Responses of wheat (Triticum aestivum) plants grown in a Cd contaminated soil to the application of iron oxide nanoparticles

Zinc Oxide Nanoparticles and Their Biosynthesis: Overview

Zinc (Zn) is plant micronutrient, which is involved in many physiological functions, and an inadequate supply will reduce crop yields. Its deficiency is the widest spread micronutrient deficiency problem; almost all crops and calcareous, sandy soils, as well as peat soils and soils with high phosphorus and silicon content are expected to be deficient. In addition, Zn is essential for growth in animals, human beings, and plants; it is vital to crop nutrition as it is required in various enzymatic reactions, metabolic processes, and oxidation reduction reactions. Finally, there is a lot of attention on the Zn nanoparticles (NPs) due to our understanding of different forms of Zn, as well as its uptake and integration in the plants, which could be the primary step toward the larger use of NPs of Zn in agriculture. Nanotechnology application in agriculture has been increasing over recent years and constitutes a valuable tool in reaching the goal of sustainable food production worldwide. A wide array of nanomaterials has been used to develop strategies of delivery of bioactive compounds aimed at boosting the production and protection of crops. ZnO-NPs, a multifunctional material with distinct properties and their doped counterparts, were widely being studied in different fields of science. However, its application in environmental waste treatment and many other managements, such as remediation, is starting to gain attention due to its low cost and high productivity. Nano-agrochemicals are a combination of nanotechnology with agrochemicals that have resulted in nano-fertilizers, nano-herbicides, nano-fungicides, nano-pesticides, and nano-insecticides being developed. They have anti-bacterial, anti-fungal, anti-inflammatory, antioxidant, and optical capabilities. Green approaches using plants, fungi, bacteria, and algae have been implemented due to the high rate of harmful chemicals and severe situations used in the manufacturing of the NPs. This review summarizes the data on Zn interaction with plants and contributes towards the knowledge of Zn NPs and its impact on plants.

Application of Exogenous Iron Alters the Microbial Community Structure and Reduces the Accumulation of Cadmium and Arsenic in Rice (Oryza sativa L.)

Cadmium (Cd) and arsenic (As) contamination of soil has been a public concern due to their potential accumulation risk through the food chain. This study was conducted to investigate the performance of ferrous sulfate (FeSO4) and ferric oxide (Fe2O3) nanoparticle (Nano-Fe) to stabilize the concentrations of Cd and As in paddy soil. Both Fe treatments led to low extractable Cd and the contents of specifically sorbed As contents, increased (p < 0.05) the Shannon index and decreased (p < 0.05) the Simpson diversity indices compared with the control. Nano-Fe increased the relative abundances of Firmicutes and Proteobacteria and decreased the abundances of Acidobacteria and Chloroflexi. Moreover, the addition of both forms of Fe promoted the formation of Fe plaque and decreased the translocation factor index (TFs) root/soil, TFs shoot/root, and TFs grain/shoot of Cd and As. These results suggest that exogenous Fe may modify the microbial community and decrease the soil available Cd and As contents, inhibit the absorption of Cd and As by the roots and decrease the transport of Cd and As in rice grains and the risk intake in humans. These findings demonstrate that soil amendment with exogenous Fe, particularly Nano-Fe, is a potential approach to simultaneously remediate the accumulation of Cd and As from the soil to rice grain systems.

Nano-Fe2O3 as a tool to restore plant growth in contaminated soils - Assessment of potentially toxic elements (bio)availability and redox homeostasis in Hordeum vulgare L

This work aimed to evaluate the potential of Fe₂O₃ nanoparticles (nano-Fe₂O₃) to alleviate potentially toxic elements (PTEs) - induced stress in barley plants (Hordeum vulgare L.), focusing on bioaccumulation patterns and on plant growth and redox homeostasis. To achieve this goal, plants grew in two agricultural soils, contaminated by different levels of PTEs, collected from an industrial area, previously amended, or not, with 1% (w/w) nano-Fe₂O₃. After 14 d of growth, biometric parameters were evaluated, along with the analysis of PTEs bioaccumulation and biochemical endpoints. After exposure to contaminated soils, plant development was greatly affected, as evidenced by significant decreases in root length and biomass production. However, upon co-treatment with nano-Fe₂O₃, lower inhibitory effects on biometric parameters were observed. Regarding the oxidative damage, both soils led to increases in lipid peroxidation and superoxide anion concentration, though hydrogen peroxide levels were only increased in the most contaminated soil. In general, these changes in the oxidative stress markers were accompanied by an upregulation of different antioxidant mechanisms, whose efficiency was even more powerful upon soil amendment with nano-Fe₂O₃, thus lowering PTEs-induced oxidative damage. Altogether, the present study revealed that nano-Fe₂O₃ can protect the growth of barley plants under contaminated soils.

Antifungal Potential of Green Synthesized Magnetite Nanoparticles Black Coffee-Magnetite Nanoparticles Against Wilt Infection by Ameliorating Enzymatic Activity and Gene Expression in Solanum lycopersicum L

Tomato plants are prone to various biotic and abiotic stresses. Fusarium wilt is one of the most devasting diseases of tomatoes caused by Fusarium oxysporum f. sp. lycopersici, causing high yield and economic losses annually. Magnetite nanoparticles (Fe3O4 NPs) are one of the potent candidates to inhibit fungal infection by improving plant growth parameters. Spinach has been used as a starting material to synthesize green-synthesized iron oxide nanoparticles (IONPs). Various extracts, i.e., pomegranate juice, white vinegar, pomegranate peel, black coffee (BC), aloe vera peel, and aspirin, had been used as reducing/stabilizing agents to tune the properties of the Fe3O4 NPs. After utilizing spinach as a precursor and BC as a reducing agent, the X-ray diffraction (XRD) pattern showed cubic magnetite (Fe3O4) phase. Spherical-shaped nanoparticles (∼20 nm) with superparamagnetic nature indicated by scanning electron microscopy (SEM) monographs, whereas energy-dispersive X-ray gives good elemental composition in Fe3O4 NPs. A characteristic band of Fe-O at ∼ 561 cm-1 was exhibited by the Fourier transform infrared (FTIR) spectrum. X-ray photoelectron spectroscopy (XPS) results confirmed the binding energies of Fe 2p3/2 (∼710.9 eV) and Fe 2p1/2 (∼724.5 eV) while, Raman bands at ∼310 cm-1 (T2 g ), ∼550 cm-1 (T2 g ), and 670 cm-1 (A1 g ) indicated the formation of Fe3O4 NPs synthesized using BC extract. The in vitro activity of BC-Fe3O4 NPs significantly inhibited the mycelial growth of F. oxysporum both at the third and seventh day after incubation, in a dose-dependent manner. In vivo studies also exhibited a substantial reduction in disease severity and incidence by improving plant growth parameters after treatment with different concentrations of BC-Fe3O4 NPs. The increasing tendency in enzymatic activities had been measured after treatment with different concentrations of NPs both in roots and shoot of tomato plants as compared to the control. Correspondingly, the upregulation of PR-proteins and defense genes are in line with the results of the enzymatic activities. The outcome of the present findings suggests that Fe3O4 NPs has the potential to control wilt infection by enhancing plant growth. Hence, Fe3O4 NPs, being non-phytotoxic, have impending scope in the agriculture sector to attain higher yield by managing plant diseases.

