Soil salinity is a major constraint to food production due to its negative impact on crop yield. Kochia (Kochia scoparia) is a hardy, salinity-resistant plant that can widely use as emergency forage for livestock to using saline waters and soils in desert ecosystems. In order to investigate physiological mechanism, antioxidants activity and potential of production of Kochia in response to different levels of salinity, an experiment was performed in a split plot based on randomized complete block design with three replications. Saline waters (5.2, 10.5 and 23.1 dS m-1) and three Kochia ecotypes (Birjand, Borujerd and Sabzevar) were allocated as main and sub plots, respectively. The results showed that salinity did not impose any significant effect on dry matter production but relative water content (RWC) and seed yield decreased by salinity stress. In general, no positive correlation coefficient observed between dry matter production and physiological and biochemical parameters except superoxide dismutase (SOD) at 23.1 dS m-1. There was no significant difference among ecotypes in dry matter and seed yield. Sabzevar showed the highest proline, total phenol content and peroxidase (POX) activity. Ascorbate peroxidase (APX), catalase (CTA), and superoxide dismutase (SOD) activity was higher in Borujerd ecotype and highest soluble sugar, glutathione reductase (GR) activity and DPPH - radical scavenging activity observed in Birjand ecotype. According to these results, Kochia has a good tolerance to elevated levels of salinities up to 23 dS m-1 and seems that can control oxidative stress by continuing growth.

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