EPA 600 3-7'
)79
&EPA
A Gas-Exchange
System for
Assessing Plant
Performance in
Response to
Environmental
Stress
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6, Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-79-108
October 1979
A GAS-EXCHANGE SYSTEM
FOR ASSESSING PLANT PERFORMANCE IN
RESPONSE TO ENVIRONMENTAL STRESS
by
G. E. Taylor, Jr.
National Research Council Postdoctoral Research Associate
Con/all is Environmental Research Laboratory
Corvallis, Oregon 97330
and
D. T. Tingey
Terrestrial Division
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
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DISCLAIMER
This report has been reviewed by the Corvallis Environmental Research
Laboratory, U. S. Environmental Protection Agency, and approved for publi-
cation. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
n
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FOREWORD
Effective regulatory and enforcement actions by the Environmental
Protection Agency would be impossible without sound scientific data on pollu-
tants and their impact on environmental stability and human health. Respon-
sibility for building this data base has been assigned to EPA's Office of
Research and Development and its 15 major field installations, one of which is
the Con/all is Environmental Research Laboratory (CERL).
The primary mission of the Corvallis Laboratory is research on the
effects of environmental pollutants on terrestrial, freshwater, and marine
ecosystems; the behavior, effects and control of pollutants in lakes and
streams; and the development of predictive models on the movement of pollu-
tants in the biosphere.
The performance of plants in pollution-stressed natural and agro-
ecosystems is a concern of the Corvallis Laboratory. This report describes an
experimental laboratory system designed to assess how pollutants may affect
plant growth and productivity. The adaptability of the system makes it appli-
cable to a wide range of research efforts focusing on the response of vege-
tation to either soil or atmospheric pollutants.
Thomas A Murphy
Director, CERL
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ABSTRACT
Anthropogenic stresses are increasingly common as environmental factors
affecting the performance of plants in both natural and agro-ecosystems.
There is a need to determine how these stresses may influence vital physio-
logical processes in plants. This report documents the design, construction
and performance of a whole-plant, gas-exchange system that can accurately
monitor gas flux (e.g., carbon dioxide, water vapor, pollutants) between
plants and the atmospheric environment. From these data, rates of key physio-
logical processes - photosynthesis, transpiration, gaseous uptake and emis-
sion - can be assessed. Example studies are reported on the uptake of sulfur
dioxide by plants and emissions of monoterpenes from plants.
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CONTENTS
Foreword --------- — ___ — _ — ___ — ________ -j
Abstract -------------------------------- jv
1. Introduction ------------------------- i
2. Gas-Exchange System ---- — ______ — ________ ]
3. Performance of the Gas-Exchange System ------------ 5
4. Gas-Exchange System in Operation ----- — _-_-___- 7
5. Conclusions — -- — ---_--____ — ________ ^5
References ---- — -- — ________ — ___________ 17
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INTRODUCTION
Gases such as carbon dioxide and water vapor are key constituents in many
plant physiological processes. The influx of carbon dioxide from the atmos-
phere into the leaf is required for photosynthesis, and the efflux of water
vapor during transpiration helps dissipate heat build-up within the leaf.
This gaseous exchange process between a plant and its environment is inti-
mately associated with the plant's physiological status. Therefore, the study
of gas flux provides an experimental means of assessing the physiological
performance of plants.
Irrespective of the direction of flow, gas movement between leaves and
the surrounding atmosphere is a consequence of diffusion. Net flux (J) or
rate that a gas (i) is emitted or absorbed is proportional to the ratio of the
steepness of the concentration gradient (AC) to distance (x.) over which
diffusion occurs. ""
J. = DiAC./xi. (1)
D- is the diffusion coefficient of the gas and is a function of the molecular
weight and diffusion medium (Nobel 1974). Since the driving force of gas
exchange is the concentration gradient, any gas exhibiting a concentration
differential will tend to diffuse along the gradient, and this movement occurs
irrespective of the physiological importance of the gas to the plant. In
addition to the concentration gradient, gas flux is regulated by resistances
(R) along the diffusion pathway. Incorporating this component into Equation
(1) yields the following:
Ji = AC^ (2)
This relationship, depicted in Figure 1, is a basis for understanding the
gas-exchange process in plants (Gaastra 1959).
