Abscisic acid promotes the formation of adventitious roots in cuttings of Phaseolus coccineus L. The optimum concentration is 10-5 M. ABA antagonises the GA, induced inhibition of rooting. The ABA effect is accompanied by a stimulation of the growth of the 2nd internode. No ABA action is observed on cuttings kept continuously in the dark or on defoliated cuttings. Treatment of cuttings with ABA causes an accumulation of assimilates, especially sucrose, which are basipetally transported from the primary leaves to the basal parts of the cuttings.