Abscisic acid (ABA) as a naturally occurring growth inhibitor was discovered through independent investigations of different physiological phenomena in two different laboratories. F.T. Addicott and collaborators (University of, California) had been investigating natural substances which accelerate leaf abscission, whereas P.F. Wareing et al (University College of Wales at Aberystwyth) had been investigating natural inhibitors which appeared to be related to bud dormancy in woody plants.
Figure: Structure of Abscisic Acid
By 1965, these two paths of research converged upon the discovery that a single hormone was involved in both. The term Abscisic acid (ABA), was later proposed to denote this compound, which is a sesquiterpenoid (15-C) compound.