Submitted to: Environmental Toxicology and Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2003
Publication Date: 2/9/2004
Citation: Michel, A., Johnson, R.D., Duke, S.O., Scheffler, B.E. Dose-response relationships between herbicides with different modes of action and growth of Lemna paucicostata: an improved ecotoxicological method. Environmental Toxicology and Chemistry. 2004. V. 23(4). P. 1074-1079. Interpretive Summary: Robust bioassays for phytotoxicity are needed by those involved in ecotoxicology, plant pathology, and herbicide discovery. A refinement of the commonly used duckweed bioassay for phytotoxicity is presented. This improved method allows for rapid and precise measurement of dose-response relationships of phytotoxins on duckweed growth. The approach presented here should provide a more reliable basis for comparison of results between different laboratories.
Technical Abstract: Lemna species are widely used in ecotoxicological research to assess the phytotoxicity of environmental compounds. The purpose of this paper was to further refine this bioassay. A non-destructive image analysis method was used to measure growth during a time course. Herbicides are a major class of phytotoxic compounds in the environment. We tested 26 herbicides, with as many as 19 different modes of action, on leaf area growth of Lemna paucicostata to establish complete dose-response relationships. By using 3,5 dichlorophenol as a reference compound, different EC50-values of the herbicides can be compared. EC50 values ranged from 0.003 µM for sulcotrione to 407 µM for asulam. Dose-response parameters were obtained which will allow transfer of these results to different laboratories with different experimental conditions. These results should give useful information to anybody who works with Lemna species to address questions on herbicide residues in environmental compartments, screening of new herbicidal compounds, or the assessment of phytotoxic side-effects of a given compound.