Transplasma-membrane ferricyanide reduction in sycamore cell. Characterization of the system and inhibition by phenyl biscarbamates

Evidence is presented for the presence of a transplasma-membrane redox system in sycamore cells, which were found able to reduce external ferricyanide. Ferricyanide reduction was accompanied by a slight reduction of potassium uptake. The transmembrane electron transport was inhibited by a slight reduction of potassium uptake. The transmembrane electron transport was inhibited by oligomycin and quinacrine; the effect of the latter inhibitor was oly temporary, owing to its progressive absorption by the cells. Several derivatives of the herbicide phenmedipham were able to inhibit the growth of sycamore cells. But had no effect on the phosphohydrolase activity of a microsomal fraction enriched in plasmalemma ATPase. They were not uncouplers of oxidative phosphorylation, and appeared as poor inhibitors of mitochondrial electron transfer.