The Effects of Fe2O3 Nanoparticles on Physiology and Insecticide Activity in Non-Transgenic and Bt-Transgenic Cotton

Nanoparticle-plant interactions: Physico-chemical characteristics, application strategies, and transmission electron microscopy-based ultrastructural insights, with a focus on stereological research

Ensuring global food security is pressing among challenges like population growth, climate change, soil degradation, and diminishing resources. Meeting the rising food demand while reducing agriculture's environmental impact requires innovative solutions. Nanotechnology, with its potential to revolutionize agriculture, offers novel approaches to these challenges. However, potential risks and regulatory aspects of nanoparticle (NP) utilization in agriculture must be considered to maximize their benefits for human health and the environment. Understanding NP-plant cell interactions is crucial for assessing risks of NP exposure and developing strategies to control NP uptake by treated plants. Insights into NP uptake mechanisms, distribution patterns, subcellular accumulation, and induced alterations in cellular architecture can be effectively drawn using transmission electron microscopy (TEM). TEM allows direct visualization of NPs within plant tissues/cells and their influence on organelles and subcellular structures at high resolution. Moreover, integrating TEM with stereological principles, which has not been previously utilized in NP-plant cell interaction assessments, provides a novel and quantitative framework to assess these interactions. Design-based stereology enhances TEM capability by enabling precise and unbiased quantification of three-dimensional structures from two-dimensional images. This combined approach offers comprehensive data on NP distribution, accumulation, and effects on cellular morphology, providing deeper insights into NP impact on plant physiology and health. This report highlights the efficient use of TEM, enhanced by stereology, in investigating diverse NP-plant tissue/cell interactions. This methodology facilitates detailed visualization of NPs and offers robust quantitative analysis, advancing our understanding of NP behavior in plant systems and their potential implications for agricultural sustainability.

Paradoxical effects of nanomaterials on plants: Phytohormonal perspective exposes hidden risks amidst potential benefits

The rapid growth of nanotechnology has led to the production of a significant amount of engineered nanomaterials (NMs), raising concerns about their impact on various domains. This study investigates the negative interactions between NMs and phytohormones in plants, revealing the changes in signaling crosstalk, integrated responses and ecological repercussions caused by NM pollution. Phytohormones, which include auxins, cytokinins, gibberellins, abscisic acid, ethylene, jasmonic acid, salicylic acid and brassinosteroids are essential for plant growth, development, and stress responses. This review examines the intricate relationships between NMs and phytohormones, highlighting disruptions in signaling crosstalk, integrated responses, and ecological consequences in plants due to NM pollution. Various studies demonstrate that exposure to NMs can lead to alterations in gene expression, enzyme functions, and ultimately affect plant growth and stress tolerance. Exposure to NMs has the capacity to affect plant phytohormone reactions by changing their levels, biosynthesis, and signaling mechanisms, indicating a complex interrelation between NMs and phytohormone pathways. The complexity of the relationships between NMs and phytohormones necessitates further research, utilizing modern molecular techniques, to unravel the intricate molecular mechanisms and develop strategies to mitigate the ecological consequences of NM pollution. This review provides valuable insights for researchers and environmentalists concerned about the disruptive effects of NMs on regulating phytohormone networks in plants.

Plant-nano interactions: A new insight of nano-phytotoxicity

Whether nanoparticles (NPs) are boon or bane for society has been a centre of in-depth debate and key consideration in recent times. Exclusive physicochemical properties like small size, large surface area-to-volume ratio, robust catalytic activity, immense surface energy, magnetism and superior biocompatibility make NPs obligatory in many scientific, biomedical and industrial ventures. Nano-enabled products are newer entrants in the present era. To attenuate environmental stress and maximize crop yields, scientists are tempted to introduce NPs as augmented supplements in agriculture. The feasible approaches for NPs delivery are irrigation, foliar spraying or seed priming. Internalization of excessive NPs to plants endorses negative implications at higher trophic levels via biomagnification. The characteristics of NPs (dimensions, type, solubility, surface charge), applied concentration and duration of exposure are prime factors conferring nanotoxicity in plants. Several reports approved NPs persuaded toxicity can precisely mimic abiotic stress effects. The signature effects of nanotoxicity include poor root outgrowth, biomass reduction, oxidative stress evolution, lipid peroxidation, biomolecular damage, perturbed antioxidants, genotoxicity and nutrient imbalance in plants. NPs stress impels mitogen-activated protein kinase signaling cascade and urges stress responsive defence gene expression to counteract stress in plants. Exogenous supplementation of nitric oxide (NO), arbuscular mycorrhizal fungus (AMF), phytohormones, and melatonin (ME) is novel strategy to circumvent nanotoxicity. Briefly, this review appraises plants' physio-biochemical responses and adaptation scenarios to endure NPs stress. As NPs stress represents large-scale contaminants, advanced research is indispensable to avert indiscriminate NPs usage for synchronizing nano-security in multinational markets.

