Effect of cerium oxide nanoparticles on rice: a study involving the antioxidant defense system and in vivo fluorescence imaging

Evidence of translocation and physiological impacts of foliar applied CeO2 nanoparticles on cucumber (Cucumis sativus) plants

Currently, most of the nanotoxicity studies in plants involve exposure to the nanoparticles (NPs) through the roots. However, plants interact with atmospheric NPs through the leaves, and our knowledge on their response to this contact is limited. In this study, hydroponically grown cucumber (Cucumis sativus) plants were aerially treated either with nano ceria powder (nCeO2) at 0.98 and 2.94 g/m(3) or suspensions at 20, 40, 80, 160, and 320 mg/L. Fifteen days after treatment, plants were analyzed for Ce uptake by using ICP-OES and TEM. In addition, the activity of three stress enzymes was measured. The ICP-OES results showed Ce in all tissues of the CeO2 NP treated plants, suggesting uptake through the leaves and translocation to the other plant parts. The TEM results showed the presence of Ce in roots, which corroborates the ICP-OES results. The biochemical assays showed that catalase activity increased in roots and ascorbate peroxidase activity decreased in leaves. Our findings show that atmospheric NPs can be taken up and distributed within plant tissues, which could represent a threat for environmental and human health.

Exposure studies of core-shell Fe/Fe(3)O(4) and Cu/CuO NPs to lettuce (Lactuca sativa) plants: Are they a potential physiological and nutritional hazard?

Iron and copper nanomaterials are widely used in environmental remediation and agriculture. However, their effects on physiological parameters and nutritional quality of terrestrial plants such as lettuce (Lactuca sativa) are still unknown. In this research, 18-day-old hydroponically grown lettuce seedlings were treated for 15 days with core-shell nanoscale materials (Fe/Fe(3)O(4), Cu/CuO) at 10 and 20mg/L, and FeSO(4)·7H(2)O and CuSO(4)·5H(2)O at 10mg/L. At harvest, Fe, Cu, micro and macronutrients were determined by ICP-OES. Also, we evaluated chlorophyll content, plant growth, and catalase (CAT) and ascorbate peroxidase (APX) activities. Our results showed that iron ions/NPs did not affect the physiological parameters with respect to water control. Conversely, Cu ions/NPs reduced water content, root length, and dry biomass of the lettuce plants. ICP-OES results showed that nano-Cu/CuO treatments produced significant accumulation of Cu in roots compared to the CuSO(4)·5H(2)O treatment. In roots, all Cu treatments increased CAT activity but decreased APX activity. In addition, relative to the control, nano-Cu/CuO altered the nutritional quality of lettuce, since the treated plants had significantly more Cu, Al and S but less Mn, P, Ca, and Mg.

Single-bilayer graphene oxide sheet impacts and underlying potential mechanism assessment in germinating faba bean (Vicia faba L.)

This study investigates the impact of different single-bilayer graphene oxide sheet (hereafter 'graphene oxide', GO; size: 0.5-5 μm) concentrations (0, 100, 200, 400, 800 and 1,600 mg L(-1)) and underlying potential mechanisms in germinating faba bean (Vicia faba L.) seedlings. The study revealed both positive and negative concentration-dependent GO-effects on V. faba. Significant negative impacts of GO concentrations (ordered by magnitude of effect: 1600>200>100 mg GO L(-1)) were indicated by decreases in growth parameters and the activity of H2O2-decomposing enzymes (ascorbate peroxidase, APX; catalase, CAT), and by increases in the levels of electrolyte leakage (EL), H2O2, and lipid and protein oxidation. The positive impacts of 400 and 800 mg GO L(-1) included significant improvements in V. faba health status indicated by decreased levels of EL, H2O2, and lipid and protein oxidation, and by enhanced H2O2-decomposing APX and CAT activity, and increased proline and seed-relative water content. V. faba seedlings-polypeptide patterns strongly substantiated these GO-concentration effects. Overall, the positive effects of these two GO concentrations (800>400 mg L(-1)) on V. faba seedlings indicate their safe nature and allow to suggest further studies.

