Lead sequestration in iron plaques developed on Phalaris arundinacea Linn. and Carex cinerascens Kukenth. from Poyang Lake (China)

• The root surfaces of C. cinerascens and P. arundinacea precipitate on iron plaque.
• The iron plaque of the two species increases sequestration of Pb on the root surfaces.
• The iron plaque of the two species reduces the translocation of Pb from root to shoot.
• 50–60% of Pb accumulated in iron plaque, and 90% of Pb accumulated in whole roots.

Iron plaque often forms on the roots of wetland plants under anaerobic conditions, and it may play a role in the uptake and translocation of metals in wetland plants. A hydroponic experiment was conducted to investigate whether iron plaque could affect the uptake and translocation of lead by two dominant wetland plants, Carex cinerascens Kukenth. and Phalaris arundinacea Linn., growing in Poyang Lake, Jiangxi Province, China. After iron plaque on plant roots was induced by growing plants in solution containing 0, 30, 60, 100, 150, or 210 mg L−1 Fe2+ for 7 days, plants were transferred to nutrient solution containing 10 mg L−1 Pb2+ for 5 days. A significant positive correlation was observed between the content of iron plaque and Fe2+ concentration in the solution for both the species. The content of iron plaque formed on the root surfaces of C. cinerascens with higher root activity was slightly more than that of P. arundinacea with lower root activity. Iron plaque on the root surfaces of the two species could adsorb or co-precipitate with Pb and could immobilize Pb on the root surfaces. The Pb concentrations and percentage distribution in different organs were in the order iron plaque > root > shoot. The findings that the proportions of Pb in DCB extracts and roots (nearly 90% in the present study) were significantly higher than that in shoots had been observed. The results showed that iron plaque on the root surfaces could increase sequestration of Pb in the root and reduce the translocation Pb from root to shoot under hydroponic conditions.