EFFLUX OF POTASSIUM FROM WHEAT ROOTS INDUCED BY CHANGES IN THE WATER POTENTIAL OF THE ROOT MEDIUM

Effects of rapid or stepwise decrease of the water potential by polyethylene glycol in the root medium on the efflux and uptake of 86Rb‐potassium, and the effect of abscisic acid on the efflux of 86Rb‐potassium were investigated in roots of intact wheat plants (Triticum aestivum L. cv. Weibulls Original Starke II). The efflux of ions increased at both a rapid and a stepwise reduction in water potential, but the effect was less at a stepwise reduction in water potential. Active uptake of ions decreased as much at a stepwise as at a rapid reduction in water potential. Addition of 4 × 10–5 M abscisic acid to the root medium did not affect the efflux of ions. It is suggested that low water potentials affect both membrane permeability and active uptake of ions. The increase of efflux is not induced by increase of ABA only. Copyright © 1979, Wiley Blackwell. All rights reserved