Assessment of the Phytotoxicity of Metal Oxide Nanoparticles on Two Crop Plants, Maize (Zea mays L.) and Rice (Oryza sativa L.)

An exploration of the influence of ZnO NPs treatment on germination of radish seeds under salt stress based on the YOLOv8-R lightweight model

BACKGROUND

Since traditional germination test methods have drawbacks such as slow efficiency, proneness to error, and damage to seeds, a non-destructive testing method is proposed for full-process germination of radish seeds, which improves the monitoring efficiency of seed quality.

RESULTS

Based on YOLOv8n, a lightweight test model YOLOv8-R is proposed, where the number of parameters, the amount of calculation, and size of weights are significantly reduced by replacing the backbone network with PP-LCNet, the neck part with CCFM, the C2f of the neck part with OREPA, the SPPF with FocalModulation, and the Detect of the head part with LADH. The ablation test and comparative test prove the performance of the model. With adoption of germination rate, germination index, and germination potential as the three vitality indicators, the seed germination phenotype collection system and YOLOv8-R model are used to analyze the full time-series sequence effects of different ZnO NPs concentrations on germination of radish seeds under varying degrees of salt stress.

CONCLUSIONS

The results show that salt stress inhibits the germination of radish seeds and that the inhibition effect is more obvious with the increased concentration of NaCl solution; in cultivation with deionized water, the germination rate of radish seeds does not change significantly with increased concentration of ZnO NPs, but the germination index and germination potential increase initially and then decline; in cultivation with NaCl solution, the germination rate, germination potential and germination index of radish seeds first increase and then decline with increased concentration of ZnO NPs.

Effect of CeO2, TiO2 and SiO2 nanoparticles on the growth and quality of model medicinal plant Salvia miltiorrhiza by acting on soil microenvironment

In this study, a six-month pot experiment was conducted to explore the effects of nanoparticles (NPs), including CeO2, TiO2 and SiO2 NPs at 200 and 800 mg/kg, on the growth and quality of model medicinal plant Salvia miltiorrhiza. A control group was implemented without the application of NPs. Results showed that NPs had no significant effect on root biomass. Treatment with 200 mg/kg of SiO2 NPs significantly increased the total tanshinone content by 44.07 %, while 200 mg/kg of CeO2 NPs were conducive to a 22.34 % increase in salvianolic acid B content. Exposure to CeO2 NPs induced a substantial rise in the MDA content in leaves (176.25 % and 329.15 % under low and high concentration exposure, respectively), resulting in pronounced oxidative stress. However, TiO2 and SiO2 NPs did not evoke a robust response from the antioxidant system. Besides, high doses of CeO2 NP-amended soil led to reduced nitrogen, phosphorus and potassium contents. Furthermore, the NP amendment disturbed the carbon and nitrogen metabolism in the plant rhizosphere and reshaped the rhizosphere microbial community structure. The application of CeO2 and TiO2 NPs promoted the accumulation of metabolites with antioxidant functions, such as D-altrose, trehalose, arachidonic acid and ergosterol. NPs displayed a notable suppressive effect on pathogenic fungi (Fusarium and Gibberella) in the rhizosphere, while enriching beneficial taxa with disease resistance, heavy metal antagonism and plant growth promotion ability (Lysobacter, Streptomycetaceae, Bacillaceae and Hannaella). Correlation analysis indicated the involvement of rhizosphere microorganisms in plant adaptation to NP amendments. NPs regulate plant growth and quality by altering soil properties, rhizosphere microbial community structure, and influencing plant and rhizosphere microbe metabolism. These findings were beneficial to deepening the understanding of the mechanism by which NPs affect medicinal plants.

Evaluating the phytotoxicological effects of bulk and nano forms of zinc oxide on cellular respiration-related indices and differential gene expression in Hordeum vulgare L

The increasing use of nanoparticles is driving the growth of research on their effects on living organisms. However, studies on the effects of nanoparticles on cellular respiration are still limited. The remodeling of cellular-respiration-related indices in plants induced by zinc oxide nanoparticles (nnZnO) and its bulk form (blZnO) was investigated for the first time. For this purpose, barley (Hordeum vulgare L.) seedlings were grown hydroponically for one week with the addition of test compounds at concentrations of 0, 0.3, 2, and 10 mg mL-1. The results showed that a low concentration (0.3 mg mL-1) of blZnO did not cause significant changes in the respiration efficiency, ATP content, and total reactive oxygen species (ROS) content in leaf tissues. Moreover, a dose of 0.3 mg mL-1 nnZnO increased respiration efficiency in both leaves (17 %) and roots (38 %). Under the influence of blZnO and nnZnO at medium (2 mg mL-1) and high (10 mg mL-1) concentrations, a dose-dependent decrease in respiration efficiency from 28 % to 87 % was observed. Moreover, the negative effect was greater under the influence of nnZnO. The gene transcription of the subunits of the mitochondria electron transport chain (ETC) changed mainly only under the influence of nnZnO in high concentration. Expression of the ATPase subunit gene, atp1, increased slightly (by 36 %) in leaf tissue under the influence of medium and high concentrations of test compounds, whereas in the root tissues, the atp1 mRNA level decreased significantly (1.6-2.9 times) in all treatments. A dramatic decrease (1.5-2.4 times) in ATP content was also detected in the roots. Against the background of overexpression of the AOX1d1 gene, an isoform of alternative oxidase (AOX), the total ROS content in leaves decreased (with the exception of 10 mg mL-1 nnZnO). However, in the roots, where the pressure of the stress factor is higher, there was a significant increase in ROS levels, with a maximum six-fold increase under 10 mg mL-1 nnZnO. A significant decrease in transcript levels of the pentose phosphate pathway and glycolytic enzymes was also shown in the root tissues compared to leaves. Thus, the disruption of oxidative phosphorylation leads to a decrease in ATP synthesis and an increase in ROS production; concomitantly reducing the efficiency of cellular respiration.

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.

Boosting plant resilience: The promise of rare earth nanomaterials in growth, physiology, and stress mitigation

Rare earth elements (REE) have been extensively used in a variety of applications such as cell phones, electric vehicles, and lasers. REEs are also used as nanomaterials (NMs), which have distinctive features that make them suitable candidates for biomedical applications. In this review, we have highlighted the role of rare earth element nanomaterials (REE-NMs) in the growth of plants and physiology, including seed sprouting rate, shoot biomass, root biomass, and photosynthetic parameters. In addition, we discuss the role of REE-NMs in the biochemical and molecular responses of plants. Crucially, REE-NMs influence the primary metabolites of plants, namely sugars, amino acids, lipids, vitamins, enzymes, polyols, sorbitol, and mannitol, and secondary metabolites, like terpenoids, alkaloids, phenolics, and sulfur-containing compounds. Despite their protective effects, elevated concentrations of NMs are reported to induce toxicity and affect plant growth when compared with lower concentrations, and they not only induce toxicity in plants but also affect soil microbes, aquatic organisms, and humans via the food chain. Overall, we are still at an early stage of understanding the role of REE in plant physiology and growth, and it is essential to examine the interaction of nanoparticles with plant metabolites and their impact on the expression of plant genes and signaling networks.

The update and transport of aluminum nanoparticles in plants and their biochemical and molecular phototoxicity on plant growth and development: A systematic review

As aluminum nanoparticles (Al-NPs) are widely used in our daily life and various industries, Al-NPs has been becoming an emerging pollution in the environment. The impact of this NP has been attracting more and more attention from the scientific communities. In this review, we systematically summarized the interactions, uptake, and transport of Al-NPs in the plant system. Al-NPs can enter plants through different pathways and accumulate in various tissues, leading to alter plant growth and development. Al-NPs also affected root, shoot, and leaf characteristics as well as changing nutrient uptake and distribution and inducing oxidative stress via excess reactive radical generation, thereby impairing plant defense systems. Additionally, Al-NPs altered gene expression, which involved in various signaling pathways and metabolic processes in plants, that further altered plants susceptible or tolerant to stressors. The review also emphasized the effects of Al-NP size, surface charge, concentration, and exposure duration on plant growth and development. In the future, more research should be focused on mechanisms underlying Al-NPs phytotoxicity and potential risk to humans and off-target species.

