Does sulfate improve the Mn bioremediation efficiency of Polygonum lapathifolium Linn?

Abstract

Polygonum lapathifolium Linn., as a hyperaccumulator, has a strong ability to bioaccumulate manganese (Mn). Sulfur (S) is an important micronutrient in plants and plays an important role in heavy metal detoxification and plant physiochemistry processes. In the present study, P. lapathifolium plants and two soils, one from a Mn mining area (Mn mine soil) and the other from a non-Mn mining area (farmland soil), were used to explore whether S has positive effects on plant growth and the efficiency of Mn bioremediation. The results showed that (1) although the biomass was similar between the two soils, the number of lateral branches in Mn mine soil was significantly greater than that in farmland soil, and S had a positive effect on root growth compared to a lack of S supplementation in each soil. (2) Sulfate promoted Mn uptake and transport from soil to plant in Mn mine soil but had no such effects in farmland soils. (3) Compared to those in farmland soil, the physiochemical parameters, including gas exchange characteristics, and chlorophyll pigments increased in Mn mine soil, and S promoted these effects. Although reactive oxygen species increased in Mn mine soil, the lower malondialdehyde content observed with S supplementation indicated its alleviatory role in the Mn-polluted environment. Antioxidant enzyme and nonantioxidant enzyme materials (total protein, total sugar and free proline) also showed the same positive effects. In conclusion, S improved the Mn enrichment efficiency of P. lapathifolium by promoting its root division in Mn mine soil, while the role of S in the physiochemical processes of P. lapathifolium was stronger in Mn mine soil than in farmland soil.