Physiological effect of anatase TiO2 nanoparticles on Lemna minor

Manufactured metal oxide nanoparticles (NPs) are being used on a large scale, and these particles will inevitably reach a body of water through wastewater and urban runoff. The ecotoxicological study of these NPs on hydrophyte is limited at present. Lemna minor was exposed to media with different concentrations of titanium dioxide (TiO2) NPs or bulk TiO2 for 7 d. The changes in plant growth, chlorophyll, antioxidant defense enzymes (peroxidase [POD], catalase [CAT], and superoxide dismutase [SOD] activities), and malondialdehyde (MDA) content were measured in the present study. The particle size of TiO2 NPs and the zeta potential of TiO2 NPs and of bulk TiO2 in the culture media were also analyzed to complementally study the toxicity of these materials on duckweed. The results showed that the effect of TiO2 NPs on plant growth was more obvious than bulk TiO2. Titanium dioxide NPs stimulated plant growth in low concentrations, but inhibited plant growth at high concentrations. The POD, SOD, and CAT activity of Lemna minor increased when TiO2 NP concentration was lower than 200 mg/L to eliminate accumulated reactive oxygen species in plant cells. The SOD activity decreased when the TiO2 NP concentration was higher than 200 mg/L, and the plant cell membrane encountered serious damage from 500 mg/L TiO2 NP concentration in the culture media. Environ. Toxicol. Chem. 2012; 31: 2147–2152. © 2012 SETAC