Correlative Inhibition of Lateral Bud Growth in Pisum sativum L. and Phaseolus vulgaris L.: Studies of the Role of Abscisic Acid

The possibility has been investigated that abscisic acid (ABA) might act as a correlative inhibitor of lateral bud growth in Pisum sativum and Phaseolus vulgaris. Application of ABA in small quantities (2μg) to axillary buds on decapitated plants of P. sativum caused appreciable inhibition of their growth, and induced a compensatory growth of the bud on an adjacent node. Application of this same quantity of ABA to axillary buds on decapitated plants of Phaseolus vulgaris was without effect, but a high concentration in lanolin (1 mg g−1) did substantially reduce bud outgrowth. Endogenous ABA-like substances in Phaseolus vulgaris, detected by bioassay and electron capture g.l.c., were present in similar concentrations in shoot tips, lateral buds on intact plants and lateral buds on plants decapitated 24 h earlier. The effects of applied ABA suggested that it might be involved in the mechanism of correlative inhibition in Pisum sativum, but it was not possible to test this hypothesis by determining endogenous ABA levels in axillary buds because of their small size. The evidence presented here suggests that ABA is not a correlative inhibitor in Phaseolus vulgaris even though at high concentration it can inhibit the growth of axillary buds.