Effects of TiO2 ultraviolet filter and sunscreens on coastal dune plant performance and competitive interactions

Ultraviolet filters (UVFs) added to sunscreens (SS) are emerging contaminants in marine environments due to their adverse effects on organisms and ecosystems. UVFs have also been detected in beach-dune systems, but their influence on resident organisms has not been explored yet. Native plants are fundamental components of coastal dunes, and these ecologically/economically important systems are currently among the most threatened globally. Thus, understanding whether UVFs may act as threats to dune plants is crucial. This field study evaluated and compared the effects of titanium dioxide nanoparticles (nTiO2), one of the inorganic UVFs most commonly added to sunscreens, and those of a commercial sunscreen product containing it (SS-nTiO2) on the performance of adult dune plants of a native (Thinopyrum junceum) and a non-native invasive species (Carpobrotus sp. pl.) and their competitive interactions at environmentally realistic concentrations. The effects of nTiO2, SS-nTiO2 and of a sunscreen product containing just organic UVFs (SS-OF) on early life stages of T. junceum were also examined. Ti bulk content in sand and plants at the study site ranged from 970 to 1069 mg kg-1 and from 2 to 7.9 mg kg-1, respectively. Thinopyrum junceum adult plants periodically exposed during the summer season to seawater contaminated by SS-nTiO2 produced less biomass than un-exposed plants and nTiO2 exposed plants. nTiO2 and SS-nTiO2 reduced the capacity of T. junceum to control the spread of Carpobrotus. Both SS-nTiO2 and SS-OF reduced seedling emergence in T. junceum whereas nTiO2 did not. These results demonstrated that the periodical exposures of native dune plants to sunscreens could reduce their establishment success and growth and favor invasive plant spread potentially resulting in community structure changes. They also emphasize the need to assess the phytotoxicity not only of single UVFs but especially that of complete sunscreen products to design more eco-friendly formulations in the future.

Magnesium oxide nanoparticles alleviate arsenic toxicity, reduce oxidative stress and arsenic accumulation in rice (Oryza sativa L.)

Magnesium oxide nanoparticles (MgO NPs) have been attracted by the scientific community for their combating action against heavy metal stress in plants. However, their role towards the mitigation of arsenic (As) induced toxicity is still obscure. In the present study, MgO NPs were synthesized through the green route and assessed their efficacy towards the reduction of As accumulation and phytotoxicity in As-stressed rice cultivar MTU-1010 under laboratory conditions. Initially, rice seedlings were grown under separate and combined applications of As (10 mg/L) and MgO NPs (0, 10, 50, and 100 mg/L) and further analyzed plant growth attributes and As accumulation in rice seedlings. Characterization of biosynthesized MgO NPs by UV-Vis spectrophotometer, transmission electron microscopy (TEM), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis showed the cubic in shape, and crystalline nature (73.10%) with average size ranges from 17-23 nm. The growth experiment showed a significant (p < 0.05) increase in seed germination, seedling growth, photosynthetic and other pigments content, and biomass accumulation in rice seedlings under the combined application of As (10 mg/L) and MgO NPs (50 mg/L) as compared to only As (10 mg/L) treatment. Additionally, As exposure resulted in declined primary metabolites such as soluble sugars and protein. However, the application of MgO NPs exhibited the alleviation of As toxicity through significant (p < 0.05) reduction of As accumulation by 34 and 53% in roots and 44 and 62% in shoots of rice seedlings under 50 and 100 mg/L MgO NPs supplementations, respectively and restored the accumulation of the primary metabolites. Furthermore, MgO NPs demonstrated the ability to scavenge reactive oxygen species (ROS) like hydrogen peroxide (H2O2) and superoxide anion (O2•-), through significant (p < 0.05) promotion of non-enzymatic (carotenoid, anthocyanin, flavonoid, and proline) and enzymatic (CAT, POD, and SOD) antioxidant defence under As stress. These findings highlighted the potential of green synthesized MgO NPs towards the mitigation of As contamination in rice plants. However, future study is necessary to unfold the actual mechanisms responsible for the protective effects of MgO NPs and to screen out the optimal dose to be used to formulate a potent nanofertilizer for sustainable rice production in metal-contaminated soils.

Effects of CuO nanoparticles in composted sewage sludge on rice-soil systems and their potential human health risks

The release of metal-based nanoparticles (MNPs) into sewage systems is worrisome due to their potential impact on crop-soil systems that are amended with sewage sludge. This study aimed to investigate the effects of copper oxide nanoparticles (CuO NPs) in composted sewage sludge (CSS) on rice-soil systems and to assess the health risks associated with consuming CuO NP-contaminated rice produced by CSS amendment. CSS was treated with three doses of CuO NPs, resulting in Cu levels below the sludge limits (1500 mg Cu kg-1) for reuse as a soil amendment. Results showed that CuO NPs in CSS at environmentally acceptable levels had no negative effect on rice growth and yield. In fact, they enhanced biomass production, tillering capacity, and soil fertility by increasing N and K levels in the soil. In addition, CuO NPs in CSS (450-1450 mg Cu kg-1) promoted the accumulation of macro- and micro-minerals in rice grains, thereby improving the nutritional value of rice. However, Cu contamination in CSS led to elevated levels of toxic metals, especially As, in rice grains, posing potential health risks to both adults and children. In the presence of higher CuO NPs contamination in CSS, the hazard quotient of As exceeded one, indicating an increased risks of toxic metal exposure via rice consumption. This study raises concerns about potential long-term threats to human health posed by MNPs contamination in CSS and highlights the need to reevaluate the permissible limits of hazardous elements in sludge to ensure its safe reuse in agriculture.

Use of metal nanoparticles in agriculture. A review on the effects on plant germination

Agricultural nanotechnology has become a powerful tool to help crops and improve agricultural production in the context of a growing world population. However, its application can have some problems with the development of harvests, especially during germination. This review evaluates nanoparticles with essential (Cu, Fe, Ni and Zn) and non-essential (Ag and Ti) elements on plant germination. In general, the effect of nanoparticles depends on several factors (dose, treatment time, application method, type of nanoparticle and plant). In addition, pH and ionic strength are relevant when applying nanoparticles to the soil. In the case of essential element nanoparticles, Fe nanoparticles show better results in improving nutrient uptake, improving germination, and the possibility of magnetic properties could favor their use in the removal of pollutants. In the case of Cu and Zn nanoparticles, they can be beneficial at low concentrations, while their excess presents toxicity and negatively affects germination. About nanoparticles of non-essential elements, both Ti and Ag nanoparticles can be helpful for nutrient uptake. However, their potential effects depend highly on the crop type, particle size and concentration. Overall, nanotechnology in agriculture is still in its early stages of development, and more research is needed to understand potential environmental and public health impacts.

Zn nutrients-loaded chitosan nanocomposites and their efficacy as nanopriming agents for maize (Zea mays) seeds

Recent breakthroughs in agro-inputs research have led to the development of nanomaterials that can promote precision agriculture and better environmental security. The agricultural sector is increasingly facing the negative impacts of changing climates due to various stress conditions. To curb this scenario, economical and low-risk practices such as decreasing fertilizer inputs and seed priming have been promoted. In the current study, the H. odoratissimum aqueous extract was used to nucleate the Zn ionic species and grow the zinc oxide nanoparticles (ZnO NPs). The developed nanocomposites and their ionic zinc precursor were then integrated into tripolyphosphate (TPP)-crosslinked chitosan (CS/TPP) nanostructures by ionic gelation. Advanced physicochemical characterization techniques (SEM, EDS, TEM, DLS, FTIR, TGA, and XPS) were exploited to report the morphology, hydrodynamic size, surface charge, and structural organization of the developed nanomaterials. These revealed positively charged particles with hydrodynamic size in the 149-257 nm range. The NPs were used as priming agents for Zea mays seeds. At 0.04%, the ZnO-loaded CS/TPP NPs achieved higher root and shoot elongation in 10-day old seedlings compared to other treatments. The pristine CS/TPP NPs, Zn(II)-laden CS/TPP NPs, and ZnO-loaded CS/TPP NPs at 0.01% significantly promoted the early seedling development of seeds under salt stress. This represents the first report showing ZnO integrated chitosan nanocomposites as an auspicious nanopriming agent for stimulating the seed germination of maize. The study envisages offering perspectives on utilizing green nanotechnology to improve the early seedling development of maize. Furthermore, it has the potential to contribute towards UN SDG 2, thus addressing the threats to global food insecurity and doubling agricultural productivity by 2030.

