Effect of silver nanoparticles in crop plants Phaseolus radiatus and Sorghum bicolor: media effect on phytotoxicity

Silver nanorods induced oxidative stress and chromosomal aberrations in the Allium cepa model

The production of different size and shape silver nanoparticles (AgNPs) has increased considerably in recent years due to several commercial and biological applications. Here, rod-shaped AgNPs (SNRs) were prepared using the microwave-assisted method and characterised by ultraviolet-visible spectroscopy, and transmission electron microscopy analysis. The present study aims to investigate the cyto-genotoxic effect of various concentrations (5, 10, and 15 µM) of SNRs using Allium cepa model. As a result, concentration-dependent cyto-genotoxic effect of SNRs was observed through a decrease in the mitotic index, and an increase in the chromosomal aberrations such as chromosome break, disturbed metaphase, and anaphase bridge. To check the impact of Ag+ ions, 15 µM silver nitrate (AgNO3) was prepared and tested in all the assays. Furthermore, cell viability and different reactive oxygen species assays were performed to test the cytotoxicity evaluation of SNRs. The authors found that in all the tested assays, SNRs at high concentrations (15 µM) and AgNO3 (15 µM) were observed to cause maximal damage to the roots. Therefore, the current study implies that the cytotoxicity and genotoxicity of SNRs were dependent on the concentration of SNRs.

ZnO nanoparticles-induced oxidative stress in Chenopodium murale L, Zn uptake, and accumulation under hydroponic culture

To understand toxic effect of Zn oxide nanoparticles (ZnO NPs) on Chenopodium murale, 40-day-old plants were exposed to 10, 50, and 250 mg L^-1 of NPs using hydroponic system under controlled light and temperature conditions. Aboveground parts and roots were harvested 3 and 6 days after treatments and evaluated for some growth and biochemical indices. By increasing the concentration of ZnO NPs, the content of Zn increased in the roots more than the shoots. Our findings showed that all ZnO NPs treatments resulted in a decrease in growth, total chlorophyll content and soluble proteins, while the content of carotenoids, lipid peroxidation, leaf hydrogen peroxide (H₂O₂), and leaf electrolyte leakage increased significantly compared with the control. These changes, along with increased proline content and catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD) activities in the treated plants, suggest that all concentrations of ZnO NPs used in this study strongly induced oxidative stress. A decline in growth-related indicators can be considered as an indicator of ZnO NPs phytoxicity in C. murale. Based on the concentration of Zn dissolved in the solution, the effects of Zn released into the nutrient solution may be greatly involved in induction of toxicity and retardation of growth at least under our experimental conditions. The results of this study suggest that an important mechanism of ZnO NPs phytotoxicity may be the exacerbation of oxidative stress and damage to biomembranes.

Engineered ZnO and CuO Nanoparticles Ameliorate Morphological and Biochemical Response in Tissue Culture Regenerants of Candyleaf (Stevia rebaudiana)

Sustainable production of secondary metabolites in medicinal plants by artificial culturing on the industrial scale has gained worldwide importance. Engineered nanoparticles (ENPs) play a pivotal role in the elicitation of compounds of medicinal value. This investigation explores the influence of ZnO and CuO ENPs on in vitro roots formation, non-enzymatic antioxidant activities, and production of steviol glycosides (SGs) in regenerants of Candyleaf, Stevia rebaudiana. ENPs were applied in 0, 2, 20, 200, and 2000 mg/L of concentration in the MS medium containing plant shoots. The percentage of rooting induced was 91% and 94% by applying ZnO ENPs (2 mg/L) and CuO ENPs (20 mg/L), respectively. Moreover, at 2 mg/L of ZnO and 20 mg/L of CuO ENPs, the high performance liquid chromatography studies determined the significantly greatest content of SGs; rebaudioside A (4.42 and 4.44) and stevioside (1.28 and 1.96). Phytochemical studies including total flavonoid content, total phenolic content, and 2,2-diphenyl-1-picryl hydrazyl-free radical scavenging activity were calculated highest by the regenerants grown in 2 mg/L of ZnO and 20 mg/L of CuO ENPs dosage. Both ZnO and CuO ENPs at 200 mg/L and 2000 mg/L of concentration induced adverse effects on plant biomass, antioxidant activities, and SGs content up to 1.22 and 1.77 for rebaudioside A and 0.21 and 0.25 for stevioside. Hence, the biochemical and morphophysiological responses of Candyleaf were elicited as a defense against ZnO and CuO ENPs applied under threshold limit. This artificial biotechnological technique holds great promise for continued production of natural antioxidants on commercial scale and our study has further strengthened this impact.

Copper pre-exposure reduces AgNP bioavailability to wheat

Heavy metals in contaminated sites can affect plant responses to emerging contaminates such as engineered silver nanoparticles (AgNPs), but the underlying mechanisms are poorly understood. After 4-day exposure to 0-2.5 mg Cu L^-1 hydroponically, Cu concentrations in roots of wheat seedlings (Triticum aestivum L.) increased from 20 ± 3 to 325 ± 58 mg kg^-1. Meanwhile, the cell death in root tips, as measured by the uptake of Evans blue stain, increased 1.8-2.8 times in response to Cu exposure. Total thiol contents in roots (including glutathione, cysteine and phytochelatins), as measured by high performance liquid chromatography, increased 1.4 times upon low Cu exposure but decreased 2.2 times upon high Cu exposure. After those wheats were exposed to 10 mg L^-1 AgNPs for 8 h, the Ag influx rates decreased 1.3-3.9 times in Cu pre-exposed plants. Together, the cell death in root tips and thiol levels in roots could explain the decreased Ag influx rates of Cu pre-exposed plants. These findings indicate that the bioavailability of AgNPs without consideration of pre-existing metals could be over-estimated.

Uptake, translocation and ligand of silver in Lactuca sativa exposed to silver nanoparticles of different size, coatings and concentration

The broad use of silver nanoparticles (AgNPs) in daily life products enhances their possibilities to reach the environment. Therefore, it is important to understand the uptake, translocation and biotransformation in plants and the toxicological impacts derived from these biological processes. In this work, Lactuca sativa (lettuce) was exposed during 9 days to different coated (citrate, polyvinylpyrrolidone, polyethylene glycol) and sized (60, 75, 100 nm) AgNPs at different concentrations (1, 3, 5, 7, 10, 15 mg L-1). Total silver measurements in lettuce roots indicated that accumulation of AgNPs is influenced by size and concentration, but not by nanoparticle coating. On the other hand, nanosilver translocation to shoots was more pronounced for neutral charged and large sized NPs at higher NP concentrations. Single particle inductively coupled plasma mass spectrometry analysis, after an enzymatic digestion of lettuce tissues indicated the dissolution of some NPs. Ag K-edge X-ray absorption spectroscopy analysis corroborated the AgNPs dissolution due to the presence of less Ag-Ag bonds and appearance of Ag-O and/or Ag-S bonds in lettuce roots. Toxicological effects on lettuces were observed after exposure to nanosilver, especially for transpiration and stomatal conductance. These findings indicated that AgNPs can enter to edible plants, exerting toxicological effects on them.

