Distribution of Indoleacetic Acid Oxidase and Inhibitors in Light-Grown Cotton

Abstract

In vitro activity of IAA-oxidase increased in greenhouse-grown cotton (Gossypium hirsutum) leaves and stems from apex to base of the plants in several stages of development. Inversely, inhibitor activity was highest in the apex and declined basipetally. The activity patterns of both substances were also demonstrated with respect to age in fruiting forms and in leaves of plants grown in the field. The findings are compatible with a hypothesis that IAA-oxidase functions in vivo in cotton to help regulate auxin levels and that the activity of the enzyme is controlled by an inhibitor system.