8%. E. H“ {CST OF SUr’RAOPfl’me
TEMPERMURES U ON CREEPE?‘ G 88‘ QTGRASS
(AGROSTfi PALUS:R!S HUDS.)

Thesis far ire“ degree of Ph D.
MICMAN STATE UNIVERSITY
D. THOMAS DUFF
1967

-- AAA-l-

  
 
  

LIBRARY

Mia}; .. -: Tunic
University

mums

 

 

This is to certify that the

thesis entitled

Some Effects of Supraoptimal
Temperatures Upon Creeping Bentgrass
(Agrostis Palustris Huds.)

presented by

D. Thomas Duff

has been accepted towards fulfillment
of the requirements for

Ph.D. degree in Crop_ Science

{OX/Wm flak/LA

Major professor

Date June 16, I967

 

0-169

ABSTRACT

SOME EFFECTS OF SUPRAOPTIMAL TEMPERATURES
UPON CREEPING BENTGRASS
(Agrostis palustris Huds.)

 

by D. Thomas Duff

The detrimental effects of supraoptimal temperatures
upon the growth of creeping bentgrass turf result in many
problems in the field. Grass vigor is reduced during high
temperature periods of the summer season. This study was
initiated to elucidate some effects of supraoptimal temper—
atures upon creeping bentgrass.

Sod pieces of Toronto creeping bentgrass were removed
from the field, and placed in the greenhouse and growth
chamber for a nine-week establishment period. The grass
was then grown at successive light—dark temperature regimes
of 20-10, 25-15, 30-20, 35-25 and 40-30 C utilizing a 16—8
hour cycle. Leaf clipping harvests were made once per week
at a 1.3 cm cutting height for a four-week period under
each temperature regime.

The yield of clippings from a turf was considered as
a function of the leaf area removed and the weight per unit
area of the leaves. In this study, leaf dry weight per
unit area increased lineraly with temperature. Decrease in
the dry weight yield of clippings was brought about by
decreased leaf area production. At the lower temperatures,

leaf area reduction was characterized more by reduced leaf

D. Thomas Duff

width than leaf length. At the higher temperature levels,
it was influenced more by decreased leaf length than leaf
width.

Production of leaf clippings and the level of both 85
per cent ethanol and water soluble carbohydrates in the
leaves varied in an inverse manner. Carbohydrate content
of clippings was greatest at the highest temperature regime,
when clipping yield was lowest. Leaf sheath, stem and
stolon tissue contained as much carbohydrate as leaf tissue.
Accumulation of carbohydrate in the leaves at high tempera-
ture levels could not be attributed to disruption of trans-
location to lower portions of the plant. Decrease in leaf
dry matter production was not attributable to depletion of
reserve carbohydrates within the leaf tissue.

Reduction of turf density at the highest temperature
regime could not be attributed to carbohydrate depletion
within the lower portions of the plant. Plants which had
ceased active leaf production and had become chlorotic con-
tained a carbohydrate level equivalent to plants which
remained green and still produced new leaves.

Photosynthetic rates were determined manometrically
under non-limiting light and carbon dioxide levels. Under
these conditions, nonphotochemical reactions limiting
photosynthesis were evaluated. Leaves produced at 40-30 C
exhibited a greater photosynthetic rate per unit area than
those grown at 20-10 C when they were tested at 20, 30 and

A0 C. This effect was probably due to quantitative changes

D. Thomas Duff

brought about by morphological differences resulting in a
greater number of photosynthetic units per unit leaf area.
Leaf tissue produced at AO-3O C also exhibited a smaller
depression in Q10 at A0 C than those leaves grown at 20—10
C. This result was brought about by uncharacterized quali-
tative changes in leaf tissue grown at “0—30 C. The
quantitative and qualitative changes in leaf tissue grown
at 40—30 C indicated that adaptive mechanisms were influ-
encing the photosynthetic rate when considered on a per
unit area basis of leaves grown at this temperature. Res-
piration rates were also determined manometrically. Changes
similar to those affecting photosynthetic rate were not
found.

Although adaptive mechanisms were indicated in the
photosynthetic rate per unit area of leaves grown at “0-30
C, much less leaf area was produced. The effects on photo-
synthetic capability and the ample carbohydrate supply did
not result in healthy minature plants. At the “0—30 C
temperature regime, many plants died from causes other

than those evaluated in this study.

SOME EFFECTS OF SUPRAOPTIMAL TEMPERATURES
UPON CREEPING BENTGRASS

(AGROSTIS PALUSTRIS HUDS.)

 

By

Lb
D9 Thomas Duff

A THESIS

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

DOCTOR OF PHILOSOPHY
Department of Crop Science

1967

ACKNOWLEDGMENTS

The author wishes to eXpress his appreciation to
Dr. J. B. Beard for his guidance, advice and critical
evaluation during the course of this investigation and
preparation of the thesis.

In addition, appreciation is expressed to those
members of the faculty who generously gave of their time
and talents to review and criticize the thesis manuscript
during its preparation.

The author also wishes to take this opportunity to
thank all those members of the faculty who have generously
and unfailingly given their time, advice and assistance

during his period of graduate study.

11

TABLE OF CONTENTS

ACKNOWLEDGMENTS
LIST OF TABLES .
LIST OF FIGURES

LIST OF APPENDIX TABLES

INTRODUCTION
LITERATURE REVIEW
MATERIALS AND METHODS
RESULTS . . . .
DISCUSSION OF RESULTS
SUMMARY

CONCLUSIONS

LITERATURE CITED

APPENDIX

iii

Page
ii
iv
vi

vii

l3
19
3A
“3
A6

A8
52

Table

10.

LIST OF TABLES

The number of leaves out of 160 falling in
three width classes when grown at five
temperature regimes . . . . . . . . .

The number of leaves out of 160 falling in
four length classes when grown at five
temperature regimes

Percentage dry weight of leaf tissue produced
under five temperature regimes . . . . .

Milligrams dry weight per square centimeter
of leaf area produced under five temperature
regimes . . . . . . . . .

Dry weight of clippings, grams per 25.8
square decimeters per week at five tempera-
ture regimes . . . . . . . . . . .

Chlorophyll content of leaf clippings, micro-
grams per milligram dry weight at five
temperature regimes . . . . . . .

Chlorophyll content, micrograms per square
centimeter of leaf area at five temperature
regimes . . . . . . . . . . . . .

85 per cent ethanol soluble carbohydrate
content of leaf tissue produced under five
temperature regimes: percentage of dry
weight of tissue . . . . . . .

Water soluble carbohydrate content of leaf
tissue produced under five temperature
regimes: percentage of dry weight of
tissue . . . . . . . . . . . . .

Water soluble carbohydrate content of stem
and stolon tissue, per cent of the dry

weight . . . . . . . . . . . . .

iv

Page

21

21

23

23

2A

25

26

26

28

28

Table Page

11. Photosynthetic rate of leaf tissue grown at
20-10 and 40-30 C and tested at the indi-
cated temperatures: microliters per
square centimeter per hour . . . . . . . 32

12. Relative photosynthetic rate per unit area of
leaves grown at 20-10 and 40-30 C and
tested at the indicated temperatures . . . 32

13. Respiratory rate of leaf tissue grown at
20-10 and AO-3O C and tested at the indi-
cated temperatures: microliters per
square centimeter per hour . . . . . . . 33

LIST OF FIGURES

Figure Page

1. Cumulative O Production of Leaves Grown and
Tested at She Indicated Temperatures.
Microliters per Square Centimeter . . . . 3O

2. Cumulative C02 Production of Leaves Grown and

Tested at the Indicated Temperatures.
Microliters per Square Centimeter . . . . 30

vi

Table

II.

III.

IV.

VI.

VII.

VIII.

IX.

XI.

XII.

LIST OF APPENDIX TABLES

Leaf dry matter production, grams per 25.8
square decimeters . . . . . . . .

Analysis of variance, leaf dry matter produc-
tion, grams per 25.8 square decimeters . . .

Per cent dry weight of harvested leaf clippings.

Analysis of variance, per cent dry weight of
harvested leaf clippings . . . . .

Leaf dry weight, mg per square centimeter . .

Analysis of variance, leaf dry weight, mg per
square centimeter . . . . . . . .

Chlorophyll content of harvested leaf clippings,
micrograms per mg dry weight . . . .

Analysis of variance, chlorophyll content of
harvested leaf clippings, micrograms per mg
dry weight . . . . . . . . . .

Content of 85 per cent ethanol soluble carbo-
hydrate in harvested leaf clippings: per
cent of the dry weight . . . . . .

Analysis of variance, content of 85 per cent
ethanol soluble carbohydrate in harvested
leaf clippings: per cent of the dry weight .

Content of water soluble carbohydrate in
harvested leaf clippings: per cent of the
dry weight . . . . . . . . . . .

Analysis of variance, content of water soluble

carbohydrate in harvested leaf tissue: per
cent of the dry weight . . . . . .

vii

Page

53

53
5A

5A
55

55

56

56

57

57

58

58

Table Page

XIII. Photosynthetic rate of leaves grown at the
indicated temperature regime and tested at
the light period temperature extant:
microliters per square centimeter per hour . 59

XIV. Analysis of variance, photosynthetic rate of
leaves grown at the indicated temperature
regime and tested at the light period
temperature extant: microliters per square
centimeter per hour . . . . . . . . . 59

XV. Respiratory rate of leaves grown at the
indicated temperature regime and tested at
the light period temperature extant:
microliters per square centimeter per hour . 6O

XVI. Analysis of variance, respiratory rate of
leaves grown at the indicated temperature
regime and tested at the light period
temperature extant: microliters per square
centimeter per hour . . . . . . . . . 6O

XVII. Photosynthetic rate at three temperatures
and two light intensities . . . . . . . 61

XVIII. Photosynthetic rate of leaves at three

calculated carbon dioxide levels and 30 C:
microliters per mg dry weight per hour . . 61

viii

INTRODUCTION

The growth pattern of cool season grasses in response
to temperature has been the object of study in numerous
investigations. A definite seasonal trend of rapid growth
during the cool period of spring is followed by reduced
growth under the influence of warm summer temperatures.

