ANALYSIS OF HEAT BALANCE OF LEAF WITH REFERENCE TO STOMATAL RESPONSES TO ENVIRONMENTAL FACTORS

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The heat balance of the intact cucumber leaf was examined by measuring leaf temperature and environmental factors, and transpiration rate and leaf conductance were calculated in course of time. When the leaf was radiated, leaf temperature, transpiration rate and leaf conductance rose rapidly and thereafter varied with the air conditions. Air temperature and saturation deficit affected the amplitudes of leaf conductance oscillation (period of 25-30 min); the amplitudes were larger at lower air temperatures and at higher saturation deficits. The saturation deficit influenced stomatal behaviour directly through change in vapour density difference (⊿w) between inside of the leaf and the air, and stomatal response to air humidity was found in the physical process. However, the air temperature did not relate to ⊿w, as ⊿w was almost constant even when the air temperature was changed, for the reason that saturation vapour density inside of the leaf increased exponentially with temperature rise in the leaf. Thus, it seems that stomatal response to air temperature could not be caused directly through the physical process, but could be caused mainly through the physiological functions.
九州大学の論文