ISHS Acta Horticulturae 705: V International Walnut Symposium
WINTER BIOLOGY IN WALNUT TREE: FREEZING TOLERANCE BY COLD ACCLIMATION AND EMBOLISM REPAIR |
| Authors: | T. Améglio, G. Alves, M. Decourteix, M. M. Poirier, M. Bonhome, A. Guilliot, S. Sakr, N. Brunel, G. Petel, R. Rageau, H. Cochard, J.L.J. Julien, A. Lacointe |
| Keywords: | carbohydrate content, xylem sap, contact cells, vessel-associated cells, stem pressure, embolism refilling |
| Abstract:
During winter walnut exhibited freezing tolerance in living cells, but at the same time freezing damage in xylem vessels with embolism as a consequence of the frost- thaw alternation. Thus, loss of hydraulic conductivity reached near 100 % after the first frost, but varied during winter; this can be related to the ability of walnut to generate positive xylem pressure due to stem pressure. For the freezing tolerance, sucrose resulting from winter starch mobilization was an essential step on the way to acquisition of cold hardiness. Those seasonal changes of carbohydrate contents occurred under low temperatures during winter. But for walnut, beside that role for freezing tolerance, starch degradation and subsequent release of resulting sucrose into xylem vessels appeared also of major importance to repair embolism. These results show clearly that important relations exist between xylem water status, dynamics of the carbon reserves and temperature during winter. They also show the importance of winter biology in walnut tree to prepare the functioning of trees during the next vegetative period | |
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