The Role of Buds and Gibberellin in Dormancy and the Mobilization of Reserve Materials in Potato Tubers

Abstract

Reducing sugar levels in potato tubers increased up to eight-fold during storage from October to May, with almost all the rise occurring after emergence from dormancy in December. Removal of all buds from the tubers within a month of harvest prevented this rise in soluble carbohydrate, but application of a lanolin preparation of gibberellic acid (GA₃ to the ‘eye’- positions completely substituted for the buds in permitting the same pattern and magnitude of sugar formation in the storage tissues. Discs of tuber tissue responded to exogenous GA₃ by forming reducing sugars only when obtained from non-dormant tubers. It is con cluded that both the buds and the storage tissues exhibit dormancy, and that breaking of this during after-ripening operates independently in the two regions, with the storage tissues becoming responsive to bud-synthesized gibberellin only after they have themselves emerged from the dormant condition. Levels of activity of starch phosphorylase, amylase and acid phosphatase in the storage tissues rose markedly after emergence from dormancy, but neither disbudding nor exogenous gibberellin had any quantitative or qualitative effect on these enzymes. Thus, it appears that neither enzyme synthesis nor enzyme activation was stimulated by gibberellin, and it is suggested that gibberellin regulation of the mobilization of the reserve materials is achieved, at least initially, through effects on cell compartmentation.