MORPHOLOGICAL CHARACTERISTICS AND YIELD OF

GRAIN SORGHUM (Sorghum bicolor L. Moench)

by

JOHN C. BICKEL, B.S.

A THESIS

IN

CROP SCIENCE

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the degree of

MASTER OF SCIENCE

Approved

Accepted

August, 1983

/ -I

r;i',h , " ACKNOWLEDGMENTS

The author wishes to thank the chairman of the committee. Dr. Kent

R. Keim, for his many helpful suggestions and patience during the

preparation of this manuscript. The aid of the members of the

committee. Dr. R. C. Jackson and Dr. D. R. Krieg, is appreciated as

well. For their help during the collection of the data, thanks go to

Pam Nafzger and Michelle Fritz. The patience and understanding of my

wife, Connie, is deeply appreciated. Many thanks are given to my

father and mother. Bill and Priscilla Bickel, who have supported me at

all times in many ways. Thanks are extended to the typist, Jan Readio.

Acknowledgement is also given to the Dryland Crop Improvement Grant,

without which this work and thesis would not have been possible.

11

TABLE OF CONTENTS

ACKNOWLEDGMENTS ii

LIST OF TABLES v

I. INTRODUCTION 1

II. REVIEW OF LITERATURE 3

Physiological Features 3

Leaf Area and Yield 4

Panicle and Yield 6

Stalk and Yield 7

Number of Leaves 8

Height of Plant 8

Morphological Trait Correlations with Grain Yield 9

III. MATERIALS AND METHODS 12

Germplasm 12

Field Layout 12

Characters Investigated 13

Statistical Analysis 14

IV. RESULTS AND DISCUSSION 16

Morphological Characteristics 16

Dry Weights 19

Grain Yield and Related Traits 23

Morphological Trait Means 25

Dry Weight Means 33

Mean of Grain Yield and Related Traits 34

111

Correlations Between Morphological Traits, Dry

Weights, and Grain Yield 35

V. SUMMARY AND CONCLUSIONS 48

APPENDIX 51

REFERENCES CITED 53

IV

LIST OF TABLES

1. Analysis of variance (mean squares) of data on morpholog­ical traits of inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation levels (1980) 17

2. Analysis of variance (mean squares) of data on morphologi­cal traits of inbred lines over water levels (1980). . . . 18

3. Analysis of variance (mean squares) of data on plant dry weights for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation lev­els (1980) 20

4. Analysis of variance (mean squares) on data for plant dry weights over water levels (1980) 21

5. Analysis of variance (mean squares) of data on plot grain yield and related traits for inbred lines grown under pre­plant plus one (PP +1) and preplant plus three (PP +3) irrigation levels (1980) 22

6. Analysis of variance (mean squares) on data for field plots over water levels (1980) 24

7. Means of morphological traits for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels and over water levels (1980) 26

8. Means of plant dry weights and plot grain yield for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation levels and over water lev­els (1980) 31

9- Correlations of morphological traits and dry weights on morphological traits and dry weights for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels (1980) 36

10. Correlations of morphological traits and dry weights on morphological traits and dry weights for inbred lines over water levels (1980) 37

11. Correlations of grain yield and related traits on morpho­logical traits and dry weights of inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels (1980) 39

V

12. Correlations of grain yield and related traits on morpho­logical traits and dry weights of inbred lines over water levels (1980) ^0

13. Correlations between grain yield and related traits for inbred lines grown under preplant plus one (PP + l)i preplant plus three (PP +3) irrigation levels and over water levels (1980) 47

VI

CHAPTER I

INTRODUCTION

Grain sorghum (Sorghum bicolor L. Moench) is an important crop in

the United States, particularly in the semiarid region of the

Southwest. The seed or grain of sorghum is an important economical

part of the plant used primarily for feeding livestock and industrial

purposes in the United States. Grain sorghum is important for human

consumption in parts of China, India and Africa.

Texas grain sorghum acreage has decreased yearly from a high of 3

million hectares harvested in 1975 to a present estimated level of 1.5

million hectares. During the same period, on the semiarid Rolling

Plains region, the sorghum area decreased 66%. Average yield in the

period 1975 to 1980 ranged from 995 kg/ha to 2386 kg/ha (Clark and

Pietsch, 1980).

Grain yield of sorghum is related to previous environmental in­

fluences during the growing season and effect of such influences on

various physiologic systems during development. Water and temperature

are the major factors influencing yield in the Rolling Plains region

and are largely responsible for the wide variations in grain yield.

Effects such as those caused by water stress are manifest through

influences on various morphologic characteristics of the developing

sorghum plant. An understanding of these effects could provide

information useful in developing desirable types in a sorghum genetics

and breeding program.

Previous studies with wheat indicate a potential for use of

various morphological traits at various growth stages (especially

anthesis) and their association with grain yield as a selection tool

in a breeding program. However, little information exists for sorghum

concerning the relationship of grain yield with morphologic traits

during development.

The main objective of this study was to determine if biologically

important relationships exist between grain yield and various

morphologic characters for eight sorghum genotypes grown under two

water levels. If genotype by water level interactions occur, then

hybridization and extraction of segregates suited to environmental

conditions will be possible.

CHAPTER II

REVIEW OF LITERATURE

Physiological Features

Blum (1974) evaluated sorghum cultivars and found low initial

water use prior to anthesis relative to the total used at maturity to

be a positive drought response. Of two sorghum genotypes grown under

water stress in the field, Stout, Kannangara and Simpson (1978)

observed one genotype to be capable of responding by shortening

developmental sequences, thus taking advantage of early season

moisture. When compared to the irrigated treatment, this genotype was

found to be in a later stage of inflorescence development.

According to Acevedo, Hsiao and Henderson (1971), water uptake

provides impetus for cell enlargement. Water use efficiency is the

ratio of dry matter produced to water used. Under conditions of

limited moisture, there is an optimal level of vegetative growth,

depending on the available water supply, for maximum grain yield

(Fisher and Kohn, 1966b).

Fisher and Kohn (1966b), working with wheat, found large

differences in vegetative growth caused relatively small differences

in evapotranspiration rates when soil moisture was adequate. An

increase in total dry matter of lOOg/m^ was associated with an

increase in cumulative evapotranspiration of 1.27 cm.

Sorghum has been shown to use water more efficiently for grain

production than some other grain crops (Major and Haman, 1981;

Sanchez-Diaz and Kramer, 1971; El-Sharkaway and Hesketh, 1964). Major

3

and Haman (1981) found that sorghum used water more efficiently than

barley (Hordeum vulgare L. 'Gait') or wheat (Triticum aestivum L.

'Neepawa'). Kernel growth ceased after whole-plant growth ceased for

barley and wheat, but for sorghum there was continued kernel growth.

Sanchez-Diaz and Kramer (1971) compared corn (Zea mays L.) and sorghum

water deficits on leaf segment samples. The greatest deficit of

sorghum was only 29% at a leaf potential of -15.7 bars while corn was

56.6% at -12.8 bars. This indicated that sorghum retained a larger

fraction of its water at given water potentials. El-Sharkaway and

Hesketh (1964) used temperature and water stress as treatments to

compare young fully expanded leaves of sorghum (Sorghum vulgare L.

'Hegari'), cotton (Gossypium hirsutumL.), sunflower (Helianthus annus

L.), and soland (Thespesia populnea L.). Sorghum did not cease

maximum photosynthesis until the leaves were curled. Other species

used were visibly wilted before photosynthesis was depressed by water

deficit.

Leaf Area and Yield

Agricultural crop yield is usually measured in terms of weight of

crop per unit of land area, and is an integration of effects of

various factors on many physiological processes and morphological

components (Moss and Musgrave, 1971; Watson, 1942).

McKree and Davis (1974) applied five cycles of soil water deficit

to sorghum under hot dry field conditions. Declines in leaf area were

found to be due to decreased leaf cell numbers and decreased cell

size. Decreases in leaf area due to stress were primarily the result

of decreased cell division.

Several studies indicate leaf area to be a major determinant of

crop yield. From four field experiments in 1961 and 1962, Elk, Kalyu

and Hanway (1966) found that grain yield of corn was linearly related

to leaf area index (LAI) days. Grain yields were most closely related

to LAI measurements closest to day of first silking. In a study of

twelve sorghum genotypes, Leeton (1978) observed total leaf area to be

highly correlated with yield.

Leeton (1978), working with sorghum, took leaf area measurements

at several stages of plant development from panicle initiation through

bloom plus 30 days. She found total leaf area at bloom to be highly

correlated with yield, but negatively correlated with photosynthetic

rate. This negative correlation was explained as the result of sink

size being a function of total leaf area. Excess leaf area existed in

relation to sink strength, and photosynthetic rates per unit area

could be reduced while maintaining high yields. Earlier observation

of Wareing, Khalifa and Treharne (1968) that reducing leaf number

results in increased photosynthetic rates per unit area tends to

support Leeton's work. Stickler and Pauli (1961) used leaf removal to

determine the contribution of individual leaves to seed weight.

Although there were decreases in total grain yield, the relative yield

per unit leaf area increased. This indicated that as leaves were

removed from a sorghum plant the remaining leaves were able to

compensate for loss of photosynthetic area.

Reduced yield due to reduced leaf area has been reported by

several workers. In a study using hybrid corn, Acevedo, Hsiao and

Henderson (1971) found that under increasing water stress the rate of

leaf elongation decreased. Using a glass enclosure in the field to

obtain water stress. Stout, Kannangara and Simpson (1978) observed a

reduction in the number of living leaves on tillers and main stems in

two varieties of sorghum. In a study involving defoliation of Midland

grain sorghum. Stickler and Pauli (1961) reported decreased yields,

but increased photosynthetic efficiency per unit area.

Panicle and Yield

Photosynthetic contribution of the inflorescence to grain yield

has been demonstrated by many workers for the small grain crops. In a

study using barley, Porter, Pal and Martin (1950) observed the ear to

contribute 30% of the plant dry weight. This dry weight contribution

was only to the grain. Birecka, Skupinska and Berstein (1967), in a

study of spring barley, reported that the contribution of the ear to

photosynthetic activity of the shoot was 25% to 30%. At later stages

of growth this value increased to 80%. In a study with greenhouse and

field experiments and four wheat varieties, Watson, Thorne and French

(1958) concluded that the higher yields of two varieties were due to

increased photosynthesis in the ears. This increased photosynthesis

was associated with greater weight of ears. Using old and new

varieties of spring and winter wheat, Watson, Thorne and French (1963)

found that after ear emergence, ear dry weight of the new varieties

was significantly greater. Grain yield of new varieties was

significantly greater, but Leaf Area Index was not.

Eastin and Sullivan (1969) found that sorghum panicles having

more open growth pattern had higher head dry weights at all stages of

growth compared to compact type panicles. They attributed this

difference to the higher rate of photosynthesis occurring in open type

panicles. Fisher et al. (1976) has found the average contribution of

the inflorescence to the grain yield to be 13%. Eastin (1968)

observed that sorghum panicles intercept 40-48% of the total energy

due to sunlight from 9 A.M. to 3 P.M.

Stalk and Yield

The contribution of the stalk to the total dry matter of the

plant and its contribution of assimilates through translocation to the

grain yield has been studied extensively- Using pollinated and

unpollinated corn hybrids, Campbell (1964) found more total dry matter

to accumulate in the stalks of the unpollinated hybrids. In a growth

chamber study using wheat, Wardlaw (1967) found that when plants were

subjected to stress, assimilates moved out of the stalk to fill the

ear. The leaves were found to supply very little assimilates during

the grain fill period. Using sorghum, Herbert et al. (1982) concluded

dry matter stored in the plant prior to anthesis was later

translocated to the grain in some hybrids they tested. Fisher and

Wilson (1971) used dry weights of field grown plants to determine the

preanthesis contribution of assimilates was only about 12%. In a

study using maize having low leaf water potentials, Boyer (1976)

applied water stress during early grain fill. Photosynthesis ceased

at -1.8 to -2.0 Mpa (megapascals, 0.1 Mpa = 1.0 bar) and plants

remained inactive photosynthetically throughout the rest of the

season, but yielded 47% of controls. Shoot dry matter was reduced 21%

in stressed plants, being interpreted as evidence of translocation of

assimilates out of the stalk.

8

Number of Leaves

Sorghum varieties were shown to have four leaves in the embryo

(Clark, 1970). Additional leaves are initiated from the period of

planting to floral initiation, which is controlled by four maturity

genes (Quinby, 1972; Quinby, Hesketh and Voight, 1973). This period

has been shown to last about 30 days regardless of a variety's

maturity characteristics (Pauli, Stickler and Lawless, 1964).

Number of leaves of sorghum have been shown to decrease under

conditions of water stress. Using four different locations with

rainfall ranging from 31 mm to 413 mm, Vinall and Reed (1918) observed

reductions of from three to six leaves. They concluded lack of

moisture was responsible in part. In a dryland study of 21 varieties,

Sieglinger (1936) reported 19 to 27 leaves per stalk for Sorghum

vulgare Per. There were less leaves within a variety as planting date

became later. Bennett (1975) reported reduced leaf numbers for

sorghum under water stress.

