Abstract

Maryam Chavoushi Rizi*

Salinity is one of the most important factors limiting plant growth and development, especially in arid and semi arid regions. Chitosan is a biological elicitor and is a major component of cell wall in many fungal species. This study aimed to evaluate the effects of salinity and chitosan on some physiological and growth parameters of Portulaca oleracea L. This experiment was conducted as a factorial based completely randomized design with 3 replications. For this purpose, the plant was exposed to certain concentrations of NaCl (0, 25 and 35 ds m^-1 ) and chitosan (0, 0.2 and 0.4 g L^-1 ). Considering the plant species are salt tolerant, the results showed that the 25 ds m^-1 salinity improved the plant growth; while the higher level of 35 ds m^-1 reduced it. The chitosan treatment at the 25 ds m^-1 salinity significantly improved the photosynthetic pigments; while both concentrations of chitosan did not show any significant moderating effect on the plants under 35 ds m^-1 salinity. The application of 25 ds m^-1 salinity or 0.4 g L^-1 chitosan resulted in the highest contents of the K⁺ , Na⁺, and compatible solutes that can be associated to the activation of defense enzymes such as ascorbate peroxidase activity. The analysis of variance showed that the amount of fatty acids such as linoleic acid (omega-6) and uronic acids significantly increased with salinity to mitigate the abnormal growth conditions. Considering the growing salinity of the soil, it is crucial to apply the right elicitors for reducing the adverse effects of salinity stress on Portulaca oleracea L.