The latter period is followed by a secondary increase in
growth during the cooler autumn season.

Most grasses utilized for turf in the cool humid
region of the United States are classified as cool season.
Turf managers in this area are cognizant of a general decline
in turf vigor during periods of high summer temperatures.
Reduced turf vigor leads to enhanced management requirements
during these periods. The turf is less able to resist addi—
tional stress placed upon it whether of natural or mechani-
cal origin.

Some workers have attributed the decline in growth at
high temperatures to decreased carbohydrate supply within
plant tissues. It has been shown that the temperature
optimum for photosynthesis is lower than that of respiration.
At some point, growth as measured by the rate of dry matter
production might be governed by a reduced supply of carbon
skeleton for assimilation. Other workers have found little
relationship between carbohydrate content and growth rate.

1

Thus, there is lack of agreement concerning the role of
carbohydrate levels in regulating growth rate.

This study was initiated to investigate some of the
effects of supraoptimal temperatures upon creeping bent-
grass. Clarification of these effects could be of value in
developing management practices which would permit the

grass to withstand better the stress of summer temperatures.

LITERATURE REVIEW

The influence of temperature upon plant growth has
often been studied.

Lundegardh (l3) discussed a generalized growth-
temperature relationship and pointed out that from low to
higher temperatures the Q10 value continuously changes. At
some point an optimum is reached and above this level, at
supraoptimal temperatures, the Q10 becomes less than unity.
At supraoptimal temperatures, the curve falls rapidly so
that at temperatures only slightly above the optimum,
growth is greatly reduced. The optimum cannot be con-
sidered as a sharply defined point since it is influenced
by many other factors of the environment to which a plant
may be subjected.

The effect of temperature upon the growth of Kentucky
bluegrass was studied by Harrison (9). Grass cultures were
grown at 60, 80, and 100 F. Cultures grown at 60 F and
supplied with nitrogen produced equivalent clipping weights
between 10—day cutting intervals for a 50-day period. Those
cultures supplied with nitrogen and grown at 80 F produced
more clippings than the 60 F grown the first harvest, but
in successive intervals, the clipping yield of the former
decreased. Cultures placed at 100 F grew very little the

first 10 days, and in subsequent periods, no growth took

place. The effect of the 80 F temperature was time depend-
ent, but the effect of 100 F was shown very quickly.

Stuckey (23) noted the effect of 50, 60, and 80 F soil
temperatures upon the growth of Colonial bentgrass. She
found both root and top growth were greatest at 60 F with
lower amounts at 50 F and the least at 80 F.

Brown (3) found the optimum for herbage production of
Kentucky bluegrass to be between 80 and 90 F. Exposure to
a constant soil and air temperature of 100 F resulted in
severe injury which developed gradually. This temperature
did not result in sudden death of the plants. In later work
in the field, Brown (A) found that top growth of Kentucky
bluegrass reached its peak when mean temperatures reached 60
to 6A F. Herbage production declined at temperatures near
or above 80 F.

Sullivan and Sprague (2A) studied the effects of four
temperature regimes upon the regrowth of perennial ryegrass.
All plants were grown at a temperature of 70 F, clipped, and
placed under the test temperature. Regrowth was measured
periodically for 40 days. Plants placed at 60-70 F night-
day temperatures produced the greatest top growth. The
least amount was produced at the end of the test period
under the 80-90 F temperature regime.

The influence of temperature upon the yield of clip-

pings of creeping bentgrass (Agrostis palustris) was inves-

 

tigated by Jordan (11). He found that of the three

temperatures 60, 70, and 80 F, the greatest clipping yield
was at 70 F. Yield at 60 F was somewhat less and that at
80 F considerably less.

Pellet and Roberts (I?) grew Kentucky bluegrass in
solution culture. They found a decreased growth rate as
temperatures increased in the greenhouse regardless of the
nutrient level of their culture solution.

The optimum temperature for production of leaf tissue
of the cool—season grasses discussed above was generally
found to be approximately 60—70 F. Temperatures lower than
this order of magnitude resulted in decreased leaf growth
as did those above this level.

The type of leaf produced at various temperatures was
reported by Sullivan and Sprague (24). They noted that at
the 21-day sampling period, leaves at 60-70 F were vigorous
in appearance, of good color, and were 5-8 inches long.
Those at 50-60 F were second best and were 2-5 inches in
length. Leaves of plants at 70-80 F were spindly and
lacked vigor. At 80-90 F, leaves were 1-5 inches long and
had a very dark green color.

Darrow (5) also reported temperature effects upon leaf
development. He found Kentucky bluegrass leaves grown at
15 C soil temperature were long and succulent and that
numerous new leaves were produced. At a soil temperature
of 35 C, however, the leaves were short and rigid with many
of them remaining erect. Leaf production and bud initiation

were limited at 35 C.

Sullivan and Sprague (2A) reported the percentage dry
weight of the new leaf tissue produced in their study.
Leaves produced at the 60—70 F temperature regime contained
18.6 per cent dry matter, while those produced at the 80—90
F level contained 23.5 per cent.

Pellet and Roberts (17) found an increase in percent—
age dry weight with increased temperature. They also found
that Kentucky bluegrass cultures supplied with a high level
of N, P, and K had a lower percentage dry weight than those
receiving a low level.

Although Harrison (9) did not report the percentage
dry weight of harvested leaves, he did report green and dry
weights of his harvests from which the percentage dry
weight can be calculated. On the first cutting date after
placing the cultures under the test temperatures, the per-
centage dry weight was 27.8 at 100 F, 19.5 at 80 F, and
17.0 at 60 F in those plants receiving nitrogen. On the
same date, those receiving no nitrogen had a percentage dry
weight of 27.6 per cent at 100 F, 23.1 at 80 F, and 20.A at
60 F.

The chlorophyll content of leaf tissue has been
ascertained from the point of view that it might be a
limiting factor in the rate of photosynthesis and thus the
rate of assimilation. Both Meyer and Anderson (1A) and
Strain (22) indicated, however, that the chlorophyll con-

tent is seldom a limiting factor of photosynthetic rate.

The photosynthetic rate remains constant over a large range
in chlorophyll content. Gaastra (7) presented a curve of
efficiency of light energy conversion in relation to chloro-
phyll concentration per unit leaf area. At low concentra—
tions, efficiency increased with increasing chlorophyll
concentration, then reached a maximum value and became a
non-limiting factor. Leopold (12) also discussed the
usually weak quantitative influence of chlorophyll content
upon the rate of photosynthesis in the field.

The carbohydrate content of plant tissue has often
been studied from many different aspects and points of view
and with widely divergent questions being investigated.
Certainly, the carbohydrates play a key role in plant metab-
olism. They provide the major source of carbon skeletons
for both catabolic and anabolic reactions.

Brown (A) studied seasonal carbohydrate levels of
Kentucky bluegrass in the field. His observations showed
that carbohydrates were produced more rapidly than they were
used during the cool weather of early spring, the surplus
being stored in roots and rhizomes. During the summer
period, there was a net loss of carbohydrates from roots and
rhizomes. During the autumn period, carbohydrate storage
again took place.

Carbohydrate content of various portions of perennial
ryegrass was determined by Sullivan and Sprague (2A). They

found the major portion of carbohydrate was located in the

stubble with smaller amounts in leaves and roots. They also
followed the amount of carbohydrate in stubble and roots of
plants which were clipped and placed under four temperature
regimes during regrowth. At the end of a AO-day period,
plants grown at 80-90 F were stunted and had spindly dark
green leaves. They attributed this deleterious effect to
rapid dissipation of reserve carbohydrates, especially in
the roots.

When Harrison (9) placed Kentucky bluegrass under an
80 F temperature, he found the amount of leaf tissue pro—
duced between periodic harvests decreased with time. He
attributed this effect to exhaustion of reserve carbohydrate.

Beinhart (2) studied the growth of white clover

(Trifolium repens L.) at various temperatures in growth

 

chambers and seasonally in the field. He found that the
decline in summer branching of the stolons appeared to limit
the summer growth of white clover. He concluded, however,
that carbohydrate supply was not the limiting factor in
summer branching.

When Jordan (11) studied fructose content of creeping
bentgrass, he found that carbohydrate accumulation in leaf
clippings was an inverse function of their growth.

Green (8) found that temperatures of 80 F and greater
appeared to exert an adverse effect on the carbohydrate
reserves of the cool season grasses he studied. However,

he concluded that under the conditions of his study, the

total carbohydrate level of leaf tissue did not appear to
limit growth.

The question of the effect of temperature upon
translocation of sucrose in tomato was studied by Went
and Engelsberg (27). They found that rate of sugar trans-
location decreased as the temperature was increased from
8 to 26 C.

In a later paper, Went and Hull (28) reported that
carbohydrate transport through the stem of the San Jose
Canner tomato became essentially 0 near 30 C.