A review on toxicity of nanomaterials in agriculture: Current scenario and future prospects

Phytonanotechnology plays a crucial part in the production of good quality and high-yield food. It can also alter the plant's production systems, hence permitting the efficient, controlled and stable release of agrochemicals such as fertilizers and pesticides. An advanced understanding of nanomaterials interaction with plant responses like localization and uptake, etc. could transfigure the production of crops with high disease resistance and efficient nutrients utilization. In agriculture, the use of nanomaterials has gained acceptance due to their wide-range applications. However, their toxicity and bioavailability are the major hurdles for their massive employment. Undoubtedly, nanoparticles positively influence seeds germination, growth and development, stress management and post-harvest handling of vegetables and fruits. These nanoparticles may also cause toxicity in plants through oxidative stress by generation of excessive reactive oxygen species thus affecting the cellular biomolecules and targeting different channels. Nanoparticles have shown to exert various effects on plants that are mainly affected by various attributes such as physicochemical features of nanomaterials, coating materials for nanoparticles, type of plant, growth stages and growth medium for plants. This article discusses the interaction, accretion and toxicity of nanomaterials in plants. The factors inducing nanotoxicity and the mechanisms followed by nanomaterials causing toxicity are also instructed. At the end, detoxification mechanism of plant is also presented.

Nano-sulfides of Fe and Mn Efficiently Augmented the Growth, Antioxidant Defense System, and Metal Assimilation in Rice Seedlings

Physiological and biochemical mechanisms behind nanoparticle (NP)-induced seed germination by nanopriming with metal sulfide NPs are lacunae in the field of agriculture. Sonochemically synthesized aqua-dispersed ferrous sulfide NPs (FeS-NPs) and manganese sulfide NPs (MnS-NPs) were examined as nanopriming agents for physiological, pathological, and antioxidative defense parameters of rice in the present study. Under pot house conditions, in vivo nanopriming of rice seeds with FeS NPs and MnS-NPs at a concentration of 35 μg/mL for 8 h significantly improved the physiological parameters, viz., germination percentage, seed germination index, mean germination time, dry weight, and vigor index, and decreased the phytopathological parameters of nanoprimed rice seeds, viz., mortality, seed rot, and seedling blight. Stimulation of superoxide dismutase (SOD ≥ 28.16%), ascorbate peroxidase (APX ≥ 52.38%), and catalase (CAT ≥ 28.57%) enzymes in FeS-NP- and MnS-NP-nanoprimed seeds as compared to control (hydroprimed seeds) enhanced the fitness of rice seedlings. The augmented levels of Fe and Mn content in the shoots and roots of NP-treated seedlings as compared to hydroprimed seedlings confirmed the incorporation nanometals in rice seedlings as nanonutrients for effective plant growth. Inclusively, FeS-NPs and MnS-NPs were shown to be effective nanopriming agents for promoting the germination of naturally fungal infested rice seeds.

Nanoparticles in Plants: Uptake, Transport and Physiological Activity in Leaf and Root

Due to their unique characteristics, nanoparticles are increasingly used in agricultural production through foliage spraying and soil application. The use of nanoparticles can improve the efficiency of agricultural chemicals and reduce the pollution caused by the use of agricultural chemicals. However, introducing nanoparticles into agricultural production may pose risks to the environment, food and even human health. Therefore, it is crucial to pay attention to the absorption migration, and transformation in crops, and to the interaction with higher plants and plant toxicity of nanoparticles in agriculture. Research shows that nanoparticles can be absorbed by plants and have an impact on plant physiological activities, but the absorption and transport mechanism of nanoparticles is still unclear. This paper summarizes the research progress of the absorption and transportation of nanoparticles in plants, especially the effect of size, surface charge and chemical composition of nanoparticle on the absorption and transportation in leaf and root through different ways. This paper also reviews the impact of nanoparticles on plant physiological activity. The content of the paper is helpful to guide the rational application of nanoparticles in agricultural production and ensure the sustainability of nanoparticles in agricultural production.