Possibility to Apply Strontium Aluminate to Produce Light-Emitting Plants: Efficiency and Safety

Light-emitting plants (LEPs) provides light in areas without electricity. The phosphorescent compound was used as a lighting material for LEP development. However, using the phosphorescent compound for LEPs development required optimization and phytotoxicity evaluation. Strontium aluminate (SrAl2 O4 ) is a phosphorescent compound that can glow for a long time and is easily recharged by visible light. In this study, using SrAl2 O4 to develop LEPs was evaluated. Additionally, plant stress under SrAl2 O4 was investigated. Metabolomic analysis can explain the possible mechanism of plants' stress under SrAl2 O4 . After, injecting 3 mL of 5 % (w/v) SrAl2 O4 products 1, 2, and 3 into the stem of Ipomoea aquatica, the result showed that SrAl2 O4 products 2 and 3 caused oxidative stress. The metabolomic analysis also indicated that I. aquatica responded to SrAl2 O4 product 1 by increasing pipecolic acid and salicylic acid, while I. aquatica injected with SrAl2 O4 products 2 and 3 showed a decrease in salicylic acid around 0.005 and 0.061-fold, respectively, compared to control plants. and an excess accumulation of MDA around 10.00-12.00 μmol g-1 FW. A 15 % concentration of SrAl2 O4 can be used for LEPs development, enabling photoemission 18-fold for 50 min. SrAl2 O4 product 1 has the potential to be a material for LEPs.

Interference Effects of Commercial Persistent Luminescence Materials on Rice Germination and Seedling Growth

Persistent luminescence materials (PLMs) are widely used across a multitude of fields due to their distinct optical properties. However, like other micron-sized materials such as microplastics, the production and recycling processes of PLMs can lead to their accumulation in soil and water, potentially posing detrimental effects on plant growth and development. In this study, we investigated the impact of commercially available blue PLM (bPLM), green PLM (gPLM), and red PLM (rPLM) on germination, seedling growth, and oxidative stress responses in rice. Our findings demonstrate that the morphology and size of PLMs do not significantly differ in their effects on rice growth. All three types of PLMs significantly inhibited root length and stem length, disrupted root cell structures, and decreased seedling biomass. Interestingly, gPLM and bPLM were found to stimulate the synthesis of osmolytes and chlorophyll in rice, while rPLM had the opposite effect. Changes in the antioxidant enzyme system in rice clearly indicated that the three types of PLMs induced reactive oxygen species (ROS) damage in rice. This study enhances our understanding of the potential environmental impacts of PLMs, offering valuable insights for the safe and responsible use of these materials in various applications.

Physiological and Biochemical Properties of Cotton Seedlings in Response to Cu2+ Stress

Copper(II) (Cu²⁺) is essential for plant growth and development. However, high concentrations are extremely toxic to plants. We investigated the tolerance mechanism of cotton under Cu²⁺ stress in a hybrid cotton variety (Zhongmian 63) and two parent lines with different Cu²⁺ concentrations (0, 0.2, 50, and 100 μM). The stem height, root length, and leaf area of cotton seedlings had decreased growth rates in response to increasing Cu²⁺ concentrations. Increasing Cu²⁺ concentration promoted Cu²⁺ accumulation in all three cotton genotypes' roots, stems, and leaves. However, compared with the parent lines, the roots of Zhongmian 63 were richer in Cu²⁺ and had the least amount of Cu²⁺ transported to the shoots. Moreover, excess Cu²⁺ also induced changes in cellular redox homeostasis, causing accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Conversely, antioxidant enzyme activity increased, while photosynthetic pigment content decreased. Our findings indicated that the hybrid cotton variety fared well under Cu²⁺ stress. This creates a theoretical foundation for the further analysis of the molecular mechanism of cotton resistance to copper and suggests the potential of the large-scale planting of Zhongmian 63 in copper-contaminated soils.

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.

Foliar application of silicon-based nanoparticles improve the adaptability of maize (Zea mays L.) in cadmium contaminated soils

Heavy metals (HMs) especially cadmium (Cd) absorbed by the roots of crop plants like maize have emerged as one of the most serious threats by causing stunted plant growth along with disturbing the photosynthetic machinery and nutrient homeostasis process. A trial was conducted for inducing Cd stress tolerance in maize by exogenous application of silicon nanoparticles (SiNPs) using five doses of SiNPs (0, 100, 200, 300, and 400 ppm) and three levels of Cd (0, 15, and 30 ppm) for maize hybrid (SF-9515). The response variables included morphological traits and biochemical parameters of maize. The results indicated that Cd level of 30 ppm remained the most drastic for maize plants by recording the minimum traits such as shoot length (39.35 cm), shoot fresh weight (9.52 g) and shoot dry weight (3.20 g), leaf pigments such as chlorophyll a (0.55 mg/g FW), chlorophyll b (0.27 mg/g FW), total contents (0.84 mg/g FW), and carotenoid contents (0.19 µg/g FW). Additionally, the same Cd level disrupted biochemical traits such as TSP (4.85 mg/g FW), TP (252.94 nmol/g FW), TSAA (18.92 µmol g^-1 FW), TSS (0.85 mg/g FW), and antioxidant activities such as POD (99.39 min^-1 g^-1 FW), CAT (81.58 min^-1 g^-1 FW), APX (2.04 min^-1 g^-1 FW), and SOD (172.79 min^-1 g^-1 FW). However, a higher level of Cd resulted in greater root length (87.63 cm), root fresh weight (16.43 g), and root dry weight (6.14 g) along with higher Cd concentration in the root (2.52 µg/g^-1) and shoot (0.48 µg/g^-1). The silicon nanoparticles (Si NPs) treatment significantly increased all measured attributes of maize. The highest value was noted of all the parameters such as chlorophyll a (0.91 mg/g FW), chlorophyll b (0.57 mg/g FW), total chlorophyll contents (1.48 mg/g FW), total carotenoid contents (0.40 µg/g FW), TSP (6.12 mg/g FW), TP (384.56 nmol/g FW), TSAA (24.64 µmol g^-1 FW), TSS (1.87 mg/g FW), POD (166.10 min^-1 g^-1 FW), CAT (149.54 min^-1 g^-1 FW), APX (3.49 min^-1 g^-1 FW), and SOD (225.57 min^-1 g^-1 FW). Based on recorded findings, it might be inferred that higher levels of Cd tend to drastically reduce morpho-physiological traits of maize and foliage-applied silver nanoparticles hold the potential to ameliorate the adverse effect of Cd stress on maize.

Trichoderma asperellum L. Coupled the Effects of Biochar to Enhance the Growth and Physiology of Contrasting Maize Cultivars under Copper and Nickel Stresses

Crop cultivation in heavy metal (HM)-polluted soils is a routine practice in developing countries that causes multiple human health consequences. Hence, two independent studies have been performed to investigate the efficiency of rice husk biochar (BC) and three fungal species, Trichoderma harzianum (F1), Trichoderma asperellum (F2) and Trichoderma viride (F3), to improve the growth and physiology of Zea mays L. plants grown on soil contaminated with Cu and Ni. Initially, a biosorption trial was conducted to test the HM removal efficiency of species F1, F2 and F3. Among them, F2 sp. showed the maximum Cu and Ni removal efficiency. Then, a pot study was conducted with two cultivars (spring corn and footer corn) having eleven treatments with three replicates. The results demonstrated a significant genotypic variation among both cultivars under applied HM stress. The maximum decreases in leaf Chl a. (53%), Chl b. (84%) and protein (63%) were reported in footer corn with applied Cu stress. The combined application of biochar and F2 increased leaf CAT (96%) in spring corn relative to Cu stress. Altogether, it was found that BC + F2 treatment showed the maximum efficiency in combatting Cu and Ni stress in spring corn.