Height of Plant

In sorghum, there are four known loci for height having a

cumulative but unequal effect. Significant fixable genetic and

environmental variation has been demonstrated for height of sorghum

(Hadley, 1957). According to Clegg (1969), plant height is an

important part of the crop canopy. On short stems, closely spaced

leaves may lead to serious shading of all but the top leaves. Tall

plants also tend to form a more complete canopy compared to shorter

plants under the same conditions. Working with tall mutants and the

dwarf plants they arose from, Hadley, Freeman and Javier (1965) found

that the heterozygous tall plants yielded more than the homozygous

dwarf plants. In a study using reciprocal crosses between 3-dwarf and

2-dwarf lines, Graham and Lessman (1966) reported that the tall (2-

dwarf) plants produced more grain than the short (3-dwarf) plants.

They speculated that more efficient light utilization by the tall

plants could be a factor in increasing grain yield.

Several workers have reported that water stress leads to a

decrease in plant height (Bennett, 1975; Stout, Kannangara and

Simpson, 1978). In a comparison of 3-dwarf and 4-dwarf isogenic

lines, Shertz (1970) observed reduced peduncle lengths for the 3-dwarf

lines. In a field study using sorghum under water stress, Bennett

(1975) reported decreased peduncle lengths for all genotypes tested.

Morphological Trait Correlations with Grain Yield

Most of the recent work involving associations of morphological

characteristics and grain yield have used common spring wheats

(Triticum aestivum L. aestivum group). Fisher and Kohn (1966b), using

a single variety of wheat, obtained a significant positive correlation

of 0.875 between grain yield and total dry weight at flowering.

Voldeng and Simpson (1967), working with seven lines of wheat,

obtained significant positive simple correlations ranging from 0.54 to

0.90. Correlations were calculated between grain yield and photosyn­

thetic areas for both high-yielding and low-yielding varieties. In

their leaf shading experiments, dry weight of grain increased

significantly when the flag leaf and ear were left unshaded compared

to any other plant part left unshaded. Walton (1969), in a study of

high quality hard red spring wheat and Mexican strains, reported

10

correlation coefficients for extrusion length showed a close positive

association with yield. In a study of 120 lines of wheat, Simpson

(1968) reported correlations of 0.84, 0.91 and 0.93 between grain

yield and flag leaf lamina area, flag leaf sheath area, and total

photosynthetic area, respectively. Briggs and Aytenfisu (1980), using

seven wheat genotypes and six seeding rates, reported the most

frequent and largest correlations with plot yield were obtained with

extrusion length. Correlations between flag, leaf lamina area and

yield, and flag leaf sheath area and yield were positive when

significant. Ramos et al. (1983), working with barley, took plant

samples every 15 days from the single stem stage to harvest. They

found highly significant positive correlations between both leaf dry

matter and total dry matter and the corresponding leaf area.

Previous research leads to the conclusion that physiological

systems as well as morphological characteristics are affected by water

stress. Studies have been conducted on the effects of stress on

photosynthetic rates and yield (grain or dry matter). However, few

studies have related the effects of stress on leaf area and related

morphological traits to grain yield of sorghum. This study was

designed: (1) to determine if genotypic variation exists with regard

to leaf area and associated morphological characteristics, (2) to

determine the effect of two environments on leaf area and associated

morphological characteristics, and (3) to determine the relationship,

if any, of leaf area and related morphological traits to grain yield.

This thesis represents part of a comprehensive study designed to

determine genotypic variation and interaction with water levels and

11

development of breeding and screening procedures to be used in a

genetics and breeding program for sorghum improvement.

CHAPTER III

MATERIALS AND METHODS

Germplasm

Eight inbred lines of Sorghum bicolor L. Moench were planted at

the Texas Tech University farm in northeast Lubbock County, Texas.

Inbreds used were TX 7000, TX 7078, NSA 440, SC 56-14, SC 35-14, R

9188, TX 2737 and SC 170-6-17.

Field Layout

Field design was a randomized complete block with four blocks

repeated over two irrigation treatments, preplant plus one irrigation

(PP + 1) and preplant plus three irrigations (PP + 3). Each plot

consisted of four rows 6.7 m long with 102 cm between rows. Plots

were planted June 4, 1980. Plants were spaced 9.84 cm apart giving a

plant population of 96,500 plants/ha. A propazine herbicide (Milo-

gard) was applied post-plant at a rate of 1.2 kg/ha. Plants were

sprayed with pesticide (Sevin) as needed for insect control.

Soil type was a Pullman clay loam approximately one meter deep.

Plots were fertilized at recommended levels. Soil of both treatments

was brought to field capacity with a preplant irrigation April 28.

Two neutron probe tubes were placed at random within the same inbred

line in each treatment in the first and fourth replication to monitor

soil moisture. Both treatments received an additional irrigation June

30 which brought the soil to field capacity. The PP + 1 received no

more irrigations after June 30. The PP + 3 treatment received two

additional irrigations to field capacity, July 25 and August 30.

12

13

Additional rainfall received from June 8 until September 10 was 107.8

mm. All cultivation practices were carried out as needed in both

treatments.

The 1980 growing season was extremely dry for an extended period

with no precipitation recorded from June 12 through July 26 (Appendix

Table 1). Corn earworms (Heliothis zea [Boddie]) were observed in

plots, and control was obtained by use of insecticide (Sevin).

Characters Investigated

Five plants per plot visually judged to be at 50% bloom were

harvested by severing the stalk transversely at the soil surface.

Measurements were then taken on the following morphological character­

istics. Plant height was the distance (cm) from the cut surface of

the stalk to the tip of the panicle. Peduncle length was the distance

(cm) from the flag leaf sheath to the basal node of the panicle. Leaf

area was calculated from the length of the lamina (excluding the

sheath) multiplied by the width of the lamina at its widest point

multiplied by 0.75 (Stickler, Wearden and Pauli, 1961).

Plants were separated into stalk, leaves and panicle and allowed

to dry at 50"C. Data were taken for each plant part dry weight. Head

weight was the mass of the panicle in grams excluding the peduncle.

Stalk weight was the mass in grams of the stem, leaf sheaths and

peduncle. Leaf weight was the mass in grams of the combined laminas.

Plant parts were weighed with a digital balance (Mettler).

After plants had reached maturity, 5.0 m of a center row were

harvested per plot for grain yield. Heads were weighed (kg) then

threshed using a plot harvester. The grain was then weighed again for

14

grain weight (kg). A digital moisture computer was used to determine

moisture percentage (%H20).

Measurements of morphological characteristics and grain yield

were used to make the following calculations:

1. Total leaf area - total of all the areas of all leaves on a per

plant basis (cm ).

2. Peduncle area - peduncle length times peduncle width times 3.14

(cm2).

3. Total photosynthetic area measured - the sum of total leaf area

and peduncle area on a per plant basis (cm ).

4. Threshing percentage equals:

(Grain weight after threshing / Head weight before threshing) 100

5. Adjusted yield, 15% moisture basis, equals:

(100 - %H20 / 85) (GNWT) C

Where:

%H20 is moisture content of grain as measured by moisture

computer. GNWT is the grain weight after threshing. C is a

constant (1960.78) for converting plot area into hectares.

Statistical Analysis

All data were analyzed for statistical significance using

analysis of variance for a randomized complete block design. Duncan's

New Multiple Range Test and simple correlation of all variables were

conducted. Computational analyses were carried out by use of the

Statistical Analysis Systems (SAS) at the Texas Tech University

Computer Center.

15

Least Significant Difference (LSD) values (Steel and Torrie,

1960) were computed to compare means of a genotype for a trait between

PP + 1 and PP + 3 water levels.

CHAPTER IV

RESULTS AND DISCUSSION

Morphological Characteristics

Analyses of variance of individual plant data for preplant plus

one irrigation (PP + 1) indicated highly significant differences

existed among genotypes. The PP + 3 showed more genotypic variation

for all traits except number of leaves. The larger variances due to

replication by genotype interaction in PP + 1 indicate more plot to

plot variability existed in the PP + 1 (Table 1). All morphological

traits measured were highly significant (P = .01) except plant height,

being significant at P = .05 (Table 1). The preplant plus three

irrigation level (PP + 3 ) indicated significant differences existed

among genotypes for all characters at the 0.01 probability level

(Table 1). As indicated by Table 2, combined analyses over water

levels resulted in highly significant interactions between water level

and genotype, evidence that inbreds responded differently to the two

water levels. Highly significant differences (P = 0.01) for all

traits except number of leaves indicate PP + 1 gave a different

response than PP + 3 due to water levels applied. Highly significant

interactions of genotype with water level were observed for all traits

except number of leaves. The data contradict results obtained by

Vinall and Reed (1918) of reductions under water stress of from three

to six leaves, and more recent results reported by Bennett (1975) of

reduced leaf number with water stress.

16

17

i o >-l

oc (0 di p

• H r-i

TJ di U

,jQ P

• H

>4-l O

CO j - t • H CO V4 4-1

i H CO O

•H 0 0

o rH O X a ^ o a p o

CO 4-1 CO

T3

^ O

ires]

. /••>.

o (30 <y» 1—I

CO iH (U > di

rH

P o • H 4-1 (0 00

• H

u u

• H

^^ <^

+ Ot OH

" ^

0) di

thr

CO 3

i H CU

4-1

c CO r H

pre

p

CO CO

CO di

s •>^>

di

a c: CO

• H Wi CO >

>4-l

o CO

•H CO >.

rH CO

c <:

. .—1

di r H ^ CO

H

1—(

+ 04 04 N_^

0)

c o CO 3

i H Od

4-1 P CO

r H

a a) u cu u di

"p p 3

o H

U •H 4J

H 0) CO x : CO

4-1 0) C M > . < : CO o 4J

o

CO

r H S-l CO < J 4-1 O >4-l

H CO di

<4H O

CO U di di >

X CO a <u 3 HJ

rH O CO p di 3 VJ

A4

rH X a 4J C3 00 3 C

di X

4J 4-1 P X CO 00

rH ' H

o

3 o

C O

o

cx> ON -3-

cn

m

CO

CM 00 o r—i

•K •K O 00 r>* cn r^ m

•K •K , — ( CTi

vO 0 0 m CN

•ic

ON

00

00

* CM m o cy> m -* 00

CN

CD

CJN 00 00

CN

ON

CJN ON

m

00

•K

CJN

cn

•K CO

CN

•K •K vO

O cn cn

* CO

cn cn

•K

cn

cn r-i CN ON

•K •K

m

\£> C3N

m

o

o

<r CJN o CN

•K

m CN

m

o

CO O

a

PC

o

(U

a 4J o c <u o

•K

m f—t

m

•K •K

cn m m CO

•K vO

cn

•K •K CM

CN CO

•K HC

O

•K •K 0 0

cn

cn

CJN

o

i n

cn

cn ON o cn

00 o cn cn en

in m 00

CN 0 0 o

• < r cn

I — I

oo m

00

m

cn

en CN

cn cn

cn i n o 0 0

ON CJN

cn CN

m

cn cn CN

CO

00 00

i n r^

CJN CN

CN

cn CM

cn CM

rH m

CN

CN

cn oo m

•K •K 0 0 ON

cn cn cn

o m

CN

00

CN 00 CN

CJN

m

O

X

PC

X

PC

p CO

rH PL,

CO 4-1

o

di >

a di a CO di u

X CO

X o u a

14H

o

di > di

o

o

c CO

m o

CO

4J P CO O

P 00

• H CO

I

>

o 0) a CO di

cn

+ (Xi Oi

c CO

(X, &4

)H o

di 3

rH CO >

18

u di > o CO di p

di u

X p

o CO

CO

CO O

• H O O o

rH o

X a u o 8 P o

CO 4-) CO

T3

CO di U CO 3 O" CO

p CO di

a

di o c CO

• H

CO >

rH CO 4-1 o H

4-1 di

X (0 4J (U c u >^< CO o 4J o

X Oi

CO di

rH U CO < 4-1 O t4-(

H CO di X

U di

X

a 3 Z

CO <u > CO 0)

hJ

rH O CO

3 t i T3 <

04

di rH X O 4J C 00 3 C

<U J O)

P X CO 00

rH -H 04 (U

o 00 CJN

CO • H CO >%

rH CO

5

CM

0) rH .Q

CO H

CO rH

> (U

V4

4J CO 3

•K •K 00

o r >d-«o cn ON CM

•K

* ON r «* m ON 00 r CN

CJN CM CN vO l *s . m

r - ( r H

vO ON r m

* * vO 00 r-4

O r^ m CJN

•K •K en o sr r>» r m CJN

•K * r 00 >3-oo >^ <J-1—4

•K •K CJ\ cn CN 00 >cl-- * r-4

•K •K CJN o m r^ 00 - *

•k •K CJN o 00 as 00 >^

<—4 -^ m cn cn CM

r«* •<r 00 •-d-

cn CM

«^ 00 CN \0 ON i n

vO -<J-CN cn as i n

cn o

cn

•K

m CJN

o

•K •K cn cn m

vO CJN

o

CM

HC •K

CM m 00 00

00

• m

CN

CJN

CJN

•K •JC cn

• ON \0 rH CN

CN

•K •K CJN

• C N cn cn

CM

CO ^

00 o

O N m -3-

•K •a CN

. r-4

vO ON

CN .

