Abstract: The objective of this research was to better understand the mechanism of osmoregulation and antioxidant response of Halostachys caspica seedlings growing under salt stress.The effects of NaCl-salinity treatments (0,100,300 and 500 mmol·L^-1 NaCl for 15 days) on water content,lipid peroxidation (MDA),organic (proline and glycine betaine) and inorganic osmolytes (Na⁺,K⁺ and Ca²⁺),and antioxidant defenses (SOD,CAT,APX,POD,AsA and GSH)in seedlings and grown-up seedlings of H.caspica were investigated.The research on the development and utilization of H.caspica and the improvement of ecological environment in Xinjiang was carried out.Water content in the seedlings and grown-up seedlings of H.caspica growing under high-salt (500 mmol·L^-1 NaCl) stress was significantly decreased compared with those under control.The data of water content and MDA content revealed that asalt stress on H.caspica plants was not induced under the conditions of 100 mmol·L^-1and 300 mmol·L^-1 NaCl.Na⁺ and GB played the dominant roles in osmoregulation of seedlings and grown-up seedlings.With increasing salt concentration,the activities of SOD and CAT as well as the content of GSH were maintained at a high level all along except AsA content of grown-up seedlings under 500 mmol·L^-1 NaCl treatment was increased.The correlation coefficient analysis showed that AsA and SOD played an important role in antioxygenation of seedlings and grown-up seedlings of H.caspica.It could be seen that the osmotic adjustments and antioxidant strategies were different at different growth stages of H.caspica seedlings so as to adapt salt stress.

Key words: Halostachys caspica, NaCl treatment, osmolytes, antioxidants system, mechanism of salt tolerance