Postpollination Phenomena in Orchid Flowers. IX. Induction and Inhibition of Ethylene Evolution, Anthocyanin Synthesis, and Perianth Senescence

Abstract

Auxin (naphthaleneacetic acid [NAA]) application to Cymbidium stigmas (25 .mu.g/flower) induced high rates of ethylene evolution by the flowers within 18 h of the treatment. Actinomycin D reduced the rate of ethylene evolution if applied with the auxin or 2 h after it. Cycloheximide reduced ethylene production regardless of time of application. Puromycin had an inhibitory effect if applied 1 or 2 h after the auxin. Ethionine if applied with the auxin or 1 or 3 h after it, induced more rapid ethylene production and higher evolution rates than NAA alone. Applications of ethionine 2 h after the auxin reduced the levels of ethylene evolution but not the rates or induction time. Anthocyanin levels decreased when each inhibitor was applied together with the auxin. Actinomycin D, cycloheximide, or puromycin, given 1 h after auxin application, did not reduce anthocyanin levels while ethionine did. Initial synthesis of anthocyanins may depend primarily on preexisting RNA and proteins; subsequent production requires de novo RNA and protein synthesis. Ethionine may be a specific inhibitor of anthocyanin production. Of the additional postpollination phenomena exhibited by Cymbidium flowers, some are sensitive to RNA and protein synthesis inhibitors and others are not.