Enhanced legume root growth with pre-soaking in α-Fe2O3 nanoparticle fertilizer

Advancement of metal oxide nanomaterials on agri-food fronts

The application of metal oxide nanomaterials (MOx NMs) in the agrifood industry offers innovative solutions that can facilitate a paradigm shift in a sector that is currently facing challenges in meeting the growing requirements for food production, while safeguarding the environment from the impacts of current agriculture practices. This review comprehensively illustrates recent advancements and applications of MOx for sustainable practices in the food and agricultural industries and environmental preservation. Relevant published data point out that MOx NMs can be tailored for specific properties, enabling advanced design concepts with improved features for various applications in the agrifood industry. Applications include nano-agrochemical formulation, control of food quality through nanosensors, and smart food packaging. Furthermore, recent research suggests MOx's vital role in addressing environmental challenges by removing toxic elements from contaminated soil and water. This mitigates the environmental effects of widespread agrichemical use and creates a more favorable environment for plant growth. The review also discusses potential barriers, particularly regarding MOx toxicity and risk evaluation. Fundamental concerns about possible adverse effects on human health and the environment must be addressed to establish an appropriate regulatory framework for nano metal oxide-based food and agricultural products.

Microbial nanotechnology for agriculture, food, and environmental sustainability: Current status and future perspective

The field of nanotechnology has the mysterious capacity to reform every subject it touches. Nanotechnology advancements have already altered a variety of scientific and industrial fields. Nanoparticles (NPs) with sizes ranging from 1 to 100 nm (nm) are of great scientific and commercial interest. Their functions and characteristics differ significantly from those of bulk metal. Commercial quantities of NPs are synthesized using chemical or physical methods. The use of the physical and chemical approaches remained popular for many years; however, the recognition of their hazardous effects on human well-being and conditions influenced serious world perspectives for the researchers. There is a growing need in this field for simple, non-toxic, clean, and environmentally safe nanoparticle production methods to reduce environmental impact and waste and increase energy productivity. Microbial nanotechnology is relatively a new field. Using various microorganisms, a wide range of nanoparticles with well-defined chemical composition, morphology, and size have been synthesized, and their applications in a wide range of cutting-edge technological areas have been investigated. Green synthesis of the nanoparticles is cost-efficient and requires low maintenance. The present review highlights the synthesis of the nanoparticles by different microbes, their characterization, and their biotechnological potential. It further deals with the applications in biomedical, food, and textile industries as well as its role in biosensing, waste recycling, and biofuel production.

Foliar application of Fe2O3 nanofertilizer on growth and yield of cauliflower (Brassica oleracea var. Botrytis L.) cv. Pusa Snowball K-1

The growth, yield, and quality of cauliflower (Brassica oleracea var. botrytis L.) cv. Pusa Snowball K-1 were studied using Fe2O3-nano fertilizer (Fe2O3-N) in combination with Azotobacter, Farmyard manure (FYM), and Phosphorus solubilizing bacteria (PSB). Hydrothermally synthesized Fe2O3 nanoparticles characterized with XRD, FTIR, and SEM. The experiment consisting 12 treatments viz. T1 (Fe2O3-N), T2 comprising of Fe2O3-N + FYM + Azotobacter + PSB, T3 (Fe2O3-N + Azotobacter + PSB), T4 (Fe2O3-N + FYM + Azotobacter), T5 (Fe2O3-N + FYM + PSB), T6 (Fe2O3-N + FYM), T7 (Fe2O3-N + Azotobacter), T8 (Fe2O3-N + PSB), T9 (PSB), T10 (Azotobacter), T11 (FYM), and T12 (control). Fe2O3 NPs positively enhance the photosynthetic activity and stimulate catalyze enzymatic action in plant leaves that effect the health of the plant and remarkably increase the crop yield. Application of Fe2O3-nano fertilizer (Fe2O3-N) along the Azotobacter, FYM, and PSB was shown encouraging growth effects to improve the cropping behavior. Fe2O3 NPs positively enhance the photosynthetic activity and stimulate catalyze enzymatic action in plant leaves that effect the health of the plant and remarkably increase the crop yield.

Nano-enabled seed treatment: A new and sustainable approach to engineering climate-resilient crops

Under a changing climate, keeping the food supply steady for an ever-increasing population will require crop plants adapted to environmental fluctuations. Genetic engineering and genome-editing approaches have been used for developing climate-resilient crops. However, genetically modified crops have yet to be widely accepted, especially for small-scale farmers in low-income countries and some societies. Nano-priming (seed exposure to nanoparticles, NPs) has appeared as an alternative to the abovementioned techniques. This technique improves seed germination speed, promotes seedlings' vigor, and enhances plant tolerance to adverse conditions such as drought, salinity, temperature, and flooding, which may occur under extreme weather conditions. Moreover, nano-enabled seed treatment can increase the disease resistance of crops by boosting immunity, which will reduce the use of pesticides. This unsophisticated, farmer-available, cost-effective, and environment-friendly seed treatment approach may help crop plants fight climate change challenges. This review discusses the previous information about nano-enabled seed treatment for enhancing plant tolerance to abiotic stresses and increasing disease resistance. Current knowledge about the mechanisms underlying nanomaterial-seed interactions is discussed. To conclude, the review includes research questions to address before this technique reaches its full potential.

