. ‘13 Nichiporovich, A. A. (ed.) Photo-
synthesis of Productive Systems. pp. 75-85. Translated edition.
Israel Prog. Sci. Trans., Jerusalem.

Ross, Y. K. and T. Nilson. 1967b. The spatial orientation of leaves
in crop stands and its determination.‘ 12_Nichiporovich, A. A.
(ed.) Photosynthesis of Productive Systems. pp. 86-95.
Translated edition. Israel Prog. Sci. Trans., Jerusalem.

Ross, J. 1975. Radiative transfer in plant communities. ‘Ig_Monteith,

J. L. (ed.) Vegetation and the Atmosphere, Vol. II. pp. 1-55.
Academic Press, New York.

Saeki, T. 1960. Interrelationships between leaf amount, light
distribution and total photosynthesis. Bot. Mag. 73: 55-63.

Saeki, T. 1975. Distribution of radiant energy and C02 in terrestral
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Productivity in Different Environments. pp. 297-322. Cambridge
University Press. New York.

Shell, G. S., A. R. G. Lang and P. J. M. Sale. 1974. Quantitative
measurement of leaf orientation and heliotropic response in
sunflower, bean, pepper and cucumber. Agric. Meteorol 13: 25-37.

Shiman, L. M. 1967. Determination of the orientation of plant leaves
in space. Sov. Plant Physiol. 14: 326-328.

Szeicz, G. 1965. A.miniature tube solarimeter. J. Appl. Ecol.

Tanaka, A., K. Kawano and J. vamaguchi. 1966. Photosynthesis,
respiration and plant type of the tropical rice plant. Int.
Rice Research Inst. Tech. Bull. 7.

21

Tanaka, T. 1972. Studies on the light-curves of carbon assimilation
of rice plants. The interrelation among the light-curves, the
plant type and the maximizing yield of rice. Bull. Nat. Inst.
Agr. Sci. A. 19: 1-100.

Turner, N. C. and L. D. Incoll. 1971. The vertical distribution of
photosynthesis in crops of tobacco and sorghum. J. Appl. Ecol.
8: 581-591.

Warren'Wilson,,J. 1959. Analysis of the spatial distribution of
foliage by two-dimensional point quadrats. New Phytol. 58: 92-101.

Wien, H. C. and D. H. wallace. 1973. Light-induced leaflet orienta-
tion in Phaseolus vulgaris L. Crop Sci. 13: 721-724.

Wit, C. T. de. 1965. Photosynthesis of leaf canopies. Agric. Res.
Rep. No. 663. Center Agri. Publ. Doc. wageningen. 57 p.

m w.~- -v 1

 

 

 

 

 

Plai

 

CHAPTER 2

CANOPY ARCHITECTURE, LIGHT PENETRATION AND GROWTH
CHARACTERISTICS OF FOUR DRY BEAN (Phaseolus vulgaris L.)

PLANT TYPES

ABSTRACT

Four dry bean genotypes were selected on the basis of their
different growth habits. The genetypes and growth habits were:
a) MSU experimental line 31908, a narrow bush type (CIAT type I),
b) cultivar Seafarer, a normal bush type (CIAT type I), c) cultivar
NEP-Z, a narrow erect, short vine type (CIAT type II), and d) MSU
experiemental line 0686, a determinate but very vigorous vegetative
type (resembling CIAT type III). Light measurements within the canopies
were estimated using the Ozalid paper technique of Friend (1961).
Formulae used in making the Calculations of growth parameters are those
listed by Redford (1967). Different plant densities (47, 20, and 9
plants/m?) were used to modify the canopy architecture.

In general, similar results were obtained for light penetration
in the plant canopy and for final seed yield for the three plant
spacings, independent of plant type. Vertical leaf distribution varied
during the growing season. The maximum Leaf Area Index (LAI) was
approximately at the middle of the plant height, which later shifted to
higher plant layers for NEP-Z, lines 31808 and 0686, but not for

Seafarer. Light distribution in the plant canopy fit Bouger-Lambert's

22

23.

law, with relative illumination as an exponential function of LAI.
Light penetration in the canopy was found to be greater in Seafarer
and lower in line 31908: while NEP-2 and line 0686 showed intermediate
values. Relative Growth Rate (RGR) was higher for Seafarer and lower
in line 31908. NEP-Z and line 0686 had intermediate RGR values.
Differences in RGR were due to differences in Net Assimilation Rate
(NAR) rather than in Leaf Area Ratio (LAR). RGR for any plant type
was affected by plant spacing. Plant spacing did not affect the
patterns 0f the ontogenetic partitioning of dry weight among, leaves,

stems, petioles, flowers and pods for any plant type.

 

 

 

 

 

th

he

INTRODUCTION

The weight of dry matter produced by a crop is essentially the
integral of the erop's rate of photosynthesis throughout the growing
season, and economic yield might be expected to depend to some extent
on crop photosynthesis and partitioning of material to the economic
plant organs. Crop architecture parameters related to light penetration
in the plant canopy and leading to increased crop production, e.g.,
leaf inclination, have been identified; and optimizing the structure of
the canopy in order to effect an improvement in crop productivity has
been proposed. Most of the experimental evidence concerning the effects
of leaf inclination on the processes leading to yield comes from.work
with.gramdnaceous crops; very few attempts have been made with
economically important dicotyledoneous crops.

The present work aims to determine crop architecture parameters
relevant to light penetration and light penetration measurements, as
wellias ontogenetic patterns of dry weight partitioning among the plant
organs of four dry bean plant types. Different plant densities were
used to modify crop architecture.

MATERIALS AND METHODS

This.experiment was conducted at the Saginaw Valley Bean-Beet
Research.farm, on a fine texture soil classified as Charity Clay Loam.

Four dry bean genotypes were selected on the basis of their
differential growth habits. These genetypes and growth habits were:

a) MSU experimental line 31908, a narrow bush.type (CIAT type I),

24

25

b) cultivar Seafarer, a normal bush type (CIAT type I), c) cultivar
NEP-Z, a narrow erect, short vine type (CIAT type II), and d) MSU
experimental line 0686, a determinate but very vigorous vegetative type
(resembling CIAT type III). Effective planting densities of 47, 20,
and 9 plants/m2 were established by use of three spacings, 5, 10, and
15 cm within the row and a constant space of 70 cm between rows. The
experimental units were arranged.in a randomized block design with
three replications. Each plot consisted of six rows 5.8 m long.
Planting date was the second week of June, 1976. During planting, a
band application of 500 kg/ha of 18 - 46 - 0 plus 4% Mn and 22 Zn
fertilizer was applied. All plots received 2 cm of sprinkler irriga-
tion during the last week of July to compensate for the deficiency

in natural rainfall during that period.

The four central rows of each plot were used for periodic
collection of data. Five uniformly spaced plants were harvested at
weekly intervals for 10 consecutive weeks starting 30 days after
planting (dap). The samples for the final harvest (normal maturity
for each genotype) were taken from 2 m of row. On each date, the
plants to be harvested were cut and harvested in 10 cm segments,
beginning from the ground. The plant material within each section was
separated into stems and petioles, flowers, pods and leaves. "This
material was then dried in a forced-air dryer at 45 to 50° C to a
constant dry weight. For specific leaf dry weight (SLDW) determination,
a sample of five central leaflets was randomly chosen from the
harvested leaves of each plant height segment of each plot and their
area was measured with a portable leaf area meter (Lambda Instruments

Model LI-300). The leaflets were then dried as were the other plant

26

parts. Leaf area was determined by multiplying SLDW by the total
leaf dry weight of each plant height segment of each plot in each
harvest.

Light measurements were estimated using the ozalid paper technique
of Friend (1961). Twelve sheets of ozalid paper (402 ZT sepia paper,
Gaf Corporation, New York, NY 10020) were stapled together and then
cut into packets of 2 by 2 cm. These were placed with the light
sensitive side up in black-painted petri dishes of 4.0 cm diameter and
1.7 cm height. The booklets were pressed close to the cover by a foam
pad in the container. Light reached the booklet through a .5 cm
(diameter) unpainted "window" on the cover. The containers were
sealed with plastic vinyl tape to protect the booklets from rainfall.
The containers with the ozalid papers were placed at 10 cm intervals
from the ground up into the canopy and between two plants in the same
row. They were held by a fixed metal rod in the ground in each plot.
The same location was used in sampling for amount of light penetration
during the growing season. The containers were placed in position
between 9:00 - 10:00 a.m. on each sampling date and collected after
24 hours. To develop the exposed booklets, they were placed in a
wire basket and suspended in a coffee can which contained concentrated
ammonium hydroxide. The booklets were left in the air-tight container
for l to 3 hours. A count of the number of bleached papers gave an
estimate of the amount of light for that particular plant position and
date. To convert the number of papers bleached to light energy values,
a calibration curve was made by exposing the ozalid papers for varying
lengths of time to a light source and/or direct sunlight and directly
measuring light intensity with a light meter (Lambda Instruments Model

LI-l70 with a quantum sensor).

 

 

 

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RESULTS AND DISCUSSION

In general, similar results were obtained for light penetration
and final seed yield for the three plant spacings,independent of plant
type. Most of the data presented will be for the 5 cm plant spacing,
but remarks relating to other plant spacings will be given when
appropriate.

Plant canopy and light interception

Light attenuation, percent of full sunlight and Leaf Area Index
(LAI) profiles, during the growing season, of four dry bean plant types
are presented in Figures 1 to 5. Some features are readily apparent.
The values of LAI increased with time during the season. Maximum LAI
for the four genotypes were attained at different times.

The vertical distribution of the area of green leaves varied
during the course of the growing season. The maximum LAI increased
(from 0.3 to.l.3) and its position shifted to higher profile layers
at maximum total LAI. At the 30 to 70 days after planting (dap) stage
of plant development the distribution curves were nearly symmetrical
with respect to the maximum, which occurs approximately at the height
of h/2, where h_is the canopy height. As the plant grew the maximum
shifted to higher layers (above h/2). Observations of the variation
in the leaf area of individual layers revealed an increase, a maximum
and then a decrease in every layer, as time progressed.

NEP-Z, lines 31808 and 0686 showed the same leaf vertical profile
trends as soybeans and broad beans (Ross and Nilson, 1967; Ito and
Udawa, 1971). Seafarer had its maximum LAI at approximately the same
plant height, 10 to 30 cm from the bottom, during the period of 30 to

72 dap. These vertical profiles are good for characterizing and

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33

describing plant type and light penetration through the plant canopy;
however, they do not provide information about the leaf disposition
and dispersion with plant width or row width, i.e., if the leaves are
close to the stem or more dispersed across the row.

