Effect of Soil Moisture Stress on Physiological Response in Grape (Vitis vinifera L.) Varieties

Four varieties of grape namely Flame Seedless, Thompson Seedless, Sharad Seedless and Tas-A-Ganesh were subjected to different levels of moisture stress to study their physiological response. Stress was imposed for 14 days by withholding irrigation. Observations on relative water content, leaf water potential, leaf osmotic potential and gas exchange parameters like photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency (WUE) were recorded. None of the varieties could survive for 14 days without irrigation (100% stress). Flame Seedless and Thompson Seedless at 50% moisture stress maintained higher turgidity as indicated by lesser reduction in relative water content and water potential attributed to better osmotic adjustment. Marginal reduction in photosynthesis and greater reduction in transpiration rate in the variety Flame Seedless may have resulted in higher WUE under moisture stress. Higher photosynthetic rate, lower transpiration rate, higher water relation parameters and high WUE in Flame Seedless under soil moisture stress indicated its better tolerance to drought.