Use of millet root elongation for toxicity tests of phenolic compounds

Millet root elongation was used for toxicity tests of phenol and seven chlorophenols. Each compound was tested twice, all with a control and six concentration levels in quadruplicates. Each test solution contained 15 seeds. The results showed that the order of decreasing toxicity is trichlorophenol, dichlorophenol, chlorophenol, and phenol. The root elongation method is more sensitive than the biomass method; however, it is time consuming. Phenolic compounds at low concentration stimulated the growth of root, but when the concentration is further increased, the stimulation effect is reversed and inhibition takes place.