N91-3i780 - NTRS - NASA

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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

B.R. Strain. inhibition in

CO 2

injury

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CO 2 in

bean

Can.

1985. cotton

Comparative photosynthesis Plant Physiol. 28:355-377.

99

to

atmospheres.

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Bot.

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