Environmental impact of biogenic silver nanoparticles in soil and aquatic organisms

Synthetic silver nanoparticles (AgNPs) are being extensively used in our daily lives; however, they may also pose a risk to public health and environment. Nowadays, biological AgNPs are considered an excellent alternative, since their synthesis occurs by a green technology of low cost and easy scaling. However, studies with these biological nanomaterials (NM) are still limited. Thus, a more careful assessment of their industrial application, economic feasibility and ecotoxicological impacts is crucial. The aim of this study was to investigate the effects of different concentrations of mangrove fungus Aspergillus tubingensis AgNPs on the aerobic heterotrophs soil microorganisms, rice seeds (Oryza sativa) and zebrafish (Danio rerio). Biogenic AgNPs were less harmful for soil microbiota compared to AgNO₃. On rice seeds, the AgNPs displayed a dose-dependent inhibitory effect on germination and their subsequent growth and development. The percentage of inhibition of rice seed germination was 30, 69 and 80% for 0.01, 0.1 and 0.5 mM AgNPs, respectively. After 24 h of AgNPs exposition at a limit concentration of 0.2 mM, it did not induce mortality of the zebrafish D. rerio. Overall, A. tubingensis AgNPs can be considered as a suitable alternative to synthetic nanoparticles.

Phytotoxicity and upper localization of Ag@CoFe2O4 nanoparticles in wheat plants

Environmental concern related to Ag⁺ release from conventional AgNPs is expected to be prevented once contained into a magnetic core like magnetite or CoFe₂O₄. Accordingly, we obtained CoFe₂O₄ NPs by microwave-assisted synthesis, which AgNO₃ addition rendered Ag@CoFe₂O₄ NPs. NPs were characterized, and before exploring potential applications, we carried out 7-day wheat toxicity assays. Seed germination and seedling growth were used as toxicity endpoints and photosynthetic pigments and antioxidant enzymes as oxidative stress biomarkers. Total Fe, Co, and Ag determination was initial indicative of Ag@CoFe₂O₄ NPs uptake by plants. Then NPs localization in seedling tissues was sought by scanning electron microscopy (SEM) and darkfield hyperspectral imaging (DF-HSI). Not any silver ion (Ag⁺) was detected into the ferrite structure, but results only confirmed the presence of metallic silver (Ag⁰) adsorbed on the CoFe₂O₄ NPs surface. Agglomerates of Ag@CoFe₂O₄ NPs (~10 nm) were fivefold smaller than CoFe₂O₄ NPs, and ferrimagnetic properties of the CoFe₂O₄ NPs were conserved after the formation of the Ag@CoFe₂O₄ composite NPs. Seed germination was not affected by NPs, but root and shoot lengths of seedlings diminished 50% at 54.89 mg/kg and 168.18 mg/kg NPs, respectively. Nonetheless, hormesis was observed in roots of plants exposed to lower Ag@CoFe₂O₄ NPs treatments. Photosynthetic pigments and the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX) indicated oxidative damage by reactive oxygen species (ROS) generation. SEM suggested NPs presence in shoots and roots, whereas DF-HSI confirmed some Ag@CoFe₂O₄ NPs contained in shoots of wheat plants.

Silver nanoparticles and silver salt (AgNO3) elicits morphogenic and biochemical variations in callus cultures of sugarcane

The research work was arranged to check the role of AgNPs and silver ions on callus cells of sugarcane (Saccharum spp. cv CP-77,400). AgNPs were synthesized chemically and characterized by UV-Vis spectra, XRD and SEM. AgNPs and silver ions were applied in various concentrations (0, 20, 40, 60 ppm) to sugarcane calli and the induced stress was characterized by studying various morphological and biochemical parameters. AgNPs and silver ions treatments produced high levels of malondialdehyde, proline, proteins, TP and TF contents. Similarly, CAT, SOD and POX activity was also significant in both treatments. The lower concentration of AgNPs and silver ions (20 ppm) provided maximum intracellular GSH level. This work mainly showed effects of AgNPs and silver ions on sugarcane calli in terms of morphological aberrations and cell membrane damage due to severe oxidative stress and production of enhanced levels of enzymatic and non-enzymatic antioxidants as self-defence to tolerate oxidative stress by scavenging reactive oxygen species. These preliminary findings will provide the way to study ecotoxicity mechanism of the metal ions and NPs in medicine industry and in vitro toxicity research. Furthermore, silver ions alone and their chemically synthesised AgNPs can be used for various biomedical applications in future.

Microfluidic synthesis of methyl jasmonate-loaded PLGA nanocarriers as a new strategy to improve natural defenses in Vitis vinifera

The objective of the present work was to synthesize biopolymeric nanoparticles (NPs) entrapping the resistance-inductor methyl jasmonate (MeJA) to be employed as a novel and alternative strategy in integrated pest management. NPs were prepared by using a continuous flow microfluidic reactor that allows to precisely control some features that are crucial for applications such as size, polydispersion, morphology and reproducibility. Poly(lactic-co-glycolic acid) (PLGA), a biopolymer largely studied for its use in biological applications, was chosen for the production of NPs entrapping MeJA, a biotic endogenous elicitor able to trigger plant’s defense responses. The effect of different fluid-dynamic conditions, PLGA molecular weight and concentration on NP properties (dimensions, polydispersion, morphology, stability) was evaluated. DLS and SEM were employed to characterize the obtained NPs. MeJA-loaded PLGA NPs ranging from 40 to 70 nm were administered to Vitis vinifera cell cultures, in order to evaluate the biological response in terms of stilbene biosynthesis. HPLC investigations showed a faster response when the elicitor was administered by PLGA NPs in comparison with free MeJA. This result demonstrates that the encapsulation in PLGA NPs significantly promotes MeJA cell uptake and the activation of MeJA-induced responses.

Assessment of toxic interaction of nano zinc oxide and nano copper oxide on germination of Raphanus sativus seeds

Multiple applications of nanoparticles (NPs) could result in their potential release into agricultural systems and raised concerns about food safety. The NPs once released in the environment may interact with numerous pollutants, including other NPs. Present study assessed the impact of a single (CuO and ZnO NPs) and binary mixture (CuO+ZnO NPs) on the germination of Raphanus sativus seeds with a wide range of exposure concentration (0-1000 mg/L). Both the NPs have shown a deleterious effect on seeds at exposure concentration greater than 10 mg/L. Antagonistic interaction between effects of CuO and ZnO NPs on seeds was noticed for all the exposed concentrations. CuO NPs showed higher absorption capacity on the seedling surface than ZnO NPs. Internal uptake of Zn in ZnO NP-exposed seedlings was found to be greater than that due to CuO NP-exposed seedlings. Three different types of exposure adversely affected seed germination (reduction in root length, shoot length, and fresh weight). Reduction in growth parameters (length and weight) with concentration was compared using log-logistic dose-response model of "DRC" package of the "R" software, and EC₅₀ was determined. As per EC₅₀ values, the toxicity of CuO NPs was found to be maximum followed by CuO+ZnO NPs and then minimum for ZnO NPs. Seedlings accumulated Cu and Zn metals, and higher uptake was recorded for Zn (reported as mg/g seedling dry weight). The order of toxicity was found as CuO NPs > binary mixture (CuO+ZnO) NPs > ZnO NPs. Exposure concentration greater than 10 mg/L resulted in significant toxicity and uptake in germinated seedlings. These findings indicated that exposure of the mixture of NPs during germination might give different effects and thus, further attempts could prove quite beneficial to the literature.

