Changes in lipid composition, water relations and gas exchange in leaves of two young 'Chemlali' and 'Chetoui' olive trees in response to water stress

The comparative responses of two young olive trees (Olea europaea L. 'Chemlali' and 'Chetoui') to drought stress were investigated during 1 month. Three-month-old own-rooted plants were subjected to two irrigation treatments: WW (well watered plants that were irrigated with fresh water to maintain a soil water content close to field capacity), and WS (water stressed plants by withholding water). Leaf water potential, gas exchange and leaf lipid composition were studied. 'Chemlali' was able to maintain higher leaf CO(2) assimilation rate and leaf stomatal conductance throughout the drought cycle compared to 'Chetoui'. Water stress induced a larger decrease in the total lipid content in 'Chetoui' than in 'Chemlali'. Interestingly, the constitution of different lipid classes was highly altered in 'Chetoui'. Lipid changes in Chemlali, a drought tolerant cultivar, revealed more stability of its cellular membranes to drought stress as compared to the drought susceptible olive cultivar, Chetoui. Furthermore, in comparison to the controls, drought stressed plants showed an increase in the degree of unsaturation of leaf lipids in the two olive cultivars. Moreover, the results observed in Chemlali showed that besides changes in lipids composition this cultivar may have an efficient defence strategy which can be related on antioxidative production against oxidative stress.