ENVR 46 |
| Pteris vittata, the first reported arsenic hyperaccumulator, can accumulate up to 2.3% of As in its fronds. To better understand the mechanisms of As hyperaccumulation and efficiently use P. vittata in phytoremediation, the uptake kinetics of arsenate [As(V)], arsenite [As(III)] and phosphate (Pi) in this plant were studied. As in normal plants, As(V) is transported via Pi uptake systems which consist of a high affinity uptake system and a low affinity uptake system in P. vittata. By comparison of As(V) and Pi uptake kinetic parameters, it was found that the protein carriers in both high and low Pi/As(V) uptake systems have similar affinity to Pi and As(V) in the plant. The Pi/As(V) uptake systems in P. vittata do not show substantial preference to Pi or As(V), which apparently differ from those in normal plants. The results suggest that rapid and efficient As accumulation in P. vittata could result from its unique Pi/As(V) uptake systems. An As(III) uptake system was found in P. vittata. This uptake system had a greater maximum uptake velocity (Vmax) and less affinity than the Pi/As(V) uptake systems, suggesting that P. vittata also takes up As(III) efficiently. When As concentrations were high (e.g., 0.5 mM), As(III) uptake was even faster than As(V) uptake. Interestingly, As(III) was found to be cotransported with Pi in P. vittata. To the best of our knowledge, the unique Pi/As(V) uptake systems and the cotransport of As(III) and Pi in P. vittata are reported for the first time in living organisms. These findings will be helpful in elucidating the mechanisms of As hyperaccumulation in the fern and will provide important information for the application of P. vittata in phytoremediation. |
|
Occurrence, Chemistry, Toxicity and Remediation of Arsenic
8:00 AM-11:20 AM, Monday, 27 March 2006 Georgia World Congress Center -- B218, Oral
Division of Environmental Chemistry |