Yukui Rui

Phytotoxic Mechanism of Nanoparticles: Destruction of Chloroplasts and Vascular Bundles and Alteration of Nutrient Absorption

This study focused on determining the phytotoxic mechanism of CeO2 nanoparticles (NPs): destroying chloroplasts and vascular bundles and altering absorption of nutrients on conventional and Bt-transgenic cottons. Experiments were designed with three concentrations of CeO2 NPs including: 0, 100 and 500 mg·L−1, and each treatment was three replications. Results indicate that absorbed CeO2 nanoparticles significantly reduced the Zn, Mg, Fe, and P levels in xylem sap compared with the control group and decreased indole-3-acetic acid (IAA) and abscisic acid (ABA) concentrations in the roots of conventional cotton. Transmission electron microscopy (TEM) images revealed that CeO2 NPs were absorbed into the roots and subsequently transported to the stems and leaves of both conventional and Bt-transgenic cotton plants via xylem sap. In addition, the majority of aggregated CeO2 NPs were attached to the external surface of chloroplasts, which were swollen and ruptured, especially in Bt-transgenic cotton. The vascular bundles were destroyed by CeO2 nanoparticles, and more damage was observed in transgenic cotton than conventional cotton.

Transformation of ceria nanoparticles in cucumber plants is influenced by phosphate

Transformation is a critical factor that affects the fate and toxicity of manufactured nanoparticles (NPs) in the environment and living organisms. This paper aims to investigate the effect of phosphate on the transformation of CeO2 NPs in hydroponic plants. Cucumber seedlings were treated with 2000 mg/L CeO2 NPs in nutrient solutions with or without adding phosphate (+P or -P) for 3 weeks. Large quantities of needle-like CePO4 was found outside the epidermis in the +P group. While in the -P group, CePO4 only existed in the intercellular spaces and vacuole of root cells. X-ray absorption near edge spectroscopy (XANES) indicates that content and percentage of Ce-carboxylates in the shoots of -P group (418 mg/kg, 67.5%) were much higher than those in the +P group (30.1 mg/kg, 21%). The results suggest that phosphate might influence the transformation process of CeO2 NPs in plants and subsequently their ultimate fate in the ecosystem.

Fate and Phytotoxicity of CeO2 Nanoparticles on Lettuce Cultured in the Potting Soil Environment

Cerium oxide nanoparticles (CeO2 NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO2 NPs by lettuce (Lactuca sativa), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO2 NPs per kg soil. Results showed that lettuce in 100 mg·kg-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg-1 CeO2 NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO2 NPs phytotoxicity. These findings demonstrate CeO2 NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo.

Effects of CuO nanoparticles on insecticidal activity and phytotoxicity in conventional and transgenic cotton.

Nanoparticles and transgenic plants are recent scientific developments that require systematic study to understand their potential risks to human health. The effects of CuO nanoparticles (NPs) on Bt-transgenic cotton and conventional cotton are reported here. CuO NPs inhibited the growth, development, nutrient content, and indole-3-acetic acid (IAA) and abscisic acid (ABA) concentrations of transgenic and conventional cotton. Transmission electron microscopy (TEM) images showed CuO NPs aggregated on the epidermis of conventional cotton leaves, whereas it had reached into the cells of transgenic cotton leaves by endocytosis. Most CuO NPs aggregates were found on the root outer epidermis and the rest were located in intercellular spaces of both conventional and Bt-transgenic cottons. CuO NPs enhanced the expression of the exogenous gene encoding of Bt toxin protein in leaves and roots, especially at low CuO NP concentrations, providing an important benefit for Bt cotton insect resistance.

Carbon Nanotubes Filled with Different Ferromagnetic Alloys Affect the Growth and Development of Rice Seedlings by Changing the C:N Ratio and Plant Hormones Concentrations

The aim of this study was to investigate the phytotoxicity of thin-walled carbon nanotubes (CNTs) to rice (Oryza sativa L.) seedlings. Three different CNTs, including hollow multi-walled carbon nanotubes (MWCNTs), Fe-filled carbon nanotubes (Fe-CNTs), and Fe-Co-filled carbon nanotubes (FeCo-CNTs), were evaluated. The CNTs significantly inhibited rice growth by decreasing the concentrations of endogenous plant hormones. The carbon to nitrogen ratio (C:N ratio) significantly increased in rice roots after treatments with CNTs, and all three types of CNTs had the same effects on the C:N ratio. Interestingly, the increase in the C:N ratio in roots was largely because of decreased N content, indicating that the CNTs significantly decreased N assimilation. Analyses of the Fe and Co contents in plant tissues, transmission electron microscope (TEM) observations and energy dispersive X-ray spectroscopy (EDS) analysis proved that the CNTs could penetrate the cell wall and the cell membrane, and then enter the root cells. According to the authors knowledge, this is the first time to study the relationship between carbon nanotubes and carbon nitrogen ratio and plant hormones.

Response difference of transgenic and conventional rice (Oryza sativa) to nanoparticles (γFe2O3)

Nanoparticles (NPs) are an increasingly common contaminant in agro-environments, and their potential effect on genetically modified (GM) crops has been largely unexplored. GM crop exposure to NPs is likely to increase as both technologies develop. To better understand the implications of nanoparticles on GM plants in agriculture, we performed a glasshouse study to quantify the uptake of Fe2O3 NPs on transgenic and non-transgenic rice plants. We measured nutrient concentrations, biomass, enzyme activity, and the concentration of two phytohormones, abscisic acid (ABA) and indole-3-acetic acid (IAA), and malondialdehyde (MDA). Root phytohormone inhibition was positively correlated with Fe2O3 NP concentrations, indicating that Fe2O3 had a significant influence on the production of these hormones. The activities of antioxidant enzymes were significantly higher as a factor of low Fe2O3 NP treatment concentration and significantly lower at high NP concentrations, but only among transgenic plants. There was also a positive correlation between the treatment concentration of Fe2O3 and iron accumulation, and the magnitude of this effect was greatest among non-transgenic plants. The differences in root phytohormone production and antioxidant enzyme activity between transgenic and non-transgenic rice plants in vivo suggests that GM crops may react to NP exposure differently than conventional crops. It is the first study of NPs that may have an impact on GM crops, and a realistic significance for food security and food safety.

