A comparative study of classical and biochemical endpoints for phytotoxicity testing of chlorobenzoic acids

The phytotoxicity of chlorobenzoic acids (CBAs) was studied and the biochemical endpoints' suitability and sensibility was evaluated. Two terrestrial plant species in the same family were exposed to different concentrations of CBAS and tested their germination according to the guideline of Organization for Economic Cooperation and Development (OECP, 1984). The results showed that CBA dose-inhibition rate of classical endpoint had the distinct linear relationship in the range of 10%-50% inhibition rate for root elongation (p < 0.01), and the dose variances of CBAs had the greater influence on the inhibition rate of germination than on inhibition rate of root elongation. The CBA dose half effect concentration-inhibition rate of two antioxidant enzyme activity superoxide dismutase (SOD) and catalase (CAT) had the quadratic relationship, and CBA dose-inhibition rate of the peroxides (POD) activity had the linear relationship (p < 0.05). Comparing the half effect concentration (EC50) of two kinds of endpoints, the POD activity was more sensitive than classical endpoint, however, SOD and CAT activity were not sensitive in the experiment.