Effects of drought stress on some photosynthesis related parameters in commercial olive cultivars (Olea europaea L.)

Drought stress is one of the factors reducing olive yield in tropical and subtropical climates. In order to study the effects of different levels of drought stress on some photosynthetic parameters and related traits, a factorial completely randomized design with six replications was carried out in Taroum Olive Research Station greenhouse. 4 levels of water stress, including 25 %, 50 %, 75 % and 100 %(control) of field capacity, were applied on one-year-old seedlings of six commercial olive cultivars, including Arbequina, Amigdalolia, Abou-Satl, Konservolia, Manzanilla and Zard during 60 days. A significant difference was recorded between stress levels in terms of carotenoid content, stomatal conductance, transpiration rate and photosynthesis rate (at p≤0.1% level), chlorophyll a and dry biomass (at p≤1% level,) and instantaneous water use efficiency (at p≤5% level). Furthermore, significant difference was observed among cultivars in terms of Chlorophyl a, carotenoid content, stomatal conductance, transpiration rate and dry biomass (at p≤0.1% level), intrinsic water use efficiency (at p≤1% level) and instantaneous water use efficiency (at p≤5% level). According to the means comparison table drought stress reduced all measured traits. But, under drought stress levels of 25 and 50 % of field capacity, both instantaneous and intrinsic water use efficiencies were increased. Also among different cultivars, stomatal conductance, transpiration rate and water use efficiency were correlated to each other. Abou-Satl and Arbequina cultivars showed higher resistance to drought stress than other cultivars. Therefore, these cultivars can be introduced as drought tolerance cultivars for breeding programs and cultivation in arid conditions.