|Perez-Pena, Jorge - WASHINGTON STATE UNIV|
Submitted to: American Journal of Enology and Viticulture
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 2004
Publication Date: December 1, 2004
Citation: Perez-Pena, J., Tarara, J.M. 2004. Using whole-vine photosynthesis to understand the effects of water stress on premium wine grapes. American Journal of Enology and Viticulture. 55(3) p. 298A. Technical Abstract: A six-chamber, mobile field laboratory was used to measure whole-vine photosynthesis on field-grown Vitis vinifera cv. Cabernet Sauvignon under three regimens of regulated deficit irrigation (RDI): 1) standard RDI (70% of vine evapotranspiration (ET) replaced weekly); 2) early deficit (50% of vine ET replaced weekly between fruit set and veraison); and 3) veraison deficit (50% of vine ET replaced weekly between veraison and harvest). When not under 50% deficit, vines in scenarios #2 and #3 were irrigated according to standard RDI. After harvest all vines were well irrigated. Whole-vine chambers were deployed for 7-day measurement runs during physiologically important stages: fruit set, pre- and post-veraison, and pre- and post-harvest. Chambers measured simultaneously two vines per treatment for 48 hours, then the chambers were moved to nearby vines until six vines per treatment were sampled. Single-leaf measurements of photosynthesis were collected at the same time as the whole-vine measurements. Large differences were observed in net carbon exchange and in transpiration between vines under the standard RDI practice and those under the additional water stress. In the pre-veraison period, 'early deficit' vines fixed up to 40% less carbon during the middle of the day than did vines under standard RDI. A similar reduction was observed in sunlit, single leaves measured independently of the whole-vine chambers. Vines under early deficit transpired up to 62% less than those under standard RDI. Only small differences were detected in net carbon exchange and transpiration before and after harvest, when daytime temperatures were lower and day length was shorter.