In this study the effect of responses of Catharanthus roseus to NaCl stress has been explored. Periwinkle plants were exposed to different concentrations of salt and the effect of treatment on germination, growth parameter and antioxidative defense system investigated. Seeds were presoaked in solutions with different salinity after sterilization. Experimental samples irrigated once every two days with solutions containing given NACl concentration. Increasing the NaCl concentration to 25, 50, 75 and 100 μM salt reduced germination percentage by 8, 29, 41 and 81 percent respectively. Plant fresh and dry weights of treated plants showed a decrease, compare to the control. Ascorbic acid content increased to 42, 56, 129 and 218 percent when treated by 25, 50, 75 and 100 μM salt, respectively, compared to the control. Glutathione concentration showed a significant (P<0.05) increase at all treatments. NaCl caused to significant decrease of SOD activity. Salinity enhanced the activities of catalase, peroxidase and glutathione reductase. The MDA content increased with the increasing concentrations of NaCl. MDA content of samples treated by 100 μM NaCl increased up to 45 percent more than the control.