Swanson and Bohning (25) studied the influence of
petiole temperature upon the translocation of sucrose out
of the leaf of bean. They found maximum sucrose tranSport
took place between 20 C and 30 C. At petiole temperatures
of 5 C to 7.5 C the rate of transport was reduced as much
as 50 per cent. From A0 0 to A2 C, the tranSport rate was
reduced 100 per cent as compared to the controls.

Hewitt and Curtis (10) found translocation from bean
leaves increased when the plants were held for 13 hours at
A, 10, and 20 C. The rate at 30 C nearly equalled that at
20 C. At A0 C there was a marked decrease.

Rabinowitch (18) discussed temperature effects upon
the rate of photosynthesis. The rate of photosynthesis is
governed not only by temperature but also by light inten-
sity and carbon dioxide supply. When light intensity is

low, photosynthetic rate is generally insensitive to change

10

in temperature. Light controlled or photochemical processes
are temperature independent. Under conditions of high light
intensity and low carbon dioxide supply, the photosynthetic
rate is primarily influenced by the effect of temperature
upon the diffusion rate of carbon dioxide. When neither
carbon dioxide nor light is limiting, photosynthetic rate
increases rapidly in the temperature range near the lower
temperature limit. As the temperature is increased further,
the rate of increase with temperature decreases until an
Optimum is reached. Above the optimum, the rate declines
rapidly with further temperature increase. Higher plants
adapted to moderate climates generally reach the maximum
photosynthetic rate in the range of 30-35 C.

Consideration of the effect of temperature upon res—
piration shows a different relationship than that of photo-
synthesis (13, 18). The respiratory rate increases with
temperature at a rapid pace from temperatures slightly
above the minimum for respiration until an optimum is
reached. At temperature levels greater than the optimum,
the rate decreases rapidly. In many cases, the optimum
photosynthetic rate is at a lower temperature than the
optimum for respiration. As a result of these effects, a
region is reached at high temperatures where net gas
exchange becomes less than unity.

The effect of temperature upon the growth of two

strains of Chlorella was studied by Sorokin and Myers (20).

 

By culturing and selecting at various temperatures, they

11

were able to isolate a culture which had a higher optimum
for growth than the wild strain with which they started.
They found the Optimum for the latter was 25-26 C and for
the former it was 39 C.

Murata and Iyama (16) in their study of the photo-
synthetic rate of forage crops found that the season of
production of orchard grass influenced the photosynthetic
rate. Plants which were grown in July exhibited a greater
rate from 20 C through A0 C than those grown in March.

The relationship between carbohydrate levels and
plant growth as measured by dry weight production of leaves
at various temperatures is still in question. In some
studies(A,2® carbohydrate levels decreased as growth was
reduced and.temperature increased. This correlative rela-
tionship shows only that carbohydrate levels and dry weight
production vary in a similar manner. In other studies
(2, 11) the amount of above ground tissue produced at
above optimum temperatures could not be correlated with
carbohydrate levels. This result does not provide evidence
for the real cause of reduced growth, but the negative
relationship does provide evidence that carbohydrate levels
are not limiting leaf dry matter production.

Under turf conditions, grass plants are periodically
mown to maintain an attractive, uniform appearance. Due to
this practice, the leaf tissue present is in a state of

continuous turnover. Leaf tissue produced at various

12

temperature levels may not exhibit the same photosynthetic
activity (16).

This study was initiated with the goal of elucidating
some of the effects of supraoptimal temperatures upon leaf
dry matter production and carbohydrate levels in the leaf
tissue. In addition, photosynthetic and respiratory rates
of leaf tissue produced were determined to investigate the
possibility of changes in temperature response of leaves

grown at different temperatures.

MATERIALS AND METHODS

Sod pieces of Toronto creeping bentgrass 6.A5 square
decimeters in area were taken from the field in mid
September and placed in boxes 25.A X 25.A X 20.3 cm con-
taining a 2-1-1 mixture of soil-sand-peat. They were main-
tained in the greenhouse three weeks and then transferred
to the growth chamber where they were permitted to grow
an additional six weeks. This period was considered ade-
quate for the sod to become established and acclimated to
the growth chamber.

During establishment, each box received a weekly
application of one liter of Hoagland's number two macro-
nutrient solution made up with tap water. On the remaining
six days, tap water was added until drainage from the
bottom of.the boxes occurred.

Leaf growth was harvested at 8:00 AM once per week
at a cutting height of 1.3 cm, utilizing hand shears with
a pan attached to collect the clippings.

During establishment, the growth chamber was pro-
grammed for 20-10 C temperatures during 16-8 hour light-
dark cycles. Light was furnished by flourescent lamps
supplemented by incandescent bulbs. Intensity at the grass

surface was approximately 2,A00 foot candles as measured

13

1A

by a Weston illumination meter, Model 756, utilizing a
quartz filter.

Disease infestation was not observed at any time
during the course of the study. Insects were controlled by
occasional dusting with malathion.

Successive four-week periods were utilized, with
temperatures of 20-10, 25-15, 30-20, 35-25, and A0-30 C
during 16-8 hour light-dark periods. Experimental deter-
minations were made once per week at any one temperature
regime.

Once per week, the grass was clipped to a height Of
1.3 cm as previously described and the harvested material
frozen and stored at -18 C for future analysis. Leaf
harvests were made at the midpoint of the light period in
order to avoid diurnal variations in carbohydrate levels.
Fertilization and watering procedures and light intensity
were as outlined under establishment period.

Chlorophyll extractions of harvested leaf clippings
were carried out as given in Official Methods of Analysis,
AOAC (1). Approximately 200 mg fresh weight of leaf
tissue were macerated in a mortar with quartz sand. Chlo-
rophyll was extracted with 85 per cent acetone and the
residue filtered off with a Buchner funnel. The extract
was brought to 100 ml final volume and the Optical density
determined with a Beckman DU spectrophotometer at 660

millimicrons.

15

A second sample was weighed into glass weighing
bottles, dried at 85 C for 2A hours, reweighed, and the '
percentage dry matter determined so that chlorOphyll con-
tent could be calculated as percentage dry weight.

Smith and Grotelueschen (19) reported 85 per cent
ethanol effective in extracting glucose, fructose, and

sucrose from stem base tissue of Agrostis alba L. Their

 

extracts were checked by thin layer chromatography. Very
little fructose Oligosaccharide was removed with this
alcohol concentration. In the present investigation, 85
per cent ethanol was used to extract bentgrass tissue.
The carbohydrates thus extracted were considered to be
predominately glucose, fructose, and sucrose.

Tissue used for carbohydrate determinations was dried
at 85 C for three to four hours. It was then ground in a
mortar and returned to the oven for further drying. The
total drying time was 2A hours. Approximately 100 mg
dried tissue was placed in an 125 ml Erlenmeyer flask and
50 ml 85 per cent ethanol added. The flask was stoppered
and shaken for one hour. The sample was removed from the
shaker and a small amount of Norit-A added. The sample was
filtered through a Buchner funnel utilizing Celite filter
aid and the residue washed with additional 85 per cent
ethanol. The ethanol was removed in a rotary flash evap-
orator, at 65 C and the aqueous solution rinsed into an

100 ml volumetric flask with distilled water and brought

16

to volume. A second sample Of approximately 100 mg was
extracted with distilled water at room temperature. Similar
procedures to the above were used except that the extract
was brought to 200 m1 final volume without reduction in the
flash evaporator.

Colorimetric determination of the carbohydrate con-
tained in the two extracts was carried out according to the
anthrone method of Yemm and Willis (29). Concentrated
sulfuric acid was diluted by adding A0 ml distilled water
to 100 ml acid.. The anthrone reagent was made by dissolving
0.2 gram anthrone in 100 ml of the sulfuric acid prepared
as above. Fresh reagent was prepared and used each day
carbohydrate determinations were made. The reaction was
carried out by placing 5 ml anthrone reagent in matched
Pyrex test tubes in an ice bath and allowing it to cool for
at least 5 minutes. One m1 of extract was pipetted on top
of the anthrone solution. The solutions were mixed and
again cooled 5 minutes. Color was developed in a boiling
water bath for 10 minutes and the test tubes returned to
the ice bath for a 5-minute cooling period. Optical den-
sity was read with a Coleman Junior spectrophotometer at
620 millimicrons, and the carbohydrate content determined
by reference to a standard curve. Duplicate determinations
of each extract were made. Duplicate standards of 10, 20,
A0, and 60 micrograms fructose were also run each time in
order to be certain the reaction remained on the standard

curve .

17

On the same day harvests were made, one box was removed
from the growth chamber and taken to the laboratory. Photo-
synthetic and respiratory rate determinations were made at
the temperature of the light period under which the plants
were grown.

Photosynthetic rate determinations were made by
standard Warburg manometric techniques (26). The last fully
unrolled leaf was excised from individual plants. Then
leaves were arranged in the center well of a flask contain-
ing 0.1 ml distilled water. Three m1 of buffer was placed
in the flask outside the center well to serve as a source
of carbon dioxide during the experimental run. The buffer
was made by adding 6.72 grams sodium bicarbonate to 100 ml
saturated sodium borate solution. Calculated atmospheric
carbon dioxide concentration within the flasks was 15 per
cent. Light intensity measurements showed 3,200 foot
candles transmitted through the bottom Of the Warburg
apparatus as measured with a Weston illumination meter,
model 756 utilizing a quartz filter.

Four flasks containing leaves plus two checks were
used for each run. All flasks were placed in the water
bath and allowed to equilibrate 20 minutes. The manometers
were then brought to the reference point and closed off.
Readings were taken at 15—minute intervals over a two-hour

period.

18

At the end of the run, flasks were removed from the
manometers and.leaf area of the tissue determined by measur-
ing the length and midpoint width of all leaves used.
Leaves were then placed in glass weighing bottles, dried at
85 C for 2A hours and weighed.

