TIME COURSE OF PHOTOSYNTHESIS AT AN INCREASED
CONCENTRATION OF CARBON DIOXIDE
DISSERTAT ION
Presented In Partial Fulfillment of the Requirements
for the Degree Doctor of Philosophy in the
Graduate School of The Ohio State
University
By
RICHARD MORRIS CRESSMAN, B.S., M.S.
The Ohio State University
1957
Approved by:
Adviser
Department of Botany and Plant
Pathology
ACKNOWLEDGMENTS
The writer wishes to express his appreciation to
the Charles P. Kettering Foundation, Yellow Springs, Ohio,
for providing financial assistance in support of these
investigations. Also, appreciation is extended to Dr. C.
A. Swanson for his helpful guidance and criticisms in the
course of this investigation.
- ii -
TABLE OF CONTENTS
Page
LIST OF T A B L E S .....................................
LIST OF ILLUSTRATIONS
iv
.............................
V
I N T R O D U C T I O N ................ . ............
1
. . . . .
8
...................................
22
MATERIALS AND METHODS
RESULTS
..........
Photosynthesis in Relation to Carbon
Dioxide Concentration and Light Intensity
Photosynthesis in Relation to Long-term
Exposure to Increased Carbon Dioxide
Concentration
„
D I S C U S S I O N .................................
39
SUMMARY
...............................
i|9
BIBLIOGRAPHY
.....................................
£l
AUTOBIOGRAPHY
..........................
57
.
- iii -
LIST OF TABLES
Pag©
TABLE
1.
2
.
3.
Photosynthesis in relation to C02 concentration
and light intensity.
"C" is the C02 concentra­
tion in per cent and "PM Is the rate of photo­
synthesis in mg. C02 absorbed per hour per sq.
dm. oi‘ leaf area
......................28
Experimental conditions Tor the data graphed
In Figs. 9 and 10
32
Observations or aging or leaves on plants or
the stock s u p p l y ................................ 32
- iv -
LIST 0? ILLUSTRATIONS
Figure
1.
2.
Page
Diagram of apparatus used to maintain a
controlled environment and to measure photo­
synthesis........................................11
Leaf chamber, type I. Reproduced from
( 1 6 ) ..............................
13
C re s B m a n
3.
Leaf chamber, type II. Reproduced from
Bohning and Burnside (9)........................ IJ4.
1;.
Spectral data involved in the source of light
5.
System by which constant pressures were
maintained
................................... 19
6.
Photosynthesis as a function of COp concentra­
tion and of light intensity . , . . . . . . .
16
2 If.
7.
Fit testsof curves in Fig. 6
.................. 26
8.
Fit testsof curves in Fig. 6
.................. 26
9.
Course of photosynthesis as a function of age
of leaf.
A) at 0 .3 ^ CCh; B) and C) at 0.03%
C02 ...................7 ........................ 30
10.
Photosynthesis as a function of COp
tion with leaves of different ages
- v -
concentra­
. . . . .
37
INTRODUCTION
The effects on plants of exposure to carbon dioxide
concentrations above 0 .0 3 per cent for an extended period of
time have never been precisely defined.
A first supposition
would be that, because carbon dioxide is a metabolite in
photosynthesis, the increased concentration would effect an
increase in the quantities of the pho'cosynthet 1 c products
and thus an increase in the size and weight of the plant.
Attempts to verify this relationship experimentally have re­
sulted, however, in a controversial body of data.
Experimental work concerned with this problem can be
grouped Into two general categories:
(lj effects on growth
or on crop yield and (2 ) effects on the rate of photosyn­
thesis itself.
Perclval^ experiments (5 4 ) were among the
first to indicate that an increase in carbon dioxide (nfixed
air” ) can be favorable to growth, but de Saussure (22) re­
ported 8 per cent to be detrimental.
From Bohm's work (8 )
in 1 8 7 3 until the early 1 9 3 0 *s, efforts were made by several
groups to establish whether ’’carbon dioxide fertilization ’1
was beneficial or not.
Several of the earliest investigators
(de Saussure, 22; Bohra, 8 ; Jentys, 37; Montemartini, ij.8 ; and
Gerlach, 26) used carbon dioxide concentrations ranging from
2 per cent to 12 per cent and obtained detrimental effects
with respect to the controls in normal air, or no real
- 1 -
2
differences.
Even at a concentration of 0.051}. per cent,
Brown and Escombe (11) obtained no significant difference In
growth (11-day increase in dry weight) when the experimental
plants were exposed to this concentration during the day­
light hours.
When plants were exposed to 0,12 per cent
carbon dioxide, the dry weight after 10 days was leas than
that of the controls.
However, they used hydrochloric acid
on marble to obtain the carbon dioxide and Demouaay (19)
traced Injurious effects in a similar experiment to some­
thing other than the carbon dioxide - most likely the hydro­
chloric acid fumes.
Chapin (15) measured growth in length of shoots and
roots in carbon dioxide concentrations of 1 to 80 per cent
as compared with controls in normal air.
He observed a
maximum 2if-hour growth rate at concentrations of 1 to 2 per
cent.
Between 2 and 5 P©r cent, growth was about the same
as the control.
Subsequent experimenters usually used less
than 1 per cent carbon dioxide.
Demoussy (19# 20, 21),
Fischer (25)# Bolas and Henderson (10), Small and White (67),
White (76), and Johnston (3 8 )# obtained increases in growth
or yield at concentrations between 0.1 per cent and 0.2 per
cent.
Arthur e_t al.
(5) found increased growth In almost
all of 3 0 species growing in greenhouses maintained at 0 . 3
per cent carbon dioxide but no further Increase when 1 per
cent was used.
Owen at ad. (51) obtained 20 per cent
31
Increase In yield or tomatoes in 0*6 per cent carbon dioxide
and a slightly smaller increase (16 per cent) In 0 . 9 per
cent.
They exposed the plants to these concentrations for
one to two hours dally.
Several other investigators reported
positive effects of ’’carbon dioxide fertilization” but the
concentrations used were not reported (1 7 # 19# 26, 3 0 , 59).
In these instances carbon dioxide was simply flushed through
the experimental chambers or areas•
Reviews of the foregoing Investigations with practi­
cal evaluations are presented by several authors (2 , 3 , llj.,
2Ij., 39# 59# 59# 61).
Lundegardh (1*5)
Monographs have been written by
Reinau (60).
Mltscherllch# on the basis of his own experiments
(k7)t has proposed that, at full sunlight# 0.03 P©** cent
carbon dioxide effects as much yield as higher concentra­
tions, and that higher carbon dioxide concentrations merely
compensate for a lower light intensity.
