Kinetin-induced tuberization of potato in vitro : on the mode of action of kinetin

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The tuberization percentage of etiolated potato (Solanum tuberosum L.) sprout sections cultured in vitro in the absence of kinetin was 61% (endogenous tuberization potential). The presence of 5 mg/liter kinetin in the medium increased tuberization to 94%.In α time course experiment soluble ADP glucose: a-1,4-glucan α-4-glucosyl transferase (starch synthetase) activity extracted from etiolated sprout sections cultured in vitro remained low (one twenty-fifth of the activity present in the mother tubers at time 0), and was almost constant throughout 21 days of culture. No difference in activity was found in sections grown in kinetin-containing medium in comparison with those grown in the absence of kinetin. During tuber initiation of etiolated potato stolons cultured in vitro, kinetin caused stimulation of phosphorylase activity which continued until the late stages of tuberization when it also stimulated ADP glucose pyrophosphorylase activity. Kinetin did not affect amylase activity. Addition of 11 mg/liter kinetin to the enzyme reaction mixture did not change the activity of soluble starch synthetase in vitro. The net accumulation of starch caused by kinetin was partially the result of the stimulation of starch biosynthesis through phosphorylase at an early stage, and both phosphorylase and pyrophosphorylase at a later stage.
日本植物生理学会の論文