SELECTIVE DIFFUSION OF BASIC AND ACIDIC PRODUCTS OF CO2 FIXATION INTO TRANSPIRATION STREAM IN GRAPEVINE

When 14CO2 was supplied to the leaf of a grape-vine shoot, radioactivity was found in the wood of the shoot and in the fluid extracted by suction from the wood adjacent to the fed leaf. Some radioactive material was transported upwards in the transpiration stream but the labelled compounds were not representative of the labelled compounds either in the wood or in the vacuum-extracted sap. The results suggest that labelled glutamine aaand malic acid are selectively released into the transpiration stream and partly reabsorbed by the surrounding tissues higher up the shoot, where they are converted to glutamic, aspartic, γ-amono butyric, and citric acids. Any labelled sugars entering the transpiration stream are preferentially reabsorbed from it. © 1969 Oxford University Press.