Mott 9420862 Experiments will be conducted to determine the relationships between the functioning of a single stoma and the responses of stomatal conductance in an intact leaf. Recent studies provide evidence that stomata in a leaf interact in complex and unexpected ways such that changes in whole leaf stomatal conductance may not reflect proportional changes for all stomata. Two levels of stomatal interactions will be investigated. First, interactions that could lead to synchronized behavior of all stomata within an areole (the smallest area of the leaf surrounded by veins) will be investigated. Several studies have shown that such behavior is relatively common (e.g., patchy stomatal closure), and Dr. Mott has proposed a hydraulic mechanism by which the movements of stomata within an areole could be synchronized. This hypothesis will be tested using epi-illumination microscopy to observe movements of individual stomata in a intact leaf. One or more stoma will be induced to open or close by altering its light environment using small glass fibers. The response of that stoma and the responses of neighboring stomata will be recorded using video digitizing equipment. The effect of changes in transpiration for one part of a leaf on stomatal conductance of other parts of the leaf will be determined using gas-exchange techniques. Changes in transpiration induced by changes in humidity, carbon dioxide, and light will be used to evalluate the role of hydraulically-based mechanisms in producing the conductance responses observed in preliminary experiments. Fluorescence imaging will be used to quantify the spatial distribution of stomatal conductance over the leaf surface. Finally, cellular automaton modeling will be used to simulate interactions among stomata and among areoles and scale from single stoma dynamics to spatial and temporal variations in whole leaf conductance. Because the model is computationally demanding, modeling work will be conduct ed at an NSF Supercomputer Center. Results from the experiments described above will be used to structure the model, and model predictions will be compared to experimental results to test proposed mechanisms.
