Stress Response and Tolerance of Zea mays to CeO₂ Nanoparticles: Cross Talk among H₂O₂, Heat Shock Protein, and Lipid Peroxidation

Abstract

The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO2 NPs to plants, and the possible transfer into the food chain, are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO2 NPs at 400 or 800 mg/kg. Stress related parameters, such as: H2O2, catalase (CAT) and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP 70), lipid peroxidation, cell death and leaf gas exchange were analyzed at 10, 15, and 20 days post germination. Confocal laser scanning microscopy was used to image H2O2 distribution in corn leaves. Results showed that the CeO2 NP treatments increased accumulation of H2O2, up to day 15, in phloem, xylem, bundle sheath cells, and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H2O2 levels. Both 400 and 800 mg/kg CeO2 NPs triggered the up regulation of the HSP 70 in roots, indicating a systemic stress response. None of the CeO2 NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO2 NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO2 NPs. Our results suggest that the CAT, APX and HSP 70 might help the plants defend against CeO2 NPs induced oxidative injury and survive NP exposure.

Response of Alfalfa under Salt Stress to the Application of Potassium Sulfate Nanoparticles

“…Similar results were reported in wheat plants following the application of NPK nanocomposites [58]. Nanoparticles also mitigated plasma membrane increased permeability and cell mortality in wheat plants [39] and in watermelon after foliar uptake of nanocomposites [29].…”

Cerium oxide nanoparticles: green synthesis and biological applications

“…CeO 2 -NPs could interfere with the nutrient transport functions of the membrane, 39 cause mechanical damage and membrane disruption 42,43 or generate reactive oxygen species (ROS) and induce oxidative stress. [38][39][40] The generation of ROS, most probably hydrogen peroxide, by CeO 2 -NPs is in agreement with observations noted by Xia et al 44 and Zhao et al 45 Hydrogen peroxide is capable of freely diffusing across cell walls and membranes, inducing cell damage.…”

Interactions between engineered nanomaterials and agricultural crops: implications for food safety

“…Other studies with different ENMs and crops revealed no differences in photosynthesis and gas exchange (net photosynthetic rate), transpiration, and stomatal conductance for CeO 2 -Zea mays, TiO 2 -Triticum aestivum, TiO 2 -Vicia faba or Fe 2 O 3 nanoparticlesGlycine max (Foltete et al, 2011;Larue et al, 2012a;Zhao et al, 2012a;Ghafariyan et al, 2013). However, unaltered gas exchange parameters did not mean that plants were unaffected; in fact, photosynthetic pigments and enzymatic structures at different stages of the photosynthesis reaction were found to be more sensitive endpoints than overall photosynthetic rates.…”

“…To date, the knowledge of ENMs-crop interactions in soil-based systems is very limited. In some published trials, sand or soil was either amended with nanomaterial powders or with ENMs suspensions (Du et al, 2011;Dimkpa et al, 2012;El-Temsah and Joner, 2012;Priester et al, 2012;Zhao et al, 2012a;Khodakovskaya et al, 2013). A design with outdoor lysimeters under field condition was first introduced to investigate the impact of ENMs on Triticum aestivum (wheat) growth and soil enzyme activities; here, the topsoil was ex-situ amended with TiO 2 and ZnO nanoparticles (Du et al, 2011).…”