Light attenuation profiles showed that light interception is
closely related to LAI profiles. The greatest amount of intercepted
light occurred at the layer(s) of maximum LAI. Light distribution in
the plant canopy changed with plant height in an exponential manner
and fit Bouguer-Lambert's law (equation 3), with relative illumination
as an exponential function of LAI. Since the first introduction of
Bouguer-Lambert's law into plant studies by Mbnsi and Saeki in 1953,
many attempts have been made to describe light environment in crop
communities. Results with broad beans (Ross and Nilson, 1967), corn
(Loomis 35 al., 1968), and soybeans (Hicks 22 al., 1968; Lee, 1976),
indicate that light distribution can be adequately characterized by
an exponential function of LAI. Probably it is not the best function
to be used, because its assumptions are not always met by the plants;
however, its simplicity makes it the most popular equation in use.

Attenuation of sunlight by the plant canopy as a function of LAI
is presented in Figures 6 to 8. Some features are apparent. Figure 6
shows that with similar LAI, these plant types intercepted different
amounts of light, i.e., at LAI of 3, Seafarer intercepted 422 of
sunlight, while line 31908 with the same LAI‘intercepted 66%. These
differences are assumed to be due to differences in morphological
characteristics between the plant types, such as leaf size, leaf
shape, leaf angle, number of branches, etc. Figures 7 and 8 show that in
each plant type, light interception, during the growing season, was

greatly associated with LAI. The light interception data are grouped

 

Auk /.ur

A dZflHdCJfl ddfiw BC N v

H

 

 

I ( Z of full sunlight )

100

80

60

40

20

34

 
  
 
 
  
  

--—- Seafarer
..... Odo NEP‘Z
-*-**"Line 31908

--~ '- -' Line 0686

 

 

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«- °\ ‘
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*\* .\.\ ‘ ‘
\" ‘\.
\* \O‘.
\~ 0 ~
\ .
P‘ *\
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\k
\,.\
Ks
E J W
1 2 3 4

LAI from top of canopy

Figure 6. Attenuation of sunlight by the canopy of four
dry bean genotypes at the time of maximum LAI
and at 5 cm plant spacing.

I ( Z of full sunlight )

100

80

6O

40

20

100

80

60

40

20

\

010

P’-

 

 

35

Seafarer

\\\ff (3 44 dap

\ Os 51 "
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\ * 65 n

 

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CM 58 "
O *6: n
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1 2 3 4

LAI from the top of canopy

Figure 7. Attenuation of sunlight at 5 on plant

spacing during the growing season. The
line is at the time of maximum LAI.

I ( I of ful sunlight )

 

36

Line 31908

 

Line 0686

 

 

I.
b

l L

1 2 3 4
LAI from the top of canopy

Figure 8. Attenuation of sunlight at 5 on plant

spacing during the growing season. The
line is at the time of maximum LAI.

37

around the line for maximum.LAI which indicates that in each plant type,
LAI was a major factor in light interception. Leaf size changed during
ontogenesis of the four plant types. Dry bean plants orient their
leaves with the position of the sun in the sky. This response is
affected by leaf age, and genotype (Wien and Wallace, 1973). Apparently,
the method used for light measurements was not precise enough to detect
these physiological and morphological changes.

Extinction coefficient (k) in equation 3, is a dimensionless para-
meter describing the light absorption properties of a particular type of
foliage. It depends on many factors such as chlorophyll concentration in
the leaf, leaf shape, leaf size, leaf angle, heliotropism, etc. Values
of k were estimated at maximum LAI and are presented in Table l. The
results show a particular pattern for each plant type; R values were very
similar with slightly higher values for wider plant spacing. As was
expected, Seafarer had the lowest k values, since it was the cultivar
with the lowest light interception.

A common standard procedure is to measure light distribution and
leaf angle at noontime in order to avoid heliotropic effects. Even
when dry bean leaf angles change during the day, representative
determination of leaf angle at midday can be used for estimating
differences during the ontogenesis of the plants or between genotypes.
During the time of maximum LAI for each plant type, angle of divergence
from the horizontal was measured between 10:00 and 12:00 a.m. EDT on
a sunny day, by placing a protractor on the adazial surface of the
central leaflet. The number of leaflets was recorded and grouped in
one of 9 angle classes of lO-degree intervals (0-10,...,80-90). The
results are presented in Figure 9. The average leaf angle were: 73.04,

63.80, and 50.20 for Seafarer, NEP-Z, and line 31908, respectively.

38

Table l. Extinction coefficient (k) at three plant spacing and
maximum LAI of four dry beans genotypes.

 

 

 

Genotype Plant spacing jcm)

5 10 15
Line 31908 .4629 .4789 .4773
Seafarer .2615 .2746 .2775
Nep-Z .3396 .3426 .3424

Line 0686 .2993 .3051 .3079

 

 

 

 

 

39

Leaf angles were not determined for Line 0686, because the measurement of
its many leaves presented a physical time limitation. However, it had
leaves of similar shape and size as Seafarer, and it is expected that
the leaf angle should be similar to Seafarer. Figure 9 shows that these
plant types did differ in the frequency of leaf angle inclination as well
as in the average leaf angles. These plant canopies, according to their
leaf angle distribution, could be classified as different degree of
erectophile foliar structure by using de Wit's system (1965). However,
de Wit's system.uses leaf area accumulation, while I used leaf number
accumulation, which might lead to different results. Soybean plants
have erectophile structure and differences between genotypes have been
observed (Blad and Baker, 1972; Lemeur, 1973).

Relative light interception for the whole plant canopy was
calculated by substracting light penetrating to the bottom of the
canopy from total incident light. The time courses of relative light
interception and LAI are presented in Figures 10 and 11. These
results show that relative light interception was closely associated
with LAI and both have similar trends during ontogenesis of the four
plant types. Seafarer with a LAI of 3.7 had 562 of light interception
44 dap. A LAI of 7.5 to 8.0 is needed by this cultivar for interception
of 952 of the sunlight. At 51 dap, LAI's of the four plant types were
similar, but intercepted different amounts of sunlight on the same day.
This may be caused by other morphological characteristics such as leaf
angle.

Several of the proposed plant "Ideotypes" (Donald, 1967; Mock and
IPearce, 1975; Adams, 1973) consider the following as valuable char-
acteristics of a crop community: its ability to have a better light

(tistribution in the canopy, maximum.light interception, rapid accumula-

Cumulative frequency distribution

40

 

1.0 f
‘ Seafarer
6.
---------~ NEE—2 f!
1;!
'8‘ P Fn-n-u- Line 31908 1r}!

 

 

Leaf inclination (angle)

Figure 9. Leaf number distribution of three
dry bean genotypes, at S cm plant
spacing and maximum LAI, as a
function of leaf inclination.

41

 

 

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43

tion of maximum leaf area, and leaf area duration as long as possible,
among others. All of the previously mentioned characteristics are
related with better light interception and utilization through photo-
synthesis. The results in Figures 9 and 10 indicate that it would be
desirable to have, under some condition such as long growing season,
early planting, or higher plant density, a commercial dry bean cultivar
with the leaf area duration of NEP-Z and the leaf orientation and seed
characteristics of Seafarer.

To establish a relationship between light interception, Z of
ground cover by the plant canopy (plant canopy width/row width), leaf
size (average of central leaflet area at maximum LAI, in cmz), leaf
angle, extinction coefficient (k), number of branches, canopy height
(cm), and canopy width (cm), simple correlation coefficients were
calculated and are presented in Table 2. Extinction coefficient was
positively and significantly correlated to leaf size and negatively
correlated to leaf angle. As the leaf angle is increased, more light
should penetrate the plant canopy (lower k value). Apparently, big
leaves require more energy and/or present more physical resistance to
be moved and tend to orient themselves less than small leaves. This
could explain the negative relationship between leaf size and leaf
angle. However, leaf size and leaf angle depend upon the position in
the plant canopy, which confound the primary cause for the negative
relationship .

To determine the simultaneous relative importance of the above
characteristics to light interception, the statistical procedures
used were Step-Wise Multiple Regression and Backward Elimination. The
results were equal with both procedures, which indicates the prevalent

relative importance of the characteristics which were significant;

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45

Table 3. Analysis of Variance (ANOVA) of overall regression of light
interception by four dry bean genotypes.

 

 

Source of Variance df SS MS F
Regression 4 2812.9977 703.2494 255.69**
Error 7 19.2522 2.7503

 

Table 4. A.model of light interceiption relationship with some
characteristics of four dry bean genotypes.

 

 

Regression Partial R2
Characteristic coef. cor. coef. delete
Constant 367.0385 .8577 .9742
Ground cover (Z) .3646 .8486 .9757
LAI 9.3445 .9650 .9010
Extinction coef. (k) -298.3075 -.7805 .9826
Leaf angle -3.8837 -.8680 .9724

Total R2 - .9922

 

46
results are presented in Tables 3 and 4. LAI, leaf angle, 2 of ground
cover, and the extinction coefficient were the most important character-
istics, accounting for 99.22% Of the variance in light penetration.
Growth Characteristics
Yield and yield components

Analysis of Variance (ANOVA) did not show statistically significant
differences either among plant densities or for the plant density X
plant type interaction. A summary of the results is presented in
Table 5. The observed yields (Kg/ha) are in the normal range obtained
with these plant types at Saginaw, Michigan. However, the seed dry
weights (gr/100 seeds) were lower than those usually observed in these
plant types, i.e., Seafarer normally has a seed dry weight of 18 to 19
gr/lOO seeds, at a seed moisture content of 152, while I obtained 15.55.
This could be due to the oven drying of the seeds for the determination
of this characteristic.

Growth analysis.

Techniques used to quantify the components of crop growth are
collectively known as "growth analysis". Watson (1952) has reviewed the
traditional techniques of growth analysis. Radford (1967) presented a.
review of the growth analysis formulae, their derivation, and necessary
conditions for their use. More recently, there are reports with
excellent reviews of growth analysis techniques (Richards, 1969; Kuet
535.21., 1971; 0ndok and Kvet, 1971; Hunt and Parsons, 1974).

In the present work, the data were used to select functions which
idescribed the total dry weight and leaf area vs. time relationships.
Presented in Table 6 are polynomials of best fit, determined using a
least squares procedure, which described the time course of total dry

weight and LAI for each plant type. They were then used to calculate,

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47

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49

for selected days during the growing season, instanteous values of
Relative Growth Rate (RGR), Net Assimilation Rate (NAR), Leaf Area
Ratio (LGR), Leaf Dry weight/Total Dry Weight Ratio (LN/TW) and Leaf
Area/Leaf Dry Weight Ratio (LA/LW). Formulae used in making the
calculations are those listed by Radford (1967) and 0ndok and Kvet
(1971).

Tables 7 to 10 present the results of the use of growth analysis
techniques. To visualize the data on RGR, they are also graphically
presented in Figure 12. For purposes of the following discussion,
note the relationships, RGR - NAR X LAR, and LAR - (LW/TW) X_(LA/LW).

