Abstract
Wheat cultivars, Sakha 93, somaclone S-1, S-2 and S-3 were previously screened under different salinity concentrations. The preliminary screening on the basis of seedlings survival showed that soma clones S-2 and S-1 were tolerant to salt stress. In the present study, photosynthetic CO2 fixation, stomatal conductance (gs) and transpiration rate were decreased substantially due to salt stress, and showed high degree of reduction in the sensitive cultivar Sakha 93 and soma clone S-3. The tolerant lines S-2 and S-1 had more responsive stomatal conductance that tended to close faster under stress. However, in the sensitive lines, gs was sharply decreased. Furthermore, salinity stimulated the activity of the antioxidative defense systems (i.e. superoxide dismutase (SOD), catalase (CAT), ascorbate peroxydase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR)).The activites of these systems were studied in the shoot and root of the plants treated with different concentrations of NaCl (0, 50, 100, and 150 mM). The activities of all antioxidant enzymes measured in this study were increased as salt concentrations increased in both shoot and root of soma clone S-2 and S-1, indicating that the scavenging of ROS by the antioxidant defense system and the decrease in the level of H2O2 was done well. Also, the damage of membranes as represented by MDA was controlled. On the other hands, the activities of these antioxidant enzymes in shoot and root of the other tested varieties (Sakha 93 and S-3) were less affected by the imposed treatments. All these reasons led to the sensitivity of Sakha 93 and S-3 to salt stress.

Key words: Photosynthesis, stomotal conductance, antioxidant enzymes, wheat soma clones, salt stress.