It is possible to assess the rates of net photosynthesis and trans-
piration with an analysis of carbon dioxide and water vapor fluxes. Further
analysis, coupled with appropriate experimental design, can relate changes in
carbon dioxide and or water vapor flux to corresponding changes in leaf resis-
tance components, including boundary layer (R ), stomatal (R_), and residual
3 S
(Rr). With these capabilities the researcher can monitor the effects of
varied environmental conditions (gaseous pollutants, water stress, toxics,
light, temperature, etc.) on the plant, with an objective of addressing how
each affects specific physiological processes. The purpose of this research
was to design, fabricate and test a gas-exchange system that could perform
these functions.
GAS-EXCHANGE SYSTEM
The gas-exchange system (Figure 2) is designed to assay quantitative
changes in gas composition that result from plant activity; the system is
based upon the theory of mass balance of gases. This approach requires quan-
tification of each of the three fates of a gas entering the chamber: (i)
1
-------
rv>
CONCENTRATION GRADIENT
JS02=DS02ACSO/A*
Sink Concentration (Cj)
Distance
Surface Flux
Source Concentration (Ca)
RESISTANCE TO FLUX
Mesophyll (Residual)
Stomate (R|°2)
Boundary Layer (Rg°2)
Figure 1. Diagram illustrating the factors affecting the flux of gases between a leaf and its environment.
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1
Pure
Air
Source
coe
Scrubber
co
Bypass
Metering
Valves
CO*
Controlled Environment Chamber*
I
Gas - Exchange
Chamber
I J
Flowmeter
Sample
Port
Infra red
Analyzer
Recorder
Flowmeter
Drierite
Recorder
Figure 2. Diagram of the gas-exchange system.
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adsorption to the chamber walls and equipment, (ii) reaction (adsorption and
absorption) with the plant, and (iii) exit by the outlet. By knowing the
inlet and outlet mass of the gas plus the loss rate to the chamber (via
experimentation), the mass reacting with the plant can be determined.
The flux of any gas can be modeled as follows (Sestak, Catsky and
Jarvis, 1971):
J = (F x C)/n (3)
where J = flux of gas to the plant,
F = flow of air through the chamber,
C = change in gas concentration between the chamber inlet and
outlet,
n = leaf area.
The model is applicable to gas being taken up (e.g., carbon dioxide and sulfur
dioxide) as well as that diffusing out of the leaf (e.g., water vapor and
hydrocarbons).
A schematic of the gas-exchange chamber is shown in Figure 3. The cylin-
drical, plexiglass unit consists of two compartments partitioned by a hori-
zontal, removable baseplate. The lower compartment houses the plant pot and
root mass, and the upper unit encloses the above-ground vegetation. The
baseplate is sectioned through the diameter with a small opening that allows
the two halves of the plate to encircle the stem so that the above- and below-
ground plant parts are isolated. Any cracks or openings are sealed with
modeling clay, thus completely separating the two compartments. The geometry
of the respective compartments is specified in Table 1,
TABLE 1. DIMENSIONS OF EXPERIMENTAL GAS-EXCHANGE CHAMBER
Compartment Diameter (m) Height (m) Volume (m3) Height/Diameter
Upper Compartment
Large Unit
Small Unit
Lower Compartment
0.375
0.375
0.260
0.415
0.155
0.240
0.046
0.017
0.013
1.11
0.41
0.92
The chamber is supported in a plexiglass frame as shown in Figure 3.
Many features of the upper compartment are incorporated to optimize rapid
mixing of the air mass so that stratification and pocketing are minimized.