New insights into the environmental application of hybrid nanoparticles in metal contaminated agroecosystem: A review

Heavy metals (HMs) contamination in agricultural soils is a major constraint to provide safe food to society. Cultivation of food crops on these soils, channels the HMs into the food chain and causes serious human health and socioeconomic problems. Multiple conventional and non-conventional remedial options are already in practice with variable success rates, but nanotechnology has proved its success due to higher efficiency. It also led the hypothesis to use hybrid nanoparticles (HNPs) with extended benefits to remediate the HMs and supplement nutrients to enhance the crop yield in the contaminated environments. Hybrid nanoparticles are defined as exclusive chemical conjugates of inorganic and/or organic nanomaterials that are combinations of two or more organic components, two or more inorganic components, or at least one of both types of components. HNPs of different elements like essential nutrients, beneficial nutrients and carbon-based nanoparticles are used for the remediation of metals contaminated soil and the production of metal free crops. Characterizing features of HNPs including particle size, surface area, reactivity, and solubility affect the efficacy of these HNPs in the contaminated environment. Hybrid nanoparticles have great potential to remove the HMs ions from soil solution and restrict their ingress into the root tissues. Furthermore, HNPs of essential nutrients not only compete with heavy metal uptake by plants but also fulfill the need of nutrients. This review provides a comprehensive overview of the challenges associated with application of HNPs in contaminated soils, environmental implications, their remediation ability, and factors affecting their dynamics in environmental matrices.

Zero-valent Iron Nanoparticles: Biogenic Synthesis and their Medical Applications; Existing Challenges and Future Prospects

OBJECTIVES

In the last decade, nanobiotechnology is emerging as a keen prudence area owing to its widespread applications in the medical field. In this context, zero-valent iron nanoparticles (nZVI) have garnered tremendous attention attributed to their cheap, non-toxic, excellent paramagnetic nature, extremely reactive surface, and dual oxidation state that makes them excellent antioxidants and free-radical scavengers. Facile biogenic synthesis, in which a biological source is used as a template for the synthesis of NPs, is presumably dominant among other physical and chemical synthetic procedures. The purpose of this review is to elucidate plant-mediated synthesis of nZVI, although they have been successfully fabricated by microbes and other biological entities (such as starch, chitosan, alginate, cashew nut shell, etc.) as well.

METHODS

The methodology of the study involved keyword searches of electronic databases, including ScienceDirect, NCBI, and Google Scholar (2008-2023). Search terms of the review included 'biogenic synthesis of nZVI', 'plant-mediated synthesis of nZVI', 'medical applications of nZVI', and 'Recent advancements and future prospects of nZVI'.

RESULTS

Various articles were identified and reviewed for biogenic fabrication of stable nZVI with the vast majority of studies reporting positive findings. The resultant nanomaterial found great interest for biomedical purposes such as their use as biocompatible anticancer, antimicrobial, antioxidant, and albumin binding agents that have not been adequately accessed in previous studies.

CONCLUSION

This review shows that there are potential cost savings applications to be made when using biogenic nZVI for medical purposes. However, the encountering challenges concluded later, along with the prospects for sustainable future development.

Physiological and metabolomic analyses reveal that Fe3O4 nanoparticles ameliorate cadmium and arsenic toxicity in Panax notoginseng

Heavy metal(loid)-contaminated available arable land seriously affects crop development and growth. Engineered nanomaterials have great potential in mitigating toxic metal(loid) stress in plants. However, there are few details of nanoparticles (NPs) involved in Panax notoginseng response to cadmium (Cd) and arsenic (As). Herein, integrating physiological and metabolomic analyses, we investigated the effects of Fe3O4 NPs on plant growth and Cd/As responses in P. notoginseng. Cd/As treatment caused severe growth inhibition. However, foliar application of Fe3O4 NPs increased beneficial elements in the roots and/or leaves, decreased Cd/As content by 10.38% and 20.41% in the roots, reduced membrane damage and regulated antioxidant enzyme activity, thereby alleviating Cd/As-induced growth inhibition, as indicated by increased shoot fresh weight (FW), the rootlet length and root FW by 40.14%, 15.74%, and 46.70% under Cd stress and promoted the shoot FW by 27.00% under As toxicity. Metabolomic analysis showed that 227 and 295 differentially accumulated metabolites (DAMs) were identified, and their accumulation patterns were classified into 8 and 6 clusters in the roots and leaves, respectively. Fe3O4 NPs altered metabolites significantly involved in key pathways, including amino sugar and nucleotide sugar metabolism, flavonoid biosynthesis and phenylalanine metabolism, thus mediating the trade-off between plant growth and defense under stress. Interestingly, Fe3O4 NPs recovered more Cd/As-induced DAMs to normal levels, further supporting that Fe3O4 NPs positively affected seedling growth under metal(loid)s stress. In addition, Fe3O4 NPs altered terpenoids when the seedlings were subjected to Cd/As stress, thus affecting their potential medicinal value. This study provides insights into using nanoparticles to improve potential active ingredients of medicinal plants in metal(loid)-contaminated areas.