Effects of exogenous additives on wheat Cd accumulation, soil Cd availability and physicochemical properties in Cd-contaminated agricultural soils: A meta-analysis

Cadmium (Cd) contamination in wheat is a serious issue. The application of exogenous additives can effectively inhibit Cd bioavailability in soil and decrease Cd accumulation in wheat. However, a comprehensive and quantitative analysis of how additives affect wheat Cd accumulation, wheat yield, soil Cd availability, and soil properties is lacking. We conducted a meta-analysis of 65 peer-reviewed papers published before April 2021 to investigate how additives application affects Cd accumulation in wheat and soil Cd availability. The results indicated that most additives application decreased the diethylenetriaminepentaacetic acid extractable-Cd content (5.27-56.33%) in the soil, and wheat grain and root Cd concentrations (0.03-129.87% and 0.42-52.84%, respectively); the pH values of wheat-grown soil and the properties of the additives affected the reduction percentage. Overall, most wheat-grown soils were calcareous soil (42 peer-reviewed papers); in calcareous soil, the magnitude of the Cd reduction in wheat grain was the highest under treatments with clay minerals (129.87%) due to clay modification, followed by composite (75.36%) and phosphorus materials (73.55%). Moreover, most additives application increased wheat grain yield by 0.03-51.84%, which was attributed to the positive effects of additives on wheat antioxidant capacity, photosynthesis, respiration, and nutrient uptake. Additives application increased the pH value of acidic wheat soil, and positively affected the electrical conductivity, cation exchange capacity, and organic carbon content of the wheat grown soil. In addition, regression analysis showed that soil available Cd was negatively correlated with the pH value with additives application in acidic soil (r² = 0.43), while a non-significant correlation was observed in neutral and calcareous wheat soils (r² = 0.017 and 0.016, respectively). The results of this study can assist in the selection, modification, and utilisation of additives to remediate Cd-contaminated wheat soils.

Biofortification-A Frontier Novel Approach to Enrich Micronutrients in Field Crops to Encounter the Nutritional Security

Globally, many developing countries are facing silent epidemics of nutritional deficiencies in human beings and animals. The lack of diversity in diet, i.e., cereal-based crops deficient in mineral nutrients is an additional threat to nutritional quality. The present review accounts for the significance of biofortification as a process to enhance the productivity of crops and also an agricultural solution to address the issues of nutritional security. In this endeavor, different innovative and specific biofortification approaches have been discussed for nutrient enrichment of field crops including cereals, pulses, oilseeds and fodder crops. The agronomic approach increases the micronutrient density in crops with soil and foliar application of fertilizers including amendments. The biofortification through conventional breeding approach includes the selection of efficient genotypes, practicing crossing of plants with desirable nutritional traits without sacrificing agricultural and economic productivity. However, the transgenic/biotechnological approach involves the synthesis of transgenes for micronutrient re-translocation between tissues to enhance their bioavailability. Soil microorganisms enhance nutrient content in the rhizosphere through diverse mechanisms such as synthesis, mobilization, transformations and siderophore production which accumulate more minerals in plants. Different sources of micronutrients viz. mineral solutions, chelates and nanoparticles play a pivotal role in the process of biofortification as it regulates the absorption rates and mechanisms in plants. Apart from the quality parameters, biofortification also improved the crop yield to alleviate hidden hunger thus proving to be a sustainable and cost-effective approach. Thus, this review article conveys a message for researchers about the adequate potential of biofortification to increase crop productivity and nourish the crop with additional nutrient content to provide food security and nutritional quality to humans and livestock.

Seed priming with zinc oxide nanoparticles downplayed ultrastructural damage and improved photosynthetic apparatus in maize under cobalt stress

It is widely known that cobalt (Co) stress adversely affects plant growth and biomass accumulation, posing serious threats to crop production and food security. Nanotechnology is an emerging field in crop sciences for its potential in improving crop production and mitigating various stresses. Although there have been several studies reporting the toxic effects of zinc oxide nanoparticles (ZnO NPs) on different crops, their role in ameliorating heavy metal toxicity are still poorly understood. This study aimed to investigate the beneficial effects of seed priming with ZnO NPs in mitigating the phytotoxicity induced by Co stress. Our results demonstrated that ZnO NPs significantly improved the plant growth, biomass, and photosynthetic machinery in maize under Co stress. The NPs priming reduced ROS and MDA accumulations in maize shoots. More importantly, ZnO NPs alleviated the toxic effects of Co by decreasing its uptake and conferred stability to plant ultra-cellular structures and photosynthetic apparatus. Furthermore, a higher accumulation of nutrient content and antioxidant enzymes were found in NPs-primed seedlings. Collectively, we provide first evidence to demonstrate the alleviation of Co toxicity via ZnO NPs seed priming in maize, thus, illustrating the potential role of ZnO NPs to be applied as a stress mitigation agent for the crops grown in Co contaminated areas to enhance crop growth and yield.

The dichotomy of nanotechnology as the cutting edge of agriculture: Nano-farming as an asset versus nanotoxicity

The unprecedented setbacks and environmental complications, faced by global agro-farming industry, have led to the advent of nanotechnology in agriculture, which has been recognized as a novel and innovative approach in development of sustainable farming practices. The agricultural regimen is the "head honcho" of the world, however presently certain approaches have been imposing grave danger to the environment and human civilization. The nano-farming paradigm has successfully elevated the growth and development of plants, parallel to the production, quality, germination/transpiration index, photosynthetic machinery, genetic progression, and so on. This has optimized the traditional farming into precision farming, utilising nano-based sensors and nanobionics, smart delivery tools, nanotech facets in plant disease management, nanofertilizers, enhancement of plant adaptive potential to external stress, role in bioenergy conservation and so on. These applications portray nanorevolution as "the big cheese" of global agriculture, mitigating the bottlenecks of conventional practices. Besides the applications of nanotechnology, the review identifies the limitations, like possible harmful impact on environment, mankind and plants, as the "Achilles heel" in agro-industry, aiming to establish its defined role in agriculture, while simultaneously considering the risks, in order to resolve them, thus abiding by "technology-yes, but safety-must". The authors aim to provide a significant opportunity to the nanotech researchers, Botanists and environmentalists, to promote judicial use of nanoparticles and establish a secure and safe environment.

Sustainable synthesis of microwave-assisted IONPs using Spinacia oleracea L. for control of fungal wilt by modulating the defense system in tomato plants

BACKGROUND

Changing climate enhances the survival of pests and pathogens, which eventually affects crop yield and reduces its economic value. Novel approaches should be employed to ensure sustainable food security. Nano-based agri-chemicals provide a distinctive mechanism to increase productivity and manage phytopathogens, with minimal environmental distress. In vitro and in greenhouse studies were conducted to evaluate the potential of green-synthesized iron-oxide nanoparticles (IONPs) in suppressing wilt infection caused by Fusarium oxysporum f. sp. lycospersici, and improving tomato growth (Solanum lycopersicum) and fruit quality.