Stimulatory Effect of Silver Nanoparticles on the Growth and Flowering of Potted Oriental Lilies

Nanoparticles exhibit unique biological activities and may serve as novel plant growth stimulators. This research consisted of a two-year pot experiment designed to find out if silver nanoparticles (AgNPs) might be used in the cultivation of Oriental lilies. In the first year, we evaluated the effects of various concentrations of AgNPs (0, 25, 50, 100, and 150 ppm) and their application methods (pre-planting bulb soaks, foliar sprays, and substrate drenches) on the growth and flowering of Lilium cv. Mona Lisa. In the second year, we evaluated the effects of soaking the bulbs of cv. Little John in the same concentration of AgNP solution on plant morphological features, leaf content of photosynthetic pigments, basic macronutrients, and complex biomolecules with the use of the Fourier-transform infrared spectroscopy (FTIR). Soaking the bulbs in a nanoparticle solution turned out to be the most effective strategy for growth and flowering promotion. AgNPs stimulated plant growth, as manifested by enhanced accumulation of leaf and bulb biomass and accelerated flowering. Moreover, plants treated with silver nanoparticles showed higher leaf greenness index, formed more flowers, and flowered longer. At 100 ppm AgNPs, the leaves accumulated the highest content of chlorophyll a, chlorophyll b, and carotenoids, and were the richest in potassium, calcium, and sulfur. The FTIR spectra did not show any changes in absorbance intensity and chemical composition in the leaves from AgNP-treated bulbs.

Silver nanoparticles reduced the invasiveness of redroot pigweed

The differences in the growth performance between invasive species and native species might paly a key role in the effective invasion. The extensive use of silver nanoparticles (AgNPs) has created the concern of their release into environment. Thus, the possible effects of AgNPs on the growth performance of invading agents are critical to better illustrate the underlying mechanisms for effective invasion. This study aimed to assess the impacts of AgNPs with different concentrations [200 and 400 mg kg (soil)^-1] and particle sizes (30 and 70 nm) on the growth performance and competitive ability of well known invasive Amaranthus retroflexus L. (redroot pigweed) and native A. tricolor L. (red amaranth). It was observed that the growth characteristics and supporting ability of redroot pigweed were significantly lower than those of amaranth. Results of the relative competitive intensity index and the relative dominance index also revealed that redroot pigweed exhibited lower competitive ability compared to red amaranth, especially under AgNPs. It can be assumed that the poor growth performance and competitive ability of redroot pigweed might prevent its invasiveness under AgNPs. The supporting ability, leaf photosynthetic area, leaf growing ability, leaf resource use efficiency and acquisition capability, and growth competitiveness of the two plant species were found to be significantly reduced under AgNPs. AgNPs with 30 nm at 400 mg kg (soil)^-1 triggered more toxicity on the supporting ability and growth competitiveness of the two plant species than AgNPs with 30 nm at 200 mg kg (soil)^-1. In addition, AgNPs with 30 nm imparted high toxicity on the leaf growing ability of red amaranth than AgNPs with 70 nm. However, the particle size of AgNPs did not address significant effects on the growth performance of redroot pigweed. Ag⁺ solution exhibited stronger toxicity on the supporting ability and leaf growing ability of the two plant species than AgNPs.

Temperature alters susceptibility of Picea abies seedlings to airborne pollutants: The case of CdO nanoparticles

Although plants are often exposed to atmospheric nanoparticles (NPs), the mechanism of NP deposition and their effects on physiology and metabolism, and particularly in combination with other stressors, are not yet understood. Exploring interactions between stressors is particularly important for understanding plant responses in urban environments where elevated temperatures can be associated with air pollution. Accordingly, 3-year-old spruce seedlings were exposed for 2 weeks to aerial cadmium oxide (CdO) NPs of environmentally relevant size (8-62 nm) and concentration (2 × 10⁵ cm^-3). While half the seedlings were initially acclimated to high temperature (35 °C) and vapour pressure deficit (VPD; 2.81 kPa), the second half of the plants were left under non-stressed conditions (20 °C, 0.58 kPa). Atomic absorption spectrometry was used to determine Cd content in needles, while gas and liquid chromatography was used to determine changes in primary and secondary metabolites. Photosynthesis-related processes were explored with gas-exchange and chlorophyll fluorescence systems. Our work supports the hypothesis that atmospheric CdO NPs penetrate into leaves but high temperature and VPD reduce such penetration due to stomatal closure. The hypothesis that atmospheric CdO NPs influences physiological and metabolic processes in plants was also confirmed. This impact strengthens with increasing time of exposure. Finally, we found evidence that plants acclimated to stress conditions have different sensitivity to CdO NPs compared to plants not so acclimated. These findings have important consequences for understanding impacts of global warming on plants and indicates that although the effects of elevated temperatures can be deleterious, this may limit other forms of plant stress associated with air pollution.

Phyllanthus emblica fruit extract stabilized biogenic silver nanoparticles as a growth promoter of wheat varieties by reducing ROS toxicity

The present study is focused on the biogenic synthesis of AgNPs (B-AgNPs) using fruit extract of Phyllanthus emblica L. and its effect (0, 5, 10, 25, 50 mg/L concentrations) on early seedling growth of two wheat varieties (HD-2967 and DBW-17). The prepared silver nanoparticles were characterized with several techniques such as UV-Vis spectroscopy, powder X-ray diffraction as well as high-resolution transmission electron microscopy. The capping of AgNPs by phytochemicals was confirmed by Fourier transforms infrared (FT-IR) spectroscopy. B-AgNPs, chemically synthesized AgNPs, chemically synthesized AgNPs+10% fruit extract and AgNO₃ salt were compared for phytotoxicity, based on growth parameters, ROS production, cytotoxicity assay and silver accumulation in two wheat varieties (HD-2967 and DBW-17). These effects were more pronounced in the variety HD-2967 over DBW-17 variety at 10 mg/L B-AgNPs exposure. Root cells viability of treated radicles was studied using Evans blue dye assay which suggest that 10 mg/L B-AgNPs was effective in promoting early seedling growth by decreasing ROS toxicity. Lower accumulation of Ag resulting in higher root cell viability than those of chemically synthesized AgNPs treated seedlings. The findings of the present study clearly indicate that phytochemicals capped AgNPs act as a growth promoter at lower concentrations by delivering a potent antioxidant during early seedling growth as compared to chemically synthesized AgNPs treated wheat seedlings.

Toxicological responses of Fe3O4 nanoparticles on Eichhornia crassipes and associated plant transportation

This work investigated the interaction of Fe₃O₄ nanoparticles (NPs) with a floating water plant (Eichhornia crassipes). The effects of Fe₃O₄ NPs on E. crassipes physiology and root morphology as well as the migration and transformation of Fe₃O₄ NPs in plant were studied emphatically. Fe₃O₄ NPs (200 mg/L) showed significant growth inhibition on E. crassipes roots and leaves after a 21-day exposure, while dissolved Fe³⁺ ions and Fe₃O₄ bulk particles had no obvious effect on E. crassipes growth. Scanning electron microscopy showed that the roots of E. crassipes were significantly damaged, the root tips became thin and the root epidermis began to peel off after Fe₃O₄ NPs exposure. In addition, there was disordered cell arrangement and a destroyed elongation zone of the root tips. The physiology of E. crassipes was also affected. In particular, after exposure to Fe₃O₄ NPs (200 mg/L), a distinct decrease in chlorophyll content and catalase activity and an increase of malondialdehyde (MDA) content could be seen. Transmission electron microscopy and energy dispersive spectroscopy revealed that Fe₃O₄ NPs were present in the root epidermis, intercellular space and protoplasts, as well as in the leaf cytoplasm and chloroplasts. Vulcanization in the leaves was also found through diffraction analysis, which may be due to the small number of absorbed nanoparticles, some of which still existed in the original form in the leaves while others were reduced to FeS through interactions with plant components during translocation. These findings are helpful for better understanding the fate of NPs in aquatic plants. Moreover, it is important to evaluate the water environment safety of NPs.

