Regulation or gibberellin biosynthesis by light

Phytochromes regulate transcript levels of gibberellin biosynthesis enzymes , GA 20-oxidases and/or GA 3 beta-hydroxylases, in germinating lettuce and Arabidopsis seeds and in de-etiolating pea seedlings. Feedback regulation o f Ga biosynthesis by active GA is well established but other mechanisms for regulation of these biosynthetic genes also exist, as this feedback does n ot operate on a GA 3 beta-hydroxylase gene of Arabidopsis during seed germi nation.