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

An assessment of nanotechnology-based interventions for cleaning up toxic heavy metal/metalloid-contaminated agroecosystems: Potentials and issues

Heavy metals (HMs) are among the most dangerous environmental variables for a variety of life forms, including crops. Accumulation of HMs in consumables and their subsequent transmission to the food web are serious concerns for scientific communities and policy makers. The function of essential plant cellular macromolecules is substantially hampered by HMs, which eventually have a detrimental effect on agricultural yield. Among these HMs, three were considered, i.e., arsenic, cadmium, and chromium, in this review, from agro-ecosystem perspective. Compared with conventional plant growth regulators, the use of nanoparticles (NPs) is a relatively recent, successful, and promising method among the many methods employed to address or alleviate the toxicity of HMs. The ability of NPs to reduce HM mobility in soil, reduce HM availability, enhance the ability of the apoplastic barrier to prevent HM translocation inside the plant, strengthen the plant's antioxidant system by significantly enhancing the activities of many enzymatic and nonenzymatic antioxidants, and increase the generation of specialized metabolites together support the effectiveness of NPs as stress relievers. In this review article, to assess the efficacy of various NP types in ameliorating HM toxicity in plants, we adopted a 'fusion approach', in which a machine learning-based analysis was used to systematically highlight current research trends based on which an extensive literature survey is planned. A holistic assessment of HMs and NMs was subsequently carried out to highlight the future course of action(s).

A Study on the Growth and Physiological Toxicity Effects of the Combined Exposure of Microplastics and Cadmium on the Vicia faba L. Seedlings

To investigate the toxicological effects of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined contamination on the growth and physiological responses of V. faba seedlings, this experiment employed a hydroponic method. The Hoagland nutrient solution served as the control, changes in root growth, physiological and biochemical indicators of V. faba seedlings under different concentrations of PS-MPs (10, 100 mg/L) alone and combined with 0.5 mg/L Cd. The results demonstrated that the root biomass, root vitality, generation rate of superoxide radicals (O2·-), malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity increased with increasing concentration under the influence of PS-MPs alone, while the soluble sugar content and peroxidase (POD) activity decreased. In the combined treatment with Cd, the trends of these indicators are generally similar to the PS-MPs alone treatment group. However, root vitality and SOD activity showed an inverse relationship with the concentration of PS-MPs. Furthermore, laser confocal and electron microscopy scanning revealed that the green fluorescent polystyrene microspheres entered the root tips of the V. faba and underwent agglomeration in the treatment group with a low concentration of PS-MPs alone and a high concentration of composite PS-MPs with Cd.

Graphene oxide-based nanocomposites for outstanding eco-friendly antifungal potential against tomato phytopathogens

To obtain the collaborative antifungal potential of nanocomposites conjugated with graphene oxide (GO), a combination of GO with chitosan (CS/GO) and GO with chitosan (CS) and polyaniline (PANI/CS/GO) was carried out. The synthesized GO-nanocomposites were recognized by several techniques. Vanillin (Van.) and cinnamaldehyde (Cinn.) were loaded on the prepared nanocomposites as antioxidants through a batch adsorption process. In vitro release study of Van. and Cinn. from the nanocomposites was accomplished at pH 7 and 25°C. The antimicrobial activity of GO, CS/GO, and PANI/CS/GO was studied against tomato Fusarium oxysporum (FOL) and Pythium debaryanum (PYD) pathogens. The loaded ternary composite PANI/CS/GO exhibited the best percent of reduction against the two pathogens in vitro studies. The Greenhouse experiment revealed that seedlings' treatment by CS/GO/Van. and PANI/CS/GO/Van significantly lowered both disease index and disease incidence. The loaded CS/GO and PANI/CS/GO nanocomposites had a positive effect on lengthening shoots. Additionally, when CS/GO/Cinn., CS/GO/Van. and PANI/CS/GO/Van. were used, tomato seedlings' photosynthetic pigments dramatically increased as compared to infected control. The results show that these bio-nanocomposites can be an efficient, sustainable, nontoxic, eco-friendly, and residue-free approach for fighting fungal pathogens and improving plant growth.

Effect of graphene oxide nanoparticles on in vitro growth of Fragaria x ananassa (Cameron Highlands white Strawberry) and evaluation of genetic stability using DAMD and ISSR markers

Graphene oxide (GO) is a novel nanomaterial with distinct physical properties and significant biological applications. The use of GO in plant tissue culture offers several new properties and potential applications. This research is vital due to the growing need for innovative techniques to promote plant growth, improve plant productivity and mitigate challenges posed by environmental stressors. This study focused on the rare Cameron Highlands white strawberry plants (Fragaria x ananassa) and addressed issues such as callus production during direct shoot induction and hyperhydricity. The research aimed to investigate the effects of GO on the regeneration process and genetic stability of white strawberry plants and to use molecular markers to ensure that plants propagated in vitro are true to type. For this purpose, shoot tip explants were used and different concentrations of GO (0, 2.5, 5.0, 7.5, 10 mg/L) were added to the Murashige and Skoog (MS) medium for six weeks. The results showed that the optimum concentration for promoting the development of white strawberry seedlings was 7.5 mg/L of GO. The study also revealed that the addition of 7.5 mg/L GO in combination with 8 μM TDZ to the MS medium facilitated the induction of multiple shoots. Moreover, the clonal fidelity of the in vitro plants treated with GO showed a genetic similarity of over 97%. These results confirm that lower GO concentrations improve plant development and stability. Consequently, this nanomaterial has a positive effect on the growth of strawberry plants and is therefore well suited for strawberry tissue culture.

Graphene nanoparticles improve alfalfa (Medicago sativa L.) growth through multiple metabolic pathways under salinity-stressed environment

Graphene, one of the emerging carbon nanomaterials, has many advantages and applications. Salinity stress seriously affects ecology and agroforestry worldwide. The effects of graphene on alfalfa under salinity stress were investigated. The results indicated that graphene promoted alfalfa growth under non-salinity stress but caused some degree of damage to root cells and leaf parameters. Graphene used in salinity stress had a positive effect on growth parameters, chlorophyll, photosynthetic gas parameters, stomatal opening, ion balance, osmotic homeostasis, cell membrane integrity and antioxidant system, while it decreased Na+, lipid peroxidation and reactive oxygen species levels. Correlation analysis revealed that most of the parameters were significantly correlated; and principal component analysis indicated that the first two dimensions (78.1% and 4.1%) explained 82.2% of the total variability, and the majority of them exceeded the average contribution. Additionally, Gene Ontology functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes signaling pathway enrichment analysis showed that there were numerous differentially expressed genes and pathways to regulate alfalfa responding to salinity stress. Taken together, the findings reveal that graphene does not enter the plant, but improves the properties and adsorption of soil to enhance salt tolerance and seedling growth of alfalfa through morphological, physiological, biochemical, and transcriptomic aspects. Furthermore, this study provides a reference for the application of graphene to improve soil environment and agricultural production.

