Article

Fate of CuO and ZnO Nano- and Microparticles in the Plant Environment

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Abstract

The environmental fate of metal oxide particles as a function of size was assessed by comparing the behavior of CuO or ZnO nanoparticles (NPs) to that of the corresponding microparticles (MPs) in a sand matrix, with and without wheat (Triticum aestivum L.) growth. After 14 days of incubation in the planted sand, the CuO and ZnO NPs were increased from their nominal sizes of <50 nm and <100 nm, to ≈317 nm and ≈483 nm, respectively. Accordingly, the negative surface charge of colloids present in aqueous extracts from the sand amended with CuO (-27.0 mV) and ZnO (-10.0 mV) NPs was reduced by the presence of plants, to -19.8 mV and -6.0 mV, respectively. The surface charge of the MPs was not influenced by plants. Plant growth increased dissolution of NPs and MPs of both metal oxides in the sand from <0.3 mg/kg to about 1.0 mg/kg for the CuO products, and from ≤0.6 mg/kg to between 1.0 and 2.2 mg/kg for the Zn products. The NP or MP products reduced wheat root length by ≈60 % or ≈50 % from control levels; CuO was more toxic than ZnO. X-ray absorption spectroscopy (XAS) analysis showed that treatments with MPs or NPs of ZnO led to similar accumulations of Zn-phosphate species in the shoots, likely from dissolution of ZnO. Exposure to CuO NPs or MPs resulted in similar XAS spectra for Cu in the shoots, explained by plant accumulation of both CuO and CuI-sulfur complexes. These findings demonstrate the similarities between commercial NPs and MPs of CuO or ZnO in wheat plants, with greater root toxicity correlating with smaller particle size. Factors from the sand and the plant modified the aggregation or dissolution of both types of particles, thus, influencing their environmental fates.

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... 11,12 Additionally, modulation of metal reductase enzyme activities that could alter particulate Cu toxicity in plants have been reported. 13 However, Cu is also known to modulate the production of a variety of critically important primary and secondary metabolites in different organisms, including suppression of siderophores but enhancement of indoleacetic acid production in bacteria 14,15 and inhibition of gluconate and butyrate in wheat. 16 Increases in the levels of chlorophylls, antioxidants, and phenolic compounds have also been recorded in lettuce exposed to Cu. 17 In addition to anticipated dose-dependent outcomes, such effects could also be Cu-type dependent, such as with copper oxide (CuO) nanoparticles (NPs) and Cu ions in Pseudomonas where the CuO NPs depressed, whereas ionic Cu was indifferent to siderophore production. ...
... 16 Increases in the levels of chlorophylls, antioxidants, and phenolic compounds have also been recorded in lettuce exposed to Cu. 17 In addition to anticipated dose-dependent outcomes, such effects could also be Cu-type dependent, such as with copper oxide (CuO) nanoparticles (NPs) and Cu ions in Pseudomonas where the CuO NPs depressed, whereas ionic Cu was indifferent to siderophore production. 15 Despite potential environmental implications, Cu pesticides continue to be the industry standard for crop protection due to a lack of suitable alternatives. There is, however, an increasing quest to improve the efficiency of Cu use to minimize its environmental footprint. ...
... However, CuO NPs are known to dissolve more rapidly than their bulk equivalents. 15,42 Also, the dissolution efficiency of CuO NPs is greater at low CuO NP concentrations than at high concentrations, due likely to enhanced particle aggregation at higher concentrations. 13 A potentially higher dissolution of CuO NPs at 50 and 100 ppm could explain the higher levels of THC and CBD evoked by these treatments over the control plants, compared to 500 ppm. ...
... It is essential to employ copper and its compounds as NPs in plant and agricultural systems to increase production and reduce environmental toxicity. The Cu-NPs-treated wheat shoot was studied by Dimkpa et al. [75]. The organ, tissue, and cellular levels of organ, tissue, and cell biotransformation were observed to be limited, as were the potential translocation routes for Cu-NPs [75]. ...
... The Cu-NPs-treated wheat shoot was studied by Dimkpa et al. [75]. The organ, tissue, and cellular levels of organ, tissue, and cell biotransformation were observed to be limited, as were the potential translocation routes for Cu-NPs [75]. According to Zhao et al. [76], the application of Cu-NPs can cause an increase or reduction in the content of sugars, organic acids, amino acids, and fatty acids in plants. ...
... The Ag-NPs were obtained from leaf extract of Hyptis suaveolens (L.) of 22 nm particle size with 29.50 mv and 1.394 ms cm −1 zeta potential and conductivity respectively. Four different doses (25,50,75, and 100 ppm) of Ag-NPs synthesized on Prosopis juliflora (L.) were tested. The result showed a positive impact on phenylalanine ammonia-lyase (PAL) activity and a neutral effect on other contents. ...
Article
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Increasing demand for engineered Nanomaterial (ENMs) that have been widely applied in plant systems, for the improvement of quality, development, growth, nutritive value, and gene preservation. The uptake, translocation, biotransformation, and the associated perils of application of Nanomaterial in the crops demand a much deeper understanding of the biochemical, physiological, and molecular mechanisms of the florae in relation to nanoparticles (NPs). Interaction between different plant parts and NPs resulted in various changes in physiology, morphology, and genotoxicity, indicating positive as well as negative feedback by NMs over the various mechanisms of the plants and their species. NMs may open new and safer opportunities for smart delivery of biomolecules and new strategies in plant genetic engineering, with the final aim to enhance plant defense and/or stimulate plant growth and development and, ultimately, crop production. This review summarizes the current understanding and the future possibilities of research relevant to plant-nanoparticles integrations.
... However, ZnO NPs regarded to be one of the most significant nanomaterials and are frequently utilized as nanofertilizers, particularly in locations with a Zn shortage, to promote plant development and growth [21]. According to [22] adding ZnO NP may help with nutritional deficiencies and increase agricultural yields. Due to ZnO NPs' extensive use in the agricultural industry, recent research has demonstrated a favorable effect on plant development and physiology [23]. ...
... Zinc is an essential micronutrient needed for dry matter accumulation and plant growth [22]. ZnO NPs have a high absorption rate and transfer, ensuring an adequate quantity of Zn for its utilization in plant growth and development [87]. ...
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Background The biosynthesis of zinc oxide nanoparticles (ZnO NPs) using Enterobacter sp. and the evaluation of their antimicrobial and copper stress (Cu + 2)-reducing capabilities in Vicia faba (L.) plants. The green-synthesized ZnO NPs were validated using X-ray powder diffraction (XRD); Fourier transformed infrared (FTIR), Ultraviolet-Visible spectroscopy (UV-Vis), Transmission electron microscope (TEM) and scanning electron microscopy (SEM) techniques. ZnO NPs could serve as an improved bactericidal agent for various biological applications. as well as these nanoparticles used in alleviating the hazardous effects of copper stress on the morphological and physiological traits of 21-day-old Vicia faba (L.) plants. Results The results revealed that different concentrations of ZnO NPs (250, 500, or 1000 mg L-1) significantly alleviated the toxic effects of copper stress (100 mM CuSO 4) and increased the growth parameters, photosynthetic efficiency (Fv/Fm), and pigments (Chlorophyll a and b) contents in Cu-stressed Vicia faba (L.) seedlings. Furthermore, applying high concentration of ZnO NPs (1000 mg L-1) was the best dose in maintaining the levels of antioxidant enzymes (CAT, SOD, and POX), total soluble carbohydrates, total soluble proteins, phenolic and flavonoid in all Cu-stressed Vicia faba (L.) seedlings. Additionally, contents of Malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2) were significantly suppressed in response to high concentrations of ZnO NPs (1000 mg L-1) in all Cu-stressed Vicia faba (L.) seedlings. Also, it demonstrates strong antibacterial action (0.9 mg/ml) against various pathogenic microorganisms. Conclusions The ZnO NPs produced in this study demonstrated the potential to enhance plant detoxification and tolerance mechanisms, enabling plants to better cope with environmental stress. Furthermore, these nanoparticles could serve as an improved bactericidal agent for various biological applications.
... However, ZnO NPs regarded to be one of the most significant nanomaterials and are frequently utilized as nanofertilizers, particularly in locations with a Zn shortage, to promote plant development and growth [21]. According to [22] adding ZnO NP may help with nutritional deficiencies and increase agricultural yields. Due to ZnO NPs' extensive use in the agricultural industry, recent research has demonstrated a favorable effect on plant development and physiology [23]. ...
... Zinc is an essential micronutrient needed for dry matter accumulation and plant growth [22]. ZnO NPs have a high absorption rate and transfer, ensuring an adequate quantity of Zn for its utilization in plant growth and development [87]. ...
Article
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Background The biosynthesis of zinc oxide nanoparticles (ZnO NPs) using Enterobacter sp. and the evaluation of their antimicrobial and copper stress (Cu+ 2)-reducing capabilities in Vicia faba (L.) plants. The green-synthesized ZnO NPs were validated using X-ray powder diffraction (XRD); Fourier transformed infrared (FTIR), Ultraviolet-Visible spectroscopy (UV-Vis), Transmission electron microscope (TEM) and scanning electron microscopy (SEM) techniques. ZnO NPs could serve as an improved bactericidal agent for various biological applications. as well as these nanoparticles used in alleviating the hazardous effects of copper stress on the morphological and physiological traits of 21-day-old Vicia faba (L.) plants. Results The results revealed that different concentrations of ZnO NPs (250, 500, or 1000 mg L⁻¹) significantly alleviated the toxic effects of copper stress (100 mM CuSO4) and increased the growth parameters, photosynthetic efficiency (Fv/Fm), and pigments (Chlorophyll a and b) contents in Cu-stressed Vicia faba (L.) seedlings. Furthermore, applying high concentration of ZnO NPs (1000 mg L⁻¹) was the best dose in maintaining the levels of antioxidant enzymes (CAT, SOD, and POX), total soluble carbohydrates, total soluble proteins, phenolic and flavonoid in all Cu-stressed Vicia faba (L.) seedlings. Additionally, contents of Malondialdehyde (MDA) and hydrogen peroxide (H2O2) were significantly suppressed in response to high concentrations of ZnO NPs (1000 mg L⁻¹) in all Cu-stressed Vicia faba (L.) seedlings. Also, it demonstrates strong antibacterial action (0.9 mg/ml) against various pathogenic microorganisms. Conclusions The ZnO NPs produced in this study demonstrated the potential to enhance plant detoxification and tolerance mechanisms, enabling plants to better cope with environmental stress. Furthermore, these nanoparticles could serve as an improved bactericidal agent for various biological applications.
