Light-Triggered Changes of Membrane Potential in Cells of Anthoceros punctatus and their Relation to Activation of Chloroplast ATPase

Post-illumination transients of the membrane potential were revealed in cells of Anthoceros punctatus upon short ( 1-2 s) irradiation with photosynthetically active light. An initial fast depolarization of the cell by 20-30 mV after a lag period of 2 s and a subsequent slow repolarization were recorded with micro-electrodes positioned both in the chloroplast and in transparent parts of the cell. The potential changes of similar kinetics were also observed upon continuous illumination. Post-illumination potential changes were abolished by 3-(3,4-dichlorophenyl)-l,l-dimethylurea and dicyclohexylcarbodiimide and were stimulated by the addition of NH4C1. It is assumed that the light-triggered potential change across the plasmalemma of A. punctatus are determined by the light activation of chloroplast ATPase. This assumption is further supported by observations of post-illumination transient increase of the chlorophyll fluorescence in preparations of A. punctatus.