Effects of Salicylic Acid on Growth Parameters, Proline Content and Antioxidant Activity of Lettuce Plants (Lactuca sativa L.) under Saline Soil Condition

Salinity stress is one of the important limiting factors in agricultural crops production. In order to evaluate salicylic acid (SA) application effects on lettuce growth parameters under salinity stress condition, a factorial experiment in a randomized complete block design (RCBD) with three replications was carried out in greenhouses, Faculty of Agriculture, University of Ilam, Iran. Factors examined in this study were salinity stress at 3 levels (0, 75 and 150 mM NaCl) and SA at 4 concentrations (0, 0.25, 0.5 and 1 mM). The results showed that SA significantly increased growth parameters of lettuce plants under salinity stress condition and reduced adverse effects of stress. With increased salinity severity, proline and malondialdehyde content and antioxidant activity increased but growth parameters decreased. In high concentrations of SA, all the measured parameters were increased while the malondialdehyde content was decreased. In general, SA application with an increase in proline content and antioxidant activity, and a decrease in peroxidation rate of cell membrane lipids led to decrease in adverse effects of salinity stress on lettuce plants.