Potential Effects of Metal Oxides on Agricultural Production of Rice: A Mini Review

The extensive usage of metal oxide nanoparticles has aided in the spread and accumulation of these nanoparticles in the environment, potentially endangering both human health and the agroecological system. This research describes in detail the hazardous and advantageous impacts of common metal oxide nanomaterials, such as iron oxide, copper oxide, and zinc oxide, on the life cycle of rice. In-depth analyses are conducted on the transport patterns of nanoparticles in rice, the plant's reaction to stress, the reduction of heavy metal stress, and the improvement of rice quality by metal oxide nanoparticles, all of which are of significant interest in this subject. It is emphasized that from the perspective of advancing the field of nanoagriculture, the next stage of research should focus more on the molecular mechanisms of the effects of metal oxide nanoparticles on rice and the effects of combined use with other biological media. The limitations of the lack of existing studies on the effects of metal oxide nanomaterials on the entire life cycle of rice have been clearly pointed out.

Melatonin-mediated resistance to copper oxide nanoparticles-induced toxicity by regulating the photosynthetic apparatus, cellular damages and antioxidant defense system in maize seedlings

The pollution of nanoparticles (NPs) has linked with severe negative effects on crop productivity. Thus, effective strategies are needed to mitigate the phytotoxicity of NPs. The aim of present study was to evaluate the efficacy of exogenously applied melatonin (MT) in mitigating the toxic effects of copper oxide nanoparticles (CuO NPs) from maize seedlings. Therefore, we comprehensively investigated the inhibitory effects of MT against CuO NPs-induced toxicity on morpho-physiological, biochemical and ultrastructural levels in maize. Our results show that CuO NPs (300 mg L^-1) exposure displayed significantly reduction in all plant growth traits and induced toxicity in maize. Furthermore, 50 μM MT provided maximum plant tolerance against CuO NPs-induced phytotoxicity. It was noticed that MT improved plant growth, biomass, photochemical efficiency (Fv/Fm), chlorophyll contents (Chl a and Chl b), SPAD values and gas exchange attributes (stomatal conductance, net photosynthetic rate, intercellular CO₂ concentration and transpiration rate) under CuO NPs stress. In addition, MT enhanced the antioxidant defense system and conferred protection to ultrastructural (mainly chloroplast, thylakoids membrane and plastoglobuli) damages and stomatal closure in maize plants subjected to CuO NPs stress. Together, it can be stated that the exogenous supply of MT improves the resilience of maize plants against the CuO NPs-induced phytotoxicity. Our current findings can be useful for the enhancement of plant growth and yield attributes in CuO NPs-contaminated soils. The reported information can provide insight into the MT pathways that can be used to improve crop stress tolerance in a challenging environment.

CuO nanoparticles in irrigation wastewater have no detrimental effect on rice growth but may pose human health risks

The possibility of metal-based nanoparticles (NPs) being released into agricultural soils via sewage systems has raised widespread concern about their negative effects on crop plants, soils, and potential risks to human health via the food chain. The objectives of this study were to (i) determine the effect of CuO NPs in irrigation water on plant growth and Cu accumulation in a rice-soil system using continuous sub-irrigation with treated wastewater (CSI), and (ii) assess the Cu exposure and potential health risk associated with rice consumption. CuO NPs were examined in treated municipal wastewater (TWW) at environmentally acceptable concentrations (0, 0.02, 0.2, and 2.0 mg Cu L^-1), allowing for effluent discharge and/or crop irrigation reuse. Low CuO NP concentrations in TWW had no adverse effect on plant growth, yield, or grain quality. Cu accumulation significantly increased in various parts of rice plants and paddy soils at 2.0 mg Cu L^-1. CuO NPs had no discernible effect on rice plants when compared to CuSO₄ at 0.2 mg Cu L^-1. The estimated daily intake of Cu derived from inadvertent consumption of Cu-contaminated rice (by CuO NPs in TWW) for young children aged 0-6 years exceeded the oral reference dose for toxicity. Overall, we found no acute toxicity of CuO NPs in TWW to rice plants, but significant Cu accumulation in grains. This implies that there is a high risk of human health problems associated with rice that was intensively irrigated with TWW containing CuO NPs.

The emergence of metal oxide nanoparticles (NPs) as a phytomedicine: A two-facet role in plant growth, nano-toxicity and anti-phyto-microbial activity

Anti-microbial resistance (AMR) has recently emerged as an area of high interest owing to the rapid surge of AMR phenotypes. Metal oxide NPs (MeONPs) have been identified as novel phytomedicine and have recently peaked a lot of interest due to their potential applications in combating phytopathogens, besides enhancing plant growth and yields. Numerous MeONPs (Ti₂O, MgO, CuO, Ag₂O, SiO₂, ZnO, and CaO) have been synthesized and tested to validate their antimicrobial roles without causing toxicity to the cells. This review discusses the application of the MeONPs with special emphasis on anti-microbial activities in agriculture and enlists how cellular toxicity caused through reactive oxygen species (ROS) production affects plant growth, morphology, and viability. This review further highlights the two-facet role of silver and copper oxide NPs including their anti-microbial applications and toxicities. Furthermore, the factor modulating nanotoxicity and immunomodulation for cytokine production has also been discussed. Thus, this article will not only provide the researchers with the potential bottlenecks but also emphasizes a comprehensive outline of breakthroughs in the applicability of MeONPs in agriculture.

Responses of soybean (Glycine max [L.] Merr.) to zinc oxide nanoparticles: Understanding changes in root system architecture, zinc tissue partitioning and soil characteristics

Addressing global Zinc (Zn) deficiency in food and feed requires innovation in Zn fertilizer. Recently, Zn oxide nanoparticles (ZnONPs) have piqued interest for potential use as a novel nano-Zn fertilizer. However, little is known about potential factors influencing ZnONPs partitioning in different plant tissues, and changes in root system architecture (RSA) and soil characteristics. Herein, we tested the effects of particle size (38, 59, and > 500 nm) and concentration (0-500 mg/kg) of ZnONPs on Zn bioaccumulation in multiple tissues in soil-grown soybean (Glycine max) grown for 120 days, including changes in RSA (root biomass, length, area, volume, and density) and soil characteristics (pH and electrical conductance [EC]). Our results showed significant effects of Zn compound types, Zn concentrations and their interaction on RSA, and Zn uptake by root, stem, leaf, and seed, in soybean. Concentration-response curves for root structures with varied sized ZnONPs and Zn2+ ions were deemed nonlinear, whereas for Zn distribution between different tissues the concentration-response curves were linear. Interestingly, ZnONPs and Zn2+ ions up to 200 mg/kg showed beneficial effects on root growth and development, but toxic response was observed at higher concentrations for both compounds. Root dry weight, length, volume, and area with 200 mg/kg ZnONPs-38 nm were higher by 48%, 56%, 33% and 44%, respectively, compared to control, and were higher by 15%, 23%, 15% and 19%, respectively, compared to 200 mg/kg ZnCl2. In general, soybean responses to the smallest size ZnONPs-38 nm were higher for all parameters evaluated compared to the larger-sized ZnONPs (59 and > 500 nm) and Zn2+ ions. Zn bioaccumulation varied among tissues in the order: root > seed > leaf > stem. A minor but steady decrease in soil pH and EC occurred among different concentrations for both ZnONPs and Zn2+ ions. Improved RSA can facilitate water and nutrient uptake in soybean, promoting growth and yield, especially considering arid and semi-arid climates where water is a limiting factor. Further, improving seed and shoot Zn levels, as demonstrated herein using ZnONPs, is paramount to addressing Zn deficiency in food and feed. Future studies assessing potential impacts on soil microbes, soil health and food safety upon ZnONPs application is critical for risk assessment of the novel nanofertilizer.

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.

