Role of IAA-Oxidase in Abscission Control in Cotton

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Abstract
Monophenols, which are cofactors of cotton IAA-oxidase in vitro, accelerated abscission of cotyledonary explants. Orthodihydroxyphenols, which inhibit cotton IAA-oxidase in vitro, inhibited abscission. Inhibition or stimulation of abscission was accomplished by phenols both with and without IAA. Results were similar when treatments were applied as lanolin pastes to the cut petiole ends or as solutions in which explants were submerged. An abscission-accelerating phenol stimulated while an abscission-inhibiting phenol inhibited IAA-1-C14 decarboxylation in explants. The mechanism of abscission regulation by the phenolic compounds may involve auxin destruction via IAA-oxidase. IAA-oxidase may act in vivo to regulate auxin levels. Other physiological functions of peroxidase and phenols or the activity of other enzymes in abscission are not excluded.