Engineering theory (Rogers et a_K 1977) suggests that instantaneous mixing is
achieved in a cylindrical enclosure in which the height:diameter ratio does
not exceed 2. Chamber dimensions for the two upper compartments (Table 1),
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1. OUTLET PORT
2. LEAF TEMPERATURE SENSOR
3. EXHAUST PORT
4. TEMPERATURE SENSOR
5. FAN
6. HEATING ELEMENT
7. LIGHT SENSOR
8. PRESSURE GAUGE PORT
9. THERMOCOUPLE WIRES
10. INLET PORT
TEMPERATURE CONTROLLERS
Figure 3. Diagram of the gas-exchange chamber.
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which were dictated by plant size and physical constraints of the controlled
environment chamber, provide a ratio of 1.11 and 0.41. Turbulence is created
by two devices. First, six impeller blades rotated by a variable speed elec-
tric motor (outside the chamber) rapidly mix the incoming air with the exist-
ing air reservoir. Second, three vertically-arranged baffles (2.5 cm high)
are aligned equidistant around the sides of the chamber. Several ports in the
floor of the upper and lower chambers provide access for inlet and outlet air
lines as well as equipment probes. The construction of the lower compartment
is identical to the upper one except for the height:diameter ratio and the
absence of wall baffles.
Air flow into the chamber is regulated by variable flow rotameters. Air
temperature regulation is provided by a floor-mounted, temperature sensor and
heating pole integrated to a proportioning controller (Love Controls Corp.,
Model 49). Since the system requires continuous positive pressure, a dif-
ferential pressure gage is plumbed to the chamber and mounted on the housing
cabinet. Air temperature is monitored by a temperature probe mounted at the
chamber outlet and shielded from incident light. Light irradiance is moni-
tored at canopy level (Lambda Instruments Co., Inc., Quantum Sensor, Model
LI-105). All wavelengths of visible light are transmitted equally through the
chamber ceiling and walls; however a uniform reduction of 8% at each wave-
length occurs (Rohm and Haas, Inc.). Leaf temperature is monitored contin-
uously with an ui situ thermocouple as described by Lange (1965), and temper-
ature (±0.2°C or °F) is reported on a multi-point digital thermometer (Omega
Engineering, Inc. , Model 2176A with Analog Processor) and recorder.
All gas lines are 1/4-inch stainless steel or copper tubing. Ambient air
is pumped through a reactor (AADCO 737 Series Pure Air Generator) which pro-
duces pressurized, clean air (Figure 2). At several locations along the inlet
air lines, ports are provided for bleeding in gas mixtures such as carbon
dioxide, pollutants or dry and moist air. A series of regulatory valves
situated in the lines prior to the gas-exchange chamber permit manual redirec-
tion of the gas flow so that alternative flow of inlet and outlet sample air
to the analyzers can be achieved. When required, syringe ports are placed in
the gas lines at the chamber's inlet and outlet. Air is forced through a
dewpoint and temperature water bath system in which varying dewpoint levels
are achieved by changing the temperature of the water bath or by mixing humid
with dry air.
The quantitative analysis of gas stream composition between inlet and
outlet air is the basis of the gas-exchange system. The choice of specific
analyzers is dictated by the objectives and will likely vary between experi-
ments; consequently discussion of individual analyzer units is not provided.
PERFORMANCE OF THE GAS-EXCHANGE SYSTEM
The gas-exchange system requires instantaneous mixing so that composition
of all aliquots of the air reservoir are equivalent. This criterion is as-
sessed using first order chemical reaction kinetics (Rogers et al_. 1977). The
time for an outlet concentration (e.g., 350 ppm C02) of a chamber gas to
decrease to a specific value (given an inlet concentration of 0) is monitored
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experimentally and compared with that predicted from theory. The expected
time is derived from the following equation:
Ct = C. (1 - e"Qt) (4)
1 Lo
where C. = the outlet gas concentrations after some time t,
C. = initial outlet gas concentration at time t
o
Q = I/residence time or the ratio of flow to volume.
