Plasmalemma redox activity and H super(+) extrusion: 1. Activation of the H super(+) -pump by ferricyanide-induced potential depolarization and cytoplasm acidification

Ferricyanide reduction by Elodea densa leaves, in the dark, is associated with: acidification of the medium; decrease of intracellular pH (measured in cell sap, cytoplasm, and vacuole); depolarization of the transmembrane potential; net efflux of K super(+) to the medium. The results indicate that ferricyanide reduction depends on a plasmalemma system transporting only electrons to the extracellular acceptor, with consequent potential depolarization and cytoplasm acidification.