Very similar trends in RGR, NAR, and LAR were observed between
plant type and plant spacing. In general, RGR for any plant type was
affected by plant spacing with the lower values for the closest plant
spacing. Simdlar results have been reported for broad beans (Ishag,
1972). The argument used to explain these results has been that NAR
is related to or measures the photosynthetic capacity of the plants.
At a low plant density, enough light passes through the plant canopy,
such that the lower leaves have higher photosynthetic rates and
'maintain these rates for a longer time (delayed senescence). In the
present work, the percent ground cover by Seafarer at maximum LAI
*was 64, 57, and 602 for 5, 10, and 15 cm plant spacings, respectively.
These data and light penetration measurements indicated that light was
:not.limiting at the bottom of the plant canopies. Differences in
‘the time required for the lower leaves to become yellow, and percent
«of yellowing were not observed between plant spacings. These results
suggested that- light penetration in the plant canopy was not the only
cause for differences in NAR between plants at different plant

spacings .

50

 

 

 

 

 

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.o canoe

52

 

 

 

mmoo. oqoc. amoo. maaa.m moom.m mcmo.~ 1 mmao. 1 cane. Hooo. 1 cm
mooo. eeoo. coco. m~e4.~ numn.m ome~.o Home. moNo. aooo. ma
deco. amoo. emoo. eeeo.m mono.m maoH.H some. eeuo. maoo. an
acne. cone. «coo. nnoo.m mmmn.m mano.n Name. Name. Nana. me
«one. «Nae. Hana. a4~n.~ no~m.m mono.~ some. «nee. Heao. an
acne. mmno. emno. meom.~ mne~.m heuo.~ «mac. some. same. on
mass. keno. «sac. noon.m seam.e mnem.m ammo. «who. mneo. as
keno. mane. Hana. ease.e ammo.m omea.e anon. amao. coho. an
amoo. omnc. mono. Hose.o omnm.m moea.m memo. same. same. on
111111111 H1w Na 11111111 111111 HImoo ~13 m 1111111 11111 HIhno le w 11111
so no on n so no on n ao.m4 on n ago
men mez mom some

 

.ao ma one .oH .m "mmnaonnm unoan women no oooam snag mo mofiumunmuooumno

3932.“ nusouo

.m manna

53

 

 

 

weoo. amoo. oeoo. o~m~.n mneo.n anne.n «coo. mmoo. coco. an
deco. Hoes. meoo. amnn.m emmn.m emee.~ cane. acne. cone. Na
whoa. “moo. amoo. o~on.a m~ow.~ ono~.m o~mo. mnuo. cowo. no
none. none. none. mo~a.e Hmm~.m mnuo.m Nose. same. Name. mm
mmno. «moo. Hmso. oaaa.e emem.m mmom.m memo. some. «moo. on
mane. memo. mmno. ~onm.e nmne.m umae.m omoo. amao. Home. as
emNo. memo. mane. e~me.m oon.e memm.m memo. anon. case. am
«one. cone. mane. mmoo.e moan.e o~ee.e knee. coca. ammo. on

11111111 H1w Na 111111111 1111111 H1moo «13 w 111111 11111 H18o H1» m 11111

as no on n so no on n ,ao no on m, awe

men «<2 use some

 

.ao ma one .oH .m umwnaonnm anode woman on oooo snag mo mowomquouoouono mamhaonn nuzonu

.3 mafia.

54
RGR was affected by plant spacing in each genotype. This was the

result of differences in NAR rather than in LAR. LAR was apparently
not affected by plant spacing. RGR trends among plant types were
similar with peak values at 37 dap for Seafarer, Lines 31908 and 0686,
and at 44 dap for NEP-Z. These values were observed at early flowering
for each cultivar, thereafter, RGR values decreased. Figure 12 shows
that Seafarer had the highest RGR values before and at 37 dap, with a
second peak at 51 dap during pod filling. Figure 13 presents results
for Seafarer at the 5 cm plant spacing; similar. trends have been
observed for the other plant spacings and with the Other Plant types.
The initial peak (Figure 12) is primarily the result of a similar peak
in LAR (Figure 13b). Thereafter, the similarity between the RGR and
NAR curves indicated that RGR was being affected by NAR. Trends in LAR
and LW/TW indicated that LW/TW was the primary factor affecting LAR.
The increase in NAR at 51 dap is interpreted as a response of the leaves
to an increased demand for assimilates during pod filling. Similar
increases in NAR during pod filling have been reported previously for
broad beans (Ishag, 1972), soybeans (Koller 3.5 31;; 1970), and peas

(Pisum sativum L.) (Easting and Gritton, 1969). The net photosynthetic

 

rate has been observed to increase in soybeans (Dornhoff and Shibles,
1970) and dry beans (Feet 91; _a_1_., 1977), during pod filling.
Partitiongg of dgy matter: Harvest Index

Harvest Index (HT) is probably the most popularly and commonly
used index of dry matter partitioning. This index has been proposed as
a selection criterion to increase the economic yield of crops
(Nichiporovich. 1975; Donald and Hambling, 1975; Wallace _e£ 31., 1975).

HT is calculated as the ratio of economic (seeds) yield to the

total‘yield of plant material (biological yield). True biological

55

.mnfiomom anode so n no manhoonmw noon zoo snow mo mom mo omnooo mafia

wnHHnM4n nouns who:
we . as .m 44 1. . an

 

.‘l I'.

coco on“;
mooum snag t1x1n1;
~1an ..1.1.1.
umuououm .IIIIII.

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on

..0‘ 0"! 0|.

on

.3.

c 8.01 x I_&ep 1-3 3 1 H93

NAR ( gr m'z day"l )

LW/TH ( gr gr'l )

 

56

 

 

 

 

 

p-
p.
D-
'.
NAR
LAR .----0 1
D-
+ . L L - L3)
30: 37 44 51 58 65 72
P
e“"’"“----e '(3
I. \
/ \
e I “
// \.-.--Q
, e ‘s‘
0 ‘q
\ 4 z
,1 \\\\\\
LWIN O_O \ d 1
" 1.11m: .----. "“
30 37 '44 51. SI 85 72
Days after planting
Figure 13. Ontogenetic trends in NAR, LAR, LW/TW,

and LA/LW of Seafarer at 5 cm plant
spacing.

 

u/Lu ( 1112 xr'1 1: 10-2 )

57
yield includes the weight of roots, but since they are normally
nonrecoverable, the term is usually applied to the total above ground
weight. Sometimes the pulled roots are included.

HI values were calculated for the four plant types and are
presented in Table 11. The results indicated that plant spacing
affected HI, independent of plant types, The lowest HI value
corresponds to the closest plant spacing (5 cm); however, no statisti-
cally significant differences were observed for 10 and 15 cm plant
spacing. HI is a result of complex physiological processes and no
single factor can be identified as the most important one in
determining HI. In cereal crops, HI has been reported to be affected
by plant population, water availability, nitrogen nutrition, genotype,
and genotype X environment interaction (Donald and Hamblin, 1975).

I_)_rz weight of plant components

The dry weight distribution of the four plant types at 5 cm plant
spacing are presented in Figures 14 to 17. All plant parts, including
leaves, stems, and pods, developed progressively later toward the top
of the plant. However, the difference in growth stage among plant
parts was much less in the case of pod walls and seed parts (hereafter
termed pod) than for leaves and stems. Consequently, the time
interval between vegetative and pod development was shorter toward the
top of the plant. .Due to the greater overlap of vegetative and pod
growth toward the top of the plant, the distinction between vegetative
and pod development stages becomes less apparent.

Dry weight of lower leaves started to decrease before flowering.
Leaf dry weight was significantly related to leaf number, r - .98806,
.98083, .98576, and .97549 for Seafarer, HEP-2 and Lines 31908 and

0686, respectively, which indicates that the decrease in leaf dry

58

Table 11. Harvest index values of four dry bean genotypes at three
plant spacings.

 

Plant spacing (cm)

 

 

Genotype ‘ 5 10 15

HI 2 * HI Z HI . Z Mean
Seafarer .4976 87.48 .5321 93.55 .5688 100.00 .5328a**
NET-2 .4722 80.86 .5651 96.74 .5840 100.00 .5404a
31808 .4884 84.06 .5563 95.75 .5810 100.00 .5419a'
0686 .3239 63.30 .4449 85.57 ..5199 100.00 .4296 b
khan:
Dunn: .4455a. .5239b .5634 b

 

* Harvest Index values (HI) as percent of 15 cm plant spacing.

** Letters not in common indicate significant differences by the Duncan's
Multiple Range Test (52 level).

59

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unuoneue menus when

 

 

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63

weight was due to leaf drop. In the literature, the decrease in the
leaf area of this stratum has been related to decreased N2 - fixation.

Pod dry weight of the bottom.and tap of the plants, together
constitute 16.32%, 11.30%, 0.51%, and 16.40% of the total pod dry
weight of Seafarer, HEP-2, and Lines 31908 and 0686, respectively.
Furthermore, these two strata also had the lowest leaf area of the
whole plant canopy.

The trends of dry weight distribution among leaves, stems, and
pod suggest movement of material from leaves to stems and pods. In
the present report, changes in stem dry weight and pod dry weight will
be used as an estimate of the possible contribution of storage material
to the final seed and pod dry weight. This technique has been
previously used by Gallagher _e_t_ _a_2_[_. (1975, 1976) with small cereal.
grains. Changes in leaf dry weight were not considered because their
changes were greatly affected by the loss of leaves. The dropped leaves
‘were not collected. The stem and petioles were included in the stem
dry weight. Dropped petioles were collected and also included in the
stem dry weight.

Changes in stem dry weight and pod dry weight were calculated for
the last three weeks for Seafarer and HEP-2, and for the last two weeks
for the other cultivars. The results are presented in Table 12. This
table shows that there are differences between plant types in the
'possible contribution of previously stored materials in the stem and
jpetioles to the final pod dry weight. Differences were also observed
between plant spacings in all plant types. For example, in Seafarer,
previously stored materials in stems and petioles, if translocated to

pods, may constitute 27.612 of the final pod dry weight.

64

Table 12. Changes in dry weights/m2 of stems (AWS) and pods (AWP) during
the last two weeks of the growing period of four bean geno-
types at three plant spacings.

 

 

Plant spac. stems pods
Genotype (cm) (AWS) (AW?) AWS/AWP
Seafarer 5 - 25.25 +1 91.09 .2761
10 - 10.08 1+ 82.40 .1223
15 - 8.98 + 110.31 .0814
NET-2 5 - 89.33 + 171.27 .5216
10 - 54.80 + 238.73 .2295
15 - 41.02 + 272.94 .1503
31908 5 - 43.82 + 96.34 .4548
10 - 20.27 + 127.40 .1591
15 - 16.14 + 141.76 .1139
0686 5 - 17.62 + 111.92 .1478
10 - 17.30 _ + 146.65 .1180

15 - 14.85 + 148.65 .0999

 

65

Table 13. Changes in dry weight/m2 of stems (AWS) and pods (AWP) by
plant strata during the last two weeks.of.the growing period
of Seafarer at 5 cm.