>* m

* * vO

• O cn o

•K •K cn

. o \D CM

* •JC O

• P^ cn

cn •

cn ,—t

r—1

. r-4

m

* •K r H

. ^ CN i-H

«* cn

vO •

o CN

* •K 00

• CJN CN O r H

•K •K r

. sr o cn

00 •

'«£) VO

r .

m cn

r H

. >^ P^ r H

\ 0 CM

>a-•<f i n CN

CJN 1—1

cn

di o u 3 O cn

/ - N

s >» rH di > di

rH

U di 4J CO 3

s Pi >^ p o

•H 4J CO o

•H rH a di

PC

o

di a

o p di o

o o X

065

o X

PC

p CO

CO 4-1

o H

X CO

X O U a

*4H

o

>

o o

CO

c CO O

c 00

•H CO I

•K

19

Absence of variation for number of leaves within an inbred line

could be due to irrigation June 30. This irrigation was applied

during growth stage one (GSI), the period of growth between planting

and panicle initiation. Both treatments were under comparable

environmental conditions during GSI which is the period of leaf number

establishment. All inbreds were subject to the same macro-environment

until the second irrigation in the PP + 3 water level. After panicle

initiation leaves are no longer initiated and leaf cell expansion

would then be the major determinant of photosynthetic area. Leaf cell

expansion in response to additional irrigation water may have been a

major contributing factor to the highly significant differences in

total leaf area indicated between water levels (Table 2).

Dry Weights

Analyses of variance for dry weights in PP + 1 and PP + 3 provided

results similar to those obtained for morphological characters, with

highly significant genotypic differences for all traits (Table 3).

When analyzed over both irrigation levels, genotypic differences were

highly significant (P = .01) (Table 5). Water level by genotype

interaction was highly significant (P = .01) for leaf dry weight and

plant dry weight, and significant (P = .05) for head dry weight and

stalk dry weight (Table 4). This indicates water level had an effect

on dry weight causing the relative position of a inbred line to

change. Such genotype by water level interaction for traits measured

indicates certain inbreds perform better relative to the other inbreds

under higher or lower water levels. Therefore, inbred lines will

20

u di

T3

P 3

t O u 0 0

CO CU * P / - N

• H O rH 0 0

ON T J r-H 0) > - • IH

X CO C r H

• H di >

U di O H

>4H

p CO O 4-» - H J= i J 00 CO

• H 00 (U - H :2 V4

V4 >^ - H U

TJ / - ^

cn 4J

c + CO rH (X,

a. oi c O (U

(U CO }H

CO 4-1 T3

CO *4H 3 O r H

a

res)

ant

squa

repl

a 3 CO 'P di P a CO

/'^ <U ,-4

o p + CO

• H OH M OH CO ^-^ >

CU 14H C

o o CO CO

• H 3 CO r H >% CX

r H CO 4-1

<i CO r H

cn u a

ble

CO H

4J

x: 00

4J ^H C (U CO : 2

r H

0 >^ V4 Q

4-t J= 00

• H 14H CU CO S (U X >,

u a

4J X 0 0

i H di CO S 4-) CO >^

o

4J

00

CO <U <u :s

^4 Q

»4H

(U O

3 O

CO

O 0 0

r m 0 0 0 0 m ,-i

cn cn

cn cn O CM I—(

CN CJN

CN m

<—4

-»-- t - • • -

CN m

^ o r-4

en

/"-S

0(S

p o

• H 4J CO O

• H r H

(U Pi

* * 0 0

0 0

o cn <—4

•K •K

•

m r-H

•K

cn 0 0 i n

O

cn ON

r

o

CU

a > 4-1

o c (U

o

•K •K '^t

sO >;t

CM

•K •K cn

• CJN 0 0 CN

•R •K -3-

r>. i n 0 0

•K •K

m m

T—4

•K r-4

o ON CN

•K

• •<d-

•K

m •<f CJN

•K

cn

o r—4

r-4 CM

o X

PC

v£>

S t O cn

CJN

cn cn

0 0

i - H

ON

0 0

CN r H

0 0 CJN

r H 1-H m cn •-i CM

r cn

m cn CM CM

O r^

r^ 0 0 s r v£)

CJN o

c n 0 0

0 0 CN i-H

^fS^

o X

s-x

4-1

c: CO

r H OH

CN r H

O N O O

CM cn CN c n

s f ST

• • m \o cn cn

r^ vO

0 0 v ^

r-4

0 0 s r

0 0 m r H

ON

m ^H

r H CO 4J o

. >^

r H <U

> • H 4-1 O CU a CO di u

M

>% 4-1 • H r H T H

CO j Q . O >% U TH

evel of p

espective

I-H U

t—4 *

o cn o + •XJ OH

P OH CO

T3

0.05

1 an

^ + CO

OH •M OH

C CO U

o o <4H •rH 0) C 3 00 rH

•rH CO CO >

• 1

1 1

•K - ( -•K - t -

•K H -

21

o 0 0 ON

CO rH di > di

u di 4-1 CO

U di >

o CO 4J X 00

•H di

u 'p

p CO

u o

CO 4-1 CO

c o

CO CU u CO 3 o* CO

c CO (U

a 0) o c CO

• H V4 CO >

*4H O

CO • H CO >%

rH CO P

<

(U rH X

CO H

X 00

•H 0 13 4J

3 CO

* * 00

• CN O cn r H r H

St •

vO 00 cn

•K -K CN

• m o r>» CM

* * o

• o m o r H

•a cn

• r CJN CM

00 .

r-4 ON rH

CM •

00 ,—1 cn

X 00

•H 0)

3

CO <U

X 00

• H (U

rH CO 4-1 C O

•K •K 00

. t n

cn

cn

* •K CJN

• CN o cn

•K •K O

• cn S t

•K cn CJN

cn

m

S t CN

(JN

cn

•K •K r>>.

. rH i n CJN

o • <JN

o <-4

•K •K 0 0

. rH vO r-4

•K CJN

. 0 0 r>» c

•K I-H

. cn CJN

CTN

. r i n

m .

00 CJN

X 00

•H (U :s TJ CO di X

* •K 1—4

• o o 0 0

00

•K •K vO

• vO CN CM

•K CJN

. 1-4

cn

•K •K m

. 1—4 1-4

CJN •

i n

m .

»d-1—4

v£> CN S t m

CN

ON 1—4

cn

di o u 3 O

CO

di > di

u d) 4J CO 3

Pi

p o

CO

CU

oi

o

(U a >% 4-1 o p di o

o X

: 2

X

O

X

OJ

4-1

CO

CO u O H

di >

O lU a CO 0) VH

CO X o u CU

di > di

o «

o c CO

m o

4J CO

C CO

a

p 00

•H CO

I

•K

22

" O CO (U rH U di

X > c <u

u p o o

»4H " H 4 - 1

CO CO 4 - 1 0 0 • H - H

CO U

u u TJ / ^ ojcn

>H OH

OH

-O ^

§ <U (U

r H X 0) -1-1

• H >N CO

3 C r H

• H O . CO

0 0 c CO

r H (U a . ^j

p ^

o + ^-N

CO CU u CO 3 o* CO

OH OH N ^

(U c o CO 3

ian

ce

CO >

MH O

CO •H CO >>

rH CO P

<

•

epla

r

M

M (U

TJ C 3

C ^ o >H 00 .

/»-> CO o (U 0 0 c: CJN

i n "H r H rH v - /

(U

r H

CO

H

00 0) C 00

• H CO J = 4-) CO c di di u o X u

OH

TJ di T j 4J rH CO (U 3 • H

• f - ) >4

<!

0) (U 0 0 M CO 3 4J 4-1 P CO 0)

• H O O »H S <u

OH

00 • H

U di o :2

r H OH P

CO

X 0 0

4-t - H O di

rH :s O H

T J CO 0)

(U O u 3 O

CO

0 0 CM

CN CM

•K •K 0 0

• 0 0 CN

•K

O CM

O St cn ON

o CM 1—4

•K

m en o CM

•K •K <N S t 1—4

CN m cn

cn cn

m CN St

m en

m cn m o

• K •JC ON CJN

so m m

. cn

ON 0 0 >3-CN vO 1-4

vO CJN S t O m

CN CJN 0 0 o CJN

cn

O CM m ON S t cn

NO

St

CM

cn

VO CM

o

sO r-4 O

o

•K •K vO ON CN

>ct CSI cn

i n CJN 0 0

rH O

CN « * S t f - ( O O

ON

o CN r-4

.

o

cn

•K S t CN 0 0

•K •k N O St m

CJN O

S t 0 0 O

PC

c o

CO

cx di

PC

o CN

CJN St O

o CM

S t O N

cn

CN

O

CU P.

4J o c CU

o

O X Pi

cn

CO 4 -1 o H

• >» u •H r-i •H X CO

-Q O u p.

MH

O

rH <u > <u r-i

r-4

o •

o 4J CO •

4J P CO a

•H l+H •H C 00

> •H 4-1

a (U a CO <u u «\

cn + OH OH

TJ P CO

r-4

+ OH OH

U O

14H

di 3

rH CO >

CO

•K •K

23

need to be evaluated to determine such responses to water. Depending

upon correlations between related traits and grain yield, particular

inbreds may be better suited to certain water levels. Of special

interest are those types capable of maintaining performance at lower

water levels as well as having the capability to respond to greater

water availability.

Grain Yield and Related Traits

Analyses of grain yield and related traits for PP + 1 and PP + 3

indicated highly significant differences (P = .01) existed among

inbreds (Table 5) indicating genetic variation existed among inbred

lines for grain yield. When analyzed over water levels, highly

significant genotypic differences were observed with all traits as

indicated by Table 6, providing evidence of genotypic variation for

all traits. Genotype by water level interaction indicated a

significant (P = .05) difference. However, plot head weight, plot

grain weight and adjusted yield indicated no such interaction.

Interpretation of this lack of interaction is that the relative

position of an inbred line did not change over the two water levels,

and a change in unthreshed head weight at harvest did not affect grain

yield relative to other inbreds.

Significant genotype and genotype by water level differences for

most morphological traits and all dry weights is evidence of

differential response to water availability among inbreds. However,

significant genotypic differences for adjusted yield, but no genotype

by water level interaction, indicates that additional water was used

for vegetative growth, not reproductive growth. Such a response was

24

o 0 0 CJN

CO rH di > di

u di

4-1 CO

u di > o CO 4J

o rH

a 13 rH di

o 14H

CO 4-> CO

p O

CO

di

CO 3 cr CO

P CO CU

a (U o c CO

• H >H CO >

o CO

• H CO

>, r H

CO P

<

X

di r-i X

CO H

00 <u C 00

•H CO X . u

CO c (U di U (J X u H <U

OH

T3 <U T3 AJ r H CO (U 3 "H

•O >H TJ <

di u 3 4J CO

• H O

s

00 CO 4-1

p di a >H di

O)

x: 00

• H 4 H CD O S

r H OH C

• H CO U O

x: 00

4-1 • H O (U

- H S OH

CO <U

di o U 3 O

CO

1—4

• rH - * CJN

CN •

m CM

•K -K m

• o o Csl

- * •

0 0 S t

CJN •

CM CM

CM •

vO r

•K •K

m CN r-4

cn o 0 0 0 0

o m cn r r

•K * 0 0 CN O vO

cn cn CN

CJN 0 0 vO CJN r H CN

CM CJN S t <JN

o I - H

CM vO O >* o m

•K •K O O CJN

• vO S t

S t 1—4

vO •

O

•IC •K ON

o 0 0 .

vO

•)C •K

r <* m . r-4

0 0 CJN CN

. o

o cn ON

. r-H

•K •K

-^ cn o

i - H

CM O

•K •K

m vO

m m m o

0 0 CN o

CM CN r-4

CN

•K •K O 0 0 CM

• S t CM

0 0

o I - H

. o

•K •K

>* r>» r-4

. CN

•K m (JN r-4

. o

CJN

r O

• o

CM r-4

r>. .

o

1-4 v O

: 2 PC

CN cn

di > di

u di 4J CO

p o

• H 4-1 CO O

di Pi

o

CU

a 4J o p di o

o X

o X

0:2

CO 4-1 o H

(U >

o (U a, CO (U

•IH

CO X o u a

di > di

o o -p

p CO

m o

CO

p CO O

P 00

• H CO

•K

25

observed when averaged over all inbreds, but may not accurately

describe individual response.

In a breeding program, inbred lines would be evaluated on ability

to produce high grain yields over a range of environments or developed

to be grown in a particular environment. Those inbred lines with the

ability to produce a high grain yield in relation to vegetative matter

when water is limiting would be selected. Lines able to partition

development in this way may indicate other factors such as

photosynthetic rate, root depth and density, or early maturity are

influencing grain yield in addition to leaf area and related traits.