RESULTS

Various microwave powers (100-1000 W) were used to modulate the properties of the green-synthesized IONPs, using spinach as a starting material. The IONPs stabilized with black coffee extract were substantively characterized using X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy, dielectric and impedance spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy (SEM and TEM, respectively), and magnetization analysis. XRD revealed a cubic magnetite (Fe3O4) phase with super-paramagnetic nature, detected at all microwave powers. The binding energies of Fe 2p3/2 (710.9 eV) and Fe 2p1/2 (724.5 eV) of Fe3O4 NPs were confirmed using XPS analysis at a microwave power of 1000 W. Uniform, spherical/cubical-shaped particles with an average diameter of 4 nm were confirmed using SEM and TEM analysis. A significant reduction in mycelial growth and spore germination was observed upon exposure to different IONP treatments. Malformed mycelium, DNA fragmentation, alternation in the cell membrane, and ROS production in F. oxysporum indicated the anti-microbial potential of the IONPs. The particles were applied both through the root (before transplantation) and by means of foliar application (after two weeks) to the infected seedlings. IONPs significantly reduced disease severity by an average of 47.8%, resulting in increased plant growth variables after exposure to 12.5 µg/mL of IONPs. Analysis of photosynthetic pigments, phenolic compounds, and anti-oxidant enzymes in the roots and shoots showed an increasing trend after exposure to various concentrations of IONPs. Correspondingly, lycopene, vitamin C, total flavonoids, and protein content were substantially improved in tomato fruits after treatment with IONPs.

CONCLUSION

The findings of the current investigation suggested that the synthesized IONPs display anti-fungal and nutritional properties that can help to manage Fusarium wilt disease, resulting in enhanced plant growth and fruit quality.

Recent Advancements and Development in Nano-Enabled Agriculture for Improving Abiotic Stress Tolerance in Plants

Abiotic stresses, such as heavy metals (HMs), drought, salinity and water logging, are the foremost limiting factors that adversely affect the plant growth and crop productivity worldwide. The plants respond to such stresses by activating a series of intricate mechanisms that subsequently alter the morpho-physiological and biochemical processes. Over the past few decades, abiotic stresses in plants have been managed through marker-assisted breeding, conventional breeding, and genetic engineering approaches. With technological advancement, efficient strategies are required to cope with the harmful effects of abiotic environmental constraints to develop sustainable agriculture systems of crop production. Recently, nanotechnology has emerged as an attractive area of study with potential applications in the agricultural science, including mitigating the impacts of climate change, increasing nutrient utilization efficiency and abiotic stress management. Nanoparticles (NPs), as nanofertilizers, have gained significant attention due to their high surface area to volume ratio, eco-friendly nature, low cost, unique physicochemical properties, and improved plant productivity. Several studies have revealed the potential role of NPs in abiotic stress management. This review aims to emphasize the role of NPs in managing abiotic stresses and growth promotion to develop a cost-effective and environment friendly strategy for the future agricultural sustainability.

Gamma radiation-induced synthesis of a novel chitosan/silver/Mn-Mg ferrite nanocomposite and its impact on cadmium accumulation and translocation in brassica plant growth

Herein, a novel chitosan/silver/Mn_0.5Mg_0.5Fe₂O₄ (Cs/Ag/MnMgFe₂O₄) nanocomposite was synthesized with gamma irradiation assistant. The prepared Cs/Ag/MnMgFe₂O₄ nanocomposite was characterized via EDX, XRD, SEM, UV-vis spectroscopy. To evaluate the effects of soak low and high-dose nanocomposite on physiological parameters, photosynthetic pigments, antioxidant and non-antioxidant enzymes of cabbage under Cd stress, a factorial experiment was conducted based on CRD with five replications. The Cd stress decreased the morphological characteristics and photosynthetic pigments while increasing cabbage's antioxidant and non-antioxidant enzymes. The application of low and high-dose of nanocomposite decreased Cd content in leaves by about 42.86%, 60.48%, and the root by approximately 18.72%, 28.72%, respectively, and translocation factors and tolerance index, H₂O₂, O₂, and malondialdehyde. In contrast, the application of high of the nanocomposite increased the values of SPAD chlorophyll about 27.50%, stomatal conductance about 87.18%, net photosynthetic rate about 44.90%, intercellular CO₂ concentration about 32.00%, and transpiration rate about 85.20%, as compared to Cd stress. Furthermore, the application of low and high-dose Cs/Ag/MnMgFe₂O₄ nanocomposite enhances the antioxidant and non-antioxidant enzymes of the cabbage plant compared to Cd stress. Generally, it was conducted that Cs/Ag/MnMgFe₂O₄ nanocomposite can be used as a proper tool for increasing cabbage plants under Cd stress.

Explicating the cross-talks between nanoparticles, signaling pathways and nutrient homeostasis during environmental stresses and xenobiotic toxicity for sustainable cultivation of cereals

Precision farming using nanoparticles is a cutting-edge technology for safe cultivation of crop plants in marginal areas afflicted with environmental/climatic stresses like salinity, drought, extremes of temperature, ultraviolet B stress or polluted with xenobiotics like toxic heavy metals and fluoride. Major cereal crops like rice, wheat, maize, barley, sorghum and millets which provide the staple food for the entire global population are mainly glycophytes and are extremely susceptible to abiotic stress-induced oxidative injuries. Nanofertilization/exogenous spraying of beneficial nanoparticles alleviates the oxidative damages in cereals by altering the homeostasis of phytohormones like abscisic acid, gibberellins, cytokinins, auxins, salicylic acid, jasmonic acid and melatonin and by triggering the synthesis of gasotransmitter nitric oxide. Signaling cross-talks of nanoparticles with plant growth regulators enable activation of the defence machinery, comprising of antioxidants, thiol-rich compounds and glyoxalases and restrict xenobiotic mobilization by suppressing the expression of associated transporters. Accelerated nutrient uptake and grain biofortification under the influence of nanoparticles result in optimum crop productivity under sub-optimal conditions. However, over-dosing of even beneficial nanoparticles promotes severe phytotoxicity. Hence, the concentration of nanoparticles and mode of administering need to be thoroughly standardized before large-scale field applications, to ensure sustainable cereal cultivation with minimum ecological imbalance.

Current trends and future prospective in nanoremediation of heavy metals contaminated soils: A way forward towards sustainable agriculture

Heavy metals (HMs) contamination in agricultural soils is a major concern for global food safety and human health. Although, various in-situ and ex-situ remediation methods have been used for the treatment of HMs contaminated soils, however, they also have many drawbacks viz., capital investment, toxicity, and environmental health hazards. Consequently, there is an urgent need to develop a novel method to ameliorate the toxicity of HMs in agricultural soils. In recent years, nanoparticles (NPs) have gained significant attention due to their potential applications in the environment and agriculture fields. Nanoremediation employs NPs that effectively reduce the contents of toxic HMs in the soil-plant system. Several studies have reported that the application of NPs in HMs-polluted soils, which reduced plant-available HMs concentration soils. However, the long-term efficiency of NPs immobilization is still unclear. Here, we provide details about the toxicity of HMs to environmental systems and potential applications NPs to alleviate the accumulation of HMs in agricultural soils. Finally, we present the mechanistic route of HMs-toxicity alleviation in plants by NPs application as well as their long-term efficiency and future prospects.

