Abstract: The plasmalemma-bond redox system localized within the plasmalemma of unicellular green alga Dunaliella salina was studied. This system oxidized exogenous NADH, increased O2 consumption to 165 % and increased the pH of the external medium, while K+ influx was inhibited. With no NADH added, ferricyanide stimulated K+ uptake about 3 folds. In the presence of exogenous NADH, ferricyanide was rapidly reduced and the external medium was acidified, generating a greater electrochemical proton gradient across the plasmalemma, thus resulting an 6-fold increase of K+ influx. Typical inhibitors of plasmalemma H+-ATPase and redox system inhibited K+ uptake to different extent. That the inhibition of K+ uptake by vanadate could be resumed partly by addition of NADH and ferricyanide indicated that plasmalemma redox system operated in association with the H+-ATPase to exert an influence on K+ transportation. A model was presented in which the implication of two possible redox chains and H+-ATPase in generating an electrochemical potential gradient for protons (△uH+) was discussed.

Key words: Redox system, K + uptake, O2 consumption, H+ extrusion: Inhibitors