Pesticides and their degradates may directly/indirectly reach water bodies via spray drift, erosion and run-off, and may undergo degradation processes with partitioning to suspended matters and bottom sediment. Therefore, it is important to evaluate their ecotoxicological risk for aquatic organisms. According to the previous EU Aquatic Guidance (2002, SANCO), standard ecotoxicological data on two algae and duckweed, a floating macrophyte, has been required for EU registration for herbicides and plant growth regulators. However, such data on floating/suspended species may not be suitable to assess the risk on submerged rooted macrophytes including water milfoil (Myriophyllum sp.), which are exposed to pesticides not only dissolved in water but also incorporated in bottom sediment. From this viewpoint, water milfoil is recommended as an additional assessment species in the latest guidance (2013, EFSA). Information on uptake/metabolism of pesticides is necessary to fully understand their risk on rooted macrophytes, but current data are limited, and especially, individual data on shoot and root uptakes is scarcely available. Therefore, by using Myriophyllum elatinoides, we have conducted a metabolism study of 14C labeled 3-phenoxybenzoic acid (I ), which is one of the major degradates of synthetic pyrethroids in the environment, as a model substance. In this study, our original test chamber was adopted which enabled to quantify each shoot and root uptake followed by translocation/metabolism. Shoot uptake of 14C-I  dissolved in water was rapid and reached equilibrium within one day. The incorporated 14C amounted to 18.0% of the applied radioactivity (AR), while translocation from shoot to roots was insignificant. Slower and minor root uptake was observed when 14C-I  was treated to sediment (8.1%AR after 14 days) and one-fifth of 14C accumulated in roots was translocated to shoot. As metabolic reactions, oxidation, reduction and sugar conjugation of I  proceeded in M. elatinoides, similarly to terrestrial plants.

Uptake, translocation, and metabolism of 3-phenoxybenzoic acid by <i>Myriophyllum elatinoides</i>

248th National Meeting (2014)

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Uptake, translocation, and metabolism of 3-phenoxybenzoic acid by Myriophyllum elatinoides