Effects of salinity and sulphide on seed germination of three coastal plants

The sensitivity of coastal plants to salinity and sulphide influences their performances in salt marshes. The combined effects of salinity and sulphide on the germination characteristics of three coastal plant species (Suaeda salsa, Phragmites australis and Spartina alterniflora) were studied under controlled conditions in the laboratory. Treatments included three salinity levels (0, 250 and 500 mM) and five sulphide levels (0, 3, 6, 9 and 12 mM) using a complete randomized block design. The germination percentage, germination speed and shoot length of all plants decreased in response to increasing salinity. S. salsa and S. alterniflora in the high salinity treatments showed significantly higher recovery percentages in comparison to low salinity treatments. Germination speed of S. salsa and P. australis increased with elevated sulphide level in freshwater, reaching maximum values in the 6 and 9 mM sulphide treatments, respectively. Sulphide did not increase shoot length of S. salsa and P. australis, but stimulated S. alterniflora to elongate rapidly under freshwater and low salinity conditions. These results showed that these three coastal plant species have different germination strategies. For S. salsa and P. australis, sulphide increased the number of germinated seeds or accelerated the speed of germination under freshwater and low salinity conditions, which benefits for their establishments by increasing the number of seedlings. Nevertheless, S. alterniflora would enhance shoot elongation to increase its competitive advantages under moderate sulphide conditions.