Nanofertilizers for agricultural and environmental sustainability

Indiscriminate use of chemical fertilizers in the agricultural production systems to keep pace with the food and nutritional demand of the galloping population had an adverse impact on ecosystem services and environmental quality. Hence, an alternative mechanism is to be developed to enhance farm production and environmental sustainability. A nanohybrid construct like nanofertilizers (NFs) is an excellent alternative to overcome the negative impact of traditional chemical fertilizers. The NFs provide smart nutrient delivery to the plants and proves their efficacy in terms of crop productivity and environmental sustainability over bulky chemical fertilizers. Plants can absorb NFs by foliage or roots depending upon the application methods and properties of the particles. NFs enhance the biotic and abiotic stresses tolerance in plants. It reduces the production cost and mitigates the environmental footprint. Multitude benefits of the NFs open new vistas towards sustainable agriculture and climate change mitigation. Although supra-optimal doses of NFs have a detrimental effect on crop growth, soil health, and environmental outcomes. The extensive release of NFs into the environment and food chain may pose a risk to human health, hence, need careful assessment. Thus, a thorough review on the role of different NFs and their impact on crop growth, productivity, soil, and environmental quality is required, which would be helpful for the research of sustainable agriculture.

Phytoremediation of copper-contaminated soil by Artemisia absinthium: comparative effect of chelating agents

Phytoremediation is a promising method for the removal of toxic trace elements, specifically of copper, from the contaminated soil in the mining regions of Armenia. Thereby, the objectives of our study were the assessment of copper accumulation capacity and phytoremediation suitability of wormwood (Artemisia absinthium L.), a potential metal hyperaccumulator, as well as the identification of the influence of some chelating agents and their combinations on copper phytoremediation effectiveness. The results of studies have shown that A. absinthium is a relatively well-adapted plant species with the ability to grow in copper-contaminated soils collected from the surroundings of Zangezur Copper and Molybdenum Combine (south-east of Armenia). The observed decrease in plant growth in contaminated soil was possible to restore by the use of ammonium nitrate. It was revealed that for the remediation of copper-contaminated soils by phytostabilisation method, A. absinthium could be grown without the application of chelating agents, as being a perennial herb, it is able to accumulate relatively high contents of copper in its root and do not transfer this metal to the above-ground part at the same time. As opposed to the phytostabilisation method, for the cleaning of copper-contaminated soils through phytoextraction method by A. absinthium, the application of chemical amendments is needed for the enhancement of copper bioavailability and for its intensive transportation to the above-ground part of the plant. Collating the effects of various chemical agents on the plant, we concluded that the growth scheme, when the application of NH₄NO₃, a promoter of plant growth, is combined with the joint use of citric and malic acids, can be applied as the most expedient approach for remediation of copper-contaminated soils by phytoextraction method.

Impact of engineered nanomaterials on rice (Oryza sativa L.): A critical review of current knowledge

After use, a large number of engineered materials (ENMs) are directly or indirectly released into the environment. This may threaten the agricultural ecosystem, especially with crops under high demand for irrigation water, such as rice (Oryza sativa L.), a crop that feeds nearly half of the world's population. However, consistent and detailed information on the effects of nanoparticles in rice is limited. This review is a systematic exploration of the effects of ENMs on rice, with a critical evaluation of the mechanisms reported in the literature by which different nanomaterials cause toxicity in rice. The physiological and biochemical effects engendered by the nanoparticles are highlighted, focusing on rice growth and development, ENMs uptake and translocation, gene expression changes, enzyme activity modifications, and secondary metabolite alterations.

Microbe-oriented nanoparticles as phytomedicines for plant health management: An emerging paradigm to achieve global food security

Biotic and abiotic environmental stresses affect the production and quality of agricultural products worldwide. The extensive use of traditional preventive measures comprising toxic chemicals has become more problematic due to severe ecotoxicological challenges. To address this issue, engineered nanoparticles (NPs) with their distinct physical and chemical properties has gained scientific attention and can help plants to confront environmental challenges. Despite their ameliorative and beneficial effects, toxicological concerns have been raised about NPs. The recent development of biogenic NPs (bio-NPs) is getting attention in agriculture due to their diverse biocompatibility, better functional efficacy, and eco-friendly nature compared to the recalcitrant NPs, providing a promising strategy for increased crop protection against biotic and abiotic environmental stresses, with the ultimate goal of ensuring global food security. This review summarizes the recent advances in the engineering of bio-NPs with particular emphasis on the functions of bio-NPs in protecting plants from biotic and abiotic environmental stresses, delivery and entry routes of NPs to plant systems, nanotoxicity, and plant physiological/biochemical responses to nanotoxicity. Future perspectives of bio-NP-enabled strategies, remaining pitfalls, and possible solutions to combat environmental challenges via advanced nanotechnology to achieve global food security and a sustainable agricultural system are also discussed.

Copper oxide (CuO) nanoparticles affect yield, nutritional quality, and auxin associated gene expression in weedy and cultivated rice (Oryza sativa L.) grains

Weedy rice grows competitively with cultivated rice and significantly diminishes rice grain production worldwide. The different effects of Cu-based nanomaterials on the production of weedy and cultivated rice, especially the grain qualities are not known. Grains were collected from weedy and cultivated rice grown for four months in field soil amended with nanoscale CuO (nCuO), bulk CuO (bCuO), and copper sulfate (CuSO₄) at 0, 75, 150, 300, and 600 mg Cu/kg soil. Cu translocation, essential element accumulation, yield, sugar, starch, protein content, and the expression of auxin associated genes in grains were determined. The grains of weedy and cultivated rice were differentially impacted by CuO-based compounds. At ≥300 mg/kg, nCuO and bCuO treated rice had no grain production. Treatment at 75 mg/kg significantly decreased grain yield as compared to control with the order: bCuO (by 88.7%) > CuSO₄ (by 47.2%) ~ nCuO (by 38.3% only in cultivated rice); at the same dose, the Cu grain content was: nCuO ~ CuSO₄ > bCuO > control. In weedy grains, K, Mg, Zn, and Ca contents were decreased by 75 and 150 mg/kg nCuO by up to 47.4%, 34.3%, 37.6%, and 60.0%, but no such decreases were noted in cultivated rice, and Fe content was increased by up to 88.6%, and 53.2%. In rice spikes, nCuO increased Mg, Ca, Fe, and Zn levels by up to 118.1%, 202.6%, 133.8%, and 103.9%, respectively. Nanoscale CuO at 75 and 150 mg/kg upregulated the transcription of an auxin associated gene by 5.22- and 1.38-fold, respectively, in grains of weedy and cultivated rice. The biodistribution of Cu-based compounds in harvested grain was determined by two-photon microscopy. These findings demonstrate a cultivar-specific and concentration-dependent response of rice to nCuO. A potential use of nCuO at 75 and 150 mg/kg in cultivar-dependent delivery system was suggested based on enhanced grain nutritional quality, although the yield was compromised. This knowledge, at the physiological and molecular level, provides valuable information for the future use of Cu-based nanomaterials in sustainable agriculture.

A comprehensive review of impacts of diverse nanoparticles on growth, development and physiological adjustments in plants under changing environment

The application of nanotechnology in agriculture includes the use of nanofertilizers, nanopesticides, and nanoherbicides that enhance plant nutrition without disturbing the soil texture and protect it against microbial infections. Thus, nanotechnology maintains the plant's health by maintaining its soil health. The use of nanoparticles (NPs) in agriculture reduces the chemical spread and nutrient loss and boosts crop yield and productivity. Effect of NPs varies with their applied concentrations, physiochemical properties, and plant species. Various NPs have an impact on the plant to increase biomass productivity, germination rate and their physiology. Also, NPs change the plant molecular mechanisms by altering gene expression. Metal and non-metal oxides of NPs (Au, Ag, ZnO, Fe₂O₃, TiO₂, SiO₂, Al₂O₃, Se, carbon nanotubes, quantum dots) exert an important role in plant growth and development and perform an essential role in stress amelioration. On the other hand, other effects of NPs have also been well investigated by observing their role in growth suppression and inhibition of chlorophyll and photosynthetic efficiency. In this review, we addressed a description of studies that have been made to understand the effects of various kind of NPs, their translocation and interaction with the plants. Also, the phytoremediation approaches of contaminated soil with combined use of NPs for sustainable agriculture is covered.

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.

