Toxic effects of 2,4,4′-trichlorobiphenyl (PCB-28) on growth, photosynthesis characteristics and antioxidant defense system of Lemna minor L.

Polychlorinated biphenyls (PCBs) are a common category of persistent man-made organic pollutants that are widespread in the ambient environment. Although Lemna minor L. is an extensively applied plant for aquatic remediation in ecotoxicology research worldwide, little is known regarding its responses to the potentially toxic effects of PCBs. For this study, a 14-day dissolved exposure was conducted to explore the effects of 2,4,4'-trichlorobiphenyl (PCB-28) on the growth, photosynthesis characteristics and antioxidant defense system of L. minor plants. We found that 100 and 200 mu g/L of PCB-28 decreased the fresh weight, chlorophyll and protein content, and activities of superoxide dismutase, peroxidase, glutathione S-transferase, and nitroreductase, whereas plasma membrane permeability, and the malondialdehyde and reactive oxygen species concentrations were increased. However, it was observed that 5 and 20 mu g/L of PCB-28 had no significant effects on these physiological indices. The ultra-structure of chloroplast demonstrated that 100 and 200 mu g/L PCB-28 severely damaged the chloroplast structures. Moreover, correlation analysis revealed that the content of reactive oxygen species had negative correlations with the fresh weight, chlorophyll and protein content, as well as the activities of superoxide dismutase, peroxidase, glutathione S-transferase, and nitroreductase, but had positive correlations with the malondialdehyde content and plasma membrane permeability. This work provides valuable data toward elucidating the physiology and biochemistry of PCBs induced phytotoxicity.