Insight into the Prospects for Nanotechnology in Wheat Biofortification

Simple Summary

Wheat is a major crop consumed by a large population of the world. Hence, increasing its nutritional value can largely handle the malnutrition issues of the growing population. In the past few decades, different biofortification techniques including conventional breeding, transgenic approach, and agronomic biofortification have been largely employed for increasing the nutrient content in wheat grains. However, all of these techniques have their own drawbacks such as environmental hazards, long time requirement, reduced acceptability etc. Thus, nanobiofortification of wheat crop has gained interest as an efficient alternative strategy to achieve nutritional gains. However, there is still a long way forward to effectively utilize nanotechnology for wheat nutritional development. In this scenario, a review on the current advancement in wheat nanobiofortification is highly required so that the lacking points in this research area can be identified and accomplished. However, such a review article has been missing so far. This review describes the progress in the use of nanomaterials for wheat biofortification till date. It will help the scientific community to identify the lack in this research area and widely implement the nanotechnology to biofortify wheat crops.

Abstract

The deficiency of nutrients in food crops is a major issue affecting the health of human beings, mainly in underdeveloped areas. Despite the development in the methods of food fortification, several barriers such as lack of proper regulations and smaller public-private partnerships hinder its successful implementation in society. Consequently, genetic and agronomic biofortification has been suggested as the potential techniques for fortifying the nutrients in diets. However, the time-consuming nature and restricted available diversity in the targeted crop gene pool limit the benefits of genetic biofortification. In agronomic biofortification, organic fertilizers face the problem of prolonged duration of nutrients release and lesser content of minerals; while in inorganic fertilizers, the large-sized fertilizers (greater than 100 nm) suffer from volatilization and leaching losses. The application of nanotechnology in agriculture holds enormous potential to cope with these challenges. The utility of nanomaterials for wheat biofortification gains its importance by supplying the appropriate dose of fertilizer at the appropriate time diminishing the environmental concerns and smoothening the process of nutrient uptake and absorption. Wheat is a major crop whose nano-biofortification can largely handle the issue of malnutrition and nutrients deficiency in human beings. Though several research experiments have been conducted at small levels to see the effects of nano-biofortification on wheat plants, a review article providing an overview of such studies and summarizing the benefits and outcomes of wheat nano-biofortification is still lacking. Although a number of review articles are available on the role of nanotechnology in wheat crop, these are mostly focused on the role of nanoparticles in alleviating biotic and abiotic stress conditions in wheat. None of them focused on the prospects of nanotechnology for wheat biofortification. Hence, in this review for the first time, the current advancement in the employment of different nanotechnology-based approaches for wheat biofortification has been outlined. Different strategies including the supply of nano-based macro- and micronutrients that have shown promising results for wheat improvement have been discussed in detail. Understanding several aspects related to the safe usage of nanomaterials and their future perspectives may enhance their successful utilization in terms of economy and fulfillment of nutritional requirements following wheat nano-biofortification.

Biological synthesis, characterization of three metal-based nanoparticles and their anticancer activities against hepatocellular carcinoma HepG2 cells

Treatment of liver cancer has always been a challenge for clinicians and development of appropriate drug against hepatocellular carcinoma is the major focus for researchers working in the field. The synthesis of metal-based nanoparticles (NPs) by green method for pharmacological uses has attained considerable attention recently. In current study three different NPs (AgO₂, CeO₂, CuO₂) were synthesized by using Trianthima portulacastrum and Chinopodium quinoa leaf extracts. These biogenic NPs were analyzed by High-tech. approaches including Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) spectroscope, SEM-EDS spot analysis, elemental mapping and X-ray diffraction (XRD). The anticancer potential of these nanoparticles was estimated using MTT assay, against hepatic cancer cell line (HepG2). SEM secondary electron images presented the nano size of prepared particles in agglomerated form with few porous forms. Average size of Ag-, Ce-, and CuNPs was observed 19-24 nm, 8-12 nm, 13-15 nm respectively. Elemental mapping and EDS-spot analysis ratifies the formation of AgNPs, CeNPs, and CuNPs. These NPs have shown good anticancer activity at different concentrations against HepG2 cell line. Further studies are however needed to identify the molecular mechanisms of these anticancer activities.

Effects of magnetite nanoparticles on physiological processes to alleviate salinity induced oxidative damage in wheat

BACKGROUND

One of the major abiotic stressors that have a serious effect on plant growth and productivity worldwide is the salinity of soil or irrigation water. The effect of foliar application of magnetite nanoparticles (size = 22.05 nm) at different concentrations (0, 0.25, 0.5, and 1.0 ppm) was investigated to improve salinity tolerance in two wheat cultivars, namely, Misr1 (Tolerant) and Gimmeza11 (Sensitive). Moreover, toxicological investigations of magnetite oxide nanoparticle in Wistar albino rats were estimated.

RESULTS

The magnetite nanoparticles positively affected growth, chlorophyll, and enzymatic antioxidants such as superoxide dismutase (SOD), stimulating reduced glutathione and improving the aggregation of several polypeptide chains that may be linked to the tolerance of saline stress. In contrast, magnetite nanoparticles reduced malondialdehyde (MDA). Inverse sequence-tagged repeat (ISTR) assay of DNA molecular marker showed the change in band numbers with the highest polymorphic bands with 90% polymorphism at primer F3, B5 and 20 positive bands in Gimmeza11 with 0.5 ppm magnetite nanoparticles. In the median lethal dose (LD₅₀ ) study, no rats died after the oral administration of magnetite nanoparticle at different doses. Therefore, the iron oxide nanoparticle was nontoxic when administered orally by gavage.

CONCLUSION

Magnetite nanoparticles partially helped to alleviate the effects of salt stress by activating growth, chlorophyll content, SOD, glutathione, and soluble proteins in two wheat cultivars (Misr1 and Gimmeza11) and decreasing MDA content. © 2021 Society of Chemical Industry.

Effects of nanoparticles on trace element uptake and toxicity in plants: A review

Agricultural soils are receiving higher inputs of trace elements (TEs) from anthropogenic activities. Application of nanoparticles (NPs) in agriculture as nano-pesticides and nano-fertilizers has gained rapid momentum worldwide. The NPs-based fertilizers can facilitate controlled-release of nutrients which may be absorbed by plants more efficiently than conventional fertilizers. Due to their large surface area with high sorption capacity, NPs can be used to reduce excess TEs uptake by plants. The present review summarizes the effects of NPs on plant growth, photosynthesis, mineral nutrients uptake and TEs concentrations. It also highlights the possible mechanisms underlying NPs-mediated reduction of TEs toxicity at the soil and plant interphase. Nanoparticles are effective in immobilization of TEs in soil through alteration of their speciation and improving soil physical, chemical, and biological properties. At the plant level, NPs reduce TEs translocation from roots to shoots by promoting structural alterations, modifying gene expression, and improving antioxidant defense systems. However, the mechanisms underlying NPs-mediated TEs uptake and toxicity reduction vary with NPs type, mode of application, time of NPs exposure, and plant conditions (e.g., species, cultivars, and growth rate). The review emphasizes that NPs may provide new perspectives to resolve the problem of TEs toxicity in crop plants which may also reduce the food security risks. However, the potential of NPs in metal-contaminated soils is only just starting to be realized, and additional studies are required to explore the mechanisms of NPs-mediated TEs immobilization in soil and uptake by plants. Such future knowledge gap has been highlighted and discussed.

