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

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 (42)K, (36)Cl and (24)Na flux into the xylem. The transport of (42)K and (36)Cl 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 (42)K transport and caused a further inhibition of (42)K 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 (24)Na and (36)Cl in bean root tissue, but not that of (42)K.