Prospects, challenges and need for regulation of nanotechnology with special reference to India

To meet the challenges of food security in a sustainable way, technological intervention in agriculture is of prime importance. With the existing conventional technologies supporting high yield, better crop production and protection, the emphasis is now on use of nanotechnology. Exploring new applications of nanotechnology has gained momentum in recent years and has shown acceptance in sectors like food, medicine, chemistry etc. As compared to other sectors, the accepted role in agriculture can still be considered on the marginal side in terms of nanotechnology application. Nanotechnology offers a potential to open large scope of novel application in the fields of biotechnology and agricultural industries due to unique physicochemical properties. Nanoparticles can be used in herbicides, nano-pesticide, nano-fertilizers, or genes, which target specific cellular organelles in plant to release their content. It can potentially play an instrumental role in minimizing the application losses of agrochemicals due to their more stable emulsion, higher coverage on leaf surface, precision application, etc. Understanding that the conventional and macro-technologies in agriculture do not ensure sustainable food security and environmentally safe methods; the researchers are now inclined for more précised nanotechnology based applications. There is still a huge untapped potential of nanomaterials to be used a future technology in agriculture which remains to be explored. Besides offering potential benefits, there are high concerns about the potential challenges associated with nanoparticles. To address the safety concerns about nanoparticles, it is important that a strong regulation system should be developed. Presently, very few countries have started focusing on keeping nanoregulation on their agenda. It is very important for agricultural and biodiverse country like India to set up norms of use nanoregulation and bring nanotechnology on the safe technology net.

Impacts of Silver Nanoparticles on Plants: A Focus on the Phytotoxicity and Underlying Mechanism

Nanotechnology was well developed during past decades and implemented in a broad range of industrial applications, which led to an inevitable release of nanomaterials into the environment and ecosystem. Silver nanoparticles (AgNPs) are one of the most commonly used nanomaterials in various fields, especially in the agricultural sector. Plants are the basic component of the ecosystem and the most important source of food for mankind; therefore, understanding the impacts of AgNPs on plant growth and development is crucial for the evaluation of potential environmental risks on food safety and human health imposed by AgNPs. The present review summarizes uptake, translocation, and accumulation of AgNPs in plants, and exemplifies the phytotoxicity of AgNPs on plants at morphological, physiological, cellular, and molecular levels. It also focuses on the current understanding of phytotoxicity mechanisms via which AgNPs exert their toxicity on plants. In addition, the tolerance mechanisms underlying survival strategy that plants adopt to cope with adverse effects of AgNPs are discussed.

Biochemical and physiological effects of copper compounds/nanoparticles on sugarcane (Saccharum officinarum)

The widespread use of copper based nanomaterials has been accompanied by an increasing interest in understanding their potential risks. It is essential to understand the effects of these nanoparticles on edible crops by performing long-term experiments at relevant exposure concentrations. Sugarcane is the source of 70% of the world's sugar supply and the widespread use of refined sugar and the consumption of raw sugarcane can provide a route for nanoparticles to enter the food supply. In order to evaluate the biochemical and physiological effects of copper nanoparticle exposure, sugarcane was grown for one year in soil amended with 20, 40, and 60 mg/kg of Kocide 3000 (a copper based fungicide), copper metal nanoparticles, micro-sized CuO, and CuCl₂. The results show that stress indicators such as catalase and ascorbic peroxidase enzymatic activity in the sugarcane plant were activated by all the copper based materials at different concentrations. Sugarcane plants exposed to nearly all copper treatments showed dosage dependent increases in copper concentrations in root tissues. Translocation of copper to aerial tissues was minimal, with copper concentrations not being significantly different from controls. In addition, Chlorophyll A content was higher in plants treated with Kocide 3000 at 20 and 60 mg/kg, μCuO at 20 mg/kg, and CuCl₂ at 20 and 60 mg/kg. To our knowledge, this is the first report on the effects of nano-copper compounds in sugarcane crop.

Size- and shape-dependent toxicity of silver nanomaterials in green alga Chlorococcum infusionum

Silver nanomaterials (AgNMs) of different shapes and sizes are potentially toxic to aquatic organisms. However, studies on the toxicity of AgNMs and on their shape-dependent effects on algae are scarce. The present study evaluated the effects of three AgNMs (silver nanospheres, AgNPs; silver nanowires, AgNWs; silver nanoplates, AgPLs) with different shapes coated with polyvinylpyrrolidone on the growth and photosynthetic performance of an alga, Chlorococcum infusionum. We used growth measurements and determined the photosynthetic parameters based on chlorophyll fluorescence transients in the algal cells exposed to different concentrations of the three AgNMs. The effective concentrations at 50% (EC₅₀) of AgNPs, AgNWs, and AgPLs were calculated to be 0.1, 0.045, and 0.021 mg/L, respectively. The results showed that the toxicity of AgNMs in C. infusionum was in the order, AgPLs (40 nm diameter) > AgNWs (21,000 nm length × 42 nm diameter) > AgNPs (57 nm diameter), based on the decrease in growth and three photosynthetic activities. We propose that the toxic potential of AgNMs is primarily dependent on their diameter and secondarily on their shape. Overall, this study provides, for the first time, a comparison of the growth and photosynthetic activities of C. infusionum exposed to AgNMs of three different shapes.

Various antibacterial mechanisms of biosynthesized copper oxide nanoparticles against soilborne Ralstonia solanacearum

The substantial antimicrobial efficacy of nanoparticles against phytopathogens has been extensively investigated for advanced agricultural applications. However, few reports have focused on soilborne pathogenic bacteria. The aim of this study was to obtain sustainably synthesized copper oxide nanoparticles (CuONPs) using papaya leaf extracts and investigate the bactericidal activity of these CuONPs against Ralstonia solanacearum, the cause of bacterial wilt, under laboratory and greenhouse conditions. The results showed that CuONPs possessed strong antibacterial activity and that all R. solanacearum were killed after exposure to 250 μg mL-1 CuONPs. CuONPs could interact with bacterial cells to prevent biofilm formation, reduce swarming motility and disturb ATP production. Ultrastructural observations by transmission electron microscopy (TEM) revealed that after interactions with CuONPs, bacterial cells suffered significantly from nanomechanical damage to the cytomembrane, accompanied by the absorption of multiple nanoparticles. In addition, molecular studies identified the downregulation mechanism of a series of genes involving pathogenesis and motility. The control efficiency of CuONPs in tobacco bacterial wilt disease management under greenhouse conditions was verified by root irrigation application, demonstrating that as-prepared CuONPs significantly reduced the disease occurrence and disease index. Our studies focused on developing biosynthesized nanoparticles as a biocompatible alternative for soilborne disease management.