His family of
curves with common saturation plateaus merely indicates that
some factor other them light Intensity or carbon dioxide
concentration was limiting maximum yield.
The consensus of
the above investigations and reports is that moderate in­
creases in the carbon dioxide concentration (,i.,e.# up to
five to seven times normal) will effect an Increase in
plant growth as long as other factors (such as light in­
tensity, essential minerals# soil moisture, etc.) are In
sufi'Icient supply, but increases of carbon dioxide concentra­
tion above thi3 value and particularly above 1 per cent are
detrimental to crop production*
Increases in yield up to
about £0 per cent have been reported and increases in fresh
weight may be as high as 150 per cent above the control*
Increased production could logically be attributed to
an increase in photosynthesis.
The relationship between
photosynthesis and carbon dioxide concentration has been in­
vestigated by many workers.
Not a few of these were concerned
with water plants; evaluations and criticisms of these experi­
ments can be found by Rabinowitch (56), and by SteemanNlelson (69# 70)*
Since several problems are involved in
photosynthesis of aquatic plants which do not exist In a con­
sideration of terrestrial plants (such as absorption of bi­
photosynthesis
carbonate ions, circulation of water, etc.)./in aquatic plants
will not be discussed in this dissertation.
Godlewski (27)/ in the earliest attempts to measure
photosynthesis as a function of carbon dioxide concentration,
obtained an ''optimum" in the evolution of oxygen in the range
of $ to 8 per cent carbon dioxide.
Kreussler (1+0 ) concluded
the existence of an "optimum" rate of photosynthesis in the
range 1 to 10 per cent carbon dioxide.
However, a re-examina­
tion of his data places a maximum at 0 . 1 to 0 * 2 per cent with
a light intensity of 5 00 to 1000 foot-candles; the data
beyond these concentrations are extremely Irregular.
Brown
and Escombe (1 1 ) demonstrated a maximum at 0*16 per cent in
5
"diffuse sunlight."
However, Lundegardh was able to get an
increase in photosynthesis up to 1 .2 per cent in full sun­
light.
Singh and Lai (6 6 ), using excised leaves, obtained
carbon dioxide saturation at 0 .1 7 per cent with about 6800
foot-candles, at 0 .1 3 per oent with 5 J+50 foot-candles and
also with 1360 foot-candles and at 0 .0 8 per cent with 330
foot-candles, a rapid decline in the rate occurred at higher
concentrations.
Hoover at al, (32), obtained carbon dioxide
saturation at O.lLj. per cent at a light intensity of 955 footcandles; when the light intensity was increased to 2 0 0 0 footcandles there was a sharp decline in the rate of increase
at 0 . 1 per cent although the increase continued up to the
highest concentration used, i.e., 0 .1 8 per cent.
The question arises as to how these investigations
correlate with increase in crop production.
Bazyrina and
Tschesnokov (7) made an attempt to study this problem.
They
measured photosynthesis during the course of one day during
which the carbon dioxide concentration was increased to 0.09
- 0.15 per cent.
At midday the rate of photosynthesis was
usually about double that of the control, but the total
photosynthetic yield for the day was, on the average, only
slightly greater than the control, as light energy was
limiting in the morning and in the evening.
However,
illumination must have been rather low as they shaded the
plants from the sun with gauze ("medizinisches Bindenzeug")
6
so that the temperature rose "only one to two degrees”
higher inside the chamber than the surrounding air.
Livingston and Franok (ijij.) studied short time effects of very
high carbon dioxide concentrations (5 and 20 per cent) and
although inhibitory effects were very much in evidence,
photosynthesis still occurred.
These authors also observed
that physiologically young leaves are more tolerant of high
concentrations of carbon dioxide than are old leaves, that
inhibitory effects of high carbon dioxide concentrations
were greater at the higher light intensities, and that
leaves could be conditioned to the high carbon dioxide con­
centrations if the concentration was increased gradually.
Thomas (71) has reported observations which indicate
a detrimental effect of 0 * 3 por cent carbon dioxide on
tomato plants when applied for 6 to 9 hours daily for several
weeks.
He also described a decrease in photosynthesis
although the actual data have hot been published.
What is
of particular note in his experiments is that it is the
first time experiments have been reported in which photo­
synthesis had been measured over an extended period of time,
during which the carbon dioxide concentration was maintained
at an elevated level for at least a part of each day.
The
longest period in which plants have been subjected to in­
creased carbon dioxide concentrations continuously end
photosynthesis measured concurrently is apparently 2 i+ to i|8
hours (Ajlj.)*
7
The present investigation is an attempt to evaluate
the effect of carbon dioxide concentration on the rate of
photosynthesis by exposing a plant to a continuously ele­
vated carbon dioxide level for the duration of the life of
a leaf.
MATERIALS AND METHODS
Apparent photosynthesis was determined by measuring
changes in carbon dioxide concentration when air was passed
over a leaf.
of a
Carbon dioxide measurements were made by means
Llston-Becker Gas Analyzer, Model 15, in conjunction
with an Esterline-Angus recording ammeter.
tion
A short descrip­
of the use of this type of instrument is presented by
Parker ( 5 3 ) «
Egle
and Ernst (23), Nuernbergk (49), and
Huber ( 3 5 ) have given detailed critiques on the method.
The principle of the instrument is based on total infra-red
absorption by the gas (non-dispersion principle) and was
first applied to measurements of photosynthesis by Scarth
et al . (6 3 ).
The instrument was calibrated for a range of 0.0 to
0 . 5 P«r cent carbon dioxide by means of tanks of compressed
air containing various amounts of carbon dioxide.
These
mixtures were obtained from the Ohio Chemical and Surgical
Equipment Company of Cleveland, Ohio.
The actual carbon
dioxide concentrations were determined by washing a metered
amount of the gas with NaOH solution, precipitating the
carbonate with BafOH^* and titrating with HC1.
The limits
of accuracy in this operation affect the accuracy of the
calibration and thus the overall accuracy of individual
measurements of photosynthesis.
- 8 -
However, the error which
9
exists in the calibration is constant and therefore cancels
itself in relative measurements of photosynthesis at the
same concentration of carbon dioxide.
At low concentrations,
this error was probably not greater than 5 per cent; at the
higher concentration, it may possibly have been as high as
15 per cent but was probably less than 1 0 .