Preliminary determinations showed no difference be-
tween the photosynthetic rate at 3,200 foot candles and
2,600 foot candles light intensity (Appendix Table XVII).
The system was considered to be at light saturation at
3,200 foot candles. Preliminary determinations of the
effect of the calculated carbon dioxide level were also
made (Appendix Table XVIII). Carbon dioxide supply was not
considered to be limiting in the photosynthetic rate deter-
minations with the.buffer system used.

Respiratory rates were also determined in the Warburg
apparatus. .Light was excluded by a black velvet cloth
draped over the top and fitted over the bottom Of the
apparatus. Twenty-five leaves similar to those used in the
photosynthetic.rate determination were excised and placed
in the Warburg flask. Two-tenths ml of 10 per cent potas-
sium hydroxide were placed in the center well. A 2 cm X
2 cm piece of filter paper was folded and placed in the
center well to increase absorption area. Determinations
were made in a manner similar to that described above and
the tissue dried and weighed.

Statistical analyses were carried out according to

methods outlined in Steele and Torrie (21).

RESULTS

The bentgrass grew quite vigorously under the 20-10 C
temperature regime. Leaf tissue was a good, green color
and new leaves were produced rapidly. One week after clip—
ping, the leaves were beginning to bend toward an horizontal
orientation. The turf was dense and was similar to the kind
of growth observed in the field in late spring and early
summer.

Very few visual differences were noted between grass
grown at 25-15 C and that produced at 20-10 C. The plants
appeared quite healthy and the turf vigorous.

Under the 30-20 C temperature regime, the grass did
not appear to be adversely affected. The plants were vig-
orous and the turf dense with no visible evidence of thin-
ning. Color did not appear different from that of the
lower temperatures.

Beginning with the 35-25 C temperature level, a
striking difference in growth Of the turf was noted. Leaves
were much more upright in growth habit and did not bend
towards the horizontal. They had a bristle-like appearance
when harvested. NO distinct color differences could be

seen when compared with leaves grown at the lower tempera-

tures.

l9

20

Soon after the plants were placed under the 35—25 C
temperature treatment, the stand Of plants appeared to de-
crease in density. After the initial period, no further
apparent thinning took place.

Growth habit of plants at the A0-30 C temperature
regime assumed a distinctly upright, bristle-like appear-
ance. Leaves produced at this temperature appeared to have
a darker green color than those produced at lower tempera-
tures.

Turf density definitely decreased at the highest
temperature level. The effect was noted in all boxes in
the growth chamber. Some plants died, but no definite
positional pattern could be noted in any of the boxes.

The plants were kept at the A0-30 C level for four weeks

as they were for the previous temperature treatments. At
the end of this period, all but two boxes were discarded.
The two remaining boxes were placed under a 20-10 C temper-
ature regime and watered, fertilized and clipped as before.
At the end of two weeks, the surviving plants appeared
healthy, but the turf did not fill in and became dense until
an additional two-week period had passed.

The width of leaves produced at five temperature
levels is presented in Table l. The data presented are from
measurements taken when leaf area was determined during the
photosynthetic rate studies. Essentially equal numbers of

leaves produced at 20-10 and 25-15 C were in the 1.0-1.5 mm

21

and >1.5 mm width classes. When temperature was increased
to the 30-20 C level, there was a distinct decrease in leaf
width. None of the leaves measured were more than 1.5 mm
wide. The width of leaves grown at 35-25 C was quite simi-
lar to that of leaves grown at 30-20 C. Leaves grown at
A0-30 C were distinctly narrower than those produced at any
other temperature regime. 6

Leaf length at five temperature regimes is presented

in Table 2.

TABLE l.--The number of leaves out of 160 falling in three
width classes when grown at five temperature regimes.

Leaf Width Class, mm

 

 

Temperature
Regime Grown
<l.0 1.0-1.5 >1.5

20-10 C 0 1AA 16
25-15 C 0 1A2 18
30-20 C 58 102 '0
35-25 C 60 100 0
A0-30 C 130 30 0

n

 

TABLE 2.--The number of leaves out of 160 falling in four
length classes when grown at five temperature regimes.

 

Leaf Length Class, mm

 

 

Temperature
Regime Grown ‘

6-10 11-15 16120 21-25
20-10 C 0 6 78 76
25-15 C 0 A 88 68
30-20 C 0 3 79 78
35-25 C 0 58 102 0
A0—30 C 62 98 0 0

 

22

As in the case of leaf width, there was essentially
no change in leaf length between 20-10 and 25-15 C. Nearly
equal numbers of leaves fell in the three longer length
classes at the three lower temperature regimes. Increasing
the temperature to 35-25 C resulted in shorter leaves than
were produced at lower temperatures. There was a large
reduction in leaf length at the A0-30 C temperature level.

Percentage dry weight increased gradually from the
20-10 to the 30-20 C temperature level, then increased more
sharply between the 30-20 and 35-250 regimes (Table 3). A
very definite increase in percentage dry weight was found
when temperature was increased from 35—25 to A0-30 C.
Percentage dry weight increased AA per cent between the two
levels. Although there was an increasing trend in percent-
age dry weight at the higher temperatures, Duncan's test
of the means showed the sharp increase at the highest tem-
perature to be the only one significantly different at the
l per cent level. The average percentage dry weight for the
four lower temperature levels was 22.1 per cent. Dry weight
percentage of the leaf tissue grown at A0—30 C was 3A.A per
cent, an increase of 61 per cent.

Weight per unit area of the leaf tissue increased
from the lowest temperature regime to the highest (Table A).
Although Duncan's range test showed that not all means were
significantly different, analysis of the treatment sums of

squares showed that the portion due to linearity was highly

23
significant and deviation from linearity was nonsignificant

(Appendix Table VI).

TABLE 3.--Percentage dry weight of leaf tissue produced
~under five temperature regimes.

 

 

Percentage Duncan's Test
Temperature Regime Dry Weight of Means“
20-10 C 20.6 a
25-15 C 21.6 a
30-20 C 22.A a
35-25 C 23.9 a
A0-30 C 3A.A b

 

*

Means containing the same letter in the third
column are not significantly different at the l per cent
level.

TABLE A.--Milligrams dry weight per square centimeter of
leaf area produced under five temperature regimes.

 

 

Temperature Milligrams Dry Weight Duncan's *
Regime Grown per Square Centimeter Test of Means
25—15 C 2.1 b
30-20 C 2.1 b
35-25 C 2.A bc
A0-30 C 2.6 c

*

Means containing the same letter in the third
column are not significantly different at the l per cent
level.

There was a gradual decrease in dry matter production

from the 20-10 to the 30-20 C temperature level (Table 5).

2A

TABLE 5.--Dry weight of clippings, grams per 25.8 square
decimeters per week at five temperature regimes.

 

 

Temperature Duncan's *
Regime Grown Clipping Yield Test of Means
20-10 C l3.A a
25-15 C 12.9 a
30—20 C ll.A a
35-25 C 8.A b
A0-30 C 3.1 c

 

*
Means containing the same letter in the third
column are not significantly different at the l per cent
level.

When the results were subjected to Duncan's multiple range
test, however, the decrease was nonsignificant at the l
per cent level. When the temperature was increased to
35-25 C, weekly dry matter production of new leaf tissue
was reduced significantly. The average value for dry
weight of clippings for the three lowest temperature regimes
was 12.6 grams, and that of the 35-25 C regime was 8.A
grams, a decrease of 33 per cent. Comparison Of the dry
matter produced among the first three temperature levels
versus the A0-30 C regime shows a decrease of 75 per cent
in new leaf production. When temperature was increased
from 35-25 to A0-30 C, leaf dry matter production was de-
creased 6A per cent.

Chlorophyll content per mg dry weight of harvested
leaf tissue showed a general increase from the 20-10 C

temperature regime to the 25-15 C level (Table 6).

- 25

TABLE 6.—-Chlorophyll content of leaf clippings, micrograms
per milligram dry‘weight at five temperature regimes.

 

 

 

Temperature Chlorophyll, Micrograms Duncan's *
Regime Grown per Milligram Dry Weight Test Of Means
20-10 C 8.7 a

25-15 C 9.3 ab
30-20 C 10.3 b

35-25 C 10.A b

A0-30 C 6.7 c

s

, Means containing the same.letter in the third
column are not significantly different at the l per cent
level. ‘

The amount of chlorophyll decreased markedly in the tissue
produced at A0-30 C. When the means of chlorophyll content
were subjected to Duncan's range test, the content at the
20-10 C regime was significantly less than that at 30-20
and 35-25 C. The amount present in the A0-30 C grown
tissue was significantly less than that present in tissue
produced at any of the other temperatures. The quantity
present at the intermediate temperatures, although showing
a slight increase, was not significantly different.

The Observation that leaves produced at the highest
temperatures appeared to be a dark green color did not
agree with the decrease in chlorophyll content found on a
weight basis. Chlorophyll content per unit area was then
calculated from the dry weight per unit area and chloro-
phyll per unit weight data (Table 7). The marked decrease

in chlorophyll content shown on a dry weight basis at the

26

highest temperature level was not found when the content was
changed to an area basis. There was a slight decrease, but
the amount present on this basis was still greater than that
found at the lowest temperature regime.

The amount of 85 per cent ethanol soluble carbohydrate
in the leaf tissue was very similar at all temperature

regimes from 20-10 to 35-25 C (Table 8). Duncan's Test of

TABLE 7.--Chlorophyll content, micrograms per square centi-
meter Of leaf area at five temperature regimes.