 

 

 

 

 

 

Dates Plant strata (cm from the bottom)
0 - 10 10 - 20 20 - 30 30 - 40 g
dap AWS
58 - 65 + 4.38- - 1.15 — 7.15 - 6.23 - 10.15
65 - 72 - 18.46 - 1.15 - 1.62 + 6.23 - 15.00
2 - 14.08 - 2.30 . - 8.77 0.00 - 25.15
AW?
58 - 65 + 18.91 + 72.65 - 2.31 - 17.76 + 71.49
65 -172 - 4.85 - ‘5u30 1+ 14.53 + 15.22 + 19.60

2 1+ 14.06 .+67.35 + 12.22 -— 2.54» + 91.09

 

 

 

 

 

 

 

Table 14. Changes in dry weight/m2 of stems ..(AWS) and pods (AWP) by
plant strata during the last three weeks of the growing
period of HEP-2 at 5 cm.

Date Plant strata (cm from the bottom)

0-10 10-20 20-30 30-40 40-50 2

-dap AWS

72 - 79 - 7.61 - 16.60 - 14.30 - 10.38 - 8.99 - 57.88

79 - 86 - 4.85 - 2.70 - 3.63 + 2.84 - 1.38 - 9.72

86 - 93 - 4.84 - 9.84 - 5.60 - 2.37 - .92 - 21.73

E - 17.30 - 29.14 - 23.53 - 9.91 - 9.45 - 89.33

AWS

72 - 79 + 8.30 + 34.60 + 25.14 + 9.46 + 2.54 + 80.04

79 - 86 - 1.16 + 34.30 + 38.41 + 11.82 - 1.69 + 81.68

86 - 93 + 10.00 + 10.58 - 20.50 + 7.78 + 1.69 + 9.55

E + 17.14 + 79.48 + 43.05 + 29.06 - 2.54 +l7l.27

 

67

 

 

 

 

 

 

Table 15. Changes in dry weight/m2 of stems (AWS) and pods (AWP) by
plant strata during the last two weeks of the growing
period of Line 31908 at 5 cm.

Date Plant strata (cm from the bottom)

0 - 10 10 - 20* 20'6 30 30 - 40 40 - 50 2
dap AWS

72 - 79 - 5.45 + 4.62 - 12.22 - 8.76 - 7.38 - 29.19

79 - 86 - 2.63 - .85 - 1.01 - 8.07 - 2.07 - 14.63

2 - 8.08 ' - 3.77 - 13.33 - 16.83 - 9.45 - 43.82

AWS
72 - 79 0.00 + 21.43 + 31.59 + 23.14 - 3.54 + 72.62
8 0.00 + 40.45 + 40.47 + 34.14 - 8.76 + 96.30

 

68

Table 16. Changes in dry weight/m2 of stems (AWS) and pods (4W?) by

plant strata during the last two weeks of the growing
period of Line 0686 at 5 cm.

 

 

 

 

 

 

Date Plant strata (cm from.the bottom)
0'- 10 10 - 20 20 - 30 30 - 40 X ;_
dap AWS -
65 — 72 - 5.47 - 5.84 - 2.31 + 5.54 - 8.08
72 - 79 + 7278 - 2.84 - 3.69 - 10.84 - 9.54
X + 2.31 - 8.68 - 5.90 - 5.30 - 17.62

AWS

65 - 72 + 9.46 + 63.10 - 12.68 + 7.61 1+ 67.49
72 - 79 - 7.61 + 51.30 + .51 - .23 + 44.43
E + 1.85 +114.40 - 12.17 + 7.38 +lll.92

 

69

Changes in stem dry weight and pod dry weight were also calculated
by plant strata and the results are presented in Tables 13 to 16. These
tables show that there are differences in the change of stem dry weight
and changes in pod dry weight among strata. Apparently the dry weight
changes in the stem are equivalent to the changes in dry weight of
pods at the bottom and top strata of all plant types with the exception
of Line 31908 at the lowest strata where no pods were present. This
may result in an important mechanism especially in the lowest strata
where leaf fall starts before flowering. Changes in stem and root
dry weight late in the growing season have been reported to be related
to changes in reducing sugars and total nonstructural carbohydrates
(Subhadrabandhu, 1976; Martinez, 1976; Bouslama, 1977). Salazar 55:11.
(1977) reported the presence of differential amounts of starch in
stems and roots of 24 {dry bean cultivars at physiological maturity.

The decrease in dry weight of petioles, stems, and roots, late in
the growing season, could be due to the use of stored materials in the
respiration of these organs, translocation of stored materials to
pod and seed, and/or leaching out of stored materials from the roots
into the soil due to root leakage. The stored materials could also
'be used in late regrowth of the plant from the base of the stem. This

subject warrants further study.

REFERENCES

Adams, M. W. 1973. Plan architecture and physiological efficiency
in the field bean. Potential of field beans and other food
legumes in Latin America. Series Seminars @E. Centro Inter-
nacional de Agriculture Tropical. Cali, Colombia. pp. 266-295.

Blad, B. L. and D. G. Baker. 1972. Orientation and distribution of
leaves within soybean canopies. Agron. J. 61: 26-29.

Bouslama, M. 1977. Accumulation and partitioning of carbohydrates
in two cultivars of navy beans (Phaseolus vulgaris L.) as
influenced by grafting and source-sink manipulation. M.S.
Thesis. Michigan State University. E. Lansing, Michigan.

Donald, C. M. 1968. The breeding of crop ideotypes. Eupbytica
17: 385-403.

Donald, C. M. and J. Hamblin. 1975. The biological yield and
harvest index of cereals as agronomic and plant breeding criteria.

Adv. in Agron. 27: 361-405.

Dornhoff, G. M. and R. M. Shibles. 1970. Varietal differences in net
photosynthesis of soybean leaves. Crop Sci. 10: 42—45.

Fried, D. G. C. 1961. A simple method of measuring integrated light
values in the field. Ecology 42: 577-580.

Gallagher, J. N., P. V. Biacoe.and R. K. Scott. 1975. Barley and its
environmentJ V. Stability of grain weight. J. Appl. Ecol.
12: 319-336.

Hicks, D. R., J. W. Pendleton, R. L. Bernard and T. J. Johnston.
1969. Response of soybean plant types to planting patterns.
Crop Sci. 297-307. .

ZKuet, J., J. Svoboda, J. P. 0ndok, and P. G. Jarvis. 1971. 'Methods
of growth analysis. ‘Eg Sestak, Z., J. Castsky and P. G. Jarvis
(ed.) Plant Photosynthetic Production. Manual of Mehtods.
pp. 343-391. Dr. W. Junk N. V. Publishers, The Hague.

Ishag, H. M. 1973. Physiology of seed yield in field beans (Vicia
faba L.) II. Dry matter production. J. Agr. Sci. Camb. 80:

191-199.

Koller, H. R., W. E. Nyquist and I. S. Chorush. 1970. Growth
analysis of the soybean community. Crop Sci. 10: 407-412.

70

71

Lemeur, R. 1973. A method for simulating the direct solar radiation
regime in sunflower, jerusalem artichoke, corn.and soybean canopies
using actual stand structure data. Agr. Meteorol. 12: 229-247.

Martinez, R. R. 1976. Nitorgen fixation and carbohydrate partitioning
in Phaseolus vulgaris L. Ph.D. Thesis. Michigan State
University. E. Lansing, Michigan.

Mock, J. J. and R. B. Pearce. 1975. An ideotype of maize. Euphytica
24: 613-623.

Monsi M. and T. Saeki. 1953. Uber den lichtfaktor in den pflanzengese-
1lschaften und seine bedutung fur die stoffproduktion. Jap. J.
Bot. 14: 22-52.

Nichiporovich, A. A. 1975. The genetics of photosynthesis and
rational means of breeding highly productive plants. .12 Nasyrov,
Yu. S., and Z. Sestak (ed.) Genetic Aspects of Photosynthesis.
pp. 315-341. Dr. W. Junk B. V. Publishers, The Hague.

0ndok, J. P. and J. Kvet. 1971. Integral and differential formulae
in growth analysis. Photosynthetica 5: 358-363.

Peet, M.‘M., A. Bravo, D. H. Wallace and J. L. Ozbun. 1977. Photo-
synthesis, stomatal resistance and enzyme activities in relation
to yield of field-grown dry bean varieties. Crop Sci. 17: 287-
293.

Radford, P. J. 1967. Growth analysis formulae. Their use and abouse.
Crop Sci. 7: 171—175.

Richards, F. J. 1969. The quantitative-analysis of growth. .13
Steward, F. C. (ed.) Plant physiology - A Treatise. Vol. 5A.
pp. 3-76. Academic Press, NY.

Ross, J. K. and T. A. Nilson. 1967. The spatial orientation of
leaves in crop stands and its determination. ‘Ig_A. A. Nichiporovich
(ed.) Photosynthesis of Productive Systems. pp. 86-99. Tranlated
by Israel Prog. Sci. Transl. Jerusalem.

Salazar, J., J. Wiersma and M. W. Adams. 1977. IKIfistarch status in
bean varieties at three stages of seed-development. Ann. Rpt.
Bean Imp;.Coop. pp. 24-27.

Subhadrabandhu, S. 1976. Control of abscission of flowers and fruits
of Phaseolus vulgaris L. Ph.D. Thesis. Michigan State university.
E. Lansing, Michigan.

 

Fflallace, D. H., M. M. Feet and J. L. Ozbun. 1975. Studies of 002
metabolism in Phaseolus vulgaris L. and applications in breeding.
[IE_Burris, R. H. and C. C. Black (ed.) C02 Metabolism.and Plant
Productivity. pp. 43-58. University Park Press, Baltimore.

Watson, D. J. 1952. The physiological basis of variation in yield.
Adv. in Agron. 4: 101-144.

72

Williams, W. A., R. S. Loomis, W. G. Duncan, A. Dovrat and F. Nunez.
1968. Canopy architecture at various densities and the growth
and yield of corn. Crop Sci. 8: 303-308.

Wit C. T. de. 1965. Photosynthesis of leaf canopies. Agric. Res.
Rep. No. 663. Center Agri. Publ. Doc. Wageningen. 57 p.

