Stimulation of volume flow and ion flux by abscisic acid in excised root systems of Phaseolus vulgaris L. cv. Redland Pioneer

Abstract

Abscisic acid (ABA) caused a 7–8-fold increase in volume flow in excised bean root systems and this was coupled with an increase in ⁴²K, ³⁶Cl and ²⁴Na flux into the xylem. The transport of ⁴²K and ³⁶Cl increased by a factor larger than the stimulation of volume flow, resulting in an increase in the concentration of those ions in the xylem exudate. Carbonyclcyanide-m-chlorophenyl hydrazone, on the other hand, eliminated ABA-stimulated ⁴²K transport and caused a further inhibition of ⁴²K flux, thus providing additional support for the proposition that ABA stimulation may involve an energised process of ion transport. ABA also increased the accumulation of ²⁴Na and ³⁶Cl in bean root tissue, but not that of ⁴²K.