 

 

Temperature Chlorophyll Content,
Regime Grown Micrograms per Square cm
20-10 C 15.0

25-15 C 20.A

30-20 C 22.5

35-25 C 25.1

A0-30 C 17.9

 

TABLE 8.--85 per cent ethanol soluble carbohydrate content
of leaf tissue produced under five temperature regimes:
percentage of dry weight of tissue.

 

 

Temperature Percentage Duncan's
Regime Grown Carbohydrate Test of Means*
20-10 C 5.2 a
25-15 C 5.2 a
30-20 C 5.1 a
35-25 C 5.7 a
A0-30 C 8.1 b

 

*

Means containing the same letter in the third
column are not significantly different at the l per cent
level.

27

the treatment means showed the differences to be nonsignifi- ‘
cant at the l per cent level. The average content of leaves
produced at the four lower temperature regimes was 5.3 per
cent of the dry weight. The A0-30 C grown leaf tissue con-
tained 8.1 per cent on the same basis, an increase of 53

per cent.

The water soluble carbohydrate content showed a
response similar to the 85 per cent ethanol soluble fraction
(Table 9). A significant increase in water soluble carbo-
hydrate content was found in leaf tissue produced at A0-30 C.
The average water soluble carbohydrate content of tissue
produced under the four lower temperature regimes was 6.5
per cent of the dry weight. Leaves grown at A0-30 C con-
tained 9.8 per cent, an increase of 51 per cent.

In addition to leaf carbohydrate determinations, the
amount present in stem and stolon tissue was ascertained
for the lowest and highest temperature regimes (Table 10).
Carbohydrate analyses were made on distinctly different
appearing plants at the A0-30 C level. In one instance,
plants which retained a green leaf color were used, but in
the second, chlorotic plants were selected.

The amount of water soluble carbohydrate found in the
stem and stolon tissue grown at 20—10 C was somewhat lower
than the average value found in leaf tissue of plants grown
under the same temperature regime. As previously stated,
however, the water soluble content was found to be quite

variable and the content found in the stem and stolon

28

tissue was within the range Of values previously determined

for bentgrass leaf tissue.

TABLE 9.--Water soluble carbohydrate content of leaf tissue
produced under five temperature regimes: percentage of dry
weight of tissue.

 

Temperature Percentage Duncan's

 

Regime Grown Carbohydrate Test of Means*
20-10 C 6.1 ab
25-15 C 6.3 ab
30-20 C 5.7 a

35-25 C 7.8 b

A0-30 C 9.8 c

 

*Means containing the same letter in the third
column are not significantly different at the l per cent
level.

TABLE 10.—-Water soluble carbohydrate content of stem and
stolon tissue, per cent of the dry weight.

 

 

Temperature Visual Plant Per Cent Water
Regime Grown Appearance Soluble Carbohydrate
20-10 C Green 5.2

A0-30 C Green 10.7

A0-30 C Chlorotic 11.9

 

The water soluble carbohydrate content of stem and
stolon tissue of green plants grown at the A0-30 C temper-
ature regime was somewhat higher than in leaf tissue of

plants grown at this temperature level. Again, however,

29

the values determined were within the range of those deter-
mined for leaf tissue.

In the chlorotic plants, the water soluble carbohy-'
drate content of stem and stolon tissue was greater than
that found in leaf tissue. The values in this case were
all greater than any value found for green plants when
water soluble carbohydrate content of leaf tissue was
determined.

Cumulative 02 and CO2 production of leaf tissue grown
at 20-10, 30-20 and A0-30 C and tested at the light temper-
ature is presented in Figures 1 and 2. The figures pre-
sented show how tissue produced under the three temperature
regimes reacted when tested at the temperature under which
they were grown. As has been shown, tissue produced under
various temperature regimes was not equivalent. The
figures presented do not represent the change in photo-
synthetic rate per unit area Of any one tissue over a range
of temperatures. The usual Q10 relationship used to compare
photosynthetic rates of tissue at different temperature
levels is not a valid mode of comparison in this case. The
photosynthetic and respiratory rates per unit area of leaf
tissue grown at the indicated temperatures and tested in
the Warburg apparatus at the light period temperature are
represented. Neither photosynthetic nor respiratory mea-
surements made in the highly artificial environment of the

Warburg apparatus represent how the tissue was capable of

3O

 

 

E; 200.

p A0 0
8

U 30 C
8

m 20 C
Q1100~

O

m

> 0

0H

4.)

m

H

E."

o 0 60 120

Time, Minutes

Figure l.--Cumulative 02 Production of Leaves Grown and
Tested at the Indicated Temperatures. Microliters per
Square Centimeter.

 

 

C

o

-H

4.)

O

s 204 A0 C
p

0

£4

a.

N O C
o .3

O O

m 10* '

>

-H

‘5

_, 20 C
3

E

3

L)

O.
0 60 120

Time, Minutes

Figure 2.--Cumulative CO Production of Leaves Grown and
Tested at the Indicated Temperatures. Microliters per
Square Centimeter.

31

reacting to the conditions extant in the growth chamber.
The data are presented and must be interpreted within they
framework of these restrictions.

Photosynthetic rates of tissue grown and tested at
the temperature levels indicated ranked as A0>30>20 C.
Respiratory rates ranked in the same order. Rates of
tissue grown and tested at the highest temperature level
continued to be greater than those Of tissue grown and
tested at lower temperatures.

It has been pointed out that leaf tissue grown at the
various temperature regimes was continuously changing as
the temperature levels increased. SO that the results of
the previous study could be interpreted, the photosynthetic
rates-per unit area of tissue grown at 20-10 and A0-30 C
were determined at 20, 30 and A0 C as a control experiment
(Table 11). The ranking of activity was 30>A0>20 C in
- tissue grown at both 20-10 and A0-30 C. The photosynthetic
rates of tissue produced at the two temperature levels were
also significantly different when they were tested at the
same temperature.

In order to compare the response of photosynthetic
activity to temperature in leaves produced at the two
temperature regimes, the rates were placed on a relative
basis. The means of the rates at 20 C were assigned the
value 1.0 and rates at 30 and A0 C are shown relative to

this base rate (Table 12). The relative rates were the

32

TABLE ll.--Photosynthetic rate of leaf tissue grown at 20-10
and A0-30 C and tested at the indicated temperatures: micro-
' liters per square centimeter per hour.

 

Test Temperature

 

 

Temperature
Regime Grown

20 C 30 C A0 C
20-10 C 55.3 80.9 61.0
AO-3O C 68.1 95.2 88.5
t Test Value* 5.297** 3.808** A.792**

 

*Value of t test for significance between means at
the indicated temperatures.

TABLE l2.--Relative photosynthetic rate per unit area of
leaves grown at 20—10 and A0-30 C and tested at the indi—
cated temperatures.

 

Test Temperature

 

 

Temperature
Regime Grown
20 C 30 C A0 C
20-10 C 1.00 l.A6 1.10
A0-30 C 1.00 l.AO 1.30
* s
t Test Value 1.003 2.1A3

 

*
Value of t test for significance between means at
the indicated temperatures.

same at 30 C in both tissues. At A0 C, however, the rela-
tive rate of leaf tissue grown at A0-30 C was greater than

that of tissue grown at 20-10 C.

33

The respiratory rates per unit area of leaf tissue
grown at 20-10 and A0-30 C were also determined at 20, 30
and A0 C (Table 13). The ranking of activity was A0>30>20
as was found in the initial test when leaf tissue was
tested at the light period temperature under which the
plants were grown. In contrast to the photosynthetic
rate, no difference was found between tissue grown at the
two temperature regimes when tested at the same temperature.

The effects Of increasing the temperature level were
manifested within one week upon leaf dry matter production
(Appendix Table I) and percentage dry weight (Appendix
Table III). The effects were not time dependent through
the course of the four-week period the plants were held
under a given temperature regime. The same time response
was found for dry weight per square centimeter, chlorOphyll
content, and water soluble carbohydrate content (Appendix
Tables V, VII, IX and XI respectively).
TABLE l3.-—Respiratory rate of leaf tissue grown at 20-10

and A0-30 C and tested at the indicated temperatures:
microliters per square centimeter per hour.

 

Test Temperature

 

 

Temperature
Regime Grown
20 C 30 C A0 C
A0-30 C 3.0 6.7 9.8
x
t Test Value 1.007 0.615 0.76A

 

*Value of t test for significance between means at
the indicated temperatures.

DISCUSSION OF RESULTS

Growth of an autotrophic green plant such as creeping
bentgrass entails a catenary series of processes. In order
for the end product, dry weight, to accumulate, all must be
capable Of reaching a delicate balance within the living
system. Stress upon the system may effect one, a few, or
many Of the processes involved. The final effect may well
be the same, whether few or many are affected. All are
inter-dependent and reduction of the rate of any single
process may conceivably reduce the amount of product formed.

Production Of leaf dry matter in this study followed
the same general type of pattern as previously reported for
cool season grasses (3, 5, 9, 23). More new leaf tissue
was produced at the 20-10 C temperature regime than at any
of the others studied. A gradual decrease was found from
the 20-10 C level to the 30-20 C. When the temperature was
raised further, a precipitous decrease in dry matter pro-
duction took place. At A0—30 0, very little new leaf
growth was produced between harvests.

Change in leaf dry matter production can come about
through modification of leaf area and leaf dry weight per
unit area. Leaf area Of a grass is a function of leaf

width or length or a combination of both.

