Phytotoxicity, uptake, and distribution of14C-simazine inAcorus grameniusandPontederia cordata

Abstract

Phytoremediation depends on the ability of plants to tolerate and assimilate contaminants. We have been interested in the use of common ornamental plants to ameliorate the effects of pesticide waste on golf courses and ornamental plant nurseries. This research characterized the interaction between two ornamentals, Acorus gramenius and Pontederia cordata, and the herbicide simazine. Simazine tolerance levels for the ornamentals were determined by exposing plants to 0, 0.01, 0.03, 0.1, 0.3, 1.0, or 3.0 mg L−1 in aqueous nutrient media for 7 d. Response endpoints included fresh weight gains for both species after 7 d exposure and 7 d postexposure. Quantum efficiency of P. cordata was also measured using dark-adapted (Fv/Fm) and light-adapted (fluorescence yields) plants. Simazine uptake and distribution within each plant was determined by exposing plants to [14C]-simazine in nutrient media (0.24 mg L−1) for 1, 3, 5, or 7 d. Plant tissues were combusted and analyzed by liquid scintillation counting. Pontederia cordata fresh weight gains were reduced 76 and 70% by 1.0 and 3.0 mg L−1, respectively, after 7 d exposure. Acorus gramenius fresh weight gains were reduced 103, 124, and 144% at 0.3, 1.0, and 3.0 mg L−1 following 7 d exposure, respectively. Photosynthetic efficiency measured on dark-adapted P. cordata (Fv/Fm) was reduced 21, 47, and 71% by 0.3, 1.0, and 3.0 mg L−1, respectively, whereas photosynthetic efficiency measured on light-adapted plants (fluorescence yields) were reduced 9, 25, 59, 87, and 96%, respectively, by 0.03, 0.1, 0.3, 1, and 3 mg L−1. Simazine activity in solution was reduced 45 and 34% over 7 d with A. gramenius and P. cordata, respectively. By day 7, activity was distributed throughout the plants, but predominantly in the leaves. Uptake of simazine was correlated with water uptake throughout the 7 d. These results suggest that A. gramenius and P. cordata may be good candidates for incorporation in a phytoremediation scheme for simazine.