Napropamide Accumulation And Its Effect On Growth Of Medicago Sativa L. Seedlings

Napropamide belongs to the amide herbicide family and widely used to control weeds in farmland. Intensive use of the herbicide has resulted in the widespread contamination to ecosystems. The current physiochemical method to evaluate the ultimately real bioavailability of the herbicide in soils has its inherent drawbacks. In this study, a comprehensive analysis was performed to assess the accumulation of napropamide, along with biological parameters and its residues in soils. We determined the accumulation of napropamide in six genotypes of alfalfa (Medicago sativa cv. Golden Empress, Zhong Mu1, WL232, WL323, Gannong3and Longdong), a plant species tolerant to adverse environmental stresses.The results showed that the accumulation abilities to napropamide varies in different parts and different varieties of Medicago sativa L. Soil was treated with napropamide at3mg kg-1dry soil and alfalfa plants were cultured for10or30d, respectively. The results showed that all the alfalfa species can absorb and accumulate napropamide. The maximum value for napropamide accumulation is0.426mg kg-1in shoots and2.444mg kg-1in roots. The concentration of napropamide accumulated in roots was more than that in shoots. The napropamide-contaminated soil with alfalfa cultivation had much lower napropamide concentrations than the control (soil without alfalfa cultivation). The reduction of napropamide in all the six treatments with plants was by58.83-78.84%and the decrease in the soil without plants was only by40.53%, indicating that the presence of plants could enhance napropamide reduction. Also, the content of napropamide residue in the rhizosphere was significantly lower than that in the non-rhizosphere soil, suggested that it may have relationship with the root exudates and microbial community.To investigate the effect of napropamide accumulation on biological parameters, several physiological responses were determined. M. sativa exposed to3mg kg-1napropamide for10d showed inhibited growth. Further analysis revealed that plants treated with napropamide accumulated more reactive oxygen species (O2-and H2O2) and less amounts of chlorophyll. However, not all cultivars showed oxidative injury, suggesting that the alfalfa cultivars have different capability for tolerance to napropamide.