Time Matters: the Toxicity of Zinc Oxide Nanoparticles to Lemna minor L. Increases with Exposure Time
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The use of zinc oxide nanoparticles (nano-ZnO) has rapidly increased in recent years, and this has triggered the need for versatile toxicity tests that can be used to test a range of different exposure scenarios. Acute exposure studies, using a variety of plant species, have overwhelmingly demonstrated nano-ZnO-induced toxicity, but substantial differences in the degree of phytotoxicity are reported in different studies. Here, we analysed the role of exposure time in determining the variation in phytotoxic effects. Using the model species Lemna minor, the effects of short-term (24 h), standardised (1 week) and chronic (up to 6 weeks) nano-ZnO exposure were compared. Nano-ZnO effects on Lemna minor growth indicators (biomass growth rate, root length), chlorophyll content and photosynthetic efficiency were measured. Rapid inhibitory effects of nano-ZnO on the maximal quantum yield of photosystem II could be measured after just 24-h exposure. Standardised (1 week) experiments revealed phytotoxic effects on Lemna minor biomass growth. More severe inhibitory effects on growth developed gradually over 4 to 6 weeks exposure to nano-ZnO, and these were qualitatively associated with increased zinc content in the plant. Such dynamics of nano-ZnO toxicity have not been elucidated before, and this study emphasises the importance of exposure time in studies of nanoparticle toxicity. We conclude that short-term, standardised experiments can potentially underestimate the environmental phytotoxicity, which may result from chronic exposure to nano-ZnO.
KeywordsLemna minor Nano-ZnO Chronic toxicity Acute toxicity
X.C. gratefully acknowledges the support by the CSC (China Scholarship Council). M.A.K.J. acknowledges the support by W.o.B. The authors appreciate the technical assistance (Atomic Absorption Spectroscopy) from Dr. Qiushi Xie and help with the physico-chemical characterisation of particles from Dr. Guillaume Yuhel.
- Antoine, M., Florence, M., Éric, P., Gauthier, L., & Emmanuel, F. (2017). Environmental impact of engineered carbon nanoparticles: from releases to effects on the aquatic biota. Current Opinion in Biotechnology, 46(2017), 1–6.Google Scholar
- Boxall, A., Chaudhry, Q., Sinclair, C., Jones, A., Jefferson, B., & Watts, C. (2007). Current and future predicted environmental exposure to engineered nanoparticles. York: CSL.Google Scholar
- El Badawy, A. M., Luxton, T. P., Silva, R. G., Scheckel, K. G., Suidan, M. T., & Tolaymat, T. M. (2010). Impact of environmental conditions (pH, ionic strength, and electrolyte type) on the surface charge and aggregation of silver nanoparticles suspensions. Environmental Science and Technology, 44(4), 1260–1266.CrossRefGoogle Scholar
- García-Hevia, L., Valiente, R., Martín-Rodríguez, R., Renero-Lecuna, C., González, J., Rodríguez-Fernández, L., … Fanarraga, M. L. (2016). Nano-ZnO leads to tubulin macrotube assembly and actin bundling, triggering cytoskeletal catastrophe and cell necrosis. Nanoscale, 8(21), 10963–10973.CrossRefGoogle Scholar
- Hernandez-Viezcas, J. A., Castillo-Michel, H., Servin, A. D., Peralta-Videa, J. R., & Gardea-Torresdey, J. L. (2011). Spectroscopic verification of zinc absorption and distribution in the desert plant Prosopis juliflora-velutina (velvet mesquite) treated with ZnO nanoparticles. Chemical Engineering, 170(1–3), 346–352.CrossRefGoogle Scholar
- Li, N., Georas, S., Alexis, N., Fritz, P., Xia, T., Williams, M. A., et al. (2016). A work group report on ultrafine particles (American Academy of Allergy, Asthma & Immunology): why ambient ultrafine and engineered nanoparticles should receive special attention for possible adverse health outcomes in human subjects. Journal of Allergy and Clinical Immunology, 138(2), 386–396.CrossRefGoogle Scholar
- Mahajan, P., Dhoke, S. K., & Khanna, A. S. (2011). Effect of nano-ZnO particle suspension on growth of mung (Vigna radiata) and gram (Cicer arietinum) seedlings using plant agar method. Nanotechnology, 2011(9), 1–7.Google Scholar
- Ma, H., Wallis, L. K., Diamond, S., Li, S., Canas-Carrell, J., & Parra, A. (2014). Impact of solar UV radiation on toxicity of ZnO nanoparticles through photocatalytic reactive oxygen species (ROS) generation and photo-induced dissolution. Environmental Pollution, 193(2014), 165–172.CrossRefGoogle Scholar
- OECD (2002). OECD guidelines for the testing of chemicals: revised proposal for a new guideline 221. Lemna sp. growth inhibition test. OECD.Google Scholar
- Pirson, A., & Göllner, E. (1953). Beobachtungen zur Entwicklungsphysiologie der Lemna minor L. Flora, 140, 485–498.Google Scholar
- Poynton, H. C., Lazorchak, J. M., Impellitteri, C. a, Smith, M. E., Rogers, K., Patra, M., … Vulpe, C. D. (2011). Differential gene expression in Daphnia magna suggests distinct modes of action and bioavailability for ZnO nanoparticles and Zn ions. Environmental Science & Technology, 45(2), 762–768.CrossRefGoogle Scholar