Green Synthesis of Iron Oxide (Hematite) Nanoparticles and Their Influence on Sorghum bicolor Growth under Drought Stress

Drought is a major abiotic stress that confronts plant growth and productivity, thus compromising food security. Plants use physiological and biochemical mechanisms to cope with drought stress, but at the expense of growth. Green-synthesized nanoparticles (NPs) have gained great attention in agriculture due to their environmental friendliness and affordability while serving as potential biofertilizers. This study investigates the role of hematite (αFe₂O₃) NPs, synthesized from Aspalathus linearis (rooibos), to improve Sorghum bicolor growth under drought stress. About 18 nm, spherical, and highly agglomerated hematite (αFe₂O₃) NPs were obtained. Sorghum seeds were primed with 5, 10, and 15 mg/L αFe₂O₃ NPs, and, after seven days of germination, the seedlings were transferred into potting soil, cultivated for fourteen days, and were subsequently water deprived (WD) for a further seven days. A reduction in plant height (78%), fresh (FW; 35%) and dry (DW; 36%) weights, and chlorophyll (chl) content ((total chl (81%), chla (135%), and chlb (1827%)) was observed in WD plants, and this correlated with low nutrients (Mg, Si, P, and K) and alteration in the anatomic structure (epidermis and vascular bundle tissues). Oxidative damage was observed as deep blue (O₂^●-) and brown (H₂O₂) spots on the leaves of WD plants, in addition to a 25% and 40% increase in oxidative stress markers (H₂O₂ and MDA) and osmolytes (proline and total soluble sugars), respectively. Seed priming with 10 mg/L αFe₂O₃ NPs improved plant height (70%), FW (56%), DW (34%), total Chl (104%), chla (160%) and chlb (1936%), anatomic structure, and nutrient distribution. Priming with 10 mg/L αFe₂O₃ NPs also protected sorghum plants from drought-induced oxidative damage by reducing ROS formation and osmolytes accumulation and prevented biomolecule degradation. The study concludes that green synthesized hematite NPs positively influenced sorghum growth and prevented oxidative damage of biomolecules by improving nutrient uptake and osmoregulation under drought stress.

Plant Growth Hormones and Nanomaterial Interface: Exploring the connection from development to defense

The global increase in nanotechnology applications has been unprecedented and has now moved into the area of agriculture and food production. Applications with promising potential in sustainable agriculture include nanobiosensors, nanofertilizers, nanopesticides, nano-mediated remediation strategies for contaminated soils and nanoscale strategies to increase crop production and protection. Given this, the impact of nanomaterials/nanoparticles (NPs) on plant species needs to be thoroughly evaluated as this represents a critical interface between the biosphere and the environment. Importantly, phytohormones represent a critical class of biomolecules to plant health and productivity; however, the impact of NPs on these molecules is poorly understood. In addition, phytohormones, and associated pathways, are widely explored in agriculture to influence several biological processes for the improvement of plant growth and productivity under natural as well as stressed conditions. However, the impact of exogenous applications of phytohormones on NP-treated plants has not been explored. The importance of hormone signaling and cross-talk with other metabolic systems makes these biomolecules ideal candidates for a thorough assessment of NP impacts on plant species. This article presents a critical evaluation of the existing yet limited literature available on NP-phytohormone interactions in plants. In addition, the developing strategy of nano-enabled precision delivery of phytohormones via nanocarriers will be explored. Finally, directions for future research and critical knowledge gaps will be identified for this important aspect of nano-enabled agriculture.