Zinc oxide nano-flowers improve the growth and propagation of mulberry cuttings grown under different irrigation regimes by mitigating drought-related complications and enhancing zinc uptake

Silkworm larvae mainly consume mulberry leaves; therefore, mulberry cultivation is important for the production of raw silk. Drought stress and micronutrient deficiency (Zn) are known to affect the propagation of mulberry cuttings. In this purview, the current investigation attempted to inspect the efficacy of different concentrations of zinc oxide nano-flower (ZnNFs) applied through both soil admixture and foliar spray on the propagation of mulberry cuttings grown under deficit irrigation regimes. The overall results demonstrated that the ZnNF-treated plant cuttings were well-adapted to drought stress and performed better in comparison to the control set. Out of the tested concentrations - ZnNF-10 (applied as 10 mg/kg soil and 10 ppm as foliar spray thrice) was found to be optimum, showing relatively better initial root establishment, the emergence of leaves, and survival and sprouting percentage. Further studies also confirmed an improvement in the accumulation of photosynthetic pigments, carbohydrates, and protein content even under extreme drought conditions. Most importantly, the ZnNF-10 treatment contributed to ROS detoxification and cell membrane protection by enhancing the pool of antioxidant enzymes. The study further demonstrated that ZnNF-10 application enhanced zinc content by 147.50%, 179.49%, and 171.99% in root, shoot, and leaves of the treated cuttings; thereby, improving the bioaccumulation factor of the plant parts. All of these interactive phenomena led to an increment in shoot height, biomass, leaf area, and leaf number of cuttings. These findings, therefore, indicated that ZnNFs can be developed as a promising nano-fertilizer for mulberry growth facilitating Zn uptake and mitigation of drought-induced complications.

Ag/ZnO core-shell NPs boost photosynthesis and growth rate in wheat seedlings under simulated full sun spectrum

Breeding programs rely on light wavelength, intensity, and photoperiod for rapid success. In this study, we investigated the ability of Ag/ZnO nanoparticles (NPs) to improve the photosynthesis and growth of wheat under simulated full solar spectrum conditions. The world population is increasing rapidly, it is necessary to increase the number of crops in order to ensure the world's food security. Conventional breeding is time-consuming and expensive, so new techniques such as rapid breeding are needed. Rapid breeding shows promise in increasing crop yields by controlling photoperiod and environmental factors in growth regulators. However, achieving optimum growth and photosynthesis rates is still a challenge. Here, we used various methods to evaluate the effects of Ag/ZnO NPs on rice seeds. Using bioinformatics simulations, we evaluated the light-harvesting efficiency of chlorophyll a in the presence of Ag/ZnO NPs. Chemically synthesized Ag/ZnO nanoparticles were applied to rice grains at different concentrations (0-50 mg/L) and subjected to a 12-h preparation time. Evaluation of seed germination rate and growth response in different light conditions using a Light Emitting Diode (LED) growth chamber that simulates a rapid growth system. The analysis showed that the surface plasmon resonance of Ag/ZnO NPs increased 38-fold, resulting in a 160-fold increase in the light absorption capacity of chlorophyll. These estimates are supported by experimental results showing an 18% increase in the yield of rice seeds treated with 15 mg/L Ag/ZnO NPs. More importantly, the treated crops showed a 2.5-fold increase in growth and a 1.4-fold increase in chlorophyll content under the simulated full sun spectrum (4500 lx) and a 16-h light/8-h dark photoperiod. More importantly, these effects are achieved without oxidative or lipid peroxidative damage. Our findings offer a good idea to increase crop growth by improving photosynthesis using Ag/ZnO nanoparticle mixture. To develop this approach, future research should go towards optimizing nanoparticles, investigating the long-term effects, and exploring the applicability of this process in many products. The inclusion of Ag/ZnO NPs in rapid breeding programs has the potential to transform crops by reducing production and increasing agricultural productivity.

