Physiological and biochemical responses to water deficit and recovery of two olive cultivars (Olea europaea L., Arbequina and Empeltre cvs.) under Mediterranean conditions

The main objective of the present study was to evaluate the responses to water deficit stress and recovery capacity of young potted trees from two olive cultivars, Empeltre cv. and the widely planted Arbequina cv. The experiment was carried out under semiarid environmental conditions at the experimental field of the University of Balearic Islands in Mallorca, Spain. Two-year-old plants in 22 L pots were exposed to three water availability regimes (full capacity [FC]; 50% FC; 30% FC). Growth, gas exchange, intrinsic water use efficiency, C-13 discrimination and biochemical parameters (total soluble sugars, proline, starch, total soluble protein, pigments and phenolic fraction) were evaluated. Plants were rewetted and assessed again after the re-watering period. Drought stress reduced photosynthesis, mainly by regulating stomatal conductance (g(s)). Arbequina cv. exhibited a more conservative water use strategy than Empeltre, with greater reductions in g(s), accompanied by significant reductions in vegetative growth. Non-significant differences in intrinsic water use efficiency were observed between cultivars and treatments. However, C-13 discrimination analysis showed better water use efficiency in Empeltre than Arbequina in all treatments. Water deficit stress caused an increase of proline and total soluble solids and a reduction of starch, total soluble protein and chlorophylls concentrations of both cultivars. Empeltre showed a higher total phenol concentration than Arbequina during non-water deficit stress conditions. Cultivar-specific differences in the mechanisms to deal with drought were observed. Empeltre cv. exhibits a higher capacity to tolerate drought and it continues growing under water stress and recovery.