The energetics of Cl− active transport inChara

Abstract

The rate of Cl− influx in intactChara was inhibited whenever the ATP concentration was reduced by application of metabolic inhibitors. In perfused cells, however, a net influx of Cl− against its electrochemical gradient could be observed in the absence of ATP. Addition of ATP to the perfusion medium slightly stimulated Cl− influx in one experiment but had no effect in another. Addition of ADP, NADH or metabolic inhibitors did not alter the influx rate. Consideration of the potential energy gradients across theChara plasmalemma in the perfused state leads to the conclusion that Cl− influx occurs by cotransport with H+ or OH−.