Chemically Synthesized AgNPs and Piriformosporaindica Synergistically Augment Nutritional Quality in Black Rice

The use of biofertilizers has been the spotlight of research aiming to mitigate the food security threat as well as to restore the fertility of agricultural lands, for decades. Several studies are being conducted to unravel the role and mechanisms of plant growth-promoting microbes. In the present research, we evaluated the effect of silver nanoparticles (AgNPs) and Piriformospora indica on the growth and nutritional enhancement of black rice (Oryzae sativa. L.) individually and in combination. Among the different treatment conditions, the AgNPs + P. indica treatment led to a significant (p ≤ 0.05) increase in morphological and agronomic parameters. In comparison to the control, the percentage increase in plant height in AgNPs-treated black rice was 2.47%, while that for the treatment with only P. indica was 13.2% and that for the treatment with both AgNPs + P. indica was 30.9%. For the number of productive tillers, the effect of AgNPs in comparison to the control was non-significant; however, the effect of P. indica and AgNPs + P. indica showed a significant (p ≤ 0.05) increase of 13.2% and 30.9% in both the treatments, respectively. Gas chromatography mass spectrophotometry analysis of grains revealed that the contents of phenylalanine, tryptophan, and histidine (aromatic amino acids) were significantly (p ≤ 0.05) increased by 75%, 11.1%, and 50%, respectively, in P. indica-treated black rice. Nutrient profiling showed that macronutrients such as potassium, calcium, magnesium were found to be increased by 72.8%, 86.4% and 59.2%, respectively, in the treatment with AgNPs + P. indica in comparison to the control plants. Additionally, a significant (p ≤ 0.05) increase of 51.9% in anthocyanin content was observed in AgNPs + P. indica-treated black rice. The P. indica treatment also showed improved growth and augmented nutrient contents. From this study, we were able to understand that AgNPs + P. indica treatment would be a better plant growth-promoting factor and further evaluation would enable us to obtain a clear picture of its mechanisms of action.

Interference of Nanoparticulates in seed invigoration of Green gram

In the present study, the impact of four metal/metal oxide nanoparticles (NPs) viz.Ag, ZnO),ZVI and TiO₂ on physiological seed quality attributes of green gram (Vigna radiata) were evaluated. The synthesized NPs characterized and evaluated the germination percentage, vigour indices and physiological responses like catalase and peroxidase activities (seed quality parameters) of fresh, naturally aged and fresh accelerated aged seed lots of green gram. In naturally aged seeds, zinc oxide-NPs (1000 mg kg^-1) treated seeds showed 14.96% higher germination percentage, 24.81% higher vigour index I and (3696) and 33.33% higher vigour index II than the controls. The treated seeds with ZnO-NPs (1000 mg kg^-1) under fresh accelerated aged conditions resulted in higher than 15.15% of germination percentage, 23.61% of vigour index I and 24.11% of vigour index II over controls. Moreover, ZnO-NPs treated naturally aged seeds showed lower electrical conductivity (EC) of 20.10 μ S cm^-1g^-1 than the control (26.60 μ S cm^-1 g^-1). Pertinent to catalase enzyme activity, ZnO-NPs (1000 mg kg^-1) treated naturally aged seed lots resulted in 356.89 μmol H₂O₂ mg^-1 min^-1 activity, 216.05 μmol H₂O₂ mg^-1 min^-1 activity in fresh accelerated aged seed lots.. Similarly, ZnO-NPs (1000 mg kg^-1) enhanced peroxidase enzyme activity in naturally aged seed lots (3.21 μg/FW/10 min) than control (0.72 μg/FW/10 min) that depicts 63.35% of increased enzyme activity. The present results showcases the ZnO-NPs as potent nano-priming agents in maintaining the seed quality parameters that ultimately establish better crop stand and field performance.

Impacts of Binary Oxide Nanoparticles on the Soybean Plant and Its Rhizosphere, Associated Phytohormones, and Enzymes

The utilization of binary oxide nanoparticles is geometrically increasing due to their numerous applications. Their intentional or accidental release after usage has led to their omnipresence in the environment. The usage of sludge or fertilizer containing binary oxide nanoparticles is likely to increase the chance of the plants being exposed to these binary oxide nanoparticles. The aim of the present review is to assess the detailed positive and negative impacts of these oxide nanoparticles on the soybean plants and its rhizosphere. In this study, methods of synthesizing binary oxide nanoparticles, as well as the merits and demerits of these methods, are discussed. Furthermore, various methods of characterizing the binary oxide nanoparticles in the tissues of soybean are highlighted. These characterization techniques help to track the nanoparticles inside the soybean plant. In addition, the assessment of rhizosphere microbial communities of soybean that have been exposed to these binary oxide nanoparticles is discussed. The impacts of binary oxide nanoparticles on the leaf, stem, root, seeds, and rhizosphere of soybean plant are comprehensively discussed. The impacts of binary oxides on the bioactive compounds such as phytohormones are also highlighted. Overall, it was observed that the impacts of the oxide nanoparticles on the soybean, rhizosphere, and bioactive compounds were dose-dependent. Lastly, the way forward on research involving the interactions of binary oxide nanoparticles and soybean plants is suggested.

