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The relationship between carbohydrate metabolism and tuber initiation in potato was determined by monitoring changes in the amount of starch and sugars along with the activities of sugar metabolizing enzymes upon transfer of plants to tuber-inducing conditions (TI; short days, cold nights) from non-inducing conditions (NTI: long days, warm nights). Switch to TI conditions caused an immediate slow-down in plant growth and triggered swelling of stolon tips, which went on to develop into tubers. Leaves of plants moved to TI conditions accumulated less starch and sugar while their stolon tips showed a sudden upsurge in starch content and a sharp decline in sugars even before any tip swelling was detectable. These changes were paralleled by a transient surge in the activity of cell wall invertase (74%) and soluble invertase (30%) in stolon tips of plants transferred to TI conditions in two unrelated cultivars under different experimental conditions. As the surge in invertase activity faded, it was replaced by a substantial increase in sucrose synthase activity as the tuber enlargement proceeded. The transient increase in invertase activity just prior to tuber initiation appears to mark a turning point in the transition of stolon tip to tuber. [ABSTRACT FROM AUTHOR]

Seeds of Hibiscus esculentum were analyzed for growth, in terms of fresh and dry weights, cell size, water content, reducing and non-reducing sugars and acid invertase activity. On the basis of growth analysis seed development is divided into four distinct phases of a) cell division, d) cell elongation, c) dry matter accumulation and, d) maturation. A close parallel with water content and cell size was observed. A peak level of reducing sugars was observed during the rapid elongation growth. The role of invertase in hydrolyzing sugars and its regulation of sink development is discussed. [ABSTRACT FROM AUTHOR]