Uptake and phytotransformation of organophosphorus pesticides by axenically cultivated aquatic plants

The uptake and phytotransformation of organophosphorus (OP) pesticides (malathion, demeton-S-methyl, and crufomate) was investigated in vitro using the axenically aquatic cultivated plants parrot feather (Myriophyllum aquaticum), duckweed (Spirodela oligorrhiza L.), and elodea (Elodea canadensis). The decay profile of these OP pesticides from the aqueous medium adhered to first-order kinetics. However, extent of decay and rate constants depended on both the physicochemical properties of the OP compounds and the nature of the plant species. Malathion and demeton-S-methyl exhibited similar transformation patterns in all three plants: 29-48 and 83-95% phytotransformation, respectively, when calculated by mass recovery balance during an 8-day incubation. No significant disappearance and phytotransformation of crufomate occurred in elodea over 14 days, whereas 17-24% degraded in the other plants over the same incubation period. Using enzyme extracts derived from duckweed, 15-25% of the three pesticides were transformed within 24 h of incubation, which provided evidence for the degradation of the OP compounds by an organophosphorus hydrolase (EC 3.1.8.1) or multiple enzyme systems. The results of this study showed that selected aquatic plants have the potential to accumulate and to metabolize OP compounds; it also provided knowledge for potential use in phytoremediation processes.