Responses of the First Internodes of Hong Mang Mai Wheat to Ethylene, Gibberellins and Potassium

Abstract

Seedlings of Hong Mang Mai wheat (Triticum aestivum L.) emerge from much deeper in the soil than do other cultivars by elongating their first internode. We examined the roles of ethylene, gibberellins (GA) and potassium in the elongation of the first internode in wheat cultivars. Although ethylene stimulated the elongation of the first internode of Hong Mang Mai in the dark, the ethylene evolution and the expression level of ethylene-receptor-like gene of this cultivar were not greater than those of other cultivars. In Hong Mang Mai, gibberellin A₃ (GA₃) substantially stimulated the elongation of the first internode in the dark. Maximum elongation of the first internode was obtained by GA₃ at the concentrations of 2.89 × 10^-6 to 2.89 × l0^-7 M. This cultivar responded markedly to gibberellins A₁ and A₃ by elongating the first internode in the dark. A mixture of gibberellins A₄ and A₇ (GA₄₊₇) was not effective in inducing the elongation. Haruhikari, a cultivar having no GA -insensitive-reducing-height (Rht) genes, substantially responded to GA₃, but other cultivars did not. The differences in the sensitivity to GA could account, at least in part, for the varietal differences in the elongation of the first internode in wheat. Takune-komugi, a cultivar whose first internode elongates in response to ethylene, did not respond to GA₃. Thus, there are different mechanisms for the GA- and ethylene-stimulated elongation of the first internode in wheat. Also, it was suggested that potassium uptake from the soil might function together with endogenous GA in inducing the elongation of the first internode in Hong Mang Mai wheat.