Abstract: Alternanthera philoxeroides was treated with NaCl of different concentrations (0, 50, 100, 150, 200, 250, 300 and 350 mmol/L). The results showed: (1) Under NaCl treatment, the fresh weight, the dry weight and the root shoot ratio decreased. (2) Water content and the succulency degree of whole plant appeared to increase first and then gradually decline as salinity increased. (3) Na⁺ contents increased and K⁺ contents decreased in root, stem and leaf. Na⁺ and K⁺ contents in leaf were the highest under the same salinity, those in stem were next and those in root were the lowest. (4) FAA content gradually decreased. (5) Pro content appeared to decline first and then increase as salinity increased. (6) Soluble sugar changed in the opposite direction. (7) Pn , Gs and T_r decreased and Ci increased . The relative conductivity of leaves increased significantly. ( 8) The malondialdehyde (MDA) content declined at about NaCl 50mmol/L but increased under at about NaCl 100 - 350 mmol/L. Those parameters indicated that A. philoxeroides was halophyte, but its salt tolerance was not strong and its NaCl optimal concentration lowed 100 mmol/L. Na⁺ mainly accumulated in stem and leaf of A. philoxeroide and it would probably spread to the salt soil .

Key words: Alternanthera philoxeroides