Nanoremediation technologies for sustainable remediation of contaminated environments: Recent advances and challenges

A major and growing concern within society is the lack of innovative and effective solutions to mitigate the challenge of environmental pollution. Uncontrolled release of pollutants into the environment as a result of urbanisation and industrialisation is a staggering problem of global concern. Although, the eco-toxicity of nanotechnology is still an issue of debate, however, nanoremediation is a promising emerging technology to tackle environmental contamination, especially dealing with recalcitrant contaminants. Nanoremediation represents an innovative approach for safe and sustainable remediation of persistent organic compounds such as pesticides, chlorinated solvents, brominated or halogenated chemicals, perfluoroalkyl and polyfluoroalkyl substances (PFAS), and heavy metals. This comprehensive review article provides a critical outlook on the recent advances and future perspectives of nanoremediation technologies such as photocatalysis, nano-sensing etc., applied for environmental decontamination. Moreover, sustainability assessment of nanoremediation technologies was taken into consideration for tackling legacy contamination with special focus on health and environmental impacts. The review further outlines the ecological implications of nanotechnology and provides consensus recommendations on the use of nanotechnology for a better present and sustainable future.

Iron oxide nanoparticles ameliorated the cadmium and salinity stresses in wheat plants, facilitating photosynthetic pigments and restricting cadmium uptake

Cadmium and salinity are the major threats to environmental resources and agricultural practice worldwide. The present work aims green synthesis, characterization, and application of iron oxide nanoparticles for co-alleviation of Cd and salt stresses in wheat plants. The iron oxide NPs were synthesized from a native bacterial strain, Pantoea ananatis strain RNT4, yielding a spherical FeO-NPs with a size ranging from 19 to 40 nm evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Results showed that application of 100 mg kg^-1 of the bioengineered FeO-NPs in an original saline soil stimulated wheat plant growth, gaining 36.7% of additional length as compared with the control scenarios, via alleviating the detrimental effects of abiotic stresses and thereby reprogramming the morpho-physiological state of wheat plants. In addition, the presence of FeO-NPs in soil significantly increased the nutrient concentrations of N, P and K⁺, while reducing the Na⁺ and Cl^- components in the wheat grain. Interestingly, application of the FeO-NPs in Cd-polluted soils eventually reduced wheat plant uptake of Cd by 72.5%, probably due to the adsorption of Cd onto the large surface of NPs and thereby, constraining Cd bioavailability to the plants. It provides the first evidence that a FeO-NPs-based treatment could be a candidate agricultural strategy for mitigating the Cd and salt stresses in Cd-polluted saline soils for safe agriculture practice.

Effect of phosphorus supplementation on growth, nutrient uptake, physiological responses, and cadmium absorption by tall fescue (Festuca arundinacea Schreb.) exposed to cadmium

Cadmium is a common heavy metal pollutant. In some plants, its absorption is inhibited by exogenous phosphorus. Here, the effect of P supplementation on the growth of tall fescue exposed to Cd was evaluated in a hydroponic culture experiment. Plants were exposed to five concentrations of P (0, 0.25, 0.5, 0.75, and 1.0 mmol L^-1) and three concentrations of Cd (50, 100, and 150 mg L^-1), and plant growth, Cd content, absorption, physiological characteristics, and nutrient accumulation were investigated. P supplementation significantly reduced the Cd content, Cd translocation factor (TF), Cd removal efficiency, plant P absorption, chlorophyll content, glutathione levels, glutathione reductase levels, and superoxide dismutase (SOD) activity in tall fescue under Cd stress (P < 0.05). Moreover, it increased the vertical growth rate and biomass of tall fescue. At a constant P concentration, the biomass and vertical growth rate significantly decreased with an increasing Cd concentration, and the shoot Cd content, SOD activity, and TF significantly increased (P < 0.05). High P supplementation (0.75 and 1.0 mmol L^-1) ameliorated the damage caused by 150 mg L^-1 Cd stress, and the biomass, vertical shoot and vertical root growth rates were increased by 72.06-82.06%, 250.00-316.67%, 300.00-312.00%, respectively. In the plants subjected to 50 mg L^-1 Cd stress, 0.5 mmol L^-1 P supplementation enhanced biomass, vertical shoot and vertical root growth rates by 29.99%, 20.41%, and 21.43%, respectively, and reduced the Cd content in shoots (45.85%) and roots (9.71%). Except for the total potassium content and catalase activity, different concentrations of Cd negatively affected all parameters tested. Such negative effects were limited by P supplementation. Optimizing the nutrient composition and concentrations could minimize the potential negative impacts of Cd on plant growth.

ZnO nanoparticle-based seed priming modulates early growth and enhances physio-biochemical and metabolic profiles of fragrant rice against cadmium toxicity

Background

Cadmium (Cd) is amongst the most toxic heavy metals that severely affects crop growth, whereas application of nanoparticles (NPs) to negate the toxic effects of heavy metals could be an effective management approach. In the present study, the seeds of two fragrant rice varieties i.e., Yuxiangyouzhan and Xiangyaxiangzhan under normal and Cd stress conditions i.e., 0 and 100 mg L^− 1 applied with four levels of ZnO NPs i.e., 0, 25, 50, and 100 mg L^− 1.

Results

Seed priming with ZnO NPs had no significant effect on the seed germination (p > 0.05) however, it substantially improved the seedling growth and other related physiological attributes under the Cd stress. The mean fresh weight of the shoot, and whole seedling was increased by 16.92–27.88% and by 16.92–27.88% after ZnO NPs application. The root fresh weight, root-shoot length was also substantially improved under ZnO NPs treatment. Moreover, application of ZnO NPs induced modulations in physiological and biochemical attributes e.g., the superoxide dismutase (SOD) activity in root and shoot, the peroxidase (POD) activity and metallothionein contents in root were increased under low levels of ZnO NPs. The α-amylase and total amylase activity were improved by ZnO NPs application under Cd Stress. Besides, modulation in Zn concentration and ZnO NPs uptake in the seedling were detected. The metabolomic analysis indicated that various pathways such as alanine, aspartate and glutamate metabolism, phenylpropanoid biosynthesis, and taurine and hypotaurine metabolism were possibly important for rice response to ZnO NPs and Cd.

Conclusion

Overall, application of ZnO NPs substantially improved the early growth and related physio-biochemical attributes in rice. Our findings provide new insights regarding the effects of ZnO NPs on seed germination, and early growth of rice, and its potential applications in developing crop resilience against Cd contaminated soils.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00820-9.

