Research article Cerium oxide nanoparticles alter the antioxidant capacity but do not impact tuber ionome in Raphanus sativus (L) Baltazar Corral-Diaz a, d , Jose R. Peralta-Videa a, b, c , Emilio Alvarez-Parrilla d , Joaquin Rodrigo-García e , Maria Isabel Morales a , Pedro Osuna-Avila d , Genhua Niu f , Jose A. Hernandez-Viezcas a , Jorge L. Gardea-Torresdey a, b, c, * a The University of Texas at El Paso, Department of Chemistry, 500 West University Ave., El Paso, TX 79968, USA b Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968, USA c UC Center for Environmental Implications of Nanotechnology (UCCEIN), The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968, USA d Universidad Aut onoma de Ciudad Juarez, Departamento de Química y Biología, Instituto de Ciencias Biom edicas, Anillo envolvente PRONAF y Estocolmo, Ciudad Juarez, Chih 32310, Mexico e Universidad Aut onoma de Ciudad Juarez, Departamento de Ciencias de la Salud, Instituto de Ciencias Biom edicas, Anillo envolvente PRONAF y Estocolmo, Ciudad Juarez, Chih 32310, Mexico f Texas AgriLife Research and Extension Center at El Paso, Texas A&M University, 1380 A&M Circle, El Paso, TX 79927, USA article info Article history: Received 31 July 2014 Accepted 29 September 2014 Available online 30 September 2014 Keywords: CeO 2 NPs Flavonoids Nutrients Antioxidants Radish abstract The effects of nCeO 2 on food quality are not well known yet. This research was performed to determine the impact of nCeO 2 on radish (Raphanus sativus L.). Plants were cultivated to full maturity in potting soil treated with nCeO 2 at concentrations of 0, 62.5, 125, 250, and 500 mg/kg. Germination, growth, photosynthesis, ionome, and antioxidants were evaluated at different growth stages. Results showed that at 500 mg/kg, nCeO 2 significantly retarded seed germination but did not reduce the number of germi- nated seeds. None of the treatments affected gas exchange, photosynthesis, growth, phenols, flavonoids, and nutrients' accumulation in tubers and leaves of adult plants. However, tubers' antioxidant capacity, expressed as FRAP, ABTS  and DPPH, increased by 30%, 32%, and 85%, respectively, in plants treated with 250 mg nCeO 2 kg 1 soil. In addition, cerium accumulation in tubers of plants treated with 250 and 500 mg/kg reached 72 and 142 mg/kg d wt, respectively. This suggests that nCeO 2 could improve the radical scavenging potency of radish but it might introduce nCeO 2 into the food chain with unknown consequences. © 2014 Published by Elsevier Masson SAS. 1. Introduction The rapid expansion of nanotechnology has triggered the pro- duction of large amounts of metal-based engineered nanoparticles (ENPs) (Casals et al., 2008; Roco, 2011; Kelleret al., 2013). This has raised concerns about the environmental buildup of ENPs, such as cerium dioxide (nCeO 2 ), and their impact on plants. nCeO 2 are massively produced and widely used (Piccino et al., 2012). In 2010, an estimate of the global material flow for nCeO 2 indicated that 8200 tons ended in landfill, 1400 in soil, 100 in air, and 300 in water (Keller et al., 2013). Currently, the environmental impacts of nCeO 2 are still not well understood. Thus, they are still included among the 14 engineered nanomaterials in the list of priority to be eval- uated for human health and environmental safety effects (OECD, 2010). Previous reports have shown that nCeO 2 reduce seed germina- tion in corn (Zea mays L.), tomato (Solanum lycopersicum L.) and cucumber (Cucumis sativus L.) (Lopez-Moreno et al., 2010a). But contrasting results have been reported for nCeO 2 effects on plant growth. Lopez-Moreno et al. reported that nCeO 2 increased root elongation in cucumber and corn but reduced root length in alfalfa and tomato. Radish (Raphanus sativus) is a worldwide consumed plant. Radish tubers have been known to have very high antioxi- dant and free radical scavenging activity, due to the high content of polyphenols (Lugasi et al., 1998). In addition, flavonoids found in radish extract have shown high radical scavenging potency (Takaya et al. 2003). Only one report has described the effects of nCeO 2 on the growth of radish (R. sativus L.) (Ma et al., 2010). Ma et al. (2010) * Corresponding author. The University of Texas at El Paso, Department of Chemistry, 500 West University Ave., El Paso, TX 79968, USA. E-mail address: jgardea@utep.edu (J.L. Gardea-Torresdey). Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy http://dx.doi.org/10.1016/j.plaphy.2014.09.018 0981-9428/© 2014 Published by Elsevier Masson SAS. Plant Physiology and Biochemistry 84 (2014) 277e285