CHAPTER 3

CANOPY ARCHITECTURE AND PHOTOSYNTHESIS OF TWO

DRXVBEAN.(Phaseolus vulgaris L.) PLANT TYPES

ABSTRACT

Two dry bean genotypes were selected on the basis of their
different growth habits. They were: a) Seafarer, a normal bush type
(CIAT type I), and b) NEP-Z, a narrow erect, short vine type (CIAT
type II). The azimuth and the inclination of all bean leaflets at
every 10 cm.plant height (plant strata) up to the top of the canopy were
measured weekly by the use of a compass and an inclinometer. Carbon
dioxide uptake of bean leaves, by plant strata, were measured using a
l4COZ-technique modified from the one proposed by McWilliam a; 11;.
(1973). Two light environments (full and 502 full sunlight) were used
to modify crop architecture and photosynthesis.

Seafarer and NEP-Z, due to their leaf inclination functions, could
be classified as erectophile and planophile foliar structure,
respectively, by using de'Wit's system (1965). Leaf area distribution
as a function of leaf inclination and average leaf angle showed that
the leaf angle changed with plant strata and time of the day. The shade
environment reduced the average leaf angle of Seafarer and NEP-Z by
22.54% and 23.22%, respectively. Neither Seafarer nor NEP-Z, under
‘both light environments, had leaves oriented with more frequency for any
.azimuth. Leaf area indexes of both cultivars were increased by the shade

73

74

environment, primarily by affecting leaf size. Photosynthetic rates
increased from the bottom to the top leaves, for both cultivars.
Maximumco2 uptake rates for each plant stratum were observed at

inital pod filling. Seafarer had higher rates of uptake at all canopy
levels than NEP-Z. During the stage of maximumco2 uptake, the shade
environment reduced the uptake rates of Seafarer and NEP—Z by 55.19%

and 30.54%, respectively. Starch, measured by IKI, started to accumulate
in roots and stems of both cultivars after flowering. At final harvest
starch disappeared in both roots and stems of Seafarer but was still
present in NEP-2. The shade environment reduced the amount of starch

but not the ontogenetic patterns.

INTRODUCTION

The primary productivity of plant communities is initially
dependent upon photosynthesis. The pattern of leaf display at each
levellof a community can be related to light interception, canopy
photosynthesis, and hence, to production. Results obtained by
experimental research and modeling with grasses indicate that leaf
inclination is an important characteristic of plant architecture for
light penetration in the plant canopy. The results with dry bean
(Chapter 2) also identified leaf inclination as an important morpho-
logical characteristic.

The objectives of this study were to measure photosynthesis in
different plant strata and to better characterize the canopy archi-
tecture of two dry bean plant types during their ontogenetic develop-
ment. Light environments (full and 502 sunlight) were used to modify '
canopy architecture and photosynthesis.

MATERIALS AND METHODS

This experiment was conducted at the.Michigan State University
Crop Science Farm, E. Lansing, on a soil clasified as a Miami-Concver
Loam.

Two dry bean genotypes were selected on the basis of their
different growth habits. They were: a) Seafarer, a normal bush type
(CIAT type I), and b) NEP-Z, a narrow erect, short vine type (CIAT type
II). Both cultivars were seeded in 70 cm.rows oriented north-south,

with 5 cm.between plants within rows. Two light environments were

75

 

 

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- o

76
imposed on each cultivars: 1) full sunlight during the whole growing

season (hereafter termed sun environment), and 2) shade environment 30
days after planting (hereafter termed shade environment). For the shade
environment, incoming Photosynthetically Active Radiation (PAR) was
reduced 50% by using a plastic screen raised 150 cm from the ground.
The light treatments were not randomly allocated to the plots due to
physical limitations in the construction of the support system for the
plastic screen. However, the cultivars were randomly allocated in
the experimental plots. The plots were distributed in a randomized
complete block design with three replications. Each plot consisted
of six rows, each 5.8 m long. Planting date was on June 8, 1977.
One week before planting 500 Kg/ha of 18-16-0 plus 42 Mn and 22 Zn
fertilizer were broadcast and incorporated on the experimental area.
All plots received supplemental sprinkler irrigation when necessary.
The four central rows of each plot were used for periodic collec-
tion of data. All the plants in a .5 m sample or row were harvested
at weekly intervals for 7 consecutive weeks starting 30 days after
planting (dap). The sample for the final harvest was taken from 2.0 m
of row; At each harvest date the plants were separated into stem and
petioles, flowers, pods, and leaves, and 'then dried in a forced air
dryer at 45 to 500 C to a constant dry weight. For specific leaf dry
weight (SLDW) determinations, a sample of five central leaflets was
randomly choosen from the harvested leaves in each plot and their area
was measured with a portable leaf area meter (Lambda Instruments Mbdel
LI-300). The leaves were dried like the other plant parts to obtain
their dry weights. The Leaf Area Index (LAI) of each plot was
determined by multiplying its respective SLDW by its corresponding

leaf dry weight.

 

 

77

Figure 1. Plots under shade environment. The plastic screen
was raise 150 cm about the ground leve.

Figure 2. Metal structure used to separate the crop canopy
by heights (10 cm each).

78

 

 

 

Figure 1.

 

 

Eigure 2.

79

The azimuth and the inclination of all been leaflets at each 10 cm
plant height up to the canopy in a .5 m row were measured weekly between
11:00 a.m. and 1:00 p.m. EDT. The azimuth of each leaflet was determined
with a compass and then was classified into one of eight different 45°
intervals. The inclination of each leaflet was measured with an
inclinometer constructed by drilling a small hole in the center of a
broad protractor base, inserting a thread through the hole, and
fastening two smalllead weight on both ends of the thread. The base of
the protractor was placed parallel to the adaxial surface of the leaflet
to determine the angle of leaf inclination with a horizontal line. The
leaflets were grouped into inclination classes with 100 intervals.

Carbon dioxide uptake of bean leaves were measured using a 14002
technique modified from the one proposed by McWilliam gt 21. (1973).
This method has been suggested for measurement of apparent photo-
synthetic rates by various researchers (Austin and Longden, 1967;
Shimsi, 1969; Incoll and Wright, 1969; Bravdo, 1972; McWilliam 25 $1.,
1973; Neylor and Teare, 1975). The usual technique consists of three
operations: 1) exposing leaves to a known 14C02 activity for a given
time interval, 2) obtaining a leaf sample form the exposed area, and
3) measuring the amount of l4COthich has been taken up.

The apparatus used in this experiment (Figures 3 and 4) to expose
a leaf segment to 14C02 can be divided into:

A) l4C02 gas supply: The radioactive gas was obtained in 54 Its
compressed-gas bottle from Matheson Gas Products, East Rutherford, NJ;

340 ppm 14C02 (with a specific activity of lO‘HCi/l), 212 of 0 and

2’

the balance N2.

B) Photosynthesis chamber: The one used was similar to the one"

described by MbWilliams'ggual. (1973), and consisted of an aluminum

80

Figure 3. Apparatus used to expose leaves to 1400 labelled
C02. A) 14C02 gas syookuer: 54 Its bottle, B) gas
regulator, C) flowmeter, D) hose to the aluminum
handpiece, and E) aluminum support.

Figure 4. Closeup of the aluminum handpiece. A) photosynthetic
chamber, B) gas regulator, C) inlet gas conduct,
D) inlet tube, E) outlet tube, F) trigger, G) clamping
lever, and H) soda-lime container.

 

Figure 3.

 

Figure 4.

 

82

Figure 5. The apparatus used for 14CO uptake measurements-
under field conditions. A) aluminum support
with the 14C02 bottle, B) aluminum handpiece,

C) light sensor (PAR), and D) light meter.

Figure 6. Some of the complementary materials used in the
14C02 uptake determination in the field. A) 22 ml
scintillation vials containing 1 ml of N08;

B) black plastic, C) glass with a zinc-oxide
glycerol mixture, D) stopwatch, and E) notebook.

83

 

Figure 5
Figure 6.

84

pistol grip, two transparent plexiglass jaws (which house a valve to
regulate the flow rate, and two photosynthesis chamber gaskets), a
lockrrelease trigger, and a soda-lime absorbing column. The chamber was
9.5 mm in diameter and 5 mm in height.

A leaf section of the central leaflet of a fully expanded leaf was
exposed to 14C02 by attaching the leaf chamber to the leaf and allowing
the gas to flow on both sides of the leaf. In preliminary experiments,
it was found that a flow rate of 130 mlmin"1 and an exposure time of
20 seconds produced optimum photosynthetic rates.

The exposed area of the leaf was marked by putting a zinc oxide-
glycerol mixture on the lower gasket before placing the leaf in the
chamber. A leaf-disc punch of the same diameter as the chamber was
used to punch out the exposed leaf area. The leaf disc was placed
in a 22 cm scintillation vial containing 1 m1 of NCS, a commercial
solubilizer (a solution of a quaternary ammonium.base in toluene)
from.Amersham-Searle Corp., Arlington Heights, Illinois. The vials
were protected from.the direct sunlight for any appreciable length of
time in the field by covering them with black plastic. The samples
were allowed to digest for 48 hours in the laboratory. After digestion
was complete, the solution was bleached with 1‘ml of saturated solution
of benzoyl peroxide (1 ml of benzoyl peroxide in 5 ml of toluene).
Eighteen ml of scintillation fluid (6 gr/l PPO and 75 mgr/l POPOP)
were added to the vial. The samples were counted for two minutes in a
scintillation counter (Beckman LS-lOO).

Carbon dioxide uptake by the bean leaf was calculated by using the
following formula

E.Spa.B.R.t

85
where:

BPs - CO2 uptake (mg dm.‘2 hr-l)

C - sample counts per minute

B - background counts (leaf sample without exposure ll‘COZ)

a - conversion factor from.umoles to mg C02 (.44)

K - constant to change seconds to hours and cmzzto dm2

(3.6 x 10‘5)

E - efficiency of the counting process (.80 to .85)

Spa - specific activity of the labeled gas (.75 uCi‘umole-l)

B - leaf sample area (.95 cmz)

R . conversion factor for dpm to uCi (2.2 X 106 dpm uCi‘l)

t s 14C02 exposure time (20 sec)

Carbon dioxide uptakes rates of both cultivars under the two light
environments were usually measured between 11:00 a.m. and 1:00 p.m. EDT
at selected levels of plant height during the growing season. For each
‘ 14C02 uptake sample the PAR was measured by placing the light sensor
in the same orientation as the leaf (hereafter termed leaf PAR).

Starch status in the roots (ground level) and stems (every third
internode of main axis) was determined by using an iodine-potassium
iodide starcbrindicator (IKI) solution (.3 gr of iodine; 1.5 gr
potassium iodide; and 100 ml water; Johansen, 1940). In each plot five
‘plbnts were randomly chosen and starch accumulation was estimated on a
“visual seal of l to 5 (Salazar ggual., 1977) from fresh sections to each
«of which had been applied 3 to 4 drops of IKI.

RESULTS AND DISCUSSION
Leaf inclination

The results obtained in the experiment of 1976 (Chapter 2) indicated

tfluat leaf inclination (leaf angle) is a very important factor which

’-

86
affects light penetration in the bean plant canopy. Therefore, more
careful measurements of this parametere were made in the present
experiment.

