EFFECTS OF SALINE STRESS IN TWO CULTIVARS OF OLEA EUROPEA L: 'ARBEQUINA' AND 'BARNEA'

Soil salinity is a major cause of plant stress leading to economic losses in world agriculture. The aim of this study is to provide information about the effects of salinity on the growth of young olive trees (Olea europaea L. ‘Barnea’ and ‘Arbequina’) and to identify some of the underlying physiological mechanisms. One-year-old plants were planted in 30-L pots, using a sand, perlite, peat (1:1:1) soil substrate. Each treatment was drip irrigated with a NaCl solution: 4 dS/m (25 mg NaCl); 6 dS/m (37.8 mg NaCl); 8 dS/m (50 mg NaCl) and a control treatment of 2 dS/m (no NaCl added). Growth in both cultivars decreased after a period of exposure to salinity, ‘Barnea’ being the most affected cultivar. In both cultivars leaf water potentials were reduced when NaCl concentrations were increased. The osmotic potential became more negative when salt concentrations increased, thus indicating that both cultivars perform osmotic adjustment. The relative water content (RWC) did not change with the different saline treatments, suggesting that both cultivars present mechanisms to maintain water content even under stress conditions. On the other hand, high salinity levels induce ionic imbalance given higher Na⁺ and Cl^- concentration in leaves and roots. As a result of the accumulation of these ions, the K⁺ concentration decreased resulting in a low ratio of K⁺/Na⁺. Both cultivars showed symptoms of toxicity in leaves and shoots which indicates that they accumulate toxic ions in the youngest leaves. ‘Arbequina’ showed higher Cl^- concentrations in their root tissues over the concentrations in leaves, suggesting that there is a mechanism of Cl^- compartmentalization at stem or root level that prevents entry and accumulation of Cl^- in the leaf. ‘Barnea’ leaves were more damaged than those of ‘Arbequina’ and accumulated higher Cl^- concentration, indicating that ‘Barnea’ is less resistant to salinity.