Physiological and Growth Responses of Halophyte Zoysia macrostachya to Increasing Salinity

The current research aimed to evaluate the effects of various concentrations of NaCl (0.0, 1.0, 2.0 and 4.0%) on the physiological and growth behaviors of the halophyte Zoysia macrostachya collected from the coastal wetland in east China from 2017 to 2018. The relative water content, antioxidase activities and osmotic adjustment substances contents in leaf were determined on days 4, 8, 12, 16, 20 and 24 of the experiment. Besides, Na+ and K+ concentrations in the root, shoot and leaf, together with the biomass, were measured at the end of experiment. Our results showed that relative water content decreased, while the H2O2 content elevated; in addition, the activities of peroxidase, catalase and superoxide dismutase were higher under salinity stress. On the other hand, the contents of proline, soluble sugar and betaine were increased with the increase in the salinity concentrations. As the NaCl concentrations increased, the Na+ concentrations in root, shoot and leaf increased significantly (P <= 0.05), K+ concentrations increased at first and then decreased, while K+/Na+ ratios were gradually decreased. Typically, the salinity levels of 1.0 and 2.0% improved root and aboveground growth, but that of 4.0% limited plant growth. These results indicated that the increase in antioxidase activities, the accumulation of osmotic adjustment substances, the absorption of a higher level of K+, the maintenance of greater K+ contents in leaf and shoot, and the lower Na+ transfer from root to shoot and leaf, might account for the mechanisms of salinity tolerance in Z. macrostachya. (C) 2020 Friends Science Publishers