Effect of salinity on growth, ion accumulation and the roles of ions in osmotic adjustment of two populations of Suaeda salsa

The effect of salinity on growth, ion accumulation and the roles of ions in osmotic adjustment of two populations of Suaeda salsa were investigated. Seeds were collected from an intertidal zone or a saline inland zone in the Yellow River Delta in Shandong province, China. Seedlings were exposed to 10, 100, 200, 400 or 600 mM NaCl for 18 days in a greenhouse. NO3− concentration in the soil where S. salsa grows in an intertidal zone was much lower than that for the second population, but leaf NO3− concentration was the same in the two populations under field conditions. When plants were cultured in a greenhouse under natural light conditions, S. salsa from the intertidal zone showed fewer main stem branches and lower relative shoot growth compared to S. salsa from saline inland. Leaf Cl− concentration of saline inland S. salsa was significantly higher than that of S. salsa from the intertidal zone, while the opposite was true for the concentration of NO3− in leaves of plants. For S. salsa from the intertidal zone NO3− contributed more than Cl− to the osmotic potential, whereas S. salsa from the saline inland exhibited a reverse relationship under saline conditions, indicating that NO3− plays an important osmotic role in S. salsa from the intertidal zone in high salinity. In conclusion, S. salsa from the intertidal zone may employ superior control of ion uptake and content than S. salsa from the saline inland zone. The two populations of Suaeda salsa presented different ability in chloride exclusion and nitrate accumulation. These characteristics may affect the distributions of S. salsa in natural highly saline environments.