soybeans are currently underway in growth chambers at. Kennedy. Space ..... soybean grown in a recirculation hydroponic system. (This issue). 3. Coombs,. J.,.
N91-3i780 EFFECTS
OF
ATMOSPHERIC
CO 2
CHARACTERISTICS
R. M. Wheeler, Bionetics Corp. Research
C. L. (RMW,
Office
OF
Mackowiak, CLM) and
(JCS,
WMK),
ON
PHOTOSYNTHETIC
SOYBEAN
J. NASA
LEAVES
C. Sager Biomedical
Kennedy
Space
and
W. M. Knott, The Operations and
Center,
FL
ABSTRACT Soybean and flux
(Glycine
2000 umol (PPF) of
exposed to assimilation general mol -_,
cv.
McCall)
plants
step changes of CO 2 rates (CAR), i.e.,
CAR increased but not from
previous and PPF. tend leaf
_
were
mol -± CO 2 f_r 39 days and 300 umol m -_ s -_. Individual concentration leaf net
leaves showed contrasts
"lazy" at conductance
that
predicted
short-term Ecological
for
an
at
f{om -_.
actively
growing
did not period, on CAR.
to
study In
time. diurnal
CO 2
umol of the CO 2
Although rhythms
show these rhythms indicating that Such measurements
CO 2 exchange dynamics System (CELSS) can be soybean
I000,
photon then
at similar that plants
elevated CO 2 levels over (to water vapor) showed
changes in Life Support
500,
500 to i000 Regardless
similar CAR with reports
entrained to the photoperiod, leaf CAR and remained constant across the light stomatal conductance had little effect suggest Controlled
grown
photosynthetic leaves were and PPF photosynthesis.
when CO 2 increased i000 to 2000 umol mol
CO 2 level, all This observation
to become stomatal
a
for a closely
crop.
INTRODUCTION Soybean currently
(Glycine under
max
L.)
is
among
for
use
in
a
and
is
tentatively
study
Support
System
(CELSS;
I)
testing
in
Biomass
Production
Center
in
underway
the 1990.
in
preparation been
the
chambers
the
at
Kennedy major
of
elevated
CO 2
on
under leaves
all
of
these
transpiration) the
focus
93
to
Kennedy
are
leaf
in
these
temporary
gas
studies and
exchange were
CO 2
Space
currently
development
atmospheric
exposed
for
Center of
measurements
different
were
Space
tests,
at
soybeans
plant
Life
scheduled (BPC)
with
A
and
grown
tests
crops
Ecological
Chamber
studies.
During
candidate
Controlled
BPC
effects
photosynthesis
addition,
growth for
production.
plants
Preliminary
the
biomass (i.e.
taken
levels.
changes
has
from In
in
irradiance
and atmospheric
environment bilities
of
of
the
effects
on
the
rate
set
of
had
any
the
leaves. of
of
grow-outs events
at
METHODS
the
plant
in
and
Lite
a
light
was
kept
studies
were
either
the
or
closed
conducted at
an
CO 2 a
community
indication
irradiance system.
during leaf
A
the
BPC
level
with
grown
in
level.
20
at
±
i000,
and
system.
Analyzer to
±
65%
±
and
with
C
the
adjustments
and
for
the
94
of
chamber mol
-I
scale).
a
an
points used
12-hr
dark
±
C
0.5
CO 2
levels
(ppm)
(set
taken
drift
during humidity
points
dioxide gas
CO 2
VHO
were
levels
control
automatically
determination, were
held
analyzer
computer
were
30
separate
Carbon
for
by
relative
infrared
m2
photosynthetic
three
dedicated
0.25 film
provided
dark;
series
instrument
necessary.
was
26
using
regression
s -I
at
full
span
A
maintained
umol
with
(2).
/
which
CA)
nutrient
light
during
2000
using
12-hr
A
controlled
zero
m -2 a
5%.
2%
were
solution umol
0.5
plants chamber
were
±
Barbara,
update
30
during
approximately
monitored
McCall)
nutient
lamps
and
500,
manual
be
growth
300
conducted
Santa
while
of
constant was
day
walk-in
complete
cycle
(Anarad,
each
growing capa-
provide
within
events
cv
Temperatures
within
plants
or
max
fluorescent
maintained to
in
will
canopy
a
(PPF)
photoperiod. the
by
the
photosynthetic should
changes
compare
(Glycine
flux
Vita
results
whether
MATERIALS
trays
photon
determine
inherent
measurements
Soybean
technique
The
uptake
directly
to
on
transient
to
AND
plastic
effects
CO 2
follow-up
CO 2
made
as
At 36 days after
planting,
single
the top of the canopy were selected measurements.