Earthworms Drive the Effect of La2O3 Nanoparticles on Radish Taproot Metabolite Profiles and Rhizosphere Microbial Communities

To promote the sustainable and safe application of nanotechnology employing engineered nanoparticles (NPs) in agroecosystems, it is crucial to pay more attention to the NP-mediated biological response process and environmental impact assessment simultaneously. Herein, 50 mg kg^-1 La₂O₃ NPs were added to soils without and with earthworms for cherry radish growth for 50 days to investigate the response changes of metabolites in radish above- and below-ground organs and rhizosphere bacterial communities. We found that La₂O₃ NP exposure, especially with earthworms, notably increased the La bioavailability and uptake by taproots and eventually increased radish leaf sucrose content and plant biomass. The La₂O₃ NP exposure significantly altered metabolite profiles in taproot flesh and peel tissues, and particularly La₂O₃ NP exposure combined with earthworms was more conducive to La₂O₃ NPs to promote radish taproot peel to synthesize more secondary antioxidant metabolites. Moreover, compared with the control, the La₂O₃ NP exposure resulted in weaker and fewer correlations between rhizosphere bacteria and taproot metabolites, but this was recovered somewhat after the inoculation of earthworms. Altogether, our results provide novel insights into the soil-fauna-driven biological and biochemical impact of La₂O₃ NP exposure on edible root crops and the long-term environmental risks to the rhizosphere microbiota in agroecosystems.

Engineered Nanomaterials for Improving the Nutritional Quality of Agricultural Products: A Review

To ensure food safety, the current agricultural development has put forward requirements for improving nutritional quality and reducing the harmful accumulation of agricultural chemicals. Nano-enabled sustainable agriculture and food security have been increasingly explored as a new research frontier. Nano-fertilizers show the potential to be more efficient than traditional fertilizers, reducing the amount used while ensuring plant uptake, supplying the inorganic nutrients needed by plants, and improving the process by which plants produce organic nutrients. Other agricultural uses of nanotechnology affect crop productivity and nutrient quality in addition to nano-fertilizers. This article will review the research progress of using nanomaterials to improve nutritional quality in recent years and point out the focus of future research.

The role of iron nanoparticles on morpho-physiological traits and genes expression (IRT1 and CAT) in rue (Ruta graveolens)

The iron nanoparticles with different physic-chemical properties induce inconsistent effects on various studied plant species. Thus, the effect of ferric oxide (Fe₂O₃) nanoparticles was compared with Fe₂O₃ microparticles and FeSO₄complexes of EDTA for major physiological and gene expression in Rue (Ruta graveolens). Iron root content increased as Fe-MPs + EDTA ˂˂ Fe-NPs + EDTA˂ FeSO₄ + EDTA. The shoot's iron remained unchanged or slightly increased under most of FeSO₄ and Fe-MPs + EDTA treatments. Under Fe-NPs + EDTA treatment, 50 and 250 µM concentration decreased on shoot iron by 23.2% and 19.4% compared to control, respectively. But the shoot iron at 500 µM NPs was 28.2% higher than that of the control. A 46-58 fold lower Fe translocation was observed under Fe-NPs + EDTA than Fe-MPs + EDTA. The effect of Fe-NPs + EDTA was more significant on plant fresh and dry mass than the control. All treatments showed an increase in anthocyanin by 19-84% in leaves compared to the control. The Fe-NPs + EDTA and MPs + EDTA induced similar effects on enhanced growth parameters, total chlorophyll, catalase enzyme activity, gene, and reduced chlorophyll a/b and oxidants. Catalase enzyme activity in FeSO₄ and MPs + EDTA was similar, and in Fe-NPs + EDTA treatments were influenced by coarse and fine regulation mechanisms, respectively. Iron MPs + EDTA had a more negative effect on IRT₁ relative gene expression in roots as compared to other iron forms. The IRT₁ relative gene expression in shoots was positively affected by 31-81% under all treatment types (except control and 250 µM Fe-NPs + EDTA, and 250 µM MPs + EDTA). These results could reveal the potential mechanism of plant response to nanoparticles.