Other influences could be the time at which the plant begins producing

photosynthate for grain fill and also the amount of photosynthate

stored before grain fill begins. These elements need to be evaluated

to determine their effect on the grain fill period and final grain

yield.

Morphological Trait Means

Means of plant heights for PP + 1 were generally lower than means

for PP + 3 (Table 7). Most inbred lines were reduced in height by 20

cm or more, but TX 7078 and NSA 440 indicated reductions of 12 cm and

13 cm, respectively. TX 7078 was the shortest in both water levels

and was significantly different (P = .05) from all other lines over

water levels (Table 7). NSA 440 was not significantly different from

the tallest line in PP + 1 and was third shortest in PP + 3 (Table 7).

Although TX 7078 and NSA 440 showed the least change in height between

water levels, both inbreds were significantly different at P = .05 by

LSD test (Table 7). Using the LSD value of Table 7 to compare each

26

c: CO

O4 OH

(U P O

CO 3

p CO

rH a CU u ex

;H

(U T1 3 3 ^ F 0 u 00

CO (U

c •H i H

-o (U u X p

•H

0 00 CJN I - H > « •

CO r-i di > (U

rH

u di 4 J

CO 5 u di > 0

TJ P CO

CO rH CU > di

^

CO 4-1

•H CO M •u

rH CO 0

•H 00 0

H 0

X ex >H

0

a 14H 0

CO p CO (U S

. r*

di rH X CO H

CO 00

•H SH M

•H

/ ^ S

cn

+ OH OH

• ^ ^

(U (U u X 4-t

CO 3

rH CX

4H

rJ CO

r-i CX (U >H

CX

0 4 J

0 X OH

rH CO 4-1

0 H

UCN •H / -> 4J a di 0

X ^ u P CO >^ di CO u

<

<4H CO

a) /~\ i J COCN (u a rH M O CO < - ^ 4-t

o H

u di

X

a 3 z

14H 0

CO (U > CO di X

di r-i / - ^ CJ COcN P di B 3 M U

TJ < >-' (U

OH

(U H X O 4-1 •-N 3 00 a 3 c a

TJ CU >-» <u J

OH

CO 00 a rH •H O OH <U >-'

0) CX >% 4-t o p di o

T3 0

^ X

vO 0

1954.

2819.

•p 0

X 0

CN <JN

1939.

2782

(U T J CU

m CJN

00 00

0 . 0 X

S t r H

i n X rM cn

0 X 0

ON r H

i n r-l I-H

di 'p

00

vO 00 cn CM

TJ 0

0

r H vO cn CN

(U

r>

00

X

00

m CM

0 X

i n

00

- 1 -•K 4 -0 - t -

XJ U3rH CO CO ^

cn CM

CJN i n 1 - . 0

r^

TX 7000

CM

CN CJN

•p 0

CJN cn

ON r^ m I-H m CJN r-i r-4

T3 TJ

0 0 r H

S t r H « * i n m ON r-4 r-4

di di

CM m

00 00

X TJ

C N CM

m 0 r H CN

U X 'P

ON so

m vo

u -0 r H r-4

m r r^ 00

00

0 r

X H

14H

X

m NO

r-4

<4H

CJN

r-4

di

en

00

U X

r

r H

0

CM

NO

(U

r-4

r-4

00

CO

NO

CM

vO CN

CO

vO

NO NO sO CN

, 0 CO

CJN

0 r-4

X

CJN

m

' p 0

CJN

r-4

X CO

f^

r-4 00

CO

CM

cn 0 m cn

CO

CN

r-4

i n cn

0 X

NO

0 r-4

di

0

CN

<U

NO

0

CJ

i n

ON

0 • ^ • ^

< : CO

z

CO

CJN

00 0 cn

CO

<JN

cn 00 0 cn

0 X

00

0 r H

TJ

0

«*

T3

Csl

r-4

13 0

r-4

00 00

abc

-d-

00 m CM CN

0 X CO

r

m CM CM

1 3 CJ

i n

CJN

X

r

en

1 3 0

CJN

r H

0

CO

as

00

CO

- *

00 cn I-H

cn

0 X

CO

0

00 CJN

cn

13

0

0 1—4

X

- *

0

X

>*

sO r-4

X

sO

cn 0 r-4

r-4 1

sO

i n

u CO

a X

-^

00 CJN vO CN

a X

^

sO

vO CM

13

00

CJN

X

0

CN CM

X

r-i

CJN

0 ^

CN

r-4 CJN

CO

0

m <JN

cn CN

CO

cn

m cn Csl

CO

0

CM r-i

CO

r>»

cn

CO

00

CN

CO

Csl

m 00

X CO

00

O N

cn

0 X

CN

ON

0 cn

CO

CM

CM r-4

CO

SO

0 r

CO

r

0 CM

CO

cn

0 1—4

1-4

1—4

1 i n cn 0 CO

X CO

- *

CM

CN

X

CN

00

r-4

CN

CO

1-4

CN r H

CO

CM

-3-m

CO

00

sO 1—4

CO

r>

CJN

'P 0

cn

0

r-4

13 0

r>.

i n

I-H

X CO

-^

r-4 r-4

X

vO

m r-4

X

00

r*.

X CO

ON

CN 00

>4H

u <u

CM Csl

00 CM 00 00 r-4 r-4

(4H 13 di

sO r H

i n m i n 0 00 00 r-4 ,-4

X X

cn cn

r H r-4 r-4 r-4

•P a X

sO r-i

00 CN CN CN

X X

m CM

« * r-4 r-4 r-4

X X CO CO

0 0 c n

m St 0 CJN — 4

00 00 r-4 CJN

PC

27

• • •

13 01 3 3

• H 4-1 P O o

. r-.

di rH

X CO

H

1 O CJCN 4J - H / - N

o u a X CU u O H j C s - ^

4-t r H C CO CO > , CU 4J CO VH

o <: H

(4H CO di ^•^

X COCN

(u a r H V U CO < ; v w 4J

o H

CO U di <u >

. O 14H CO a o <u 3 HJ

Z

CU r H ' ^ CJ COCM 3 CU a 3 (H U

"^ <3 ^-^ <U

OH

(U r H X O 4J ^-N 3 00 a 3 C O

1 3 CU ^ 1 ^

di X OH

• U 4.) 3 ^ ^ N CO 00 a

r-i -H O OH at >-^

ffi

0) CX >s U

o p di

o

TJ U

^ CO U

•^ so m . . .

-d- CM cn r-4 r-4 r-4 r-4 r-4 r-4 CN CN CN

O X di CO 1 3 13

CN ON o . . .

cn CN cn rH CJN O r H O r H CM CM CM

O T3 13 ^ O CJ

- ^ CJN r H

. . . O CJN O r H r-i

-P - Q U O

CN r^ m . . .

r H CJN O r H r-4

1 3 1 3 13

c n s O r H

. . . o m cn

CJ XJ O 13

ON r H m . . .

sO sO sO r^ ON 0 0

r- cn r>. CM

X H

U X X

CO CO cO

m o CN . . .

m ON CN r-i O r-4 cn cn 00 CM c n CN

a XXX

CO CO CO

cn p^ o . . .

P^ 0 0 - * o o o cn cn 00 CN c n CN

X ^ X CO CO CO

cn m -^ . . .

r-4 r-4 r-4 r-4 1—4 r-4

X d) Ti

CN c n CM . . .

0 0 CO 0 0

1 3 U di

X "P "P

O cn CN . . .

cn cn cn

o X o CO U3 4 2

>^ o r>. . . .

ON CN O r^ O CJN

I - H

-17

vO < 1

o r^ r ^

<J> CO

cn •

o <JN SO

Csl •

CM as sO

1.4

0 0 •

- * r-4

CN •

m

m •

0 0

•M i n

o •

o Q CO X

1 u di

>4H <4H • H 13

> N

rH u

iflcan

c 00

• H CO

4-t O 3

ter are

4J CU

r-i

same

by the i

t.

y^ di 5 ^ O di

J C>0

o S

column f

Itiple R,

3 <U jg a " CO 3 CO Q)

Z di

ent in th

Duncan's

a >N 4-> X CO d) M

u i n 4-t O

• CO

II u O OH

14H U

CO CO

c CO 4-1 <U P a <u 1

•K

, 4 J

f H • CO

>>> U rH -U CU

spectiv(

s for a

CU rH

vels, r

er leve

water le

ween wat

4-1 >H 0) di X > O d) CX

1 3 >^ 3 4J

P + 3, a

f a geno

OH O

M CO rH 3

CO

+ <u a

ue for PP

omparing i

rH O CO > Ul

o CO M H

0) 4-1 (U O 3 C rH (U CO

1 3 >

1 1

•-H CN

A

-«— +-

M

+-

28

inbred's value for height in PP + 1 with its value in PP + 3 indicates

no inbred maintained the same height under varying water regimes.

This gives evidence of significant increased vegetative growth with

increased water availability for all genotypes tested.

A positive association of plant height with adjusted yield (Table

12) indicates selecting for plant height would have a positive effect

2 on grain yield. However, this correlation resulted in a r value of

0.09, indicating the relationship was of no great biological value.

Tendency of tall plants to lodge as well as the difficulty encountered

in combine harvesting of tall plants would likely inhibit selection

based on this character. Selection of an inbred with stability for

height over a range of environments could lead to efficient light

utilization referred to by Graham and Lessman (1966).

Peduncle length means were related to plant height means (Table

9), taller plants having the longer peduncles as a result of internode

expansion. Change in peduncle extrusion length was most dramatic for

SC 56-14, being 1.9 cm in PP + 1 and 16.4 cm in PP + 3 (Table 7).

These values are shown to be significantly different by LSD test.

Lines TX 7078, NSA 440, and SC 170-6-17 had relatively small changes

from PP + 1 to PP + 3 with SC 170-6-17 being essentially constant, and

values for these lines are not significantly different when tested

with the LSD value. Decrease in peduncle extrusion length under water

stress is in agreement with results obtained by Bennett (1975).

Stability of peduncle extrusion length over various environments would

be a selection criteria from the standpoint of ease of combine

harvest.

29

Degree of peduncle extrusion beyond the flag leaf sheath is the

result of expansion of the uppermost internode. Highly significant (P

= .01) positive correlations between plant height and peduncle length

at both water levels (Table 9) indicates for these inbred lines

overall internode expansion is related to peduncle extrusion length.

Plants having more internode expansion would have a more open growth

pattern which could allow for greater light utilization.

Means for number of leaves in PP + 1 and PP + 3 indicated that the

taller plants (SC 35-14, R 9188, and SC 170-6-17) had the greater

number of leaves (Table 7). This can be explained by number of leaves

being directly related to internode number, and height of plant being

due to internode expansion. Lines maturing at about the same time,

but having differences in leaf numbers, would be expected to have

different rates of leaf appearance, the inbred line with more leaves

having the faster rate of leaf appearance. Since peduncle length is

related to plant height, genotypes with more leaves would be expected

to have longer peduncles due to the relationship of height and

internode expansion. This was generally the case except for peduncle

length of SC 170-6-17 which was essentially the same for both water

levels. This could be due to leaf sheath length; however, no data is

available for this trait.

Height decreased from PP + 3 to PP + 1 for all inbred lines (LSD

significant) up to 25 cm for SC 35-14, but no corresponding decrease

in leaf numbers was observed for these inbreds (Table 7). This

contradicts results obtained by Vinall and Reed (1918) of reductions

of from three to six leaves in sorghum under water stress, and by

30

Bennett (1975) who reported a decrease in height and leaf number. The

lack of variation in leaf number could be due to June 30 irrigation

near panicle initiation. Variation in height leads to the conclusion

that internodes were expanding at different rates, but no variation in

leaf number indicates the same stress for both water levels while

leaves were initiated.

Means for leaf area and total photosynthetic area gave results

similar to those obtained for all other morphological traits in the PP

+ 1 and PP + 3, being greater in PP + 3 than PP + 1 except for TX 2737

(LSD not significant) which produced essentially the same leaf area

under both water levels. Leaf area reductions ranged from 6% for R

9188 to 30% for TX 7000 and SC 170-6-17. TX 2737 was observed to be

early maturing and senescent which is evidence of drought escape

mechanisms referred to by Keim and Kronstad (1981). Early maturity

could lead to increased cell expansion rates in the PP + 1, and thus

increased photosynthetic area.