Evaluation of some effects on plant metabolism through proteins and enzymes in transgenic and non-transgenic soybeans after cultivation with silver nanoparticles

To evaluate the effects of silver nanoparticles (AgNP) exposition, transgenic (through gene cp4EPSPS) and non-isogenic non-transgenic soybeans were cultivated in the presence or absence of AgNP or silver nitrate (AgNO3) at 50 mg/kg of silver. Physiological aspects of the plants including mass production and development of roots, proteomics such as protein amount and differential proteins, enzymes and lipid peroxidation were determined after exposition. The mass production of non-transgenic plants treated with AgNP or AgNO3 was decreased by 25 and 19%, respectively, on their mass based, while for transgenic soybean this effect was observed for AgNP cultivation only. Fifty-nine proteins were identified from the differentially abundant spots by two-dimensional difference gel electrophoresis and nano-electrospray ionization liquid chromatography coupled tandem mass spectrometry. Identified species as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), ATP synthase, superoxide dismutase (SOD), related to plant metabolism were less abundant for the cultivation with either AgNP and AgNO3 than the control. Finally, this work demonstrated significant correlation as evidenced by changes in lipid peroxidation content and catalase activity, which were a result of exposure to either AgNP or AgNO3 cultivations. Further, necrotic areas in the basal part of the stems and damage or chlorotic areas were found in the leaves. SIGNIFICANCE: Once nanoparticles have been employed for several applications in recent years and they can be released in the environmental matrices, this study highlights proteomic and enzymatic alterations in transgenic and non-transgenic soybeans, an important crop, after cultivation with silver nanoparticles. Such strategy employing proteomic and enzymatic approaches to evaluate soybeans exposed to silver nanoparticles has not yet been reported. Therefore, the results obtained in this study can expand the information concerning the effects of silver nanoparticles in soybean plants.

Uptake and Transformation of Silver Nanoparticles and Ions by Rice Plants Revealed by Dual Stable Isotope Tracing

Knowledge on the uptake and transformation of silver nanoparticles (AgNPs) and Ag⁺ ions by organisms is critical for understanding their toxicity. Herein, the differential uptake, transformation, and translocation of AgNPs and Ag⁺ ions in hydroponic rice ( Oryza sativa L.) is assessed in modified Hewitt (with Cl^- ions, HS(Cl)) and Hogland solutions (without Cl^- ions, HS) using dual stable isotope tracing (¹⁰⁷AgNO₃ and ¹⁰⁹AgNPs). After coexposure to ¹⁰⁷Ag⁺ ions and ¹⁰⁹AgNPs at 50 μg L^-1 (as Ag for both) for 14 days, a stimulatory effect was observed on root elongation (increased by 68.8 and 71.9% for HS(Cl) and HS, respectively). Most of the Ag⁺ ions (from ¹⁰⁷Ag⁺ ions and ¹⁰⁹AgNPs) were retained on the root surface, while the occurrence of AgNPs (from ¹⁰⁹AgNPs and ¹⁰⁷Ag⁺ ions) was observed in the root, suggesting the direct uptake of AgNPs and/or reduction of Ag⁺ ions. Higher fractions of Ag⁺ ions in the shoot suggest an in vivo oxidation of AgNPs. These results demonstrated the intertransformation between Ag⁺ ions and AgNPs and the role of AgNPs as carriers and sources of Ag⁺ ions in organisms, which is helpful for understanding the fate and toxicology of Ag.

Phytotoxic effect of silver nanoparticles on seed germination and growth of terrestrial plants

Silver nanoparticles (AgNP) exhibit size and concentration dependent toxicity to terrestrial plants, especially crops. AgNP exposure could decrease seed germination, inhibit seedling growth, affect mass and length of roots and shoots. The phytotoxic pathway has been partly understood. Silver (as element, ion or AgNP) accumulates in roots/leaves and triggers the defense mechanism at cellular and tissue levels, which alters metabolism, antioxidant activities and related proteomic expression. Botanical changes (either increase or decrease) in response to AgNP exposure include reactive oxygen species generation, superoxide dismutase activities, H₂O₂ level, total chlorophyll, proline, carotenoid, ascorbate and glutathione contents, etc. Such processes lead to abnormal morphological changes, suppression of photosynthesis and/or transpiration, and other symptoms. Although neutral or beneficial effects are also reported depending on plant species, adverse effects dominate in majority of the studies. More in depth research is needed to confidently draw any conclusions and to guide legislation and regulations.

Ag nanoparticles inhibit the growth of the bryophyte, Physcomitrella patens

The wide use of Ag nanoparticles (Ag NPs) as antimicrobial agents has resulted in a massive release of Ag NPs into environment, such as water and soil. As bryophytes live ubiquitously in water and soil, their tolerance and response to Ag NPs could be employed as an indicator for the harm of Ag NPs to the environment. Herein, we report the study on the physiological and biochemical responses of bryophytes to Ag NPs with different surface coatings at the gametophyte stages: protonema and leafy gametophyte, by using Physcomitrella patens as a model system. We found that Ag NPs, including AgNPs-B (Ag NPs without surface coating), AgNPs-PVP (Ag NPs coated with poly (N-vinyl-2-pyrrolidone)) and AgNPs-Cit (Ag NPs coated with citrate), were toxic to P. patens in terms of growth and development of the gametophyte. The toxicity was closely related to the concentration and surface coating of Ag NPs, and the growth stage of P. patens. The protonema was more sensitive to Ag NPs than the leafy gametophyte. Ag NPs inhibited the growth of the protonema following the trend of AgNPs-B > AgNPs-Cit > AgNPs-PVP. Ag NPs changed the thylakoid and chlorophyll contents, but did not affect the contents of essential elements in the protonema. At the leafy gametophyte stage, Ag NPs inhibited the growth of P. patens following a different order: AgNPs-Cit > AgNPs-B ≈ AgNPs-PVP. Ag NPs decreased the chlorophyll b content and disturbed the balance of some important essential elements in the leafy gametophytes. Both the dissolved fraction of Ag NPs and Ag NPs per se contributed to the toxicity. This study for the first time reveals the effects of Ag NPs on bryophytes at different growth stages, which calls for more attention to the nanoecotoxicology of Ag NPs.

Physiological, ultrastructural and proteomic responses of tobacco seedlings exposed to silver nanoparticles and silver nitrate

Since silver nanoparticles (AgNPs) are a dominant nanomaterial in consumer products, there is growing concern about their impact on the environment. Although numerous studies on the effects of AgNPs on living organisms have been conducted, the interaction of AgNPs with plants has not been fully clarified. To reveal the plant mechanisms activated after exposure to AgNPs and to differentiate between effects specific to nanoparticles and ionic silver, we investigated the physiological, ultrastructural and proteomic changes in seedlings of tobacco (Nicotiana tabacum) exposed to commercial AgNPs and ionic silver (AgNO3) from the seed stage. A higher Ag content was measured in seedlings exposed to AgNPs than in those exposed to the same concentration of AgNO3. However, the results on oxidative stress parameters obtained revealed that, in general, higher toxicity was recorded in AgNO3-treated seedlings than in those exposed to nanosilver. Ultrastructural analysis of root cells confirmed the presence of silver in the form of nanoparticles, which may explain the lower toxicity of AgNPs. However, the ultrastructural changes of chloroplasts as well as proteomic study showed that both AgNPs and AgNO3 can affect photosynthesis. Moreover, the majority of the proteins involved in the primary metabolism were up-regulated after both types of treatments, indicating that enhanced energy production, which can be used to reinforce defensive mechanisms, enables plants to cope with silver-induced toxicity.

