Study of variability in growth, antioxidant defense system and protein content by zinc element application in periwinkle (Catharanthus roseus (L.) G. Don.) under salinity stress

Salinity stress is one of the major abiotic stresses that have destructive effects on plant productivity and quality. An experiment was conducted to investigate the effects of zinc as alleviating agent under salinity stress on antioxidative system, proteins, proline and growth of Catharanthus roseus (L.) G. Don. at Arak University in 2012 autumn. A number of 49-days-old plants were treated with different concentrations of NaCl (0, 35, 70 and 100mM) alone and in combination with various ZnSO4 concentrations (0, 5 and 10μm) for 21 days. Then, the inhibition percent of 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH), activity of antioxidant enzymes such as superoxide dismutase, catalase and guaiacol peroxidase, proline and protein content and growth parameters were measured. Results showed that zinc application improved shoot length, root depth, root and shoot fresh and dry weight under all salinity treatments. As a result of salinity stress, the inhibition percent of DPPH radical and superoxide dismutase, catalase, guaiacol peroxidase activity and also proline content increased 348.5%, 475.6%, 172.7%, 200% and 364%, respectively but protein content was reduced 33%. Zinc application improved protein content up to 16% in plants under salinity treatment and also reduced the proline content up to 36%. The activity of antioxidant enzymes increased significantly in treated plants with NaCl as compared with those treated with NaCl or Zn alone. These results support the positive effects of Zn application on antioxidant defense system in vinca under salinity. Zinc may act as a scavenger of reactive oxygen species for mitigating the injury on biomembranes under salt stress.