Abscissic acid: Chemical nature, Biosynthesis, Bioassay, Physiological effects and Mode of action
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Abscisic Acid (ABA):- > It is found in older leaves, apical buds and seeds. > Both GA and ABA hormones work opposite to each other. > ABA inhibits the biosynthesis of the hormone GA. 1. Discovery of Abscisic Acid:- - Torsten Hemberg (1940) reported that dormant potato tubers and buds of ash (Fraxinus excelsior) contained inhibitor (rather than stimulators) that blocked the effects of IAA. When the buds germinated, the amount of these inhibitors decreased. - Eagles and Wareing (1963) isolated an inhibitor from the birch (Betula pubescens) leaves held under short day conditions. When this substance was reapplied to the leaves of birch seedlings, apical growth was completely arrested. As this substance induced dormancy, they named it as ‘dormin’. - Cornus and Addicot (1963) isolated this compound from the shedding bolls of cotton plant. - Ohkum (1965) isolated an inhibitor from cotton fruits and named it ‘abscisin II’. - Cornforth (1965) demonstrated that both Do...