During mid-1960s, three independent researches reported the purification and chemical characterisation of three different kinds of inhibitors: inhibitor-B, abscission II and dormin. Later all the three were proved to be chemically identical. It was named abscisic acid (ABA).
Abscisic acid (ABA) was discovered for its role in regulating abscission and dormancy. an inhibitor of plant metabolism. ABA inhibits seed germination. antagonist to GAs.
ABA stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone.ABA plays an important role in seed development, maturation and dormancy.
ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps seeds to withstand desiccation and other factors unfavourable for growth.
Roles of PGR could be complimentary or antagonistic. These could be individualistic or synergistic.