Aims Suaeda salsa can grow in the intertidal zone or on saline inland soil. The intertidal population is mainly affected by high salt concentration, hypoxia and low temperature, while the inland population is mainly affected by salt and drought. We hypothesized that S. salsa from the intertidal zone would have a greater ability to regulate salt accumulation or translocation compared with S. salsa in saline inland habitats. Therefore, our objective was to investigate the effects of salinity on growth, photosynthetic oxygen evolution and ion accumulation of two populations of S. salsa, i.e., to determine how two populations of S. salsa adapt to their different habitats.

Methods After pre-culture for 40 days, seedlings of both populations were treated with 1, 200 and 600 mmol·L^-1 NaCl. The experiment was terminated 20 days after final NaCl concentrations were reached. Then we determined the organic dry weight of shoots and roots, content of chlorophyll and the rate of photosynthetic oxygen evolution in leaves and contents of Na⁺ and Cl^- in leaves and roots of seedlings of the two S. salsa populations.

Important findings The organic dry weight of shoots and roots of both populations was not affected by 200 mmol·L^-1 NaCl, indicating that both populations had high salt resistance. Under all treatments, the rate of photosynthetic oxygen evolution was higher in leaves of S. salsa from saline inland than that in the intertidal population, while the opposite trend was true in the chlorophyll a/b ratio. The Cl^-content in leaves of S. salsa from the intertidal zone was lower than that in the saline inland habitats, while the opposite trend was true in the Cl^- content in roots, which suggests that S. salsa from the intertidal zone may employ superior control of ion accumulation (especially for Cl^-) in roots or ion translocation from roots to shoots compared with S. salsa from saline inland. These traits may affect the distribution of S. salsa in natural saline environments.