ASCORBIC ACID FORMATION IN POTATO TUBER SLICES

The occurrence of ascorbic acid in plants and the environmental, nutritional and genetic factors involved have been widely studied but little is known about the actual mechanism of its formation. Previous work on this problem has been chiefly with germinating seedlings (15, 16) or leaf tissue (1, 24, 25) in which photosynthesis or rapid growth also occurred. The accumulation of ascorbic acid in potato tuber tissue, pointed out by GUTHRIE (11), STEWARD and PRESTON (26), PROKOSHEV (19), and others, indicated, therefore, that this might be favorable material for studying ascorbic acid synthesis, especially in relation to respiration. Sugars have most frequently been suggested as precursors of ascorbic acid in plants (1, 6, 15, 20) and there is evidence relating the process to both photosynthesis (24, 25) and respiration (11, 19, 26). However, the most concrete suggestion for a mechanism of ascorbic acid synthesis has come from the work of SMYTHE and KING (23) who showed that certain glycolytic intermediates may increase synthesis in rat tissues. This paper reports (a) a technique for comparing ascorbic acid synthesis and respiratory capacity in potato tuber slices, (b) further identification of the ascorbic acid formed, and (c) evidence that glycolysis is involved in the formation.