Abscisic acid, plant-growth hormone inhibitor

Abiotic elicitors, examples, 48 Abscisic acid, plant-growth hormone inhibitor, I6f Active defense, definition, 37 Alfalfa, phytoalexins, 56 Allelochemicals... 

Among the plant hormones discussed In this Symposium, the growth Inhibitor abscisic acid Is the most recently discovered one. Work In the 1950s and early 1960s by three groups, working on apparently unrelated problems, ultimately resulted In the Isolation and Identification of abscisic acid in each case (see reviews 1, 2, 3, 4) (a) The search for an abscission-... 

Abscisic acid (44) is involved in a number of hormonal roles in plants (Fig. 26.16) (Milborrow, 1983). This plant growth-regulating compound, probably found in all higher plants, acts as a growth inhibitor and is involved in bud and seed dormancy. (+ )-(5)-Abscisic acid is a potent effector of stomatal closure. Abscisic acid also is linked to water stress resistance in plants. To date, the presence of abscisic acid has not been confirmed in bryophytes (Milborrow and Netting, 1991). 

In an indirect manner, the lipoxygenase reaction in higher plants appears to be implicated in the biosynthesis of abscisic acid, a further senescence hormone [23-25], Abscisic acid is formed from the carotenoid violaxanthin that is converted into xanthoxin, which is a plant growth inhibitor and at the same time a precursor of abscisic acid. The formation of xanthoxin requires the co-oxidative activity of a lipoxygenase-linoleic (or a-linolenic) acid system. 

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