Abstract

Changes in sucrose metabolism in response to Na⁺-salt and Cl^- -salt stresses were measured in tomato cultivar liaoyuanduoli (Lycopersicon esculentum Mill.) and its objective was to provide a new evidence for the ion-specific stress effects of Na⁺and Cl^- on sucrose metabolism of tomato fruits. The carbohydrate contents, as well as sucrose metabolizing enzymes activities were determined. The results indicated that hexoses (fructose and glucose) accumulated to higher levels and the content of sucrose and starch were lower in matured fruit under salt stress treatments, which accumulated more hexoses under Na⁺-salt stress than under Cl^- -salt stress. Na⁺-salt stress and Cl^--salt stress enhanced the acid invertase and decomposition direction of sucrose synthase activities of tomato fruit in a long period of time (30-60 days after anthesis), but little variation of sucrose-phosphate synthase and synthesis direction of sucrose synthase activities were observed. The sucrolytic activities were linked to changes in soluble sugar levels but not with the activities of sucrose biosynthetic. These results point to the importance of sucrolytic activities in sucrose metabolism of tomato fruit under salt stress; the effect of Na⁺ was more severe than that of Cl^-.

Key words: Salt stress, Na⁺-salt, Cl^- -salt, sucrose metabolism.