Effects of salinity on sprouting and growth of three submerged macrophytes

Many freshwater ecosystems are facing salinity stress, but limited information is available about its effects on submerged macrophytes. Here, we assessed the effects of salinity on sprouting and growth of three submerged macrophytes-Potamogeton crispus,Hydrilla verticillataandMyriophyllum spicatum. We conducted experiments in the lab and the outdoor platform to test for the sprouting and growth responses of selected macrophytes to a gradient of salinity (0.32-10,000 mg Cl-L-1). Sprouting rate, biomass and other related physiological indices were measured in all treatments. We found that lower salinity (100 mg Cl-L-1) increased the turion sprouting rate, and higher salinity (greater than or equal to 5,000 mg Cl-L-1) significantly inhibited the sprouting ofP. crispusturions.M. spicatumappeared to have higher tolerance of salinity thanH. verticillata. The optimum salinity for the growth ofH. verticillataandM. spicatumwas 500-1,000 mg Cl(-)L(-1)and 100-500 mg Cl-L-1, respectively. Activity of superoxide dismutase (SOD) and production of malondialdehyde (MDA) differed in salinity levels between submerged macrophytes, and higher SOD activity was observed inM. spicatum. This study helped clarify how physiological response mechanisms affecting sprouting and growth of submerged macrophytes are inhibited under high salinity and suggested that SOD plays an important role in the resistance to oxidative stress induced by salinity