Abscisic Acid (AbA) - Plant Growth Substances
In 1961 Lice and Cams isolated a substance in crystalline form from mature cotton fruit. This substance stimulated the abscission of debladed cotton petioles. It also promotes flowering in some short day plants. The dormancy response may be through an effect of RNA and protein synthesis. Some effects of Abscisic Acid seem to be reversed by gibberellins (seed dormancy) or by cytokinins (stomatal closure).