Metal/Metalloid-Based Nanomaterials for Plant Abiotic Stress Tolerance: An Overview of the Mechanisms

In agriculture, abiotic stress is one of the critical issues impacting the crop productivity and yield. Such stress factors lead to the generation of reactive oxygen species, membrane damage, and other plant metabolic activities. To neutralize the harmful effects of abiotic stress, several strategies have been employed that include the utilization of nanomaterials. Nanomaterials are now gaining attention worldwide to protect plant growth against abiotic stresses such as drought, salinity, heavy metals, extreme temperatures, flooding, etc. However, their behavior is significantly impacted by the dose in which they are being used in agriculture. Furthermore, the action of nanomaterials in plants under various stresses still require understanding. Hence, with this background, the present review envisages to highlight beneficial role of nanomaterials in plants, their mode of action, and their mechanism in overcoming various abiotic stresses. It also emphasizes upon antioxidant activities of different nanomaterials and their dose-dependent variability in plants' growth under stress. Nevertheless, limitations of using nanomaterials in agriculture are also presented in this review.

Functionalized Magnetic Nanomaterials in Agricultural Applications

The development of functional nanomaterials exhibiting cost-effectiveness, biocompatibility and biodegradability in the form of nanoadditives, nanofertilizers, nanosensors, nanopesticides and herbicides, etc., has attracted considerable attention in the field of agriculture. Such nanomaterials have demonstrated the ability to increase crop production, enable the efficient and targeted delivery of agrochemicals and nutrients, enhance plant resistance to various stress factors and act as nanosensors for the detection of various pollutants, plant diseases and insufficient plant nutrition. Among others, functional magnetic nanomaterials based on iron, iron oxide, cobalt, cobalt and nickel ferrite nanoparticles, etc., are currently being investigated in agricultural applications due to their unique and tunable magnetic properties, the existing versatility with regard to their (bio)functionalization, and in some cases, their inherent ability to increase crop yield. This review article provides an up-to-date appraisal of functionalized magnetic nanomaterials being explored in the agricultural sector.

Nanobiotechnological advancements in agriculture and food industry: Applications, nanotoxicity, and future perspectives

The high demand for sufficient and safe food, and continuous damage of environment by conventional agriculture are major challenges facing the globe. The necessity of smart alternatives and more sustainable practices in food production is crucial to confront the steady increase in human population and careless depletion of global resources. Nanotechnology implementation in agriculture offers smart delivery systems of nutrients, pesticides, and genetic materials for enhanced soil fertility and protection, along with improved traits for better stress tolerance. Additionally, nano-based sensors are the ideal approach towards precision farming for monitoring all factors that impact on agricultural productivity. Furthermore, nanotechnology can play a significant role in post-harvest food processing and packaging to reduce food contamination and wastage. In this review, nanotechnology applications in the agriculture and food sector are reviewed. Implementations of nanotechnology in agriculture have included nano- remediation of wastewater for land irrigation, nanofertilizers, nanopesticides, and nanosensors, while the beneficial effects of nanomaterials (NMs) in promoting genetic traits, germination, and stress tolerance of plants are discussed. Furthermore, the article highlights the efficiency of nanoparticles (NPs) and nanozymes in food processing and packaging. To this end, the potential risks and impacts of NMs on soil, plants, and human tissues and organs are emphasized in order to unravel the complex bio-nano interactions. Finally, the strengths, weaknesses, opportunities, and threats of nanotechnology are evaluated and discussed to provide a broad and clear view of the nanotechnology potentials, as well as future directions for nano-based agri-food applications towards sustainability.

Effect of Selenium Nanoparticles on Germination of Hordéum Vulgáre Barley Seeds

Within the framework of this study, the effect of nanoparticles of the essential trace element selenium stabilized by Polyvinylpirrolidone (PVP) C15 (8 ± 2 kDa) and ascorbic acid on the germination of barley seeds has been studied. Selenium nanoparticles stabilized by PVP C15 (8 ± 2 kDa) and ascorbic acid, characterized by a spherical shape, monodisperse size distribution, and a diameter of about 70 ± 5 nm, were obtained by the chemical reduction method. The experiment compared the effect of selenium nanoparticles and selenous acid on seed germination. The positive effect of preparation of selenium nanoparticles stabilized by PVP C15 (8 ± 2 kDa) and ascorbic acid on the length of roots and shoots, the number of roots, and the percentage of seed germination has been revealed. It was determined that the highest percentage of Hordeum vulgare L. culture seed germination was achieved using a preparation of selenium nanoparticles stabilized by PVP C15 (8 ± 2 kDa) and ascorbic acid at a concentration of of 4.65 µg/mL. Analysis of the results showed that selenium in the form of nanoparticles has an order of magnitude that is less toxic than in the form of selenous acid. The study of morphological and functional parameters during the germination of Hordeum vulgare L. seeds allowed us to conclude that selenium nanoparticles can be successfully used in agronomy and agriculture to provide plants with the essential microelement selenium, which is necessary for the normal growth and development of crops.

