Metal-Dependent Root Iron Plaque Effects on Distribution and Translocation of Chromium and Nickel in Yellow Flag (Iris pseudacorus L.).

Iris pseudacorus L. (yellow flag) is a wide-use wetland plant for constructed wetlands for removing metals from wastewater. This study aims to understand effects of root iron plaque on sequestration and translocation of Cr and Ni in yellow flag seedlings using a hydroponic experiment. Yellow flag seedlings (4-week-old seedlings with 4-6 leaves) with or without iron plaque induction (at 50 mg Fe2+ L(-1) for 72 hours) were spiked for 6 days in the Hoagland solution with Cr or Ni at 0.5, 5, and 50 mg L(-1), equivalent to 1, 10, 100 times of thresholds of surface water quality, respectively. Results indicated that root iron plaque significantly reduced translocation of Cr and Ni to root but increased from root to shoot. Root iron plaque formation counteracted Cr toxicity to yellow flag seedlings while the control showed Cr toxicity to root at 5 mg L(-1)and to shoot at 50 mg L(-1) with significant biomass loss. Neither Ni exposures caused significant biomass loss nor root iron plaque formation significantly changed Ni distribution among plant parts. Our study suggests that root iron plaque effects on metal sequestration and translocation in yellow flag seedlings were metal-dependent.