Effect of graphene on soybean root colonization by Bradyrhizobium strains

Legume crops such as soybean obtain a large portion of their nitrogen nutrition through symbiotic nitrogen fixation by diazotrophic rhizobia bacteria in root nodules. However, nodule occupancy by low-capacity nitrogen-fixing rhizobia can lead to lower-than-optimal levels of nitrogen fixation. Seed/root coating with engineered materials such as graphene-carrying biomolecules that may promote specific attraction/attachment of desirable bacterial strains is a potential strategy that can help overcome this rhizobia competition problem. As a first step towards this goal, we assessed the impact of graphene on soybean and Bradyrhizobium using a set of growth, biochemical, and physiological assays. Three different concentrations of graphene were tested for toxicity in soybean (50, 250, and 1,000 mg/l) and Bradyrhizobia (25, 50, and 100 mg/l). Higher graphene concentrations (250 mg/l and 1,000 mg/l) promoted seed germination but slightly delayed plant development. Spectrometric and microscopy assays for hydrogen peroxide and superoxide anion suggested that specific concentrations of graphene led to higher levels of reactive oxygen species in the roots. In agreement, these roots also showed higher activities of antioxidant enzymes, catalase, and ascorbate peroxidase. Conversely, no toxic effects were detected on Bradyrhizobia treated with graphene, and neither did they have higher levels of reactive oxygen species. Graphene treatments at 250 mg/l and 1,000 mg/l significantly reduced the number of nodules, but rhizobia infection and the overall nitrogenase activity were not affected. Our results show that graphene can be used as a potential vehicle for seed/root treatment.

Regulation and safety measures for nanotechnology-based agri-products

There is a wide range of application for nanotechnology in agriculture, including fertilizers, aquaculture, irrigation, water filtration, animal feed, animal vaccines, food processing, and packaging. In recent decades, nanotechnology emerged as a prospective and promising approach for the advancement of Agri-sector such as pest/disease prevention, fertilizers, agrochemicals, biofertilizers, bio-stimulants, post-harvest storage, pheromones-, and nutrient-delivery, and genetic manipulation in plants for crop improvement by using nanomaterial as a carrier system. Exponential increase in global population has enhanced food demand, so to fulfil the demand markets already included nano-based product likewise nano-encapsulated nutrients/agrochemicals, antimicrobial and packaging of food. For the approval of nano-based product, applicants for a marketing approval must show that such novel items can be used safely without endangering the consumer and environment. Several nations throughout the world have been actively looking at whether their regulatory frameworks are suitable for handling nanotechnologies. As a result, many techniques to regulate nano-based products in agriculture, feed, and food have been used. Here, we have contextualized different regulatory measures of several countries for nano-based products in agriculture, from feed to food, including guidance and legislation for safety assessment worldwide.

GO nanoparticles mitigate the negative effects of salt and alkalinity stress by enhancing gas exchange and photosynthetic efficiency of strawberry plants

Considering the potential use of nanomaterials, particularly carbon-based nanostructures, in agriculture, we conducted a study to investigate the effect of graphene oxide (GO) on strawberry plants under salinity and alkalinity stress conditions. We used GO concentrations of 0, 2.5, 5, 10, and 50 mg/L, and applied stress treatments at three levels: without stress, salinity (80 mM NaCl), and alkalinity (40 mM NaHCO₃). Our results indicate that both salinity and alkalinity stress negatively impacted the gas exchange parameters of the strawberry plants. However, the application of GO significantly improved these parameters. Specifically, GO increased PI, F_v, F_m, and RE₀/RC parameters, as well as chlorophyll and carotenoid contents in the plants. Moreover, the use of GO significantly increased the early yield and dry weight of leaves and roots. Therefore, it can be concluded that the application of GO can enhance the photosynthetic performance of strawberry plants, and improve their resistance to stress conditions.

Toxicological effects resulting from co-exposure to nanomaterials and to a β-blocker pharmaceutical drug in the non-target macrophyte species Lemna minor

The wide use of carbon-based materials for various purposes leads to their discharge in the aquatic systems, and simultaneous occurrence with other environmental contaminants, such as pharmaceutical drugs. This co-occurrence can adversely affect exposed aquatic organisms. Up to now, few studies have considered the simultaneous toxicity of nanomaterials, and organic contaminants, including pharmaceutical drugs, towards aquatic plants. Thus, this study aimed to assess the toxic effects of the co-exposure of propranolol (PRO), and nanomaterials based on cellulose nanocrystal, and graphene oxide in the aquatic macrophyte Lemna minor. The observed effects included reduction of growth rate in 13% in co-exposure 1 (nanomaterials + PRO 5 μg L^-1), and 52-64% in co-exposure 2 (nanomaterials + PRO 51.3 mg L^-1), fresh weight reduction of 94-97% in co-exposure 2 compared to control group, and increased pigment production caused by co-exposure treatments. The analysis of PCA showed that co-exposure 1 (nanomaterials + PRO 5 μg L^-1) positively affected growth, and fresh weight, and co-exposure 2 positively affected pigments content. The results suggested that the presence of nanomaterials enhanced the overall toxicity of PRO, exerting deleterious effects in the freshwater plant L. minor, suggesting that this higher toxicity resulting from co-exposure was a consequence of the interaction between nanomaterials and PRO.

The combined effect of graphene oxide and elemental nano-sulfur on soil biological properties and lettuce plant biomass

The impact of graphene oxide (GO) nanocarbon on soil properties is mixed, with both negative and positive effects. Although it decreases the viability of some microbes, there are few studies on how its single amendment to soil or in combination with nanosized sulfur benefits soil microorganisms and nutrient transformation. Therefore, an eight-week pot experiment was carried out under controlled conditions (growth chamber with artificial light) in soil seeded with lettuce (Lactuca sativa) and amended with GO or nano-sulfur on their own or their several combinations. The following variants were tested: (I) Control, (II) GO, (III) Low nano-S + GO, (IV) High nano-S + GO, (V) Low nano-S, (VI) High nano-S. Results revealed no significant differences in soil pH, dry plant aboveground, and root biomass among all five amended variants and the control group. The greatest positive effect on soil respiration was observed when GO was used alone, and this effect remained significant even when it was combined with high nano-S. Low nano-S plus a GO dose negatively affected some of the soil respiration types: NAG_SIR, Tre_SIR, Ala_SIR, and Arg_SIR. Single GO application was found to enhance arylsulfatase activity, while the combination of high nano-S and GO not only enhanced arylsulfatase but also urease and phosphatase activity in the soil. The elemental nano-S probably counteracted the GO-mediated effect on organic carbon oxidation. We partially proved the hypothesis that GO-enhanced nano-S oxidation increases phosphatase activity.

A mesoporous silica nanocarrier pesticide delivery system for loading acetamiprid: Effectively manage aphids and reduce plant pesticide residue

A multifunctional nanomaterials-based agrochemical delivery system could supply a powerful tool for the efficient use of pesticides. Redox-responsive carriers as novel delivery systems of pesticide application in agriculture could promote the pest control and reduce plant pesticide residues due to the controllable release of agrochemicals. Herein, neonicotinoid insecticide acetamiprid (Ace) was encapsulated with decanethiol in a mesoporous silica nanocarrier pesticide delivery system for a nanopesticide Ace@MSN-SS-C10. The Ace@MSN-SS-C10 had redox-responsive sustained release behavior triggered by glutathione (GSH). Moreover, the Ace@MSN-SS-C10 possessed excellent wettability, adhesion performance, stability, and biosafety. Greenhouse experiments showed that foliar spraying 1.5 mg Ace@MSN-SS-C10 per plant reduced the populations of adult and juvenile aphids (Aphis craccivora Koch) on Vicia faba L. after 5 days of aphid infestation by 98.7 % and 99.3 %, respectively. Notably, the leaf final Ace residue (0.32 ± 0.004 mg/kg) of Ace@MSN-SS-C10 application at the dose of 1.5 mg/plant after 5 days of aphid infestation was lower than the international Codex Alimentarius Commission (CAC) maximum residue limits (0.4 mg·kg^-1) or much lower (24.87-folds decrease) than those treated with conventional Ace (40 % acetamiprid water dispersible granule). Altogether, this GSH-dependent redox-responsive delivery system for loading acetamiprid can develop as an efficient and environmentally-friendly nanopesticide to control aphids in sustainable agriculture.

