Potassium Fluxes during Potassium Absorption by Intact Barley Plants of Increasing Potassium Content

The presence of previously absorbed K in plants caused a marked reduction in the short term influx of (86)Rb-labeled K into roots of barley seedlings. The influx values agreed with net K absorption rates into intact plants, thus suggesting that K efflux was negligible in comparison with influx.Earlier interpretations of a large K efflux component from excised roots approaching equilibrium K concentrations are considered to be due to an underestimation of net K absorption rates resulting from xylem exudation as the K status of the roots increased.