... After being applied to the soil, ZnO NPs were partially absorbed directly by the rice plant roots. During root uptake and transportation within the plant, the NPs were broken down by organic acids present in the plant, and the released Zn was utilized in the form of soluble Zn 2+ or organic Zn (Dimkpa et al., 2013). Another portion of ZnO NPs dissolved in the soil due to acidic substances and combined with phosphate ions, resulting in Zn phosphate that was then used by rice plants. ...
... Amino acids, as organic molecules, can enhance plant response and absorption of Zn after reacting with it, thereby increasing the Zn content in milled rice (Xiao et al., 2022). Previous studies (Dimkpa et al., 2013;Wang et al., 2013) have shown that when ZnO NPs are applied to the soil, plants take up Zn in the form of soluble Zn 2+ rather than as ZnO NPs. This indicates that the application of ZnO NPs increases the concentration of Zn in rice grains without posing risks to human consumption or health. ...
Article
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Zinc oxide nanoparticles (ZnO NPs) have been widely used in agriculture as a new type of Zn fertilizer, and many studies were conducted to evaluate the effect of ZnO NPs on plant growth. However, there are relatively few studies on the effects of application methods and appropriate dosages of ZnO NPs on rice yield, quality, grain Zn content, and distribution. Therefore, in the 2019 and 2020, field trials were conducted with six ZnO NPs basal application dosages of no ZnO NPs, 3.75 kg hm⁻², 7.5 kg hm⁻², 15 kg hm⁻², 30 kg hm⁻², and 60 kg hm⁻², and the effects of ZnO NPs application on rice yield, quality, grain Zn content, and distribution were investigated. The results demonstrated that applying ZnO NPs in Zn-deficient soils (available Zn < 1.0 mg kg⁻¹) increased rice grain yield by 3.24%–4.86% and 3.51%–5.12% in 2019 and 2020, respectively. In addition, ZnO NPs improved the quality of rice by increasing the head milling rate, reducing chalky grain percentage, and increasing the taste value and breakdown of rice. In terms of Zn accumulation in rice, ZnO NPs application significantly increased the Zn content in both milled rice and brown rice, compared with no Zn treatment, in 2019 and 2020, Zn content in milled rice significantly increased by 20.46%–41.09% and 18.11%–38.84%, respectively, and in brown rice significantly increased by 25.78%–48.30% and 20.86%–42.00%, respectively. However, the Zn fertilizer utilization gradually decreased with increasing ZnO NPs application dosage. From the perspective of yield, rice quality, Zn fertilizer utilization, and Zn accumulation, basal application of 7.5 kg–30 kg hm⁻² ZnO NPs is beneficial for rice yield and quality improvement and rice Zn accumulation. This study effectively demonstrated that ZnO NPs could be a potential high‐performed fertilizer for enhancing rice yield, quality, and zinc content of edible grain fraction synergistically.
... ZnO-NPs have significant antifungal activity against Aspergillus nidulans, Aspergillus flavus, Rhizopus stolonifera, and T. harzianum (Gunalan et al., 2012). Dimkpa et al. (2013) reported that ZnO-NPs are efficient antifungally against F. graminearum. Furthermore, Hamza et al. (2016) found that TiO 2 -NPs have fungicidal properties against Cercospora beticola. ...
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With a focus on plant tolerance to environmental challenges, nanotechnology has emerged as a potent instrument for assisting crops and boosting agricultural production in the face of a growing worldwide population. Nanoparticles (NPs) and plant systems may interact molecularly to change stress response, growth, and development. NPs may feed nutrients to plants, prevent plant diseases and pathogens, and detect and monitor trace components in soil by absorbing their signals. More excellent knowledge of the processes of NPs that help plants survive various stressors would aid in creating more long-term strategies to combat these challenges. Despite the many studies on NPs’ use in agriculture, we reviewed the various types of NPs and their anticipated molecular and metabolic effects upon entering plant cells. In addition, we discussed different applications of NPs against all environmental stresses. Lastly, we introduced agricultural NPs’ risks, difficulties, and prospects.
... Whether nanoparticles maintain their integrity within the plant depends on their specific type and the in planta environment. 220,221 These transformations affect their movement within the plant, their potential toxicity, and their availability to the plant's biological systems. 222 Nanoparticles can accumulate in different tissues such as leaves, stems, and roots, with accumulation influenced largely by surface charge potential and, to a lesser extent, by size and tissue conditions. ...
Article
This critical review comprehensively analyses nano-sized metal oxide fertilizers (NMOFs) and their transformative potential in sustainable agriculture. It examines the characteristics and benefits of different NMOFs, such as zinc, copper, iron, magnesium, manganese, nickel, calcium, titanium, cerium, and silicon oxide nanoparticles. NMOFs offer unique advantages such as increased reactivity, controlled-release mechanisms, and targeted nutrient delivery to address micronutrient deficiencies, enhance crop resilience, and improve nutrient efficiency. The review underscores the essential role of micronutrients in plant metabolism, crop growth, and ecosystem health, highlighting their importance alongside macronutrients. NMOFs present significant benefits over traditional fertilizers, including enhanced plant uptake, reduced nutrient losses, and decreased environmental impact. However, the review also critically examines potential risks associated with NMOFs, such as nanoparticle toxicity and environmental persistence. A comparative analysis of different metal types used in nanofertilizers is provided, detailing their primary advantages and potential drawbacks. The review emphasizes the need for cautious management of NMOFs to ensure their safe and effective use in agriculture. It calls for comprehensive research to understand the long-term effects of NMOFs on plant health, soil ecosystems, and human health. By integrating insights from material science, plant biology, and environmental science, this review offers a holistic perspective on the potential of NMOFs to address global food security challenges amid resource constraints and climate change. The study concludes by outlining future research directions and advocating for interdisciplinary collaboration to advance sustainable agricultural practices and optimize the benefits of NMOFs.
... For example, zinc oxide, silver oxide nanoparticles had been explored as effective slow-release nanofertilizers, transport carriers, and bacteriostatic agents to provide plants with essential nutrients and inhibit pathogens, thus promoting plant growth and increasing crop yields (Elhaj Baddar and Unrine, 2018;Sun et al., 2018;Shireen Akhter Jahan et al., 2024). The application of nanoparticles to soil can influence its physical and chemical properties, the metabolic richness of plant roots, and the activity of the rhizosphere microbial community (Dimkpa et al., 2013;Sarma et al., 2024). Furthermore, the physical and chemical characteristics of soil, including texture, organic matter content, and pH level, inherently influence the migration and morphology of nanoparticles within the soil, which impact the bioavailability of nanoparticles (Cornelis et al., 2014;Reith and Cornelis, 2017;Goḿez-Sagasti et al., 2019). ...
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With the growth of the global population and the increasing scarcity of resources, the sustainability and efficiency improvement of agricultural production have become urgent needs. The rapid development of nanotechnology provides new solutions to this challenge, especially the application of nanoparticles in agriculture, which is gradually demonstrating its unique advantages and broad prospects. Nonetheless, various nanoparticles can influence plant growth in diverse manners, often through distinct mechanisms of action. Beyond their direct effects on the plant itself, they frequently alter the physicochemical properties of the soil and modulate the structure of microbial communities in the rhizosphere. This review focuses intently on the diverse methods through which nanoparticles can modulate plant growth, delving deeply into the interactions between nanoparticles and plants, as well as nanoparticles with soil and microbial communities. The aim is to offer a comprehensive reference for the utilization of functionalized nanoparticles in the agricultural sector.
... Further, particle size of ZnO-NPs also plays an important role in their dissolution in the soil. For instance, ZnO-NPs of a smaller size dissolved quickly, but their transformation and destiny are the same as those of the larger particles (Dimkpa et al. 2013). Further, soil acidity and alkalinity also affect the dissolution of ZnO-NPs. ...
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Heavy metal (HM) toxicity is a serious concern across the globe owing to their harmful impacts on plants, animals, and humans. Zinc oxide nanoparticles (ZnO-NPs) have gained appreciable attention in mitigating the adverse effects of abiotic stresses. The exogenous application of ZnO-NPs induces tolerance against HMs by improving plant physiological, metabolic, and molecular responses. They also interact with potential osmolytes and phyto-hormones to regulate the plant performance under HM stress. Moreover, ZnO-NPs also work synergistically with microbes and gene expression which helps to withstand HM toxicity. Additionally, ZnO-NPs also restrict the uptake and accumulation of HMs in plants which improves the plant performance. This review highlights the promising role of ZnO-NPs in mitigating the adverse impacts of HMs in plants. In this review, we explained the different mechanisms mediated by ZnO-NPs to counter the toxic effects of HMs. We also discussed the interactions of ZnO-NPs with osmolytes, phytohormones, and microbes in mitigating the toxic effects of HMs in plants. This review will help to learn more about the role of ZnO-NPs to mitigate HM toxicity in plants. Therefore, it will provide new insights to ensure sustainable and safer production with ZnO-NPs in HM-polluted soils.
... Regardless, for instance, in the related agriculture field, studies have shown that zinc oxide nanoparticles (ZnONPs) in various forms, such as zinc phosphate, exhibit maximal absorption in the roots and shoots of Z. mays when exposed hydroponically, likely because of increased dissolution in the rhizosphere, enhanced plant uptake, or efficient ionic zinc translocation [30]. Similar speciation of Zn accumulation has been observed in wheat grown in soil environments [31]. Still, ZnONPs have become one of the most preferred metal oxide nanoparticles in biological applications due to their high biocompatibility, low cost, and low toxicity [32]. ...
Article
The global food crisis is exacerbated by various challenges, including agricultural restrictions and environmental stresses, necessitating innovative approaches to enhance crop development and productivity. One promising technique is seed priming with iron oxide nanoparticles (FeNPs), which has shown significant potential in improving seed germination, crop growth, and stress resistance. This mini-review explores the synthesis, application, and physiological impacts of FeNPs in agriculture, emphasizing their role in addressing iron deficiency in plants and promoting robust plant development under challenging environmental conditions. Despite their benefits, the practical use of FeNPs faces critical challenges, notably nanoparticle agglomeration in biological media, which can diminish their effectiveness and lead to phytotoxicity. This review highlights advanced surface modification strategies, including the use of biocompatible polymers like chitosan and silica encapsulation, to enhance the colloidal stability, reduce agglomeration, and ensure the safe delivery of FeNPs. It discusses the mechanisms by which these modifications improve nanoparticle dispersion and interaction with plant systems, thereby optimizing their agronomic benefits. The review concludes with insights into the future directions of nanoparticle use in seed priming, particularly focusing on the implications of nanoparticle physicochemical properties on their agronomic efficacy and environmental safety.
