ABA is well known for its role in the induction and maintenance of seed dormancy. Highest endogenous level of
ABA has been recorded during seed maturation and at the onset of dormancy [17]. The biological activity of
ABA is controlled either by conjugation with glucose to form ABA glucosyl ester (ABA-GE), or through oxidation
to phaseic acid (PA), dihydrophaseic acid (DPA), DPA-glucosides (DPA-GS) [22]. These oxidized forms
render ABA inactive and regulate the endogenous concentration of ABA [12]. ABA level decreased upon release
of seed dormancy during seed imbibition leading to germination, as found in several plant species [23],
[24]. Kushiro and co-workers [13] found that ABA catabolism was active during imbibition period in Arabidposis
and the level of catabolites, viz. PA and DPA, was increased. Hence, the free active form of ABA decreased
and bound form increased in the imbibed seeds.