Atomistic insights into migration mechanism of graphene-based membranes on soil mineral phases

Graphene-based membranes (GBM) will migrate in the soil and enter the groundwater system or plant roots, which will eventually pose potential risks to human beings. The migration mechanism of GBM depends on the interface behavior of complex soil components. Herein, we use molecular dynamics (MD) simulations to probe the interface behavior between GBM and three type minerals (quartz, calcite and kaolinite). Based on the investigation of binding energy, maximum pulling force and barrier energy, the order of the difficulty of GBM adsorption and desorption on the three minerals from small to large is roughly: quartz, calcite and kaolinite respectively. The graphene-oxide (GO), improves the binding energy and energy barrier, making GBM difficult to migrate in soil. Remarkably, a larger GBM sheet and high velocity external load improve GBM migration in soil to a certain extent. These investigations give the dynamic information on the GBM/mineral interaction and provide nanoscale insights into the migration mechanisms of GBM in soil.

Foliar application of selenium affecting pollen viability, grain chalkiness, and transporter genes in cadmium accumulating rice cultivar: A pot study

Under Cadmium (Cd) stress, rice grain quality and quantity are compromised, affecting human health. Application of Selenium (Se) mitigating Cd stress in rice was already reported, but its role in rescuing Cd induced damage in the reproductive parts in rice plants has not been studied before. To investigate the underlying mechanism, Se mediated alleviation of Cd-stress induced damage to pollen viability, germination rate, and grain chalkiness were studied. A grain Cd accumulating rice genotype was selected and treated with 10 μM Cd and sprayed with 5 μM Se during tillering, elongating and heading stages. A significant reduction in pollen viability, germination percentage, and accumulation of higher amount of ROS in the reproductive parts were observed in Cd treated plants. However, Se supplementation (i.e. Cd + Se), decreased the ROS accumulation in anther, pistil, pollen and enhanced the pollen viability and germination percentage. Cd translocation was prevented from flag leaf to grains, under Se treatment. As a result, a significantly higher seed setting rate, and yield were observed. Additionally, Se improved grain nutrient content and grain quality. Therefore, the recent study suggests that the use of foliar spray of Se could be a cost-effective strategy to prevent Cd-induced yield loss and quality in rice.

Effect of graphene oxide on the uptake, translocation and toxicity of metal mixture to Lepidium sativum L. plants: Mitigation of metal phytotoxicity due to nanosorption

Due to its unique structure and exceptional properties, graphene oxide (GO) is increasingly used in various fields of industry and therefore is inevitably released into the environment, where it interacts with different contaminants. However, the information relating to the ability of GO to affect the toxicity of contaminants is still limited. Therefore, the aim of our study was to synthesize GO, to examine the phytotoxicity of different concentrations of GO and its co-exposure with the metal mixture using garden cress (Lepidium sativum L.) as a test organism and to evaluate the potential of GO to affect toxicity of metals and their uptake by plants. The metal mixture (MIX) containing Ni (II), Zn (II), Cr (III) and Cu (II) was prepared in accordance with the maximum-permissible-concentrations (MPC) accepted for the inland waters in the EU. Additionally, the capacity of GO to adsorb metals was studied in specific conditions of the phytotoxicity test and assessed using adsorption isotherms. Our data indicate that in most cases the tested concentrations of MIX, GO and MIX + GO did not affect seed germination, root growth and biomass of roots and seedlings, however, they were found to alter photosynthesis processes, enhance production of carotenoids and H₂O₂ as well as to activate lipid peroxidation. Additionally, our study revealed that GO affects the accumulation of tested metals in roots and shoots of the MIX-exposed L. sativum. This is due to the capacity of GO to adsorb metals from the growth medium. Therefore, low concentrations of GO can be used for water decontamination.

The nitrate uptake and growth of wheat were more inhibited under single-layer graphene oxide stress compared to multi-layer graphene oxide

Although the phytotoxicity of graphene-based materials has been investigated extensively, the effects of different graphene-based materials on nutrient uptake in plants remain unclear. Here, we analyzed the differences in phytotoxicity between single-layer graphene oxide (sGO) and multi-layer graphene oxide (mGO) by analyzing the growth status and nitrate (NO₃^-) accumulation in wheat plants at 0, 100, 200, 400, and 800 mg L^-1 graphene oxide supply. Both sGO and mGO displayed concentration-dependent inhibitory effects on biomass, root length, number of lateral roots, and nitrogen (N) nutrient status. Treatment with 400 mg L^-1 sGO caused 0.9-, 1.3-, and 1-fold higher reductions in NO₃^--N, assimilated N, and total N concentrations in roots, respectively, than mGO treatment. Analysis of root oxidative stress and in situ NO₃^- uptake revealed that sGO caused more significant damage to the root tip and a lower NO₃^- net influx rate than mGO. In addition, the expression of NO₃^- transporter (NRT) genes in roots, including NRT1.5, NRT2.1, NRT2.2, NRT2.3, and NRT2.4, under sGO treatment were lower than those under mGO treatment. Overall, sGO treatment induced a more severe inhibitory effect on root growth and NO₃^- uptake and accumulation than mGO treatment, accompanied by significant suppression of the expression of NRTs in sGO-treated roots. This study provides a physiological and molecular basis for studying the phytotoxic effects of various sizes of graphene oxide.

Green synthesis and application of GO nanoparticles to augment growth parameters and yield in mungbean (Vigna radiata L.)

Plant growth promotion has long been a challenge for growers all over the world. In this work, we devised a green nanomaterial-assisted approach to boost plant growth. It has been reported that carbon nanomaterials are toxic to plants because they can inhibit the uptake of nutrients if employed in higher concentrations, however this study shows that graphene oxide (GO) can be used as a regulator tool to improve plant growth and stability. Graphene oxide in different concentrations was added to the soil of mungbean. It is proved that when a suitable amount of graphene oxide was applied, it had a good influence on plant growth by enhancing the length of roots and shoots, number of leaves, number of root nodules per plant, number of pods, and seeds per pod. We presume that the use of bio-fabricated graphene oxide as a strategy would make it possible to boost both plant growth and the significant increase in the number of seeds produced by each plant.

Effects of Graphene Oxide on Plant Growth: A Review

Several reports of graphene oxide (GO) promoting plant growth have sparked interest in its potential applications in agroforestry. However, there are still some toxicity studies that have raised concerns about the biosafety of GO. These reports show conflicting results from different perspectives, such as plant physiology, biochemistry, cytology, and molecular biology, regarding the beneficial and detrimental effects of GO on plant growth. Seemingly inconsistent studies make it difficult to effectively apply GO in agroforestry. Therefore, it is crucial to review and analyze the current literature on the impacts of GO on plant growth and its physiological parameters. Here, the biological effects of GO on plant growth are summarized. It is proposed that an appropriate concentration of GO may be conducive to its positive effects, and the particle size of GO should be considered when GO is applied in agricultural applications. This review provides a comprehensive understanding of the effects of GO on plant growth to facilitate its safe and effective use.

