Studies of Effects of Light on Growth Pattern and of Gibberellin Sensitivity in Relation to Age, Growth Rate, and Illumination in Intact Wheat Coleoptiles

Abstract

Although there have been many studies on effects of light on over-all elongation of various plant organs, relatively little is known concerning effects of light on the pattern of elongation within a given organ, i.e., the relative contributions of various portions of the organ to the total elongation. In this study, intact wheat coleoptiles were marked with India ink to permit an investigation of effects of various light treatments on the pattern, as well as the total extent, of elongation. These intact coleoptiles are also used to test the suggestion that actions of photomorphogenic radiation on elongation are closely related to gibberellin effects (4, 17, 25, 27, 30), and the generalization that gibberellin is more effective on young, rapidly growing tissues than on older, more slowly growing tissues (4, 12, 13, 22, 23, 27,33).