Chemical modification and degradation of atrazine in Medicago sativa through multiple pathways

The atrazine residue in ecological systems has resulted in a negative effect on environmental quality. Once alfalfa crops were contaminated by atrazine residues, the dairy and livestock production may be further affected.... [ view full abstract ]

The atrazine residue in ecological systems has resulted in a negative effect on environmental quality. Once alfalfa crops were contaminated by atrazine residues, the dairy and livestock production may be further affected. Thus, investigation on the accumulation and degradation of atrazine in alfalfa is of great importance from the environmental and agricultural points of view. The objectives of this study were (1) to assess the ability of alfalfa to accumulate and degrade atrazine and (2) to investigate the possible atrazine catabolic pathway.
Alfalfa seedlings were planted using hydroponics. To study the accumulation and translocation of atrazine in alfalfa, the concentration of atrazine in shoots and roots was analyzed by HPLC. Metabolites and conjugates of atrazine in alfalfa were analyzed using UPLC coupled to LTQ Orbitrap XL. The structures of metabolites were determined by analyzing fragmentation patterns from MS2 and MS3 data. The activities of glutathione S-transferase and glycosyltransferases were assayed spectrophotometrically.
The study demonstrated that alfalfa had a great ability to accumulate and translocate atrazine. Some atrazine absorbed in alfalfa was found as 10 chemically modified derivatives like deisopropylated atrazine, dehydrogenated atrazine, methylated atrazine, etc. Some derivatives were further conjugated with polar donor molecules such as glucose, homoglutathione and amino acids. The activated activities of glutathione S-transferase and glycosyltransferase supported the atrazine degradation models. These results suggest that atrazine in alfalfa can be degraded through different pathways. The biochemical responses and metabolism pathway will serve as useful indicators for assessment of the herbicide contamination in agricultural environments.