The significant genotype by water level interaction for total

leaf area, but no significant difference for leaf number (Table 2),

indicates leaf expansion was the primary factor causing increased

photosynthetic area in PP + 3. The significant negative correlation

for total leaf area and adjusted yield (Table 11) gives a r^ value of

0.151 indicating increased photosynthetic area increased sink size and

was possibly competing with the grain filling process for photosyn­

thate. This can be seen from means for total leaf area of SC 56-14

and NSA 440 (Table 7) and adjusted yield (Table 8) of these two

inbreds. Although leaf areas for these lines were largest in PP +3

31

CO 3

rH CX

4J . 3 ^ CO O

rH 0 0 O.CJN di r-4 U ^w'

a CO

U r-H CU di

-o > 3 <U 3 ^

r ' ^ ^ d^

}H 2 00 ^

rn '-I

3 > •rH

_ 3 1 3 CO (U >H M

•2 •-' 3 a; • H >

0) U r-i O

<4H 3

o - r t T H

r H -W flj CO

• H M > ^ • H

U

^ H • H ^ CO U ^ bO^

^ + 4-t

^5 13 di 3 CU CO M

J= CO 4-t 4-t X CO 0 0 3

•H r-i di CX 5

4-t

>N 2 tH «J

TJ rH CX

4_, 0)

3 ^ g CX

^'B CO

14H

o ^ r H

CO

c + CO

i i OH S OH

<>-•

. (U

0 0 3 O

di r-i X CO

H

0 0 3

• H J 3 CO di u X H

0) U 3 4-1 CO

• H O

s

1 3 0) 4-t CO 3

di 00 CO 4J 3 ^-> <U ^ 8 U > ^ U di

OH

0) 0 0 CO 4-> 3 /-^ Oi ^ S O > ^ M CU

OH

CO ^"^

X o CN

00 X M ^ >«• m

•«-) T3 r H 1 3 <

3 • H CO Ui O

4-t

o rH OH

TS CO di ffi

4J

o r-i OH

4-1 3 CO

rH OH

14H CO 0) X

^ i H CO 4-t CO

1 3 CO di X

rH di 4-t

• H CO >•

4-t X ^-s 00 0 0

• H ^ (U s ^

3

4-t X / - s oo 00 •H M 0) s ^ 3

4J X / - s 00 a

•H 00 CU v - /

S

4-t X '^ 00 a

•H 00 01 >^ :s

4-1 X ^-N 00 a

• H 00 (U ^ ^

:5

4-t X ^ 00 a

• H 00 di v ^ 3

0> CX >s XJ O 3 di O

a ^ CO

so o vO

cn

di 1 3

m cn

cn

CO

CJN ON CJN I - H

CO

O O

r-4

CO

CJN r^

r-4

O

cn S t

r^ cn

T3 U

sO m

en r-4

CJ ^

sO cn

0 0 r H

- ( -•K . O

r H

m •

i n

X

0 0 CN

so cn

T3 O

m rH

CN

X CO

o i n

cn CM

X CO

sO 1—4

1—4

CO

ON 1—4

cn

X CO

cn so

cn so

CO

r m cn CM

a X

o so 0 0 CN

1 3 U

r- r-4

sO

cn

a; 13

m t ^

CN

CO

>* r^ r-4 CM

CO

0 0 O

r-4

CO

CJN - *

CN

o X

CN

m o m

o X

sO i n

0 0 r-4

X

0 0 S t

cn CM

- t - r H

+-X

sO S t

•

TX 7000 11

u X

0 0 ' ^

• 0 0

CO

0 0

o CM vO

di

0 0 0 0

CM

X CO

sO CJN

m r-i

X CO

ON

r O

o X CO

0 0 CM

I - H

o o m m cn

T3

CN cn

CN r-4

o i n cn

m r H

CO

cn 0 0

r^

CO

m cn 0 0 S t

'p

cn r-4

CN

CO

1-4

0 0 vO CN

CO

CM cn

r-4

X CO

cn t*>.

CN

1 3

i n

o 0 0 - *

X

m o p^ r-4

1 3

ON O

o CM

X

1—4

CJN

o

TX 7078

1

CO

r-4 CM

m m

o o m CM

CO

0 0 cn r-4 CN

CO

sO O

r-i

X

r-4

o CM

1 3

0 0 P ^

r-4 •^

13

CJN sO

S t r H

u CM r^

t ^ r-4

X

r^ cn

<3N

'P a

CN r-4

0 0 S t

u X

0 0 r>.

be

14.

CO

sO 0 0 cn r-4

X CO

O r^

O

CJ X CO

r>. S t

.—I

CO

0 0 r-

CJN

m

CO

CM r^

CJN r-i

CO

r^ O

r-4 cn

CO

as CJN

0 0

X

0 0 CM

so cn

13 o

m 1—4

Csl

a CM 0 0 so r-4

o cn 0 0

o

CJ

CJN CN

CM

CO

m sO

m p^

CO

r-4 S t

S t CM

CO

r-4 1—4

r^ cn

CO

cn r-4

<T

NSA 440

1

1 3

O CN

CM S t

O X

X S t

cn

X

<f cn m 1-4

X

p^ p»*

o

o X

0 0 0 0

r-4

CO

r-l r^

r* vO

CO

so O

Csl CM

CO

CJN O

S t cn

CO

sO i n

r H 1—4

13

m -^

so «*

X CO

0 0 CM

i n

13

S t CN

cn

u r>. r-4

O

13

so cn o

X CO

ON

o eg

m

X CO

m p^

0 0 r-4

CO

-^ CM

ON Csl

X

o r-4

<t

X

CJN 0 0

CJN cn

X

m r^

CN

T3

r-4 CM

o r-4

13

1—4

m o

13

0 0 CM

1-4

X CO

(JN cn

cn vO

CO

CN

m rH CN

X CO

CJN S t

-^ cn

13

o 0 0 cn

p»«

SC 56-14

13 a

r r H

cn <*

X

r-4

o S t

O

CN r~«. vO

o -* cn o

13

c^ 0 0

o

X

m p ^

p^

m

X CO

-d-1—4

o CM

CO

1 ^ 0 0

r-4

en

1 3

S t f ^

m

1 3 CJ

CJN sO

p^ S t

CO

o o so

13 CJ

cn o ON

X

r^ >3-

O

a p>. ON

o

X CO

CN vO

r-4

m

X CO

cn i n

CJN r H

CO

sO r^

r^ CM

X

cn cn

'^

X

sO r-4

m en

CO

i n CJN

- *

a r-O sO 1—4

U

Csl 0 0

o

o cn cn

CN

o X

cn CJN

o vO

CO

CM CJN

O CN

X CO

sO > t

cn en

13

m m sO

SC 35-14

T3

CM •<t

r-4 <f

CO

0 0 •^

m

X

i n

m CM r H

X

•<r sO

o

u i n sO

r-4

X

CJN CN

sO

m

X CO

CM CN

o CM

CO

1—4

SO

O cn

13

vO -d"

m

13 CJ

X

oo 0 0

CJN 'd -

X CO

cn en

i n

o X

r-4 CM O r-i

X

CvJ

m o

CJ

X

S t

o r H

u X

CN r H

SO •^

O .o sO P^

S t i -H

CO

cn o r^ CN

X

en cn

S t

CO

r^ sO

vO

-a-

1 3 O

^

O cn

eg

X

CJN r-4 r-4 CN

^

m o r-4

o i n CN

CN

T3

cn o S t -3-

X

o p^

m I - H

13 O

-^ CJN

Csl CN

13

ON cn

i n

R 9188

CJ X CO

0 0 Csl

0 0 - *

X

r-4 0 0

cn

X

o p^ i n f—i

X

CJN r^

O

u >3-so

r-4

1 3 U

r< O

i n S t

'P

CN Csl

i n r-4

X

CJN CJN

- * CM

13

SO OO

• > *

32

• • •

13 di 3 3

• H 4-t

3 O

CJ

. 0 0

di r-i X CO

H

00 di p 00

• H CO X U CO 3 / ^ 0) 0) 3sS (H U N.^

J 3 U

H 0) OH

di di 00 ^ CO 3 -i-t 4-t 3 ^-s CO (U 8 «

• H CJ s - / O (H

S (U OH

CO / " ^ 1 3 JS O CU - ^ eg 4J 00 JC CO ^ S^ 3 's^^ i n

•"-J 1 3 r H 'P rH - < 0) 4J

• H CO

3 • H CO 4H M J= / - N

O 00 00 •H J«i

4-1 0 ) s.-^

o s r H OH

13 CO H

pd 00 00 • H ^

o s r H OH

4H 4-1 3 - C / - N CO 0 0 a

r H • H 0 0 OH 0) v .^

13

4-1 14H ^ x -s

CO 00 a 0) -H 00

hJ <U > - / : 2

. 1 ^ 4-1 r-i X ^-\ CO 00 a 4J - H 00 CO 0) > ^

: 2

4J 13 J= /-s CO 00 a (U •H 00

PC QJ >w' 3

0) CI. >. 4-1 o 3 0)

o

1 3 O 1 3

X X U

CM CjN r H m <* m

. . . o o m m S t S t

1 3 13 o -o CJ ^ o

o in cn o >a" CM

. . . •>* CM c n r H r-l r H

a X CO CO CO

P*. ON 0 0 r H cn P>. i n so o r H CM CM

X CO CO CO

SO r H S t (^ cn o

. . . O t—1 I-H

X CO CO CO

rH - ^ f ^ m CM cn

. . . r H r n CM

^ 1 3 O CO O XJ

r H P^ ON r H sO c n

. . . CN O r H i n m m

o X 1 3 CO ^ U

CM so - ^ St so m

. . . r>. in so r-4 r-4 r-4

13 O X

r^ 00 r>« cn r^ O

• • • i n >d- m CM eg CN

^ X X

CM c n 0 0 c n CN p^

. . . ON O CJN

r-4

ps*

cn r^ eg

X ! H

X X CO CO CO

CM 0 0 O r H sO ON

. . . 0 0 P^ CM St -^ m

0) O 13 'P X o

O cn r-4 p^ r^ CN

. . . cn CN cn r-4 r-4 r-4

X CO CO CO

ON r H O cn CN cn 0 0 S t r H rH CN CN

X CO CO CO

CM O sO ON CM O

. . • ^ r-4 1—4

o Cd X X

00 cn so m m o

. . . r H eg CN

O X X Cd X

0 0 c n r H s o I-H -a-

. . . vO O 0 0 S t p^ m

o X X CO CO CO

ON CN sO O so 0 0

. . . 1 ^ -d- O .-H CM eg

X CO CO CO

so ON r>. r H c n CN

. . . S t ^ O eg cn cn

a X X o

c n CN 0 0 >3" r H CN

. . . m ON p^

r-4

1 sO 1

o

r-4 CJ CO

S t 0 0

. sO

0 0 r>.

. o

0 0 CN < •

>^ CM

• O

o S3-

•

O

0 0 r^

. CJN r-i

P^ o

. p^

so 0 0

• o 1—4

P^ ^

• m

rM i n o

• o

CO X

1 <4H • H 13

>> rH 4J 3 CO

o • H ^ • H 3 00

• H CO

4J o 3

ter

are

4J di

rH

di

a CO CO

CU

X 4J

>^

— ui y, CO ^ di

r-i (D

1 3 ^ Cd

PC 4-1 ^ 3 (u ^ - H a CU

reat

Lilti

^ s <U 5 a CU CO <z CO

CO

the

can'

3 3 • H 3

a 3 a > 3 X

rH o m o o

• CO

It 3

• H OH X 4J 4J • H CO

4J CO 3 3 <U CO V4 di di

a ^ 1

•K

• 4J

ively.

a tral

4-1 U o o di 14H a CO CO 0) i H )H (U

>

CO i H r H

leve!

ater

3

(U 3 4-t (U cn OJ

over Wi

B betW(

CX 13 >% 3 4-t CO O

c M dl

cn 00

+ CO

OH ^ OiH O

« CO r-l 3

CO + <u a OH OH 00

3 ^ H O M

>4H CO CX

<u a 3 O

rH O CO > M

o CO StH 01 4-t 01 O 3 3 rH O; CO

13 >

1 1

1-* eg

«% - f -- t -

A

-»-

33

adjusted yields gave low values with SC 56-14 being the poorest

performing line.

Results obtained for SC 56-14 and NSA 440 are in contrast to

those of TX 2737 which did not have a total photosynthetic area that

differed by LSD from PP + 1 to PP + 3 (Table 7). However, TX 2737 did

have a significant increase in adjusted yield (Table 8) from PP + 1 to

PP + 3. A further observation of the results of Tables 7 and 8

indicates TX 2737 had one of the smallest total leaf areas, but one of

the largest adjusted yields in the PP + 1. This is evidence TX 2737

used the available water in PP + 1 for reproductive growth.

A stable photosynthetic area, such as produced by TX 2737, could

be a selection criteria for a semiarid environment where rainfall is

unpredictable. When water was sufficient, excess leaf area would not

be added, and when water was limited, there would not be excess leaf

area in relation to sink strength.

Dry Weight Means

Means of dry weights generally decreased from PP + 3 to PP + 1 for

all traits (Table 8). Reductions in head dry weight ranged from 10%

(TX 2737) to 53% (TX 7000). Compared over water levels, head dry

weight means separated into two groups with SC 56-14 having the

smallest. Stalk dry matter was reduced from 15% (SC 56-14) to 36% (TX

7000). This is in agreement with results obtained for corn by Boyer

(1976) of 21% reduction. However, results obtained for lines R 9188

and TX 2737 are in disagreement, having increases in PP + 1 of 18% and

2%, respectively. R 9188 may be acting as a perennial by increasing

vegetative growth at the expense of reproductive growth. An inbred

34

line having this characteristic would not be desirable for grain

production if water was limited due to undesirable genotype-

environment interaction.

