Studies on the Mechanism of Stem Growth Inhibition by Visible Radiation.

Abstract

Applied gibberellic acid specifically reverses the light inhibition of etiolated stem growth in certain species (4, 5). It therefore appears reasonable to suggest that light regulates stem elongation in these plants through some effect (or effects) on the gibberellin metabolism of the plant. Results presented in the present paper provide further support for this hypothesis. The effect of light on the gibberellin metabolism might be mediated through 1 of 3 general mechanisms. First, light may decrease the synthesis of endogenous gibberellin; or, second, it may cause the destruction (or diversion) of the natural gibberellin. Finally, light might make the tissue less responsive to a given amount of gibberellin. The results presented in the present paper make possible a partial resolution of these alternatives.