THE BIOSYNTHESIS OF POLYSACCHARIDES. INCORPORATION OF D-(1-14C)GLUCOSE AND D-(6-14C)GLUCOSE INTO PLUM-LEAF POLYSACCHARIDES.

1. The utilization of specifically labelled d-glucose in the biosynthesis of plum-leaf polysaccharides has been studied. After these precursors had been metabolized in plum leaves, the polysaccharides were isolated from the leaves, and their monosaccharide constituents isolated and purified. 2. Both the specific activities and the distribution of (14)C along the carbon chains of the monosaccharides were determined. Significant (14)C activity was found in units of d-galactose, d-glucose, d-xylose and l-arabinose, but their specific activities varied widely. The labelling patterns suggest that in the leaves the other monosaccharides all arise directly from d-glucose without any skeletal change in the carbon chain, other than the loss of a terminal carbon atom in the synthesis of pentoses. 3. The results indicated that within the leaf there are various precursor pools for polysaccharide synthesis and that these pools are not in equilibrium with one another.