Calibration curves for several ranges, supplied by
the manufacturer, were examined and these curves fit, very
closely, a hyperbolic relationship of the form: y - x/(m + bx),
where "x" is the carbon dioxide concentration, "y" is the
reading in microamperes (pa )9 "m*1 is the slope of the line
obtained when the reciprocals are plotted* and "b" is the
intercept of this line with the Hyw axis.
tive of '‘x 1’ with respect to "y”, .1
The first deriva­
: dx/dy « m/(l - by)^,
gives the slope at any value of ’’y11 in terms of the rate of
change of carbon dioxide concentration with change of micro­
amperes,
This method allows a more accurate reading than
could be obtained directly from the graph, first, because
the graph is relatively rough, when small changes are being
considered, and second, because deflections of only 2 to 6
microamperes were the rule.
With this amount of deflection,
readings were considered accurate generally to about 5> P«r
cent.
The apparatus was arranged as diagrammed in Pig. 1;
the code letters in the following text refer to this figure.
10
The leaf was enclosed In a leaf chamber (C) made of plexi­
glass.
Two designs were used: type I (described by
Cressman, 16, and reproduced in Fig. 2) when the air was
drawn through the system by vacuum; and type II (a modifica­
tion described by Bohning and Burnside, 9» and reproduced
in Fig. 3) when compressed air was used.
After flowing
through the leaf chamber, the air stream passed through a
drying column of Drier!te (D) before it entered the gas
analyzer (IRGA).
Although the instrument is only Blightly
sensitive to water vapor, the error introduced Is sufficient­
ly large to necessitate drying the air before measuring
carbon dioxide concentration.
A drying tube filled with
Drierite served this purpose most satisfactorily as little
resistance was offered and it was completely flushed through
in a minimal amount of time.
Finally, the rate of air flow
was determined by a "precision” wot test meter (M).
In the
experiments conducted in the plant chamber (I.e.*, the long­
term experiments), the air was drawn through the system by
a vacuum pump; in the short-term experiments, the air flowed
through the system under pressure from the compressed air
tanks.
In the extended experiments in controlled carbon
dioxide environment, a plant chamber (P) was used to enclose
the whole plant.
This chamber consisted of a wood frame lh
inches by llj. inches by 21± inches fitted with glass sides and
Fig, 1.— Diagram of apparatus used to maintain a
controlled environment and to measure photosynthesis.
(For explanation see text).
- 11 -
A A -L
-B
vacuum
pump
—P
D—
air
supply
0
o
**nb©jf>
tQp*
°®c?
Qflj
Or*
’
^u
^6 ;
Pig, 3»— Lea£ chamber , type II.
Bohning and Burnside (9)*
- ik •
Reproduced fron
15
top.
Several hose connections wore inserted through the
wooden cross-bar on one face.
The inlet and outlet for air
circulation were placed in a lower corner and an opposite
upper corner, respectively.
The chamber was painted white.
Two General Electric 300-watt reflector flood lamps (L) pro­
vided the primary illumination.
Supplementary illumination
to the extent of several hundred foot-candles was supplied
by an overhead bank of General Electric Standard Cool White
fluorescent lamps (F).
On top of the chamber and underneath
the lamps was placed a filter (B) consisting of a four-inch
layer of 0.2 percent-CuSOj^ solution in 0.05 N HgSO^.
This
solution absorbs most of the infra-red radiation while
transmitting most of the visible spectrum (79).
A small
fan directed over the surface of the filter bath served to
dissipate some of the heat.
Thus light intensities up to
3 0 0 0 foot-candles could be used with temperature increases
of only a few degrees centigrade in the leaf chamber.
The Bpectr&l characteristics of the source of
illumination are considered in Fig. I;..
The relative energy
output of a 50Q**watt lamp (curve r,B u ) is reproduced from the
General Electric Lamp Bulletin (75)*
The 300-watt lamps
which were used should roughly approximate this curve.
The
spectral transmittance of a 1 0 -centimeter path of a
5-grams-per-liter solution of CuSO^ (curve nA ,f) is estimated
from Withrowfs data (80), which include curves down to
Fig- I*.— Spectral data involved in the source of light
- 16 -
PERCENT
and
o
TRANSMISSION
R E L A T IV E
_
'-5
o
C
OF
CuS04
ENERGY OF LIGHT
(>l
o
-ti
o
0
o
g
a
>
o
<
x
o
- - - - - - - - - i- - - - - - - - - :- - - - - - - - - 1- - - - - - - - - 1- - - - - - - - 1- - - - - - - - - 1- - - - - - - - - 1- - - - - - - - - 1- - - - - - - - - 1
RELATIVE
RESPONSE OF LIGHT
-si
METER
(curve G)
05
WAVE
LENGTH
a>
o
o
o
o
0
3
O
O
L\
(curve A)
SOURCE (curves B , C , D , E , F )
<T>
°
SOLUTION
CD
>
0
o
I
18
10-grama-per-liter.
The product oi these two curves is re­
drawn as curve "C " , which is the energy incident upon the
leaf from the incandescent lamp.
Curve "D", (also from the
G. E. Lamp Bulletin) is the emission by a G. E. I4.5 0 O0 white
fluorescent lamp.
curve "E" .
When corrected by curve "A”, it becomes
Adding curve "E" to curve "C" gives curve "P"
which should approximate the distribution of energy of the
light used in these experiments.
The emission from the
fluorescent light is graphed so that the total energy is
about 20 per cent of the energy of the total light.
The
sensitivity of a Weston photoelectric cell is given in a
publication of Weston Electric (lj.) and reproduced as curve
"G."
Carbon dioxide concentrations were obtained by
"bleeding11 carbon dioxide from a tank of the compressed gas
into the air stream from the laboratory compressed-air line.
The air from this facility was first passed through a
column of activated charcoal 7 inches high and 2 % inches in
diameter to adsorb possible organic contaminants, such as
oil vapors.
A constant flow was obtained by regulating the
pressure in the system by water manometers as illustrated in
Fig. 5.
Several glass tubes of 1-raeter length were nearly
filled with water and connected in series so that up to
about 2^ meters of water pressure could be maintained.
air pressure was adjusted so that air bubbled from the
The
t o p la n t
chamber
air
-* •
CO
H
CO
Pig. 5. — System by which constant pressures were maintained
20
system.
Thus fluctuations in the delivery pressure of the
air line were dampened out.
In this manner it was possible
to obtain relatively constant carbon dioxide concentrations.
When a leaf was to be exposed to carbon dioxide
concentrations only briefly, a leaf chamber of type II was
used.
Illumination was by means of one or two G. E. 300-
watt reflector flood lamps supplemented by overhead fluor­
escent lights to the extent of several hundred foot-candles.
Light intensity was adjusted by varying the distance of the
flood lamps from the leaf and by the use of layers of
cheesecloth.
A three-inch layer of CuSOj^ solution was used
to absorb the infra-red radiation.
Air was supplied to thci
leaf chamber from tanks containing various carbon dioxide
concentrations in air.