Inbred lines TX 7000 and SC 170-6-17 had wide variation for stalk

dry weight from PP + 3 to PP + 1; however, a large variation for

adjusted yield relative to other inbreds was not observed (Table 8).

This may be evidence of stalk stored assimilates being translocated to

fill the grain which would allow for adjustment of grain yield in

various environments. Stability over environments could be used in

selection, inbred lines such as TX 7000 and SC 170-6-17 should have a

higher relative grain yield performance in a water limited

environment. Although TX 7078 and TX 2737 were not significantly

different (P = .05) from TX 7000 and SC 170-6-17 (Table 8), there was

wide variation in grain yield between environments (Table 8).

Means of Grain Yield and Related Traits

The values for adjusted yield seem quite low for most inbred

lines in either water level (Table 8). Means for threshing percentage

are also lower than generally expected. Experimental error in

threshing the grain could be the cause of these low values; however,

the thresher was tested prior to threshing the plots.

In both PP + 1 and PP + 3 and over water levels, SC 56-14 had the

least plot head weight and adjusted yield (Table 8). Stalk dry weight

of SC 56-14 was not significantly different from the heaviest at

either water level (Table 8). This would point to assimilates being

in the stalk with potential use for grain fill as reported by Boyer

(1976) and Wardlaw (1967). NSA 440 and TX 2737 had large stalk dry

35

weights in PP + 1 and large grain yields (Table 8) indicating this

mechanism. Low grain yield of SC 56-14 could be explained in part

from it being a nonsenescent type maintaining a large photosynthetic

area at the expense of grain yield. Similar to R 9188, SC 56-14 could

be trying to function like a perennial.

Inbred lines with the largest grain yield over water levels

generally had the lowest moisture percentage and highest threshing

percentage (Table 8). Lines SC 56-14, SC 35-14, and NSA 440 had low

grain yields, high moisture percentages and low threshing percentages,

evidence these were late maturing lines. Under conditions where water

is limited, this late maturing characteristic would be a disadvantage.

The available water would probably be used for vegetative growth or

maintenance while the reproductive system was idle waiting for

adequate moisture for grain fill.

Correlations Between Morphological Traits,

Dry Weights, and Grain Yield

Correlation coefficients were calculated to determine if

meaningful relationships existed among the various morphological

traits, dry weights, and grain yield and related traits. Due to the

possibility that trends may be different with varying water level, the

correlations were calculated for PP + 1, PP + 3 and over water levels.

All data was reported as r-values for simple correlation coefficients.

Plant height had significant positive correlations in PP + 1, pp

+ 3, and over water levels with all morphological traits and dry

weights except head weight and plant weight (Tables 9 & 10). Head

weight was negative and significant in PP + 3 and not significant in

36

1 CO CJ 4-t 0 0

X "H 00 ^

• H J-t d) i H

> N c n V4 13 +

3 ^ C O H CO o

«1 /»!

•H s CO ^

4-t ^

' - I 55 CO 5 o r: •H CX 00 0 *J

^ S O CO

-fi 'TJ a . Ci-^ 0) o >-• S CX

3 13 O 3

CO CO 4J /-N X r H 00 •H + 0) 5 d , . ( ^ > ^ s ^ M

" ^ (U

c -p o 3 CO 5 0

^ ^ ^ ^

gic

al

tra

pre

pla

nt

o ^ -H ^. o ^

^ 3 J H -^ O ^

s § 14H O

o ii 00 CO

c 'H o di •H C 4 J - H

CO ' - • r H di 1 3 M <U M U O X o c •H

. M ON O

(4H (U

r H .O CO H

. / -N O 00 ON r-l

< ^ CO

r H <U > 01

r-i

3 O

•H 4-1

4J • u i . £ P 00 CO'H

r H OJ O H : ?

4-t

<4H 00 CO'H (U o;

h J I S

4-1 ^ J = t H 0 0 C O - H 4 J di

co:3

4-1 1 3 J = CO 0 0 di-H

X di 13

1 o 4-t O O - H

X u i O H O; CO

X di r H 4-t J H

CO 3 < ; 4J >% O CO H

r H < 4 H CO CO CO 0 ) 4-1 OJ VH

Oi_J<5 H

u CO 0 ) CU

^ * 4 H > a o CO 3 OJ

Z H J

rH O CO 3 0) 3 JH

1 3 < : 0 )

O H

OJ rHX O 4J 3 00 3 3

n g OJ

OJ J O H

•K 1 •K -K C N C N r - H i n • > * r H 1

O O

« 1 •K -K <JNO C J N f ^ C g r H

O O

•K -K •K •)( c n < -moo S t C N

O O

•K •K

m m >3-CjN r H CN

o o 1

* -K •K -K c M m c N m ^ e g

O O

•X -K •K -K O N O O s t «3-CsJ

O O

•K -K •K * or-* O N m C M - ^

. . O O

•K -tc •K -K Q o m S t S t

>^m o o

+-- 1 - 4 -•K -te -K -K m m cnoo - ^ m

o o

4-1 4 - t x : 3 00 CO^H

r-i di

O H S

•K 1 * 1

S t r H 1 O O ! r-icn 1

o o 1 1 1 1

•K •K

s t m 1 r ^ v o O C N

o o 1 1 1

•K m r H o m O r H

o o 1 1

•JC - K * * 0 0 - s t s O O

cnso o o 1 1

•K O N c n

cnoo r-lr-4

O O 1 1

•K •K * SOON s O O r H C M

o o 1 1

•K r ^ O N p > . o r H C M

. . o o

•K -K •K -IC

1 CNCM 1 r -cn

CJNCJN

C 5 C 5

1 OJ 1 rH 1 c j j : 1 3 4 J 1 3 00 1 13 3 1 OJ OJ 1 O H H J

s O P > . 1 m s t 1 O r H 1

O O 1 1 1 1

cnr -C n r H 1

o ^ o o 1 1 1

O r H c n CN

o o o o

1

* -K •K -K C n r H r H m

c n ^ o o 1 1

r>.oo «*cn O O

o o 1 1

m m P ^ s O

o o o o 1 1

•K r H O CTNCN r H r H

• . O O

1 OJ 1 r-i

1 a 1 3 1 3 CO 1 13 o; 1 0) u 1 O H < :

•K -K 1 •K -K 1 r H v d - 1 C N O O 1 S t C M 1

O O 1

•K -K 1 •JC - K 1

cncn 1 O O O 1 S t C N

o o 1

•K •K •K -JC m r ^ O O O ^a-st

o o

•K cnm r H P ^ r H r H

O O 1 1

•K -K •JC - K ONi—t

cnso m ^

o o

•K -K •K -K cnr^ cnm m s t o o

1 I4H 1 O

1 U CO 1 OJ OJ 1 ijQ >

1 a n) 1 3 OJ 1 Z H J

•JC •JC 1 •JC •»( O O r H

p^-a- 1 p^oo

o o

•K * •JC * C N P ^ C M - ^ 1 f ^ O O

o o

•JC • K •JC - K cncn cncn 1 r^oo

o o

•K -K •K •JC cnm cnst cnst

o o

•K •K •K •K <JNC3N CJNCJN CJNCJN

O O

t '4H t CO 1 OJ 1 X

1 r-i 1 CO CO 1 4-t OJ

1 o u 1 H < :

•K -K 1 •K •JC 1 0 0 0 0 1 p^cn 1 P^OO 1

O O 1

•JC • * 1 •Jt -JC 1

C N s t 1 C N S t 1 r^oo 1

O O 1

•K * •K * m s t cncn 1 P ^ O O

o o

•JC •K •K -JC m e n 1 cNcn 1 c n s t

O O

oto-

c A

rea

1 X-H 1 CU 4J 1 OJ 1 HX 1 CO i J 1 4-t 3 1 O > , 1 H CO

•JC -IC 1 •JC •je 1

(JN^d-0 0 0 0 1 S t s O

o o 1

•JC •K 1 •K -K 1 - ^ c n 1 ONON 1 C N m 1

o o 1

•JC •JC 1 •JC - K CMi-l 1 OCJN c n s t 1

O O 1

4-t X

1 T3 00 1 CO-H 1 OJ OJ

1 x:s

• K •JC 1 •JC •JC e g o 1 S t s O 1 CJNCJN

O O 1

•JC •K 1 •JC • * 1 P^^sO 1 m O N 1

r^oo 1 O O 1

4-t

1 ^x 1 H 0 0 1 C O ' H 1 4.t OJ

1 c o : 2

• K -JC •JC -JC ^ 0 0 O N m 0 0 CJN

o o

• u 1 X 1 "H 00 1 CO'H 1 0) OJ 1 x:s

>N 4J •H >

O OJ CX CO OJ

u

X CO

X o u a

OJ

> OJ

o o • p

3 CO

m o

4-1 CO

3 CO O

3 00 •H

CO

I •JC •JC

OJ

> •H 4-1 CJ OJ CU CO OJ u

cn

+ OH O)

OH

OH

U O

OJ 3

r-i CO >

CO OJ 4J

o 3 OJ

13

37

weights

>% u

T3

ts and

•H CO U

4-t

r H CO CJ

•H

00

o r H

O X

morp

3 O

CO

4-t X 00

• H 0)

>» u

13

TS 3 CO

CO . 4-1 / - s

• H O CO 0 0 JH CJN 4J r H

V ^

r H CO CO O r H

• H OJ

0 0 > O OJ

X rH

o X u CX OJ Ul 4-t

O CO

a > 14H JH O OJ

> CO o 3 O CO

• H OJ 4-1 3 CO ' H

r H rH OJ

Corr

inbred

• O J-" r H O

14H OJ

rH X CO

H

4J

3 00 CO'H

r H OJ

O H 3

4-t

J= 14H 00 CO'H OJ OJ

4J

Stal

Welg

4-1 1 3 JS

CO 00

OJ 'H X OJ

1

o •u u O ' H

J= 4-1

OH OJ CO X OJ

r H 4J JH CO 3 < •w >. O CO

H

r H l 4 H CO CO CO OJ

4-1 OJ J H

O K J < : H

M CO 0) OJ

X ^ >

a O CO 3 OJ

Z H J

OJ r H a CO 3 OJ

3 H

-a< OJ

OH

0) r H J = O 4-t

3 00 3 3

13 OJ

0 ) r J OH

•JC •JC ON

o •

o

•K •K <JN

0.36

•K •K

.406

o

•K •K

O

m

0.2

•K •K

r>. 0 0 -3-

• O

•K •K eg

r St

• o

•K 1 • K 1

cn 1 m 1 CM 1

. j

O 1

•JC 1 •K 1

P>' 1 P^ 1

m 1 • 1

O 1

•K 1 •K 1

O 1 0 0 1

m 1 • 1

O 1

4J 1 4-iX 1 3 00 1 CO'H 1

H OJ 1 OH X 1

1 S t 1 0 0 1 O 1 •

1 o 1 1 1 1

1 0 0

-0.05

.001

1 o

1 •K 1 -K 1 ON 1 ON

-0.2

1 CJN

1 o 1 o 1 • o

1

m cn o

• o 1 1

•K 1 0 0 1

cn 1 r H 1

. 1

O 1

* 1 •JC 1 CM 1

m 1 ON 1

• 1

O 1

OJ 1 r-i 1 ^ X 1 3 4-i 1

3 00 1 T3 3 1 OJ (U 1

P4X 1

1 ON 1 r-4 1 0 1 •

1 0

1 m

0.03

.098

1 0

1 < * 1 ON

-0.1

1 m 1 0 1 r-4 1 .

1 0

0 0 r>v

0 •

0

•K 1

P^ 1 S t 1 r H 1

a 1

0 1

di 1 rH 1

U 1 3 1 3 CO 1

13 OJ 1 OJ U 1

o.<«: 1

1 •J* 1 •K 1 .JC 1 -JC 1 •K 1 •JC

1 m 1 0 0 1 m 1 cn 1 cn 1 cn 1 c n 1 0 0 1 0 0 1 • 1 • 1 .

1 0 1 0 1 0

1 * 1 -K 1 •JC 1 -K 1 •JC 1 •IC 1 0 0 1 sO 1 i n

0.33

0.80

0.80.

1 -JC 1 • * 1 -JC 1 •K 1 -JC 1 «

.434

.803

.804'

j 0 1 0 1 0

1 1 •K 1 •K ! 1 JC 1 -JC 1 ON 1 0 1 > ^ 1 rH 1 <-~) 1 OS

-0.1

0.51

0.4<

1 •K 1 •K 1 1 •JC 1 •K 1 1 ^ 1 ON 1 1 m I <jN 1 1 - ^ 1 CJN 1 1 . 1 . 1

0 1 0 1

CN 1 1 m 1 1 S t 1 1

• 1 1

0 1 1

1 1 CO 1 1 1 OJ 1 1 1 1 VH 1 1 1 o < 1 1 <4H 1 4-t 1

<4H 1 CO 1 0 U 1 0 1 OJ 1 X H 1

\ X 1 OH -U 1 V-l CO 1 1 01 1 OJ OJ 1 r H 1 HJZ 1

-O > 1 CO CO 1 CO 4-) 1

a CO 1 4-t OJ 1 4-t 3 1 3 OJ 1 0 JH 1 0 >%l

Z P - J 1 i H < 1 H CO 1

1 •JC 1 •JC

1 0 1 so 1 s o 1 •

1 0

1 •K 1 •JC 1 U3

0.52(

1 •K 1 Je

.470'

1 0

4-t 1 X 1

13 00 1 CO'H 1

OJ OJ 1

x:s 1

1 •K 1 • K 1 cn 1 m 1 ON 1 •

1 0

1 ^ I -K 1 . ^

0.84]

.