Foliar-applied nanoscale zero-valent iron (nZVI) and iron oxide (Fe3O4) induce differential responses in growth, physiology, antioxidative defense and biochemical indices in Leonurus cardiaca L

The impacts of nZVI and iron oxides on growth, physiology and elicitation of bioactive antioxidant metabolites in medicinal aromatic plants must be critically assessed to ensure their safe utilization within the food chain and achieve nutritional gains. The present study investigated and compared the morpho-physiological and biochemical changes of Leonurus cardiaca L. plants as affected by various concentrations (0, 250, 500 and 1000 mg L^-1) of nZVI and Fe₃O₄. The foliar uptake of nZVI was verified through Scanning Electron Microscopy (SEM) images and Energy Dispersive X-ray (EDX) analytical spectra. Plants exposed to nZVI at low concentration showed comparatively monotonic deposition of NPs on the surface of leaves, however, the agglomerate size of nZVI was raised as their doses increased, leading to remarkable changes in anatomical and biochemical traits. 250 mg L^-1 nZVI and 500 mg L^-1 Fe₃O₄ significantly (P < 0.05) increased plant dry matter accumulation by 37.8 and 27% over the control, respectively. The treatments of nZVI and Fe₃O₄ at 250 mg L^-1 significantly (P < 0.01) improved chlorophyll a content by 22.4% and 15.3% as compared to the control, and then a rapid decrease (by 14.8% and 4.1%) followed at 1000 mg L^-1, respectively. Both nZVI and Fe₃O₄ at 250 mg L^-1 had no significant impact on malondialdehyde (MDA) formation, however, at an exposure of 500-1000 mg L^-1, the MDA levels and cellular electrolyte leakage were increased. Although nZVI particles could be utilized by plants and enhanced the synthesis of chlorophylls and secondary metabolites, they appeared to be more toxic than Fe₃O₄ at 1000 mg L^-1. Exposure to nZVI levels showed positive, negative and or neutral impacts on leaf water content compared to control, while no significant difference was observed with Fe₃O₄ treatments. Soluble sugar, total phenolics and hyperoside content were significantly increased upon optimum concentrations of employed treatments-with 250 mg L^-1 nZVI being most superior. Among the extracts, those obtained from plants treated with 250-500 mg L^-1 nZVI revealed the strong antioxidant activity in terms of scavenging free radical (DPPH) and chelating ferrous ions. These results suggest that nZVI (at lower concentration) has alternative and additional benefits both as nano-fertilizer and nano-elicitor for biosynthesis of antioxidant metabolites in plants, but at high concentrations is more toxic than Fe₃O₄.

The impact of engineered nanomaterials on the environment: Release mechanism, toxicity, transformation, and remediation

The presence and longevity of nanomaterials in the ecosystem, as well as their properties, account for environmental toxicity. When nanomaterials in terrestrial and aquatic systems are exposed to the prevailing environmental conditions, they undergo various transformations such as dissociation, dissolution, and aggregation, which affects the food chain. The toxicity of nanomaterials is influenced by a variety of factors, including environmental factors and its physico-chemical characteristics. Bioaccumulation, biotransformation, and biomagnification are the mechanisms that have been identified for determining the fate of nanomaterials. The route taken by nanomaterials to reach living cells provides us with information about their toxicity profile. This review discusses the recent advances in the transport, transformation, and fate of nanomaterials after they are released into the environment. The review also discusses how nanoparticles affect lower trophic organisms through direct contact, the impact of nanoparticles on higher trophic organisms, and the possible options for remediation.

Iron Oxide and Silicon Nanoparticles Modulate Mineral Nutrient Homeostasis and Metabolism in Cadmium-Stressed Phaseolus vulgaris

The application of nanoparticles (NPs) has been proved as an efficient and promising technique for mitigating a wide range of stressors in plants. The present study elucidates the synergistic effect of iron oxide nanoparticles (IONPs) and silicon nanoparticles (SiNPs) in the attenuation of Cd toxicity in Phaseolus vulgaris. Seeds of P. vulgaris were treated with IONPs (10 mg/L) and SiNPs (20 mg/L). Seedlings of uniform size were transplanted to pots for 40 days. The results demonstrated that nanoparticles (NPs) enhanced growth, net photosynthetic rate, and gas exchange attributes in P. vulgaris plants grown in Cd-contaminated soil. Synergistic application of IONPs and SiNPs raised not only K+ content, but also biosynthesis of polyamines (PAs), which alleviated Cd stress in P. vulgaris seedlings. Additionally, NPs decreased malondialdehyde (MDA) content and electrolyte leakage (EL) in P. vulgaris plants exposed to Cd stress. These findings suggest that stress alleviation was mainly attributed to the enhanced accumulation of K+ content, improved antioxidant defense system, and higher spermidine (Spd) and putrescine (Put) levels. It is suggested that various forms of NPs can be applied synergistically to minimize heavy metal stress, thus increasing crop production under stressed conditions.