Recent progress in bio-mediated synthesis and applications of engineered nanomaterials for sustainable agriculture

The ever-increasing demand for agricultural food products, medicine, and other commercial sectors requires new technologies for agricultural practices and promoting the optimum utilization of natural resources. The application of engineered nanomaterials (ENMs) enhance the biomass production and yield of food crop while resisting harmful environmental stresses. Bio-mediated synthesis of ENMs are time-efficient, low-cost, environmentally friendly, green technology. The precedence of using a bio-mediated route over conventional precursors for ENM synthesis is non-toxic and readily available. It possesses many active agents that can facilitate the reduction and stabilization processes during nanoparticle formation. This review presents recent developments in bio-mediated ENMs and green synthesis techniques using plants, algae, fungi, and bacteria, including significant contributions to identifying major ENM applications in agriculture with potential impacts on sustainability, such as the role of different ENMs in agriculture and their impact on different plant species. The review also covers the advantages and disadvantages of different ENMs and potential future research in this field.

Effects of biochar-based materials on the bioavailability of soil organic pollutants and their biological impacts

Motivated by the unique structure and superior properties, biochar-based materials, including pristine biochar and composites of biochar with other functional materials, are considered as new generation materials for diverse multi-functional applications, which may be intentionally or unintentionally released to soil. The influencing mechanism of biochar-based material on soil organisms is a key aspect for quantifying and predicting its benefits and trade-offs. This work focuses on the effects of biochar-based materials on soil organisms within the past ten years. 206 sources are reviewed and available knowledge on biochar-based materials' impacts on soil organisms is summarized from a diverse perspective, including the pollutant bioavailability changes in soil, and potential effects of biochar-based materials on soil organisms. Herein, effects of biochar-based materials on the bioavailability of soil organic pollutants are detailed, from the perspective of plant, microorganism, and soil fauna. Potential biological effects of pristine biochar (PBC), metal/metal compounds-biochar composites (MBC), clay minerals-biochar composites (CMBC), and carbonaceous materials-biochar composites (CBC) on soil organisms are highlighted for the first time. And possible mechanisms are presented based on the different characters of biochar-based materials as well as various environmental interactions. Finally, the bottleneck and challenges of risk assessment of biochar-based materials as well as future prospects are proposed. This work not only promotes the development of risk assessment system of biochar-based materials, but broadens the strategy for the design and optimization of environmental-friendly biochar materials.

Proteomic, biochemical, and anatomical influences of nanographene oxide on soybean (Glycine max)

Nano-graphene oxide (NGO) is an engineered nanostructure that is used in various fields including biology, chemistry, medicine, and environmental protection. This kind of highly used nanomaterial (NM) is being released and accumulated gradually in nature and can have some adverse influences on living organisms including plants. Soybean as a cultivated plant with a high importance in food industry, but sensitive to stresses, was chosen in the present study to be examined in terms of proteomic, biochemical, and anatomical properties under the NGO stress. Accordingly, a 2-dimensional gel electrophoresis (2-DE) approach was adopted for proteomic analysis of the NGO treated soybean roots, where significant changes were observed in the abundance of 48 proteins. MALDI TOF/TOF analysis revealed the upregulation of the proteins involved in the redox regulation in plants. Furthermore, anatomical examination of soybean roots under light microscopy showed that the NGO could enter into the root epidermis through the apoplastic pathway and accumulated in some parts of the root. With increasing NGO concentration, the diameter of the vascular apertures increased and then decreased at higher concentrations. To evaluate the toxicity of NGO, some of the growth parameters including fresh and dry weight, and height of the shoots, as well as some stress-related biochemical properties such as H2O2 production, antioxidant enzymes activity, and phenolics and flavonoids contents were measured. The results indicated that NGO could cause an oxidative stress, which can be considered a toxic effect evoking antioxidative and detoxification mechanisms in soybean.

Nanomaterials coupled with microRNAs for alleviating plant stress: a new opening towards sustainable agriculture

Plant growth and development is influenced by their continuous interaction with the environment. Their cellular machinery is geared to make rapid changes for adjusting the morphology and physiology to withstand the stressful changes in their surroundings. The present scenario of climate change has however intensified the occurrence and duration of stress and this is getting reflected in terms of yield loss. A number of breeding and molecular strategies are being adopted to enhance the performance of plants under abiotic stress conditions. In this context, the use of nanomaterials is gaining momentum. Nanotechnology is a versatile field and its application has been demonstrated in almost all the existing fields of science. In the agriculture sector, the use of nanoparticles is still limited, even though it has been found to increase germination and growth, enhance physiological and biochemical activities and impact gene expression. In this review, we have summarized the use and role of nanomaterial and small non-coding RNAs in crop improvement while highlighting the potential of nanomaterial assisted eco-friendly delivery of small non-coding RNAs as an innovative strategy for mitigating the effect of abiotic stress.

Assessment of graphene oxide toxicity on the growth and nutrient levels of white clover (Trifolium repens L.)

Carbon nanomaterials (CNMs) are novel engineered nanomaterials and have been used widely. Their toxic effects on terrestrial plants in soil matrix require careful investigation. In this study, white clover (Trifolium repens L.) was grown in a potted soil with graphene oxide (GO) at levels of 0.2%, 0.4% and 0.6% and the effects of GO on the growth and nutrient uptake of white clover were evaluated after 50 and 100 days of exposure. GO exposure showed adverse effects on seedling growth, photosynthetic parameters and nutrient uptake in shoots, and the effect was more significant with increasing concentration and exposure time. Compared with the control, GO at the highest level of 0.6% decreased plant height, leaf and stem dry weights, total chlorophyll content and net photosynthetic rate by 43.7%, 45.7%, 43.4%, 32% and 85.7%, respectively, after 100 d of exposure, and N, K, Cu, Zn, Fe, Mo, B, Si contents decreased by 19.5%, 20.1%, 12.6%, 25.0%, 12.9%, 26.0%, 18.9%, 23.0%, respectively. Furthermore, the electrolyte leakage, lipid peroxidation, reactive oxygen species, antioxidant enzyme activities were all increased by GO, especially at high dose and long exposure. These results indicate that GO can suppress plant growth by oxidative stress, photosynthesis inhibition, and nutrient imbalance.

The Effects of Graphene-Family Nanomaterials on Plant Growth: A Review

Numerous reports of graphene-family nanomaterials (GFNs) promoting plant growth have opened up a wide range of promising potential applications in agroforestry. However, several toxicity studies have raised growing concerns about the biosafety of GFNs. Although these studies have provided clues about the role of GFNs from different perspectives (such as plant physiology, biochemistry, cytology, and molecular biology), the mechanisms by which GFNs affect plant growth remain poorly understood. In particular, a systematic collection of data regarding differentially expressed genes in response to GFN treatment has not been conducted. We summarize here the fate and biological effects of GFNs in plants. We propose that soil environments may be conducive to the positive effects of GFNs but may be detrimental to the absorption of GFNs. Alterations in plant physiology, biochemistry, cytological structure, and gene expression in response to GFN treatment are discussed. Coincidentally, many changes from the morphological to biochemical scales, which are caused by GFNs treatment, such as affecting root growth, disrupting cell membrane structure, and altering antioxidant systems and hormone concentrations, can all be mapped to gene expression level. This review provides a comprehensive understanding of the effects of GFNs on plant growth to promote their safe and efficient use.