Burpee’s Black Valentine Bush Beans were used in
these experiments.
The seeds were germinated in vermieullte
and transferred to one-quart Mason jars which contained a
modified Hoagland's solution and were aerated continuously.
The stock supply of plants, in a controlled environment room,
were subjected to a Hi-hour photoperiod of about 1200 footcandles of light Intensity at the mean plant height, a
phototemperature of about 25 ° G. and a nyctotemperature of
o
about 20 . The light supply was by Standard Cool White
fluorescent lamps supplemented by i^O-watt tungsten bulbs.
The room in which the experiments were conducted was
21
maintained on a ll|-hour photoperiod, a 2 lf° phototemperature,
o
and a 18
nyctotemperature. The temperature in the leaf
chamber during illumination was usually several degrees
higher than the room temperature.
The temperature of the
leaf chamber rose gradually from about 23° to 2i\° C. in the
morning to about 27° to 28° C. in the late afternoon.
The
plant-chamber temperature remained essentially the same as
that of the room.
T h e p H of the culture solution was originally about
four.
As
the plants grew, the pH slowly shifted to about
eight a n d then declined to an acid value again.
If the
solution was not changed by this time, the rate of photo­
synthesis decreased and the plant soon became chlorotic.
The time lapse in which this situation occurred varied from
several weeks for young plants to several days for older
plants.
The symptoms were similar to those of nitrogen
deficiency and the addition of nitrate was of considerable
aid to the plants.
For this reason,
was usually
a.dded to the culture solution, especially in the case of
■the larger plants, and the solutions were changed when the
p H started to decrease.
Approximate pH was determined by
•the use of "Universal Indicator."
The age of each leaf was recorded as the number of
days elapsed since emergence from che bud.
RESULTS
Photosynthesis In Relation to Carbon Dioxide
Concentration and Light Intensity
The relationships between photosynthesis, carbon
dioxide concentration, and light intensity which have been
published in the literature are not consistent.
For this
reason it was thought advisable to measure the relation­
ships which obtained under the conditions employed In these
experiments.
The results are illustrated in Fig. 6 .
All of
the data were collected from the same leaf, and the rates at
a particular light intensity were determined in a single
day.
The data were collected within one week and at a time
just past the maturation of the leaf when the photosynthetic
capacity of a leaf in relation to age remains relatively
constant.
The temperature In the leaf chamber varied from
22° + 0*5° C. at the lower light Intensities to 26 + 2° C*
at the highest Intensity.
Several measurements of these
relationships were made through the course of the investiga­
tion and similar curves were obtained; there was some
variation in the saturating carbon dioxide concentrations
and in the rate of approach to saturation, !•&*, the rate of
change of the slope of the curve.
These curves cannot be
compared to each other with respect to light Intensity
because of the differences in age.
- 22 -
23
The general characteristics or the family of curves
are in reasonable agreement with the results of Hoover <st a l .
(32).
The rate of photosynthesis reached a maximum value,
in the present experiments, at about 0 .1 5 P©** cent carbon
dioxide; in Hoover's data, the carbon dioxide saturation
value varied with light intensity.
However, the highest in­
tensities which Hoover used are only slightly higher than
the lowest intensity reported in the present paper and the
highest saturation value which Hoover obtained is similar
to the value illustrated in Pig# 6 .
The initial slopes in
Pig. 6 are more divergent than are Hoover's but this may
simply be a result of the higher light intensities which
were used.
The curves at light intensities of 800 and 1700
foot-candles fit a hyperbolic relationship, viz.:
p *
(pmax 0 , / ( k * C ) ’
where np n is the rate of photosynthesis, "p
" is the
nifl^c
maximum rate of photosynthesis, MC" is the concentration of
carbon dioxide, and "k” is a constant#
A test for a fit to
-this equation is the ability to get a straight line by
plotting "C/p" against "C";
this plot is drawn in
2
Q
40
4500 f.c.
3500 f.c.
o
30
2500 f.c.
700 f.c.
£
l
PER
CENT
CO
Pig. 6 .— Photosynthesis as a function of C02 concentration and of light intensity
25
-a-
Pig. 7*
The curves at 25^0, 3500* and 1+500 foot-candles
have a better fit to Smith's formulation (6 7 ):
U/K2
’’K” being a constant.
line is obtained if nC
.
C V /2
In this relationship, a straight
i
s
plotted against "C^M. The
nearness of the fit is indicated in Fig. 8.
The curve for
2500 foot-candles is plotted In both Pigs, 7 and 8 to show
the difference In fit.
The values from which Pigs. 6, 7
and 8 were drawn are tabulated In Table 1.
Occasionally, evidence of stomatal closure and re­
opening was observed during the course of measurements.
Condensation of water vapor on the interior of the leaf
chamber commonly occurred when the air flow was tilow.
The
absence of this condensation despite slow air circulation
indicated closure of the stomates.
Also, on several
occasions, while the carbon, dioxide concentration was being
•BThis type of fitting has several advantages over
plotting the reciprocals: all points can be fitted on the
graph and the absolute error will be similar for all
points. The horizontal part of the original curve will
plot as a straight line whether there is a fit or not, but
the fit is determined by on© appearance of the other
points on this line, or within a reasonable proximity
thereto, depending on the accuracy of the measurements.
Two units are added to np,* in the present case, before
plotting so that the curve p&sBes through the origin - a
characteristic of the equations under consideration.
Pig. 7»— Pit tests of curves in Fig. 6
Pig. 8.— Fit tests of curves in Fig. 6
-
26
-
(P E R
(M 6. C 02
C EN T
C O g )‘
ABSORBED /
HR. / DM.2\2
)
P ER C E N T COj,
___________________________ 2 __________
X 10'
MG.
O
O
COg
X
o
I0 2
A B S O R B E D / HR. / DM.2
M
PER
CENT
'ro
CO
CD
o IO o
o
o
2500 f.c.
CJ1
ro
Vi
28
TABLE 1
Photosynthesis in relation to CO2 concentration and
light Intensity.
"C" is the CO2 concentration In per
cent and "P" Is the rate of photosynthesis In mg. CO2
absorbed per hour per sq. dm. of leaf area
G
P
C/(P + 2)
Light intensity - 800 f-c.
.0 1 3
.026
•066
.117
.1 6 7
.213
.338
.1*18
4
5.7
9.7
10.5
12.3
12.3
12.7
13
.0022
.0 0 3 k
.0056
.0094
.0117
.0 1 4 9
.0 2 3
.028
Light intensity - 17 00 f-c.