3A

35

In this study, leaf width was found to decrease as
temperature increased from 20—10 to 30—20 C. Leaf length,
however, changed very little. Dry weight per unit area
increased between these temperature regimes. A small de-
crease in leaf dry matter production resulted. The decrease
in leaf width was to some extent offset by the increased
weight per unit area.

At the higher temperatures both leaf width and leaf
length decreased markedly. Dry weight per unit area con-
tinued.to increase. The resultant was a highly significant
decrease in dry matter production at 35—25 and A0-30 C.
.The.precipitous decrease in leaf area produced overshadowed
the upward trend in dry weight per unit area. Change in
.leaf length, width, and dry weight per unit area have a
multiplicative effect upon the dry weight of leaf tissue
produced.

Change in leaf width had its greatest influence in
decreasing dry matter production at the lower temperature
regimes.. Conversely, a small decrease in leaf width
coupled with a large decrease in leaf length plus reduction
of turf density resulted in reduced dry matter production
at the highest temperatures.

The turf as a whole was much less vigorous at higher
temperatures. Such turf in the field would be less resis-
tant to disease and insect attack or weed encroachment,

and would be less able to recover from damage caused by

36

use of the turf. The less vigorous plants would have a
reduced ability to recover from or resist stress placed
upon them by another factor of the environment whether
natural or mechanical.

On a dry weight basis, chlorophyll content decreased
sharply at the A0-30 0 temperature level. However, per-
centage dry weight increased sharply, thus confounding the
chlorophyll determination. Visual observation of the
tissue produced, however, indicated that leaves at the
highest temperature appeared to retain their green colora-
tion. The amount of chlorophyll per square centimeter of
leaf area was then calculated. On this basis, the large
decrease in chlorOphyll content was not present as it was
on a weight basis. On an area basis, there was more chloro-
phyll present at the A0-30 C than at the 20-10 C level.
The large decrease in chlorophyll content per milligram
dry weight was probably more apparent than real because of
other changes which were taking place in the tissue at the
highest temperature regime. On either basis, the produc-
tion of leaf dry matter could not be equated with chloro-
phyll content of the leaf tissue.

Carbohydrate production is the resultant of a series
of reactions which must take place in sequential order.
Not only must photosynthetic carbon reduction take place,
but the product must be transported from the site of

synthesis to the non—photosynthetic portions of the plant

37

which are dependent upon the green portions for a supply
Of respiratory substrate. If the supply Of carbohydrate
becomes depleted, the autotrophic plant will exhibit a
decreased growth rate because of the decreased supply of
respiratory carbon skeleton.

Carbohydrate levels within the leaf tissue Of the
creeping bentgrass of this study varied very little from
the 20—10 to the 30-20 C level. Production of leaf tissue
decreased slightly between these regimes, but the trend
was statistically nonsignificant at the l per cent level.

Dry matter production was significantly reduced at
the 35-25 C temperature regime. The amount of 85 per cent
ethanol soluble carbohydrate, increased slightly as did the
amount of water soluble carbohydrate.

At the highest temperature, there was a highly signifi-
cant decrease in leaf tissue production and a highly signifi-
cant increase in 85 per cent ethanol soluble carbohydrate
content, water soluble carbohydrate content, and percentage
dry weight of harvested leaf tissue. The amount of water
soluble carbohydrate increased 51 per cent at A0-30 C com-
pared to the mean of that found at the lower temperature
regimes. On the same basis, percentage dry weight increased
61 per cent. The increase in percentage dry weight was
largely accounted for by increase in carbohydrate content.
None of the other components of the dry weight were deter-
mined, therefore, the data do not show what made up the re—

mainder of the dry weight not accounted for by carbohydrate.

38

The finding that carbohydrate content of leaf tissue
increased at the highest temperature prompted investigation
of the content in lower leaf sheath, stem, and stolon. The
cause of the increased leaf carbohydrate content could
have been a breakdown in translocation of material from the
leaf to lower portions of the plant. This investigation
showed that the amount of water soluble carbohydrate in
tissues of the lower portion of green plants was of the
same order of.magnitude as that found in the leaves. This
finding was interpreted as showing that translocation of
carbohydrate from leaves to lower portions of the plant was
not disrupted.

The amount of water soluble carbohydrate present in
the lower portion of plants which were becoming visibly
chlorotic at the highest temperature was also investigated.
Although these plants were visibly harmed in that they were
not actively growing and were turning yellow, the amount of
water soluble carbohydrate present was Of the same order of
magnitude as that found in green plants at the same tempera-
ture.

At no temperature regime could the amount of carbo-
hydrate present be directly equated with dry matter produc-
tion of new leaf tissue. Rather, the two were inversely
related. When leaf dry matter production was at its
greatest, carbohydrate content of both leaf and lower por-

tions of the plant was at its lowest. Conversely, when

 

 

llllill.lll|lllli
I‘ll-ll

39

leaf dry matter production was at its ebb, carbohydrate
content was at its peak.

Photosynthetic rates were determined manometrically.
Photosynthetic oxygen production was evaluated in an
environment where neither carbon dioxide nor light limited
activity. Under these conditions, the temperature depend-
ent, nonphotochemical reactions of photosynthesis were
evaluated.

The photosynthetic rate per unit area of leaves grown
at 20-10, 25-15 and A0-30 C was determined at the light
period temperature. The results of this study indicated a
steadily increasing rate per unit area from the lowest
temperature to the highest. However, this result con-
flicted with the results of other investigators who have
reported the effect of this temperature level on the photo-
synthetic rate of grasses. In their-studies, Murata and
Iyama (16) found a reduction of photosynthetic rate at A0 C,
as did Miller (15). It has been shown in the previous dis-
cussion that numerous changes were taking place in the leaf
tissue produced as the temperature was increased. This
evidence indicated that changes were taking place which
made the base, leaf area, a significant variable due to
qualitative and/or quantitative changes within the leaf as
temperature increased. The photosynthetic activity of
leaves produced at 20-10 and A0-30 C was determined at 20,

30 and A0 C as a control experiment to elucidate the

A0

steadily increasing photosynthetic rate found in the pre-
vious study. Leaves grown at A0-30 C exhibited a greater
photosynthetic rate per unit area than those grown at 20-
10 C when both tissues were tested at 20, 30 and A0 C.
This effect may have been caused by morphological changes
within the leaf tissue produced at the two temperature
regimes. One possible change is indicated indirectly by
the observed change in leaf size as temperature was in-
creased. Each cell produced at A0-30 C, although physi-
cally smaller than those produced at 20—10 C, would be
expected to retain a certain level of autonomy. A greater
number of the smaller cells would be present per unit leaf
area. Because of the greater number of cells per unit
area, there may have been a quantitatively greater concen-
tration of photosynthetically active units per unit leaf
area. This larger number of phyotsynthetic units per unit
leaf area would be capable of exhibiting a greater photo-
synthetic rate per unit area Of leaf even if the rate per
photosynthetic unit was the same in both tissues. El-
Sharkawy and Hesketh (6) noted that there seemed to be an
inverse relationship between cellular diameter and photo—
synthetic rate. They suggested that the reason for the
relationship observed was due to a surface to volume factor.
In order to compare the response of photosynthetic
activity to temperature in leaf tissue grown at 30-20 and

A0-30 C, the Observed rates were placed on a relative basis.

Al

The relative photosynthetic rate of leaf tissue grown at
the two temperatures was quite similar at 30 C compared to
20 C. The Q10 of both tissues was essentially the same
between 20 and 30 C. In both tissues, the relative rate
at A0 C was less than that at 30 C, therefore the Q10
between 30 and A0 0 was less than unity in both. At A0 C,
the relative rate of leaf tissue grown at A0—30 C was
greater than that of tissue grown at 20-10 C. The depres-

sion in Q1 value of leaf tissue grown at A0-30 C was less

0
than the depression in leaves grown at 20-10 C. This dif-
ference in the depression of Q10 between 30 and A0 C is a
qualitative difference in the leaf tissue grown at the two
temperatures.

These results indicate that adaptive mechanisms of
both a quantitative and qualitative nature played a role in
influencing the photosynthetic activity per unit area of
leaves grown at the various temperature levels. These pos-
tulated adaptive mechanisms affected the results Observed
in the initial study. The steadily rising photosynthetic
rate per unit area of leaf was occasioned by continuous
changes within the leaf leading to different photosynthetic
capability per unit area of leaves grown at the various
temperature levels.

Similar effects of the influence of the temperature

under which the leaf tissue was produced was not evidenced

for the respiratory rate. The respiratory rate was still

A2

increasing at the highest temperature in all tissues tested.
The rate per unit area of leaves grown at 20-10 and A0-30 C
was essentially equal.

Adaptive mechanisms affecting the photosynthetic rate
per unit area were indicated in this study. The total
amount of net photosynthesis is a function of both the
photosynthetic rate per unit area and the amount Of leaf
area present. The amount Of leaf area produced at the
higher temperatures was much less than that produced at the
lower temperatures. The total amount of photosynthesis
and thereby growth would be much lower at the high tempera—
ture regime.

If only the effects measured in this study affected
the growth of bentgrass plants at high temperature, the
plants might be eXpected to survive quite well. The plants
might be much smaller, but photosynthetic capability and
carbohydrate levels were adequate. The diametrically
opposite result was Observed. When the temperature was in-
creased to the A0-30 C level, the turf became thinner in
stand due to death Of plants. The results of this study do
not provide evidence for the cause of plant death at the

A0-30 C level.

SUMMARY

Some effects of above Optimum temperatures upon the
growth of creeping bentgrass were investigated.

