Biphasic response of cucumber hypocotyl sections to auxin

概要

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The pattern of the response to auxin of cucumber hypocotyl sections, its relation to acid-induced growth and the role of the epidermis were investigated. In long-term incubation. IAA had practically no effect on sections without epidermis (peeled sections). Time course measurements showed that the response to IAA of nonpeeled sections was biphasic; the first phase started right after IAA treatment and continued for about 1 hr, then after a period of 1 hr with a greatly decreased growth rate the second phase started with a higher rate. Peeled sections lacked the second phase; their growth rate in the first phase depended on the acidity of the incubation medium. These results were confirmed by utilizing one side-peeled sections and measuring the curvature of the sections which represented the difference in the growth rate between the peeled and nonpeeled sides. The following points were suggested. The first phase resembles acid-induced growth and the growth capacity is limited by the epidermis; the second phase is specific to auxin and requires the presence of the epidermis. The first phase was hardly influenced by temperature, while the second one was greatly affected; its Q_<10> being more than 4.0, suggesting that the first phase is of physical nature.
日本植物生理学会の論文