Downregulation of the photosynthetic machinery and carbon storage signaling pathways mediate La2O3 nanoparticle toxicity on radish taproot formation

The molecular and physiological mechanisms of how rare earth oxide nanoparticles (NPs) alter radish (Raphanus sativus L.) taproot formation and cracking were investigated in the present study. We compared plants that received suspensions of 10, 50, 100, 300 mg L^-1 of La₂O₃ NPs, 300 m L^-1 La₂O₃ bulk-particles (BPs), 0.8 m L^-1 La³⁺, or only water for six days during their tuber formation period. 100 and 300 mg L^-1 La₂O₃ NPs exposure decreased storage root biomass by 38% and 60%, respectively, and they both induced visible root cracking. Physiological analyses showed that La₂O₃ NPs exposure (>100 mg L^-1) significantly inhibited leaf net photosynthetic rate, cell wall pectin synthesis of both storage root epidermis and xylem parenchyma tissues, but increased the contents of cellulose and hemicellulose 1 in root epidermis cell walls. Moreover, transcriptome analysis further found that La₂O₃ NPs changed root cell wall structure by down-regulating core genes involved in cell wall pectin and IAA biosynthesis, which coincided with the observed La₂O₃ NPs-induced root cracking. Our results revealed the molecular mechanisms related to cell wall carbohydrate metabolism in response to NPs stress, providing a step forward for understanding the causes of NPs phytotoxicity on edible plant taproot formation and cracking.

Nanopriming with zero-valent iron synthesized using pomegranate peel waste: A "green" approach for yield enhancement in Oryza sativa L. cv. Gonindobhog

Nanopriming is a combination of nanoparticle treatment and a seed dressing technique that can increase seed quality, seedling vigour, yield and also imparts tolerance against biotic and abiotic stress. Here, nano-scale zero-valent iron (G-nZVI) was synthesized using fruit peel waste of Punica granatum L and their formation was validated from XRD and optical spectroscopic techniques. Later, the seeds were primed with G-nZVI at six different concentrations (0, 10, 20, 40, 80, and 160 mg L ^-1) to determine the dose which is optimum for increasing germination percentage and seedling vigour of rice (Oryza sativa L. cv. Gobindobhog). According to initial results, upon priming seeds with 40-80 mg L ^-1 G-nZVI highest growth rate was found. The early growth enhancement of seedlings was chiefly attributed to increased ROS generation, higher hydrolytic enzyme activities, and increased iron uptake in germinating seeds upon nanopriming. The effects of nanopriming were carried over to later stages of development. A field experiment was carried out where nanoprimed seeds and traditional hydroprimed control seeds were sown in plots and grown till maturity without the aid of any conventional fertilizers and pesticides and it was found that crop yield and grain nutrient concentrations were higher in nanoprimed sets. Compared to control hydroprimed sets, 1.53 folds higher crop yield was observed upon seed priming with 80 mg L ^-1 G-nZVI. Thus in the future, G-nZVI can be considered to be a novel low-cost, eco-friendly, food waste-derived seed treatment agent that has immense potential in increasing rice yield.

Toxicity evaluation of iron oxide nanoparticles and accumulation by microalgae Coelastrella terrestris