Solving for t,
t = -In (1 - C./C. )/Q. (5)
1 o
If the gas-exchange system exhibits instantaneous mixing, time calculated
from the above equation will approximate that observed under experimental
conditions. This test (using C02 as the test gas) was performed in an empty
chamber (large upper compartment) at six different flow rates ranging from 2
to 6 1 min-1 with a dewpoint and chamber temperature of 4.5 and 26.7°C,
respectively.
Irrespective of flow rate, the profile of carbon dioxide decay within the
chamber is an inverse function of flow rate (Figure 4A). A linear regression
analysis (Figure 4B) of observed versus expected times accounts for 95% of the
variation, and the slope (1.14) is not statistically different from 1.0. This
suggests that instantaneous mixing is achieved.
GAS-EXCHANGE SYSTEM IN OPERATION
Two examples of studies utilizing the gas-exchange system are reported:
(i) flux of gaseous pollutants to plants and (ii) the emission of monoterpenes
from plants.
FLUX OF GASEOUS POLLUTANTS
Populations of Geranium carolinianum, a winter annual weed, vary in their
foliar response to acute sulfur dioxide (S02) exposure, and population dif-
ferences are genetically controlled (Taylor 1978). Flux of sulfur dioxide to
plants was monitored to determine whether pollutant resistance is associated
with reduced S02 uptake into the plant. Seeds were germinated and seedlings
grown in a Jiffy Mix: Perlite (1:2;V:V) mixture. Plants were cultured in a
greenhouse with maximum day/night temperatures of 28° and 20°C, respectively.
The photoperiod was extended to 16 hours per day. A modified Hoagland's
nutrient solution (1/2 strength) was applied daily. At least two weeks prior
to experimentation, plants were transferred to a growth chamber having an
environmental regime similar to that of the gas-exchange chamber (see legend,
Figure 6).
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00
o
CD
o:
<
o
Figure 4A.
600
500
400
300
o:
h-
UJ
o
o
o
LU
9 200
X
g
Q
100
0
Figure 4A
\
_ \
\
\>
90
— 70
Q
LU
I 50
CO
GO
O
UJ 30
0
y = -7.l2+M4(x)
r=0.95
Figure 4B
0 30 50 70 90
TIME EXPECTED (min)
110
o——o n
o
0
10
20 30
TIME (min)
40
50
Carbon dioxide decay rate within the chamber
given an air flow rate of 4.5 1 min-1 and
initial outlet and inlet C02 concentrations
of 365 and 0 ppm, respectively.
Figure 4B. Relationship between observed and
expected time for outlet C02 concen-
trations to approach 0 ppm at varying
flow rates.
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In using the mass balance approach to analyze gaseous exchange, the vari-
ous fates of S02 molecules entering the chamber must be quantified. The
potential of chamber surfaces to serve as a sink for various gases depends
upon the humidity of the chamber air since any surface water film adhering to
the walls will scavenge water-soluble pollutant molecules. To assess this
sink potential, an artificial transpiration system was designed to inject
continuously a known volume of moist air. Inlet and outlet lines were moni-
tored for S02 and water vapor concentrations, and the latter was varied by
regulating manually the volume of steam injected. The expected outlet con-
centration of S02 was determined by calculating the dilution effect of the
steam air on the S02 entering the chamber, and any discrepancy between expec-
ted and observed sample line concentrations was attributed to pollutant
adsorption to the chamber walls.
As the sample dewpoint increased, the adsorption of S02 to the chamber
increased linearly (Figure 5). Using linear regression analysis this rela-
tionship is expressed as:
chamber loss = 2.42 DPQUT - 26.32
where chamber loss = percentage of the total S02 concentration
differential reacting with the chamber interior and
DPOUT = the Out1et dewP0int in °C.
Although the S02 loss to the chamber at lower dewpoints is small, the per-
centage adsorbed at higher levels may exceed 20%. Consequently, the chamber's
capacity to scavenge S02 molecules must be incorporated into the data analysis
in order to assess accurately S02 flux to the plant.
Total leaf flux of S02 is the sum of loss to the leaf surface (adsorp-
tion) and leaf interior (absorption), and it is important to quantify the
significance of each since S02 absorption is responsible for foliar necrosis.
