Role of IAA-Oxidase in Abscission Control in Cotton

The potential role of indoleactic acid (IAA)-oxidase as an in vivo abscission regulating system in the cotton (Gossypium hirsutum L.) cotyledonary explant was investigated. Phenols (usually monophenols), which are cofactors of cotton IAA-oxidase in vitro, accelerated abscission. Phenols (usually 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 the decarboxylation of IAA-1-¹⁴C by explants and an abscission inhibiting phenol inhibited the decarboxylation of IAA-1-¹⁴C.