Antioxidant properties of two alfalfa (Medicago sativa L.) ecotypes in response to sodium chloride salinity stress

Biochemical and physiological responses of alfalfa under salinity stress were comparatively studied in a factorial experiment based on randomized complete block design by using Yazdi as the tolerant and Diabolourde as the sensitive ecotypes. Salt levels of 100, 150 and 200 mM were prepared by adding sodium chloride to the Hoagland half-strength culture medium. Total phenolics content, polyphenol oxidase (PPO), β-glucosidase and antiradical activities of leave′s extract, stomata properties and chlorophyll fluorescence parameters of the leaves including Fv/Fm and Fv/Fo were measured in response to salinity stress. Stomata characters were reduced in both ecotypes but chlorophyll fluorescence parameters only declined in Diabolourde but not in the Yazdi ecotype.  The PPO and β-glucosidase activities increased in both ecotypes. The phenolics content and antiradical activities increased in the Yazdi ecotype at all salt levels but those of Diabolurde increased only at the higher salinity levels. Our observations indicated that the Yazdi ecotype manipulated biochemical and physiological responses more efficiently to alleviate the reduction of growth parameters under salinity.