Interaction of gibberellic acid, abscisic acid, and phenolic compounds in the control of hypocotyl growth of <i>Amaranthus caudatus</i> seedlings

Abstract

Abscisic acid, a potent growth inhibitor, inhibits hypocotyl growth of Amaranthus caudatus (L.) seedlings. Phenolic compounds when applied with ABA (abscisic acid), antagonize ABA action and restore normal seeding growth. GA (gibberellic acid) promotes hypocotyl growth and on combined application with ABA, the ratio of their concentrations determines the course of the resultant growth. This interaction can be modulated by phenolic compounds. Phenolic compounds in low concentrations when present together with GA and ABA favour GA-induced growth by antagonizing the inhibitory effect of ABA. Inhibitory action of abscisic acid on growth is so far known to be counteracted only by growth-promoting hormones. Antagonistic action of phenolic compounds imparts a dual role to this class of compounds, balancing the effect of growth-promoting and growth-inhibiting hormones.