Uses of iron oxide nanoparticles have increased in the last decade. The increased application marked a concern regarding their fate and behavior in the environment. Especially towards the aquatic ecosystems, as the ultimate descend of these iron oxide nanoparticles are aquatic bodies. The greater surface area per mass compared with larger-sized materials of the same chemistry renders these nanoparticles biologically more active. Therefore, it is imperative to assess their eco-toxicogical impact on aquatic eco-systems. In the present study, comparative assessment of iron oxide nanoparticles and their bulk counterpart have been monitored using Coelastrella terrestris up to 40 days. Interestingly, study reveals the potential of Coelastrella terrestris as tool for the bioremediation of iron nanoparticles to combat nano-pollution. Adsorption/absorption kinetics measured after 25 days of treatments with iron oxide nanoparticle and its bulk counterpart revealed higher absorption levels in comparison to the adsorption with maximum accumulation factor (AF) of 2.984 at 50 mg L^-1 in nano-form. Iron oxide absorption was found linearly related with concentration in both cases (y = 11.313x-12.165, R² = 0.8691 in nano; y = 6.35x-5.74, R² = 0.8128 in bulk). However, 50-mg L^-1 nanoparticle concentration was perceived sub-lethal for the algae with 33.33% algal growth reduction under nano and 27.77% under bulk counterpart. Other biochemical parameters, i.e., SOD, CAT, MDA, and lipid quantification, were also quantified to correlate the state of metabolism of treated algal cells in comparison to the control and these exhibited reduction in algal growth due to oxidative stress. Morphological changes were monitored through SEM and TEM.

Iron (III) oxide nanoparticles alleviate arsenic induced stunting in Vigna radiata

Iron nanoparticles (NPs) are widely used for the removal of arsenic from water. In this study, we evaluated the interaction between arsenate (AsO₄^3-) and Fe₂O₃-NPs on early seedling growth of Vigna radiata. Seedlings were raised in AsO₄^3- and Fe₂O₃-NPs, alone and in combination. While Fe₂O₃-NPs slightly promoted seedling growth, AsO₄^3- reduced seedling growth drastically. AsO₄^3--induced decline in the seedling growth was recovered by Fe₂O₃-NPs. In contrast, equivalent concentrations of FeCl₃, alone and together with AsO₄^3-, inhibited seed germination completely. Lower arsenic content in seedlings raised in the presence of Fe₂O₃-NPs indicated that Fe₂O₃-NPs restricted arsenic uptake. Ability of Fe₂O₃-NPs to restrict the arsenic uptake of the seedlings was due to adsorption of AsO₄^3-, as revealed by transmission and scanning electron microscopy. Non-toxic levels of iron in seedlings were due to restriction of Fe₂O₃-NPs to root-surface. AsO₄^3- enhanced the ferric chelate reductase activity of root which was recovered by Fe₂O₃-NPs. The AsO₄^3--induced oxidative stress, evident from high levels of proline, H₂O₂ and malondialdehyde, and lowered root oxidisability was ameliorated by Fe₂O₃-NPs. AsO₄³-induced enhancement in total antioxidant capacity, superoxide dismutase and catalase activity, and decline in guaiacol peroxidase activity were antagonized by Fe₂O₃-NPs. Our findings reveal that Fe₂O₃-NPs provide effective resistance/amelioration to arsenic toxicity by reducing arsenic availability to plants.

Nanoparticle-Plant Interactions: Two-Way Traffic

In this Review, an effort is made to discuss the most recent progress and future trend in the two-way traffic of the interactions between plants and nanoparticles (NPs). One way is the use of plants to synthesize NPs in an environmentally benign manner with a focus on the mechanism and optimization of the synthesis. Another way is the effects of synthetic NPs on plant fate with a focus on the transport mechanisms of NPs within plants as well as NP-mediated seed germination and plant development. When NPs are in soil, they can be adsorbed at the root surface, followed by their uptake and inter/intracellular movement in the plant tissues. NPs may also be taken up by foliage under aerial deposition, largely through stomata, trichomes, and cuticles, but the exact mode of NP entry into plants is not well documented. The NP-plant interactions may lead to inhibitory or stimulatory effects on seed germination and plant development, depending on NP compositions, concentrations, and plant species. In numerous cases, radiation-absorbing efficiency, CO2 assimilation capacity, and delay of chloroplast aging have been reported in the plant response to NP treatments, although the mechanisms involved in these processes remain to be studied.

Plant Response to Engineered Metal Oxide Nanoparticles

All metal oxide nanoparticles influence the growth and development of plants. They generally enhance or reduce seed germination, shoot/root growth, biomass production and physiological and biochemical activities. Some plant species have not shown any physiological change, although significant variations in antioxidant enzyme activity and upregulation of heat shock protein have been observed. Plants have evolved antioxidant defence mechanism which involves enzymatic as well as non-enzymatic components to prevent oxidative damage and enhance plant resistance to metal oxide toxicity. The exact mechanism of plant defence against the toxicity of nanomaterials has not been fully explored. The absorption and translocation of metal oxide nanoparticles in different parts of the plant depend on their bioavailability, concentration, solubility and exposure time. Further, these nanoparticles may reach other organisms, animals and humans through food chain which may alter the entire biodiversity. This review attempts to summarize the plant response to a number of metal oxide nanoparticles and their translocation/distribution in root/shoot. The toxicity of metal oxide nanoparticles has also been considered to see if they affect the production of seeds, fruits and the plant biomass as a whole.