Nano-enabled improvements of growth and colonization rate in wheat inoculated with arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi display desired potential to boost crop productivity and drought acclimation. Yet, whether nanoparticles can be incorporated into arbuscular mycorrhizal fungi for better improvement and its relevant morphologic and anatomical evidences are little documented. Pot culture experiment on wheat (Triticum aestivum L.) was conducted under drought stress (30% FWC) as well as well watered conditions (80% FWC) that involved priming of wheat seeds with iron nanoparticles at different concentrations (5mg L^-1, 10 mg L^-1 and 15 mg L^-1) with and without the inoculation of Glomus intraradices. The effects of treatments were observed on morphological and physiological parameters across jointing, anthesis and maturity stage. Root colonization and nanoparticle uptake trend by seeds and roots was also recorded. We observed strikingly high enhancement in biomass up to 109% under drought and 71% under well-watered conditions, and grain yield increased to 163% under drought and 60% under well-watered conditions. Iron nanoparticles at 10 mg L^-1 when combined with Glomus intraradices resulted in maximum wheat growth and yield, which mechanically resulted from higher rhizosphere colonization level, water use efficiency and photosynthetic rate under drought stress (P < 0.01). Across growth stages, optical micrograph observations affirmed higher root infection rate when combined with nanoparticles. Transmission electron microscopy indicated the penetration of nanoparticles into the seeds and translocation across roots whereas energy dispersive X-ray analyses further confirmed the presence of Fe in these organs. Iron nanoparticles significantly enhanced the growth-promoting and drought-tolerant effects of Glomus intraradices on wheat.

Interactions of iron-based nanoparticles with soil dissolved organic matter: adsorption, aging, and effects on hexavalent chromium removal

The interactions and mechanisms between soil dissolved organic matter (DOM) and three types of iron-based nanoparticles (NPs), i.e., nanoscale zero-valent iron (nZVI) particles, Fe₂O₃ NPs, and Fe₃O₄ NPs, were investigated in short-term exposure experiments. The adsorption results showed that soil DOM was rapidly adsorbed on the surface of the iron-based NPs with the adsorption rate varying according to Fe₃O₄ > Fe₂O₃ > nZVI. Spectral analysis results revealed that aromatic DOM fractions with high-molecular-weights were preferentially adsorbed. The binding mechanism was determined as hydrogen bonding and ligand exchange via Fourier transform infrared spectroscopy (FT-IR) analysis. Scanning electron microscopy, FT-IR, X-ray photoelectron spectroscopy, and X-ray diffraction were used to identify the corrosion products of the three iron-based NPs at the adsorption equilibrium. The results suggest that Fe₃O₄ and/or γ-Fe₂O₃ and α-FeOOH were the main corrosion products of nZVIs and α-FeOOH was obtained as an aged product of Fe₃O₄ NPs. Results of Cr(VI) removal tests suggest that the aged nZVI achieved 79.87% of Cr(VI) removal and the Cr(VI) removal efficiency was significantly improved by coating DOM onto Fe₂O₃ NPs. The overall data indicate the fate and transformation of iron-based NPs and the enhancement for Cr(VI) removal after interactions between DOM and NPs.

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.

Nanoparticle-Based Sustainable Agriculture and Food Science: Recent Advances and Future Outlook

In the current scenario, it is an urgent requirement to satisfy the nutritional demands of the rapidly growing global population. Using conventional farming, nearly one third of crops get damaged, mainly due to pest infestation, microbial attacks, natural disasters, poor soil quality, and lesser nutrient availability. More innovative technologies are immediately required to overcome these issues. In this regard, nanotechnology has contributed to the agrotechnological revolution that has imminent potential to reform the resilient agricultural system while promising food security. Therefore, nanoparticles are becoming a new-age material to transform modern agricultural practices. The variety of nanoparticle-based formulations, including nano-sized pesticides, herbicides, fungicides, fertilizers, and sensors, have been widely investigated for plant health management and soil improvement. In-depth understanding of plant and nanomaterial interactions opens new avenues toward improving crop practices through increased properties such as disease resistance, crop yield, and nutrient utilization. In this review, we highlight the critical points to address current nanotechnology-based agricultural research that could benefit productivity and food security in future.