Soil-based nano-graphene oxide and foliar selenium and nano-Fe influence physiological responses of 'Sultana' grape under salinity

Salinity is a worldwide stressor that influences the growth and productivity of plants. Some novel compounds like; graphene oxide and nutrients such as Se and Fe especially as nano form may improve plant responses to the environmental stress factors. The soil-based graphene oxide (0, 50, and 100 g kg⁻¹) and the foliar applications of Se and nano-Fe (control and 3 mg L⁻¹) were assayed on grapevine cv. Sultana under salinity (0, 50, and 100 mM NaCl). The top flavonoids, chlorophyll b, and plant dry weight belonged to graphene oxide and nano-Fe applications. CAT activity was improved in response to Se, nano-Fe, and graphene oxide (50 g kg⁻¹). The least Fe, K, Se, N, Mg, Mn, and Zn content was recorded for 100 mM NaCl. In contrast, the higher data for K, Se, Ca, Mg, Zn and Mn were acquired with graphene oxide × foliar treatments. In general, graphene oxide treatment (50 g kg⁻¹) × nano-Fe and Se foliar use ameliorated the adverse salinity effects with the improved biochemical and physiological responses of Sultana grape.

Nanomaterial sulfonated graphene oxide advances the tolerance against nitrate and ammonium toxicity by regulating chloroplastic redox balance, photochemistry of photosystems and antioxidant capacity in Triticum aestivum

The current study was designed to assess nanomaterial sulfonated graphene oxide (SGO) potential in improving tolerance of wheat chloroplasts against nitrate (NS) and ammonium (AS) toxicity. Triticum aestivum cv. Ekiz was grown under SGOs (50-250-500 mg L^-1) with/without 140 mM NS and 5 mM AS stress. SGOs were eliminated the adverse effects produced by stress on chlorophyll fluorescence, potential photochemical efficiency and physiological state of the photosynthetic apparatus. SGO reversed the negative effects on these parameters. Upon SGOs exposure, the induced expression levels of photosystems-related reaction center proteins were observed. SGOs reverted radical accumulation triggered by NS by enabling the increased superoxide dismutase (SOD) activity and ascorbate (AsA) regeneration. Under AS, the turnover of both AsA and glutathione (GSH) was maintained by 50-250 mg L^-1 SGO by increasing the enzymes and non-enzymes related to AsA-GSH cycle. 500 mg L^-1 SGO prevented the radical over-accumulation produced by AS via the regeneration of AsA and peroxidase (POX) activity rather than GSH regeneration. 50-250 mg L^-1 SGO protected from the NS+AS-induced disruptions through the defense pathways connected with AsA-GSH cycle represented the high rates of AsA/DHA and, GSH/GSSG and GSH redox state. Our findings specified that SGO to NS and AS-stressed wheat provides a new potential tool to advance the tolerance mechanism.

Graphene oxide decreases Cd concentration in rice seedlings but intensifies growth restriction

The extensive use of graphene oxide (GO) results in its inevitable entry into the environment, raising risks to the environment, especially the ecological risks when coexisting with other contaminants. Nevertheless, how GO affects the biological behavior of Cd in plants remains poorly understood. Here, we report that the transcript levels of Cd transporters, including OsIRT1, OsIRT2, OsNramp1, OsNramp5, and OsHMA2, were decreased by 56-96% in Cd-stressed rice seedlings with exposure to 400 mg L^-1 GO compared with those without GO exposure. The in situ non-invasive microelectrodes test revealed that GO clearly reduced the net Cd influx of rice roots. Thus, GO exposure decreased the level of Cd in rice seedlings by approximately 60%, compared with the GO-free condition. However, the analyses of biomass, chlorophyll fluorescence parameters and Evans blue staining, indicated that GO had adverse effects on the robustness of plants under the Cd co-contaminated condition. Taken together, although GO reduced the accumulation of Cd in rice seedlings, it still negatively affected plant growth. Therefore, the positive and negative impacts of GO on crop production are of concern. Our findings provide new information for establishing a wider phytotoxicity evaluation system for the safe manufacture and use of GO.

Graphene Oxide Normal (GO + Mn2+) and Ultrapure: Short-Term Impact on Selected Antioxidant Stress Markers and Cytokines in NHDF and A549 Cell Lines

Since biological applications and toxicity of graphene-based materials are structure dependent, studying their interactions with the biological systems is very timely and important. We studied short-term (1, 24, and 48 h) effects of ultrapure (GO) and Mn²⁺-contaminated (GOS) graphene oxide on normal human dermal fibroblasts (NHDF) and adenocarcinomic human alveolar basal epithelial cells (A549) using selected oxidative stress markers and cytokines: glutathione reductase (GR) and catalase (CAT) activity, total antioxidative capacity (TAC), and malondialdehyde (MDA) concentration, levels of vascular endothelial growing factor (VEGF), tumor necrosis factor-alpha (TNF-α), platelet-derived growth factor-BB (PDGF-BB), and eotaxin. GOS induced higher levels of oxidative stress, measured with CAT activity, TAC, and MDA concentration than GO in both cell lines when compared to control cells. GR activity decreased in time in NHDF cells but increased in A549 cells. The levels of cytokines were related to the exposure time and graphene oxide type in both analyzed cell lines and their levels comparably increased over time. We observed higher TNF-α levels in NHDF and higher levels of VEGF and eotaxin in the A549 cell line. Both types of cells showed similar susceptibility to GO and GOS. We concluded that the short-time exposure to GOS induced the stronger response of oxidative stress markers without collapsing the antioxidative systems of analysed cells. Increased levels of inflammatory cytokines after GO and GOS exposure were similar both in NHDF and A549 cells.

Glycine betaine functionalized graphene oxide as a new engineering nanoparticle lessens salt stress impacts in sweet basil (Ocimum basilicum L.)

Regarding destructive impacts of salinity on different vital processes of plants, many strategies have been developed to alleviate salinity effects. Amongst, nanoparticles (NPs) application has been achieved great attention. For that point, considering positive effects of graphene oxide NPs (GO) and glycine betaine (GB) on different plant processes, GO-GB NPs were primarily synthesized to use GO as a carrier for GB. Then, GO, GB and GO-GB (each in three concentrations; 0, 50 and 100 mg L^-1) were applied on sweet basil (Ocimum basilicum L.) plants under 0, 50 and 100 mM salinity stress conditions. The results demonstrated that GO-GB NPs could lessen negative effects of salinity by enhancing agronomic traits, photosynthetic pigments, chlorophyll fluorescence parameters, membrane stability index (MSI), proline, phenols, antioxidant enzymes activities and dominant constituents of essential oils and decreasing MDA and H₂O₂. These positive effects were more considerable at its lower dose (50 mg L^-1) introducing it as the best treatment to ameliorate sweet basil performance especially essential oil compounds under salt stress. GO application at its higher dose (100 mg L^-1) demonstrated toxicity by negative impacts on the measured parameters. In conclusion, the positive response of sweet basil to GO-GB NPs under non-stress and salt stress conditions cause to consider the NPs as potential novel plant growth promoting and stress protecting agent with innovative outlooks for its use in agriculture.

Graphene oxide exhibited positive effects on the growth of Aloe vera L

There is increasing evidence for graphene associated plant growth promotion, however, the chronic effects of soil-applied graphene remain largely unexplored. The present study investigated the morphological, physiological and biochemical responses of graphene oxide (GO) on Aloe vera L. over the concentration range of 0-100 mg/L for four months. Our results demonstrated that GO, with the best efficiency at 50 mg/L, could enhance the photosynthetic capacity of leaves, increase the yield and morphological characters of root and leaf, improve the nutrient (protein and amino acid) contents of leaf, without reducing the content of the main bioactive compound aloin. Compared with leaves, the effect of GO on root growth was more obvious. Although the electrolyte leakage and MDA content were raised at high concentrations, GO treatment did not increase the root antioxidant enzymes activity or decrease the root vigor, which excluding typical stress response. Furthermore, injection experiments showed that the GO in vivo did not change the plant growth state obviously. Taken together, our study revealed the role of GO in promoting Aloe vera growth by stimulating root growth and photosynthesis, which would provide theory basis for GO application in agriculture and forestry.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-00979-3.

