CARBOHYDRATE-METABOLISM DURING DORMANCY AND SPROUTING IN YAM (DIOSCOREA) TUBERS - CHANGES IN CARBOHYDRATE CONSTITUENTS IN YAM (DIOSCOREA) TUBERS DURING DORMANCY AND SPROUTING

Changes in carbohydrate constituents were stuided in tubers of Dioscor ea rotundata, Dioscorea alata, and Dioscorea esculenta during dormancy and sprouting for a period of 90 days. Decrease in starch content (35 %) was the most significant change observed in all yam species. This d ecrease was reflected in proximal, middle, and distal regions of tuber s. More than 50% of the starch reduction took place during the dormanc y period. The mobilization of starch to sugars and its utilization was reflected in fluctuating levels of reducing and nonreducing sugars du ring presprouting/sprouting periods. Changes were also observed in the amylose fraction in starch. Chromatographic sugar analysis in tubers indicated the presence of glucose and sucrose in fresh tubers. Fructos e and maltose were detected during dormancy/sprouting periods.