Ethylene Production and Endogenous Gibberellin Content in Chrysanthemum Plants as Affected by Uniconazole, Brushing and Aminoethoxyvinylglycine Treatments

Abstract

Chrysanthemum (Dendranthema grandiflora (Ramat.) Kitam.) plants, sprayed with a 25 ppm uniconazole one month after planting, evolved ethylene immediately and attained the highest yield on the third day. Plants that were brushed (mechanical stress, MS) for 30 days produced more ethylene on the third day than did uniconazole-sprayed plants and maintained their high production. Plants treated with aminoethoxyvinylglycine (AVG) yielded the lowest levels of ethylene and displayed no peak. Application of AVG to uniconazole-sprayed or brushed plants decreased ethylene evolution. Gibberellic acid (GA)-like substances in the control plants separated into 4 bands on silica gel TLC plates; authentic GA₁ GA₃, and GA₇ were detected at the same Rf in the control plants. GA₁- and GA₃-like substance contents decreased markedly in plants sprayed with uniconazole or brushed. The application of AVG alone did not affect GA- like substance content, nor did it enhance GA activities in uniconazole-sprayed plants. Thus, growth of chrysanthemum plants is controlled not only by GA activities but also by ethylene.