Metalaxyl toxicity, uptake, and distribution in several ornamental plant species

Phytoremediation depends on the ability of plants to tolerate and assimilat e contaminants, This research characterized the interaction between several ornamental plant species and the fungicidal active ingredient, metalaxyl [ N-(2,6-dimethylphenyl)-N-(methoxyacetyl)anine methyl ester]. Species evalua ted included sweetflag (Acorus gramineus Sol, ex Aiton), canna (Canna hybri da L. 'Yellow King Humbert'), parrotfeather [Myriophyllum aquaticum (Vell.) Verdc], and pickerelweed (Pontederia cordata L,), Metalaxyl tolerance leve ls for each species were determined by exposing plants for 7 d to solutions containing 0, 5, 10, 25, 50, 75, or 100 mg metalaxyl L-1 aqueous nutrient media. Response endpoints included fresh mass production after 7 d exposure and 7 d post-exposure and quantum efficiency using dark-adapted (Fv/Fm) an d light-adapted (fluorescence yields) plants. Metalaxyl uptake and distribu tion within the plant was determined by growing plants in aqueous nutrient media containing 1.18 x 10(6) Bq L-1 [C-14]metalaxyl (0.909 mg L-1) for 1, 3, 5, or 7 d. plant tissues were combusted and analyzed by liquid scintilla tion counting. Metalaxyl had no effects on the endpoints measured, except f or fresh mass production of sweetflag at the 75 and 100 mg L-1 treatment le vels. However, leaf necrosis was apparent in most species after 5 d exposur e to concentrations greater than 25 mg L-1. Metalaxyl removal from the spik ed nutrient media ranged from 15 to 60% during the 7 d exposure period. The majority of metalaxyl removed from the solution was detected within indivi dual plants. In nearly all cases, activity from the radiolabeled pesticide accumulated in the leaves. Uptake of metalaxyl was correlated with water up take throughout the 7 d, These results suggest that all species examined ma y be good candidates for incorporation into a phytoremediation scheme for m etalaxyl.