© 2004 Heron Publishing—Victoria, Canada
Winter variation in xylem sap pH of walnut trees: involvement of plasma membrane H+-ATPase of vessel-associated cells
Georges Alves (1), Thierry Ameglio (2), Agnes Guilliot (1), Pierrette Fleurat-Lessard (3), André Lacointe (2), Soulaïman Sakr (1), Gilles Petel (1) and Jean-Louis Julien (1, 4)
1. U.M.R. PIAF, site des Cézeaux, Université Blaise Pascal, 24 avenue des Landais, 63177 Aubière cedex, France / 2. U.M.R. PIAF, site INRA de Crouelle, 234 avenue du Brézet, 63039 Clermont-Ferrand cedex 2, France / 3. U.M.R. CNRS 6161, Bâtiment Botanique, 40 avenue Recteur Pineau, 86022 Poitiers, France / 4. Author to whom correspondence should be addressed (J-Louis.JULIEN@piaf.univ-bpclermont.fr) / Received November 26, 2002; accepted June 14, 2003; published online December 1, 2003
Summary
We studied seasonal variation in xylem sap pH of Juglans regia L. Our main objectives were to (1) test the effect of temperature on seasonal changes in xylem sap pH and (2) study the involvement
of plasma membrane H+-ATPase of vessel-associated cells in the control of sap pH. For this purpose, orchard-grown trees were compared with trees
grown in a heated (≥ 15 °C) greenhouse. During autumn, sap pH was not directly influenced by temperature. A seasonal change
in H+-ATPase activity resulting from seasonal variation in the amount of protein was measured in orchard-grown trees, whereas no
significant seasonal changes were recorded in greenhouse-grown trees. Our data suggest that H+-ATPase does not regulate xylem sap pH directly by donating protons to the xylem, but by facilitating secondary active H+/sugar transport, among other mechanisms.
Keywords:
Juglans regia, temperature, winter functioning.
