AbstractCucumber and lettuce are the biological test species recommended by the U.S. Environmental Protection Agency, the Food and Drug Administration and the Organization for Economic Cooperation and Development for toxicity testing and environmental assessment. Millet is a riverine species widely distributed in the Midwest. The Illinois State Water Survey has conducted several studies using this species and the results show the millet to be rather promising for toxicity testing.The objective of this study was to compare the responses of lettuce, cucumber and millet seeds to heavy metals, including Cd, Cr(VI), Cu, Mn, Ni and Zn. Lettuce was most sensitive to metal toxicity, while results for cucumber and millet were mixed. The millet seeds, however, did show a predictable pattern of response similar to their response to phenolic toxicity. There was a fairly good correlation between 50 effect concentrations and no observed effect concentrations for millet (R2= 0.858).Lettuce and millet seeds are recommended for use together in toxicity tests of unknown, complex hazardous substances.
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