lettuce and sugar beets in thefield
and injected a mixture of gases
(common in geothermal emissions)
at various concentrations through
the bottom of the chambers
(Fig. 1). Each chamber maintained
a constant exposure condition for a
period of several hours, and during
making these measurements in the
field.
We found that geothermal air
carbon dioxide fixed per gram of .
emissions actually stimulate
leaf tissue per hour) and the
resistance of leaf pores (stomata) to photosynthesis at low concentrathe diffusion of gases into the leaf tions (see Fig. 2) because the addition of carbon dioxide and
(inverse conductance, i.e., s/cm}.
We have pioneered techniques for hydrogensulfide provides elements
needed for carbohydrate and
amino acid production. Thefirst
significant decrease in
photosynthesis occurred when the
concentration of hydrogen sulfide
exceeded about 3 ppm
(4200 g/m?) in the mixture. This
value is two orders of magnitude
that period we measured the rate
of photosynthesis (milligrams of
ACO, concentration — ppm
25
5
Trt
TT
Cross
photosynthesis
20 ;—
sing co 3/9- h)—
15 | photosynthesis MK
control
10 —
90
—
~~
2
Leaf stomatal resistance
5 om Lb ae
Control
(s/em)}
ontro
0
0.3
teppriil
Hos
1
4
4
ot
3
concentration — ppm
6
JRA 4 G)
Photosynthesis rates
(Qi.
(mg COz/g-h) and
stomatal resistance (s/cm)in lettuce exposed (for 3h at 30°C and
high light) to a mixture of gases
similar to that emitted by geothermal power plants. Geothermal
emissions actually stimulate
ra Hes
‘ne aed
I
Open-topped chambers used to measure the reactions of plants
Qiil
é
to hydrogen sulfide and other gases. Potential air pollutants are
injected in various concentrations into the bottom of the chamber. Each chamber maintains a constant exposure condition for a period of several hours, during which researchers make physiological measurements to evaluate effects on
the plant's metabolism.
~
Cn
cg
Ne
Oa
ay
a
cm
5
24
photosynthesis at low concentra-
tions because the additional carbon
dioxide and hydrogen sulfide
provide essential elements for carbehydrate and amino acid produc-
tion. The first significant decreasein
photosynthesis occurs when
hydrogen sulfide exceeds about
3ppm in this mixture.