... Although there are many reports on the effects of NPs in vegetables and field crops as well as on their microbiological activities [51][52][53][54][55], there are limited studies investigating their effects in berries, especially on boysenberry fruits. In this study, it was aimed to determine the effectiveness of some nanomaterials (SiNP, FeNP, AgNP) on the morphological and physiological properties of boysenberry plant grown under in vitro culture conditions and salinity stress (15 and 35 mM NaCl). ...
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Salinity, one of the most important abiotic stress factors, affects plant growth and limits agricultural productivity. In the study, the effects of iron (FeNP; 0.025 and 0.05 mM), silver (AgNP; 0,2 ve 0,4 mg L-1) and silicon dioxide (SiNP;7,5 ve 15 mg L-1) nanoparticles on morphological and physiological parameters of in vitro blackberry plants grown under salinity stress (NaCl; 15 mM ve 35 mM) were investigated. According to our study results, it was determined that higher values obtained from SiNP application in terms of shoot development parameters, FeNP application found more succesfull for root development, AgNP application was effective in SPAD, leaf relative water content (LRWC) and relative growth rate (RGR), and FeNP application was increased superoxide dismutase (SOD) and catalase (CAT) enzyme activities. Salt stress was significantly affected the root development, SPAD value, LRWC and RGR, SOD and CAT enzyme activities. As a result, under salt stress conditions, SiNP, FeNP and AgNP applications can significantly reduce the negative effects of stress and promote vegetative development of the plant compared to control conditions.
... The bioaccumulation of NPs in edible plant tissues holds great importance, due to its implications for plant performance and food safety. The scientific community has increasingly focused on understanding the fate (including uptake, transport, and biotransformation) and phytotoxicity of Cu-based nanopesticides in crops (Dimkpa et al., 2013;Pullagurala et al., 2018;Tripathi et al., 2017;Wang et al., 2012;Zhang et al., 2018aZhang et al., , 2018b. Various studies have explored the impact of NPs on plants, revealing both positive (Hussain et al., 2018;Rossi et al., 2019) and adverse consequences (Rizwan et al., 2017;Xiong et al., 2017). ...
Article
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Copper-based nanoparticles (NPs) are gradually being introduced as sustainable agricultural nanopesticides. However, the effects of NPs on plants requires carefully evaluation to ensure their safe utilization. In this study, leaves of 2-week-old lettuce (Lactuca sativa L.) were exposed to copper oxide nanoparticles (CuO-NPs, 0 [CK], 100 [T1], and 1000 [T2] mg/L) for 15 days. A significant Cu accumulation (up to 1966 mg/kg) was detected in lettuce leaves. The metabolomics revealed a total of 474 metabolites in lettuce leaves, and clear differences were observed in the metabolite profiles of control and CuO-NPs treated leaves. Generally, phenolic acids and alkaloids, which are important antioxidants, were significantly increased (1.26–4.53 folds) under foliar exposure to NPs; meanwhile, all the significantly affected flavonoids were down-regulated after CuO-NP exposure, indicating these flavonoids were consumed under oxidative stress. Succinic and citric acids, which are key components of the tricarboxylic acid cycle, were especially increased under T2, suggesting the energy and carbohydrate metabolisms were enhanced under high-concentration CuO-NP treatment. There was also both up- and down-regulation of fatty acids, suggesting cell membrane fluidity and function responded to CuO-NPs. Galactinol, which is related to galactose metabolism, and xanthosine, which is crucial in purine and caffeine metabolism, were down-regulated under T2, indicating decreased stress resistance and disturbed nucleotide metabolism under the high CuO-NP dose. Moreover, the differentially accumulated metabolites were significantly associated with plant growth and its antioxidant ability. Future work should focus on controlling the overuse or excessive release of NPs into agricultural ecosystems to limit their adverse effects.
... Genus-level clustering analysis showed that the composition of the epiphytic microbial community changed significantly under different concentrations of ZnO NPs, suggesting that ZnO NPs have a selective effect on epiphytic bacteria and fungi. This is consistent with previous studies that metal nanoparticles can affect the composition and abundance of microbial communities, potentially related to the antimicrobial properties of nanoparticles [68]. Similarly, the varying abundance of specific taxa suggests that ZnO NPs may exert selective pressure, favoring certain epiphytic microorganisms to become dominant [69]. ...
Article
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Background Nanotechnology holds revolutionary potential in the field of agriculture, with zinc oxide nanoparticles (ZnO NPs) demonstrating advantages in promoting crop growth. Enhanced photosynthetic efficiency is closely linked to improved vigor and superior quality in tea plants, complemented by the beneficial role of phyllosphere microorganisms in maintaining plant health. However, the effects of ZnO NPs on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms have not been fully investigated. Results This study investigated the photosynthetic physiological parameters of tea plants under the influence of ZnO NPs, the content of key photosynthetic enzymes such as RubisCO, chlorophyll content, chlorophyll fluorescence parameters, transcriptomic and extensive targeted metabolomic profiles of leaves and new shoots, mineral element composition in these tissues, and the epiphytic and endophytic microbial communities within the phyllosphere. The results indicated that ZnO NPs could enhance the photosynthesis of tea plants, upregulate the expression of some genes related to photosynthesis, increase the accumulation of photosynthetic products, promote the development of new shoots, and alter the content of various mineral elements in the leaves and new shoots of tea plants. Furthermore, the application of ZnO NPs was observed to favorably influence the microbial community structure within the phyllosphere of tea plants. This shift in microbial community dynamics suggests a potential for ZnO NPs to contribute to plant health and productivity by modulating the phyllosphere microbiome. Conclusion This study demonstrates that ZnO NPs have a positive impact on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms, which can improve the growth condition of tea plants. These findings provide new scientific evidence for the application of ZnO NPs in sustainable agricultural development and contribute to advancing research in nanobiotechnology aimed at enhancing crop yield and quality. Graphical Abstract
... Further, ZnO-NPs with positive charge can absorb negatively charged humic acid under lower soil pH, leading to their aggregation [70]. The size of NPs also affects their dissolution; for instance, small-sized NPs have quick dissolution compared to large-sized NPs [71]. In addition, soil acidity and alkalinity also affect the dissolution of ZnO-NPs; for example, ZnO-NPs are more quickly absorbed in acidic soils than in alkaline ones [72]. ...
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Cadmium (Cd), as the most prevalent heavy metal contaminant poses serious risks to plants, humans, and the environment. The ubiquity of this toxic metal is continuously increasing due to the rapid discharge of industrial and mining effluents and the excessive use of chemical fertilizers. Nanoparticles (NPs) have emerged as a novel strategy to alleviate Cd toxicity. Zinc oxide nanoparticles (ZnO-NPs) have become the most important NPs used to mitigate the toxicity of abiotic stresses and improve crop productivity. The plants quickly absorb Cd, which subsequently disrupts plant physiological and biochemical processes and increases the production of reactive oxygen species (ROS), which causes the oxidation of cellular structures and significant growth losses. Besides this, Cd toxicity also disrupts leaf osmotic pressure, nutrient uptake, membrane stability, chlorophyll synthesis, and enzyme activities, leading to a serious reduction in growth and biomass productivity. Though plants possess an excellent defense mechanism to counteract Cd toxicity, this is not enough to counter higher concentrations of Cd toxicity. Applying Zn-NPs has proven to have significant potential in mitigating the toxic effects of Cd. ZnO-NPs improve chlorophyll synthesis, photosynthetic efficiency, membrane stability, nutrient uptake, and gene expression, which can help to counter toxic effects of Cd stress. Additionally, ZnO-NPs also help to reduce Cd absorption and accumulation in plants, and the complex relationship between ZnO-NPs, osmolytes, hormones, and secondary metabolites plays an important role in Cd tolerance. Thus, this review concentrates on exploring the diverse mechanisms by which ZnO nanoparticles can alleviate Cd toxicity in plants. In the end, this review has identified various research gaps that need addressing to ensure the promising future of ZnO-NPs in mitigating Cd toxicity. The findings of this review contribute to gaining a deeper understanding of the role of ZnO-NPs in combating Cd toxicity to promote safer and sustainable crop production by remediating Cd-polluted soils. This also allows for the development of eco-friendly approaches to remediate Cd-polluted soils to improve soil fertility and environmental quality.
... As compared to the plant inoculated on MS media with GO fortifcation, the number of leaves and roots reached their maximum value at T1 and T4, respectively. Tese outcomes are consistent with those of Dimkpa et al. [40] who found that GO nanoparticles have the ability to activate metabolic pathways and produce active constituents for plant metabolism. Similarly, Guo et al. [41] observed that quinoa seedlings with diferent GO concentrations showed an increase in shoot/root growth. ...
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Stevia rebaudiana Bert. is commonly known as candy leaf, sugar leaf, or sweet leaf. It is a natural sweetener that has low calories and is used as a substitute for sucrose. The objective of this research is to evaluate the effects of graphene oxide (GO) on the growth, biochemical activities, and stevioside and rebaudioside A production of Stevia in in vitro-raised plantlets. For this, green nanomaterials of GO (0, 2, 4, 6, 8, and 10 mgL⁻¹) were applied to the in vitro plants to enhance its sweetness by triggering the production of stevioside and rebaudioside A and other growth and biochemical parameters. It was observed that all the growth parameters of Stevia plants significantly increased with all GO treatments tested. Total chlorophyll and protein contents were increased (1.85- and 2.65-fold increase from the control) by applying 8 mgL⁻¹ of GO to the MS medium. The maximum value (4 mg·g⁻¹ of protein) of peroxidase activity (POD) was observed by applying 4 mgL⁻¹ of GO, 28.92-fold increase from the control. In comparison, superoxide dismutase activity (SOD) (0.4 mg·g⁻¹ protein) was observed with 10 mgL⁻¹ of GO (1.56-fold increase from the control). Stevioside (12.9 and 8.9 mg·g⁻¹ DW) and rebaudioside A (3.2 and 0.81 mg·g⁻¹ DW) were observed only at 6 and 8 mg·L⁻¹ treatment of graphene oxide. According to the findings, using graphene oxide (GO) had a significant impact on the growth, biochemical activities, and steviol glycoside production in Stevia. This shows that GO has the potential to be a valuable enhancer of sweetness and overall Stevia leaf quality, providing great prospects for the development of low-calorie natural sweeteners.
