the study of physiological characteristics and enzyme superoxide dismutas activity in two wheat (triticum aestivum l.) cultivars at different growth stages under irrigation water salinity

in order to study the effect of salt stress at different growth stages on physiological characteristics and enzyme superoxide dismutas (sod) activity in wheat genotypes a green house experiment was conducted at the agricultural research greenhouse, agricultural, medical and industrial research school, nuclear science and technology research institute of karaj. a split factorial design on the basis of randomized complete design with three replications was applied. growth stage (tillering, anthesis and 10 days after anthesis) served as main plots and a combination of five salinity treatments (0, 6, 8, 10 and 12 ds/m) and two wheat cultivars, bam (resistance) and tajan (susceptible to salt stress) served as subplots. salt stress at different growth stages resulted in a decrease in relative water content. althougth salinity increased mda, chlorophyll and protein content in all cultivars. the antioxidant enzyme superoxide dismutas (sod) activity also increased under salt stress. bam cultivar, which had higher sod activity, had the lower mda and chlorophyll content and rwc and higher protein content than tajan cultivar under salt stress. in this experiment, chlorophyll content and rwc of tajan cultivar were higher than bam cultivar, but increase in these parameters did not cause to higher sod activity in tajan cultivar. it seems that the degree of oxidative stress tolerance associated with increasing in activities of antioxdant enzymes. salinity susceptible genotype uses the avoidance mechanism such as higher rwc and chlorophyll content to stand salt stress. so the evaluation of some physiological and biochemical characteristics at the most important growth stages of wheat may be useful for screening the salinity tolerance genotypes.