Silver nanoparticles with different particle sizes enhance the allelopathic effects of Canada goldenrod on the seed germination and seedling development of lettuce

Allelopathic effects on the seed germination and seedling development of co-occurring native plant species (natives hereafter) are regarded as an important driver facilitating invasion of many invasive plant species (invaders hereafter). The release of silver nanoparticles (AgNPs) into the environment may affect the allelopathic effects of the invaders on the seed germination and seedling development of natives. This study aims to assess the allelopathic effects (using leaf extracts) of Canada goldenrod (Solidago canadensis L.) on the seed germination and seedling development of native lettuce (Lactuca sativa L.) treated with AgNPs with different particle sizes. Canada goldenrod leaf extracts with high concentration exhibit stronger allelopathic effects on the seedling height and root length of lettuce than those treated with low concentration. AgNPs of all particle sizes significantly decreased seed germination and seedling development indices of lettuce. AgNPs with larger particle sizes exerted stronger toxicity on leaf length and width of lettuce than those with smaller particle sizes. Thus, nanoparticles with larger particle sizes might mediate the production of increased sizes of cell wall pore size and large absorption of such substances by plant roots can be harmful. AgNPs significantly enhanced the allelopathic effects of Canada goldenrod on the seed germination and seedling development of lettuce. Small particle size AgNPs may play a more essential role in the enhanced allelopathic effects of low concentrations of Canada goldenrod leaf extracts; however, large particle size AgNPs may play a more important role in the enhanced allelopathic effects of high concentrations of Canada goldenrod leaf extracts.

Glutamic acid assisted phyto-management of silver-contaminated soils through sunflower; physiological and biochemical response

Phytoremediation is a cost-effective and eco-friendly technique for the removal of heavy metal-contaminated soils and water. The less availability and mobility of heavy metals in medium decreased the efficiency of this technique. The mobility and availability of these metals in the medium can be enhanced by the addition of organic chelators. The present study was conducted to investigate the possibility of glutamic acid (GA) in improving silver (Ag) phytoextraction by sunflower (Helianthus annuus L.). Different concentrations of Ag and GA were supplied in solution form in different combinations after defined intervals. Results depicted that increasing concentration of Ag significantly reduced the plant biomass, photosynthetic pigments, and antioxidant enzyme activities (like catalase, peroxidase, ascorbate, peroxidase, superoxide dismutase). Furthermore, Ag stress increased the Ag concentration and the production of reactive oxygen species (ROS) in sunflower plants. The addition of GA alleviated the Ag-induced toxicity in plants and enhanced Ag concentration and accumulation in sunflower. The addition of GA enhanced Ag accumulation in sunflower roots by 70, 79, 58, and 66% at 0-, 100-, 250-, and 500-μM Ag treatments, respectively, as compared to control plants. In conclusion, the results showed that Ag significantly reduced the physiological and biochemical attributes in term of reduced growth of sunflower and the addition of GA alleviated the Ag induced toxicity and enhanced Ag uptake. The results suggested that sunflower can be used as hyper-accumulator plant for the removal of Ag under GA. Further studies are required to understand the role of GA at gene and microscopic level in plants.

Impact of Zinc oxide nanoparticles on eggplant (S. melongena): studies on growth and the accumulation of nanoparticles

The increasing use of nanoparticles and their occurrence in the environment has made it imperative to elucidate their impact on the environment. Although several studies have advanced the authors' understanding of nanoparticle-plant interactions, their knowledge of the exposure of plants to nanoparticles and their effects on edible crop plants remain meager and is often paradoxical. The aim of this study was to increase their knowledge on the effect of zinc oxide (ZnO) nanoparticles on eggplant seed germination and seedling growth. ZnO nanoparticles had a negative effect on the growth of eggplant in plant tissue-culture conditions, as the growth of seedlings decreased with the increase in the concentration of ZnO nanoparticles. In contrast, ZnO nanoparticles enhanced eggplant growth under greenhouse conditions. The accumulation of ZnO nanoparticles in various parts of eggplant was observed through scanning electron microscopy of both plant tissue-culture and greenhouse-raised eggplant seedlings. To the best of their knowledge, this is the first study to report on ZnO nanoparticle accumulation in eggplant and its effect on seed germination and seedling growth.

Transformation-dissolution reactions partially explain adverse effects of metallic silver nanoparticles to soil nitrification in different soils

Risk assessment of metallic nanoparticles (NPs) is critically affected by the concern that toxicity goes beyond that of the metallic ion. The present study addressed this concern for soils with silver nanoparticles (AgNPs) using the Ag-sensitive nitrification assay. Three agricultural soils (A, B, and C) were spiked with equivalent doses of either AgNP (diameter = 13 nm) or AgNO₃ . Soil solution was isolated and monitored over 97 d with due attention to accurate Ag fractionation at low (∼10 μg L^-1 ) Ag concentrations. Truly dissolved (<1 kDa) Ag in the AgNO₃ -amended soils decreased with reaction half-lives of 4 to 22 d depending on the soil, denoting important Ag-aging reactions. In contrast, truly dissolved Ag in AgNP-amended soils first increased by dissolution and subsequently decreased by aging, the concentration never exceeding that in the AgNO₃ -amended soils. The half-lives of AgNP transformation-dissolution were approximately 4 d (soils A and B) and 36 d (soil C). The Ag toxic thresholds (10% effect concentrations, milligrams of Ag per kilogram of soil) of nitrification, evaluated at 21 or 35 d after spiking, were similar between the 2 Ag forms (soils A and B) but were factors of 3 to 8 lower for AgNO₃ than for AgNP (soil C), largely corroborating dissolution differences. This fate and bioassay showed that AgNPs are not more toxic than AgNO₃ at equivalent total soil Ag concentrations and that differences in Ag dissolution at least partially explain toxicity differences between the forms and among soils. Environ Toxicol Chem 2018;37:2123-2131. © 2018 SETAC.

Metabolomics Reveals How Cucumber ( Cucumis sativus) Reprograms Metabolites To Cope with Silver Ions and Silver Nanoparticle-Induced Oxidative Stress

Due to their well-known antifungal activity, the intentional use of silver nanoparticles (AgNPs) as sustainable nanofungicides is expected to increase in agriculture. However, the impacts of AgNPs on plants must be critically evaluated to guarantee their safe use in food production. In this study, 4-week-old cucumber ( Cucumis sativus) plants received a foliar application of AgNPs (4 or 40 mg/plant) or Ag⁺ (0.04 or 0.4 mg/plant) for 7 days. Gas chromatography-mass spectrometry (GC-MS)=based nontarget metabolomics enabled the identification and quantification of 268 metabolites in cucumber leaves. Multivariate analysis revealed that all the treatments significantly altered the metabolite profile. Exposure to AgNPs resulted in metabolic reprogramming, including activation of antioxidant defense systems (upregulation of phenolic compounds) and downregulation of photosynthesis (upregulation of phytol). Additionally, AgNPs enhanced respiration (upregulation of tricarboxylic acid cycle intermediates), inhibited photorespiration (downregulation of glycine/serine ratio), altered membrane properties (upregulation of pentadecanoic and arachidonic acids, downregulation of linoleic and linolenic acids), and reduced inorganic nitrogen fixation (downregulation of glutamine and asparagine). Although Ag ions induced some of the same metabolic changes, alterations in the levels of carbazole, lactulose, raffinose, citraconic acid, lactamide, acetanilide, and p-benzoquinone were AgNP-specific. The results of this study offer new insight into the molecular mechanisms by which cucumber responds to AgNP exposure and provide important information to support the sustainable use of AgNPs in agriculture.

