effects of foliar application of ordinary and nano-particles of zinc oxide on the antioxidant enzyme activity and proline content of two zea mays l. cultivars under salt stress

this experiment was conducted in order to evaluate the effects of foliar application of ordinary and nano-particles of zinc oxide on the response of corn to salinity. treatments included two corn genotypes (seed mass and sc 704), three spray levels (zinc oxide, nano-sized zinc oxide, and a spray of water treatment) and three salinity levels (0, 75 and 150 mm nacl). shoot dry matter was decreased as the level of salinity was increased and the reduction was greater in seed mass than in sc 704. however, the enzyme activity of superoxide dismutase (sod), catalase (cat) and ascorbat peroxidase (apx), and also the concentration of mda and proline in leaves were increased under saline conditions. the extent of increases in proline content and the antioxidant enzyme activities was larger in seed mass than in sc 704. foliar application of zinc oxide had significant positive effects on shoot dry matter and on the activity of sod in leaves. regardless of cultivars, the extent of increase in the activity of apx under saline condition was smaller when plants were sprayed with nano-sized zinc oxide compared to the ordinary bulk form. the results from this experiment showed that there were positive correlations between the increase in proline content and the enhanced antioxidant enzyme under saline condition and the salt tolerance of the more salt tolerant cultivar. although, there were no significant differences between the two tested cultivars in response to zinc oxide foliar application, positive effects of nano-sized was more than ordinary form.