SUGARS EXCHANGES BETWEEN VESSELS ASSOCIATED CELLS AND XYLEM VESSELS, IN RELATION WITH THE TEMPERATURE, IN WALNUT

During winter, walnut exhibits stem pressure variations depending on temperatures and due to water and sugars fluxes between the different compartments of the wood. In order to quantify the fluxes of sugars between parenchyma cells and xylem vessels in winter we have developed experimental methods to study separately the efflux and influx processes. In order to investigate the effect of temperature on each component, one-year-old twigs of walnut were conditioned during 48h at 1°C or 15°C before measuring sugar fluxes. The efflux was quantified by the enrichment in sugars, within one hour, in a saline solution which was substituted to the original xylem sap. The influx was quantified by the absorption of 14C-sucrose by parenchyma cells. The results show a clear effect of temperature on sugars fluxes. The efflux is very high at 1°C but close to zero at 15°C. At the opposite, the influx is independent of temperature during the winter but more important at 15°C than at 1°C in March. The efflux increased throughout the period of sampling. On the other hand, the influx is stable and low during winter. In March, the influx intensity is twice as high as in winter. In March, influx was correlated with xylem sap pH nut not during winter.

IV International Walnut Symposium

V. Valentin, T. Améglio, A. Lacointe, J.L. Julien, G. Petel

sugar efflux, sugar influx, carbohydrates, contact cell, vessel-associated cell, temperature, water relation, stem pressure, sap osmolarity, xylem sap pH.

https://doi.org/10.17660/ActaHortic.2001.544.40