This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (15) Citing Articles via Google Scholar Google Scholar Articles by Beyer, E. M. Search for Related Content PubMed PubMed Citation Articles by Beyer, E. M., Jr. Agricola Articles by Beyer, E. M.

Articles

[¹⁴C]Ethylene Metabolism during Leaf Abscission in Cotton ¹

^a Central Research and Development Department, Experimental Station, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19898

Changes in ¹⁴C₂H₄ metabolism in the abscission zone were monitored during cotton (cv. Deltapine 16) leaf abscission. Rates of ¹⁴C₂H₄ oxidation to ¹⁴CO₂ and tissue incorporation in abscission zone segments cut from the second true leaf of nonabscising leaves of intact plants were similar (about 200 disintegrations per minute per 0.1 gram dry weight per 5.5 hours) and relatively constant over a 5-day period. Deblading to induce abscission caused a dramatic rise in ¹⁴C₂H₄ oxidation, but tissue incorporation was not markedly affected. This rise occurred well before abscission, reaching a peak of 1,375 disintegrations per minute per 0.1 gram dry weight per 5.5 hours 2 days after deblading when abscission was 40%. The rate then gradually declined, but on day 5 when abscission reached completion, it was still nearly three times higher than in segments from nonabscising leaves. Application of 0.1 millimolar abscisic acid in lanolin to the debladed petiole ends increased the per cent abscission slightly and initially stimulated ¹⁴C₂H₄ oxidation. In contrast, naphthaleneacetic acid applied in a similar manner delayed and markedly inhibited both abscission and ¹⁴C₂H₄ oxidation.

Petiole segments cut 1 centimeter from the abscission zone of intact second true leaves also incorporated and oxidized ¹⁴C₂H₄ to ¹⁴CO₂ but at rates two and six times higher, respectively, than that of comparable adjacent abscission zone segments. However, in marked contrast to the abscission zone segments, no changes in oxidation were observed when the leaves were debladed to induce abscission.

These results demonstrate that: (a) prior to abscission, the ethylene oxidation, but not the tissue incorporation pathway, rapidly increases in the abscission zone; (b) this increase does not occur in adjacent petiole tissue; and (c) changes in the rate of oxidation and per cent abscission brought about by hormone treatments parallel one another. The possible significance of these changes in ethylene metabolism is discussed with respect to the hypothesis that ethylene action and metabolism are directly related.