Interaction of γ-Fe2O3 nanoparticles with Citrus maxima leaves and the corresponding physiological effects via foliar application

Background

Nutrient-containing nanomaterials have been developed as fertilizers to foster plant growth and agricultural yield through root applications. However, if applied through leaves, how these nanomaterials, e.g. γ-Fe₂O₃ nanoparticles (NPs), influence the plant growth and health are largely unknown. This study is aimed to assess the effects of foliar-applied γ-Fe₂O₃ NPs and their ionic counterparts on plant physiology of Citrus maxima and the associated mechanisms.

Results

No significant changes of chlorophyll content and root activity were observed upon the exposure of 20–100 mg/L γ-Fe₂O₃ NPs and Fe³⁺. In C. maxima roots, no oxidative stress occurred under all Fe treatments. In the shoots, 20 and 50 mg/L γ-Fe₂O₃ NPs did not induce oxidative stress while 100 mg/L γ-Fe₂O₃ NPs did. Furthermore, there was a positive correlation between the dosages of γ-Fe₂O₃ NPs and Fe³⁺ and iron accumulation in shoots. However, the accumulated iron in shoots was not translocated down to roots. We observed down-regulation of ferric-chelate reductase (FRO2) gene expression exposed to γ-Fe₂O₃ NPs and Fe³⁺ treatments. The gene expression of a Fe²⁺ transporter, Nramp3, was down regulated as well under γ-Fe₂O₃ NPs exposure. Although 100 mg/L γ-Fe₂O₃ NPs and 20–100 mg/L Fe³⁺ led to higher wax content, genes associated with wax formation (WIN1) and transport (ABCG12) were downregulated or unchanged compared to the control.

Conclusions

Our results showed that both γ-Fe₂O₃ NPs and Fe³⁺ exposure via foliar spray had an inconsequential effect on plant growth, but γ-Fe₂O₃ NPs can reduce nutrient loss due to their the strong adsorption ability. C. maxima plants exposed to γ-Fe₂O₃ NPs and Fe³⁺ were in iron-replete status. Moreover, the biosynthesis and transport of wax is a collaborative and multigene controlled process. This study compared the various effects of γ-Fe₂O₃ NPs, Fe³⁺ and Fe chelate and exhibited the advantages of NPs as a foliar fertilizer, laying the foundation for the future applications of nutrient-containing nanomaterials in agriculture and horticulture.Graphical abstract

Toxicity of iron oxide nanoparticles to grass litter decomposition in a sandy soil

We examined time-dependent effect of iron oxide nanoparticles (IONPs) at a rate of 2000 mg kg⁻¹ soil on Cynodon dactylon litter (3 g kg⁻¹) decomposition in an arid sandy soil. Overall, heterotrophic cultivable bacterial and fungal colonies, and microbial biomass carbon were significantly decreased in litter-amended soil by the application of nanoparticles after 90 and 180 days of incubation. Time dependent effect of nanoparticles was significant for microbial biomass in litter-amended soil where nanoparticles decreased this variable from 27% after 90 days to 49% after 180 days. IONPs decreased CO₂ emission by 28 and 30% from litter-amended soil after 90 and 180 days, respectively. These observations indicated that time-dependent effect was not significant on grass-litter carbon mineralization efficiency. Alternatively, nanoparticles application significantly reduced mineral nitrogen content in litter-amended soil in both time intervals. Therefore, nitrogen mineralization efficiency was decreased to 60% after 180 days compared to that after 90 days in nanoparticles grass-litter amended soil. These effects can be explained by the presence of labile Fe in microbial biomass after 180 days in nanoparticles amendment. Hence, our results suggest that toxicity of IONPs to soil functioning should consider before recommending their use in agro-ecosystems.