ISHS Acta Horticulturae 442: III International Walnut Congress
CARBON AND WATER FLUXES IN VEGETATING 3-YEAR-OLD WALNUTS |
| Authors: | A. Lacointe, T. Améglio, A. Kajji, F.A. Daudet, P. Cruiziat, P. Archer, J.S. Frossard |
| Keywords: | Photosynthesis, 14C labeling, reserves, water stress |
| Abstract:
The daily net carbon gain of young walnut trees was measured over the whole season through gas exchange measurements, and the spatial and biochemical partitioning of the incoming carbon was investigated through isotopic labeling in summer and fall. Daily fluxes of recent photoassimilates into the different organs and functions were derived from combining these two complementary information's. The translocation pattern, already highly basipetal in summer, became even more so in fall; in the same time, the daily fluxes of recent photoassimilates incorporated into all biochemical fractions decreased sharply at the whole plant level, and the metabolic rate slowed down. However, not all organs changed their activity to a similar extent, particularly among the different components of the root system. In contrast to the C fluxes incorporated into plant dry matter, the fluxes allocated to respiration were only little affected. In parallel, water fluxes were investigated, both at the day-and the infra-day level. An average of ca. 7 liters daily were transported through the transpiration stream for correctly irrigated trees. During a normal summer day, absorption lagged transpiration and dehydration leading to shrinkage. In the evening and night the situation reversed and plants rehydrated. The fine dynamics of sap flow and stem diameter allow a precise monitoring of the water status. The effects of drought on both fluxes and their interaction are briefly discussed. | |
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