HYDROACTIVE AND HYDROPASSIVE MOVEMENTS OF STOMATA RESPONDING TO VISIBLE AND INFRARED RADIATIONS

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Movements of stomata responding to visible and infrared radiations were analyzed in an intact cucumber leaf by applying an improved heat balance method for evaluation of transpiration rate and leaf conductance. In step response to the visible radiation, photosynthetically active radiation (PAR) induced dynamics of water balance in the whole leaf through osmotic change in guard cells and mesophyll, and resulted in hydroactive stomatal oscillation with a natural period of about 30 min at the higher radiant intensities. In the infrared radiation, leaf-air vapor density difference (W_L-W_A) was rapidly raised by the thermal effect of the radiation, and subsequently rapid increase in the peristomatal transpiration caused hydropassive stomatal opening through hydraulic interaction between guard cells and adjacent epidermal cells. This hydropassive stomatal opening was more active at the more rapid changes in W_L-W_A; there was a linear relationship between degree of the hydropassive stomatal opening and changing rate of W_L-W_A. Thus, the visible radiation containing PAR brought about the hydroactive stomatal movement mainly through physiological processes, whereas the infrared radiation caused the hydropassive stomatal movement through physical processes in response to the thermal effect.
九州大学の論文