Аннотация:Effects of plasma membrane action potential (AP) on external pH and chlorophyll (Chl) fluorescence in Chara corallina cells were examined in the absence and presence of an electron transport inhibitor and electron acceptors. In intact cells, energy-dependent quenching qE developed at high photon flux densities (PFD) and appeared transiently after electrically stimu-lated AP at moderate PFD. Diuron (DCMU) fully inhibited qE established by light and AP. The artificial cyclic electron flow restored qE imposed by light but not the electrically induced qE. Methyl viologen (MV) at concentrations 0.1–0.83 mM had no effect on fluorescence and quantum efficiency of photosystem II (PSII) until the first excitatory stimulus was applied. However, triggering AP in the presence of MV induced rapid qE formation at low PFD indicat-ing that a divalent cation MV became instantly accessible to thylakoids and partially diverted electron flow from PSI to MV reduction.