EFFECTS OF BLUE-LIGHT ON ELECTRICAL POTENTIAL AND TURGOR IN PULVINAR MOTOR CELLS OF PHASEOLUS

Pulvinar motor cells of Phaseolus vulgaris L. display transient depola rization of the membrane potential and a turgor pressure decrease when exposed to a pulse of blue light. To analyze the mechanism of the tra nsient depolarization, the effects of some factors such as anoxia, met abolic inhibitors and specific inhibitors of H+-ATPase have been exami ned. The findings have led to the conclusion that blue light inactivat es the electrogenic H+-pumping ATPase in the plasma membrane of the mo tor cells. This inactivation seems to suppress ion uptake and decrease the turgor pressure of the motor cells.