4-t 1 ^ X 1 <H 00 1 CO'H 1 4-t OJ 1

C 0 3 1

1 •K 1 -JC 1 CN

1 cn 1 ON 1 •

1 0

4_|

JZ 14H 0 0 CO'H

OJ OJ

r J S

vely.

' H

respect

4J

• H

r-i

robabJ

Cl.

>4H 0

level

r H 0

• 0

and

m 0

• 0

4-t

CO

Lgnificant

CO

1 1

•t(

•JC

•JC

38

PP + 1, and plant weight was not significant in PP + 3 when correlated

with plant height. Over water levels, peduncle length resulted in the

highest positive significant correlation (0.577) (Table 10) with plant

height as would be expected since internode length is directly related

to plant height, being measurements of the same overall genetic

expression.

An observation of the means (Tables 7 and 8) indicates wide

variation of all inbred lines for plant height and head dry weight

except R 9188 and TX 2737 which remained essentially constant over

water levels (LSD not significant). All morphological traits gave

significant negative correlations with grain yield in PP + 1 and PP +

3 except head dry weight which gave highly significant positive

correlations for both plot head weight and adjusted yield (Table 9).

However, large variations in grain yield (1000 kg/ha) between

environments for R 9188 and TX 2737 may 'be evidence these are early

lines able to use available water for grain yield (Table 11).

Correlation of peduncle length with morphological traits in PP +

1 and PP + 3 were negative when significant, except number of leaves

in PP + 3 (Table 9), as were r-values for grain yield traits (Table

11). Over water levels, a positive highly significant (P = .01)

correlation was observed between head dry weight and peduncle length.

This relationship would be expected since peduncle length is related

to plant height, and plant height and head dry weight were positively

correlated (Table 10).

No significant positive correlation of peduncle length with grain

yield was observed (Tables 11 & 12), unlike results reported for wheat

w 39

Table 11. Correlations of grain yield and related traits on morpho­logical traits and dry weights of inbred lines grown under pre­plant plus one (PP + 1) and preplant plus three (PP + 3 ) irriga­tion levels (1980).

PLOT

Head Weight

Adjusted Yield

Moisture Percentage

Plant Dry Weight

-0.044 -0.082

-0.152* -0.195*

0.330** 0.053

Threshing Percentage

Plant Height

Peduncle Length

Peduncle Area

Number of Leaves

Total Leaf Area

Total Photo­synthetic Area

Head Dry Weight

Stalk Dry Weight

Leaf Dry Weight

0.002 t 0.218**tt

-0.055 -0.372**

-0.036 -0.209*

-0.060 -0.243**

0.041 -0.232**

0.040 -0.238**

0.324** 0.291**

-0.151* -0.214**

-0.048 -0.075

-0.079 -0.339**

-0.049 -0.444**

-0.038 -0.369**

-0.168* -0.270**

-0.062 -0.389**

-0.064 -0.400**

0.277** 0.210**

-0.258** -0.315**

-0.140 -0.192*

0.324** 0.423**

0.167* 0.515**

0.155* 0.622**

0.486** 0.497**

0.291** 0.203**

0.296** 0.221**

-0.232** ^0.320**

0.420** 0.186*

0.330** 0.051

-0.278** -0.023

-0.023 0.197*

-0.043 -0.326**

-0.310** -0.084

-0.278** -0.356**

-0.280** -0.366**

0.100 -0.106

-0.385** -0.234**

-0.267** -0.234**

-0.311** -0.231**

*, ** - significant at 0.05 and 0.01 probability level, respectively. t, ft - denotes value for PP + 1 and PP + 3, respectively.

40

Table 12. Correlations of grain yield and related traits on morpho­logical traits and dry weights for inbred lines over water lev­els (1980).

PLOT PLANT

Head Weight

Adjusted Yield

Moisture Percentage

Threshing Percentage

Plant Height

Peduncle Length

Peduncle Area

Number of Leaves

Total Leaf Area

Total Photo­synthetic Area

Head Dry Weight

Stalk Dry Weight

Leaf Dry Weight

Plant Dry Weight

0.521**

0.095

0.171**

-0.083

0.200**

0.204**

0.492**

0.060

0.181**

0.200**

0.296**

-0.029

0.010

-0.167

0.009

0.010

0.401**

-0.104

0.024

0.036

-0.310**

0.028

0.056

0.365**

-0.068

-0.067

-0.447**

0.075

-0.033

-0.065

-0.617**

-0.301**

-0.365**

-0.183**

-0.464**

-0.473**

-0.269**

-0.387**

-0.377**

-0.406**

** - significant at 0.01 probability level

41

by Briggs and Aytenfisu (1980). Correlations between peduncle area

and morphological traits and dry weights followed the same patterns as

peduncle length except for a significant negative correlation with

head dry weight of -0.194 in PP + 1 (Table 10). No positive

correlation between peduncle area and leaf area or photosynthetic area

indicates that size of peduncle area in relation to photosynthetic

area was either too small to have an effect or leaf area and peduncle

area develop independently.

Peduncle length and plant height are the result of internode

expansion. The positive significant association (Tables 9 & 10) of

peduncle length with plant height indicates taller inbreds had longer

peduncles. However, an observation of the means (Table 7) reveals

that even though SC 170-6-17 had large variations for height from PP +

1 and PP + 3 of about 20 cm, peduncle length remained essentially

constant as did peduncle length of TX 7078 and NSA 440. Selection of

types not varying for peduncle length in various environments would

result in a genotype with a good combine harvest characteristic.

Correlation coefficients for number of leaves were positive and

highly significant (P = .01) with all dry weights in PP + 1 and PP + 3

(Table 9) and over water levels (Table 10) except head dry weight

being negative when significant. Data indicates as leaf number

increased dry weight increases as expected since number of leaves is

directly related to leaf weight and so to plant weight. Negative

correlation between head dry weight and number of leaves could be due

to inbreds SC 56-14, SC 35-14 and R 9188 having small head dry weights

and large leaf numbers in PP + 1 and PP + 3. Correlations between

42

number of leaves and grain yield were negative when significant for PP

+ 1, PP + 3, and over water levels (Tables 11 & 12). This type of

association with head dry weight and grain yield could relate to

optimal vegetative production for maximum grain yield under water

stress referred to by Fisher and Kohn (1966b). SC 56-14, SC 35-14,

and R 9188 may have put on excess leaf area using water needed later

t-

for grain filling. The excess leaf area could be due to June 30

irrigation near the time of panicle initiation resulting in more

leaves being initiated or allowing leaves already initiated, but not

mature, to increase in size.

Correlations between leaf area and total photosynthetic area with

dry weights in PP + 1 and PP + 3 (Table 9) and over water levels (Table

10) were all positive and highly significant (P = -01). Leaf number,

leaf area, and total photosynthetic area are directly related being

similar measurements of the same genetic expression. Correlations of

these three traits with dry weights followed the same pattern, except

for a significant negative correlation in PP + 1 between leaf number

and head dry weight.

Leaf area and photosynthetic area correlations between grain

yield and associated traits were negative when significant in PP + 1

and PP + 3 (Table 11) and were not significant over water levels

(Table 12). This contradicts results reported by Voldeng and Simpson

(1967) and Simpson (1968) of positive correlations between grain yield

of wheat and photosynthetic area. Stickler and Pauli (1961) reported

increased relative yield per unit leaf area when leaves were removed,

implying that less leaf area may give a compensation effect allowing

43

assimilates that may otherwise be diverted to leaf area production to

be used for grain yield.

From the photosynthetic area data, conclusions can be made that R

9188 and TX 2737 were the most consistent (LSD not significant), each

varying only slightly between water levels. No significant positive

correlation between photosynthetic area and grain yield was observed

(Tables 11 & 12), contrary to results obtained by Leeton (1978). An

observation of the means (Table 7) indicates TX 2737 and R 9188 had

consistent photosynthetic areas, but wide variation (LSD significant)

in grain yield between water levels. In contrast, TX 7000 and SC 170-

6-17 had wide variation (LSD significant) in photosynthetic area, but

grain yields between treatments (LSD for TX 7000 not significant, but

SC 170-6-17 significant) were not as variable as other inbred lines.

Inbreds TX 7000 and SC 170-6-17, added extra leaf area with additional

water. However, these two lines not having a corresponding increase

in grain yield, may be an indication of inefficient partitioning.

This relates to the optimal amount of vegetative growth produced in

relation to grain yield referred to by Fisher and Kohn (1966b).

Over water levels correlations were positive and highly

significant (P = -01) between plant height and photosynthetic area

(Table 10), evidence that the taller lines produced more leaves and

stalk, and larger peduncles at maturity. This indicates that

selection for any one of these traits would have an effect on other

traits for these inbred lines.

Correlations between plant dry weights were all highly signifi­

cant and positive for PP + 1, PP + 3, and over water levels as expected

44

since these similar measurements of the same genetic system. Over

water levels correlations of head dry weight, leaf dry weight and

plant dry weight with plot head weight were positive and highly

significant (P = .01) (Table 12). Correlations between dry weights

and plot head weight and adjusted yield were negative when significant

in PP + 1 and PP + 3 (Table 11). Over water levels head dry weight,

leaf dry weight and plant dry weight gave positive, highly significant

(P = .01) correlations with plot head weight (Table 12). Only head

dry weight gave positive significant correlations with adjusted yield

(Tables 11 & 12). The highly significant positive correlation between

head dry weight at bloom and plot head weight can be explained as

being due to florets produced in the panicle leading to final grain

yield.

Data for means of dry weights and adjusted yield (Table 8)

indicate that genotype by water level interactions resulted in wide

variation between treatments. TX 7000 had a decrease in head weight

of about 6 grams from PP + 3 to PP + 1, but only a 500 kg/ha decrease

in grain yield (Table 8). This contrasts with R 9188 and TX 2737

which had essentially the same head dry weight with either water

level, but grain yield decreases of over 1000 kg/ha.

Stalk dry weight was reduced for TX 7000 and SC 170-6-17 while

other genotypes did not decrease as greatly from PP + 3 to PP + 1. The

observation of Wardlaw (1967) and Boyer (1976) that assimilates are

translocated from the stalk to fill the grain could explain part of

the grain yield results obtained for TX 7000 and SC 170-6-17.

45

NSA 440 also had a large decrease in head dry weight from PP + 3

to PP + 1, and although grain yield was only decreased 300 kg/ha, rank

in relation to other lines for grain yield was low (Table 8).

Head dry weight at bloom was positively correlated with grain

yield (Tables 11 & 12). An observation of the data indicates that

although TX 7000 and SC 170-6-17 had large decreases in head dry

weight, the reductions in grain yield were not as substantial as the

reduction for R 9188 and TX 2737. NSA 440 ranked second in PP + 1 for

head dry weight, but sixth for adjusted yield, indicating an inability

to fill the grain.

Head dry weight over water levels (Table 8) for SC 170-6-17 was

lower than TX 2737, TX 7078, and TX 7000, but adjusted yields of these

lines were not significantly different. In the PP + 1, head dry

weights for TX 2737 and TX 7078 were significantly different from SC

170-6-17 and TX 7000, but adjusted yield was not significant. In PP +

3, head dry weight and adjusted yield for the four lines were not

significantly different.

The means for adjusted yield of TX 7000 and SC 170-6-17 were more

consistent over both water levels (Table 8). If stability of yield

over a range of environments was desired, these would be the types of

lines selected for use in a breeding program due to their ability to

produce grain yield when water is limiting.

Data for plant dry weight (Table 8) indicates TX 7000 and SC 170-

6-17 had large variation in dry matter production between water levels

at bloom while R 9188 and TX 2737 remained essentially the same in

both treatments. Adjusted yield of TX 7000 and SC 170-6-17, though

46

not significantly different, exceeded TX 7078 by 400 kg/ha and 240

kg/ha, respectively. Evidence is provided that TX 7000 and SC 170-6-

17 were able to use the available moisture in PP + 1 for grain fill

rather than vegetative growth.

Plant dry weight of inbred lines R 9188 and TX 2737 remained

essentially the same in either environment (Table 8). However, wide

variations in grain yield indicate an interaction of water level with

genotype for grain yield, but not vegetative growth. This could be

due to early maturity or extensive growth of the root system.

Correlations between plot head weight, grain weight, and adjusted

yield were highly significant and positive in PP + 1, PP + 3, and over

water levels (Table 13) as would be expected since these are directly

related. However, correlations between these grain yield traits and

moisture percentage were significant and negative in PP + 1 and PP +

3, and over water levels. Threshing percentage had a highly

significant (P = .01) negative correlation with plot head weight over

water levels (Table 13). This indicates excess nonseed portions were

produced in relation to grain.

