Observations on the Incorporation of C14 into Tartaric Acid and the Labeling Pattern of D-Glucose from an Excised Grape Leaf Administered L-Ascorbic Acid-6-C14.

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Abstract
[long dash]The possible precursor relation of L-ascorbic acid to (+)-tartaric acid has been tested by adding 3 mg. containing 47 [mu]C. of L-ascorbic acid-6-C 14 to a single actively photosynthesizing grape leaf (var. Mission). After 8 hours in the light and 17 hours in the dark, the soluble constituents were separated by ion exchange and paper chromatographic procedures. The tartaric acid, after three recrystallizations as the K acid salt, contained only 24 cpm per mg carbon (80% efficiency). Nearly 50% of the activity remained in the neutral effluent from the ion exchange columns. Of this, 30% chromatographed as sucrose, and 5% each as glucose, fructose, and xylose. The D-glucose contained 100,000 cpm. per mg. carbon. Upon degradation with Leuconostoc mesenteroides, it gave a percentage distribution of activity as follows: carbon 1 (21.5), 2 (6.0), 3 (23.0), 4 (21.0), 5 (2.5), and 6 (26.0). The results suggest that tartaric acid is derived in a secondary manner from the carbohydrate pool of the leaf. Further, L. ascorbic acid is utilized by the leaf in a way closely associated with hexose and pentose metabolism. A possible pathway for the conversion of L-ascorbic acid to D-glucose is described.