Effect of Phosphorus on Arsenic Accumulation and Detoxification in Arsenic Hyperaccumulator, Isatis cappadocica

Arsenic (As) and phosphorus (P) interactions are important for better understanding their uptake and accumulation by plants due to similar chemical behaviors. In this study, we investigated the interactions of arsenic and phosphorus on plant biomass and uptake of arsenic and phosphorus by Isatis cappadocica, a newly discovered arsenic hyperaccumulator. In a 28 day hydroponic experiment with varying concentrations of arsenate (0, 50, 200, 800, and 1,200 μmol l⁻¹) and phosphate (5, 50, 200, 800, and 1,600 μmol l⁻¹), I. cappadocica accumulated As in the shoots up to 700 mg As kg⁻¹dry weight, and the shoot As to root As concentration ratio varied between 0.6 and 1.5. At low and medium As levels (50 and 200 μmol l⁻¹), phosphate had slight effects on As uptake and growth of I. cappadocica. However, increasing P supply decreased As uptake markedly, with the effect being greater on root As concentration than on shoot As concentration at high arsenate levels (800 and 1,200 μmol l⁻¹). Increasing As supply decreased the P concentration in the roots and shoots, especially at high levels, because of its phytotoxicity. The root P concentrations of I. cappadocica were greater than those of shoots, which is in contrast to non-accumulator plants. Our findings suggest that P application may be an important strategy for efficient use of I. cappadocica to phytoremediate As-contaminated areas. Further studies are needed on the mechanisms of interactive effects of As and P on I. cappadocica in the soil system.