... Concerns include the toxicity of nanoparticles to non-target organisms like soil microbes, plants, and animals, with studies indicating that certain nanoparticles can disrupt soil microbial communities and accumulate in the food chain. Their small size facilitates mobility, raising the risk of environmental contamination and unknown long-term effects (Tourinho et al., 2012;(Dimkpa et al., 2013;deMoraes et al., 2021). Human health concerns also arise from the potential for nanoparticles to enter the body through food consumption, with evidence of their ability to cross biological barriers. ...
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Sustainable food security and safety are major concerns on a global scale, especially in developed nations. Adverse agroclimatic conditions affect the largest agricultural-producing areas, which reduces the production of crops. Achieving sustainable food safety is challenging because of several factors, such as soil flooding/waterlogging, ultraviolet (UV) rays, acidic/sodic soil, hazardous ions, low and high temperatures, and nutritional imbalances. Plant growth-promoting rhizobacteria (PGPR) are widely employed in in-vitro conditions because they are widely recognized as a more environmentally and sustainably friendly approach to increasing crop yield in contaminated and fertile soil. Conversely, the use of nanoparticles (NPs) as an amendment in the soil has recently been proposed as an economical way to enhance the texture of the soil and improving agricultural yields. Nowadays, various research experiments have combined or individually applied with the PGPR and NPs for balancing soil elements and crop yield in response to control and adverse situations, with the expectation that both additives might perform well together. According to several research findings, interactive applications significantly increase sustainable crop yields more than PGPR or NPs alone. The present review summarized the functional and mechanistic basis of the interactive role of PGPR and NPs. However, this article focused on the potential of the research direction to realize the possible interaction of PGPR and NPs at a large scale in the upcoming years.
... The overall trend suggests that the shoot fresh weight decreased with increasing concentration, excluding the control and 6.0 mM SrO-NPs treatments. The findings of these results agree with Dimkpa et al. [32] on CuO and ZnO-NPs, Wang et al. (2014) on Ag-NPs, and Jiang et al. [33] on TiO 2 -NPs. The application of TiO 2 has been shown to decrease the fresh weight of wheat plant shoots in a dose-dependent manner. ...
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We explored the impact of strontium oxide nanoparticles (SrO-NPs), synthesized through a green method, on seedling growth of bread wheat in hydroponic systems. The wheat plants were exposed to SrO-NPs concentrations ranging from 0.5 mM to 8.0 mM. Various parameters, including shoot length (cm), shoot fresh weight (g), root number, root length (cm), root fresh weight (g), chlorophyll value (SPAD), cell membrane damage (%), hydrogen peroxide (H2O2) value (µmol/g), malondialdehyde (MDA) value (ng/µL), and enzymatic activities like ascorbate peroxidase (APX) activity (EU/g FW), peroxidase (POD) activity (EU/g FW), and superoxide dismutase (SOD) activity (U/g FW), were measured to assess the effects of SrO-NPs on the wheat plants in hydroponic conditions. The results showed that the SrO-NPs in different concentrations were significantly affected considering all traits. The highest values were obtained from the shoot length (20.77 cm; 0.5 mM), shoot fresh weight (0.184 g; 1 mM), root number (5.39; 8 mM), root length (19.69 cm; 0 mM), root fresh weight (0.142 g; 1 mM), SPAD (33.20; 4 mM), cell membrane damage (58.86%; 4 mM), H2O2 (829.95 µmol/g; 6 mM), MDA (0.66 ng/µl; 8 mM), APX (3.83 U/g FW; 6 mM), POD (70.27 U/g FW; 1.50 mM), and SOD (60.77 U/g FW; 8 mM). The data unequivocally supports the effectiveness of SrO-NPs application in promoting shoot and root development, chlorophyll levels, cellular tolerance, and the activation of enzymes in wheat plants.
... For example, ZnO NPs have exerted deleterious effects on Lepidium sativum growing in soils with higher cation exchange capacity ( Jośko and Oleszczuk, 2013). Likewise, Triticum aestivum growing in sandy soils showed increased toxicity toward ZnO and CuO NPs (Dimkpa et al., 2013). ...
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With the advancement of nanotechnology, the possible releases of nanoparticles have attracted significant consideration. In the present scenario, nanoparticles with new functional properties have been developed and continue to spread in almost every field of science, industry, biotechnology, medicine, agriculture, etc. Plants are intrinsic to ecosystems and plant–nanoparticles interaction is imperative for risk assessment. The entire acceptability and propensity to use nanotechnology in plants and the agricultural industry are constrained by the growing worries regarding bioavailability, transport, fate, inappropriate regulatory framework, and nanoparticle toxicity. A realistic approach is also lacking in the current research trends, which prevents a thorough understanding of risk assessment criteria and the nanoparticles’ toxicity toward plant, soil, and soil microbiome components following their release into the environment. A systematic evaluation of information on the influence of nanoparticles on plants and agricultural practices is required to improve our understanding of the effects of nanoparticles. Hence this book chapter focuses on the problems related to nano-toxicity and risk assessment factors on exposure of plants to nanoparticles. We also try to address the possible outcomes of the long-term and large-scale applications of nanomaterials in the field of social health and environmental concerns. Likewise, this chapter also suggests the future perspectives of the research direction for the safer use of nanoparticles in agriculture, which would lead us toward sustainable development.
... A comparable process for improved metal oxide NP dissolution by plants has been recommended and may be ascribed to siderophores and organic acids produced in rhizosphere soils (Dimkpa et al., 2013;Schwabe et al., 2015). The CuO and ZnO NPs' dissolution was augmented by the roots of wheat seedlings, which increased their concentrations from less than 0.3 to 1 and 0.6 to 2.2 mg/kg, respectively. ...
Chapter
Nanomaterials (NMs) are progressively employed in many sectors because of their novel properties; however, their introduction into the environment is of great interest to agriculture, food security, and health. Specifically, the NMs accumulation in soils could disrupt the soil and plant systems, probably posing a threat to crop yield. In this chapter, we have comprehensively discussed the toxic impacts of NMs on the soil ecosystem. It emphasizes how the potential widespread application of NPs in various fields may have negative effects on the soil ecosystem, such as changes in soil constituents and microflora (bacteria, nematodes, and earthworms), which eventually affect plant growth and development. It also emphasizes the genotoxic and cytotoxic impacts, influence on reactive oxygen species (ROS), and anti-oxidative activities in plants caused by NMs.
... However, low availability of Zn outside the root zone hinders plant nutrient uptake, and thereby majority of the agricultural soil is deficient in zinc (Lindsay, 1972). On the contrary, Zn and other NPs can easily accumulate in the delivery system of plants because of their ultra-small size and large surface area, and hence they have huge potential to improve the agricultural outcome (Raliya et al., 2018;Dimkpa et al., 2013;Shankar and Rhim, 2018). For example, zinc oxide (ZnO) NPs applied to Coffea arabica L. at a 10 ppm concentration increased the overall rate of photosynthesis by 55% and enhanced crop productivity/quality (Rossi et al., 2019). ...
... After the uptake by plants, nanomaterials are submitted to plant-mediated transformation [76]. It may concern changes in their structure and chemistry [77], formation of complexes with other elements [78], size modification [76]. Except uptake, transport and accumulation by plants, other issues should be included in the risk assessment of nanomaterials when introducing them to plant production sector, as life cycle analysis, bio-distribution and access to the food chain [79]. ...
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Background Bacterial contamination poses a high risk to the successful establishment and maintenance of plant tissue cultures. The aim of this study was to identify the isolates representing the frequent bacterial contaminants of Prunus rootstock tissue cultures and to determine the most effective concentration of nanomaterials for Curtobacterium sp. strain A7_M15 elimination without a negative impact on explants. Results Six Curtobacterium sp. strains were isolated and identified, and the whole-genome sequence was obtained for strain A7_M15. Two nanocomposites, reduced graphene oxide–copper–silver and silver–selenium, with the highest bactericidal activity were selected for elimination of Curtobacterium sp. contamination in Gisela 5 rootstock tissue cultures. Both nanocomposites showed 100% inhibition of bacterial plaque formation on culture medium at concentrations of 100, 200 and 400 mg L⁻¹ Ag (2 ×–8 × MBC). The quantity of Curtobacterium sp. on culture medium assessed using cfu enumeration was reduced by 92% and 74% in comparison to the positive control after treatment with reduced graphene oxide–silver–copper and silver–selenium at a concentration of 200 mg L⁻¹ Ag, respectively. None of the tested concentrations resulted in a decrease in Curtobacterium sp. quantity in explants. Curtobacterium sp. was detected in donor Gisela 5 plants, indicating an endophytic character of this bacterium. The dry weight of explants was not negatively affected by the application of nanocomposites regardless of concentration, and no detrimental effect of either nanocomposite at 100 or 200 mg L⁻¹ Ag on the surface covered by plants was observed. Conclusions Reduced graphene oxide–silver–copper and silver–selenium nanocomposites at 200 mg L⁻¹ Ag effectively limited the Curtobacterium sp. presence in micropropagated Prunus rootstock without causing phytotoxicity; therefore, those treatments could be offered as prevention with a high activity against bacterial contamination in plant tissue cultures. Graphical Abstract
... However, not all NPs play a protective role. ZnO and NiO NPs, while involved in ROS generation, leave an unresolved question about whether this generation is a consequence of the NPs themselves or the ions they release (Dimkpa et al., 2013). CuO NPs introduce further complexity, capable of instigating ROS production and potentially compromising membrane integrity (Wang et al., 2012). ...
