Differential Salt Sensitivity of Two Flax Cultivars Coincides with Differential Sodium Accumulation, Biosynthesis of Osmolytes and Antioxidant Enzyme Activities

Abstract

The present study was conducted in order to determine the response of two Egyptian flax cultivars (Sakha 102 and Sakha 105) to salt stress. To this end, seedlings of both cultivars were subjected to 150 mM NaCl condition, and the growth, Na+ and K+ concentrations, proline and hydrogen peroxide concentrations, and antioxidant enzyme activities were measured and compared with plants grown under non-stressed conditions. The results showed that salt stress reduced the overall growth of Sakha 102 by 38% as opposed to almost 50% reduction in Sakha 105. H2O2 significantly increased in Sakha 105, but remained unchanged in Sakha 102. The Na+ concentration in the leaf of Sakha 102 was 30% more than in the leaf of Sakha 105. The K+ concentrations were reduced by the same degree in all tissues of both plants and the Na+/K+ ratios were similar in both cultivars (generally > 1). The proline concentration was significantly more elevated in leaf, stem, and root of Sakha 102 (5.4, 2.5, and ten-fold, respectively) than in Sakha 105 (2.3, 2.3, and 4.0-folds). CAT activity markedly increased in the root of Sakha 102 (3.5-fold), but remained unchanged in Sakha 105. Taken together, these results suggest that Sakha 102 is more salt tolerant than Sakha 105, and that differences in proline concentration and ROS production under stress may account to a greater degree in the differential tolerance.