Effects of Kinetin, IAA, and Gibberellin on Ethylene Production, and Their Interactions in Growth of Seedlings

Abstract

A bstract. Kinetin in concentrations of 10-e to 10-4 M, stimuated ethylene production in 3 and 4-day old etiolated seedlings of Alaska pea (Pisucm sativum L. var. Ala-ka). Seedlings of other species responded similarly. The response to kinetin depended on the age of the seedlings.Kinetin alone did not influence ethylene production in 6-day old stem sections, but it greatly increased the enhancing effect of IAA.Gibberellic acid had no effect on ethylene production by pea seedlings during the first 6 days of growth. Ethylene and gibberellic acid are antagonistic in their effects on growth of the seedlings; ethylene interfered severely with the action of gibberellic acid but did not completely suppress it.The inhibitors cycloheximide, cupferron, and N-ethylmaleimid?, caused considerable inhibition of kinetin-induced ethylene production but were much less effective in the endogenous ethylene-forming system. Materials and MethodsPlant Materials. Alaska pea seeds (Pisunm sativum L. var. Alaska) were soaked in a beaker in the dark, in running tap water bubbled with air. The soaking was carried out for 48 hr at 250, a treatment which was found to produce uniform, disease-free seedlings. Thev were then planted on wet "Kimpack" (an absorbent of one-eighth inch thick packing paper) and grown at 25°and about 95 % relative humidity. The seedlings were grown in darkness up to 6 days with occazional dim "safe green" light. Seedlings were transferred to 50 ml flasks in the dark, at different ages, for the experiments. Age of seedlings was measured from the time the soaking started. In some experiments 2-cm apical sections were cut from 6-day old seedlings and used as experimental material. In experiments in which 1 day old seedlings were tested, the dry seeds were placed directly into 50 ml flasks, containing 2 ml of water or the test solution. Dwarf pea seeds (Pisumn sativuins L. var. Progress No. 9) were germinated in the same way.In other experiments seeds of radish (Raphantus sativus L. var. Early Scarlet Globe), bean (Phaseolius vulgaris L. var. Tendergreen Improved), cucumber (Citrumis sativus L. var. Boston Pickling), 2029www.plantphysiol.org on May 10, 2018 -Published by Downloaded from

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