The Regulation of Leaf Cell Expansion by Light and Ion Flux

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Leaf growth responses to light are important for a plant to maximize its photosynthetic capacity while conserving available nutrients and water. Leaf growth is stimulated photo- morphogenically by red and blue light acting by separate mechanisms, and is enhanced by photosynthesis occurring in the growing cells. The growth response to light is associated with proton efflux, and other ion fluxes across the plasma membrane. The objectives of this study are to ask: 1. How is the plasma membrane proton pump regulated by light in epidermal and mesophyll cells? 2. Are light-induced ion fluxes in leaf cells carried in part by ion channels, and if so, does light regulate channel activity? 3. Will mutants defective in growth responses to light exhibit altered electrical responses to light? These questions will be approached by electrophysiological (microelectrode and patch clamp) techniques taking advantage of mutants of Arabidopsis showing altered growth responses to light. %%% Leaf growth responses to light are important for a plant to maximize its ability to carry out photosynthesis while conserving available nutrients and water. Leaf growth is stimulated by red and blue light and is enhanced by photosynthesis occurring in the growing cells. The growth response to light is associated with ion fluxes across the cell membrane. This project will use electrical techniques to study the mechanisms by which ions move across the membranes of leaf cells in response to light. The results of this research will clarify the initial events occurring in light responses of growing leaf cells.