EFFECTS OF ARSENIC SPECIES AND CONCENTRATIONS ON ARSENIC ACCUMULATION BY DIFFERENT FERN SPECIES IN A HYDROPONIC SYSTEM

Two hydroponic experiments were conducted to evaluate factors affecting plant arsenic (As) hyperaccumulation. In the first experiment, two As hyperaccumulators (Pteris vittata and P. cretica mayii) were exposed to 1 and 10 mg L−1 arsenite (AsIII) and monomethyl arsenic acid (MMA) for 4 wk. Total As concentrations in plants (fronds and roots) and solution were determined. In the second experiment, P. vittata and Nephrolepis exaltata (a non-As hyperaccumulator) were exposed to 5 mg L−1 arsenate (AsV) and 20 mg L−1 AsIII for 1 and 15 d. Total As and AsIII concentrations in plants were determined. Compared to P. cretica mayii, P. vittata was more efficient in arsenic accumulation (1075–1666 vs. 249–627 mg kg−1 As in the fronds) partially because it is more efficient in As translocation. As translocation factor (As concentration ratio in fronds to roots) was 3.0–5.6 for P. vittata compared to 0.1 to 4.8 for P. cretica. Compared to N. exaltata, P. vittata was significantly more efficient in arsenic accumulation (38–542 vs. 4.8–71 mg kg−1 As in the fronds) as well as As translocation (1.3–5.6 vs. 0.2–0.5). In addition, P. vittata was much more efficient in As reduction from AsV to AsIII (83–84 vs. 13–24 % AsIII in the fronds). Little As reduction occurred after 1-d exposure to AsV in both species indicates that As reduction was not instantaneous even in an As hyperaccumulator. Our data were consistent with the hypothesis that both As translocation and As reduction are important for plant As hyperaccumulation