Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings VI. Promotive and inhibitory effects of kinetin

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The interaction of kinetin with IAA and GA_3 on the elongation of hypocotyl sections of Cucumis sativus L. cv. National Pickling was studied. Kinetin in the concentration range of 10^<-7> M to 10^<-4> M markedly inhibited IAA-induced elongation, while in a lower range from 10^<-10> M to 10^<-8> M, it synergistically enhanced IAA-induced elongation. Kinetin alone in this range had no effect. A 5- to 15-min pulse treatment seems enough to induce the maximum effect for both inhibition and promotion. Since the magnitude of the maximum inhibition depended on the concentration and not on the duration of treatment, the reaction in the cell caused by kinetin seemed to be completed within a short period. Washing of the sections with distilled water after kinetin treatment (30 min) did not significantly eliminate the kinetin effect. This probably indicates that the binding of kinetin molecules to a supposed acceptor is not reversible. Interaction of kinetin with GA_3 in their pretreatment effects on IAA-induced elongation shows that in the inhibitory concentration range, the kinetin effect was partly overcome by GA_3, and that in the promotive range, the magnitude of the enhancement was determined by kinetin regardless of the presence of GA_3. The effect of kinetin seems to dominate over that of GA_3, indicating that the modes of their pretreatment effects differ from one another.
日本植物生理学会の論文