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Nanotechnology offers promising applications in agriculture and horticulture. Specifically, nanofertilizers (NFs) have been investigated for enhancing growth, antioxidant defense, and productivity in fruit-bearing plants. These crops are vital for supplying essential nutrients and minerals to humans. However, their production and quality often face challenges from various stresses. Using nanoparticles (NPs) can potentially mitigate these challenges, thereby improving the productivity and quality of horticulture crops. NPs possess unique chemical and physical properties that benefit plant growth, development, and stress tolerance, making them valuable for fruit crop enhancement. This review highlights recent advancements in employing nanoparticles to bolster fruit crop growth. Various nanoparticle types, such as metal oxide, metallic, carbon-based, and organic NPs have been demonstrated positive effects on plant abiotic stress tolerance growth and fruit quality. They have been found to boost nutrient absorption, neutralize free radicals, and activate plant stress response pathways, leading to enhanced quality and yield of fruit. This review aims to elucidate significant insights into the utilization of nanoparticles as a promising strategy for bolstering the resilience of horticultural plants and safeguarding food security in the face of environmental alterations. Notwithstanding the favorable outcomes observed in ameliorating plant performance under abiotic stresses, the molecular mechanisms underlying the beneficial effects of NPs remain a subject of ongoing investigation. Further research is imperative to delve into the enduring implications , safety considerations, and optimal techniques for the application of NPs in horticultural plants.
... However, not all NPs play a protective role. ZnO and NiO NPs, while involved in ROS generation, leave an unresolved question about whether this generation is a consequence of the NPs themselves or the ions they release (Dimkpa et al., 2013). CuO NPs introduce further complexity, capable of instigating ROS production and potentially compromising membrane integrity (Wang et al., 2012). ...
... The dissolution of ZnO NPs in the soil is also depends on their particle size. For example, small-sized ZnO NPs showed quick dissolution, but their transformation and fate are not different to the larger particles (Dimkpa et al. 2013). In addition, the acidic and alkaline nature of soil influenced the dissolution of ZnO NPs. ...
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Due to sessile, plants are unable to avoid unfavorable environmental conditions which leads to inducing serious negative effects on plant growth, crop yield, and food safety. Instead, various approaches were employed to mitigate the phytotoxicity of these emerging contaminants from the soil–plant system. However, recent studies based on the exogenous application of ZnO NPs approve of their important positive potential for alleviating abiotic stress-induced phytotoxicity leads to ensuring global food security. In this review, we have comprehensively discussed the promising role of ZnO NPs as alone or in synergistic interactions with other plant growth regulators (PGRs) in the mitigation of various abiotic stresses, i.e., heavy metals (HMs), drought, salinity, cold and high temperatures from different crops. ZnO NPs have stress-alleviating effects by regulating various functionalities by improving plant growth and development. ZnO NPs are reported to improve plant growth by stimulating diverse alterations at morphological, physiological, biochemical, and ultrastructural levels under abiotic stress factors. We have explained the recent advances and pointed out research gaps in studies conducted in earlier years with future recommendations. Thus, in this review, we have also addressed the opportunities and challenges together with aims to uplift future studies toward effective applications of ZnO NPs in stress management.
... The increase in Zn content in grains would be beneficial for the nutritive value of rice. Dimkpa et al. reported that the root surfaces of plants grown with ZnO NPs were whiter than the control roots, suggesting coverage of the root surface by the ZnO NPs [60]. Therefore, the supply of ZnO NPs is linked to the increased accumulation of Zn in plants, which may be attributed to the higher availability of Zn in the form of NPs. ...
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In the present study, the effects of zinc oxide nanoparticles (ZnO NPs) on rice (Oryza sativa L. cv. PB1509) plant growth were assessed in hydroponics (5, 10, 25, 50 mg L−1) and soil microcosm (5, 10, 25 50 mg kg−1) experiments. In both hydroponics and soil experiments, Zinc (Zn) accumulation in plant parts (roots, shoots and grains) was found to increase with increasing doses of ZnO NPs. Grains accumulated 29 mg kg−1 Zn at 50 mg kg−1 ZnO NPs in the soil experiment. In the hydroponics experiment, growth and photosynthetic pigments were induced by ZnO NPs up to 10 mg L−1, while higher doses of 25 and 50 mg L−1 were toxic to plant growth. Antioxidant enzyme activities (SOD, CAT, APX and GPX) were mostly increased or unaffected by all ZnO NPs doses. In soil experiments, acid and alkaline phosphatase activities were increased at 5 mg kg−1 followed by a declining trend. However, a significant decrease occurred only at 50 mg kg−1. Urease activity in soil was significantly increased at all doses of ZnO NPs, while the activity of dehydrogenase did not show any significant change up to 25 mg kg−1. The length of plants and photosynthetic pigments did not show much toxicity except root length beyond 10 mg kg−1; however, the biomass of plants including grains was significantly lower than control beyond 5 mg kg−1 dose. The activity of antioxidant enzymes (GPX, APX and CAT) showed a significant increase at all doses of ZnO NPs. The DTPA extractable Zn concentration in the soil was significantly elevated with increasing exposure concentrations of ZnO NPs. Based on hydroponics and soil experiments, this study suggests a dose of up to 10 mg L−1 or 10 mg kg−1 would be an appropriate dose for augmenting the growth of rice plants and Zn accumulation, and this can be practically utilized for rice plants growing in submerged conditions. HIGHLIGHTS Rice plants exposed to ZnO nanoparticles in hydroponics and soil Zinc accumulation increased significantly in roots, shoots and grains Lower dose of ZnO NPs (10 mg/L or mg/kg) augmented plant growth Antioxidant enzymes showed a significant increase in activity in ZnO NPs treatment GRAPHICAL ABSTRACT
... Since we suggest the use of ZnO-NPs as the source of Zn we have tested the microbial community shift only at the recommended dose of Zn fertilizer. Many previous studies have reported the impact of nanomaterials on soil microbial ecology mainly with reference to their toxicity (Dimkpa et al., 2013;Khan et al., 2022a;Shah et al., 2022). When analyzed for differentially abundant genera, no such genera were observed. ...
Chapter
Soil nutrients play a crucial role in the growth and development of plants, influencing various physiological processes. Macronutrients such as nitrogen, phosphorus, and potassium, along with micronutrients including calcium, magnesium, and others, are essential for plant health. However, challenges in soil nutrient management necessitate innovative solutions, and nanotechnology offers promising avenues for addressing these challenges. This chapter examines the importance of soil nutrients for plant growth, highlights various macronutrients and micronutrients, and explores the role of nanotechnology in enhancing soil nutrient management. Specifically, it discusses the encapsulation of micro and macronutrients within polymer nanoparticles as a strategy to improve nutrient uptake efficiency and reduce environmental impacts. By leveraging nanotechnology, sustainable agricultural practices can be promoted, ensuring optimal plant nutrition while minimizing resource usage and environmental degradation.
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The relentless challenges phytopathogens pose in agricultural ecosystems demand innovative and sustainable solutions to ensure global food security. This chapter explores the potential of metallic nanoparticles as a novel approach to combat fungal phytopathogens and enhance plant health. It provides an in-depth analysis of various metallic nanoparticles, their properties, and mechanisms of action against phytopathogens. It reviews different application methods, discusses challenges and risks, and outlines future perspectives. Beginning with an overview of the current scenario of phytopathogen-induced crop losses, it then discusses the synthesis methods for metallic nanoparticles, emphasizing their tunable properties and diverse applications. Insights into the mechanisms underlying the antimicrobial activity of metallic nanoparticles against phytopathogens are given, highlighting their potential to disrupt crucial cellular processes. Furthermore, the multifaceted roles of metallic nanoparticles in plant defense mechanisms like enhancing plant innate immunity and fortifying resistance against diverse pathogens are explored. Finally, it discusses potential challenges and future directions addressing nanoparticle stability, long-term ecological effects, and regulatory considerations. This chapter serves as a comprehensive resource for researchers and policymakers, interested in applying metallic nanoparticles as a cutting-edge nanoweapon against fungal phytopathogens. Offering a holistic perspective on the subject contributes to the ongoing dialogue on sustainable agriculture and the development of innovative solutions to address the complex challenges associated with plant diseases.
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Due to the widespread use of engineered nanomaterials (ENMs) for soil remediation and nano‐enabled sustainable agriculture, there is a growing concern regarding the behavior and fate of ENMs released into soil systems in the presence of natural root exudates (REs). Herein, we investigate the influence of REs on the fate and ecological effect of ENMs from a comprehensive perspective. We summarize the key roles reported in the literature for REs in physical changes (e.g., adsorption, dispersion/aggregation), chemical changes (e.g., oxidation/redox reactions, and dissolution), and biotransformation of ENMs, which will further determine the ecological risk of ENMs in natural soil systems. Moreover, this review highlights the potential adverse effects of ENMs on different soil organisms (e.g., bacteria, plants, and eisenia foetida) in the presence of REs. The remaining unclear mechanisms (e.g., oxidative stress and DNA damage) of ENMs toxicity at the cellular level influenced by REs are reviewed and presented. Finally, the review concludes by addressing the current knowledge gaps and challenges in this field.
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The effects and mechanisms of zinc oxide nanoparticles (ZnO NPs) and their aging products, sulfidized (s-) ZnO NPs, on the carbon cycling in the legume rhizosphere are still unclear. We observed that, after 30 days of cultivation, in the rhizosphere soil of Medicago truncatula, under ZnO NP and s-ZnO NP treatments, the dissolved organic carbon (DOC) concentrations were significantly increased by 1.8- to 2.4-fold compared to Zn2+ treatments, although the soil organic matter (SOM) contents did not change significantly. Compared to Zn2+ additions, the additions of NPs significantly induced the production of root metabolites such as carboxylic acids and amino acids and also stimulated the growth of microbes involved in the degradations of plant-derived and recalcitrant SOM, such as bacteria genera RB41 and Bryobacter, and fungi genus Conocybe. The bacterial co-occurrence networks indicated that microbes associated with SOM formation and decomposition were significantly increased under NP treatments. The adsorption of NPs by roots, the generation of root metabolites (e.g., carboxylic acid and amino acid), and enrichment of key taxa (e.g., RB41 and Gaiella) were the major mechanisms by which ZnO NPs and s-ZnO NPs drove DOC release and SOM decomposition in the rhizosphere. These results provide new perspectives on the effect of ZnO NPs on agroecosystem functions in soil-plant systems.
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Based on previously published hydroponic plant, planktonic bacterial, and soil microbial community research, manufactured nanomaterial (MNM) environmental buildup could profoundly alter soil-based food crop quality and yield. However, thus far, no single study has at once examined the full implications, as no studies have involved growing plants to full maturity in MNM-contaminated field soil. We have done so for soybean, a major global commodity crop, using farm soil amended with two high-production metal oxide MNMs (nano-CeO2 and -ZnO). The results provide a clear, but unfortunate, view of what could arise over the long term: (i) for nano-ZnO, component metal was taken up and distributed throughout edible plant tissues; (ii) for nano-CeO2, plant growth and yield diminished, but also (iii) nitrogen fixation—a major ecosystem service of leguminous crops—was shut down at high nano-CeO2 concentration. Juxtaposed against widespread land application of wastewater treatment biosolids to food crops, these findings forewarn of agriculturally associated human and environmental risks from the accelerating use of MNMs.