Physico-chemical properties and toxicological effects on plant and algal models of carbon nanosheets from a nettle fibre clone

Carbon nanosheets are two-dimensional nanostructured materials that have applications as energy storage devices, electrochemical sensors, sample supports, filtration membranes, thanks to their high porosity and surface area. Here, for the first time, carbon nanosheets have been prepared from the stems and leaves of a nettle fibre clone, by using a cheap and straight-forward procedure that can be easily scaled up. The nanomaterial shows interesting physical parameters, namely interconnectivity of pores, graphitization, surface area and pore width. These characteristics are similar to those described for the nanomaterials obtained from other fibre crops. However, the advantage of nettle over other plants is its fast growth and easy propagation of homogeneous material using stem cuttings. This last aspect guarantees homogeneity of the starting raw material, a feature that is sought-after to get a nanomaterial with homogeneous and reproducible properties. To evaluate the potential toxic effects if released in the environment, an assessment of the impact on plant reproduction performance and microalgal growth has been carried out by using tobacco pollen cells and the green microalga Pseudokirchneriella subcapitata. No inhibitory effects on pollen germination are recorded, while algal growth inhibition is observed at higher concentrations of leaf carbon nanosheets with lower graphitization degree.

Effects of foliar application of graphene oxide on cadmium uptake by lettuce

Although graphene oxide (GO) has been widely used to enhance soil quality and crop yield, there is currently little information regarding the effects of foliar application of GO on cadmium (Cd) toxicity to plants. In this study, we investigated the response to GO in lettuce cultivated under Cd stress in hydroponic conditions. Lettuce was grown from seeds in a nutrient solution supplemented with 2 mg/L Cd and the leaves were sprayed with 0, 30, and 60 mg/L GO. The results indicated that application of 30 mg/L GO significantly increased the total length, surface area, average diameter, and hair number of lettuce roots, and effectively alleviated the negative effects of Cd on root growth. Furthermore, foliar application of 30 mg/L GO, but not 60 mg/L GO, significantly improved the quality of lettuce, including reduction in Cd accumulation in leaves and roots and increase in soluble sugar, protein, and vitamin C content. Transmission electron microscopy revealed that GO nanoparticles, which entered the leaves and were subsequently transported to the roots via the vascular system (phloem), reduced the damaging effect of Cd on cellular organelles, including the cell wall and membrane, chloroplasts, and starch granules. The effect may be attributed to the absorption of GO by lettuce cells, where it fixed Cd2+, thus reducing Cd2+ bioavailability, or to the improvement of Cd tolerance through regulation of lettuce metabolic pathways. Gaussian simulation analysis revealed that Cd caused significant changes in the GO molecule, resulting in detachment of an epoxy group from the GO carbon ring and breakage of OH bonds in hydroxyl groups, whereupon the oxygen freed from the OH bond formed a new bond with Cd. Collectively, these results indicate that foliar application of 30 mg/L GO can enhance the tolerance of lettuce to Cd, promote plant growth, and improve nutritional quality.

Multiphysical analysis of nanoparticles and their effects on plants

Nanoparticles are the magic bullets and at the leading edge in the field of nanotechnology, and their unique properties make these materials indispensable and superior in many areas, including the electronic field. Extensive applications of nanomaterials are incontrovertibly entering our living system. The increasing use of nanomaterials into the ecosystem is one of the crucial environmental factors that human being is facing. Nanomaterials raise noticeable toxicological concerns; particularly their accumulation in plants and the resultant toxicity may affect the food chain. Here, we analyzed the characterization of nanomaterials, such as graphene, Al₂ O₃ , TiO₂ , and semi-insulating or conducting nanoparticles. Quantitative evaluation of the nanomaterials was conducted and their commercialization aspects were discussed. Various characterization techniques, scanning electron microscopy, X-ray diffraction, and ultraviolet rays were utilized to identify the morphology, phase, absorbance, and crystallinity. In addition, we analyzed the effects of nanomaterials on plants. The toxicity of nanoparticles has severe effects on loss of morphology of the plants. Potential mechanisms including physical and physiological effects were analyzed. In future studies, it is indispensable to assess widely accepted toxicity evaluation for safe production and use of nanomaterials.

Guiding the design space for nanotechnology to advance sustainable crop production

The globally recognized need to advance more sustainable agriculture and food systems has motivated the emergence of transdisciplinary solutions, which include methodologies that utilize the properties of materials at the nanoscale to address extensive and inefficient resource use. Despite the promising prospects of these nanoscale materials, the potential for large-scale applications directly to the environment and to crops necessitates precautionary measures to avoid unintended consequences. Further, the effects of using engineered nanomaterials (ENMs) in agricultural practices cascade throughout their life cycle and include effects from upstream-embodied resources and emissions from ENM production as well as their potential downstream environmental implications. Building on decades-long research in ENM synthesis, biological and environmental interactions, fate, transport and transformation, there is the opportunity to inform the sustainable design of nano-enabled agrochemicals. Here we perform a screening-level analysis that considers the system-wide benefits and costs for opportunities in which ENMs can advance the sustainability of crop-based agriculture. These include their on-farm use as (1) soil amendments to offset nitrogen fertilizer inputs, (2) seed coatings to increase germination rates and (3) foliar sprays to enhance yields. In each analysis, the nano-enabled alternatives are compared against the current practice on the basis of performance and embodied energy. In addition to identifying the ENM compositions and application approaches with the greatest potential to sustainably advance crop production, we present a holistic, prospective, systems-based approach that promotes emerging alternatives that have net performance and environmental benefits.

Foliar graphene oxide treatment increases photosynthetic capacity and reduces oxidative stress in cadmium-stressed lettuce

The application of graphene oxide (GO) in the environment can have a positive or negative effect on the toxicity of pollutants, but the effect of GO on cadmium (Cd2+)-stressed lettuce has not yet been thoroughly studied. Therefore, we assessed the potential effects of foliar GO sprays on photosynthesis and antioxidant systems in Cd-stressed lettuce. We found that the foliar application of 30 mg L-1 of GO could significantly reduce signs of Cd2+ toxicity in lettuce. We observed increased net photosynthetic rates, stomatal conductance, transpiration rates, chlorophyll content, primary maximum photochemical efficiency of photosystem II, actual quantum yield, photosynthetic electron transport rates, ribulose-1,5-bisphosphate carboxylase and oxygenase concentrations, and biomass in Cd2+-stressed lettuce treated with GO. In addition, the foliar application of 30 mg L-1 of GO reduced the accumulation of the reactive oxygen species O·̄2 and H2O2, malondialdehyde content, and the activity of antioxidant enzymes. The decreased antioxidant enzyme activity could have been due to the decrease in reactive oxygen species. Cd2+ pollution is highly destructive to agricultural products, and the foliar application of GO provides a new potential tactic to improve the tolerance of plants to heavy metals.

Nanoparticles in Agroindustry: Applications, Toxicity, Challenges, and Trends

Nanotechnology is a tool that in the last decade has demonstrated multiple applications in several sectors, including agroindustry. There has been an advance in the development of nanoparticulated systems to be used as fertilizers, pesticides, herbicides, sensors, and quality stimulants, among other applications. The nanoencapsulation process not only protects the active ingredient but also can affect the diffusion, interaction, and activity. It is important to evaluate the negative aspects of the use of nanoparticles (NPs) in agriculture. Given the high impact of the nanoparticulated systems in the agro-industrial field, this review aims to address the effects of various nanomaterials on the morphology, metabolomics, and genetic modification of several crops.

