Spinach was wilted up to 62% of the original weight (wilting treatment) and soaked in water to recover its weight and the appearance (soaking treatment). The changes in ascorbic acid contents and ascorbate oxidase activities of spinach leaves, stalks and roots were examined separately after the wilting treatment and also the soaking treatment. The following results were obtained.
1) Ascorbic acid contents and ascorbate oxidase activities differed in the parts of fresh spinach. Ascorbic acid content was the highest in leaves and the least in roots. About 46% of total ascorbic acid was dehydroascorbic acid in roots. On the other hand, the specific activity of ascorbate oxidase in roots was 200 times higher than that in leaves.
2) Ascorbate oxidase activities were increased in leaves and stalks after the soaking treatment in water at 30°C, when significant decrease in L-ascorbic acid was noted. However, no increase was observed in root after the same treatment in spite of the decrease in L-ascorbic acid.
3) No increase in ascorbate oxidase activity was observed in leaves after the soaking treatment in water at 10°C. Thus, it was inferred that this enzyme was concerned with the decrease in L-ascorbic acid of spinach leaves when they were soaked in water at 30°C, as one of the redox enzymes involving ascorbic acid.