Incorporation of Carbon-14 into the Complex Polysaccharides of Plants

Abstract

THE carbon-14 tracer technique would appear to offer a unique opportunity for investigations of the biosynthesis and subsequent metabolism of pectins and hemicelluloses, provided that there is a measurable synthesis and turnover of these polysaccharides in plant tissues. After allowing four mature fruiting spurs, each with four to six leaves and two fruits, detached from plum trees (variety Victoria), to photosynthesize¹ in the presence of carbon-14 dioxide (from 43.5 µc. barium carbonate-¹⁴C), the leaf polysaccharides and the water-soluble polysaccharides of the fruit mesocarp were isolated. Labelling of all the monosaccharide constituents was observed by hydrolysing the polysaccharides (N sulphuric acid ; 100° 16 hr.), separating the products on paper chromatograms and examining with a Geiger counter those areas containing the separated sugars. The specific activities of the latter were determined, after elution from the paper chromatograms, as infinitely thin films on planchets (see Table 1). The incorporation of carbon-14 into the fruit mesocarp polysaccharides may be due to photosynthesis by the fruit or by translocation from the leaves.