Effect of Graphene Oxide on Growth of Wheat Seedlings: Insights from Oxidative Stress and Physiological Flux

In this study, the responses of wheat seedlings to graphene oxide (GO) were investigated at a wide concentration range of 0-1000 mg L^-1, including oxidative stress, real-time membrane potential as well as proton and calcium ion fluxes. The results show that GO induced a hormesis effect on root growth (low concentration (100 mg L^-1) promotion and high concentration (1000 mg L^-1) inhibition. Oxidative stress was responsible for the growth inhibition at GO concentration of 1000 mg L^-1, as suggested from great stimulation in the activities of antioxidant enzymes and MDA content in roots or leaves. Superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activities were highly correlated with MDA levels (r² = 0.963, 0.984, and 0.960, respectively). GO exposure caused significant concentration-dependent membrane depolarization in roots, and significantly inhibited H⁺ efflux and extracellular Ca²⁺ influx in root cap.

Graphene oxide exposure suppresses nitrate uptake by roots of wheat seedlings

Despite the large number of studies reporting the phytotoxicity of graphene-based materials, the effects of these materials on nutrient uptake in plants remain unclear. The present study showed that nitrate concentrations were significantly decreased in the roots of wheat plants treated with graphene oxide (GO) at 200-800 mg L^-1. Non-invasive microelectrode measurement demonstrated that GO could significantly inhibit the net NO₃^- influx in the meristematic, elongation, and mature zones of wheat roots. Further analysis indicated that GO could be trapped in the root vacuoles, and that the maximal root length and the number of lateral roots were significantly reduced. Additionally, root tip whitening, creases, oxidative stress, and weakened respiration were observed. These observations indicate that GO is highly unfavorable for vigorous root growth and inhibits increase in root uptake area. At the molecular level, GO exposure caused DNA damage and inhibited the expression of most nitrate transporters (NRTs) in wheat roots, with the most significantly downregulated genes being NRT1.3, NRT1.5, NRT2.1, NRT2.3, and NRT2.4. We concluded that GO exposure decreased the root uptake area and root activity, and decreased the expression of NRTs, which may have consequently suppressed the NO₃^- uptake rate, leading to adverse nitrate accumulation in stressed plants.

Carbon family nanomaterials — new applications and technologies

Research on carbon-based nanomaterials (CBNMs) and their development is one of the major scientific disciplines of the last century. This is mainly because of their unique properties which can lead to improvements in industrial technology or new medical applications. Therefore, it is necessary to examine their properties such as shape, size, chemical composition, density, toxicity, etc. This article focuses on the general characteristics of nanomaterials (NMs) and their behavior when entering the environment (water and soil). In addition, it presents individual members of the graphene family including porous ecological carbon (biochar). The article mainly deals with the new potential technologies of CBNMs considering their possible toxic and genotoxic effects. This review also highlights the latest developments in the application of self-propelled micromotors for green chemistry applications. Finally, it points to the potential biomedical applications of CBNMs.

Graphene oxide enters the rice roots and disturbs the endophytic bacterial communities

The environmental release of graphene oxide (GO) will certainly induce the GO exposure to plants. To date, the influence of GO on the intracellular structures and the endophytic bacterial ecology of plants have been rarely reported. In the present study, the rice seedlings were exposed to GO (5 mg/L) under hydroponic condition for fifteen days with periodic stir. The cellular structures damage, GO deposition and oxidative stress were found in rice root after GO exposure. A Illumina analysis based on the bacterial 16 S rRNA gene showed that the richness, evenness and diversity of endophytic bacterial communities of rice root decreased due to GO exposure. The relative abundance of beneficial endophytic bacterial populations decreased after GO exposure. Out of potential phenotypes predicted by BugBase, the relative abundance of Gram negative, stress-tolerant and biofilm-forming phenotypes, presented an increase trend after GO exposure.

Untargeted Metabolic Pathway Analysis as an Effective Strategy to Connect Various Nanoparticle Properties to Nanoparticle-Induced Ecotoxicity

Elucidation of the relationships between nanoparticle properties and ecotoxicity is a fundamental issue for environmental applications and risk assessment of nanoparticles. However, effective strategies to connect the various properties of nanoparticles with their ecotoxicity remain largely unavailable. Herein, an untargeted metabolic pathway analysis was employed to investigate the environmental risk posed by 10 typical nanoparticles (AgNPs, CuNPs, FeNPs, ZnONPs, SiO₂NPs, TiO₂NPs, GO, GOQDs, SWCNTs, and C₆₀) to rice (a staple food for half of the world's population). Downregulation of carbohydrate metabolism and upregulation of amino acid metabolism were the two dominant metabolic effects induced by all tested nanoparticles. Partial least-squares regression analysis indicated that a zerovalent metal and high specific surface area positively contributed to the downregulation of carbohydrate metabolism, indicating strong abiotic stress. In contrast, the carbon type, the presence of a spherical or sheet shape, and the absence of oxygen functional groups in the nanoparticles positively contributed to the upregulation of amino acid metabolism, indicating adaptation to abiotic stress. Moreover, network relationships among five properties of nanoparticles were established for these metabolic pathways. The results of the present study will aid in the understanding and prediction of environmental risks and in the design of environmentally friendly nanoparticles.

Effects of silver-graphene oxide on seed germination and early growth of crop species

Due to its excellent material properties, silver-graphene oxide (Ag-GO) is being studied for diverse applications, such as antimicrobial agents, catalysts and absorbents. Such use of Ag-GO may lead to its release into terrestrial ecosystems, but little is known about the impact of Ag-GO on plants. In the present study, we determined the effects of Ag-GO on seed germination and early growth of crop species by analyzing the germination rate, growth of roots and shoots, hydrogen peroxide (H₂O₂) accumulation, and the uptake of Ag in alfalfa, radish and cucumber treated with 0.2–1.6 mg mL⁻¹ of Ag-GO. Ag-GO treatment increased the shoot growth of radish at 0.2–1.6 mg mL⁻¹ but decreased that of cucumber at 0.8 mg mL⁻¹. In addition, Ag-GO enhanced the root elongation of radish at 0.2 mg mL⁻¹ but inhibited that of alfalfa at 0.2, 0.8 and 1.6 mg mL⁻¹. Ag-GO treatment induced H₂O₂ production in alfalfa, radish and cucumber in a concentration-dependent manner. Larger amounts of Ag accumulated in the seedlings as the concentration of Ag-GO increased, and such accumulation suggests that Ag may be transferred to higher trophic levels when plants are exposed to Ag-GO in ecosystems. Our study can, thus, serve as an important basis for setting guidelines for the release of nanomaterials into the environment.

Effects of biochar nanoparticles on seed germination and seedling growth

As a soil amendment, the prospect of biochar application is excellent. However, environmental risks of biochar need to be investigated for its substantial use. The environmental risks of BNPs need urgent attention because at present little knowledge is available. Therefore, the effects of six types of BNPs on seed germination and growth of rice, tomato and reed seedlings were investigated. The BNPs were collected from biochars derived from two feedstocks (rice straw and wood sawdust) under 300 °C (low-temperature), 500 °C (mid-temperature) and 700 °C (high-temperature). The BNPs collected from high-temperature biochar inhibited seed germination of rice. However, all of the BNPs had a stimulating effect on rice seedling growth that significantly increasing the length of its root and shoot. Furthermore, the BNPs collected from high-temperature biochar and lignin-rich feedstock had an inhibiting effect on reed that dramatically decreased shoot length and biomass. Inhibitory effects of BNPs were caused not only by phenolic compounds on its surface, but also by the blocking effect on epidermal openings resulting in a reduced transfer of nutrients and water. No evidence was found that BNPs would affect the seed gemination and seedling growth of tomato plants. This study indicates that the eco-toxicity of BNPs is a potential environmental risk of biochar. Our findings provide new evidence for the necessity of establishing environmental risk management of biochar.