Environmental behavior of coated NMs: Physicochemical aspects and plant interactions

The application of nanomaterials (NMs) depends on several characteristics, including polydispersity, shape, surface charge, and composition, among others. However, the specific surface properties of bare NMs induce aggregation, reducing their utilization. Thus, different surface coverages have been developed to avoid or minimize NMs aggregation, making them more stable for the envisioned applications. Carbon-based NMs are usually coated with metals, while metal-based NMs are coated with natural organic compounds including chitosan, dextran, alginate, or citric acid. On the other hand, the coating process is expected to modify the surface properties of the NMs; several coating agents add negative or positive charges to the particles, changing their interaction with the environment. In this review, we analyze the most recent literature about coating processes and the behavior of coated NMs in soil, water, and plants. In particular, the behavior of the most commercialized metal-based NMs, such as TiO₂, ZnO, CeO₂, CuO, Ag, and Au, and carbon-based NMs are discussed in this review. The available articles about the effects of coated NMs in plants are discussed. Up to now, there is no uniformity in the information to ensure that the surface coverage increases or decreases the effects of NMs in plants. While some parameters are increased, others are decreased. Since the data is contradictory in some cases, the available literature does not allow researchers to determine what concentrations benefit the plants. This review highlights current results and future perspectives on the study of the effects of coated NMs in the environment.

Alteration of Crop Yield and Quality of Wheat upon Exposure to Silver Nanoparticles in a Life Cycle Study

As a result of the rapid development of nanotechnology, metal-based nanoparticles (NPs) are inadvertently released into the environment and may pose a potential threat to the ecosystem. However, information for food quality and safety in NP-treated crops is limited. In the present study, wheat ( Triticum aestivum L.) was grown in different concentrations of Ag-NP-amended soil (20, 200, and 2000 mg kg^-1) for 4 months. At harvest, physiological parameters, Ag and micronutrient (Fe, Cu, and Zn) contents, and amino acid and total protein contents were measured. Results showed that, with increasing the exposure doses, Ag NPs exhibited severe phytotoxicity, including lower biomass, shorter plant height, and lower grain weight. Ag accumulation in roots was significantly higher than that in shoots and grains. Decreases in the content of micronutrients (Fe, Cu, and Zn) in Ag-NP-treated grains suggested low crop quality. The results of amino acid and protein contents in Ag-NP-treated wheat grains indicated that Ag NPs indeed altered the nutrient contents in the edible portion. In the amino acid profile, the presence of Ag NPs significantly decreased the contents of arginine and histidine by 13.0 and 11.8%, respectively. In summary, the effects of metal-based NPs on the edible portion of crops should be taken into account in the evaluation of nanotoxicity to terrestrial plants. Moreover, investigation of the potential impacts of NP-caused nutrient alterations on human health could further our understandings on NP-induced phytotoxicity.

Plant extract-mediated green silver nanoparticles: Efficacy as soil conditioner and plant growth promoter

Recently, concerns have been raised regarding the ultimate fate of silver nanoparticles (SNPs) after their release into the environment. In this study, the environmental feasibility of plant leaf (Thuja occidentalis) extract-mediated green SNPs (GSNPs) was assessed in terms of their effects on soil physicochemical properties and crop growth in comparison to conventionally synthesized silver nanoparticles (CSNPs). Upon application of GSNPs, soil pH shifted toward neutrality, and substantial increments were observed in water holding capacity (WHC), cation exchange capacity (CEC), and N/P availability. The mechanism behind the enhanced availability of N was verified through lab-scale experiments in which GSNP-treated soils efficiently resisted nitrate leaching, thereby sustaining N availability in root zone soil layers. However, retardation in nutrient availability and enzyme activity was apparent in soils treated with 100 mg kg^-1 of either CSNPs or GSNPs. Remarkable improvements in leaf area index (LAI), leaf number, chlorophyll content, nitrate reductase (NR) activity, and Phaseolus vulgaris pod yield were observed after the application of low doses of GSNPs (25-50 mg kg^-1). The true benefit of GSNP application to soil was substantiated through experiments on plant uptake of nutrients, NR expression, and ferredoxin gene expression in P. vulgaris leaves.

Nanoparticle Exposure and Hormetic Dose-Responses: An Update

The concept of hormesis, as an adaptive response of biological systems to moderate environmental challenges, has raised considerable nano-toxicological interests in view of the rapid pace of production and application of even more innovative nanomaterials and the expected increasing likelihood of environmental and human exposure to low-dose concentrations. Therefore, the aim of this review is to provide an update of the current knowledge concerning the biphasic dose-responses induced by nanoparticle exposure. The evidence presented confirmed and extended our previous findings, showing that hormesis is a generalized adaptive response which may be further generalized to nanoscale xenobiotic challenges. Nanoparticle physico-chemical properties emerged as possible features affecting biphasic relationships, although the molecular mechanisms underlining such influences remain to be fully understood, especially in experimental settings resembling long-term and low-dose realistic environmental exposure scenarios. Further investigation is necessary to achieve helpful information for a suitable assessment of nanomaterial risks at the low-dose range for both the ecosystem function and the human health.

Plant Response to Metal-Containing Engineered Nanomaterials: An Omics-Based Perspective

The increasing use of engineered nanomaterials (ENMs) raises questions regarding their environmental impact. Improving the level of understanding of the genetic and molecular basis of the response to ENM exposure in biota is necessary to accurately assess the true risk to sensitive receptors. The aim of this Review is to compare the plant response to several metal-based ENMs widely used, such as quantum dots, metal oxides, and silver nanoparticles (NPs), integrating available "omics" data (transcriptomics, miRNAs, and proteomics). Although there is evidence that ENMs can release their metal components into the environment, the mechanistic basis of both ENM toxicity and tolerance is often distinct from that of metal ions and bulk materials. We show that the mechanisms of plant defense against ENM stress include the modification of root architecture, involvement of specific phytohormone signaling pathways, and activation of antioxidant mechanisms. A critical meta-analysis allowed us to identify relevant genes, miRNAs, and proteins involved in the response to ENMs and will further allow a mechanistic understanding of plant-ENM interactions.

