Evidence for a K(+)-stimulated Na (+) efflux at the plasmalemma of barley root cells.

The influence of K(+) on the Na(+) fluxes of barley root cells was investigated. A increased K(+) concentration (K(+) influx) results in a transient increase of the plasmalemma efflux of Na(+) followed by a decrease, and in a decrease of the cytoplasmic content and the tonoplast influx of Na(+). These results are consistent with a Na-K-pump at the plasmalemma.