Biogenic iron oxide nanoparticles enhance callogenesis and regeneration pattern of recalcitrant Cicer arietinum L

This study is the first report on the biosynthesized iron oxide nanoparticles (IONPs) which mediate in-vitro callus induction and shoot regeneration in economically important recalcitrant chickpea crop (Cicer arietinum L.). Here, we used leaf extract of Cymbopogon jwarancusa for the synthesis of IONPs in order to achieve a better biocompatibility. The bioactive compounds in C. jwarancusa leaf extract served as both reducing and capping agents in the fabrication process of IONPs. Field emission scanning electron microscopy (FE-SEM) revealed rods like surface morphology of IONPs with an average diameter of 50±0.2 nm. Energy-dispersive X-ray spectroscopy (EDS) depicted formation of pure IONPs with 69.84% Fe and 30.16% O2. X-ray diffractometry (XRD) and attenuated total reflectance-fourier transform infrared (ATR-FTIR) validate the crystalline structure, chemical analysis detect the presence of various biomolecular fingerprints in the as synthesized IONPs. UV-visible absorption spectroscopy depicts activity of IONPs under visible light. Thermo-gravimetric analysis (TGA) displayed thermal loss of organic capping around 500°C and confirmed their stabilization. The biosynthesized IONPs revealed promising results in callus induction, shoot regeneration and root induction of chickpea plants. Both chickpea varieties Punjab-Noor 09 and Bittle-98 explants, Embryo axes (EA) and Embryo axes plus adjacent part of cotyledon (EXC) demonstrated dose-dependent response. Among all explants, EXC of Punjab-Noor variety showed the highest callogenesis (96%) and shoot regeneration frequency (88%), while root induction frequency was also increased to 83%. Iron content was quantified in regenerated chickpea varieties through inductively coupled plasma-optical emission spectrometry. The quantity of iron is significantly increased in Punjab-Noor regenerated plants (4.88 mg/g) as compare to control treated plants (2.42 mg/g). We found that IONPs enhance chickpea growth pattern and keep regenerated plantlets infection free by providing an optimum environment for rapid growth and development. Thus, IONPs synthesized through green process can be utilized in tissue culture studies in other important recalcitrant legumes crops.

Uptake, translocation, and physiological effects of hematite (α-Fe2O3) nanoparticles in barley (Hordeum vulgare L.)

There has been a growing concern with the environmental influences of nanomaterials due to recent developments in nanotechnology. This study investigates the impact and fate of hematite nanoparticles (α-Fe₂O₃ NPs) (∼14 nm in size) on a crop species, barley (Hordeum vulgare L.). For this purpose, hematite NPs (50, 100, 200, and 400 mg/L) were hydroponically applied to barley at germination and seedling stages (three weeks). Inductively coupled plasma mass spectrophotometry (ICP-MS) along with vibrating sample magnetometer (VSM) techniques were used to track the NPs in plant tissues. The effects of NPs on the root cells were observed by scanning electron microscopy (SEM) and confocal microscopy. Results revealed that α-Fe₂O₃ NPs significantly reduced the germination rate (from 80% in control to 30% in 400 mg/L), as well as chlorophyll (36-39%) and carotenoid (37%) contents. Moreover, the treatment led to a significant decline in the quantum yield of photosystem II (Fv/Fm). Leaf VSM analysis indicated a change in magnetic signal for NPs-treated samples compared with untreated ones, which is mostly attributed to the iron (Fe) ions incorporated within the leaf tissue. Besides, Fe content in the roots and leaf had gradually increased by the increasing doses of NPs, which was confirming NPs' translocation to the aerial parts. Microscopic observations revealed that α-Fe₂O₃ NPs altered root cell morphology and led to the injury of cell membranes. This study, in the light of our findings, shows that α-Fe₂O₃ NPs (∼14 nm in size) are taken up by the roots of the barley plants, and migrate to the plant leaves. Besides, NPs are phytotoxic for barley as they inhibit germination and pigment biosynthesis. This inhibition is probably due to the injury of the cell membranes in the roots. Therefore, the use of hematite NPs in agriculture and thereby their environmental diffusion must be addressed carefully.

Physiological and anti-oxidative response of biologically and chemically synthesized iron oxide: Zea mays a case study

The synthesis methodology, particle size and shape, dose optimization, and toxicity studies of nano-fertilizers are vital prior to their field application. This study investigates the comparative response of chemically synthesized and biologically synthesized iron oxide nanorods (NRs) using moringa olefera along with bulk FeCl3 on summer maize (Zea mays). It is found that FeCl3 salt and chemically synthesized iron oxides NRs caused growth retardation and impaired plant physiological and anti-oxidative activities at a concentration higher than 25 mg/L due to toxicity by over accumulation. While iron released form biologically synthesized NRs have shown significantly positive results even at 50 mg/L due to their low toxicity, an improved leaf area (13%), number of leaves per plant (26%), total chlorophyll content (80%) and nitrate content (6%) with biologically synthesized NRs are obtained. Moreover, the plant anti-oxidative activity also increased on treatment with biologically synthesized NRs because of their ability to form a complex with metal ions. These findings suggest that biologically synthesized iron oxides NRs are an efficient iron source and can last for a long time. Thus, proving that nanofertilizer are required to have specific surface chemistry to release the nutrient in an appropriate concentration for better plant growth.

