Effects of temperature and salinity on Ruppia sinensis seed germination, seedling establishment, and seedling growth

As typical submerged aquatic vegetation, Ruppia species are facing population reductions due to anthropogenic impacts. In this study, we investigated the effects of temperature and salinity on seed germination and seedling establishment of Ruppia sinensis seeds collected from northern China. The effects of seven salinities (0-50) and six water temperatures (0-30 °C) on seed germination were investigated to identify the environmental conditions that could potentially limit survival and growth. We found that: 1) optimum seed germination was salinity 5 at 30 °C; 2) high salinity (salinity 40-50) and low temperature (0 °C) significantly inhibited seed germination; 3) seed germination with increasing temperature showed a bimodal pattern at suitable salinities (5-10); 4) storing seeds at high salinities (40-50) or low temperature (0 °C) promoted germination after transferal to optimal germination conditions. These findings may serve as useful information for R. sinensis habitat establishment and restoration programs.