K(+)-dependent net Na(+) efflux in roots of barley plants.

The influence of K(+) ions on the net Na(+) fluxes in cells of excised barley roots (Hordeum distichon L.) and roots of whole barley plants was investigated. The fluxes were determined by flame photometry in the external solution. In both cases a transient net Na(+) efflux against the external Na(+) concentration was observed upon addition of K(+). The results stress the effectiveness of the K(+)-dependent Na(+) efflux mechanism residing at the plasmalemma, and its involvement in K-Na-selectivity in whole barley plants.