Conversion of L-Galactono-γ-lactone into L-Ascorbic Acid by Plants

Abstract

IT has been inferred from feeding-experiments that cress seedlings¹, and also pea and mung bean mitochondria², are capable of converting L-galactono-γ-lactone into L-ascorbic acid. Similar results were obtained with mitochondria from cabbage leaves and cauliflower florets, and a relatively specific L-galactono-γ-lactone dehydrogenase was isolated from the latter³. The results (Table 1) confirm that this system may not be uncommon in the higher plants ; Sphagnum, Spirogyra and Psalliota‡ gave inconclusive results. The figures in Table 1 are either the mean of duplicate estimations, or are taken from single, extended experiments which show how the concentration of ascorbic acid in the tissue varies during the period of feeding. Fig. 1 shows the results of one such extended experiment with parsley, in which the concentration of ascorbic acid in the laminæ fed with the lactone rose, during a period of 190 hr., from 1,582 to 12,010 mgm./100 gm. dry-weight, that is, to approximately 12 per cent of the dry weight. During the same period, the value for the controls in de-ionized water fell gradually to 1,120 mgm./100 gm. dry weight, and at this time the experimental laminæ possessed more than ten times the concentration of ascorbic acid in the controls.