Carbon dioxide
fully-expanded
leaves at
for gas exchange
assimilation
rates
leaves were determined using an LCA2portable
(CAR) of the
photosynthesis
system with a PLC model B leaf chamber (ADC Co., Hoddesdon, England).
The incoming gas stream to the cuvette
from a CO2-enriched (3510 umol mol-I) Different
CO2 concentrations
was provided
compressed air
were obtained from this
using an ADCGD600gas diluter
to selectively
gas supplies
air
stream
shunt portions
the flow through a soda lime column to remove CO2. was used to provide
supply.
of
This system
of 0, 255, 440, 695, 1040, 1290,
1480, and 2030 umol mol-I CO2.
Higher levels
were not used
because of the inability
to span the infrared
analyzer
beyond 2100 umol mol-I.
Different
were obtained by
using the existing screening
for levels
with fluorescent controlled
radiation
plus supplemental radiation
optic
lamp with dichroic
guide.
unit,
quantum sensor (Li-Cor
Each single
from a rheostatreflector
and focused was
could thus be kept within
temperature.
sensor on the ADC leaf cuvette a Li-Cor
(63, 40, 28%), or
dish to reduce the long wave
Cuvette temperatures
± 0.3 C of the initial
(metal)
This supplemental radiation
through a glass petri
component.
with neutral
less than 300 umol m-2 s-I
incandescent
with a fiber filtered
fluorescent
PPF levels
unit
Inc,
In addition
to the radiation
PPF levels
were checked with
Lincoln,
leaf was exposed to the entire
PPF regimes, with a set of measurements lasting
NE). set of CO2 and approximately
4
hours. This was done to expedite measurements during the middle of the photoperiod
and to avoid leaf to leaf variability. 95
This
approach risked
disturbing
from the physical cuvette.
contact
the leaf
(e.g. closing
and/or altered
To avoid drying the leaf,
leaf
stomata)
environment of the
the air
stream desiccant
loop
of the gas supply system was bypassed thereby keeping cuvette relative
humidities
between 60 and 80%. To determine whether the
measurements were themselves having any disruptive measurements at the ambient in
the
all
middle,
cases,
and
at
initial
repeatable
even
physical
between
end
after
4
of
on
incoming
and
basis)
multiplied
by
each
min
and
divided were
were
outgoing
CO 2
air
of were
leaf
for
water
In
effects
of
the
rates. as
concentrations
area
before,
consistently
minimal
flow
taken
measurements.
calculated
stream
the
made
set
were
photosynthetic
rates
by
levels
indicating
leaf
the
PPF
rates
hours,
assimilation
corrections
and
photosynthetic
measurements
Carbon
-I)
the
CO 2
effects,
difference
(on
rate
(6.25
the
a
molar
(approx.
cm 2)
interference
300
(3).
in
ml
No
the
readings.
RESULTS Prior CO 2
and
PPF
to
determine
in
Figs. the
showed
a
light
period.
CAR
whether and
2,
light distinct period
leaf
effect
However, were
to
any
measured
diurnal
CAR
measurements
period,
but
diurnal and
on
leaf
avoid
any
taken
photosynthetic
was
then
within
across
tended
stomatal
in
stomatal
photosynthetic
rates
diurnal
hours
96
of
12-hr
the
the
water
to
the
onset
of
of
vapor
middle the
conductance (CAR)
shown
constant to
effects, middle
photoperiod As
remain
prior
with
changing
existed. to
peaking
changes
2
the
to
conductance
decreasing
possible
response
differences
rhythm,
Interestingly,
little
data
testing
levels,
1
across
the
to
of dark
had
(Figs
1
and
all
gas
the
photoperiod.
2).
exchange
The levels
effect on
shown
in
of
leaf
CAR
Fig.
3.
plateau
at
the
CO 2
response
m -2
s -1,
no
grown CAR
was
at
2000
5);
and
data
CO 2
PPF
levels
up
1040
umol
at
to
PPF
to mol
-I
the
highest
the
CO 2
decrease leaves
taken
(Fig.
-I
also
CO2,
but
showed
near 1040
PPF
were
CO 2 510
or
plants
with
umol
mol
peak -I
positive A
similar
840,
increase from
the
not
plants
of
not
no
at
840
of
rates.
for
umol
from
1040
grown
similar
or
trend,
had
to
rates
Leaves this
is
and
510
did
mol -I.
CO 2
limiting
trend a
PPF
tended
Leaves
photosynthetic
was
-I
maximum
At
plants
mol
of
similar
level
different
was
PPF
4).
than
from
CAR
a
umcl
higher
PPF
a
at
levels
CO 2.
