Abstract
Tuber formation in the strictly short day-dependent potato species Solanum demissum Lindl. was studied. In order to accurately determine the developmental stage of individual stolon tips, a reliable parameter describing tuber formation is defined. Dry matter percentage of stolon tips was highly correlated with starch concentration and with swelling of the stolon tips, independent of plant age and stolon diameter. Based on this parameter, changes in carbohydrate metabolism during the initial stages of tuber formation were analyzed. Glucose and fructose levels decreased significantly upon tuber formation. This decrease could be explained by a change in sucrose hydrolysis, dominated by acid invertases before tuber formation, and by sucrose synthase afterwards. A model of the temporal and spatial changes in sucrose unloading and hydrolysis in swelling stolon tips is discussed. The observed changes in carbohydrate metabolism are similar to changes observed in a simplified in vitro system, indicating that such model systems adequately reflect tuber development in intact plants.
Key words
Invertase - sucrose synthase - sugar metabolism - tuber formation