Cerium oxide nanoparticles modify the antioxidative stress enzyme activities and macromolecule composition in rice seedlings

Cerium oxide nanoparticles (nCeO2) have been shown to have significant interactions in plants; however, there are limited reports on their impacts in rice (Oryza sativa). Given the widespread environmental dispersal of nCeO2, it is paramount to understand its biochemical and molecular impacts on a globally important agricultural crop, such as rice. This study was carried out to determine the impact of nCeO2 on the oxidative stress, membrane damage, antioxidant enzymes' activities, and macromolecular changes in the roots of rice seedlings. Rice seeds (medium amylose) were grown for 10 days in nCeO2 suspensions (0-500 mg L(-1)). Results showed that Ce in root seedlings increased as the external nCeO2 increased without visible signs of toxicity. Relative to the control, the 62.5 mg nCeO2 L(-1) reduced the H2O2 generation in the roots by 75%. At 125 mg nCeO2 L(-1), the roots showed enhanced lipid peroxidation and electrolyte leakage, while at 500 mg L(-1), the nCeO2 increased the H2O2 generation in roots and reduced the fatty acid content. The lignin content decreased by 20% at 500 mg nCeO2 L(-1), despite the parallel increase in H2O2 content and peroxidase activities. Synchrotron μ-XRF confirmed the presence of Ce in the vascular tissues of the roots.

Citric acid modifies surface properties of commercial CeO2 nanoparticles reducing their toxicity and cerium uptake in radish (Raphanus sativus) seedlings

Little is known about the mobility, reactivity, and toxicity to plants of coated engineered nanoparticles (ENPs). Surface modification may change the interaction of ENPs with living organisms. This report describes surface changes in commercial CeO2 NPs coated with citric acid (CA) at molar ratios of 1:2, 1:3, 1:7, and 1:10 CeO2:CA, and their effects on radish (Raphanus sativus) seed germination, cerium and nutrients uptake. All CeO2 NPs and their absorption by radish plants were characterized by TEM, DLS, and ICP-OES. Radish seeds were germinated in pristine and CA coated CeO2 NPs suspensions at 50mg/L, 100mg/L, and 200mg/L. Deionized water and CA at 100mg/L were used as controls. Results showed ζ potential values of 21.6 mV and -56 mV for the pristine and CA coated CeO2 NPs, respectively. TEM images showed denser layers surrounding the CeO2 NPs at higher CA concentrations, as well as better distribution and smaller particle sizes. None of the treatments affected seed germination. However, at 200mg/L the CA coated NPs at 1:7 ratio produced significantly (p ≤ 0.05) more root biomass, increased water content and reduced by 94% the Ce uptake, compared to bare NPs. This suggests that CA coating decrease CeO2 NPs toxicity to plants.

Effect of cerium oxide nanoparticles on the quality of rice ( Oryza sativa L.) grains

Despite the remarkable number of publications on the interaction of engineered nanoparticles (ENPs) with plants, knowledge of the implications of ENPs in the nutritional value of food crops is still limited. This research was performed to study the quality of rice grains harvested from plants grown in soil treated with cerium oxide nanoparticles (nCeO2). Three rice varieties (high, medium, and low amylose) were cultivated to full maturity in soil amended with nCeO2 at 0 and 500 mg kg(-1) soil. Ce accumulation, nutrient content, antioxidant property, and nutritional quality of the rice grains were evaluated. Results showed that rice grains from nCeO2-treated plants had less Fe, S, prolamin, glutelin, lauric and valeric acids, and starch. Moreover, the nCeO2 reduced in grains all antioxidant values, except flavonoids. Medium- and low-amylose varieties accumulated more Ce in grains than the high-amylose variety, but the grain quality of the medium-amylose variety showed higher sensitivity to the nCeO2 treatment. These results indicate that nCeO2 could compromise the quality of rice. To the authors' knowledge, this is the first report on the effects nCeO2 on rice grain quality.

Toxicity assessment of cerium oxide nanoparticles in cilantro (Coriandrum sativum L.) plants grown in organic soil

Studies have shown that CeO₂ nanoparticles (NPs) can be accumulated in plants without modification, which could pose a threat for human health. In this research, cilantro (Coriandrum sativum L.) plants were germinated and grown for 30 days in soil amended with 0 to 500 mg kg⁻¹ CeO₂ NPs and analyzed by spectroscopic techniques and biochemical assays. At 125 mg kg⁻¹, plants produced longer roots (p ≤ 0.05), and at 500 mg kg⁻¹, there was higher Ce accumulation in tissues (p ≤ 0.05). At 125 mg, catalase activity significantly increased in shoots and ascorbate peroxidase in roots (p ≤ 0.05). The FTIR analyses revealed that at 125 mg kg⁻¹ the CeO₂ NPs changed the chemical environment of carbohydrates in cilantro shoots, for which changes in the area of the stretching frequencies were observed. This suggests that the CeO₂ NPs could change the nutritional properties of cilantro.