The influence of potassium content on the kinetics of potassium influx into excised ryegrass and barley roots.

The influx of K(+) into excised roots of barley (Hordeum vulgare L.) and ryegrass (Lolium multiflorum L.) previously grown with or without K(+) was measured in K(+) solutions ranging in concentration from 0.01 to 50 mM. In both species the K(+) influx was lower in the roots with high K(+) content. The extent of reduction by high internal [K(+)] decreased with external concentration above 1 mM. These results support the contention that at high external concentrations passive diffusion makes significant contributions to observed fluxes.