The effects of Fe2O3 nanoparticles on physiology and insecticide activity in non-transgenic and Bt-transgenic cotton

As the demands for nanotechnology and nanoparticle (NP) applications in agriculture increase, the ecological risk has drawn more attention because of the unpredictable results of interactions between NPs and transgenic crops. In this study, we investigated the effects of various concentrations of Fe2O3 NPs on Bt-transgenic cotton in comparison with conventional cotton for 10 days. Each treatment was conducted in triplicate, and each experiment was repeated three times. Results demonstrated that Fe2O3 NPs inhibited the plant height and root length of Bt-transgenic cotton and promoted root hairs and biomass of non-transgenic cotton. Nutrients such as Na and K in Bt-transgenic cotton roots increased, while Zn contents decreased with Fe2O3 NPs. Most hormones in the roots of Bt-transgenic cotton increased at low Fe2O3 NP exposure (100 mg⋅L-1) but decreased at high concentrations of Fe2O3 NPs (1000 mg⋅L-1). Fe2O3 NPs increased the Bt-toxin in leaves and roots of Bt-transgenic cotton. Fe2O3 NPs were absorbed into roots, then transported to the shoots of both Bt-transgenic and non-transgenic cottons. The bioaccumulation of Fe2O3 NPs in plants might be a potential risk for agricultural crops and affect the environment and human health.

Toxicity and bio-effects of CuO nanoparticles on transgenic Ipt-cotton

ABSTRACT This study investigated the effects of copper oxide nanoparticles (CuO NPs) on the growth and development of transgenic cotton harboring the Ipt gene, which encodes isopentenyl transferase (Ipt). Three concentrations of CuO NPs were evaluated: 10, 200, and 1000 mg·L-1, each with three replicates. The height and the root length were 26.91% and 42.80% decreased after 10-day exposure with 1000 mg·L-1 CuO NPs, respectively.In addition, less abundant on root hairs and lower in shoot biomass of Ipt-cotton when compared with the control group. The growth of Ipt-cotton was not affected by 10 mg·L-1 CuO NPs, but a high concentration of CuO NPs promoted the absorption of Fe and Na into roots, and inhibited the production of phytohormones in Ipt-cotton. The CuO NPs increased the concentration of iPA in shoots, which can delay senescence. The extent of the increase in iPA in response to CuO NPs should be relative to the amount of Ipt immobilized onto the NPs in the plant tissue. To our knowledge, this is the first study to evaluate the phytotoxicity of CuO NPs to Ipt-transgenic cotton. These results establish a baseline for further research on the effects of nanoparticles on transgenic crops harboring the Ipt gene.

Effects of TiO2 nanoparticles on wheat (Triticum aestivum L.) seedlings cultivated under super-elevated and normal CO2 conditions

Concerns over the potential risks of nanomaterials to ecosystem have been raised, as it is highly possible that nanomaterials could be released to the environment and result in adverse effects on living organisms. Carbon dioxide (CO2) is one of the main greenhouse gases. The level of CO2 keeps increasing and subsequently causes a series of environmental problems, especially for agricultural crops. In the present study, we investigated the effects of TiO2 NPs on wheat seedlings cultivated under super-elevated CO2 conditions (5000 mg/L CO2) and under normal CO2 conditions (400 mg/L CO2). Compared to the normal CO2 condition, wheat grown under the elevated CO2 condition showed increases of root biomass and large numbers of lateral roots. Under both CO2 cultivation conditions, the abscisic acid (ABA) content in wheat seedlings increased with increasing concentrations of TiO2 NPs. The indolepropioponic acid (IPA) and jasmonic acid (JA) content notably decreased in plants grown under super-elevated CO2 conditions, while the JA content increased with increasing concentrations of TiO2 NPs. Ti accumulation showed a dose-response manner in both wheat shoots and roots as TiO2 NPs concentrations increased. Additionally, the presence of elevated CO2 significantly promoted Ti accumulation and translocation in wheat treated with certain concentrations of TiO2 NPs. This study will be of benefit to the understanding of the joint effects and physiological mechanism of high-CO2 and nanoparticle to terrestrial plants.

Comparative effects of nano and bulk-Fe3O4 on the growth of cucumber (Cucumis sativus)

Cucumber (Cucumis sativus) plants were cultivated in hydroponic media with nano and bulk- iron oxide (Fe3O4) (50, 500 and 2000 mg/L) over a period of 21 days. At the low concentration (50 mg/L), nano-Fe3O4 resulted in reduction of biomass and enzyme activities compared to the control. However, at the higher concentration of nano-Fe3O4 dosage (2000 mg/L), there was a significant increase in biomass, antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD). In contrary, the high concentration of bulk-Fe3O4 caused phytotoxicity in terms of biomass and enzymes activity. The phytotoxicity was dependent on the particles property (mainly sizes and aggregation) for nano-F3O4 and concentration dependent for bulk-Fe3O4. The particle size is an important factor that can influence the bioavailability of nanomaterials, which need to be included when evaluating the exposure of nanomaterials and their deleterious effects in the environment. These promising results can help to develop the possible application of Fe3O4 NPs which may improve nutrient management to overcome food security.