.Oik
.026
.071
.113
.208
.331
.411
4.7
6.7
17*3
21
20
22.5
21*
21*
C
P
.1 6 6
.0021
.0 0 3 0
.0037
.0049
.0075
.0085
.0127
.0159
C/(P + 2)
C
P
c2
c2/(p
+ 2)
Light intensity - 3500 f-c.
.013
.025
4
.0 7 2
26
32
33
.110
.161
.213
.328
.407
3
36.5
37
.0 0 0 1 7
.0 0 0 6 3
.0052
.0121
.026
.045
.108
.165
4 . 8 x 1 0 ~6
6 .3
"
6 .7
"
10.2
21
35
72
"
"
"
"
no
"
Light intensity 4500 f-c.
.012
.025
.068
.111
.154
.206
.331
.405
3.5
9.5
28.5
35
37
36.5
37
37
.0 0 0 1 4
4 . 8 x 10"6
.00063
.0046
4.0
.0 1 2 3
.0236
.0425
.1 1 0
.1 6 4
C2
4 .9
9.0
15.2
29
72
108
"
"
"
"
"
“
n
C^/(P + 2)2
Light intensity 2500 f-■c.
.012
.025
.060
.107
.178
.212
.326
.4 0 a
3*7
7.7
21
28.5
30
29
31
30
.0021
.0026
.0026
.0035
.0056
.0069
.0099
.0127
.0 0 0 1 4
.00062
.0 0 3 6
.0 1 1 4
.0315
.045
.106
.1 7 0
*4 4 x 10 ’
.68
.68
1*22
3.14
4*8
9.8
16
M
"
“
"
"
"
29
increased, photosynthesis remained constant over a series or
several concentrations, then jumped to a new value.
Re­
measuring at the lower levels gave new, higher values which
fit into a smooth curve.
The factors which brought about
stomatal closure in these instances are not known.
Photosynthesis in Relation to Long-term Exposure to
Increased Carbon Dioxide Concentration
In each of these experiments, a bean plant with
several well-developed leaves was selected from the stock
supply of plants and placed in the plant chamber; the
carbon dioxide concentration was adjusted to about 0.3 per
cent, and photosynthesis was measured one to three times
daily through the course of several weeks until the rate
dropped to or near zero.
Several curves obtained in this
manner are illustrated in Fig. 9A by curves MA , !1 MB,n and
"C."
Curves nE tt and MD t! In Fig. 9B were obtained under
similar conditions, except that the carbon dioxide concen­
tration was about 0 . 0 3 per cent; these two curves represent
the extremes of several runs.
Light intensities, carbon
dioxide concentrations, and temperature ranges are given in
Table 2.
Temperature and carbon dioxide measurements were
taken at the same time as the rate of photosynthesis was
read.
It was necessary to trim the plant occasionally for
two reasons: the new growth shaded the experimental leaf
Pig. 9*— Course of photosynthesis as a function of
age of leaf. A) at 0.3% C02 ; B) and C) at 0.03% C0P .
(See Table 2 for environmental conditions.)
- 30 -
MG.
C02
A B S O R B E D / HR. / D M 2
o j
o
o
AGE
ro
O
OF
LEAF
DAYS
OJ
o
O
~n
cn
O
O
00
32
TABLE 2
Experimental conditions for the data graphed
in Figs. 9 and 10
Fig. 9
Curve
A
B
C
D
E
F
COp concen­
tration, %
.28
.26
.28
.028
.022
.28
PiS* 9-C
-
Light
intensity
f-c.
1800
2800
2800
.35
.35
.35
2500
2800
23-5
21+.5
25
22
2k
26
2800
23.5 - 27
2700
.0 3 7
.0 3 2
.37
.028 - .039
Approx. time
expansion of
Temperature leaf ceased,
Extremes* C • _ day
-
16th
1 5 th
ll+th
22nd
2i+th
1 5 th
27
29
29
28
29
30
TABLE 3
Observations of aging of leaves on plants of the
stock supply
Symptom
Slight chlorosis
(usually mottled)
Slight necrosis
Slight chlorosis
Approx. age
of leaf, weeks
Frequency
1
2.5
3*5 - 4 .5
5
- 6.5
4
3
4
3
-
4*5
Average,
weeks
4.3
4*3
Severe chlorosis
Some necrosis
6
- 7
2
No visible
symptoms
2.5
-
4
3
6.5
33
and the carbon dioxide concentration was considerably re­
duced if too much foliage was present.
This latter situa­
tion was the cause of most of the variation in carbon
dioxide concentration which did occur..
Daytime temperature varied as much as six degrees
during the course of an experiment.
No experiments were
designed to test the effect of temperature on photosynthesis,
but no correlation was noted in the existing data.
Rabinowitch (56, p. 1220) generalizes that Hfor land plants
in moderate climates, the optimum (temperature) is situated
at 30 - 35° C."
Because the optimum temperature for appar­
ent photosynthesis (I.e., true photosynthesis minus respir­
ation) is lower than that for true photosynthesis due to
the temperature effect on respiration, the present experi­
ments were most likely conducted in the range of tempera­
tures optimum for apparent photosynthesis, i.e., where the
near unity.
Therefore any effect which temperature
might have in these experiments would be expected to be of
less magnitude than the experimental error.
At a level of 0*3 per cent carbon dioxide, photo­
synthesis began diminishing when the leaf was 2 to 2js weeks
old.
Immediately following the initiation of this decline,
there was a visible deterioration of the leaf.
But it was
not until the leaf was almost completely deteriorated that
photosynthesis ceased entirely.
Thus there was no indication
3k
of a direct inhibition of photosynthesis by carbon dioxide.
The rest of the plant, i.e., the younger leaves, appeared
to be still in a very healthy condition.
Although photosynthesis at 0.03 per cent sometimes
decreased after 2 to 3 weeks, the diminution was not always
evident.
The extremes are illustrated in Fig. 9B.
By the
termination of each experiment at this concentration, the
leaf had become quite chlorotic and large necrotic areas
had developed.
The existence of complicating conditions is
suggested in Fig* 9C.
By the 22nd day, photosynthesis had
declined to about one-half its maximum value.
At this time
the incandescent illumination was turned off and the plant
was exposed to only several hundred foot-candles of fluores­
cent lighting.
Five days later, the incandescent bulbs
were again lighted.
The rate of photosynthesis was now
higher than the previous measurement and this rate was main­
tained for a considerable period of time and even exhibited
a further increase before a decline commenced.
The leaf had
undergone inter-veinal growth and presented a strongly
crinkled appearance by the 6th to 7th week.
This rejuvena­
tion of interveinal growth was observed occasionally when
the leaf had been enclosed in a chamber for a prolonged
period of time at a normal carbon dioxide concentration.
