Abstract

This investigation was conducted to determine NaCl salinity effects on antioxidant enzymes activities, reducing sugar contents and lipid peroxidation in two alfalfa cultivars. Plants grown in solution cultures were subjected to 0, 100, 150 and 200 mM solutions of sodium chloride. Yazdi and Diabolourde alfalfa were used as tolerant and sensitive cultivars, respectively, in a germination experiment under similar conditions. Results show that the amount of reducing sugars and the activities of peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) enzymes increased with the increase in salt concentration. However, SOD activities decreased at high salt concentrations. The increase in the activities of antioxidant enzymes in response to salt treatments was higher in the tolerant cultivar. The results also show that salt treatment provoked an oxidative stress in both cultivars, as shown by the increase in lipid peroxidation. However, the level of lipid peroxidation was higher in the sensitive cultivar. The increase in antioxidant activities could also be a response to the cellular damage induced by NaCl. It seems that the tolerant cultivar has a better mechanism to cope with the deleterious effects ROS produced under salt stress.

Key words: Alfalfa, antioxidant enzymes, malondialdehyde, salt stress.

Abbreviation

PUFA, Poly unsaturated fatty acids; ROS, reactive oxygen species;SOD, superoxide dismutase; CAT, catalase; APX, ascorbate peroxidase; DHAR, dehydroascorbate reductase; MDHAR, monodehydro ascorbate reductase; GR, glutathione reductase; PPFD, photo period flow density; TBA, thio barbituric acid;EDTA, ethylene diamino tetra acetic acid; TCA, tri chloro acetic acid.