Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 2/27/2003
Publication Date: 12/1/2003
Citation: SUTTLE, J.C. ROLE OF ETHYLENE IN NAPHTHALENE-MEDIATED SPROUT GROWTH INHIBITION IN POTATO. ACTA HORTICULTURAE, Proceeding of International Horticultural Congress. 2003. v. 619. P. 383-388. Interpretive Summary: For an indeterminate period of time following harvest, potatoes will not sprout and are physiologically dormant. Dormancy is gradually lost during postharvest storage and the resultant sprouting is detrimental to the nutritional and processing qualities of potatoes. Because of this, sprouting results in severe financial loss to producers. Currently sprouting is controlled through the use of synthetic sprout inhibitors. The research being conducted in this lab is directed towards 1) identifying key physiological processes that naturally regulate tuber dormancy and ultimately, 2) modifying these processes genetically thereby eliminating the need for artificial sprout suppression. Much of our current research concerns the roles of plant hormones in the regulation of tuber dormancy. Various naphthalene derivatives have been shown to inhibit sprout growth in stored potatoes and, therefore, have potential utility as commercial sprout suppressants. In this paper, the mechanism of action of certain sprout-inhibiting naphthalene derivatives was examined. Specifically, the role of the plant hormone ethylene (itself, a powerful sprout inhibitor) in naphthalene-induced sprout inhibition was determined. The results show, that although ethylene production was stimulated by certain naphthalenes, it played no role in the observed sprout inhibition. It was concluded that naphthalenes directly affect sprout growth by interfering with the processes of cell division and elongation.
Technical Abstract: A number of substituted naphthalenes reversibly inhibit potato (Solanum tuberosum L.) sprout growth and may have potential as commercial sprout inhibitors. Sprout growth is also reversibly inhibited by ethylene treatment and ethylene production is often stimulated by xenobiotics. The role of endogenous ethylene in naphthalene-mediated sprout growth inhibition was examined using a variety of ethylene biosynthesis and action inhibitors. Ethylene evolution from intact potato tubers was significantly stimulated following treatment with alpha-naphthalene acetic acid (NAA) but not by 1,4- or 1,6- dimethylnaphthalene treatment. An increase in ethylene production was observed 24 h after NAA treatment, reached a maximum 48-72 h post-treatment and declined gradually thereafter. In addition to NAA, a variety of structurally unrelated auxins also stimulated ethylene production and inhibited sprout growth. Neither the non-competitive (Ag thiosulfate) nor the competitive (2,5-norbornadiene) ethylene antagonist affected NAA-induced growth inhibition. Simultaneous treatment with the ethylene biosynthesis inhibitor AVG blocked NAA-induced ethylene production but did not affect subsequent sprout growth inhibition. These results suggest that the sprout inhibiting effects of NAA, but not those of 1,4 or 1,6-dimethyl-naphthalene, are related to intrinsic auxin-like bioactivity and are not dependent on endogenous ethylene synthesis or action.