Abstract: Germination rate, cumulative germination rate and the final germination rate of Vallisneria natans （Lour.） Hara seeds under different substrate types and different flocs concentrations were studied. The results showed that the substrate type had a significant effect on the seed germination（P<0.05）. The final germination rate of V. natans seed with yellow mud as substrate was the highest （55.8%）, while the final germination rate of seed with sediment + sand was the lowest （33.0%）. The addition of flocs significantly reduced the final germination rate of seeds, and the final germination rate of the treatment with the largest inhibition effect （29.4%） was 19.8 percentage points lower than that of the treatment without flocs （49.2%）. In the ecological restoration of rivers and lakes, ferrate, as an common flocculant, could condense pollutants in the water body and remove them from the water body to achieve the purpose of water purification. However, the flocs produced by ferrate dosing covered the surface of V. natans seeds, which would affect their germination. Comprehensive analysis, yellow mud was more suitable for the seed germination than sediment and sand, and the use of flocculants might have adverse effects on the seed germination. In practical applications, the improvement effect of flocculants on water transparency and the negative effect on the seed germination of submerged plants should be considered comprehensively.

Key words: flocculant, substrate types, floc concentration, Vallisneria natans （Lour.） Hara, germination rate