1. Discs of tobacco leaf lamina were floated on media containing D-[U-14C]glucose. Glucose uptake was mainly through the cut edges, and diffusion through the veins and intracellular spaces was slow. 2. Radioactivity was detected in all polysaccharide fractions extracted from the discs, including those associated with the wall. 3. Plasmolysis in sorbitol or KCL decreased the incorporation of radioactive material into all fractions. 4. Incorporation of arabinose into pectins was increased or unaffected by plasmolysis, but the incorporations of other sugars were decreased. Removal of the lower epidermis did not affect this result. 5. Seperate mechanisms for arabinan and polygalacturonorhamman syntheses must exist, and these must differ in their responses to the physiochemical, structural and organizational changes that accompany plasmolysis.