Measurements of leaflet area were necessary for the estimation of
leaflet orientation. For this purpose leaflet length and width were
taken simultaneously with leaflet inclination and azimuth. At 40 dap,
100 leaflets from each of Seafarer and NEP-Z, growing in the sun
environment, were sampled. For each leaflet, width and length were
measured and the area determined with a leaf area meter (Lambda
Instruments Model LI-300). These data were used to calculate regression
equations to estimate Seafarer leaflet area (Leaflet area - 1.7884 +
0.8455X, R2 - .9214) and NEP-Z leaflet area (Leaflet area a 1.1700 +
.9604X, R2 - .9433) by knowing the length X width of the leaflet (X in
the above equations in cm?).

Leaf area distributions as a function of leaf inclination of
Seafarer and NEP-Z grown under the sun environment are presented in
Figure 7. The canopy of Seafarer was found to have a greater frequency
of vertical leaves, while NEP-Z had a greater frequency of horizontal
leaves. Seafarer and NEP-Z, according to their leaf angle distributions,
could be calssified as erectophile and planophile foliar structures
respectively, using de Wit's system (1965).

At 49 dap, leaf inclination measurements of Seafarer grown under
the sun environment were made at 8:30 a.m. 12:00 a.m. and 3:00 p.m. EDT.

IEAB.above the plants at these times were 800, 3,200, and 3,600 uE cm"2

-1
sec. , respectively. The results are presented in Figure 8A. In the
morning, Seafarer had a planophile foliar structure which changed to
«tifferent degrees of erectophile as the light intensity increased during

the day. At each sampling time (at 49 dap) leaf inclination data were

87

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Table 1. Average leaf angle by plant strata of Seafarer at 45 dap grown
under the sun environment.

 

 

Time Plant strata (cm)
O'é 10 10 - 20' 20'- 30' 30 - 40 Mean
8:30 a.m. 16.95 29.30 35.70 39.32 31.20
12:00 a.m. 42.82 52.64 62.24‘ 60.84 ' 54.71

3:00 p.m. 47.61 '64.92 66v66 67.29 63.86

 

90
also taken by plant strata. The results at 3:00 p.m. are presented in
Figure 8B. Similar trends in leaf inclination.were observed at the
other sampling times. Figure 8B shows that the degree of erectophile
structure increased from the bottom to the top of the plant canopy.
In Table 1 is presented the average leaf angle by plant strata of
Seafarer at 49 dap grown under the sun environment. These date indicate
that leaf inclination of Seafarer changed during the day'and increased
fromthe bottom to the top of the plant canopy.

Average leaf angles of Seafarer and NEP-Z in the sun and the shade
environments, during the growing season, are presented in Table 2. Both
cultivars showed similar trends, however, Seafarer had=higher average
leaf angles than NEP-2. Their values increased and then decreased
during the growing season. The average leaf angle increased fromfithe
bottom (0 - 10 cm) to the top of the plant canopy (40 4 50 cm) for both
cultivars on all sampling dates. A similar trend was observed for the
leaf angle values at any plant height. The shade environment reduced
the average leaf angle of Seafarer and NEP-2 by 22.54% and 23.22%,
respectively.

Leaf area distribution as a function of leaf inclination.and
average leaf angle clearly showed that the leaf angle changed during the
day; It increased from the morning to the afternoon and from.the bottom
to the top of the plant canopy.

Hazimum photosynthesis of the plant canopy is found when leaf
:tnclination changes gradually from 900 degrees at the top layer to
0° degrees at the lowest layer of the canopy (Loomis and Williams,
JP969; Kuroiwa, 1970). The higher phtosynthesis is caused by the more
tuiiform.distribution of light over the leaves and the curvilinear

nature of the photosynthetic light response curve. Verhagen _e_t a_l..

91

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92
(1963) stated that the "ideal foliage" consists of layers with

continuously changing inclination so that available light is evenly
spread over all available leaf area. Under this consideration Seafarer
has a better plant canopy structure than NEP-Z because it has higher
leaf inclination and allows more light penetration in the canopy than
NEP-Z.

Leaflet orientation depends on the relative turgor of motor cells
on dorsal and ventral sides of the pulvinus, an organ at the base of
the leaflet (Satter 35 al., 1970a). Potassium (K+) flux is involved in
turgor changes in Mimosa pudica (Allen, 1979), Albizzia jglibrissin
(Satter £2 31., 1970b), and Trifolium repens (Scott 25 31., 1977).
Phytochrome has been suggested to be the mechanism for Rf flux and KT
movement is at least partly the result of changes in membrane permeability
and/or transport of K+ in the motor cells of the pulvini (Satter and
Galston, 1971; Setty and Jaffe, 1972). Breeding for efficient and
uniform light distribution in a bean canopy would have to be conducted
‘with consideration given to leaf inclination.

Leaf azimuth

Simultaneous measurements of leaf inclination and leaf azimuth were
made during the growing season. The results of the X2 (Chi-square)
Test, using the number of leaflets as variable, for random azimuthal
distribution for Seafarer and NEP-Z under both light environments are
presented in Table 3. Neither Seafarer nor NEP-Z had leaves oriented
'more frequently for any particular azimuth. Leaf area distribution
(2 of total) as a function of azimuth angle for Seafarer and NEP-Z,
after 49 and 50 dap, respectively, is presented in Table 4. Figure 9
'represents graphically the data of Table 4 for Seafarer under the sun

environment. Apparently leaves of Seafarer under the sun environment

 

93

Table 3. X2 (Ch-square) Test for random.aximuth leaf orientation for
Seafarer and NEP-Z during the growing season.

 

 

 

 

 

 

 

 

 

 

Date'(dap) Light env. X2 p
35 Seafarer sun 4.4789 .900
35 NEP-Z sun 7.3104 .500
42 Seafarer sun 4.3724 .900
42 NEP-Z sun 7.1136 .500
49 Seafarer sun 5.7959 .900
49 Seafarer shade 3.1305 .900
50 NEP-Z sun 2.9168 .900
50 NEP-Z shade 2.7109 .900
56 Seafarer sun .6432 .995
56 Seafarer' shade 3.2593 .900
59 NEP-Z sun 6.0993 .750
59 NEP-Z shade .5995 .995
64 NEP-Z sun 2.8540 .900
64 .NEP-Z vshade .7174 .995
Table 4. Leaf area distribution (Z of total) as a function of azimuth
for Seafarer and NEP-Z after 49 and 50 dap, respectively.
Seafarer- NEP-Z
sun shade sun shade
.Azimuth 8:30 am. 12:00 am. 3:00 pm 1:00 pm 12:00 am. 1:00 pm
0- 45 17.05 15.34 17.84 9.39 12.98 14.96
45- 90 17.21 20.25 17.54 18.01 10.62 10.51
90—135 8.51 12.44 13.85 15.79 12.99 15.30
135-180 9.21 8.40 14.95 16.58 13.06 14.02
.180-225 11.04 10.00 9.82 11.13 12.77 11.16
225-270 5.61 8.17 6.26 9.75 12.31 11.57
.270-315 14.84 14.03 13.19 8.56 12.78 10.78
.315-360 12.49 10.39 6.56 10.78 12.99 11.70
X2 ., 3.3110 5.7959 10.4307 3.1305 2.9168 2.7109

P .900 .500 .250 .900 .900 .900

 

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95

had more leaves oriented in the northeastern azimuth which became more
prominent in the afternooni, This could be due to the direction of the
prevailing winds. But no statistical significance was found for any
azimuth orientation.

Shell 35 21, (1974) observed that bean leaves had a northeasterly
azimuth in the morning which changed to a northerly azimuth in the after-
noon. But they did not give any explanation for this behavior. However,
all four plant species observed by them (sunflower, beans, cucumbers,
and peppers) showed preference for a northeasterly azimuth orientation.
Soybean plants have a random azimuthal distribution (Blad and Baker,

1972; Lemeur, 1973), as well as broad beans (Ross and Nilson, 1967).

 

Corn plants have a marked preference for azimuthal direction perpendi-
cular to the row (Ross and Nilson, 1967; Loomis and Williams, 1969;
Lemeur, 1973). Sunflower plants have three preferential directions due
to the spiral phyllotaxy of the leaves which is equal to 120° (Lemeur,
1973).
Leaf area distribution with plant height

Light models of plant communities require the distribution of LAI
with plant height. Leaf area distributions for Seafarer and NEP-Z
as a function of plant height are presented in Figures 10 and 11,
respectively. Leaf area distributions with height for Seafarer and NEP-Z
under the sun environment for this experiment were similar to those
observed in the previous experiment (Chapter 2). Seafarer had its
:maximum leaf area at approximately the middle of the plant height with
equal leaf area toward the bottom or the top of the plant canopy; NEP-Z
'had.its maximum leaf area at higher levels and more leaf area in the top
than in the bottom of the canopy. Both cultivars, when grown under the

shade environment, showed 602 less leaf area in the lower layers. This

96

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is visualized by higher values of leaf accumulation at .75 and .8
values of cumulative leaf area for Seafarer and NEP-Z, respectively.
Leaf area

The time courses of development of LAI for Seafarer and NEP-2 are
presented in Figure 12. Both cultivars had lower LAI's than in the
previous year (Chapter 2). The shade environment increased the LAI of
both cultivars, primarily by affecting leaf size (Figure 13A and Table
5), since the number of branches and number of nodes were not affected.
The bean plants were shaded 3O dap when they had formed branches and
the number of nodes had been determined by the genetic potential of
each cultivar.

Dale (1964) observed that the pattern of growth at the stem apex
of been plants was highly determinate and the number of leaf primordia
produced was independent of environmental factors. Dale also found
(1965) that leaf size and the rate of leaf unfolding was a parabolic
function of light intensity. This may explain why, in this experiment,
an increase of bean leaf size was found under shaded field conditions;
Crookston gt al., (1975) observed a decrease in bean leaf size due to
shading, working in crontrolled-environment chambers. Segovia and Brown
(1978) found that under field conditions, soybean leaf area increased
under 502 of sunlight. There was an effect of the shade environment on
the expansion of the bean leaf. This could originate either from a
diverson of more material to the leaves under the shade conditions or
:from.the development of a larger leaf area from the same amount of dry
nuatter, i.e., by alteration of the specific leaf dry weight (SLDW).
{Fable 6 shows that the shade environment did not affect the amount of
jleaf'dry matter in relation to the whole plant; however, the SLDW was

reduced in both cultivars by the shade environment (Figure 13B and

Table 7) .