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Abstract Metal oxide nanoparticles (NPs) are reported to impact plant growth in hydroponic systems. This study describes the impact of commercial CuO (\50 nm) and ZnO (\100 nm) NPs on wheat (Triticum aestivum) grown in a solid matrix, sand. The NPs contained both metallic and non-metallic impurities to different extents. Dynamic light scattering and atomic force microscopy (AFM) assessments confirmed aggregation of the NPs to submicron sizes. AFM showed transformation of ZnO NPs from initial rhomboid shapes in water to elongated rods in the aqueous phase of the sand matrix. Solubilization of metals occurred in the sand at similar rates from CuO or ZnO NPs as their bulk equivalents. Amendment of the sand with 500 mg Cu and Zn/kg sand from the NPs significantly (p = 0.05) reduced root growth, but only CuO NPs impaired shoot growth; growth reductions were less with the bulkamendments.DissolvedCufromCuONPs contributed to their phytotoxicity but Zn release did not account for the changes in plant growth. Bioaccumulation of Cu, mainly as CuO and Cu(I)–sulfur complexes, and Zn as Zn-phosphate was detected in the shoots of NP-challenged plants. Total Cu and Zn levels in shoot were similar whether NP or bulk materials were used. Oxidative stress in the NP-treated plants was evidenced by increased lipid peroxidation and oxidized glutathione in roots and decreased chlorophyll content in shoots; higher peroxidase and catalase activities were present in roots. These findings correlate with the NPs causing increased production of reactive oxygen species. The accumulation of Cu and Zn from
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Abstract This study investigated the dissolution-based toxicity mechanism for silver nanoparticles to Escherichia coli K12. The silver nanoparticles, synthesised in the vapour phase, are effective anti-bacterial agents against the Gram-negative bacterium, E. coli K12. The nanoparticles associate with the bacterial cell wall, appearing to interact with the outer and inner membranes, and then dissolve to release Ag(+) into the cell and affect a transcriptional response. The dissolution of these nanoparticles in a modified LB medium was measured by inductively coupled plasma mass spectrometry (ICP-MS) and has been shown to follow a simple first-order dissolution process proportional to the decreasing surface area of the nanoparticles. However, the resulting solution phase concentration of Ag(+), demonstrated by the ICP-MS data, is not sufficient to cause the observed effects, including inhibition of bacterial growth and the differential expression of Cu(+) stress response genes. These data indicate that dissolution at the cell membrane is the primary mechanism of action of silver nanoparticles, and the Ag(+) concentration released into the bulk solution phase has only limited anti-bacterial efficacy.
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The toxicity of commercially-available CuO and ZnO nanoparticles (NPs) to pathogenic bacteria was compared for a beneficial rhizosphere isolate, Pseudomonas chlororaphis O6. The NPs aggregated, released ions to different extents under the conditions used for bacterial exposure, and associated with bacterial cell surface. Bacterial surface charge was neutralized by NPs, dependent on pH. The CuO NPs were more toxic than the ZnO NPs. The negative surface charge on colloids of extracellular polymeric substances (EPS) was reduced by Cu ions but not by CuO NPs; the EPS protected cells from CuO NPs-toxicity. CuO NPs-toxicity was eliminated by a Cu ion chelator, suggesting that ion release was involved. Neither NPs released alkaline phosphatase from the cells' periplasm, indicating minimal outer membrane damage. Accumulation of intracellular reactive oxygen species was correlated with CuO NPs lethality. Environmental deposition of NPs could create niches for ion release, with impacts on susceptible soil microbes.
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This study was carried out to examine the phytotoxicity and oxidant stress by CuO and ZnO nanoparticles (NPs) in Cumumis sativus and the characterization of CuO and ZnO NP suspensions. We estimated the bioaccumulation of CuO and ZnO NP in plant, reactive oxygen species enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activities in plant tissue of root, and observed CuO and ZnO NPs with transmission electron microscopy. We found that the seedling biomass significantly decreased to 75% and 35% of that of control at 1,000 mg/L of CuO and ZnO NPs, respectively. The bioavailability and oxidant stress potential of plants exposed to metal oxide particles were dependent in the size, concentration, and species of the NPs. The median inhibition concentrations of CuO and ZnO NPs were 376 and 215 mg/L, respectively. In transmission electron microscopy, CuO and ZnO NPs greatly adhered to the root cell wall, and NPs were observed in the root cells. Another finding indicated that both CuO and ZnO NPs caused statistically significant increase in SOD, CAT, and POD activities and significant increase at 100 mg/L concentration levels. These results indicated that NPs alter both phytotoxicity and oxidative stress in plant assays. We further suggest that the oxidative stress markers appear to be a good predator of potential future toxicity of nanoparticles.
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The manufacture and multiple uses of zinc oxide (ZnO) nanoparticles (NPs) will represent a possible source of soil contamination. Little is known about how these NPs transport in soil and plants. In this research, the transport of Zn/ZnO NPs in sandy loam soil and the uptake by corn plants (Zea mays) was investigated. Results showed that ZnO NPs exhibit low mobility in a soil column at various ionic strengths. Elution curves suggest that some of the adsorbed ZnO NPs/Zn were released in the presence of chemical perturbations. The breakthrough of released Zn coincided with Fe and Al (indicator of soil colloids) suggesting that soil colloids may act as carriers of strongly adsorbed NPs. By using electron microprobe, Zn/ZnO NPs aggregates were visualized associate with soil clay minerals. The uptake (mg/kg) of Zn by one-month old corn plants varied from 69 to 409 in roots and from 100 to 350 in shoots, respectively, in soils contaminated with different concentrations of ZnO NPs (from 100 to 800 mg NPs/kg soil). Confocal microscope images showed that ZnO NPs aggregates penetrated the root epidermis and cortex through the apoplastic pathway; however, the presence of some NP aggregates in xylem vessels suggests that the aggregates passed the endodermis through the symplastic pathway.
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This report describes the synthesis and structural analysis of stable copper(II) cysteine complexes. Pale pink copper(II) cysteine complexes were synthesized in mole ratios of 1:2, 1:4, and 1:6 of copper(II):cysteine in ethanol. Infrared spectroscopy and X-ray absorption spectroscopy confirmed that copper(II) binding occurred via the thiol ligand of cysteine. XANES analysis showed that the oxidation state of copper remained as copper(II) and the local atomic geometry was similar in all of the cysteine complexes. The EXAFS data indicate that the copper(II) cysteine complexes are forming ring type structures with sulfur ligands from the cysteines acting as bridging ligands. X-ray diffraction revealed that the copper(II) cysteine complexes formed monoclinic cells with maximum crystallinity found in the 1:4 copper(II):cysteine complex.
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Fluorescence detection, in principle, permits the detection of the extended X-ray absorption fine structure (EXAFS) of more dilute atoms than can be obtained in absorption. To take advantage of this it is necessary, in practice, to eliminate the background that normally accompanies the fluorescence signal. We describe an X-ray filter assembly that accomplishes this purpose. The unique characteristic of the assembly is a slit system that minimizes the fluorescence background from the filter. The theory of the slit assembly is presented and is found to agree with measurements made on the Fe EXAFS of a dilute sample. The filter assembly has a better effective counting rate in this case than that of a crystal monochromator design.
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Graminaceous species release phytosiderophores for mobilization of iron (Fe) under Fe deficiency stress. In this study the possible risk that these root exudates might also enhance the uptake of toxic heavy metals from contaminated soils, was investigated. For this purpose wheat (Triticum aestivum L. cv. Piko) and sorghum (Sorghum bicolor (L.) Moench cv. E‐610), differing in release of phytosiderophores were precultured with roots in nylon bags in a sand culture system for low and high Fe nutritional status (+/‐Fe supply) for two weeks. After this preculture the nylon bags were brought in contact with a sewage sludge or heavy metal salt‐contaminated calcareous soil in a climate chamber for an additional 8 days growth period. At harvest the concentration of Fe, Zn, Ni and Cd in roots and shoots were analysed. The results clearly show that both plant species have mobilized Fe and heavy metals from the contaminated soil. Plants precultured for low Fe nutritional status had a higher uptake of Fe, Zn, Ni and Cd (up to 200%) than control plants with adequate Fe nutritional status. This enhanced acquisition of heavy metals was particularly expressed in wheat as an Fe efficient graminaceous species with corresponding higher release of phytosiderophores under Fe deficiency stress than sorghum.
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Little is known about transport of Zn from leaves to other plant organs. The present study tested a range of Zn forms applied foliarly for their suitability to provide adequate Zn nutrition to wheat (Triticum aestivum L.). Transport of65Zn applied either to leaves or to one side of the root system was also studied. Inorganic (ZnO, ZnSO4) and chelated sources of Zn (ZnEDTA, glycine-chelated Biomin Zn) applied foliarly provided sufficient Zn for vigorous growth. Zinc concentrations in roots and shoots were in the sufficiency range, except in the −Zn control. Foliar treatments with ZnSO4and chelated Zn forms resulted in shoot Zn concentrations in 7-week-old plants being about two-fold greater than those in plants supplied with Zn in the root environment or via foliar spray of ZnO. Adding surfactant to foliar sprays containing chelated forms of Zn did not cause negative growth effects, but surfactant added to ZnO or ZnSO4foliar sprays decreased shoot growth. Adding urea to the ZnO foliar spray had no effect on shoot growth. Foliarly-applied65Zn was translocated to leaves above and below the treated leaf as well as to the root tips. Stem girdling confirmed that65Zn transport toward lower leaves and roots was via the phloem. Split-root experiments showed intensive accumulation of65Zn in the stem and transport to all leaves as well as to the root tips in the non-labelled side of the root system. Foliar application of Zn in inorganic or organic form is equally suitable for providing adequate Zn nutrition to wheat. Phloem transport of Zn from leaves to roots was demonstrated.