The amount of dry matter produced as measured by
weekly harvests of leaf tissue decreased slightly from the
20—10 C regime through the 25-15 and 30-20 C. When the
temperature was increased further to 35-25 C, a sharp de—
crease in dry matter production took place. At A0-30 C,
very little new leaf tissue was produced between harvests.

Reduction in dry matter production came about through
the action of three separate effects, leaf length, leaf
width, and leaf weight per unit area. Decrease in leaf
width was the most important at the lower temperature
regimes. The effect was nearly countered by increased leaf
dry weight per unit area. At the higher temperatures of
35-25 and A0-30 C there was a precipitous decrease in leaf
length. Dry weight per unit area continued to increase at
these temperatures but was overshadowed by the large
decrease in leaf length.

The dry weight percentage of leaf tissue increased
slightly as temperature was increased above 20-10 C until at
A0-30 C a large and highly significant increase took place.

Dry weight per unit area trended upward linearly from

the lowest temperature to the highest.

A3

AA

The amount of 85 per cent ethanol soluble carbohydrate
and water soluble carbohydrate remained essentially the same
at 20-10, 25-15 and 30-20 C. A slight increase was noted in
both fractions at 35-25 C. A highly significant increase
was found in both carbohydrate fractions at A0-30 C.

The content of water soluble carbohydrate present in
leaf sheath, stem and stolon tissue was on the same order
of magnitude as that found in leaf tissue grown at the same
temperature.

When leaves grown at 20-10, 30-20 and A0—30 C were
tested for cumulative O2 and CO2 production in the Warburg
apparatus at the light period temperatures under which they
were grown, activity ranked as A0>30>20 for both.

When leaves grown at 20-10 C were tested at 20, 30 and
A0 C, the ranking was 30>A0>20 for photosynthetic rate and
A0>30>20 for respiratory rate. Leaves grown at A0-30 0
exhibited the same ranking of activity.

Comparison of relative photosynthetic rates of leaves
grown at 20-10 C with those produced at A0-30 C and tested
at 20,30 and A0 C indicated that quantitative and qualita—
tive changes were taking place within the leaf tissue.

These changes indicated that adaptive mechanisms influenced
the photosynthetic rate per unit area in leaf tissue grown
at the highest temperature level.

Although ample carbohydrate was found in leaf tissue

grown at the highest temperature, and adaptive mechanisms

A5

for photosynthetic rate per unit area were indicated, plants
died at the highest temperature. The effects measured in

this study did not account for their death.

CONCLUSIONS

The following conclusions were drawn from the results

of the study.

1.

Decrease in leaf dry matter production was
dependent upon decrease in leaf width and leaf
length. Leaf width was more important at the
lower temperatures. Leaf length was more
important at the higher temperatures.

Decrease in leaf dry matter production could
not be equated with a change in chlorophyll
content of the leaf tissue on either a dry
weight or area basis.

Diminished leaf dry matter production could
not be equated with leaf content of either

85 per cent ethanol or water soluble carbo-
hydrate.

Indreased carbohydrate content of leaf tissue
at A0-30 C could not be accounted for by dis-
ruption of transport out of the leaf into
lower portions of the plant.

Reduction of turf density at A0-30 C could not
be attributed to depleted carbohydrate reserves

in chlorotic appearing plants.

A6

A7

Morphological changes within the tissue of
leaves grown at A0—30 C resulted in a
quantitative increase in the photosynthetic
rate per unit area compared to leaves grown
at 20-10 C.

Uncharacterized qualitative changes in the
leaf tissue grown at A0—30 C resulted in a
smaller depression of Q10 of photosynthetic
rate per unit area at A0 C than in leaves
grown at 20-10 C.

The results of this study do not provide
evidence for the cause Of death of plants at
A0-30 C. Metabolic derangements not investigated
resulted in plant death and a thinner turf at

this temperature level.

LITERATURE CITED

10.

LITERATURE CITED

Association Of Official Agricultural Chemists. 1955.
Methods of Analysis. Eighth Edition.

Beinhart, G. 1963. Effects of Environment on Meri-
stematic Development, Leaf Area, and Growth of White
Clover. Crop Science 3:209-213.

Brown, E. M. 1939. Some Effects of Temperature on the
Growth and Chemical Composition of Certain Pasture
Grasses. Missouri Agricultural Experiment Station
Research Bulletin 299.

Brown, E. M. l9A3. Seasonal Variations in the Growth
and Chemical Composition of Kentucky Bluegrass. Missouri
Agricultural Experiment Station Research Bulletin 360.

Darrow, R. A. 1939. Effects of Soil Temperature, pH
and Nitrogen Nutrition on the Development of Poa
pratensis. Botanical Gazette 101:109-127.

 

El—Sharkawy, M. and Hesketh, J. 1965. Photosynthesis
Among Species in Relation to Characteristics of Leaf
Anatomy and CO2 Diffusion Resistances. Crop Science 5:
517-521.

Gaastra, P. 1962. Climatic Control of Photosynthesis
and Respiration. In Environmental Control of Plant
Growth. Edited by L. T. Evans. Academic Press, New York.

Green, D. G. 1963. Seasonal Responses of Soluble
Carbohydrates in the Leaves of Four Cool-Season Grasses
to Five Nitrogen Treatments. MS Thesis, Michigan

State University.

Harrison, C. M. 193A. Responses of Kentucky Bluegrass
to Variations in Temperature, Light, Cutting and
Fertilizing. Plant Physiology 9:83-106.

Hewitt, S. P. and Curtis, 0. F. 19A8. The Effect Of
Temperature on Loss of Dry Matter and Carbohydrate

from Leaves by Respiration and Translocation. American
Journal of Botany 35:7A6-755.

A9

11.

12.

13.

1A.

15.

l6.

17.

18.

19.

20.

21.

22.

23.

50

Jordan, E. E. 1959. The Effect Of Environmental
Factors on the Carbohydrate and Nutrient Levels of
Creeping Bentgrass, (Agrostis palustris). MS Thesis,
Purdue University.

 

Leopold, C. A. 196A. Plant Growth and Development.
McGraw Hill, New York.

Lundergardh, H. 1931. Environment and Plant Develop-
ment. A Translation of Klima und Boden und Ihrer
Wirkung auf des Pflanzenleben. Ashby, E. Edward
Arnold and Company.

Meyer, B. S. and Anderson, D. B. 1952. Plant
Physiology. Second Edition. D Van Nostrand Company,
Princeton, New Jersey.

Miller, V. J. 1960. Temperature Effect on the Rate

of Apparent Photosynthesis of Seaside Bent and Bermuda-
grass. Proceedings of the American Society for
Horticultural Science 75:700-703.

Murata, Y. and Iyama, J. 1963. Studies on the Photosynthe-
sis Of Forage CrOps. Proceedings of the Crop Science
Society of Japan 21:315-321.

Pellet, H. M. and Roberts, E. C. 1963. Effects of
Mineral Nutrition on High Temperature Induced Growth

fietardgtion Of Kentucky Bluegrass. Agronomy Journal 55:
73-“? o

Rabinowitch, E. I. 1956. Photosynthesis. Volume II.
Part z. Interscience Publishers, Inc. New York.

Smith, D. and Grotelueschen, R. D. 1966. Carbohydrates
in Grasses. 1. Sugar and Fructosan Composition of the
Stem Bases of Several Northern-Adapted Grasses at Seed
Maturity. Crop Science 6:263-266.

Sorokin, C. and Meyers, J. 1953. A High Temperature
Strain of Chlorella. Science 117:330—331.

Steele,R. G. and Torrie, J. H. 1960. Principles and
Procedures of Statistics. McGraw Hill Book Company,
Inc. New York.

Strain, H. H. l9A9. Photosynthesis in Plants. Edited
by Frank, J. and Loomis, W. E. Iowa State College Press.

Stuckey, I. H. 19A2. Influence of Soil Temperature
on the Development of Colonial Bentgrass. Plant
Physiology 17:116-122.

2A.

250

26.

27.

28.

29.

51

Sullivan, J. T. and Sprague, V. G. l9A9. The Effect
of Temperature on the Growth and Composition of the
Stubble and Roots of Perennial Ryegrass. Plant
Physiology 2A:706-71A.

Swanson, C. A. and Bohning, R. H. 1951. The Effect
of Petiole Temperatures on the Translocation of Carbo-
hydrate From Bean Leaves. Plant Physiology 26:
557-56A.

Umbreit, W. W., Burris, R. H. and Stauffer, J. F. 1959.
Manometric Techniques. Burgess Publishing Co.
Minneapolis.

Went, F. W. and Engelsberg, R. 19A6. Plant Growth

Under Controlled Conditions VII. Sucrose Content of
the Tomato Plant. Archives of Biochemistry and Bio-
physics. 9:187—199.

Went, F. W. and Hull, H. M. l9A9. The Effect of
Temperature upon Translocation of Carbohydrates in
the Tomato Plant. Plant Physiology 2A:505-526.

Yemm, E. W. and Willis, A. J. 195A. The Estimation
of Carbohydrates in Plant Extracts by Anthrone.
Biochemical Journal 57:508-51A.

APPENDIX

53

APPENDIX TABLE l.--Leaf dry matter production, grams per
25.8 square decimeters.

 

A

 

Temperature Replication (Week) Sum Mean

Regime
1 2 3 A
20-10 C 12.62 15.76 1A.96 10.A7 53.80 13.A5
25-15 C 13.5A 13.0A 13.08 12.25 51.91 12.98
30-20 C 12.36 11.77 11.88 9.77 A5.78 11.A5
35-25 C 7.91 10.72 6.38 8.63 33.6A 8.41
A0-30 C 2.88 5.16 2.08 2.12 12.2A 3.06
Sum A9.31 56.A5 A8.37 A3.2A 197.37

 

APPENDIX TABLE II.--Analysis
production, grams per

of variance, leaf dry matter
25.8 square decimeters.

