evaluation of some physiological characteristics and antioxidants activity in kochia (kochia scoparia) in different of salinity levels and growth stages

soil salinity threat for agricultural ecosystems in many parts of iran, and negatively affects crop production. in order to examine salinity tolerance of kochia a series of experiments were conducted in crd with four replications, seven levels of salinity (0, 10, 20, 30, 40, 50 and 60 ds.m-1), two growth stages (planting and early seedling) and interval irrigation. result showed that decrease of root dry weight, root volume, membrane stability index were more increased at planting than early seedling stages. relative water content was increased with increasing salinity levels in all experiments except at interval irrigation. proline and osmotic potential increased with increasing salinity levels. catalase, glutathione reductase, dpph - radical scavenging activities and total phenol were higher with more increased at planting than early seedling. sodium concentration and sodium to potassium ratio in shoot and root increased with increasing salinity levels. generally, despite application of high levels of salinity stress kochia was able to survive and tolerate these levels of salinity.