Effect of water stress on some biochemical changes in leaf of five olive (Olea europaea L.) cultivars

The biochemical responses of five olive cultivars to water stress were evaluated in order to develop diagnostic indicators for olive tree susceptibility. One-year-old rooted olive cutting (Olea europaea L.) of cvs. Mary, Zard, Roghani, Bladi and Mission grown in 14-liter pots containing a mixture of sandy loam soil (24% silt, 14% clay and 62% sand), were subjected to various levels of water stress during two growing seasons in 2001 and 2002. Irrigation treatments were control (soil water at field capacity, Psi(soil) = -0.03 MPa), medium stress (Psi(soil) = -0.5 MPa) and severe stress (Psi(soil) = -1.5 MPa). A factorial experiment based on randomized complete block design was used. Results indicated that the degree of water stress had a significant effect on the amount of free proline, soluble carbohydrates, chlorophyll a, b and carotenoids. Exposure of plants to drought conditions led to noticeable increases in free proline and soluble carbohydrate concentration specifically related to each cultivar. Cultivars Mary and Bladi had higher amount of free proline and soluble carbohydrates under drought stress in comparison to other cultivars. The amount of chlorophyll a, b and carotenoid significantly decreased under drought stress conditions. The amount of chlorophyll a, b and carotenoid reduction was related to the degree of drought stress and cultivar. Generally, Bladi, Mary, Roghani, Zard and Mission showed a better performance under drought stress in that order.