Ion transport and leaflet movement will be studied with: 1) Single and double barrel ion-sensitive microelectrodes to measure the dynamic relationship of H+, K+, Cl- and Ca++ fluxes in the pulvinar apoplast, in response to light, channel blockers, and pump inhibitors; and 2) Patch clamp methods to probe for changes in the electrical behavior of ion pumps and channels in Samanea protoplast membranes in response to light, channel blockers, and a variety of ionic conditions: To further probe the mechanism of light signal transduction, standard biochemical methods will be used to elucidate the diacylglyerol portion of the PI pathway. The effects of PI cycle intermediates on ion transport will also be investigated.%%% Samanea saman is a nyctinastic legume with paired leaflets that usually separate from each other (open) in the light and fold together (close) in the dark. These leaf movements are also under circadian control and furnish a convenient model system for studying biological time measurements in plants. They are turgor regulated and driven by movements of ions through membranes of the cells in the motor organ (pulvinus). The ion movements result from rhythmic and light-regulated changes in pumps and channels in the membranes. The light signals require amplification and the plant uses the phosphatidylinositol (PI) pathway. This pathway is well studied in animals but unexplored in plants. This project will study the tranduction mechanism using a variety of techniques.***//