Abstract
The weight of tubers and contents of starch and vitamin C of potatoes (Solanum tuberosum L., cv. Kitaalcari, cv. Irish Cobbler) increased during tuber development and reached maximum at the end of July or at the early August. The activity of L-galactono-γ-lactone dehydrogenase (EC 1.3.2.3, GLDHase) increased during tuber development and reached maximum just before the time when vitamin C content reached the maximum value, and then decreased.
When tubers of 7 cultivar varieties of potatoes including cv. Irish Cobbler, cv. Kitaalcari, cv. Tsunika, cv. Touya, cv. Hokkai 79, cv. Shimakei 575 and cv. Shimakei 571 were stored at 4°C within 10 days after the harvest at about 20°C, vitamin C contents were markedly decreased during one month after storage and then decreased gradually for 3 months by 50∼70%. When tubers were stored at 4°C, both ascorbic acid (AsA) content and GLDHase activity increased after 2 days, and decreased thereafter. The decrease in vitamin C content during cold (4°C) storage was larger than that of storage at 15°C, and GLDHase activity was higher in 4°C-storage tubers than that in 15°C-storage tubers. These results suggest that AsA is supplied by the increased GLDH ase activity when a large amount of AsA is exhausted by a strong low temperature stress.
