Ion content and its correlation with some physiological parameters in olive cultivars in response to salinity

Olive (Olea europaea L.) is one of the most valuable and widespread fruit trees in Iran. Salt stress-induced changes in membrane stability, photosynthesis and antioxidant enzyme activity were examined on four olive cultivars (Dakal, Shiraz, Zard and Amigdalifolia) by emphasizing the correlation between measured parameters and ion (K+, Na+) accumulation. Plants were subjected to four salt treatments (0, 100, 150 or 200 mM NaCl) under greenhouse conditions. The exposure of the olive plants to increased salinity resulted in a decline in relative leaf chlorophyll content (RLCC), photosynthesis rate (Pn), transpiration rate (E) and leaf and root K+ content. NaCl increased superoxide dismutase (SOD) and peroxidase (POX) activity of olive leaves. Increasing the concentrations of NaCl in soil increased the concentration of Na+ in the leaves and roots. Differences in the effectiveness of Na+ exclusion mechanism among cultivars at high salinity reflected differences in salt tolerance. ‘Zard’, the better-adapted cultivar, displayed tolerance to high internal salt concentrations without apparent cell damage. Relationships between parameters involved in salinity response are discussed in relation to ion accumulation in leaves and roots of olive cultivars.