Plants were exposed to 0.4 ul I-1 S02 (outlet concentration) in the dark for
three hours (adequate to achieve a S02 steady state flux). This exposure
regime was followed by an equivalent S02 concentration (outlet S02 level of
0.4 pi I-1) after the lights were turned on. The pollutant dose was not
sufficient to cause visible leaf injury. Concurrent measures of dewpoint and
leaf temperature were recorded so that leaf resistance to water vapor flux
could be calculated (Nobel 1974). Following this protocol, the plant was
removed and uni facial leaf area measured. With these data, values were ob-
tained for steady state S02 flux to the plant (ug m-2 hr-1) and concurrent
leaf resistances (sec cm-1) to water vapor and S02 flux for each plant in both
light and dark. The S02 flux data incorporated appropriate calculations to
exclude that fraction of the pollutant lost to the chamber walls.
For all plants the pattern of leaf resistance and the flux of S02 to the
plant throughout the night-day exposure regime was similar; an example is
shown in Figure 6. In the dark, total leaf resistance to S02 flux remained
constant (30 sec cm-1) and with light, decreased precipitously to a lower
steady state value (4 sec cm-1). This response pattern, showing distinct dark
and light plateaus, is mirrored by total leaf flux of S02, which exhibits
-------
X
h-
30
O 25
to ;f; 20
10
UJ O 5
0 I
0
O
y =-26.32+2.42x
r = 0.98
O
0 13 14 15 16 17 18 19 20
OUTLET DEW POINT (°C)
•21
22
Figure 5.
Influence of outlet dewpoint on S02 flux to the chamber's internal surface and equipment. The
chamber conditions were equivalent to the day environmental regime described in the legend to
Figure 6.
-------
Figure 6.
\J,\J
J^
'v. 2.0
CM
'E
H
^^»
^ 1.0
1
1
1 ,
U_
CM
O
C/)
o
i i i I i I
A
I I _
—
r'
Photoperioc
Initiation
I /
i *
i /
i /
I/
17
\t
f
A
/i
/I
/I
i i
/ 1
^ i
i *
^*— •--•
i i i t i 1
15.0
1
1
1
—*
'E -
10.0 o
o
a>
t/)
O
CVJ
T* |
a:
5.0
n J
30.0
1
1
1
_^
20.0 'E
o
o
CD
to
CM
O
CO -I
a:
10.0
n
1200 1300 1400 1500 1600 1700 1800
TIME (hr)
6. Relationship of S02 flux and leaf resistance to water vapor flux (R^*0) and S02 flux (RLS°2)
as a function of time in the dark and light. Chamber conditions in the day and night environ-
ments were: air temperature = 27°C, inlet C02 concentration = 320-345 |jl I-1 and outlet S02
concentration = 0.4 ul I-1. Light irradiance during photoperiod was 490 uE m-2 sec-1.
-------
steady state uptake rates of 0.8 and 2.5 (ug m-2 hr-1 in the dark and light,
respectively).
Total S02 flux and leaf resistance at steady state for each plant under
both light and dark conditions are plotted with S02 flux as the dependent
variable (Figure 7). Total pollutant flux to the plant, including both ad-
sorption and absorption, is related inversely to leaf resistance and is asymp-
totic at both leaf resistance extremes. Consequently, S02 flux into the leaf
decreases with increasing leaf resistance. Using linear regression analysis
of the log-transformed values for each variable, a model .for S02 flux as a
function of leaf resistance in both sensitive and resistant plants was devel-
oped (Figure 8). Respective regression lines and slopes for resistant and
sensitive plants do not differ statistically. These results indicate that
given equivalent leaf resistance values for gaseous flux, S02 resistant and
sensitive plants do not differ in the leaf uptake of the pollutant.
