Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 28, 1998
Publication Date: N/A
Technical Abstract: Previous research has implicated endogenous cytokinins as natural dormancy-terminating agents in potato (S. tuberosum L.) Tubers. An increase in both total and bioactive cytokinins preceded the onset of tuber sprouting. Injection studies have shown that the efficacy of exogenous isopentenyl-adenosine (IPA) and zeatin(Z) changed during tuber dormancy. Immediately after harvest and during the initial period of post harvest storage, injection of these cytokinins did not stimulate sprouting. Thereafter, the sensitivity towards both of these cytokinins increased in both a time- and dose-dependent manner. The observed changes in cytokinin efficacy could be a result of changes in receptor/signal transduction dynamics or could be a result of metabolic inactivation. In order to determine the role of metabolism in the observed changes in cytokinin efficacy, the fates of exogenous tritiated IPA and Z were followed during postharvest storage. In both dormant and non-dormant tubers, both IPA and Z were rapidly metabolized and exhibited half-lives of ca. Four hours or less. The principal metabolites of IPA were: Ade/Ado, and IPA-5'-monophosphate, while the principal metabolites of Z included: Ade/Ado, X-5'-monophosphate and ZR. The rapid and progressive accumulation of labeled adenine derivatives suggests that tubers posses an active cytokinin oxidase system which preferentially oxidized IPA relative to Z. The effects of dormancy status on cytokinin metabolism are currently under investigation and will be reported.