Direct and Indirect Stomatal Responses to Light. A concentration
of l0-` M cyanazine in the irrigation water of leaves of X
strumarium and G. hirsutum reduced photosynthesis to the compensation
point within 2 h. At that time, net exchange of CO2 did
not occur or was so small that it could not be measured. The CO2
concentration in the intercellular spaces ofthe leaves was therefore
equal to the CO2 concentration in the air around the leaves, and
a change in irradiance could not cause a change in the intercellular
CO2 concentration. Stomata of X strumarium appeared not to be
affected by cyanazine while those of G. hirsutum became more
sensitive to CO2 (Fig. 1). In leaves of X strumarium, Atrazine and
DCMU also eliminated' the net exchange of CO2 without affecting
the stomatal response to CO2. Inhibitors of photosynthesis could
not be used to study stomatal responses to light in Z. mays and C.
communis because higher concentrations than 10-r M had to be
supplied in order to reduce the net exchange of CO2 to zero within
2 h. The leaves began to evolve CO2 during the course of the
experiments and, as a consequence, the intercellular CO2 was no
longer independent of changes in stomatal conductance. Stomata
of X strumarium and G. hirsutum clearly responded to irradiance
in the presence of cyanazine (Figs. 2, 4-6, 8). The magnitude of
the direct response to irradiance derived from the data thus
obtained plus data on the stomatal sensitivity to CO2 and the
response of assimilation to light and CO2 were used to evaluate
equation (5) derived under "Materials and Methods." Table I
shows how conductance and assimilation changed with infmitesimal
changes in irradiance at irradiance levels of 50 and 300 w
m-2, with the intercellular CO2 concentration maintained at 250
,ul 1-1. In X strumarium, the direct stomatal response to irradiance
accounted for 79% of the total response at 50 w m-2 and for 55%
Direct and Indirect Stomatal Responses to Light. A concentrationof l0-` M cyanazine in the irrigation water of leaves of Xstrumarium and G. hirsutum reduced photosynthesis to the compensationpoint within 2 h. At that time, net exchange of CO2 didnot occur or was so small that it could not be measured. The CO2concentration in the intercellular spaces ofthe leaves was thereforeequal to the CO2 concentration in the air around the leaves, anda change in irradiance could not cause a change in the intercellularCO2 concentration. Stomata of X strumarium appeared not to beaffected by cyanazine while those of G. hirsutum became moresensitive to CO2 (Fig. 1). In leaves of X strumarium, Atrazine andDCMU also eliminated' the net exchange of CO2 without affectingthe stomatal response to CO2. Inhibitors of photosynthesis couldnot be used to study stomatal responses to light in Z. mays and C.communis because higher concentrations than 10-r M had to besupplied in order to reduce the net exchange of CO2 to zero within2 h. The leaves began to evolve CO2 during the course of theexperiments and, as a consequence, the intercellular CO2 was nolonger independent of changes in stomatal conductance. Stomataof X strumarium and G. hirsutum clearly responded to irradiancein the presence of cyanazine (Figs. 2, 4-6, 8). The magnitude ofthe direct response to irradiance derived from the data thusobtained plus data on the stomatal sensitivity to CO2 and theใช้เพื่อประเมินการตอบสนองของผสมแสงและ CO2สมการ (5) ที่ได้มาภายใต้ "วัสดุและวิธีการ" โต๊ะผมแสดงวิธีการเปลี่ยนแปลงของการนำพาและผสมกับ infmitesimalการเปลี่ยนแปลงใน irradiance ระดับ irradiance 50 และ 300 wm-2 กับความเข้มข้น CO2 intercellular ที่ 250, ul 1-1 ใน X strumarium การตอบสนองต่อ stomatal ตรง irradianceคิดเป็น 79% ของการตอบสนองรวมที่ 50 w m-2 และ 55%
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