Seasonal Changes in Citrus Auxin and 2 Auxin Antagonists as Related to Fruit Development

Abstract

Quantitative changes in Citrus auxin and 2 auxin antagonists were correlated with the growth and development of the parthenocarpic Navel orange, Citrus sinensis, to estimate the importance of these compounds to the source fruit. Fruit set in the parthenocarpic orange was correlated with a high level of Citrus auxin typical of the pattern shown for grapes and suggested for Citrus. The period of maximum fruit drop seemed to coincide with the change from cell division to cell enlargement, a change in the pattern of auxin accumulation, and the initial detection of an auxin antagonist, Inhibitor I. The highest concentration of Inhibitor I was associated with a change in the growth rate of the fruit and a decrease in auxin level.