Starch degradation and sucrose metabolism during anaerobic growth of pondweed (Potamogeton distinctus A. Benn.) turions

Abstract

Stem growth in pondweed (Potamogeton distinctus A. Benn.) turions was stimulated in anaerobic conditions. Decreases in starch contents in turion cells, the number of amyloplasts in a cell and sizes of starch granules in amyloplasts clearly showed enhancement of starch consumption in turions during anaerobic growth of stems of pondweed. Although the total activities of both α-amylase and starch phosphorylase were not stimulated by anaerobic conditions, the activities of one amylase and two isozymes of starch phosphorylase, separated by native polyacrylamide gel electrophoresis, were enhanced in anaerobic conditions. The sucrose content in turion cells decreased rapidly in the early stage of anaerobic growth but then remained constant after the enhanced growth had started, suggesting active sucrose metabolism. The activities of sucrose-phosphate synthase, sucrose synthase and acid invertase, measured in vitro, were enhanced in extracts from turions in anaerobic conditions. The induction of the activity of sucrose synthase was most significant, suggesting that sucrose synthase plays an important role in sucrose metabolism in pondweed turions growing in anaerobic conditions.