Effect of ZnO Nanoparticles on Growth and Biochemical Responses of Wheat and Maize

Zinc is an essential element that is also renowned for widespread contamination and toxicity at high concentrations. The present study was carried out to analyze the responses induced by lower, as well as higher, doses of zinc (0-200 mg/L), in the form of zinc oxide nanoparticles (ZnO NPs) in wheat and maize, for a period of 21 days. Accumulation of zinc increases with increasing Zn doses in both wheat and maize, with higher doses being in wheat (121 mg/kg in root and 66 mg/kg in shoot) than in maize (95 mg/kg in root and 48 mg/kg in shoot). The activity of alpha-amylase showed increase, while that of dehydrogenase decline, in response to ZnO NPs. The length and biomass of plants and photosynthetic pigments increased slightly upon ZnO NPs supply. Malondialdehyde content showed a progressive increase in root and shoot of both plants. However, in response, antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase) showed increase up to lower concentrations (100 mg/L) of ZnO NPs but decline variably at higher levels (150-200 mg/L) in wheat and maize. The results suggest that lower supply of ZnO NPs (100 mg/L) could be stimulatory to the growth of plants and can be recommended as a Zn fertilizer source for crop production.

Differential bioaccumulations and ecotoxicological impacts of metal-oxide nanoparticles, bulk materials, and metal-ions in cucumbers grown in sandy clay loam soil

Expanding applications of metal-oxide nanoparticles (NPs) and increased environmental deposition of NPs followed by their interactions with edible crops threaten yields. This study demonstrates the effects of aging (45 days in soil) of four NPs (ZnO, CuO, Al₂O₃, TiO₂; 3.9-34 nm) and their corresponding metal oxide bulk particles (BPs; 144-586 nm) on cucumbers (Cucumis sativus L.) cultivated in sandy-clay-loam field soil and compares these with the phytotoxic effects of readily soluble metal salts (Zn²⁺, Cu²⁺, and Al³⁺). Data revealed the cell-to-cell translocations of NPs, their attachments to outer and inner cell surfaces, nuclear membranes, and vacuoles, and their upward movements to aerial parts. Metal bioaccumulations in cucumbers were found in the order: (i) ZnO-NPs > ZnO-BPs > Zn²⁺, (ii) CuO-NPs > CuO-BPs > Cu²⁺, (iii) Al³⁺> Al₂O₃-NPs > Al₂O₃-BPs and (iv) TiO₂-NPs > TiO₂-BPs. Aging of NPs in soil for 45 days significantly enhanced metal uptake (P ≤ 0.05), for instance aged ZnO-NPs at 1 g kg^-1 increased the uptake by 20.7 % over non-aged ZnO-NPs. Metal uptakes inhibited root (RDW) and shoot (SDW) dry weight accumulations. For Cu species, maximum negative impact (%) was exhibited by Cu²⁺ (RDW:SDW = 94:65) followed by CuO-NPs (RDW:SDW = 78:34) and CuO-BPs (RDW:SDW = 27:22). Aging of NPs/BPs at 1-4 g kg^-1 further enhanced the toxic impact of tested materials on biomass accumulations and chlorophyll formation. NPs also induced membrane damage of root tissues and enhanced levels of antioxidant enzymes. The results of this study suggest that care is required when aged metal-oxide NPs of both essential (Zn and Cu) and non-essential (Al and Ti) metals interact with cucumber plants, especially, when they are used for agricultural purposes.

Silica nanoparticles as pesticide against insects of different feeding types and their non-target attraction of predators

The agricultural use of silica (SiO2) nanoparticles (NPs) has the potential to control insect pests while the safety and tritrophic effects on plants and beneficial natural enemies remains unknown. Here, we evaluate the effects of silica NPs on insect pests with different feeding niches, natural enemies, and a plant. Silica NPs were applied at different concentrations (75-425 mg/L) on field-cultivated faba bean and soybean for two growing seasons. The faba bean pests, the cowpea aphid Aphis craccivora and the American serpentine leafminer Liriomyza trifolii, and the soybean pest, the cotton leafworm Spodoptera littoralis, were monitored along with their associated predators. Additional laboratory experiments were performed to test the effects of silica NPs on the growth of faba bean seedlings and to determine whether the rove beetle Paederus fuscipes is attracted to cotton leafworm-infested soybean treated with silica NPs. In the field experiments, silica NPs reduced the populations of all three insect pests and their associated predators, including rove beetles, as the concentration of silica NPs increased. In soybean fields, however, the total number of predators initially increased after applying the lowest concentration. An olfactometer-based choice test found that rove beetles were more likely to move towards an herbivore-infested plant treated with silica NPs than to a water-treated control, suggesting that silica NPs enhance the attraction of natural enemies via herbivore-induced plant volatiles. In the laboratory, while silica NPs inhibited the development of faba bean roots at 400 mg/L, they did not affect germination percentage, germination time, shoot length, or vigor index compared to the control.

Mobility of arsenic in the growth media of rice plants (Oryza sativa subsp. japonica. 'Koshihikari') with exposure to copper oxide nanoparticles in a life-cycle greenhouse study

The increasing arsenic (As) concentration in agriculture media poses increasing risks to both environment and human health. Arsenic mobility determines its bioavailability and entry into the food chain. Nanoparticle application may help to control As mobility in crop cultivation media, and thus decreasing As bioavailability for plants. This research studied the adsorption kinetics of As(V) on copper oxide nanoparticles (nCuO) and nCuO dissolution in a hydroponic solution, and the effects of nCuO on As mobility in a greenhouse system exposed to As(V) addition of 10 mg/kg and nCuO at 0.1-100 mg/L for a life-cycle growth of rice. Arsenic adsorption was dependent on both the total mass and the concentration of nCuO as well as the initial concentration of As(V), while nCuO dissolution was mainly dependent on nCuO concentration regardless of As(V). Arsenic in the simulated paddy was quickly mobilized from soil to aqueous phase during week 1, and further interacted with components in water phase, sediment-water interfacial transition and rice plants. Copper (Cu) and As speciation in the soil were observed by X-Ray Absorption Near Edge Spectrometry. Dissolved Cu was complexed with organic ligands. As(V) was adsorbed to kaolinite, or reduced to As(III) and adsorbed to ferrihydrite. Percent As removal from water phase in the growth container was determined by both nCuO application and As(V) initial concentration. Based on our previous finding that As accumulation in rice grains was significantly decreased by nCuO at 50 mg/L and the results of this study on As adsorption capacity of nCuO and As removal from water due to nCuO application, nCuO at 50 mg/L was proposed to be an appropriate application in rice paddy to immobilize As. Further research is needed in actual agriculture to verify the appropriate nCuO application and get an integrated beneficial effect for rice plants and humans.

Effect of different copper oxide particles on cell division and related genes of soybean roots

In this study, soybean (Glycine max) seeds were cultured in distilled water. When the roots were about 2 cm, they were separately treated with copper oxide bulk particles (CuO BPs) suspensions and copper oxide nanoparticle (CuO NPs) suspensions in different concentrations (2, 5 and 10 mg L-1) for 24 h and 48 h. Results showed that different concentrations of CuO BPs suspensions had little effect on the structure and cell division of meristematic zone. After CuO NPs treatment, Cu content increased in the roots, accompanied by high reactive oxygen species, malondialdehyde and relative electrical conductivity. CuO NPs significantly inhibited the growth of soybean roots over exposure time and the concentration. The destruction of CuO NPs occurred first in the promeristem, and then in the primary meristem of the meristematic zone. The meristematic cells of roots showed vacuolization, the nuclei swelled and deformed. After 10 mg L-1 CuO NPs treatment for 48 h, the mitotic index of root cells decreased by 14.28%, and the micronucleus rate increased by 14.33‰. Some cell division genes, such as GmCYCB1; 2, GmCYCU4; 1, GmCYCA1; 1, GmCYCP3; 1, GmCYCD3; 1 and CDC20; 1 were up-regulated or down-regulated with CuO NPs treatments.