Improving ATPase and PPase activities, nutrient uptake and growth of salt stressed ajowan plants by salicylic acid and iron-oxide nanoparticles

Salicylic acid and iron-oxide nanoparticles alleviated salt toxicity and improved plant growth by stimulating the activities of H⁺-ATPase and H⁺-PPase and preventing nutrient imbalance. Two factorial experiments were undertaken in a greenhouse during 2018 and 2019, to evaluate the impacts of SA (1 mM) and nano-Fe₂O₃ (3 mM) sprays at 7 leaves and flowering stages on vacuolar H⁺-pumps, growth and essential oil of salt-subjected (0, 4, 8 and 12 dS m^-1 NaCl) ajowan plants. Measurements of plant traits were started at about 12 days after the last foliar spray and continued up to maturity. The H⁺-ATPase and H⁺-PPase activities and root ATP content were enhanced under low salinity, but higher salinities reduced these parameters. Rising salinity enhanced Na uptake and translocation, endogenous SA and DPPH activity, while reduced K⁺/Na⁺ ratio and nutrients uptake, leading to a reduction in plant biomass. Treatment with SA, nano-Fe₂O₃ and their combination improved H⁺-pumps activities and ATP content in roots and leaves. The SA-related treatments caused the highest activities of H⁺-pumps in roots, but Fe-related treatments resulted in the highest activities of these pumps in leaves. Increasing H⁺-pumps activities reduced sodium uptake and translocation and enhanced nutrients uptake. Foliar treatments, especially SA + nano-Fe₂O₃ augmented endogenous SA, DPPH activity, and plant growth in salt-stressed plants. Essential oil contents of vegetative and inflorescence organs under severe salinity and seeds under moderate and severe salinities were enhanced. Maximum essential oil was obtained from seeds of SA + nano-Fe₂O₃-treated plants, which was strongly correlated with endogenous SA and DPPH. Nevertheless, the SA + nano-Fe₂O₃ was the best treatment for diminishing salt toxicity and improving ajowan plant growth and essential oil production.

Zinc oxide nanocatalyst mediates cadmium and lead toxicity tolerance mechanism by differential regulation of photosynthetic machinery and antioxidant enzymes level in cotton seedlings

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ZnONPs enhanced plant growth and biomass by alleviation of heavy metal toxicity.

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Increased level photosynthetic pigments, MDA and protein contents recorded in cotton leaves in co-presence of ZnONPs.

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The activity of antioxidative enzymes was promoted significantly in the presence of ZnONPs under Cd and Pb induced stress.

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No distinct genomic alterations were recorded in the RAPD banding pattern.

Cadmium (Cd) and Lead (Pb) heavy metal pollution induced toxicity severely affects the plant growth and yield of various agriculutral crops worldwide. The present study discuss the prime role of phycomolecules coated zinc oxide nanoparticles (ZnONPs) application on development of heavy metal tolerance mechanism in cotton (Gossypium hirsutum L.) seedlings better than exposed to Cd and Pb treatments alone. Co-exposure of ZnONPs along with heavy metal treatments significantly promoted the shoot, and root growth as well as biomass compared to control, while it was down-regulated in Cd and Pb exposed seedlings. The intervention of ZnONPs had up-regulated the level of chlorophyll a, b and carotenoid contents in leaves grown under Cd and Pb treatments than the untreated control. Similarly, the level of total soluble protein and malondialdehyde (MDA-lipid peroxidation) contents was significantly increased in the co-presence of ZnONPs along with Cd and Pb treatments over their respective control. Accumulation of antioxidant defense enzymes viz., superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) was up-regulated significantly in seedlings upon co-exposure of ZnONPs with Cd and Pb treatments. Random amplified polymorphic DNA (RAPD) fingerprinting analysis exhibited no genomic changes/alterations in seedlings by co-existence of ZnONPs with heavy metals. Overall, the present results indicate that the addition of ZnONPs with Cd and Pb ion exposure protects cotton seedlings by alleviating heavy metal induced phytotoxicity and promoted physiochemical characteristics via differential regulation of photosynthetic machinery as well as antioxidative defense mechanisms in cotton seedlings. Results strongly suggest that phycomolecule coated ZnO nanoparticles could be effectively used as nanofertilizer to cultivate agronomically important crops in heavy metal polluted soil in the future.

Nanoparticle-based amelioration of drought stress and cadmium toxicity in rice via triggering the stress responsive genetic mechanisms and nutrient acquisition

Cadmium and drought are the most destructive of the abiotic stresses with negative consequences in terms of impaired metabolism, restricted nutrient use efficiency and disruptive photosynthesis of plants. The present study investigated the mitigation strategy of both aforementioned stresses by the application of iron oxide (IONPs) and hydrogel nanoparticles (HGNPs) simultaneously probably for the first time. IONPs were biofabricated by using a locally identified Bacillus strain RNT1, while HGNPs were produced chemically followed by the confirmation and characterization of both NPs through nanomaterials characterization techniques. Results of FTIR and XRD showed the capping of NPs by different functional groups together with their crystalline structure, respectively. SEM and TEM analysis showed the spherical shape along with the particle size ranging from 18 to 94 nm of both NPs, while EDS analysis confirmed the elemental purity of NPs. The results revealed that IONPs-treated rice plants increased biomass, antioxidant enzyme contents, photosynthesis efficiency, nutrient acquisition together with the decrease in reactive oxygen species and acropetal Cd translocation under normal and drought stress conditions as compared with control plants. Furthermore, the expression of the Cd transporter genes, OsHMA2, OsHMA3 and OsLCT1 were curtailed in NPs-treated rice plants under normal and drought stress conditions. The overall significance of the study lies in devising the NPs-based solutions of increasing heavy metal pollution and water availability challenges being faced the farmers around the world.

Application of different foliar iron fertilizers for enhancing the growth and antioxidant capacity of rice and minimizing cadmium accumulation

Iron (Fe) fertilizer can reduce cadmium (Cd) uptake and toxicity in rice, but the underlying mechanisms of Cd mitigation by different fertilizers are poorly understood. Here, pot experiments in rice were conducted to characterize the effects of four types of foliar-applied Fe fertilizer (chelated ferrous Fe, ferric Fe, ionic ferrous Fe, and ferric Fe) at three doses (20, 50, and 100 mg L^-1) on photosynthetic capacity, antioxidant ability, yield, and Cd accumulation in Cd-contaminated soil. The results showed that foliar Fe application increased the net photosynthesis rate by 19.3%, peroxidase (POD) by 18.2%, superoxide dismutase (SOD) by 26.9%, and catalase (CAT) by 19.6%, and led to a 7.2% increase in grain yield compared with the control. Moreover, foliar Fe application significantly reduced Cd accumulation by 15.9% in brown rice and decreased the translocation of Cd from roots to other plant tissues. Overall, application of moderate doses (50 mg L^-1) of chelated ferrous Fe was the most effective method for reducing Cd uptake (decreasing the Cd concentration in brown rice by 29.0%) and toxicity in rice (decreasing malondialdehyde by 23.2% and increasing POD, SOD, and CAT by 54.4%, 51.6%, and 45.7%, respectively), which may stem from the fact that chelated ferrous Fe was a more stable and bioavailable source of Fe for rice. The Cd concentration in rice had negative relationship with Fe concentration, and the translocation of Cd from root to the other tissues was reduced by the higher Fe nutrition status in leaf, suggesting that a high Fe supply may decrease Cd content by inhibiting the expression of the Fe transport system. These results indicate that foliar application of chelated ferrous Fe provides a promising alternative approach for enhancing growth and controlling Cd accumulation in rice plants. Furthermore, these results advance our understanding of the associations between plant Fe nutrition status and Cd accumulation.

