2,4‐D‐Induced Changes in the K + Uptake of Wheat Roots at Different pH Values

The effects of an auxin herbicide, 2,4‐D, at a concentration of 0.01 m M , on the K + uptake and efflux of excised roots of wheat ( Triticum aestivum L. cv. Rannaya) were investigated at different pH values. The K + movement was monitored with a K + ( 86 Rb) tracer. In parallel experiments the ATPase activities of microsomal fractions were determined by the inorganic phosphate liberation method. 2,4‐D inhibited the K + uptake especially at low pH, irrespective of whether Ca 2+ was present or not. No marked changes were observed in the K + efflux properties at pH values above 4. The inhibitory effect on K + uptake exhibited a correlation with the hydrocarbon solubility of the herbicide, but not with the 2,4‐D‐induced decrease of the ATPase activity. It is suggested that 2,4‐D exerts a non‐specific effect on the lipid‐protein interactions, giving rise to a generalized alteration of the transport barrier properties of the plasma membrane even at as low a concentration as 0.01 m M .