Chemical structure and function of phototropism-regulating substances in plants

点击翻译按钮获取中文摘要

Phototropism is a typical example of an environmental response in plants. From many accumulated findings it is suggested that phototropism is caused by the unequal lateral distribution of light-induced growth inhibitor(s) in the illuminated and the shaded sides affecting the auxin activity at unchanged, even auxin level (Bruinsma-Hasegawa theory, 1990).In the present study, we investigated chemical structure and formation of phototropism-regulatming substances in plants. Blue light-induced growth inhibitors were isolated from light-grown maize coleoptiles, and identified as DIMBOA and MBOA from their ^1H NMR spectra. From chemical analyzes, it can be concluded that phototropic stimulation induces conversion of the inactive DIMBOA glucoside into the active DIMBOA, which plays the essential role in the phototropism of maize coleoptiles, and then metabolizes into MBOA, which has a lower activity.From light-grown Arabidopsis thaliana hypocotyls, indole-3-acetonitrile (IAN) was isolated and identified as a blue light-induced growth inhibitor. IAN increased in the wild type upon phototropic stimulation, whereas it showed no change in the mutant that shows no phototropic response. From these results it is suggested that IAN plays an important role in the phototropism of Arabidopsis hypocotyls.