Application of Nanoparticles Alleviates Heavy Metals Stress and Promotes Plant Growth: An Overview

Nanotechnology is playing a significant role in addressing a vast range of environmental challenges by providing innovative and effective solutions. Heavy metal (HM) contamination has gained considerable attention in recent years due their rapidly increasing concentrations in agricultural soil. Due to their unique physiochemical properties, nanoparticles (NPs) can be effectively applied for stress alleviation. In this review, we explore the current status of the literature regarding nano-enabled agriculture retrieved from the Web of Science databases and published from January 2010 to November 2020, with most of our sources spanning the past five years. We briefly discuss uptake and transport mechanisms, application methods (soil, hydroponic and foliar), exposure concentrations, and their impact on plant growth and development. The current literature contained sufficient information about NPs behavior in plants in the presence of pollutants, highlighting the alleviation mechanism to overcome the HM stress. Furthermore, we present a broad overview of recent advances regarding HM stress and the possible mechanism of interaction between NPs and HM in the agricultural system. Additionally, this review article will be supportive for the understanding of phytoremediation and micro-remediation of contaminated soils and also highlights the future research needs for the combined application of NPs in the soil for sustainable agriculture.

Synthesis and characterization of titanium dioxide nanoparticles by chemical and green methods and their antifungal activities against wheat rust

The production of metallic nanoparticles (NPs) by green and ecofriendly methods has received consideration during the recent past. The present study summarized the comparative production of titanium dioxide (TiO₂) NPs by plant extracts of Trianthema portulacastrum (T2) and Chenopodium quinoa (T3) and by conventional chemical (sol-gel) method (T1). Synthesized TiO₂-NPs were examined by high-tech. techniques such as X-Ray Diffraction (XRD), Fourier Transmission Infra-red (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) spectroscope, SEM-EDS spot analysis and elemental mapping. Synthesized TiO₂-NPs were applied on wheat rust (Ustilago tritici) for the evaluation of their antifungal activity against toxic plant pathogens. XRD results confirmed the (2θ) peak at 25.3 related to 101 anatase form. EDS-spot analysis and elemental mapping confirms the formation of TiO₂-NPs by using these techniques. SEM secondary electrons (SEs) images demonstrated the nano range of particles in cluster form with fewer porous structures. The average size of all three TiO₂-NPs was found less than 15 nm. FT-IR analysis of all three TiO₂-NPs perfectly matched with the standard parameters. The NPs prepared by both sol-gel and green methods have a good antifungal response against U. tritici, and the green prepared TiO₂-NPs were found to have the best antifungal activity against wheat rust especially NPs synthesized with the extract of C. quinoa. Overall, green method can be used for the large scale and less toxic synthesis of TiO₂-NPs because of their wide range of environmental applications.

Responses of ajowan (Trachyspermum ammi L.) to exogenous salicylic acid and iron oxide nanoparticles under salt stress

This research with a factorial arrangement was undertaken to investigate physiological responses of ajowan plants to foliar treatment of salicylic acid (1 mM) and nano-Fe₂O₃ (3 mM) under various salinity levels (0, 4, 8, 12 dS m^-1 NaCl, respectively). Rising salinity enhanced sodium and endogenous SA contents, soluble sugars, protein, glycine betaine, proline, antioxidant enzymes activities, ROS generation, and lipid peroxidation, while reduced potassium and iron contents, membrane stability index, leaf water content, leaf pigments, root and shoot biomasses, and seed yield. Application of particularly SA and SA+nano-Fe₂O₃ alleviated salt toxicity via enhancing K⁺ uptake, K⁺/Na⁺ ratio, Fe content, endogenous level of SA, the activities of antioxidant enzymes (superoxide dismutase, catalase, peroxidase, and polyphenol oxidase), and most of the osmolytes. These changes were resulted in improving membrane stability index, leaf water content, leaf pigments, root and shoot growth, and finally seed yield of plants under moderate and severe salinities. Therefore, these treatments can additively enhance salt tolerance and physiological performance of ajowan through increasing antioxidant capacity, osmolytes, and photosynthetic pigments. Graphical Abstract .

The first evidence of accumulation and avoidance behavior of macroinvertebrates in a forest soil spiked with human-made iron nanoparticles: A field experiment

Both earthworms and terrestrial isopods have been used to evaluate the quality of contaminated soil by NPs. However, most experiments have been conducted in the laboratory and under greenhouse conditions. Besides, little is known of Fe accumulation in earthworms from iron NPs (Fe NPs) under natural conditions. Therefore, the objective of this research was to evaluate the effect of manufactured NPs on the accumulation of Fe in macroinvertebrates from forest soil. Our results revealed that earthworms consume low amounts of Fe in a concentration of 1000 mg Fe NPs kg⁻¹ of dry soil, with a behavior constant over time. Besides, we observed that earthworms could not detect Fe at low concentrations (1 or 10 mg Fe NPs kg⁻¹), so they do not limit soil consumption, which translates into high amounts of Fe in their bodies. By contrast, the content of Fe in organisms is inversely proportional to increasing concentrations in the soil (R² = -0.41, p < 0.05). Therefore, although studies are needed, in addition to considering environmental factors and the physicochemical properties of the soil, endogenous worms in the evaluated area could, under natural conditions, be useful to inform us of contamination of NP manufactured from Faith. Besides, for future research, a novel methodology should be considered to demonstrate more realistic avoidance behavior under field conditions.

Nanotechnology in soil remediation - applications vs. implications

Engineered nanomaterials (ENMs) and nanotechnology have shown great potential in addressing complex problems and creating innovative approaches in soil remediation due to their unique features of high reactivity, selectivity and versatility. Meanwhile, valid concerns exist with regard to their implications towards the terrestrial environment and the ecosystem. This review summarizes: (i) the applications and the corresponding mechanisms of various types of ENMs for soil remediation; (ii) the environmental behavior of ENMs in soils and their interactions with the soil content; (iii) the environmental implications of ENMs during remedial applications. The overall objective is to promote responsible innovations so as to take optimal advantage of ENMs and nanotechnology while minimizing their adverse effects to the ecological system. It is critical to establish sustainable remediation methods that ensure a healthy and safe environment without bringing additional risk.

Effect of gibberellic acid on growth, biomass, and antioxidant defense system of wheat (Triticum aestivum L.) under cerium oxide nanoparticle stress

Recently nanoparticles (NPs) are ubiquitous in the environment because they have unique characteristics which are the reason of their wide use in various fields. The release of NPs into various environmental compartments mainly ends up in the soil through water bodies which is a serious threat to living things especially plants. When present in soil, NPs may cause toxicity in plants which increase significance to minimize NPs stress in plants. Although gibberellic acid (GA) is one of the phytohormones that has the potential to alleviate abiotic/biotic stresses in crops plant, GA-mediated alleviation of cerium oxide (CeO2) NPs in plants is still unknown, despite the large-scale application of CeO2-NPs in various fields. The present study was performed to highlight the ability of foliar-applied GA in reducing CeO2-NPs toxicity in wheat under soil exposure of CeO2-NPs. We observed that CeO2-NPs alone adversely affected the dry weights, chlorophyll contents, and nutrients and caused oxidative stress in plants, thereby reducing plant yield. GA coupled with CeO2-NPs reversed the changes caused by CeO2-NPs alone as indicated by the increase in plant growth, chlorophylls, nutrients, and yield. Furthermore, GA alleviated the oxidative stress in plants by enhancing antioxidant enzyme activities under CeO2-NPs exposure than the NPs alone which further provided the evidence of reduction in oxidative damage in plants by GA. Overall, evaluating the potential of GA in reducing CeO2-NPs toxicity in wheat could provide important information for improving food safety under CeO2-NPs exposure.

