Investigation of morphological and physiological responses of lettuce plants inoculated by Piriformospora indica under salinity stress

In order to evaluate morphological and physiological responses of lettuce plants inoculated/ non-inoculated with Piriformospora indica under salinity stress, a factorial experiment on the basis of randomized complete block design (RCBD) with three replications was carried out under greenhouse conditions. Main factor was consisted of inoculated or non-inoculated seeds with the fungus and the sub-factor included three levels of irrigation water salinity (tap water with EC=0.8 dS/m as control and saline water with ECs of 4 and 8 dS/m). Salinity stress significantly decreased most of growth parameters and P. indica declined the adverse effects of salinity. An increase in fresh foliage weight and leaf area observed for plants inoculated with P. indica. These plants showed less leaf damage symptoms under stress condition. Inoculation by the fungus significantly increased the volume and length of root in comparison with control plants. Inoculated plants contained higher concentration of proline, photosynthetic pigments and catalase enzyme activity in their leaves rather than control plants. The lowest ionic leakage was observed in P. indica-inoculated plants at EC=4 dS/m. The results revealed the usefulness of P. indica fungus in production of lettuce under salinity stress up to 4 dS/m. But inoculation with the fungus did not lead to desirable results at 8 dS/m.