Zinc Oxide Nanoparticles Alleviate Chilling Stress in Rice (Oryza Sativa L.) by Regulating Antioxidative System and Chilling Response Transcription Factors

As one of the common abiotic stresses, chilling stress has negative effects on rice growth and development. Minimization of these adverse effects through various ways is vital for the productivity of rice. Nanoparticles (NPs) serve as one of the effective alleviation methods against abiotic stresses. In our research, zinc oxide (ZnO) NPs were utilized as foliar sprays on rice leaves to explore the mechanism underlying the effect of NPs against the negative impact of chilling stress on rice seedlings. We revealed that foliar application of ZnO NPs significantly alleviated chilling stress in hydroponically grown rice seedlings, including improved plant height, root length, and dry biomass. Besides, ZnO NPs also restored chlorophyll accumulation and significantly ameliorated chilling-induced oxidative stress with reduced levels of H₂O₂, MDA, proline, and increased activities of major antioxidative enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). We further found that foliar application of ZnO NPs induced the chilling-induced gene expression of the antioxidative system (OsCu/ZnSOD1, OsCu/ZnSOD2, OsCu/ZnSOD3, OsPRX11, OsPRX65, OsPRX89, OsCATA, and OsCATB) and chilling response transcription factors (OsbZIP52, OsMYB4, OsMYB30, OsNAC5, OsWRKY76, and OsWRKY94) in leaves of chilling-treated seedlings. Taken together, our results suggest that foliar application of ZnO NPs could alleviate chilling stress in rice via the mediation of the antioxidative system and chilling response transcription factors.

OsFTIP7 determines metallic oxide nanoparticles response and tolerance by regulating auxin biosynthesis in rice

The widely application of metallic oxide nanoparticles (NPs) has led to an increase in their accumulation in farmland. Previous studies have found that the metallic oxide NPs have negative effect on plants development and growth. Nonetheless, the underlying mechanism of response to metallic oxide NPs in rice remains elusive. In this study, we show that rice FT-INTERACTING PROTEIN 7 (OsFTIP7) plays an essential role in NPs of CuO and ZnO-mediated physiological and biochemical changes in rice. Loss of function of OsFTIP7 reduced the toxicity of the NPs of CuO and ZnO to the seedlings by accumulating more biomass and chlorophyll contents. Furthermore, after high exposure to metallic oxide NPs, more indole-3-acetic acid (IAA) were determined in Osftip7 with higher expression of auxin biosynthetic genes than the control seedlings. What's more, IAA-treated seedlings displayed the similar phenotype as Osftip7 under high concentrations of NPs of CuO and ZnO. Taken together, the results substantiate that OsFTIP7 is involved in metallic oxide nanoparticle-mediated physiological and biochemical changes by negatively regulating auxin biosynthesis in rice.

Copper bioavailability, uptake, toxicity and tolerance in plants: A comprehensive review

Copper (Cu) is an essential element for humans and plants when present in lesser amount, while in excessive amounts it exerts detrimental effects. There subsists a narrow difference amid the indispensable, positive and detrimental concentration of Cu in living system, which substantially alters with Cu speciation, and form of living organisms. Consequently, it is vital to monitor its bioavailability, speciation, exposure levels and routes in the living organisms. The ingestion of Cu-laced food crops is the key source of this heavy metal toxicity in humans. Hence, it is necessary to appraise the biogeochemical behaviour of Cu in soil-plant system with esteem to their quantity and speciation. On the basis of existing research, this appraisal traces a probable connexion midst: Cu levels, sources, chemistry, speciation and bioavailability in the soil. Besides, the functions of protein transporters in soil-plant Cu transport, and the detrimental effect of Cu on morphological, physiological and nutrient uptake in plants has also been discussed in the current manuscript. Mechanisms related to detoxification strategies like antioxidative response and generation of glutathione and phytochelatins to combat Cu-induced toxicity in plants is discussed as well. We also delimits the Cu accretion in food crops and allied health perils from soils encompassing less or high Cu quantity. Finally, an overview of various techniques involved in the reclamation and restoration of Cu-contaminated soils has been provided.

Phytotoxicity of Y2O3 nanoparticles and Y3+ ions on rice seedlings under hydroponic culture

Due to the characteristics of both rare earth elements (REEs) and nanoparticles (NPs), Y₂O₃ NPs have been widely used in the fields of medicine, military industry, and agriculture, especially in the areas of electricity, light, magnetism, and catalysis. Given this widespread use, it is inevitable that Y₂O₃ NPs and soluble Y³⁺ will enter bodies of water through the processes involved in their preparation, application, and disposal. We sought to investigate the toxicities of Y₂O₃ NPs and Y³⁺ ions on rice seedlings (Oryza sativa L.), as well as the uptake and distribution of Y₂O₃ NPs under hydroponic conditions. Our results indicated that Y₂O₃ NPs and released Y³⁺ had no significant effect on the germination rate of rice. However, high concentrations of Y₂O₃ NPs (50 and 100 mg/L) delayed seed germination. As for rice root elongation, low concentrations (1, 5, and 10 mg/L) of Y₂O₃ NPs had a positive effect. Notably, when Y₂O₃ NPs concentration reached 20 mg/L and higher, root elongation was significantly inhibited. According to the physiological and biochemical characteristics of rice seedlings under Y stress, Y₂O₃ NPs ranging from 20 to 100 mg/L significantly reduced chlorophyll contents and root activity. Using ICP-MS and TEM analyses, Y₂O₃ NPs and Y³⁺ were shown to be mainly absorbed and accumulated in the roots. With Y₂O₃ NPs exposure, the Y transport coefficient from the roots to the shoots of rice was 1.94-7.55%. Comparatively, Y³⁺ ions had an insignificant effect on plant growth, with the phytotoxicity of Y being mainly produced by Y₂O₃ NPs.

Dual Effect of Nanomaterials on Germination and Seedling Growth: Stimulation vs. Phytotoxicity

Due to recent active research, a large amount of data has been accumulated regarding the effects of different nanomaterials (mainly metal oxide nanoparticles, carbon nanotubes, chitosan nanoparticles) on different plant species. Most studies have focused on seed germination and early seedling development, presumably due to the simplicity of these experimental systems. Depending mostly on size and concentration, nanomaterials can exert both positive and negative effects on germination and seedling development during normal and stress conditions, thus some research has evaluated the phytotoxic effects of nanomaterials and the physiological and molecular processes behind them, while other works have highlighted the favorable seed priming effects. This review aims to systematize and discuss research data regarding the effect of nanomaterials on germination and seedling growth in order to provide state-of-the-art knowledge about this fast developing research area.

Can the properties of engineered nanoparticles be indicative of their functions and effects in plants?

The extensive applicability of engineered nanoparticles (ENPs) in various fields such as environment, agriculture, medicine or biotechnology has mostly been attributed to their better physicochemical properties as compared with conventional bulk materials. However, functions and biological effects of ENPs change across different scenarios which impede the progress in their risk assessment and safety management. This review thus intends to figure out whether properties of ENPs can be indicators of their behavior through summarizing and analyzing the available literature and knowledge. The studies have indicated that size, shape, solubility, specific surface area, surface charge and surface reactivity constitute a more accurate measure of ENPs functions and toxic effects in addition to mass concentration. Effects of ENPs are also highly dependent on dose metrics, species and strains of organisms, environmental conditions, exposure route and duration. Searching correlations between properties and functions or biological effects may serve as an effective way in understanding positive and negative impacts of ENPs. This will ensure safe design and sustainable future use of ENPs.

