Abstract: Tamarix species are dominant shrubs in the Yellow River Delta region, and they can adapt to saline environment well. Roots can directly sense soil salinity change. Therefore, studying the effects of differing salinity on the eco-physiological characteristics of roots of Tamarix species is important for the ecological restoration of coastal wetlands. In the present study, we studied the effects of different salinities (0, 0.4%, 0.8%, 1.2%, 2.4% and 3.6% NaCl solutions) on the growth and eco-physiological characteristics of roots of 1-yearold T. chinensis and T. austromongolica cuttings. We determined the rooting rate of Tamarix cuttings, root lifespan, root number, root length, root biomass, hydrogen peroxide enzyme (CAT) activity, adenosine triphosphate (ATP) synthase activity, and abscisic acid content. The cuttings of the two Tamarix species were suitable for cultivation at solutions with a salt content of lower than 0.8%. The rooting rate of the two species decreased significantly when salt content was more than 0.8%, and T. austromongolica cuttings did not produce roots when salt content was at 3.6%. The root growth of both Tamarix species was significantly inhibited when the salinity increased to more than 1.2%, especially for T. chinensis. Both Tamarix species could relieve the harm of salt to their roots by increasing the proportion of root biomass allocation under high salt conditions. The activities of ATP synthase and CAT of T. chinensis roots increased when the salinity was less than 0.8%, and the activities decreased when the salt content was more than 0.8%. The content of abscisic acid (ABA) of T. chinensis roots increased with the increasing salinity, and then decreased when the salinity was higher than 1.2%. The activities of ATP synthase and CAT and the content of ABA of T. austromongolica roots decreased gradually with the increasing salinity.

Key words: elevated CO₂ concentration, semi-arid area., spring wheat, production, water use efficiency