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Development and Growth Regulation

Similarity between Cytokinin and Blue Light Inhibition of Cucumber Hypocotyl Elongation ¹

Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel

The cytokinin benzyladenine inhibited endogenous hypocotyl elongation in intact etiolated seedlings of cucumber (Cucumis sativus L.). In hypocotyl segments, the inhibitory effect of benzyladenine on growth was clearly detectable in the presence of indoleacetic acid. Fusicoccin-induced elongation was unaffected by the presence of cytokinin. The effect of cytokinin on elongation of the segments was determined by measuring changes in fresh weight, a linear function of extension growth. The effect of benzyladenine on hypocotyl growth was at least as large in segments prepared from red-light-grown seedlings as in those from seedlings grown in total darkness. A comparison was made between the inhibitory effects of cytokinin and blue light. The use of the calcium chelator ethyleneglycol-bis(-aminoethyl ether)-N, N'-tetraacetic acid indicated that calcium ions are required for manifestation of benzyladenine-induced inhibition.

¹ L. C. was supported by a Lady Davis postdoctoral research fellowship at Technion. B. A. H. holds fellowships from the Allon Foundation and from the Bat-Sheva de Rothschild Fund for Science and Technology.