Abstract: A pot experiment was conducted to study the effects of different NaCl concentrations (0, 50, 100, 200 mmol·L^-1 and 400 mmol·L^-1) on the growth, leaf hydrogen peroxide (H₂O₂), malonaldehyde (MDA) content, superoxide dismutases (SOD), catalases (CAT), peroxidase (POD), ascorbate peroxidase (APX) enzymes activity, water potential, soluble sugar and proline contents of Populus euphratica. The results showed that plant heights were significantly inhibited under 200 mmol·L^-1 NaCl treatment compared with control; Basal stem diameter were significantly inhibited under 400 mmol·L^-1 NaCl treatment compared with control; Crown area, leaf dry mass and branch dry mass decreased remarkably under NaCl concentration ≥100 mmol·L^-1 compared with control level; Root dry mass decreased with the increasing in NaCl concentrations. Root shoot ratio decreased markedly under NaCl concentration ≥200 mmol·L^-1 compared with control. H₂O₂ and MDA content increased with the increasing in NaCl concentrations. SOD, POD, CAT and APX activities in leaves of P. euphratica increased compared with control lever at low NaCl concentrations (50 mmol·L^-1), whereas SOD, POD and APX activities began to descend under NaCl concentration ≥100 mmol·L^-1 compared with control level. Water potential in leaves of P. euphratica reduced with the increasing in NaCl concentrations. Being treated for 90 d, soluble sugar decreased with the increasing in NaCl concentrations. Proline content in leaves of P. euphratica first increased and then decreased compare with control level.

Key words: Populus euphratica, salinity stress, MDA content, antioxidative enzyme system, osmotic regulation