An observation of the means indicates that inbreds with the

largest grain yield had the lowest moisture percentage and highest

threshing percentage (Table 8). Lines SC 56-14, SC 35-14, and NSA 440

had low grain yields, high moisture percentage, and low threshing

percentage, evidence that late maturity could account for some of the

low yielding potential for these inbred lines.

47

Table 13. Correlations between grain yield and related traits for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels and over water levels (1980).

Plot Head Weight

Adjusted Yield

0.958**t 0.844**tt 0.900**^

Moisture Percentage

-0.419** -0.195* -0.618**

Threshing Percentage

0.387** -0.024 -0.375**

Plot Adjusted Yield -0.546** -0.323** -0.627**

0.614** -0.268** 0.035

Moisture Percentage -0.634** 0.504** 0.098

* * _

t, tt. significant at 0.05 and 0.01 probability level, respectively. ^ - denotes value for PP + 1, PP + 3, and over water levels,

respectively.

CHAPTER V

SUMMARY AND CONCLUSIONS

The major objectives of this study were to (1) determine what

genotypic variation existed among eight sorghum inbred lines, (2)

determine genotype by environment interaction, (3) determine if a

relationship existed between leaf area and related morphological

traits and grain yield, and (4) identify inbred lines suitable for

further genetic study.

Significant genotypic differences were consistently detected at

the 0.01 level of probability for all morphological traits and grain

yield, leading to the conclusion that variation exists among the eight

genotypes for traits tested. Water level by genotype interaction

resulted in significant differences for all morphological traits

excluding number of leaves. This observation is contradictory to

results obtained by others of decreased leaf numbers with water

stress. The lack of variation in number of leaves observed in this

study could be explained in part as resulting from the inbred lines

growing in comparable macroenvironments during the leaf initiation

period. More data should be obtained to determine if this lack of

variation is due to genetic effects or if the environmental effects of

this study were not effective in attaining a response.

Water level had a modifying effect on photosynthetic area,

causing significant increases from PP + 1 to PP + 3. TX 7000 and SC

170-6-17 added additional leaf area with additional water, but there

48

49

was little increase In grain yield observed indicating inefficient

partitioning of assimilates for grain production.

Evidence of differential water use was obtained from the

significant genotype by water level interactions of morphological

traits measured as dry weights. These results suggest certain inbreds

perform better under higher water levels and others under lower water

levels. Inbred lines should be evaluated to determine such responses

to water levels since, depending upon correlations with grain yield,

particular lines may be better suited to a specific water level, and

provide superior segregates for such traits in a breeding program.

Significant reductions in the stalk dry weights of TX 7000 and SC

170-6-17 and a small decrease in grain yield relative to other inbred

lines were observed. These results may imply utilization of stalk

stored assimilates in these two lines. However, no positive

significant correlation of stalk dry weight at bloom with grain yield

was observed. If stalk stored assimilates are important for grain

filling in sorghum, evaluations of this trait are needed. The ability

of an inbred to use stalk stored assimilates for grain yield during

periods of water stress would be an important factor from a breeding

standpoint.

Genetic differences were detected among inbred lines for grain

yield. Genotype by water level interaction was not significant for

grain yield. However, the interaction gave significant differences

for unthreshed head weight. These results indicate the relative

position of an inbred line did not change over water levels, and

additional water was used for vegetative, not reproductive growth.

50

This could be an indication of inefficient partitioning. Some of the

variation in performance among inbreds for grain yield could be

explained by early maturity and leaf senescence. While these

characteristics are desirable in some environments, they are not

always advantageous in all environments. The use of these character­

istics by the breeder is dependent on the type of environment he is

concerned with in his breeding program.

Most positive significant correlations obtained were attributable

to measurement of the same overall genetic system. Significant

negative correlations between photosynthetic area or leaf area and

grain yield suggest less relative leaf area may be beneficial when

water is limiting. Head dry weight at bloom was the only

morphological characteristic exhibiting a positive significant rela­

tionship with grain yield which could merit further evaluation to

determine usefulness in screening of inbred lines.

APPENDIX

1. Precipitation after June 4 for 1980 growing season and 1980 totals to date recorded at Texas Tech University Farm.

51

52

Appendix Table 1. Precipitation after June 4 for 1980 growing sea­son and 1980 totals to date recorded at Texas Tech University Farm.

Precipitation Total to Date Total for Year

Date (mm) (mm) (mm)

June 8 5.1 5.1 90.6

June 11 23.3 28.4 113.9

July 27 14.4 42.8 128.3

August 4 26.9 69.7 155.2

August 14 16.2 85.9 171.4

August 15 7.6 93.5 179.0

September 1 2.0 95.5 181.0

September 9 7.1 102.6 188.1

September 10 15.2 107.8 203.3

REFERENCES CITED

1. Acevedo, E., T. C. Hsiao, and D. W. Henderson. 1971. Immediate and subsequent growth responses of maize leaves to changes in water status. Plant Physiol. 48:631-636.

2. Bennett, J. M. 1975. The effect of light and water stress on yield and yield components of grain sorghum. M.S. Thesis, Texas Tech University.

3. Birecka, H., J. Skupinska, and I. Bernstein. 1967. Photo­synthetic activity before and after heading in spring barley. Acta. Soc. Bot. Pol. 36(2):386-409- (English summary in Biol. Abstr..Vol. 49, No. 36758).

4. Blum, A. 1974. Genotypic responses to sorghum to drought stress. I. Response to soil moisture stress. Crop Science 14:361-364.

5. Boyer, J. S. 1976. Photosynthesis at low water potentials. Phil. Trans. R. Soc. Lond. B. 273:501-512.

6. Briggs, K. G. and A. Aytenfisu. 1980. Relationship between morphological characters above the flag leaf node and grain yield in spring wheats. Crop Science 20:350-354.

7. Campbell, C. M. 1964. Influence of seed formation of corn on accumulation of vegetative dry matter and stalk strength. Crop Science 4:31-34.

8. Clark, L. E. 1970. Embryonic leaf number in sorghum. Crop Science 10:307-309.

9. Clarke, L. E. and D. Pietsch. 1980. Grain sorghum yield performance, Chillicothe—1980. TAES Bulletin PR-3730, Mar­ch, 1981.

10. Clegg, M. D. 1969. Row spacing, plant population and light interception as they influence sorghum yield. Ln Proceedings of the 24th annual corn and sorghum research conference.

11. Daynard, T. B., J. W. Tanner, and D. J. Hume. 1969. Contribution of stalk soluble carbohydrates to grain yield in corn (Zea mays L.). Crop Science 9:831-834.

12. Eastin, J. D. and C. Y. Sullivan. 1969- Carbon dioxide exchange in compact and semi-open sorghum inflorescences. Crop Science 9:165-166.

13. Elk, Kalyu, J. J. Hanway. 1966. Leaf area, its relation to yield of corn grain. Ag. J. 58:16-18.

53

54

14. El-Sharkaway, M. A. and J. D. Hesketh. 1964. Effects of temperature and water deficit on leaf photosynthetic rates of different species. Crop Science 4:514-518.

15. Fischer, K. S. and G. L. Wilson. 1971. Studies of grain production in Sorghum vulgare. I. The contribution of preflowering photosynthesis to grain yield. Aust. J. Agric. Res. 22:33-37.

16. Fischer, K. S., G. L. Wilson and I. Duthie. 1976. Studies of grain production in Sorghum bicolor (L. Moench). VII. Contribution of plant parts to canopy photosynthesis and grain yield in field situations. Aust. J. Agric. Res. 27:235-242.

17. Fisher, R. A. and G. D. Kohn. 1966a. The relationship between evapotranspiration and growth in the wheat crop. Aust. J. Agric. Res. 17:255-267.

18. Fisher, R. A. and G. D. Kohn. 1966b. The relationship of grain yield to vegetative growth and post-flowering leaf area in the wheat crop under conditions of limited soil moisture. Aust. J. Agric. Res. 17:281-295.

19. Graham, D. and K. J. Lessman. 1966. Effect of height on yield and yield components of two isogenic lines of Sorghum vulgare Pers. Crop Science 6:372-374.

20. Hadley, H. H. 1957. An analysis of variation in height in sorghum. Agronomy Journal 49:144-147.

21. Hadley, J., J. E. Freeman, and E. Q. Javier. 1965. Effects of height mutations in grain yield in sorghum. Crop Science 5:11-14.

22. Herbert, S. W., S. Fukai, and G. L. Wilson. 1982. Plant characteristics associated with high grain yield under high and low moisture availability. Sorghum Newsletter 25:1.

23. Keim, D. L. and W. E. Kronstad. 1981. Drought response of winter wheat cultivars grown under field stress conditions. Crop Science 21:11-15.

24. Lawes, D. A. and K. J. Treharne. 1971. Variation in photosyn­thetic activity in cereals and its implication in a plant breeding programme. I. Variation in seedling leaves and flag leaves. Euphytica 20:86-92.

25. Leeton B. S. 1978. Photosynthetic variation in sorghum geno­types. M.S. Thesis, Texas Tech University.

55

26. Major, D. J. and W. M. Haman. 1981. Comparison of sorghum with wheat and barley grown on dryland. Can. J. Plant Sci. 61:37-43.

27. McKree, K. J. and S. D. Davis. 1974. Effect of water stress and temperature on leaf size and number of epidermal cells in grain sorghum. Crop Science 14:751-755.

28. Moss, D. N. and R. B. Musgrave. 1971. Photosynthesis and crop production. Advances in Agronomy 23:317-336.

29. Pauli, A. W., F. C. Stickler, and J. R. Lawless. 1964. Developmental phases of grain sorghum (Sorghum vulgare Pers.) as influenced by variety, location, and planting date. Crop Science 4:10-13.

30. Porter, H. K., N. Pal, and H. V. Martin. 1950. Physiological studies in plant nutrition. XV. Assimilation of carbon by the ear of barley and its relation to the accumulation of dry matter in the grain. Annals of Bot. Lond. 14:55-68.

31. Quinby, J. R. 1972. Influence of maturity genes on plant growth in sorghum. Crop Science 12:490-492.

32. Quinby, J. R. , J. D. Hesketh, and R. L. Voigt. 1973. Influence of temperature and photoperiod on floral initiation and leaf number in sorghum. Crop Science 13:243-246.

33. Ramos, J. M., L. F. Garcia de Moral, and L. Recalde. 1983. Dry matter and leaf area relationships in winter biology. Ag^ J. 75:308-309.

34. Sanchez-Diaz, M. F. and P. J. Kramer. 1971. Behavior of corn and sorghum under water stress and during recovery. Plant Physiol. 48:613-616.

35. Shertz, K. F. 1970. Single-height-gene effects in doubled haploid sorghum bicolor (L.) Moench. Crop Science 10:531-534.

36. Sieglinger, J. B. 1936. Leaf number of sorghum stalks. Ag. J. 28:636-642.

37. Simpson, G. M. 1968. Association between grain yield per plant and photosynthetic area above the flag leaf node in wheat. Can. J. Plant Sci. 48:253-260.

38. Steel, R. G. D. and J. H. Torrie. 1960. Principles and Procedures of Statistics. McGraw-Hill, New York.

56

39. Stickler, F. C. and A. W. Pauli. 1961. Leaf removal in grain sorghum. I. Effects of certain defoliation treatments on yield and components of yield. Ag. J. 53:99-102.

40. Stickler, F. C., S. Wearden, and A. W. Pauli. 1961. Leaf area determination in grain sorghum. Ag. J. 53:187-188.

41. Stout, D. G., T. Kannangara, and G. M. Simpson. 1978. Drought resistance of Sorghum bicolor. 2. Water stress effects on growth. Can. J. Plant Sci. 58:225-233.

42. Vinall, H. N. and H. R. Reed. 1918. Effect of temperature and other meteorological factors on the growth of sorghums. J. Ag. Res. 13:133-148.

43. Voldeng, H. D. and G. M. Simpson. 1967. The relationship between photosynthetic area and grain yield per plant in wheat. Can. J. Plant Sci. 47:359-365.

44. Walton, P. D. 1969. Inheritance of morphological characters associated with yield in spring wheat. Can. J. Plant Sci. 49:587-596.

45. Wardlaw, I. F. 1967. The effect of water stress on transloca­tion in relation to photosynthesis and growth. I. Effect during grain development in wheat. Aust. J. Biol. Sci. 20:25-39.

46. Wareing, P. F., M. M. Khalifa, and K. J. Treharne. 1968. Rate-limiting processes in photosynthesis at saturating light intensities. Nature 220:453-457.

47. Watson, D. J. 1942. The physiological basis of variation in yield. Advances in Agronomy 4:101-145.

48. Watson, D. J., G. N. Thorne, and S. A. W. French. 1958. Physiological causes of differences in grain yield between varieties of barley. Annals of Botany 22:321-352.

49. Watson, D. J., G. N. Thorne, and S. A. W. French. 1963. Analysis of growth and yield of winter and spring wheats. Annals of Botany 27:1-22.

V