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No.: 107 The thermodynamic properties ofZn5(OH)6(CO3)2 , hydrozincite, have been determined by performing solubility and d.s.c. measurements. The solubility constant in aqueous NaClO4media has been measured at temperatures ranging from 288.15 K to 338.15 K at constant ionic strength (I =1.00 mol· kg−1). Additionally, the dependence of the solubility constant on the ionic strength has been investigated up to I= 3.00 mol · kg−1NaClO4at T= 298.15 K. The standard molar heat capacity Cp, mofunction fromT= 318.15 K to T= 418.15 K, as well as the heat of decomposition of hydrozincite, have been obtained from d.s.c. measurements. All experimental results have been simultaneously evaluated by means of the optimization routine of ChemSage yielding an internally consistent set of thermodynamic data (T= 298.15 K): solubility constant log*Kps 00= (9.0 ± 0.1), standard molar Gibbs energy of formationΔfGmo {Zn5(OH)6(CO3)2 } = (−3164.6 ± 3.0)kJ · mol−1, standard molar enthalpy of formation ΔfHmo{Zn5(OH)6(CO3)2 } = (−3584 ± 15)kJ · mol−1, standard molar entropy Smo{Zn5(OH)6(CO3)2 } = (436 ± 50)J · mol−1· K−1and Cp,mo/(J · mol−1· K−1) = (119 ± 11) + (0.834 ± 0.033)T/K. A three-dimensional predominance diagram is introduced which allows a comprehensive thermodynamic interpretation of phase relations in(Zn2++ H2O + CO2) . The axes of this phase diagram correspond to the potential quantities: temperature, partial pressure of carbon dioxide and pH of the aqueous solution. Moreover, it is shown how the stoichiometric composition{n(CO3)/n(Zn)} of the solid compoundsZnCO3 and Zn5(OH)6(CO3)2can be checked by thermodynamically analysing the measured solubility data.
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With the increased use of engineered nanomaterials such as ZnO and CeO2 nanoparticles (NPs), these materials will inevitably be released into the environment, with unknown consequences. In addition, the potential storage of these NPs or their biotransformed products in edible/ reproductive organs of crop plants can enter them into the food chain, and the next plant generation. No reports thus far have addressed the entire life cycle of plants grown in NP-contaminated soil. Soybean (Glycine max) seeds were germinated and grown to full maturity in organic farm soil amended with either ZnO NPs at 500 mg/kg or CeO2 NPs at 1000 mg/kg. At harvest, synchrotron μ-XRF and μ-XANES analyses were performed on soybean tissues, including pods, to determine the forms of Ce and Zn in NP-treated plants. The X-ray absorption spectroscopy studies showed no presence of ZnO NPs within tissues. However, µ-XANES data showed O-bound Zn, in a form resembling Zn-citrate, which could be an important Zn complex in the soybean grains. On the other hand, the synchrotron μ-XANES results showed that Ce remained mostly as CeO2 NPs within the plant. The data also showed that a small percentage of Ce(IV), the oxidation state of Ce in CeO2 NPs, was biotransformed to Ce(III). To the authors' knowledge, this is the first report on the presence of CeO2 and Zn compounds in the reproductive/edible portion of the soybean plant grown in farm soil with CeO2 and ZnO NPs.
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To exploit the promised benefits of engineered nanomaterials, it is necessary to improve our knowledge of their bioavailability and toxicity. The interactions between engineered nanomaterials and vascular plants are of particular concern, as plants closely interact with soil, water, and the atmosphere, and constitute one of the main routes of exposure for higher species, i.e. accumulation through the food chain. A review of the current literature shows contradictory evidence on the phytotoxicity of engineered nanomaterials. The mechanisms by which engineered nanomaterials penetrate plants are not well understood, and further research on their interactions with vascular plants is required to enable the field of phytotoxicology to keep pace with that of nanotechnology, the rapid evolution of which constantly produces new materials and applications that accelerate the environmental release of nanomaterials.
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The phytotoxicity of bulk and nanoparticle Cu and Ag was directly compared. NP Ag reduced biomass and transpiration by 66-84% when compared with bulk Ag. The Ag ion concentration was 4.4-10-times greater in NP than bulk particle solutions. The Cu ion concentration was 1.4-4.4-times greater in bulk than NP amended solutions. Humic acid (50 mg/L) decreased the ion content of bulk Cu solution by 38-42% but increased ion Cu content of NP solutions by 1.4-2.9 times. Bulk and NP Cu were highly phytotoxic; growth and transpiration were reduced by 60-70% relative to untreated controls. NP Cu phytotoxicity was unaffected by solution type, but humic acid (50 mg/L) completely alleviated phytotoxicity caused by bulk Cu. The data demonstrate differential toxicity of Ag NP relative to bulk Ag. The finding that humic acid and solution chemistry differentially impact bulk and NP behavior highlights the importance of evaluating nanoparticles under environmentally relevant conditions.
Article
The impact of metal nanoparticles (NPs) on biological systems, especially plants, is still not well understood. The aim of this research was to determine the effects of zinc oxide (ZnO) NPs in velvet mesquite (Prosopis juliflora-velutina). Mesquite seedlings were grown for 15 days in hydroponics with ZnO NPs (10 nm) at concentrations varying from 500 to 4000 mg L(-1). Zinc concentrations in roots, stems and leaves were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Plant stress was examined by the specific activity of catalase (CAT) and ascorbate peroxidase (APOX); while the biotransformation of ZnO NPs and Zn distribution in tissues was determined by X-ray absorption spectroscopy (XAS) and micro X-ray fluorescence (μXRF), respectively. ICP-OES results showed that Zn concentrations in tissues (2102 ± 87, 1135 ± 56, and 628 ± 130 mg kg(-1) d wt in roots, stems, and leaves, respectively) were found at 2000 mg ZnO NPs L(-1). Stress tests showed that ZnO NPs increased CAT in roots, stems, and leaves, while APOX increased only in stems and leaves. XANES spectra demonstrated that ZnO NPs were not present in mesquite tissues, while Zn was found as Zn(II), resembling the spectra of Zn(NO(3))(2). The μXRF analysis confirmed the presence of Zn in the vascular system of roots and leaves in ZnO NP treated plants.
Article
Before commencing any nanotoxicological study, it is imperative to know the state of the nanoparticles to be used and in particular their size and size distribution in the appropriate test media is particularly important. Particles satisfying standards can be commercially purchased; however, these invariably cannot be used directly and need to be dispersed into the relevant biological media. Often such changes in the environment or ionic strength, or a change in the particle concentration, results in some aggregation or a shift in the particle size distribution. Such unexpected aggregation, dissolution or plating out, if unaccounted for, can have a significant effect on the available nanoparticle dose and on interpretation of any results obtained thereafter. Here, we demonstrate the application of characterisation instrumentation that sizes nanoparticles based on their Brownian motion in suspension. Unlike classical light-scattering techniques, the nanoparticle tracking and analysis (NTA) technique allows nanoparticles to be sized in suspension on a particle-by-particle basis allowing higher resolution and therefore better understanding of aggregation than ensemble methods (such as dynamic light scattering (DLS) and differential centrifugation sedimentation (DCS)). Results will be presented from gold (standard) nanoparticles in biologically relevant media that emphasise the importance of characterisation of the nanoparticle dispersion. It will be shown how the NTA technique can be extended to multi-parameter analysis, allowing for characterization of particle size and light scattering intensity on an individual basis. This multi-parameter measurement capability allows sub-populations of nanoparticles with varying characteristics to be resolved in a complex mixture. Changes in one or more of such properties can be followed both in real time and in situ.
Article
It has been shown previously (Treeby et al., 1989) that phytosiderophores, released by roots of iron deficient grasses (Gramineae), mobilize from calcareous soils not only iron (Fe) but also zinc (Zn), manganese (Mn) and copper (Cu). Mobilization of Fe may therefore be impaired by other micronutrient cations. This has been studied in both, model experiments with Fe hydroxide and with a calcareous soil (15% CaCO3, pH 8.6) amended with micronutrients as sulfate salts. Mobilization of Fe from Fe hydroxide by phytosiderophores (epi-3-hydroxymugineic acid) was not affected by the addition of CaCl2, MgSO4 and MnSO4, slightly inhibited by ZnSO4 and strongly inhibited by CuSO4. In a calcareous soil amended with increasing levels of ZnSO4, MnSO4 and CuSO4, mobilization of Fe by phytosiderophores remained uneffected by Zn and Mn amendments but was progressively impaired by increasing levels of Cu amendment, correlated with corresponding enhancement of Cu mobilization. High concentrations of ZnSO4 and MnSO4 and relatively high concentrations of CuSO4 were required for inhibition of Fe mobilization by phytosiderophores. It is therefore concluded that in most calcareous soils phytosiderophores efficiently mobilize Fe, and that phytosiderophores play an important role in Fe acquisition by grasses grown on calcareous soils.
Article
This work investigated how copper (Cu) phytotoxicity affected iron (Fe) nutrition and root elongation in hydroponically grown durum wheat (Triticum turgidum durum L., cv Acalou) in order to establish the critical level of Cu concentration in roots above which significant Cu phytotoxicity occurs. This was assessed at two levels of Fe supply (2 and 100μM). Severe symptoms of Cu phytotoxicity were observed at Cu2+ concentration above 1μM, i.e. interveinal chlorosis symptoms and global root growth alteration. Total root Cu concentration of about 100, 150 and 250–300mg kg−1 corresponded to 10%, 25% and 50% reduction in root elongation, respectively. Copper and Fe concentrations as well as amounts of Cu and Fe accumulated in shoots varied inversely which suggested an antagonism between Cu and Fe leading to Fe deficiency. In addition, the root-induced release of complexing compounds increased significantly with increasing Cu concentration in nutrient solution and was positively correlated with Cu uptake without significant difference between the two Fe treatments (high and low Fe supply). This work suggests that total root Cu concentration might be a simple, sensitive indicator of Cu rhizotoxicity. It also indicated that Cu phytotoxicity which may have resulted in Fe deficiency and significant increase in root-induced release of complexing compounds (presumably phytosiderophores) was independent of the level of Fe supply provided that the threshold values of phytotoxicity were based on the free Cu-ion concentration.
