The action of abscisic acid on ion uptake and water flow in plant roots

Abstract

Abscisic acid was shown to inhibit transport of potassium and chloride from the cut ends of excised barley and maize roots. Transport to the shoot of intact barley seedlings was also inhibited. Total uptake into the excised root of barley did not appear to be affected by abscisic acid. There was an increase in tracer accumulated in the root accompanying the reduction in transport from the cut end. Concentrations of abscisic acid above 10−6M produced the maximum effect. Measurements of exudation from excised maize roots showed that abscisic acid inhibited both water flow and net potassium transport into the exudate. The reduction in water flow was completely accounted for as an osmotic consequence of inhibition of potassium secretion, so that there was no evidence for an effeot of absoisio acid on the permeability of the root to water. The results are disoussed in relation to the regulation of ion and water distribution within the whole plant. © 1972 CSIRO.