Synergistic ameliorative effect of iron oxide nanoparticles and Bacillus subtilis S4 against arsenic toxicity in Cucurbita moschata: polyamines, antioxidants, and physiochemical studies

The present study was intended to assess the potential of iron oxide nanoparticles (IONPs) and Bacillus subtilis S4 in mitigation of arsenic (As) stress in Cucurbita moschata. Cucurbita moschata seedlings were subjected to As stress for 60 days. Reduced level of growth parameters including photosynthetic pigments, rate of photosynthesis and gas exchange characteristics was observed in seedlings subjected to As stress. However, IONPs and B. subtilis S4 improved growth attributes and proline contents in supplemented C. moschata seedlings. Bacillus subtilis S4 inoculated seedlings showed higher activity of peroxidase (POD) and superoxide dismutase (SOD) under As toxicity. Similarly, the co-application of IONPs and B. subtilis S4 further increased the activity of these antioxidative enzymes. The As stress alleviation in inoculated C. moschata seedlings is credited to reduced levels of hydrogen peroxide (H₂O₂), malondialdehyde (MDA) and electrolyte leakage (EL) in IONPs and B. subtilis S4-treated plants. Furthermore, synergism between plant growth promoting bacteria (PGPB) and IONPs enhanced the biosynthesis of stress mitigating polyamines including spermidine and putrescine in As-stressed seedlings. Current research reveals that synergistic application of IONPs and B. subtilis S4 is an effective sustainable and ecofriendly approach for alleviation of As stress in C. moschata seedlings.

Efficiency of various silicon rich amendments on growth and cadmium accumulation in field grown cereals and health risk assessment

Cadmium (Cd) contamination of arable soils and its subsequent accumulation in food is one of the global issues which needs urgent attention. Field experiments were conducted to explore the impacts of ten silicon (Si) rich amendments on Cd bioavailability and accumulation by maize and wheat irrigated with sewage effluents. Results depicted that applied amendments decreased the total Cd accumulation in shoots and grains of both crops with and the maximum decrease was observed in rice husk biochar (RHB) treatment. The RHB was able to significantly decrease the translocation factor, Cd harvest and health risk indexes. All amendments differentially affected the soil pH, EC, CaCl₂-extractable Si, and decreased the AB-DTPA-extractable soil Cd. Overall, suitable Si rich amendments (like RHB and CSB etc.) can be employed to mitigate the health risks associated with dietary Cd in untreated sewage irrigated fields. However, the cost-benefit analysis such Si rich amendments should be considered before final recommendations.

Hydrogen sulfide alleviates chromium stress on cauliflower by restricting its uptake and enhancing antioxidative system

The present study evaluated the physiological and biochemical mechanisms through which exogenous sodium hydrosulfide (H₂ S donor) mitigates chromium (Cr) stress in cauliflower. The different levels of Cr included 0, 10, 100 and 200 µM. Results reported that Cr exposure reduced growth and biomass, chlorophyll (Chl) contents, gas exchange parameters and enzymatic antioxidants. Chromium stress enhanced the production of electrolyte leakage (EL), hydrogen peroxide (H₂ O₂ ) and malondialdehyde (MDA) contents and increased Cr content in the roots, stem, leaf and flowers. Exogenous H₂ S improved the physiological and biochemical attributes of Cr-stressed cauliflower. Hydrogen sulfide decreased Cr content in different parts of Cr-stressed plants, whereas it increased the Chl contents and gas exchange attributes. H₂ S reduced the EL, H₂ O₂ and MDA concentrations, enhancing the antioxidant enzymes activities in Cr-stressed roots and leaves compared to the Cr treatments alone. Collectively, our results provide an insight into the protective role of H₂ S in Cr-stressed cauliflower and suggest H₂ S as a potential candidate in reducing Cr toxicity in cauliflower and other crops.

Simultaneous mitigation of cadmium and drought stress in wheat by soil application of iron nanoparticles

Excess amount of cadmium (Cd) in arable soils and shortage of good quality water are the major abiotic factors affecting the crop yield which needs immediate solution to feed the increasing population worldwide. Recently, nanoparticles (NPs) are widely used in various industries including agriculture which is due to the unique properties of NPs. Among NPs, iron (Fe) NPs might be used to alleviate the abiotic stresses in crops but limited informations are available in the literature about the role of Fe-NPs in crops under metal stress. The present study was designed to highlight the efficiency of Fe-NPs on Cd accumulation in Cd and drought-stressed wheat. Wheat plants were grown in Cd-contaminated soil after the supply of different levels of Fe-NPs and two water regimes were introduced in the soil in latter growth stages of the plants. Cadmium and drought stress negatively affected the wheat photosynthesis, yield and caused oxidative stress in leaves with excess accumulation of Cd in grains and other plant tissues. The NPs improved the photosynthesis, yield, Fe concentrations and diminished the Cd concentrations in tissues. The NPs alleviated the oxidative stress in leaves and the efficiency depends on the NPs concentrations applied in the soil. The results obtained indicated that Fe-NPs may be employed aiming to get wheat grains with excess Fe and decreased Cd contents. However, field investigations with various sizes, shapes and levels of NPs are needed before final recommendations to the farmers.

Comparative effectiveness of different biochars and conventional organic materials on growth, photosynthesis and cadmium accumulation in cereals

Although biochar and conventional organic materials have been widely studied for lowering cadmium (Cd) uptake by plants but information regarding their comparative effectiveness is lacking. In this study, biochars from different feedstocks viz. rice husk biochar (RHB), cotton sticks biochar (CSB) and wheat straw biochar (WSB) were compared with conventional organic materials viz. farm manure (FM), poultry manure (PM) and press mud (PrMd) for their effectiveness to promote plant growth and to reduce Cd uptake by wheat and rice plants grown rotationally in a Cd-spiked (50 mg kg^-1) soil. Each amendment was applied at the rate of 2% (w/w) in three replicates. Results showed that the application of amendments improved the soil properties and plant growth, by retaining Cd in the soil and restricting its uptake by plants. The amendments decreased the ammonium bicarbonate diethylene penta acetic acid extractable soil Cd, and improved soil organic carbon (SOC) and cation exchange capacity (CEC) as compared to only Cd-contaminated soil. The highest SOC content of 2.68 and 1.68% and CEC of 8.77 and 9.39 cmol_c kg^-1 were found in RHB treated post-wheat and post-rice soil, respectively. Amendments treated soil showed lower concentrations of bioavailable Cd and the maximum reduction was recorded in RHB and PrMd amended soil. Similarly, bioaccumulation of Cd was decreased with the application of all amendments; the maximum decrease was recorded in RHB and PrMd treated soil. Our results suggested that RHB and PrMd could be used for reducing the bioaccumulation of Cd in cereal grains in alkaline soils.