Article
Metal nanoparticles have many potential technological applications. Biological routes to the synthesis of these particles have been proposed including production by vascular plants, known as phytoextraction. While many studies have looked at metal uptake by plants, particularly with regard to phytoremediation and hyperaccumulation, few have distinguished between metal deposition and metal salt accumulation. This work describes the uptake of AgNO3, Na3Ag(S2O3)2, and Ag(NH3)2NO3 solutions by hydroponically grown Brassica juncea and the quantitative measurement of the conversion of these salts to silver metal nanoparticles. Using X-ray absorption near edge spectroscopy (XANES) to determine the metal speciation within the plants, combined with atomic absorption spectroscopy (AAS) for total Ag, the quantity of reduction of AgI to Ag0 is reported. Transmission electron microscopy (TEM) showed Ag particles of 2–35nm. The factors controlling the amount of silver accumulated are revealed. It is found that there is a limit on the amount of metal nanoparticles that may be deposited, of about 0.35wt.% Ag on a dry plant basis, and that higher levels of silver are obtained only by the concentration of metal salts within the plant, not by deposition of metal. The limit on metal nanoparticle accumulation, across a range of metals, is proposed to be controlled by the total reducing capacity of the plant for the reduction potential of the metal species and limited to reactions occurring at an electrochemical potential greater than 0V (verses the standard hydrogen electrode).
Article
Characterizing the state of nanoparticles (such as size, surface charge, and degree of agglomeration) in aqueous suspensions and understanding the parameters that affect this state are imperative for toxicity investigations. In this study, the role of important factors such as solution ionic strength, pH, and particle surface chemistry that control nanoparticle dispersion was examined. The size and zeta potential of four TiO2 and three quantum dot samples dispersed in different solutions (including one physiological medium) were characterized. For 15nm TiO2 dispersions, the increase of ionic strength from 0.001M to 0.1M led to a 50-fold increase in the hydrodynamic diameter, and the variation of pH resulted in significant change of particle surface charge and the hydrodynamic size. It was shown that both adsorbing multiply charged ions (e.g., pyrophosphate ions) onto the TiO2 nanoparticle surface and coating quantum dot nanocrystals with polymers (e.g., polyethylene glycol) suppressed agglomeration and stabilized the dispersions. DLVO theory was used to qualitatively understand nanoparticle dispersion stability. A methodology using different ultrasonication techniques (bath and probe) was developed to distinguish agglomerates from aggregates (strong bonds), and to estimate the extent of particle agglomeration. Probe ultrasonication performed better than bath ultrasonication in dispersing TiO2 agglomerates when the stabilizing agent sodium pyrophosphate was used. Commercially available Degussa P25 and in-house synthesized TiO2 nanoparticles were used to demonstrate identification of aggregated and agglomerated samples.
Article
The toxicity and fate of nanoparticles (NPs) have been reported to be highly dependent on the chemistry of the medium, and the effects of phosphate have tended to be ignored despite the wide existence of phosphate contamination in aqueous environments. In the present study the influence of phosphate on the dissolution and microstructural transformation of ZnO NPs was investigated. Phosphate at a low concentration rapidly and substantially reduced the release of Zn(2+) into aqueous solution. Synchrotron X-ray absorption spectroscopy and X-ray diffraction analysis reveal that interaction between ZnO NPs and phosphate induced the transformation of ZnO into zinc phosphate. Transmission electronic microscopy observation shows that the morphology of the particles changed from structurally uniform nanosized spherical to anomalous and porous material containing mixed amorphous and crystalline phases of ZnO and zinc phosphate in the presence of phosphate. To our knowledge, this is the first study in which the detailed process of phosphate-induced speciation and microstructural transformation of ZnO NPs has been analyzed. In view of the wide existence of phosphate contamination in water and its strong metal-complexation capability, phosphate-induced transformations may play an important role in the behaviors, fate, and toxicity of many other metal-based nanomaterials in the environment.
Article
Silver nanoparticles (Ag NPs) are widely used for their antimicrobial activity and consequently the particles will become environmental contaminants. This study evaluated in sand and soil matrices the toxicity of 10nm spherical Ag NPs (1 and 3 mg Ag/L) toward a beneficial soil bacterium, Pseudomonas chlororaphis O6. In sand, both NP doses resulted in loss in bacterial culturability whereas in a loam soil, no cell death was observed. Amendments of sand with clays (30% v/v kaolinite or bentonite) did not protect the bacterium when challenged with Ag NPs. However, culturability of the bacterium was maintained when the Ag NP-amended sand was mixed with soil pore water or humic acid. Imaging by atomic force microscopy revealed aggregation of single nanoparticles in water, and their embedding into background material when suspended in pore water and humic acids. Zeta potential measurements supported aggregation and surface charge modifications with pore water and humic acids. Measurement of soluble Ag in the microcosms and geochemical modeling to deduce the free ion concentration revealed bacterial culturability was governed by the predicted free Ag ion concentrations. Our study confirmed the importance of Ag NPs as a source of ions and illustrated that processes accounting for protection in soil against Ag NPs involved distinct NP- and ion-effects. Processes affecting NP bioactivity involved surface charge changes due to sorption of Ca²⁺ from the pore water leading to agglomeration and coating of the NPs with humic acid and other organic materials. Removal of bioactive ions included the formation of soluble Ag complexes with dissolved organic carbon and precipitation of Ag ions with chloride in pore water. We conclude that mitigation of toxicity of Ag NPs in soils towards a soil bacterium resides in several interactions that differentially involve protection from the Ag NPs or the ions they produce.
Article
Fluorescence detection, in principle, permits the detection of the extended x‐ray absorption fine structure (EXAFS) of more dilute atoms than can be obtained in absorption. To take advantage of this it is necessary, in practice, to eliminate the background that normally accompanies the fluorescence signal. We describe an x‐ray filter assembly that accomplishes this purpose. The unique characteristic of the assembly is a slit system that minimizes the fluorescence background from the filter. The theory of the slit assembly is presented and is found to agree with measurements made on the Fe EXAFS of a dilute sample. The filter assembly has a better effective counting rate in this case than that of a crystal monochromator design.
Article
Copper biogeochemistry is largely controlled by its bonding to natural organic matter (NOM) for reasons not well understood. Using XANES and EXAFS spectroscopy, along with supporting thermodynamic equilibrium calculations and structural and steric considerations, we show evidence at pH 4.5 and 5.5 for a five-membered Cu(malate)2-like ring chelate at 100–300 ppm Cu concentration, and a six-membered Cu(malonate))1–2-like ring chelate at higher concentration. A “structure fingerprint” is defined for the 5.0–7.0 Å⁻¹ EXAFS region which is indicative of the ring size and number (i.e., mono- vs. bis-chelate), and the distance and bonding of axial oxygens (Oax) perpendicular to the chelate plane formed by the four equatorial oxygens (Oeq) at 1.94 Å. The stronger malate-type chelate is a C4 dicarboxylate, and the weaker malonate-type chelate a C3 dicarboxylate. The malate-type chelate owes its superior binding strength to an –OH for –H substitution on the α carbon, thus offering additional binding possibilities. The two new model structures are consistent with the majority of carboxyl groups being clustered and α-OH substitutions common in NOM, as shown by recent infrared and NMR studies. The high affinity of NOM for Cu(II) is explained by the abundance and geometrical fit of the two types of structures to the size of the equatorial plane of Cu(II). The weaker binding abilities of functionalized aromatic rings also is explained, as malate-type and malonate-type structures are present only on aliphatic chains. For example, salicylate is a monocarboxylate which forms an unfavorable six-membered chelate, because the OH substitution is in the β position. Similarly, phthalate is a dicarboxylate forming a highly strained seven-membered chelate.
Article
Potential health and environmental effects of nanoparticles need to be thoroughly assessed before their widespread commercialization. Though there are few studies on cytotoxicity of nanoparticles on mammalian and human cell lines, there are hardly any reports on genotoxic and cytotoxic behavior of nanoparticles in plant cells. This study aims to investigate cytotoxic and genotoxic impacts of silver nanoparticles using root tip cells of Allium cepa as an indicator organism. A. cepa root tip cells were treated with four different concentrations (25, 20, 75, and 100 ppm) of engineered silver nanoparticles (below 100 nm size) dispersion, to study endpoints like mitotic index, distribution of cells in mitotic phases, different types of chromosomal aberrations, disturbed metaphase, sticky chromosome, cell wall disintegration, and breaks. For each concentration five sets of microscopic observations were carried out. No chromosomal aberration was observed in the control (untreated onion root tips) and the mitotic index (MI) value was 60.3%. With increasing concentration of the nanoparticles decrease in the mitotic index was noticed (60.30% to 27.62%). The different cytological effects including the chromosomal aberrations were studied in detail for the treated cells as well as control. We infer from this study that silver nanoparticles could penetrate plant system and may impair stages of cell division causing chromatin bridge, stickiness, disturbed metaphase, multiple chromosomal breaks and cell disintegration. The findings also suggest that plants as an important component of the ecosystems need to be included when evaluating the overall toxicological impact of the nanoparticles in the environment.
Article
This work reports on the toxicity of CuO nanoparticles (NPs) to maize (Zea mays L.) and their transport and redistribution in the plant. CuO NPs (100 mg L(-1)) had no effect on germination, but inhibited the growth of maize seedlings; in comparison the dissolved Cu(2+) ions and CuO bulk particles had no obvious effect on maize growth. CuO NPs were present in xylem sap as examined by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), showing that CuO NPs were transported from roots to shoots via xylem. Split-root experiments and high-resolution TEM observation further showed that CuO NPs could translocate from shoots back to roots via phloem. During this translocation, CuO NPs could be reduced from Cu (II) to Cu (I). To our knowledge, this is the first report of root-shoot-root redistribution of CuO NPs within maize. The current study provides direct evidence for the bioaccumulation and biotransformation of CuO NPs (20-40 nm) in maize, which has significant implications on the potential risk of NPs and food safety.
Article
CuO nanoparticles (NPs) exhibit dose-dependent toxicity to bacteria, whereas sublethal concentrations of these NPs change bacterial metabolism. Siderophores are model metabolites to study the impact of sublethal levels of metallic NPs on bacteria because they are involved in survival and interaction with other organisms and with metals. We report that a sublethal level of CuO NPs modify the production of the fluorescent siderophore pyoverdine (PVD) in a soil beneficial bacterium, Pseudomonas chlororaphis O6. The production of PVD was inhibited by CuO NPs but not by bulk CuO nor Cu ions at concentrations equivalent to those released from the NPs. The cell responses occurred despite the NPs forming near micrometer-sized aggregates. The CuO NPs reduced levels of periplasmic and secreted PVD and impaired expression from genes encoding proteins involved in PVD maturation in the periplasm and export through cell membranes. EDTA restored the fluorescence of PVD quenched by Cu ions but did not generate fluorescence with cultures of NP-challenged cells, confirming the absence of PVD. Conse