Effect of exogenous nitric oxide on germination and some of biochemical characteristics of purple coneflower (Echinacea purpurea L.) in saline condition

To find out the role and effects of exogenous nitric oxide (NO) application in reducing oxidative damage induced by salinity stress in purple coneflower (Echinacea purpurea L.) seed germination, a compeletly randomized design in factorial arrangment with three replications was conducted in Plant Physiology Laboratory of the Genetics and Agricultural Biotechnology Institute of Tabarestan, Sari Agricultural Sciences and Natural Resources University in 2012. The crop seeds were pre-soaked in 0.1 mM of sodium nitroprusside (SNP 0.1 as nitric oxide donor) solution as well as in distilled water (SNP 0 as control) for 20 hs just before the onset of the experiment. Then, pre-treated seeds were subjected to different levels of salinity (0, 50, 75, 100, 125, 150 mM NaCl solution) to germinate. Results showed that the SNP0.1 treatment in saline conditions had significant effect on germination percentage. Different levels of salinity significantly reduced germination rate, germination vigor and index. Pretreated with exogenous NO increased the activity of SOD, POD and APX as compared with SNP0. Accordingly, the highest activity of SOD (116.3 μM g-1 FW), POD (1.7 μM g-1 FW. min.) and APX (50.1 μM g-1 FW. min.) was related to the 125, 50 and 125 Mm NaCl, respectively. Significant and adverse effects of NO were seen on CAT activity. Exogenous NO, as an antioxidant, also reduced peroxidation of membrane lipids (MDA) and delayed the oxidation of proteins. Overall, it could be concluded that sodium nitroprusside as NO donor could improve coneflower seed germination characteristics in saline condition and increase salinity tolerance by means of scavenging of free ROS radicals