Impact of Carbon Nanomaterials on the Antioxidant System of Tomato Seedlings

Tomato is one of the most economically important vegetables worldwide and is constantly threatened by various biotic and abiotic stress factors reducing the quality and quantity in the production of this crop. As an alternative to mitigate stress in plants, carbon nanomaterials (CNMs) have been used in agricultural areas. Therefore, the objective of the present work was to evaluate the antioxidant responses of tomato seedlings to the application via foliar and drench of carbon nanotubes (CNTs) and graphene (GP). Different doses (10, 50, 100, 250, 500, and 1000 mg L-1) and a control were evaluated. The results showed that the fresh and dry root weight increased with the application of CNMs. Regarding the antioxidant responses of tomato seedlings, the application of CNMs increased the content of phenols, flavonoids, ascorbic acid, glutathione, photosynthetic pigments, activity of the enzyme's ascorbate peroxidase, glutathione peroxidase, catalase, and phenylalanine ammonia lyase as well as the content of proteins. Therefore, the use of carbon-based nanomaterials could be a good alternative to induce tolerance to different stress in tomato crop.

Graphene oxide effects in early ontogenetic stages of Triticum aestivum L. seedlings

Nanomaterials are being used increasingly in various areas such as electronic devices manufacture, medicine, mechanical devices production, and even food industry. Therefore, the evaluation of their toxicity is mandatory. Graphene oxide (GO) has been shown to have both positive as well as negative impact on different crop plants, depending on species, dose, and duration of exposure. The current study evaluated the impact of GO sheets at different concentrations (500, 1000 and 2000 mg/L) on physiological, biochemical and genetic levels to determine the possible toxic action. Wheat caryopses were treated with GO for 48 h and 7 days. The germination rate and roots elongation decreased in a dose-response manner, except the sample treated with GO at a concentration of 1000 mg/L. Mitotic index has ascendant trend; its increase may be due to the accumulation of prophases GO induced significant accumulation of the cells with aberrations, their presence suggests a clastogenic/aneugenic effect of these carbon nanomaterials. Regarding enzymatic and non-enzymatic antioxidant system defence, the activity varied depending on the dose of GO. Thus, chlorophyll a pigments content decreased significantly at high dose (2000 mg/L), while the carotenoid pigments had lower content at 500 mg/L of GO, and no statistical difference encountered in case of chlorophyll b amount. The antioxidant enzyme activity (CAT, POD, and SOD) was higher at low dose of GO, indicating the presence of oxidative stress generated as a response to the GO treatment. Also, the free radical scavenging activity of the polyphenolic compounds was enhanced upon GO exposure. The GO accumulation has been identified by transmission electron microscopy only at plumules level, near the intercellular space.

Physiological and antioxidative responses to GO/PANI nanocomposite in intact and demucilaged seeds and young seedlings of Salvia mirzayanii

The current study aimed to investigate the impacts of different concentrations of GO/PANI nanocomposites (25, 50 and 100 mg L^-1), in comparison with GO and PANI, on seed germination behaviors, morpho-physiological and biochemical traits in intact (mucilaginous) and demucilaged seeds, and young seedlings of the medicinal plant Salvia mirzayanii. Upon exposure to GO, seed germination was delayed and reduced, and growth attributes (root and shoot length, shoot fresh weight, and total chlorophyll content) declined, all of which could be attributed to the reductions in water uptake and oxidative stress particularly in demucilaged seeds. A hormetic dose-dependent response was observed for the growth traits in both intact and demucilaged seedlings upon exposure to GO/PANI concentrations, i.e. low-concentration stimulation and high-concentration repression. Elevated levels of H₂O₂ in shoot tissue of the seedlings exposed to GO and high concentration of GO/PANI, in comparison with those exposed to low levels of GO/PANI and control, were linked with the activities of the antioxidant enzymes SOD, CAT, POD, and total phenolics. Overall, the results showed high toxicity of GO on germination and early growth of S. mirzayani that was more evident in demucilaged seedlings, whereas GO/PANI stimulated germination, and the effects on seedling growth were stimulatory or inhibitory depending on the application dose and presence of mucilage. Furthermore, the capacity of GO/PANI nanocomposites to improve germination and cause a regular porosity pattern in roots accompanied by improved water uptake and early establishment of S. mirzayanii propose potential implications of GO/PANI nanocomposites for seeds/plants in drought-prone ecosystems.

Ecotoxicity and genotoxicity of polystyrene microplastics on higher plant Vicia faba

Nano- and microplastics have been widely spread in environmental matrices, especially in marine and terrestrial systems. In this study, higher plant Vicia faba root tips were exposed to 5 μm and 100 nm with 10, 50 and 100 mg/L polystyrene fluorescent microplastics (PS-MPs) for 48 h. Root length, weight, oxidative stress and genotoxicity of V. faba were assessed to investigate toxic effects of PS-MPs. The results showed that the biomass and catalase (CAT) enzymes activity of V. faba roots decreased under 5 μm PS-MPs whereas superoxide dismutase (SOD) and peroxidase (POD) enzymes activity significantly increased. Under the 100 nm PS-MPs exposure a significant decrease of growth was observed only at the highest concentration (100 mg/L). However, micronucleus (MN) test and antioxidative enzymes activities showed that 100 nm PS-MPs induce higher genotoxic and oxidative damage to V. faba than 5 μm PS-MPs. Furthermore, the laser confocal scanning microscopy (LCSM) demonstrated that 100 nm PS-MPs can accumulate in V. faba root and most probably block cell connections or cell wall pores for transport of nutrients. These findings provide a new insight into the toxic effects of microplastics on V. faba, and further apply to the ecological risk assessment of microplastics on higher plants.

Applications of carbon nanomaterials in the plant system: A perspective view on the pros and cons

With the remarkable development in the field of nanotechnology, carbon-based nanomaterials (CNMs) have been widely used for numerous applications in different areas of the plant system. The current understanding about the CNMs' accumulation, translocation, plant growth responses, and stress modulations in the plant system is far from complete. There have been relentless efforts by the researchers worldwide in order to acquire newer insights into the plant-CNMs interactions and the consequences. The present review intends to update the reader with the status of the impacts of the different CNMs on plant growth. Research reports from the plant biotechnologists have documented mixed effects (which are dependent on CNMs' concentration) of the CNMs' exposure on plants ranging from enhanced crop yield to acute cytotoxicity. The growth and yield pattern vary from species to species and are dependent on the dosage of the CNMs applied. Studies found an increase in vegetative growth and yield of fruit/seed at lower concentration of CNMs, but a decrease in these observables were also noted when higher concentrations of CNMs were used. In general, at lower concentrations, CNMs were found to be effective in enhancing (water uptake, water transport, seed germination, nitrogenase, photosystem and antioxidant activities), activating (water channels proteins) and promoting (nutrition absorption); all these change when concentrations are raised. All these aspects have been reviewed thoroughly in this article, with a focus on the recent updates on the role of the CNMs in augmenting or retarding plant growth. Sections have been devoted to the various features of the CNMs and their roles in inducing plant growth, phytotoxic responses of the plants and overall crop improvement. Concluding remarks have been added to propose future directions of research on the CNMs-plant interactions and also to sound a warning on the use of CNMs in agriculture.