Analysis of total leaf flux of S02 shows that under conditions promoting
absorption into the leaf (i.e., light), the percentage of the total S02 flux
lost to the leaf surface is approximately 20%. This determination is derived
from a comparison of the asymptotic S02 flux values at high versus low leaf
resistances (Figure 7) and assumes that the capacity of the leaf surface to
extract S02 is constant and unaffected by the opening of the stomates.
HYDROCARBON EMISSIONS FROM PLANTS: EFFECT OF TEMPERATURE
The specific objectives of this study were (i) to identify specific
monoterpenes being emitted by a species of pine, (ii) to determine monoterpene
emission rates under rigidly controlled environments, and (iii) to assess how
leaf temperature affects the emission rate. A detailed report of this project
is available (Tingey et al_. 1978).
Seedlings of slash pine (Pinus elliotti) were grown in a greenhouse and
transferred, at least four weeks before experimentation, to a controlled envi-
ronment chamber similar to that in which the gas-exchange chamber was housed.
The gas-exchange system was modified slightly to accommodate analysis of
hydrocarbons by gas chromatography. Syringe ports were placed in both inlet
and outlet lines so that air samples of 25- to 50-ml could be collected with
gas-tight syringes. Samples were injected into a gas chromatograph designed
to cryogenically concentrate, separate and quantify the levels of monoter-
penes. After experimentation each plant's needles were oven-dried and assayed
for dry weight. The data were analyzed using regression techniques, and the
results are presented graphically. Since emission rates were log-normally
distributed, the data were transformed to logarithms for calculation (Tingey
etaJL 1978).
Qualitatively, five monoterpenes were identified in the outlet air (par-
enthetical data are average emission rates in ug C/gm dry wt/hr at 35°C):
crpinene (4.46), p-pinene (3.44), myrcene (0.32), limonene (0.06) and
p-phellandrene (0.22). Leaf temperature exerted demonstrable effects on the
rate of monoterpenes emitted (Figure 9). The data for the sum of the five
monoterpenes (Figure 9A) show a log-linear relationship between emission rate
12
-------
3.0
«* 2.0
E
X
CVJ
O
1.0
0
0
Sensitive Plar>tso
' 1
'Resistant Plants'
o^
• •
2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0
(secern"1)
5.0 10.0
15.0 20.0 25.0 30.0
(sec cm"1)
35.0 40.0
Figure 7. Relationship between leaf resistance to gaseous flux (RL 2 and RL 2 ) and S02 flux to
the plant in both S02 resistant and sensitive plants.
-------
3.0
2.0
~"L
_c
CM
'E
S L°
x 0.8
CVJ
O
CO
0.6
0.4
O.I
1.0
I I I I I
s
RESISTANT PLANTS
) LOG|0(S02 FLUX) = 0.85-0.77(LOG,0R^°2)
-/ r = -0.90
SENSITIVE PLANTS
=0.95-0.91 (LOGIC)RL 2)
= -0.92
I
I I I I
5.0
10.0 20 30
R^°2 (secern"1)
40 50 60 70
Figure 8. Regression analysis depicting linear relationship between Iog10
(leaf resistance) and Iog10 (S02 flux) for S02 resistant (n = 44
and S. = 0.071) and S02 sensitive (n = 36 and Sfa = 0.083) plants.
14
-------
100
50
10
5
O
o>
d>
I
LJ
5
CC
CO
CO
LJ
LJ
LJ
0_
LJ
O
0.5
O.I
0.05
0.01
100
I I
Z| monoterpenes
log y=-O.I44+0.032(C°)
R2=0.92
j I
-B
ct-Pinene
log y=-0.369+0.029(0°)
R2 = 0.90
jQ-Pinene
log y=-0.633+0.033(0°)
R2 = 0.90
Sol- D
Myrcene
10
5
0.5
O.I
0.05
0.01
logy=-l.65l+0.033(C°)
R2 = 0.82
-E
Limonene
log y=-l.93l+0.032(C°)
R2=0.7I
I I
j9-Phellondrene
log y=-1.645+0.028(0°)
R2 = 0.83
I I
20 30 40 50 20 30 40 50 20 30 40 50
NEEDLE TEMPERATURE-°C
Figure 9. The influence of varying temperatures on monoterpene emission rates
in slash pine.