(Fig.
PPF
leaf
that
at
-I
showed
CO 2
PPF
i.e.
mol
1290
umol
i.e.
But
mol
500
lower
levels,
umol
lower
indicates
and
1040
CO 2
to
at
occurred,
mol -I
umol
from
levels
to
concentration
the
CO 2
saturation
raising
tended
at
saturated.
increased
occurring
(Fig
CAR low
umol
at
CO 2
grown
plants
Leaf
up
increased
when
of
CO 2
i000
saturation CAR
for
was
even at
CO 2
relatively
achieved, grown
increasing
CO 2
effect
comparison
different
CO 2
combinations
of
6).
DISCUSSION
The in
the
CO 2
reduce
healthy from
no
capacity
with adverse (5).
regardless
similar
soybean
leaves
other
species
have
effects, From
in
a
and CELSS
(Fig. which with
shown even
that
97
on 6). CO 2
time
CO 2 in
carbon
concentration the
contrasts
enrichment (4).
tends
But
long-term
atmospheric
assimilation
This
increased
perspective,
the
changes
effects
capacity
soybeans
of
transient
have
photosynthetic
studies
that
environment,
irradiance of
findings
suggest
"native"
and
rates
had
results
CO 2
recent
with to field
enrichment
photosynthetic it
is
noteworthy
that
the effects
of transient
changes on soybean CARcan be predicted
independent of the crop's serve as useful life
prior
history.
models for testing
support module.
transient
However, this
exchange measurements closely
Thus, leaf
reflect
systems may
changes in a closed
presumes that single-leaf
gas
community gas exchange,
which remains to be tested. A comparison of CARcurves from Fig. is no advantage to raising that levels
greater
supraoptimal.
5 indicates
there
the CO2 much above i000 umol mol-I and
than this
(e.g. 2000 umol mol-I)
The drop in photosynthetic
may be
rates by increasing
from i000 to 2000 umol mol-I may be a result inhibition,
that
of some feedback
e.g. excessive starch accumulation
in leaves
(6,7).
Aside from determining
the optimum environment for photosyn-
thesis,
be useful
such data will
where plants or levels (e.g.
CO2
for the purposes of a CELSS,
may be subjected to transient
changes in CO2 levels,
much higher than have been traditionally
studied
>I000 umol mol-l). Because the plants
were all
s-1, we can only speculate
grown at a PPF of 300 umol m-2
on the effects
environment might have on photosynthetic likely
that the lighting
than the CO2 history chlorophyll
history
from this
umol
mol
-I
the
light
or
because of irradiance
a point
PPF
of for
840
structure
soybean
98
umol
leaves.
It
is
on leaf
(8).
CO 2
m -2
lighting
leaves differently
effects
study did show that when
greater,
saturation
capacities.
would affect
content and chloroplast
results
that a native
levels
s -I
was
However were still
440 below
REFERENCES I. Tibbitts,
T.W. and D.K. Alford.
1982.
life 2231.
support
system.
Use
plants.
Mackowiak,
C.L.,
R.M.
2.
1989. Effects concentrations a 3.
Coombs,
Oxford, 4.
D.O.
in
W.
Controlled NASA
Lowery,
atmospheric carbon and acid requirements
hydroponic J.,
higher
Wheeler,
of elevated on water
recirculation
Techniques
of
system.
Hall,
S.P.
(This
Long,
bioproductivity
and
and
ecological Conference
and
J.C.
Pub.
Sager.
dioxide of soybean
grown
J.M.O.
Scurlock.
photosynthesis.
1985.
Pergamon
Press,
England.
Peet,
Acclimiation exchange
M.M.,
S.C.
to rates,
Huber,
and
D.T.
Patterson.
high CO 2 in monoecious enzyme activities, and
concentrations.
Plant
Physiol.
1986.
cucumbers. starch and
II. Carbon nutrient
80:63-67.
5. Campbell, J.W., L.H. Allen, and G. Bowes. 1988. Effects concentration on rubisco activity, amount, and photosynthesis soybean leaves. Plant Physiol. 88:1310-1316. 6.
in
issue).
Ehret,
D.L.
plants grown 63:2015-2020.
and in
7. Sasek, Reversibility
T.W.,
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exposure
of
8. Boardman, shade plants.
P.
carbon
A.
Jolliffe.
dioxide
E.H. DeLucia, photosynthetic
N.K. Ann.
to
1977. Rev.
1985. enriched
and
elevated
Leaf
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injury
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CO 2 in
bean
Can.
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99
to
atmospheres.
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J.
Bot.
after
Plant
of
Physiol.
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