THE EFFECTS OF NITRIC OXIDE ON SOME ANTIOXIDANT ENZYME ACTIVITIES UNDER SALT STRESS IN SUNFLOWER PLANTS

The effects of externally applied sodium nitroprusside on superoxide dismutase (SOD), glutathione peroxidase (GPx), ascorbate peroxidase (APX), and catalase (CAT) antioxidant enzyme activities, nitric oxide (NO) levels have been investigated in salt stress resistant and sensitive sunflower plants. NaCl treatments and SNP treatments simultaneously with salt application (NaCl+SNP) were performed. SOD, GPx, APX and CAT antioxidant enzyme activities and NO levels showed differences in leaf tissues treated with 100 mu M SNP, different concentrations of NaCl, and NaCl+SNP. SOD, GPx and APX enzyme activities were generally increased in sensitive variety, but decreased in tolerant variety. However, while general increase in CAT enzyme activity was determined in tolerant type, a reduction was established in sensitive type. An increase was determined in both types in NO levels. It is evident from these results that administration of NO donor SNP can cope with reactive oxygen species in both varieties. This study indicates that negative effects of salt stress on different sun flower varieties can be recovered by nitric oxide.