 

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Leaf size

Specific leaf dry weight

(cu-2)

( gr/ce2 x lO—l' )

100

’ A
a
,-’ \-
I '\
.’ s
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e- ‘
s
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.\0_0
' .-———w. Seafarer: sun env.
.-.—.qp- Seafarer: shade env.
.. --.. NIP-2 : sun env.
4-u-u—41NEP-2 : shade env.
. B
./.\o
./.‘ x.
I; ““.----_._“--.l
e/‘./ ’
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...- -... NEP-Z : sun env.
._»_..._.NEP-2 : shade env.
h.n-*— ** ‘A ‘ ** ‘

 

 

41. 48 55 82 60 76
' Days after planting

Figure 13. Size of the central leaflet (A) and specific

leaf dry weight (B) of Seafarer and HEP-2
during the growing season at two light
environments.

 

101

Table 5. Analysis of Variance (ANOVA) for leaf size during the growing

 

 

 

session.
Source of variance df MS F
Treatments (T) 3 776.3767 78.63**
sun vs. shade 1 1088.5948 llO.25**
Sea sun vs. Sea shade 1 213.5372 21.62**
NEP-Z sun vs. NEP-Z shade l 1027.0396 104.01
Replications 2 p 1.9845
Error (a) 6 9.8736
Date of sampling (D) 4 121.3975 15.26**
D X T 12 10.9124 1.42
Error (b) 32 7.6538

 

** Significant at the 1% level

102

Table 6. Leaf dry weight/Plant dry weight ratio of Seafarer and HEP-2
during the growing season.

 

 

 

 

 

 

 

Seafarer NEP-Z
Date
dap sun env. shade env. sun env. shade env.
Leaf d. w'/ Plant d. w

34 .69 .69 .67 .67

41 .68 .67 .57 .61

48 .58 .59 .54 .56

51 .50 .54 .49 .48

62 .35 .39 .45 .45

69 .27 .30 .32 .31

 

103

Table 7. Analysis of Variance (ANOVA) for specific leaf dry weight
(SLDW) during the growing season.

 

 

 

 

Source of variance_ df , 3 MS F

Treatments (T) 3 530.3466 44.52**
sun vs. shade env. 1 793.4200 66.61**
See. sun vs. Sea. shade~ 1 456.5358 38.32**
NEP-Z sun vs. NEP-2 shade 1 341.0841 28.63**

Replications 2 14.2682

Error (a) 6 11.9110

Date of sampling (D) 4 18.6434 3.25**

D X T ' 12 11.6180 2.02

Error (b) 32 5.7329

 

** Significant at the 12 level

104

Canopy photosynthetic profiles

Photosynthetic rates, measured by the 14CO2 techniques as CO2
uptake rates, of Seafarer and NEP-Z canopy profiles are presented in
Table 8. All plant strata were sampled in each cultivar with the
exception of those leaves at the upper most strata, because only fully
expanded leaves were considered and to have uniform number of strata
for comparison purposes among cultivar and light environments. A
general trend can be observed. Carbon dioxide uptake rates at all
sampling dates increased from the bottom to the top of the plant for
both cultivars. Maximumco2 uptake rates for each plant stratum were
observed at the time of initial pod filling, 58 and 71 dap, for Seafarer
and NEP-Z, respectively. Seafarer generally had higher rates of uptake
at all canopy levels than did NEP-Z. The shade environment affected‘

CO uptake rates of both cultivars, i.e., during maximum CO uptake,

2 2
the shade environment reduced the CO2 uptake rates of Seafarer and
NEP-2 by 55.19% and 30.54%, respectively. This resulted in a signifi-
cant cultivar X treatment interaction (Table 8). There were signifi-
cant statistical differences between Seafarer and NEP-Z canopies, light
environments, and plant strata in the rate of CO2 uptake in all sampling
dates (Table 9). Some interactions were also significantly different
from zero.

In general, the observed photosynthetic rates were in the range of
‘previously reported values for bean leaves (Howe, 1962, 1964; Charter
3331., 1970; Austin and MacLean, 1972; Crooksten _e_t__a_1_., 1974; Sestak
535.31., 1975; Feet 35 91, 1977). Frazer and Bidwell (1974) observed
in beans a pattern of photosynthesis with age that is repeated in each

leaf} Apparent photosynthesis of individual bean leaves rose to a

maximmn and then slowly declined with time. However, it increased with

 

105

 

 

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106

 

 

 

 

 

 

cums. mean. mm. «N.H ammm. smmm. m: uouum

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107

the appearance of a new leaf or during flowering. They concluded that
photosynthesis was, to a large extent, controlled by or dependent on
intrinsic factors in each leaf and by extrinsic events in other parts
of the plant. Neales and Incoll (1968) suggested that the rate of
photosynthesis is regulated by the interactions of the accumulation of
assimilates within the leaf, the rate of transpiration from the leaves,
and the demand of assimilates in other parts of the plant. Ormrod
(1963) observed that net carbon dioxide exchange rates of bean leaves ‘
also increased in the linear phase of increase in pod dry weight.

Woodward and Rawson (1976) found similar net photosynthesis patterns

 

‘with age for soybean leaves. Peet 35 a1. (1977) reported that photo-

37

synthetic rates of been leaves were highest at early pod development

and differences between cultivars were observed. Victor £5 31. (1977)
found that leaf apparent photosynthesis rates of inbred, hybrid and
open-pollinated corn plants were affected by leaf position and declined ,
as plants aged;

The observations reported here are in keeping with results reported
by the above authors. The CO2 uptake rates were highest at the upper
most measured strata of the bean plants which was probably the result
of younger leaves and higher demand for assimilates since most of the
pods are located in these levels. Under the shade environment, similar

C0 uptake rate patterns were observed, although the uptake behavior

2
may indicate that the shade environment induced quantitative changes
of the photosynthetic mechanism.of the bean leaves and/or lower demand
for assimilates.

Relationship between photosynthesis and leaf PAR

Photosynthetic rates of Seafarer and NEP-2 canopies as a function

of the incident PAR on the leaves (leaf PAR) are shown in Figure 14 to

11)8

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109

 

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111

 

 

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112

16. Leaf PAR.was generally over 700 uE mfz sec“1 for leaves of both
cultivars under the sun and shade environments, with the exception of
the bottom leaves, 58 and 65 dap, which was around 60 HR mfz sec-l.
Photosynthesis of bean leaves becomes light saturated at 700 to 900

2 sec-1 (Charter gt 31., 1970; Austin and MacLean, 1972, Crooksten

uEm-
‘ggugl., 1964). This clearly indicates that enough light for photo-
synthesis penetrated into the canopy of these cultivars.. Neither

Seafarer nor NEP-2 canopies completely covered the ground even at

“Er

maximum LAI. This could explain why the bottom leaves received enough

light for photosynthesis, since light came from almost all directions

 

and not only from.the top of the plant canopy. However, it is inter- i
eating to observe that when PAR was around 1300 HE mfz sec”l over the top 4”
of the plants on a cloudy day (Figure 15), the Seafarer canopy had better '
light penetration than the NEP-Z canopy. Carbon dioxide uptake rates
were positively correlated with leaf PAR for both cultivars (Table 10).
For calculation of simple correlations of Table 10, both light environ-.
ment data were considered together in each cultivar. These results
suggest that the differences between photosynthetic rates under the sun
environment in each cultivar were independent of leaf PAR; however,
leaf PAR.was an important factor for differences between light environment
Relationship between photosynthesis and SLDW
There was a positive relationship between plant strata and specific
leaf dry weight (SLDW) and between plant strata and photosynthetic rates
(Table 10). This means that from the bottom to the top of the plant
canopy both photosynthesis and SLDW increased. An attempt was made to
estimate the relationship between photosynthesis and SLDW. Five central
leaflets were sampled for each plant strata for SLDW determinations

‘when CO uptake was measured.

2

 

113'
Photosynthetic rates of Seafarer and NEP-Z canopies as a function

of LSDW are shown in Figures 17 and 18. In general, plants under the

shade environment had lower CO2 uptake and lower SLDW than under the

sun environment. Seafarer under the sun environment had the highest

CO2 and the highest SLDW values, while NEP-Z under the shade environ-

ment had the lowest values for both C02 uptake rates and SLDW. At
43 and 50 dap, (Figure 17), under the sun environment. Seafarer had

both higher C0 uptake rates and SLDW than NEP-Z. These differences

2
were still shown at 58 dap (Figure 18 ), but became less apparent at

65 dap (Figure 18). Seven out of the ten simple correlation coefficients

 

between C02 uptake rates and SLDW'were significantly different from
zero at the 52 level (Table 10), which indicates a positive relation-
ship between these two leaf characteristics.

Although genetic differences in apparent photosynthesis rates
have been reported, the physiological bases for genotypic variation
remains obscure in most species studied. Gaastra (1962) has stated
that photosynthesis is influenced by three main processes: 1) a photo-
chemical process, 2) a diffusion process associated with the transport
of co to the co -fixation side, and 3) biochemical process which I

2 2
includes the fixation and chemical reduction of C0 .

2

There is some evidence that SLDW might be used in breeding programs
for photosynthetic efficiency. Positive correlation between net photo-
synthesis rates and SLDW has been reported in alfalfa (Medicago sati!§_
‘L.) Pearce gt 21., 1969; Wblf and Blazer, 1972), soybeans (Dornhoff
and Shibles, 1970), oats (Agape spp.) Criswell and Shibles, 1971).
THeishel and Musgrave (1969) did find a significant correlation between
specific leaf fresh weight and net photosynthesis. Although I found a

positive correlation between CO uptake rates and SLDW, further work

2

114

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116

will be needed in determining the feasibility of SLDW as an index for
leaf photosynthetic efficiency in beans because of the limited number
of bean genotypes used in this study.

Light intensity during plant growth affects leaf morphology,
chloroplast structure, and a number of component processes of photo-
synthesis. Plants grown at high light intensity have lower mesophyll
resistance (rm), thicker leaves, and greater amounts of the carboxy-
lating enzymes (Boadman, 1977). Crooksten gt a1. (1975) working with
bean plants grown under two light environments in a growth chamber,
found a positive correlation between apparent photosynthesis and leaf

thickness. They suggested that the increased intracellular resistance,

 

chloroplast structure and carboxylation enzyme of the shaded leaves '
was more important in reducing CO2 uptake than was the increase in
stOmatal resistance (rm). Louwense and Zweerde (1977) found, with
bean plants grown under different light intensities in field and under
growth chamber conditions, a positive correlation between apparent
photosynthesis, leaf thickness, and number of chloroplasts per unit
leaf area. They suggested that maximum.photosynthesis depended on

the number of chloroplasts. Nobel ggngl., (1975) reported that the
changes in photosynthetic rate induced by various irradiances during
leaf development resulted from changes in the mesophyll cell surface

area per unit leaf area rather than from changes in C0 exchange rate

2
(CER) and that CO2 residual resistance (rm) was related to the thick-

ness and cellular volume of the several soybean leaf tissues. They
concluded that characteristics internal to the cell, as opposed to

CO -resistances related to stomata, intercellular space, or cell

2

surfaces, were regulating CER.