Another interesting and somewhat similar phenomenon
was observed on the plants growing in 0.3 per cent carbon
dioxide.
When mature leaves were not present on the plant
{as a result of pruning), the leaves emerging from the bud
experienced a more rapid growth of the Interveinal tissue
than of the veins, resulting In a severe crinkling of the
leaf.
The leaf remained greenish-yellow In color, necrotic
areas developed soon after emergence, and the leaf died
after attaining a length of several centimeters.
If a
mature, trifoliate leaf was left on the plant, the new
leaves usually developed into large, healthy leaves.
Crinkling was rarely observed in these leaves.
These obser­
vations were Incidental and no specific experiments were
conducted to study this relationship.
noted about three times —
leaves were trimmed.
The phenomenon was
the only times all the mature
Because of these detrimental effects,
at least one mature leaf was left on the plant in the re­
maining experiments.
Observations were made on the deterioration of
leaves of the stock supply of plants and are listed in Table
3*
Incipient chlorosis was observed, on the average, after
about four weeks, with necrotic areas generally appearing
shortly thereafter.
It was found, however, that consider­
able chlorosis could occur before photosynthesis became
seriously Impaired at 0.03 per cent carbon dioxide.
This
observation Is in agreement with the concept that chloro­
phyll concentration is seldom a limiting factor in
36
photosynthesis at usual atmospheric concentrations of carbon
dioxide.
On two occasions, the culture solution of the plant
being exposed to 0*3 P©r cent carbon dioxide became deficient
in certain ions as indicated by a strongly acid reaction
(pH of about eight) as has been described under Materials
and Methods.
Visual deficiency symptoms had not yet become
apparent, but the situation was noted because of a rapid
decrease in the rate of photosynthesis.
One of these
instances is given as curve "F" in Fig. 9A.
Visual deterior­
ation of the leaf did not become prominent until photo­
synthesis had ceased, and within two days the leaf was
almost completely necrotic.
The decline of photosynthesis with age of leaf was
also evident in darbon dioxide curves which were made on
leaves of different ages.
Maximal rates were observed up
to the approximate time of cessation of expansion (about the
third week).
Thereafter a decline was usually observed.
This is in agreement with Singh and Lai (6£) who observed
highest rates of photosynthesis in ’’young" leaves, lower
rates in "mature" leaves, and lowest rates in "old" leaves
if the leaves were all from plants of the same age.
did not state their criteria of age.
They
Several curves, repre­
senting different leaves, are shown in Fig. 10.
The data
are selected to illustrate the general trend which was
CVJ
10 days
cn
-3
28
days
35
days
20
PER CENT
CO-
Pig. 10. — Photosynthesis as a function of C02 concentration
with leaves of different ages.
observed.
Curves or this type varied as to degree of slope
of the initial rise and the rate of approach to saturation.
When the same leaf could be used for 1 to 2 weeks, a drop
in the rates at the higher carbon dioxide concentrations,
as indicated in Fig, 10 by the 10-day and the 28-day curves,
was quite consistent.
The effects of age of plant reported
by Singh and Lai were not observed in these experiments as
long as the plants were supplied with sufficient nutrients
and were not allowed to set fruit.
These authors found
photosynthesis to be most active in leaves from mature
plants.
activity.
Leaves from young or old plants showed less
DISCUSSION
The series of curves showing the rate of photosynthe­
sis as a function of both carbon dioxide and light intensity
which are presented in Fig. 6 approximate the Type II re­
lationship described by Rabinowitch (56, P* 862).
The
initial slopes are divergent and the saturation plateaus are
separate.
According to Rabinowitch (56, p. 869) this con­
dition signifies that both variables affect the same reaction
step, or that the rates of the reactions affected by each
variable do not differ from each other to any great extent.
Inasmuch as carboxylation of a carbon dioxide acceptor and
the transformation of radiant energy into chemical energy
are separate phases in the process of photosynthesis, carbon
dioxide and light cannot be considered to affect the same
reaction and the production of reducing power by light have
approximately equivalent maximum rates.
Expanding on this concept, the reducing power In the
system becomes the primary limiting factor at low Intensi­
ties, and the rate of photosynthesis should then become a
hyperbolic function of the carbon dioxide concentration if
the assumption is made that the carbon dioxide acceptor is
present In non-limiting concentration.
The function should
be, Ideally, a Mlchaells-Menten hyperbola.
- 39 -
ho
When the light intensity approaches saturation, the
higher rates of photosynthesis at higher concentrations of
carbon dioxide produce a severe drain on the pool of the
carbon dioxide acceptor, which, according to our present
biochemical knowledge, is ribulose diphosphate.
However,
due to a higher concentration of photosynthetic products,
there will also be a higher rate of production of ribulose
diphosphate.
In the experiments of Wilson and Calvin (79)*
the drain on the pool at 1 per cent carbon dioxide apparent­
ly was greater than the rate of synthesis of ribulose di­
phosphate, since the pool was less at 1 per cent carbon
dioxide than at 0.003 per cent.
Limitations in the rate
could, therefore, arise by the effects of the ribulose
diphosphate concentration also.
Thus the rate relationship becomes quite complex and
the graphic representations must depart from a simple hyper­
bola.
Smith’s representation (68) appears to approximate an
empirical representation of the curves at high light
intensify:
or, rearranged:
P
2
where nC n is the concentration of carbon dioxide, upn is the
ill
rate of photosynthesis, ’’P m ^ " is the maximum rate of photo­
synthesis, and “K" is a constant.
In determinations of rates of photosynthesis as a
function of carbon dioxide concentration, it has been found
usually that the rate becomes constant at some percentage
or that sometimes the rate continues to increase with in­
creasing carbon dioxide concentration up to the highest con­
centration used.
rarely.
Definite inhibition has been observed only
Ballard (6) found depressant effects at 5 par cent
only under certain conditions.
Measurements of photo­
synthesis at high concentrations of carbon dioxide are quite
difficult to make accurately; most methods have a large
amount of variability.
One method with sufficient sensi­
tivity is the manometric technique and the use of leaf
discs (e.g., see Livingston and Franck, ljl|)*
^n this
method the possibility of effects of injury due to cutting
the leaf discs cannot be disregarded.
Thus immediate
Inhibitory effects of high carbon dioxide concentrations on
photosynthesis are not definitely established.
What has
been indicated, though, is that after the plant Is exposed
to high concentrations of carbon dioxide for a period of
time, certain aspects of growth may be affected.
Indeed,
Brown and Escombe (11) found that despite the ineffective­
ness of carbon dioxide in increasing yields, the leaves of
plants exposed to the higher carbon dioxide concentrations
1*2
contained much more starch than control plants.
