Levels of IAA, Cytokinins, ABA and Ethylene in Rice Plants as Affected by a Gibberellin Biosynthesis Inhibitor, Uniconazole-P.

Abstract

Effects of uniconazole-P, a triazole-type growth retardant, on endogenous levels of IAA, cytokinins, ABA and ethylene in rice seedlings were investigated. Endogenous levels of IAA and ABA were similar between control and uniconazole-P-treated rice shoots. Evolution of ethylene was promoted slightly, being 1.8 times greater under 0.3 ppm uniconazole-P treatment than that of control. The most obvious effect was the increase of trans-Z and trans-RZ in shoots. Shoots treated with uniconazole-P (10 mg/m2 nursery box) contained 3.4 times and 3 times more trans-Z and trans-RZ than control, respectively. No significant differences of cytokinin levels were recognized in roots except for cis-RZ. The increase of ethylene and active forms of cytokinins, and the decrease of gibberellin in the shoots may be the basis for physiological phenomena caused by uniconazole-P, namely the promotion of flowering in woody plants and the enhancement of femaleness in cucumber.