Physiological response of grapevine rootstock cultivars to moisture stress

Five rootstock cultivars, viz. Dogridge, Salt Creek, 1613, St. George and Vitis champini clones, and Thompson Seedless were observed for their physiological responses under different moisture-stress conditions (100%, 50% and the control). Moisture stress was imposed in potted plants by withholding the watering. Observations were recorded on photosynthesis (Pn), transpiration (E), stomatal conductance (Gs), leaf water potential (Yl), osmatic potential (Ys) and relative water content (RWC). Most of the cultivars did not survive beyond 4th day of moisture stress except Dogridge and Salt Creek. The maintenance of turgidity in both these cultivars as indicated by lesser reduction in RWC attributed to better osmotic adjustment. The reduction in photosynthesis was attributed to the concomitant reduction in stomatal conductance. The marginal reduction in the photosynthesis in Dogridge compared to other cultivars, suggested a better tolerance level in this cultivar.