Effect of silver nanoparticles on phenolic compounds production and biological activities in hairy root cultures of Cucumis anguria

The present study describes the elicitor effect of silver ion (Ag⁺) and biologically synthesized silver nanoparticles (AgNPs) to enhance the biomass accumulation and phenolic compound production as well as biological activities (antioxidant, antimicrobial and anticancer) in genetically transformed root (hairy root) cultures of Cucumis anguria. The biomass of hairy root cultures was significantly increased by AgNPs whereas decreased in Ag⁺ elicitation at 1 and 2 mg/L. AgNPs-elicited hairy roots produced a significantly higher amount of individual phenolic compounds (flavonols, hydroxycinnamic and hydroxybenzoic acids), total phenolic and flavonoid contents than Ag⁺-elicited hairy roots. Moreover, antioxidant, antimicrobial and anticancer activities were significantly higher following AgNPs-elicitation compared with that in Ag⁺-elicited hairy roots. We suggest that AgNPs could be an efficient elicitor in hairy root cultures to increase the phytochemical production.

Application of Silver Nanostructures Synthesized by Cold Atmospheric Pressure Plasma for Inactivation of Bacterial Phytopathogens from the Genera Dickeya and Pectobacterium

Pectinolytic bacteria are responsible for significant economic losses by causing diseases on numerous plants. New methods are required to control and limit their spread. One possibility is the application of silver nanoparticles (AgNPs) that exhibit well-established antibacterial properties. Here, we synthesized AgNPs, stabilized by pectins (PEC) or sodium dodecyl sulphate (SDS), using a direct current atmospheric pressure glow discharge (dc-APGD) generated in an open-to-air and continuous-flow reaction-discharge system. Characterization of the PEC-AgNPs and SDS-AgNPs with UV/Vis absorption spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction revealed the production of spherical, well dispersed, and face cubic centered crystalline AgNPs, with average sizes of 9.33 ± 3.37 nm and 28.3 ± 11.7 nm, respectively. Attenuated total reflection-Fourier transformation infrared spectroscopy supported the functionalization of the nanostructures by PEC and SDS. Antibacterial activity of the AgNPs was tested against Dickeya spp. and Pectobacterium spp. strains. Both PEC-AgNPs and SDS-AgNPs displayed bactericidal activity against all of the tested isolates, with minimum inhibitory concentrations of 5.5 mg∙L-1 and 0.75-3 mg∙L-1, respectively. The collected results suggest that the dc-APGD reaction-discharge system can be applied for the production of defined AgNPs with strong antibacterial properties, which may be further applied in plant disease management.

Investigating long-term effect of nanoparticles on growth of Raphanus sativus plants: a trans-generational study

In the past decade, there has been an unprecedented growth in the application of nanoparticles (NPs) worldwide. Even though the acute toxicity of CuO and ZnO NPs to plants has been investigated in past, the trans-generational effects of these NPs in the environment are still unknown. In this study, we investigated whether the treatment of radish plants with CuO and ZnO NPs as single compound and as a binary mixture (10, 100 and 1000 mg/Kg soil) through their lifecycle would affect the seed quality and the development of second-generation seedlings or not. Results showed reduced root length, shoot length and biomass in F1 seedlings of NPs treated plants. The treated F1 seeds had smaller seed weight with accumulated Cu and Zn. The effect of toxic interaction between CuO and ZnO on plant growth was antagonistic in nature. Evaluation of the trans-generational impact is important to understand the long-term effect of NPs on the environment.

The toxicity of silver to soil organisms exposed to silver nanoparticles and silver nitrate in biosolids-amended field soil

The use of engineered silver nanoparticles (AgNPs) is widespread, with expected release to the terrestrial environment through the application of biosolids onto agricultural lands. The toxicity of AgNPs and silver nitrate (AgNO₃ ; as ionic Ag⁺ ) to plant (Elymus lanceolatus and Trifolium pratense) and soil invertebrate (Eisenia andrei and Folsomia candida) species was assessed using Ag-amended biosolids applied to a natural sandy loam soil. Bioavailable Ag⁺ in soil samples was estimated using an ion-exchange technique applied to KNO₃ soil extracts, whereas exposure to dispersible AgNPs was verified by single-particle inductively coupled plasma-mass spectrometry and transmission electron microscopy-energy dispersive X-ray spectroscopy analysis. Greater toxicity to plant growth and earthworm reproduction was observed in AgNP exposures relative to those of AgNO₃ , whereas no difference in toxicity was observed for F. candida reproduction. Transformation products in the AgNP-biosolids exposures resulted in larger pools of extractable Ag⁺ than those from AgNO₃ -biosolids exposures, at similar total Ag soil concentrations. The results of the present study reveal intrinsic differences in the behavior and bioavailability of the 2 different forms of Ag within the biosolids-soils pathway. The present study demonstrates how analytical methods that target biologically relevant fractions can be used to advance the understanding of AgNP behavior and toxicity in terrestrial environments. Environ Toxicol Chem 2017;36:2756-2765. © 2017 Crown in the Right of Canada. Published Wiley Periodicals Inc., on behalf of SETAC.

Toxicological implications of selenium nanoparticles with different coatings along with Se4+ on Lemna minor

Nanoparticles have potential high risks for living organisms in the environment due to their specific qualities and their easy access. In the present study, selenium nanoparticles (Se NPs) with two different coatings (l-cysteine and tannic acid) were synthesized. The characteristics of particles were analyzed using XRD, FT-IR and SEM. The impact of the nanoparticles besides Se⁴⁺, on the aquatic higher plant Lemna minor was evaluated and compared. Entrance of l-cysteine and tannic acid capped Se NPs in the roots of Lemna minor was proved by TEM and fluorescence microscopy. Adverse effects of mentioned NPs and differences of these effects from those by sodium selenite as the ionic form were assessed by a range of biophysicochemical tests. Altogether, the results asserted that Lemna minor was notably poisoned by both capped Se NPs and Se⁴⁺. Thus, growth and photosynthetic pigments were decreased while lipid peroxidation along with total phenol and flavonoid contents were raised. Eventually some changes in enzymatic activities were presented. To sum up the consequences, it can be concluded that all changes occurred due to the plant defense system especially in order to remove reactive oxygen species (ROS) and possible phytotoxicity originated by l- cysteine and tannic acid capped Se NPs in addition to Se⁴⁺. The influence of tannic acid capped Se NPs after sodium selenite is stronger by the means of antioxidant enzymes activity in comparison with l-cysteine capped Se NPs.

Cytokinin response in pepper plants (Capsicum annuum L.) exposed to silver nanoparticles

The increasing development of different nanomaterials, such as silver nanoparticles (AgNPs), and their practical use in agriculture and biotechnology has created a strong need for elucidations of biological effects and risk assessments of AgNPs in plants. This study was aimed to investigate AgNPs effects on metal uptake and their biodistribution in pepper plants as well as on morphological parameters and hormonal responses of the isoprenoid cytokinin (CK) family. In addition, the comparison of effects silver form, nanoparticles vs. ionic, has also been examined. To the best of our knowledge, this is the first study describing CK responses in plants exposed to metallic NPs. The obtained results indicate that both AgNPs and Ag⁺ ions significantly increased total content of Ag⁺ in pepper tissues in a dose-dependent manner and affected on plant development by decreasing both plant height and biomass in a similar way. This study evidenced for the first time the role of CKs in abiotic stress in plants caused by AgNPs. The hormonal analysis, conducted by an ultra-high performance liquid chromatography-electrospray tandem mass spectrometry, revealed a significant increase in total CKs in the leaves and also highlighted the importance of cis-zeatin type CKs in plants treated with AgNPs. Our observations suggest potential risks of AgNPs on plant ecosystems upon their release into the environment.

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

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