The experiments described in this paper are an
attempt to arrive at a more critical understanding of the
situation.
The most striking fact which appeared when the
plant was subjected to 0*3 per cent carbon dioxide was the
shortened life of the leaf and the suddenness of its deteri­
oration.
The decline in rate of photosynthesis was closely
correlated with visual deterioration of the leaf and seems
to be a result of the processes which cause the deterioration
rather than a direct effect of carbon dioxide inhibition of
the photosynthetic apparatus*
However, in the present experi­
ments it appeared that, in general, the harmful effects of
this concentration do not exceed the benefits.
The in­
creased production of total photosynthate by the leaf at 0*3
per cent carbon dioxide may more than outweigh the decrease
in longevity.
The effects of carbon dioxide appear to be
the early induction of senescence.
In the further analysis of the situation, it would be
well to consider all known reactions in which carbon dioxide
can participate in the metabolism of a plant:
1.
The carboxylation of ribulose diphosphate (55*
7h) •
This reaction, being the mechanism of fixation of carbon
dioxide in photosynthesis, can hardly be a likely candidate
for direct adverse effects.
The substrates and products are
normal plant constituents which may exist in relatively
largo concentrations.
2.
Reversal of decarboxylat ions of the Kreb'a cycle:
a.
Succinyl CoA * CO^ — ~ ■>
alpha-ketoglutarate
b.
Alpha-ketoglutarate + CO2 i- — ~ ■„
ieocitrate
The masB law effect of increased carbon dioxide concentra­
tions would, be to reduce the rate of respiration and effect
a greater concentration of the acids of the cycle in the
cell.
However, since the reaction equilibria are strongly
toward de-carboxylation and since 0.3 P©r cent carbon
dioxide is quantitatively very small, little effect should
be expected from these reactions.
3.
Carboxylation of pyruvate
a.
"Malic enzyme" system: pyruvate + CC>2
TPNH
malate + TPN
b.
Wood-Workman reaction: pyruvate + COg * - ■ >
oxalacetate
c.
Phospho-enol pyruvate + CO^ f: — -
oxalacetate +
These reactions would increase the concentration of oxal­
acetate and malate in particular, and compounds of the
Kreb's cycle in general.
Since this situation occurs regu­
larly in succulents via the reaction in part "c" (62, 73 )*
it is doubtful if harmful effects could be derived from this
source, although effects of increased acidity over long
kb
periods
l\.»
of time cannot be completely disregarded.
Proprionyl CoA ♦ CO^ ♦ ATP 1 - ^ succinyl CoA ♦ADP
+ HPO^’ .
Whitely (77, 7 8 ) showed this reaction to be reversible and
James (3 6 ) showed that the synthesis of odd-numbered fatty
acids were dependent on this reaction (in the reverse of
the above).
Thus high carbon dioxide concentrations could
cause a deficiency of fatty acids and other compounds which
involve
a proprionyl derivative in their syntheses. At the
present
time, little is known of these processes.
5*
Acetyl CoA + CC>2
pyruvate
Ochoa (50) demonstrated an exchange of C ^ between carbon
dioxide and the carboxyl carbon of pyruvate and thus indi­
cated that the decarboxylation is reversible, albeit
insignificantly so.
6.
Ribulose-5-phosphate + c0 2 i===? 6 -phosphogluconate
Horecker (33* 3U)
demonstrated the reversibility of
this reaction and of the oxidation of glucose-6 -phosphate
to 6 -phosphogluconate.
He calculates an equilibrium con­
stant for the reductive decarboxylation of phosphogluconate
as 1.9 liters per mole.
Thus, he states, that in 5 per cent
carbon dioxide and with one-half of the TPN in a reduced
state, 99 per cent of the phosphogluconate would be
oxidized.
The effect of carbon dioxide on increasing the
rate of carboxylation reaction can thus be considered to be
negligible.
A similar situation could probably be found
with the above carboxylations with the possible exception of
reaction
7.
Ornithine + C02 +
^
citrulline
Recent evidence (57* 29) indicates that the mechanism of
this reaction proceeds via the formation of carbamyl
phosphate:
KH^ + C02 + ATP
NH2 -G0-0P0^“ + ADP
The carbamyl phosphate is then capable of combining with
ornithine to give citrulline or with aspartatic acid follow­
ed by the synthesis of pyrimidine (57) •
Thus indications
are that carbamyl phosphate is an important metabolite in
the cell*
6.
Synthesis of purines and pyrimidines
Carbon dioxide has been found to be directly involved in the
synthesis of purines and pyrimidines (12, 30, lj.1, 61j.)*
sequence of reactions is discussed by Carter (13)*
The
Carbon­
ic-labelled carbon dioxide becomes located in the ureidocarbon. of pyrimidines (31) said in the number 6 carbon of the
purine ring (12).
Derivatives of these compounds known to
be of importance in metabolism are ribonucleic acids,
deoxyribonucleic acids, purine and pyrimidine nucleotides,
flavin adenine dinucleotide, the pyridine nucletides,
coenzyme A, kinetin, and thiamine.
compounds is increasing yearly.
The known number of Buch
It should be expected,
therefore, that carbon dioxide concentration should have some
effect on the concentration of these compounds and thus on
metabolism.
Many effects of carbon dioxide on plant growth have
been observed.
Carbon dioxide, in concentrations above 1
per cent, has been found to inhibit sporophore formation in
mushrooms (lf.2)»
But the presence of at least small amounts
of carbon dioxide appear to be requisite for germination of
sporangia of Phyaoderma (72).
In Avena seedlings, the
mesocotyl and colejptile react differently to increased
carbon dioxide concentrations (I4.6 ).
When the mesocotyl was
exposed to concentrations up to 10 per cent, elongation was
depressed relative to the control in normal air during the
first three days.
At the end of seven days, the mesocotyls
of the seedlings in 5 por cent carbon dioxide had elongated
the most.
Elongation of the coleoptiles was likewise
depressed by the increased carbon dioxide concentrations but
the effect persisted through the course of 9 days.
The
accelerating effect on the mesocotyls was still observed If
the seedlings were transferred to normal air at the end of
3 days.
Another effect of carbon dioxide was observed by
Wood f8 l) on thermonastic movements In tulip and crocus
47
flowers.
Increasing the carbon dioxide concentration caused
a marked cell extension and a lower optimum temperature for
growth.
Effects of carbon dioxide on abscission are mention­
ed In a review by Addicott and Lynch (1).
Carbon dioxide is
reported to have accelerated flower abscission in Nlcotlana
and to have retarded abscission in bean leaflets.
