Soil salt and NaCl have different effects on seed germination of the halophyte Suaeda salsa

Seed germination is a key life-history stage of halophytes. Most studies on seed germination of halophytes have focused on the effects of a single salt, while little information is available on the effects of mixed salt in the natural habitat. Due to the contribution of multiple ions in saline soil, we hypothesized that the effect of mixed salt on seed germination will differ from that of a single salt and the mechanism of how germination is affected will differ as well. The effects of mixed salt and NaCl on germination, water imbibition, and ionic concentrations of seeds of Suaeda salsa (L.) Pall. were compared at various salinity levels. Germination percentage (GP) and rate (GR) decreased with increasing salinity level, regardless of salt type. There was no difference in GP or GR between mixed salt and NaCl when the salinity level was below 20 dS m(-1). Above 20dS m(-1), GP and GR in NaCl were lower than those in mixed salt. At the same salinity level, Na+ concentration in seeds was higher in NaCl than that in mixed salt, but the reverse was true for Ca2+ and Mg2+ concentrations. Imbibition rate for seeds in NaCl was lower than that in mixed salt at the same salinity level. Addition of Ca2+ and Mg2+ alleviated the inhibition of NaCl on seed germination. In conclusion, our results suggest that the effects of soil salts and NaCl on seed germination are different, and using NaCl instead of soil salt might not be realistic to show the effect of saline stress on seed germination of halophytes in the natural habitat.