Absorption, Translocation, and Metabolism of Et-IAA in Relation to Fruit Set and Growth of Day-neutral Strawberry

in Journal of the American Society for Horticultural Science
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  • 1 Department of Pomology, University of California, Davis, CA 95616


Single applications of auxins that normally induce parthenocarpic fruit set in June-bearing and everbearing strawberries (Fragaria × ananassa Duch) (e.g., NAA, 2-NOA, and IAA) do not induce set in the day-neutral cultivar Fern. The only auxin found to date that induces set in day-neutrals with a single application is Et-IAA. The translocation and metabolism of [14C]Et-IAA applied to receptacles was followed in order to gain insight into mechanisms involved in set. Ninety to ninety five percent of the recovered 14C activity remained in the receptacles throughout set and initial development (0 to 6 days) after Et-IAA application. Growth of treated receptacles followed the rapid metabolism of [14C]Et-IAA. Twelve hours after application, 16% of the radioactivity remained in the Et-IAA fraction. This level decreased to <5% by 144 hr after application. The majority of the radioactivity (55–60%) was contained in highly polar compounds. Little activity was recovered in the free IAA fraction. Chemical names used: 1-naphthaleneacetic acid (NAA); 2-naphthoxyacetic acid (2-NOA); 1H-indole-3-acetic acid (IAA); IAA ethyl ester (Et-IAA).

Contributor Notes

Present address: Fruit Crops Dept., Univ. of Florida, Gainesville, FL 32611.

Received for publication 3 Nov. 1986. We gratefully acknowledge Royce Bringhurst for his generous gift of plant material. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.