 

 

Source df SS MS F
Total 19 331.8A
Replications 3 17.7A 5.91 3.50
Treatments A 293.8A 73.A6 A3.A7**
Linear Effect 1 256.99 256.99 152.07**
Quadratic Effect 1 31.68 31.68 18.75**
Residual Effect 2 5.17 2.59 1.53
Error 12 20.26 1.69

 

5A

APPENDIX TABLE III.--Per cent dry weight of harvested leaf

 

 

 

clippings.
Temperature Replication (Week) Sum Mean
Regime
l 2 3 A
20—10 C 21.19 21.68 19.76 19.99 82.62 20.66
25—15 C 22.76 20.A5 22.01 21.27 86.A9 21.62
30-20 C 21.81 22.22 22.A5 23.12 89.60 22.A0
35-25 C 23.78 2A.12 23.58 2A.12 95.60 23.90
A0-30 C 29.38 33.79 37.36 37.26 137.79 3A.A5
Sum 118.92 122.26 125.16 125.76 A92.10

 

APPENDIX TABLE IV.--Analysis of variance, per cent dry weight
of harvested leaf clippings.

 

 

Source df SS MS F
Total 19 556.07
Replications 3 5.90 1.97 0.55
Treatments A 506.90 126.73 35.20**
Linear Effect 1 356.71 356.71 99.09**
Quadratic Effect 1 98.83 98.83 27.A5**
Cubic Effect 1 3A.13 3A.13 9.A8**
Residual Effect 1 17.23 17.23 A.79

Error 12 A3.25 3.60

 

55

APPENDIX TABLE V.-—Leaf dry weight, mg per square centimeter.

 

 

 

Temperature Replication (Week) Sum Mean
Regime
l 2 3 A
20—10 C 1.60 1.71 1.81 1.76 6.88 1.72
25-15 C 2.05 2.06 2.31 2.32 8.7A 2.19
30—20 C 2.18 2.19 2.16 2.18 8.71 2.18
35—25 C 2.38 2.55 2.A2 2.27 9.62 2.A1
A0—3O C 2.89 2.69 2.70 2.39 10.67 2.67
Sum 11.10 11.20 ll.AO 10.92 AA.62

 

APPENDIX TABLE VI.--Analysis of variance, leaf dry weight,
mg per square centimeter.

 

 

Source df SS MS F
Total 19 2.20
Replications 3 0.02 0.007 0.35
Treatments A 1.9A 0.A9 2A.50**
Linear Effect 1 1.79 1.79 89.50**
Residual Effect 3 0.15 0.05 2.50

Error 12 0.2A 0.02

 

56

APPENDIX TABLE VII.--Chlorophyll content of harvested leaf
clippings, micrograms per mg dry weight.

 

 

 

Temperature Replication (Week) Sum Mean
Regime
l 2 3 A
20-10 C 8.78 8.A8 8.88 8.91 35.05 8.76
25—15 C 9.08 9.18 8.97 10.15 37.38 9.35
30—20 C 10.37 10.53 10.A6 9.97 A1.33 10.33
35—25 C 10.05 9.25 11.A7 10.99 A1.76 10.AA
A0-30 C 6.97 5.77 7.32 6.82 26.88 6.72
Sum A5.25 A3.2l A7.10 A6.8A 182.A0

 

APPENDIX TABLE VIII.-—Ana1ysis of variance, chlorophyll con—
tent of harvested leaf clippings, micrograms per mg dry

 

 

weight.
Source df SS MS F
Total 19 A2.06
Replications 3 1.92 0.6A 2.21
Treatments A 36.60 9.15 31.55**
Linear Effect 1 3.58 3.58 12.3A**
Quadratic Effect 1 22.A5 22.A5 77.A1**
Cubic Effect . 1 7.17 7.17 2A.72**
Residual Effect 1 3.AO 3.AO 11.72**

Error 12 3.5A 0.29

 

57

APPENDIX TABLE IX.--Content of 85 per cent ethanol soluble

carbohydrate in harvested leaf clippings.

Per cent Of dry

 

 

 

weight.
Replication (Week) Sum Mean

Temperature

Regime 1 3 A

20-10 C A.5 5.0 A.9 6.3 20.7 5.2

25-15 C 5.5 5.6 5.5 A.1 20.7 5.2

30-20 C A.6 A.8 5.0 5.8 20.2 5.1

35-25 C 5.9 6.0 5.7 5.1 22.7 5.7

A0-30 C 8.0 9.1 7.9 7.A 32.A 8.1
Sum 28.5 30.5 29.0 28.7 116.7

 

APPENDIX TABLE X.--Ana1ysis of variance, content of 85 per
cent ethanol soluble carbohydrate in harvested leaf clip-

 

 

pings. Per cent of dry weight.
Source df SS MS F

Total 19 32.81
Replications 3 0.50 0.17 0.35
Treatments A 26.58 6.65 l3.A8**

Linear Effect 1 16.13 16.13 33.60**

Quadratic Effect 1 7.98 7.98 l6.63**

Residual Effect 2 2.A7 1.2A 2.58
Error 12 5.73 0.A8

 

58

APPENDIX TABLE XI.--Content Of water soluble carbohydrate in
harvested leaf clippings. Per cent of dry weight.

 

Replication (Week)

 

 

Temperature —— -—
. Sum Mean
Reg1me l 2 3 A
20-10 C 6.8 5.8 5.0 6.9 2A.5 6.1
25-15 C 7.A 6.8 6.2 A.9 25.3 6.3
30-20 C 5.A 5 7 5.3 6.5 22.9 5.7
35-25 C 8.8 7.8 7.2 7.2 31.0 7.8
A0-30 C 9.5 10.8 9.7 9.A 39.A 9.8
Sum 37.9 36.9 33.A 3A.9 1A3.1

 

APPENDIX TABLE XII.--Analysis of variance, content of water
soluble carbohydrate in harvested leaf clippings. Per cent

 

 

dry weight.
Source df SS MS F
Total 19 55.35
Replications 3 2.AA 0.81 1.33
Treatments A A5.65 ll.Al l8.70**
Linear Effect 1 31.51 31.51 51.65**
Quadratic Effect 1 10.32 10.32 16.91**
Residual Effect 2 3.82 1.91 3.13

Error 12 7.26 0.61

 

59

APPENDIX TABLE XIII.--Photosynthetic rate of leaves grown

at the indicated temperature regime and tested at the light

period temperature extant. Microliters per square centimeter
per hour.

 

Replication (Week)

 

 

Temperature Sum Mean
Regime l 2 3 A
20—10 C 55.8A 59.78 55.17 50.51 221.30 55.33
25-15 C 62.50 66.15 63.73 72.61 26A.99 66.25
30-20 C 68.35 72.75 73.16 70.78 285.0A 71.26
35-25 C 79.75 78.16 70.97 79.05 307.93 76.98
A0-30 C 92.03 92.71 89.03 80.23 35A.00 88.50

Sum 358.A7 369.55 352.06 353.18 1A33.26

APPENDIX TABLE XIV.--Ana1ysis of variance, photosynthetic

rate of leaves grown at the indicated temperature regime and

tested at the light period temperature extant. Microliters
per square centimeter per hour.

 

 

Source df SS MS F
Total 19 2,699.86
Replications 3 38.35 12.78 0.67
Treatments A 2,A32.81 608.20 31.91**
Linear Effect 1 2,376.8A 2,376.8A 12A.70**
Residual Effect 3 55.97 18.66 0.98

Error 12 228.70 19.06

 

60

APPENDIX TABLE XV.--Respiratory rate of leaves grown at the

indicated temperature regime and tested at the light period

temperature extant. Microliters per square centimeter per
hour.

 

Replication (Week)

 

 

Temperature Sum Mean
Regime 1 2 3 A
20—10 C 2.52 2.51 2.87 3.31 11.21 2.80
25-15 C 5.11 A.9A 5.62 5.25 20.92 5.23
30-20 C 5.59 6.18 6.2A 6.79 2A.80 6.20
35—25 C 9.7A 9.53 9.2A 7.71 36.22 9.05
A0-30 C 10.63 9.76 10.26 8.A9 39.1A 9.79

Sum 33.59 32.92 3A.23 31.55 132.29

 

APPENDIX TABLE XVI.--Ana1ysis of variance, respiratory rate

of leaves grown at the indicated temperature regime and

tested at the light period temperature extant. Microliters
per square centimeter per hour.

 

 

Source df SS MS F
Total 19 137.07
Replications 3 0.79 0.26 0.5A
Treatments A 130.51 32.63 67.98**
Linear Effect 1 126.59 126.59 263.73**
Residual Effect 3 3.92 1.31 2.73

Error 12 5.77 0.A8

 

61

APPENDIX TABLE XVIl.-—Photosynthetic rate at three tempera—
tures and two light intensities.

 

 

Test Photosynthetic Rate, Microliters
Temperature per Square cm per Hour

2600 fc 3200 fc

20 C 2A.60 25.96

30 C 32.33 31.20

A0 C 2A.93 23.92

 

APPENDIX TABLE XVIII.—-Photosynthetic rate of leaves at
three calculated carbon dioxide levels and 30 C. Micro-
liters per mg dry weight per hour.

 

Calculated per cent

 

Carbon Dioxide Concentration Photosynthetic Rate
1.5 22.77
7.2 18.73

20.5 23.63