Title: Toxicity and biotransformation of ZnO nanoparticles in the desert plants Prosopis juliflora-velutina, Salsola tragus and Parkinsonia florida

Authors: Guadalupe De La Rosa, Martha Laura Lopez-Moreno, Jose A. Hernandez-Viezcas, Milka O. Montes, Jose R. Peralta-Videa, Jorge L. Gardea-Torresdey

Addresses: Chemistry Department, The University of Texas at El Paso, 500 W. University Ave. El Paso, TX, 79968, USA; Departamento de Ingenieria Quimica, Universidad de Guanajuato, Col. N. Alta s/n, Guanajuato, Gto., 36050, Mexico. ' Chemistry Department, University of Puerto Rico, campus Mayaguez, P.O. Box 9000 Mayaguez, PR 00681, USA. ' Environmental Science, MSc Program, The University of Texas at El Paso, 500 W. University Ave. El Paso, TX 79968, USA. ' Chemistry Department, The University of Texas at El Paso, 500 W. University Ave. El Paso, TX, 79968, USA. ' Chemistry Department, The University of Texas at El Paso, 500 W. University Ave., El Paso, TX, 79968, USA. ' Chemistry Department and Environmental Science and Engineering, PhD Programme, The University of Texas at El Paso 500 W. University Ave. El Paso, TX, 79968, USA

Abstract: Although arid and semiarid regions account for about 40% of world land, no nanotoxicity studies on desert plants have been reported. In this investigation, Parkinsonia florida (blue palo verde), Prosopis juliflora-velutina (velvet mesquite) and Salsola tragus (tumbleweed) were selected to determine the phytotoxicity of ZnO nanoparticles (NPs) at germination stage. Seeds were treated with ZnO NP concentrations ranging between 0 and 4000 mg L⁻¹. From this, the germination rate, root elongation and Zn concentration in tissues were determined. Furthermore, X-ray Absorption Spectroscopic (XAS) studies were performed to obtain preliminary information on potential NP biotransformation within plant tissues. Results indicated that germination was not significantly affected (P < 0.05) in any of the three plant species. Also, root elongation in blue palo verde was reduced by 16%, with respect to control at 4000 mg ZnO L⁻¹. Tumbleweed root size diminished by 14% and 16% at ZnO NP levels of 500 and 2000 mg L⁻¹, respectively, and velvet mesquite root length was reduced to all ZnO NP concentrations used in this study. The 50% inhibitory concentration (IC50) for mesquite root elongation was between 1000 mg L⁻¹ and 2000 mg L⁻¹. XAS results demonstrated that ZnO NPs were biotransformed on/within the root and Zn was present as Zn(II) in the three desert plant species.

Keywords: ZnO nanoparticles; zinc oxide; nanophytotoxicity; desert plants; X-ray absorption spectroscopy; plant growth; nanotechnology; toxicity; biotransformation; nanotoxicity; phytotoxicity; germination rate; root elongation; zinc concentration.

DOI: 10.1504/IJNT.2011.040190

International Journal of Nanotechnology, 2011 Vol.8 No.6/7, pp.492 - 506

Published online: 19 May 2011 *

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