Carbon
dioxide also has been reported to have various effects on
flowering.
When Kalanchoe is exposed to inductive photo-
periods, a large rate of dark fixation of carbon dioxide
occurs (20); only a small amount occurs In non-inductive
photoperiods (long days)*
Parker and Borthwick (52) did not
obtain formation of flower buds in Biloxi soybeans in carbon
dioxide-free air.
Increasing the carbon dioxide concentra­
tion above that of normal air increased the number of
flower buds formed.
Liverman (43) notes a correlation of
the effect of high temperature during the dark period on
decreasing the flowering response with the effect on causing
carbon dioxide evolution and supplies further discussion on
the problem.
The above citations indicate that carbon dioxide Is
essential in some phases of metabolism other than photosyn­
thesis, and can affect a variety of others*
The role of
carbon dioxide in the synthesis of purine and pyrimidine
compounds can account for its essentiality.
Large concen­
trations of carbon dioxide would be expected to lead to
larger amounts of these compounds in the cella and various
effects upon metabolism should follow.
It Is suggested, then, that high, sustained levels
of carbon dioxide result In toxic concentrations of purine
and pyrimidine derivatives.
The effect on photosynthesis is
interpreted as being secondary.
Further evidence for this
situation is the fact, described above, that young leaves
exposed to 0,3 per cent carbon dioxide usually experienced
less rapid growth of the vein than of the intervelnal
tissues when mature leaves are absent from the plant.
presence of a growth-affecting substance is Indicated.
The
The
actual effect of the carbon dioxide may be due to inhibition
of metabolic processes or it may be an effect closely allied
with senescence of the leaf.
SUMMARY
Further studies have been made or effects of carbon
dioxide on green plants.
For the purpose of correlating
certain aspects of the work with previous investigations,
the relationship of photosynthesis to carbon dioxide con­
centration and light intensity was measured.
A family of
curves was obtained which corresponds to the consensus of
previous data.
The major part of the research was concerned with
the effects on the plant of continuous exposure to a high
level of carbon dioxide.
The experimental plants were
placed in a closed cabinet which was flushed with air en­
riched with carbon dioxide to a concentration of about 0«3
per cent.
Photosynthetic rate, as a function of age of
leaf, was found to start declining when the leaf was about
weeks old.
At about 1+ weeks of age, the leaf was no
longer capable of carrying on photosynthesis.
When photosynthesis was measured on plants which re­
mained in a natural atmosphere, a decline was sometimes
observed.at about 3 weeks, and sometimes not.
Curves of
photosynthesis as a function of carbon dioxide concentration
exhibited lower saturation plateaus for the older leaves.
The decline in photosynthesis at high carbon dioxide
concentrations is considered to be an indirect effect of
-
k9
-
50
changes in metabolism rather than a direct inhibition of the
photosynthetic mechanism by carbon dioxide.
All known re­
actions by which carbon dioxide can participate as a meta­
bolite have been considered as pathways for effects on plant
growth.
The only reactions which appear to be capable of
gross effects on metaboism are the incorporation of carbon
dioxide into purines and pyrimidines.
It is suggested that
the effects of high carbon dioxide concentrations are a
result of the synthesis of derivatives of these compounds.
BIBLIOGRAPHY
1.
Addicott, F. T. and R. S. Lynch. Physiology of
abscission. Ann. Rev. Plant Physiol. 6:211-238.
1955.
2..
Anon., Article 626. International Rev. Sci. Prac.
Agric. 1920. p. 696.
3.
.
Article 7 0 4 .
Ibid. 1921. p. 809.
if.. _____ • Technical Data -- Weston Photronic Cell.
Weston Electric Instrument Corp. Newark, N. J.,
1935.
5*
Arthur, John M., J. P. Guthrie, and J. M. Newell. Some
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14-82. 1930.
6.
Ballard, L. A. T. The depressant effect of carbon
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7.
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9.
Bohning, R. H., and Christel A. Burnside. The effect
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557-561. 1956.
10.
Bolas, B. D., and F. Y. Henderson. The effect of in­
creased atmospheric C0P on the growth of plants. I.
Ann. Bot. 1^2:509-523. 1928.
11.
Brown, H. T. and F. Escombe. The influence of varying
amounts of COg on the photosynthetic process of
leaves and on the mode of growth of plants. Proc.
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-
51
-
52
12 .
Buchanan, John M . , John C. Sonne, and Adelaide M.
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The role of lactate, glycine, and CO2 as precursors
of the carbon chain and nitrogen atom 7 of uric
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13.
Garter, Charles E. Metabolism of purines and pyrimi­
dines. Ann. Rev. Biochem. 25:123-146.
1956.
*.
11
15.
Cerighelli, R. Emploi de COP comme engrais
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1921.
Chapin, P. Einfluss der Kohlensaure auf das Wachstum.
Flora. 91:346.
1902.
16 . Cressman, R. M.
A time study of the effects of in­
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17.
18
.
Cummings, M. B. and C. H. Jones. The aerial fertiliza­
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________ • The aerial fertilization of plants with
COo.
J. Chem. Soc. Abs. 118, no. 6 8 9 Pt. I, p. 2 6 7 .
1920.
19.
Demoussy, E. Sur les vegetation dans des atmospheres
riches en acide carbonique.
Compte rendus Seances
Acad. Sci. 136:325-328.
1903.
.
21.
_______ .
20
22
.
Ibid. 139:883-885.
1904.
_______ • Influence sur las vegetation de I'aclde
carbonique emis par le sol. Ibid. 138:291-293.
1904.
De Saussure, T.
Paris.
1904.
Recherehes chimiaues sur la vegetation.
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AUTOBIOGRAPHY
I, Richard Morris Cressraan, was born in Bethlehem,
Pennsylvania, on August 1 5 » 1928.
I received my secondary
school education in the public school system of The Borough
of Fountain Hill, Pennsylvania,and my undergraduate educa­
tion at Pennsylvania State College (now Pennsylvania State
University, University Park, Pennsylvania), from which I
received the Bachelor of Science degree, with Honors, in
1950.
While in residence there, I held, for two years, a
scholarship provided by the Pennsylvania Power and Light
Company.
From 1950 "to 1953* I held a graduate assistant -
ship in the Department of Botany and Plant Pathology at The
Ohio State University, which granted me the Master of
Science degree In December of 1952.
After fulfilling mili­
tary service requirements from 1953 to 1955* I returned to
The Ohio State University.
At this time I was appointed to
a fellowship sponsored by the Charles F. Kettering Founda­
tion at Yellow Springs, Ohio.
I held this position for two
years while completing the remainder of the requirements
for the degree, Doctor of Philosophy.
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57
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