15
-------
and temperature so that the mean value increased exponentially with temper-
ature. As temperature increased from 20 to 46°C, the rate of the sum of
monoterpenes emitted increased from 3 to 21 ug C/g dry wt/hr. The regression
equation accounted for 92% of the observed variation (Figure 9A).
CONCLUSIONS
The objective of this research was to establish a gas-exchange system
capable of assessing indices of physiological activity that are closely linked
to overall plant performance. Two types of data are presented to support
this objective. First, the performance trials show that the system conforms
to necessary design criteria of gas conditioning, delivery, instantaneous
mixing and monitoring. Second, the results of two studies, measurement of S02
uptake and hydrocarbon emissions, indicate that with appropriate experimental
designs, research can evaluate the effects of the environment on vital gas-
exchange processes in plants.
16
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REFERENCES
Gaastra, P. 1959. Photosynthesis of crop plants as influenced by light,
carbon dioxide, temperature and stomatal diffusion resistance. Meded.
Landbhoogesch. W'ageningen. 13:1-68.
Lange, 0. L. 1965. Leaf temperatures and methods of measurement. Jji:
Methodology of Plant Ecophysiology, Proceedings of the Montpellier
Symposium, F. EcKardt (ed.). UNESCO, pp 203-209.
Nobel, P. 1974. Biophysical Plant Physiology. W. H. Freeman and Company,
San Francisco.
Rogers, H. H., H. E. Jeffries, E. P. Stabel, W. W. Heck, L. A. Ripperton and
A. M. Witherspoon. 1977. Measuring air pollutant uptake by plants: a
direct kinetic technique. Air Pollut. Control Assoc. 27:1192-1197.
Sestak, Z. , J. Catsky, and P. G. Jarvis. 1971. Plant photosynthetic produc-
tion. Manual of Methods. Dr. W. Junk, N. U. Publ., The Hague.
Taylor, G. E., Jr. 1978. Genetic analysis of ecotypic differentiation of an
annual plant species, Geranium carolinianum L., in response to sulfur
dioxide. Bot. Gaz. 139(3):362-368.
Tingey, D. T., M. Manning, H. C. Ratsch, W. F. Burns, L. C. Grothaus and R. W.
Field. 1978. Monoterpene emission rates from slash pine. U.S. Environ-
mental Protection Agency, Corvallis Environmental Research Laboratory,
Corvallis, Oregon. CERL-045.
17
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-79-108
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
A Gas-Exchange System for Assessing Plant Performance
in Response to Environmental Stress
5. REPORT DATE
Qc.tob.er 1979 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
G.E. Taylor, Jr.
D.T. Tingey
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
1. National Research Council
2. Terrestrial Division
Corvallis Environmental Research Laboratory
10. PROGRAM ELEMENT NO.
1AA602
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Corvallis Environmental Research Laboratory
Office of Research & Development
U.S. Environmental Protection Agency
Corvallis, OR 97330
13. TYPE OF REPORT AND PERIOD COVERED
inhouse
14. SPONSORING AGENCY CODE
EPA/600/02
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Anthropogenic stresses are increasingly common as environmental factors
affecting the performance of plants in both natural and agro-ecosystems. There
is a need to determine how these stresses may influence vital physiological
processes in plants. This report documents the design, construction and
performance of a whole-plant, gas-exchange system that can accurately monitor
gas flux (e.g., carbon dioxide, water vapor, pollutants) between plants
and the atmospheric environment. From these data, rates of key physiological
processes-photosynthesis, transpiration, gaseous uptake and emission-can be
assessed. Example studies are reported on the uptake of sulfur dioxide by
plants and emissions of monoterpenes from plants.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Environmental Simulator
Plant Physiology
Gas-Exchange System
06/F
8. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
unclassified
21. NO. OF PAGES
24
20. SECURITY CLASS (This page)
unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
18
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