Biosynthesis of vitamin C during germination

Summary

The effects of various cultural and environmental factors on the biosynthesis of ascorbic acid in germinating seeds have been studied. It is observed that treatments with manganese ions, over a range concentrations, and in different ways, are ineffective in bringing about any change in ascorbic acid or dehydroascorbic acid formation, or in the distribution of these constituents in the various parts of the seedling. Similar results are obtained with magnesium ion, while boric acid treatment slightly enchances ascorbic acid synthesis.

Treatments with different nitrogenous, phosphatic and potassic fertilizers, plant hormones, and colchicine, result in an inhibition of growth accompanied by a pronounced decrease in ascorbic acid formation in the earlier stages of germination. The extent of biosynthesis of vitamin C during germination of polyploid seeds is similar to that in hormone or colchicine treated seeds. Exposure of seedlings to ultraviolet rays is without significant effect on the synthesis of the vitamin,

Among other treatments studied, steeping of seed in the cold, and germination in the dark, effect pronounced increases in the biosynthesis of ascorbic acid, the latter being relatively more effective. Also, a cold treatment of the seed followed by germination in the dark results in greater formation of ascorbic acid than germination in the dark alone. With cold treatment, it is seen that the degree of effectiveness depends, within limit, on the duration of the treatment.

Addition of hexoses to nutrient media increases two-fold ascorbic acid formation in seed embryos; attempts to elaborate ascorbic acid from sugars through the growth of certain micro-organisms have not however been successful.

The observations are discussed in relation to the possible changes involved in the mechanism of the biogenesis of ascorbic acid in germinating seeds.