Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants

Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanurn lycopersicum L.) plants were cultivated for 210 days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO(2), CA + nCeO(2)) bulk cerium oxide (bCeO(2)), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500 mg/kg, both the uncoated and CA + nCeO(2) increased shoot length by similar to 9 and similar to 13%, respectively, while bCeO(2) and CeAc decreased shoot length by similar to 48 and similar to 26%, respectively, compared with MPW (p <= 0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA + nCeO(2) at 250 mg/kg, but reduced by bCeO(2) at 62.5 mg/kg, compared with MPW. At 250 and 500 mg/kg, nCeO(2) increased Ce in roots by 10 and 7 times, compared to CA + nCeO(2), but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO(2) nor CA + nCeO(2) affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125 mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500 mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO(2) at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO(2) at 62.5 mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO(2) on tomato plants. (C) 2015 Elsevier B.V. All rights reserved.