Specific interactions in the physiology of flowering and gibbosity of Lemna gibba G3

Abstract

Fronds of Lemna gibba G3 became conspicuously gibbous when ethrel, an ethylenereleasing compound, was added to the nutrient medium. Maximal gibbosity was obtained at ethrel concentrations of 1 μg/ml and higher. Unlike the chelating agent, EDDHA, which causes profuse flowering and markedly gibbous fronds under long-day conditions, ethrel did not affect flowering. In the presence of an optimal concentration of EDDHA (10 μ/ml), ethrel even significantly inhibited flowering and caused development of excessively gibbous fronds. Autoclaved gibberellic acid specifically negated the ethrel effect as it does that of EDDHA. Three decomposition products of GA₃, allogibberic acid, epiallogibberic acid and gibberic acid, also nullified flowering and gibbosity in the presence of EDDHA. A fourth decomposition product of GA₃, epigibberic acid, inhibited gibbosity but hardly affected flowering. Salicylic acid was confirmed to affect flowering and gibbosity in L. gibba G3. However, contrary to an earlier report, it did not induce flowering under short-day conditions.