|Perez Pena, Jorge - WSU|
Submitted to: Northwest Center for Small Fruit Research Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 4, 2003
Publication Date: December 5, 2003
Citation: TARARA, J.M., PEREZ PENA, J. USING WHOLE-VINE PHOTOSYNTHESIS TO UNDERSTAND THE EFFECTS OF WATER STRESS ON PREMIUM WINE GRAPES. NORTHWEST CENTER FOR SMALL FRUIT RESEARCH PROCEEDINGS. 2003. Technical Abstract: A six-chamber, mobile field laboratory was used to record measurements of whole-vine photosynthesis from mature, field-grown Vitis vinifera cv. Cabernet Sauvignon under three regimes of regulated deficit irrigation (RDI): 1) standard RDI, in which 70% of vine evapotranspiration (ET) is replaced weekly; 2) early deficit, in which 50% of vine ET is replaced weekly between fruit set and veraison; and 3) veraison deficit, in which 50% of vine ET is replaced weekly between veraison and harvest. When not under 50% deficit, vines in scenarios #2 and #3 were irrigated according to standard RDI practice. Irrigation was delivered by drip. Vines were own-rooted, planted in 1992 in rows oriented N-S, with spacing of 6 feet between vines and 9 feet between rows, at the Canoe Ridge vineyard of Stimson Lane Vineyards & Estates, west of Paterson, WA. Whole-vine chambers were deployed for 7 to 8-day measurement runs during physiologically important stages: fruit set, pre- and post-veraison, and pre- and post-harvest. Chambers were installed on two vines per treatment, data collected for 24 to 48 hours, then the chambers moved to nearby vines until six vines per treatment were sampled. On adjacent non-chambered vines, single-leaf measurements of photosynthesis were collected at the same time as the whole-vine measurements. Leaf tissue was collected for laboratory analysis of the diurnal dynamics of starch and sugar concentrations. Periodic measurements of chlorophyll fluorescence and the photosynthetic light response in individual leaves also were recorded. Leaf area per vine was estimated at the end of each week-long measurement run. 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. Such results are not unexpected, as other research has suggested drought-induced downregulation of both transpiration and net carbon assimilation, and that an increase in water use efficiency can be computed when the decrease in net carbon exchange is dominated by stomatal closure. Differences in net carbon exchange and transpiration were smaller after harvest, when all vines were watered more liberally to encourage late-season storage reserves and cold acclimation.