Size effect of iron (III) oxide nanomaterials on the growth, and their uptake and translocation in common wheat (Triticum aestivum L.)

Nanomaterials (NMs) have emerged in the last decades and are used in many disciplines such as industry, material sciences, biomedicine, biotechnology, bioenergy, and agriculture. The size of the NMs is a critical factor that affects NMs' integration and transfer into the biological systems. Therefore, this study aims at investigating the effect of NMs-size on i) plant growth and physiology, and ii) NMs uptake and translocation in plant tissues. For these purposes, iron (III) oxide (Fe₂O₃) NMs with varied sizes, 8-10, 20-40, and 30-50 nm, have been applied to wheat plants in a hydroponic system. Results showed that Fe₂O₃ NMs enhanced root length, plant height, biomass, and chlorophyll content of wheat. Confocal microscopy analysis indicated that Fe₂O₃ NMs cause injury in root-tip cells without a visible toxic symptom. Vibrating sample magnetometer (VSM), and inductively coupled plasma-mass spectroscopy (ICP-MS) analyses of leaf tissues revealed that all tested NMs were up taken by wheat plant and translocated to the leaves. Iron content was found to be dramatically increased in NMs-treated plant tissues, which possibly contributed to the growth enhancement. Experiments confirmed that Fe₂O₃ NMs with 20-40 nm size is much more efficient in plant growth compared to those with 8-10 and 30-50 nm size. Overall, Fe₂O₃ NMs with 20-40 nm in size could be proposed as a nano-fertilizer for agricultural applications. On the other hand, the translocation of NMs in the wheat plant requires further investigation of their effects on the end users.

Template-free microwave-assisted hydrothermal synthesis of manganese zinc ferrite as a nanofertilizer for squash plant (Cucurbita pepo L)

Manganese, zinc, and iron are the most essential micronutrients required for plant growth and applied as foliar fertilizers. Herein, a simple template-free microwave-assisted hydrothermal green synthesis technique was adapted to produce manganese zinc ferrite nanoparticles (Mn0.5Zn0.5Fe2O4 NPs) at different temperatures (100, 120, 140, 160 and 180 °C). The prepared nanomaterials were employed at different concentrations (0, 10, 20, and 30 ppm) as foliar nanofertilizers during the squash (Cucurbita pepo L) planting process. X-ray diffraction patterns of the prepared nanomaterials confirmed successful production of the nanoferrite material. The prepared nanofertilizers showed type IV adsorption isotherm characteristic for mesoporous materials. FE-SEM and HR-TEM imaging showed that the nanoparticles were cubic shaped and increased in particle size with the increase in microwave temperature during production. The impact of application of the synthesized ferrite nanoparticles on vegetative growth, proximate analysis, minerals content and the yield of squash plant was investigated for two consecutive successful planting seasons. The nanoferrite synthesized at 160 °C and applied to the growing plants at a concentration of 10 ppm gave the highest increase in % yield (49.3 and 52.9%) compared to the untreated squash for the two consecutive seasons, whereas the maximum organic matter content (73.0 and 72.5%) and total energy (260 and 258.3 kcal/g) in squash leaves were obtained in plants treated with 30 ppm ferrite nanoparticles synthesized at 180 °C. On the other hand, the maximum organic matter content (76.6 and 76.3%) and total energy (253.6 and 250.3 kcal/g) in squash fruits were attained with plants supplied by 20 ppm ferrite nanoparticles synthesized at 160 °C. These results indicate that the simple template-free microwave-assisted hydrothermal green synthesis technique for the production of manganese zinc ferrite nanoparticles yields nanoparticles appropriate for use as fertilizer for Cucurbita pepo L.

Nano-Biotechnology in Agriculture: Use of Nanomaterials to Promote Plant Growth and Stress Tolerance

Sustainable agriculture is a key component of the effort to meet the increased food demand of a rapidly increasing global population. Nano-biotechnology is a promising tool for sustainable agriculture. However, rather than acting as nanocarriers, some nanoparticles (NPs) with unique physiochemical properties inherently enhance plant growth and stress tolerance. This biological role of nanoparticles depends on their physiochemical properties, application method (foliar delivery, hydroponics, soil), and the applied concentration. Here we review the effects of the different types, properties, and concentrations of nanoparticles on plant growth and on various abiotic (salinity, drought, heat, high light, and heavy metals) and biotic (pathogens and herbivores) stresses. The ability of nanoparticles to stimulate plant growth by positive effects on seed germination, root or shoot growth, and biomass or grain yield is also considered. The information presented herein will allow researchers within and outside the nano-biotechnology field to better select the appropriate nanoparticles as starting materials in agricultural applications. Ultimately, a shift from testing/utilizing existing nanoparticles to designing specific nanoparticles based on agriculture needs will facilitate the use of nanotechnology in sustainable agriculture.