117

Therefore, several factors are modified when plants are grown
under selected light intensities, and there is no concensus of opinion
concerning any one factor as the prime cause of the altered photo-
synthetic capacity.

Starch accumulation in roots and stems

The results of the experiment of the previous year (Chapter 2)
with respect to changes in stem and pod dry weights, suggested the
possible contribution of storage materials in the stem to the final
seed and pod dry weights. Adams (1975) reported differences in the
amount of carbohydrate stored in stems of Seafarer and NEP-Z. In
order to relate stem dry weight and starch accumulation, starch levels
in the roots and in every third internode (internode immediately above
the simple leaf was counted as 1), were determined by using iodine-
potassium iodide Starch indicator solution (IKI) as suggested by
Salazar 2531. (1977).

IKI determinations in the roots and 3rd internode of Seafarer
and NEP-Z during the growing season are shown in Figures 19 and 20.
Curves for the other internodes were similar to the 3rd internode in
each cultivar. In both cultivars after flowering, greater amounts
of starch started to accumulate in the roots than in the stems.
Seafarer had maximum IKI values for roots at 62 dap and for stems at
65 dap. After these dates IKI determinations in both roots and stems-
decreased and reach their lowest values at final harvest (79 dap).
NEP-Z had maximum IKI values for roots and stems at 62 dap. Thereafter,
IKI determinations started to decrease in both roots and stems with
the minimum values of IKI index of 4 and 3, respectively, at final
harvest (105 dap). This clearly indicates that starch was present in

the roots and stems of NEP-Z and it was not completely remobilized.

 

 

118

 

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121

The shade environment only reduced the amount of starch in roots and
stems of both cultivars and not the patterns of change in IKI values.

Ontogenetic changes in stem dry weight of Seafarer and NEP-Z,
under both light environments, are presented in Figure 21. Both stem
dry weight and starch accumulation in the stems were found to have very
similar patterns (Figures 20 and 21). Salazar ggnal. (1977) also
reported similar trends of starch accumulation in the roots and stems
of Seafarer and NEP-Z. Their IKI values were lower than the ones
reported here. During the last 3 weeks before final harvest of NEP-2,
the plants were exposed to unusual weather conditions of excessive
rainfalls. This might have changed the patterns of starch accumulation
in NEP-Z at this period. Nevertheless, there appears to be a cultivar
X environment interaction in the starch accumulation in roots and stems

of bean plants.

 

REFERENCES

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in,field beans. Ann. Rep. to the Rockefeller Foundation.

Allen, R. D. 1969. Mechanism.of the sesismonastic reaction in
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Austin, R. B. and P. C. Longden. 1967. A rapid method for the
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Austin, R. B. and M. S. M. MacLean. 1972. Some effect of temperature
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Blad, B. L. and D. G. Baker. 1972. Orientation and distribution of
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Bravdo, B. 1972. Photosynthesis, transpiration, leaf stomatal and
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Chartier, R., M. Chartier and J. Catsky. 1970. Resistances for
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Criswell, J. G. and R. M. Shibles. 1971. Physiological basis for
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Crookston, a. K., J. O'Toole, R. Lee, J. L. Oszm and D. D. Wallace.
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Crookston, R. K., K. J. Treharne, P. Ludford and J. L. Ozbun. 1975.
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Dale, J. E. 1965. Leaf growth in Phaseolus Vulgaris. 2. Temperature
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122

 

123

Dornhoff, G. M. and R. M. Shibles. 1970. Varietal differences in
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Dornhoff, G. M. and R. M. Shibles- 1976. Leaf morphology and anatomy
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Howe, G. F. 1962. Time course of the photosynthetic induction periods
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Howe, G. F. 1964. Time course of photosynthetic rhythms in Phaseolus
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Ross, Y. K. and T. Nilson. 1967. The spatial orientation of leaves
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Satter, R. R., P. Marinoff and A. W. Galston. 1970. Phytochrome
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CHAPTER 4

SUMMARY AND CONCLUSIONS

Two principal physiological processes can be considered for
improvement of crop yields: photosynthate production and photosyntate
partitioning to the economically important organs. The aims of this
investigation were to obtain information for increasing bean product-
ivity by optimizing the structure of the crop canopy and carbohydrate
partitioning. Therefore, it was necessary to define canopy architec-
ture characteristics relevant to light penetration, crop photosynthesis,
and ontogenetic carbohydrate partitioning. ‘For these purposes two
experiments were conducted: 1) in.the summer of 1976 at the B/B Research
Farm, Saginaw, Michigan, with four dry bean genotypes representing
different growth habits. The genotypes and growth habits were: a MSU
experimental line 31908, a narrow bush type (CIAT type I), b)
cultivar Seafarer, a normal bush type (CIAT type I), c) cultivar
NEP-Z, a narrow erect, short vine type (CIAT type II), and d) MSU
experimental line 0686, a determinate but very vigorously vegetative
type resembling CIAT type III). Plant spacing (47, 20, and 9 plants/m2)
was used to modify the canopy architecture; and 2) in the summer of 1977
at the Crop Science Research Farm, E. Lansing, with two genotypes:
Seafarer and NEP-Z. Light environments (full and 502 sunlight) were
used to modify the canopy architecture. The following conclusions are

based on the results of this study.

126

 

127

1. The vertical distribution of the area of green leaves varied
during the course of the growing season. Seafarer had its maximum LAI
at approximately the same plant height, 10-30 cm from.the bottom,
during the period Of 30 to 72 dap. NEP-Z and Lines 31908 and 0686 had
the distribution curves nearly symmetrical with respect to the LAI
maximum at the middle of the plant height at 30 to 70 dap, thereafter,
the maximum.shifted to higher plant layers.

2. All plant parts, independent of plant types, including leaves,
stems and pods, develop progressively later toward the top of the plant.
However, the difference in growth stage among plant parts was less in
the case of pods than for the leaves and stems. Consequently, the time
interval between vegetative and pod development was shorter toward the
top of the plant.

3. WLight distribution in the plant canopy changed with plant
height in an exponential manner and fit Bouguer-Lambert's law, with
relative illumination as an exponential function of LAI. Relative
light interception was closely associated with LAI and both showed
similar trends during plant development.

4. Extinction coefficient (k) values at maximum LAI were: .2615,
.3396, .4629 and .2993 for Seafarer, NEP-Z, Line 31908 and Line 0686,
respectively. K values were not significantly affected by plant
spacing.

5. Light penetration in the canopy was found to be greater in
Seafarer and lower in the Line 31908. NEP-2 and Line 0686 showed
intermediate values.

6. LAI, leaf angle, percent of ground cover, and the extinction
coefficient were the most important characteristics accounting for

99.222 of the variance in light penetration.

 

128
7. The studied plant spacings did not affect either seed yields

or yield components of the four plant types.

8. Relative Growth Rate (RGR) was higher for Seafarer and lower
for the Line 31908; NEP-Z and Line 0686 had intermediate RGR values.
Differences in RGR.were due to differences in Net Assimilation Rate (NAR)
rather than in Leaf Area Ratio (LAR). RGR.was affected by plant spacing.

9. Harvest Index (HI), independent of plant type, was affected by
plant spacing with the lowest HI values corresponding to the closest
plant spacing.

10. The trends of dry weight distribution suggested a movement of
material from leaves to stems and pods. Changes in stem dry weight and
pod dry weight were used to estimate the contribution of storage
material to the final seed and pod dry weight. There were differences
between plant types and plant spacings in the possible.contribution of
previously stored materials in the stems and petioles to the final pod
dry weight. Apparently, the changes in dry weight of the stems were
equivalent to the changes in dry weight of the pods at the bottom and
top strata of all plant types with the exception of Line 31908 at the
lowest strata where pods were not present. Storage material trans-
location from stems to pods was affected by plant spacing with its
highest values at the closest plant spacing.

11. The canopy of Seafarer was found to have a greater frequency
of vertical leaves, while NEP-Z had a greater frequency of horizontal
leaves. Seafarer and NEP-Z could be classified as erectophile and
phanophile foliar structure, respectively, by using de Wit's system
(1965). Leaf inclination changed during the day. In the morning
Seafarer had a planophile foliar structure which changed to different

degrees of erectophile as the light intensity increased and the sun

 

129

position changed during the day.- With respect to plant strata, the
degree of erectophile structure increaSed from.the bottom to the top of
the plant canopy. Average leaf angle of Seafarer and NEP-Z showed
similar trends during the growing seaSon, however, Seafarer had a
higher average leaf angle than HEP-2. Their values increased and then
decreased during the growing season. The shade environment reduced

the average leaf angle of Seafarer and HEP-2 by 22.54Z.and 23.22%,
respectively.

12. Neither Seafarer nor HEP-2, under either light enViranment,
had leaves oriented with more frequency for any azimuth."

13. The shade environment increased the LAI of Seafarer and NEE-2,
primarily hy.affecting leaf size, since the number of branches and
number of nodes were not affected. The bean plants were shaded 30 dap
when they had formed branches and the number of nodes had been
determined by the genetic potential of each cultivar. There was an
effect of the shade environment on the bean leaf, but not on.the'amount
of leaf dry matter in relation to the whole plant, howeVer, the specific
leaf dry weight was reduced in both cultivars by the shade environment.

14. Photosynthesis rates, measured by the 14CO2 techniques as COé
uptake rates, were in the range of previously reported values far been
leaves.- They increased from.battom.1eaves to top leaves for hath.

Seafarer and HEP-2. Maximum.co uptake rates for each plant stratum

2
‘were observed at the time Of initial pod filling, 58 and 71 dap, for

Seafarer and NEP-Z, respectively. Seafarer generally had higher rates
of uptake at all canopy levels than did HEP-2. The shade environment

affected the C0 uptake rates of hath.cu1tivars, 1. e. during the"

2

Imaximum.CO uptake, the shade enViranment reduced theCO2 uptake rates

2
of Seafarer and NEP-Z by 55.19% and 30.542 respectively.

130

15. There was a positive relationship between plant strata,
specific leaf dry weight and photosynthetic rates. This means that from
the bottom to the top of the plant canopy both photosynthesis and
specific leaf dry weight increased.

16. After flowering, greater amounts of starch started to accumu-
late in the roots than in the stems of Seafarer and NEP-Z. Seafarer
had maximum.starch accumulation in the roots at 62 dap and in the stems
at 65 dap. NEP-2 had maximum accumulation in both roots and stems at
62 dap. Thereafter, starch started to decrease in both roots and stems
and disappeared at harvest time for Seafarer, while it was still present
in roots and stems of NEP-Z. The shade environment only reduced the
amount of starch but not the ontogenetic patterns. Similar trends
were observed for starch accumulation in the stems and stem dry weight.
There appeared to be a cultivar X environment interaction in the starch

accumulation in the roots and stems of bean plants.

 

   

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