Classical and biochemical endpoints in the evaluation of phytotoxic effects caused by the herbicide trichloroacetate

Three terrestrial plant species, oat (Avena sativa), Chinese cabbage (Brass ica campestris cv. chinensis) and lettuce (Lactuca sativa), were exposed to different concentrations of herbicide TCA (sodium trichloroacetate) in a g rowth test according to guideline OECD # 208. Classical (i.e. germination a nd biomass) and biochemical (i.e., antioxydant enzyme activities) endpoints were investigated. Germination rate decreased significantly at 3.9 mg TCA kg dry soil(-1) (for oat and lettuce) and 62.5 mg TCA kg dry soil(-1) (for Chinese cabbage). Biomass decreased significantly only at 1.9 mg TCA kg dry soil(-1) (for oat and lettuce) and 15.6 mg TCA kg dry soil(-1) (for Chines e cabbage). The activities of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7) and glutathione reductase (EC 1.6.4 .2) increased significantly at the lowest concentration of TCA tested, i.e. 0.03 mg TCA kg dry soil(-1) (for oat and lettuce) and 0.48 mg TCA kg dry s oil(-1) (for Chinese cabbage). Our results showed a ranking of sensitivity among the different endpoints for the three plant species: enzyme activitie s > biomass > germination rate. The increase in antioxidant enzyme activiti es observed in this study ensured the detoxification of increased levels of active oxygen species, and presumably prevented the plants from undergoing oxidative stress damage. Thus, the use of enzyme activities will permit th e detection of early injury in plant growth testing. (C) 2000 Elsevier Scie nce B.V. All rights reserved.