Associate Professor University of California, Davis, California, United States
Abstract: Leaf stomata are responsible for allowing gas-exchange and thereby photosynthesis in land plants. Stomatal opening and closure are affected by a number of environmental and biochemical factors. One environmental factor that has received little attention is the direct effect of temperature on stomata. Although many previous studies have increased temperature, few have focused on the effects of temperature while controlling for other environmental factors known to affect stomata, especially the vapor pressure difference between the leaf and air (VPD). The need to control for VPD while changing temperatures makes this experiment very difficult to accomplish. A positive response to temperature has been predicted due to the decrease in water viscosity as temperature rises, allowing for easier rehydration. What data exists regarding direct temperature response is consistent with a positive response. This data comes a limited number of species, however, with varying responses. The goal of this ongoing study is to determine the direct response of stomata to temperature across a wide variety of species from diverse lineages. Initial experiments involved placing leaves inside a gas exchange chamber (LI-6800) and varying temperature between 15 and 35oC while holding VPD constant. To prevent condensation in the gas analysis system, the plant and LI-6800 were placed inside of a temperature-controlled tent. Initial results show a positive response of stomatal conductance to temperature. Several hypotheses exist as to why this response occurs, including biochemical and physical processes. Future experiments will examine more taxa, test the effects of ABA concentration and sensitivity, and the effects of growing conditions to help determine what factors cause this response. This data will then be used to update mechanistic models of plant gas-exchange and water use accordingly.
