Showing papers by "Jeffrey C. Suttle published in 2001"

Dormancy-related changes in cytokinin efficacy and metabolism in potato tubers during postharvest storage

Abstract: The metabolism of [3H]-zeatin (Z) and[3H]-isopentenyladenosine (IPA) in potato tubers was examined inrelation to changes in cytokinin efficacy during postharvest storage anddormancy progression. Exogenous radiolabeled cytokinins were rapidlymetabolizedby dormant and nondormant tubers. Following injection, [3H]-Z wasmetabolized to zeatin riboside, adenine derivatives andzeatin-riboside-5′-monophosphate. Four hours after injection, less than60% of the recovered radioactivity was associated with unmetabolized[3H]-Z. [3H]-IPA was also rapidly metabolized to severalmetabolites including: IPA-5′-monophosphate, adenine derivatives andzeatin riboside. Four hours after injection, less than 50% of therecovered radioactivity was associated with [3H]-IPA. Cytokininsensitivity was assessed by determining the effects of exogenous Z or IPA ontuber sprouting. Immediately after harvest and during the initial period ofstorage, tubers were dormant and exogenous Z or IPA were completely ineffectivein breaking tuber dormancy. Thereafter, dormant tubers exhibited a gradualincrease in sensitivity to both cytokinins. Cytokinin sensitivity continued toincrease as postharvest storage was extended and dormancy weakened. The lengthof postharvest storage (hence dormancy status) had no apparent effects on themetabolism of either cytokinin. Neither the rate of metabolism nor the natureofmetabolites detected was affected by the length of postharvest storage. Theseresults suggest that changes in cytokinin efficacy in dormant potato tubersduring postharvest storage are not the result of differential catabolism butrather are due to other cellular processes such as hormone perception and/orsignal transduction.