Use of polymeric nanoparticles to improve seed germination and plant growth under copper stress

Plant seedlings are susceptible to copper (Cu) toxicity. As copper levels in soil continue to rise with the use of Cu-based agrochemicals, alleviation of Cu stress is of paramount importance. Traditional approaches to allay Cu stress are well documented but are typically found to be either costly or inefficient. Given their small size, ionic character, and high biocompatibility, specific polymeric nanoparticles (NPs) may have the potential for mitigating metal toxicity to crops. In this pioneering study, we investigated the effects of newly synthesized polysuccinimide NPs (PSI-NPs) on corn (Zea mays L.) seed germination and seedling growth under different levels of Cu stress. The results showed that PSI-NPs influenced seed germination in a dose-dependent manner with an optimal rate of 200 mg L^-1. In addition, the positive effects of PSI-NPs on seed germination indexes were found to be positively correlated with enhanced seed imbibition (r = 0.82). The addition of PSI-NPs significantly mitigated Cu stress as indicated by improved growth of shoots and roots, and higher antioxidant enzyme activity observed with co-exposure to PSI-NPs as compared to Cu stress treatment only. Cu concentrations in seedling root and shoot significantly increased with increasing Cu treatment rate. Higher uptake of Cu by plant was observed in the Cu-PSI-NPs co-treatment than single Cu treatment. The alleviation effect of PSI-NPs could be explained by the enhanced antioxidant enzyme activities and storage of Cu as Cu-PSI complexes in plants with reduced phytotoxicity. These findings will open the opportunity of using PSI-NPs as a regulator to enhance seed germination and improve seedling growth under stress of heavy metals like Cu.

Morphological, physiological, and genotoxic effects of heavy metal bioaccumulation in Prosopis laevigata reveal its potential for phytoremediation

Mining industry generates large volumes of waste known as mine tailings, which contain heavy metals (HMs) that generate a risk to environmental health. Thus, remediation of HM pollution requires attention. In this study, HM bioaccumulation, genotoxic damage, and morphological and physiological changes in the tree species Prosopis laevigata were evaluated in order to assess its potential for remediation of mine tailings. P. laevigata plants were established in two treatments (reference substrate and tailing substrate) under greenhouse conditions. Every 2 months, six individuals were selected per treatment for 1 year. From each individual, macromorphological (height, stem diameter, and number of leaves), micromorphological (stomatal coverage and stomatal index), and physiological parameters (chlorophyll content) were evaluated, as well as the concentration of Pb, Cu, Cd, Cr, Fe, and Zn in root and foliar tissue. Genetic damage was assessed by the comet assay in foliar tissue. These parameters were evaluated in adult individuals established in mine tailings. Roots bioaccumulated significantly more HM compared to foliar tissue. However, the bioaccumulation pattern in both tissues was Fe > Pb > Zn > Cu. The plants in tailing substrate reduced significantly the morphological and physiological characters throughout the experiment. Only the bioaccumulation of Pb affected significantly the levels of genetic damage and the number of leaves, while Zn reduced plant height. The percentage of plants that have translocation factor values greater than 1 are Cu (92.9) > Fe (85.7) > Pb (75.0) > Zn (64.3). P. laevigata has potential to phytoremediate environments contaminated with metals, due to its dominance and establishment in abandoned mine tailings, and its ability to bioaccumulate HM unaffecting plant development, as well as their high levels of HM translocation.

Are Titania Photocatalysts and Titanium Implants Safe? Review on the Toxicity of Titanium Compounds

Titanium and its compounds are broadly used in both industrial and domestic products, including jet engines, missiles, prostheses, implants, pigments, cosmetics, food, and photocatalysts for environmental purification and solar energy conversion. Although titanium/titania-containing materials are usually safe for human, animals and environment, increasing concerns on their negative impacts have been postulated. Accordingly, this review covers current knowledge on the toxicity of titania and titanium, in which the behaviour, bioavailability, mechanisms of action, and environmental impacts have been discussed in detail, considering both light and dark conditions. Consequently, the following conclusions have been drawn: (i) titania photocatalysts rarely cause health and environmental problems; (ii) despite the lack of proof, the possible carcinogenicity of titania powders to humans is considered by some authorities; (iii) titanium alloys, commonly applied as implant materials, possess a relatively low health risk; (iv) titania microparticles are less toxic than nanoparticles, independent of the means of exposure; (v) excessive accumulation of titanium in the environment cannot be ignored; (vi) titanium/titania-containing products should be clearly marked with health warning labels, especially for pregnant women and young children; (vi) a key knowledge gap is the lack of comprehensive data about the environmental content and the influence of titania/titanium on biodiversity and the ecological functioning of terrestrial and aquatic ecosystems.

Root System Architecture, Copper Uptake and Tissue Distribution in Soybean (Glycine max (L.) Merr.) Grown in Copper Oxide Nanoparticle (CuONP)-Amended Soil and Implications for Human Nutrition

Understanding the potential uptake and biodistribution of engineered nanoparticles (ENPs) in soil-grown plants is imperative for realistic toxicity and risk assessment considering the oral intake of edibles by humans. Herein, growing N-fixing symbiont (Bradyrhizobium japonicum) inoculated soybean (Glycine max (L.) Merr.) for a full lifecycle of 120 days, we assessed the potential influence of particle size (25, 50, and 250 nm) and concentration (0, 50, 100, 200, and 500 mg/kg soil) of Copper oxide nanoparticles (CuONPs) on: (1) root system architecture, (2) soil physicochemical attributes at the soil-root interface, and (3) Cu transport and accumulation in root, stem, leaf, and seed in soybean, and compared them with the soluble Cu2+ ions and water-only controls. Finally, we performed a comparative assessment of total seed Cu levels in soybean with other valuable food sources for Cu intake and discussed potential human health implications. Results showed particle size- and concentration-dependent influence of CuONPs on Cu uptake and distribution in root, stem, leaf, and seed. Alterations in root architecture (root biomass, length, volume, and area) were dependent on the Cu compound types, Cu concentrations, and their interactions. Concentration-response relationships for all three sizes of CuONPs and Cu2+ ions were found to be linear. Furthermore, CuONPs and Cu2+ ions had inhibitory effects on root growth and development. Overall, soybean responses to the smallest size of CuONPs-25 nm-were greater for all parameters tested compared to the two larger-sized CuONPs (50 nm, 250 nm) or Cu2+ ions. Results suggest that minor changes in soil-root physicochemical attributes may not be a major driver for Cu uptake in soybean. Cu bioaccumulation followed the order: root > leaf > stem > seed. Despite reduction in root architecture and seed yield, the smallest size CuONPs-25 nm led to increased total seed Cu uptake compared to the larger-sized CuONPs or Cu2+ ions. Our findings also suggest that soil amendment with CuONPs, and more so with the smallest size of CuONPs-25 nm-could significantly improve seed nutritional Cu value in soybean as reflected by the % Daily Values (DV) and are rated "Good" to "Very Good" according to the "World's Healthiest Foods" rating. However, until the potential toxicity and risk from CuONP-fortified soybean seed ingestion is characterized in humans, we caution recommending such seeds for daily human consumption when addressing food Cu-deficiency and associated diseases, globally.

Binary mixture of nanoparticles in sewage sludge: Impact on spinach growth

Present study carried out pot experiments and evaluated effects of single and binary mixture of nanoparticles (exposed via sludge as soil conditioner) on spinach plant. Exposure of Ag₂O nanoparticles (NPs) (1 and 10 mg/kg soil-sludge) did not show significant reduction in plant as compared to control. On the other hand, TiO₂ NPs (exposed as single and in binary mixture) resulted in significant increase in root length (29% and 37%) and fresh weight (60% and 48%) at highest exposure concentration. Total chlorophyll content decreased for Ag₂O and binary mixture (7% and 4%, respectively) and increased for TiO₂ (5%) at 10 mg/kg soil-sludge. The toxic interaction between Ag₂O and TiO₂ NPs was additive at both exposure concentrations. Ag₂O NPs had higher tendency of root surface adsorption than TiO₂ NPs. Metal content in spinach leaves at highest exposure concentration was Ag: 2.6 ± 0.55 mg/g plant biomass(for Ag₂O NPs) and 1.02 ± 0.32 mg/g plant biomass (for Ag₂O + TiO₂ NPs) and for Ti: 1.12 ± 0.78 (for TiO₂ NPs) mg/g plant biomass and 0.58 ± 0.41 mg/g (for Ag₂O + TiO₂ NPs). The inadvertent ingestion of NPs- contaminated spinach resulted in projected daily intake (DI) of Ag and Ti for different age-mass classes (child to adult) exceeding the oral reference dose for toxicity during oral ingestion. In conclusion, we report no acute toxicity of single and binary mixture of NPs to spinach but significant accumulation of Ag and Ti metals in spinach leaves. There are high chances that ingestion of spinach grown in such environment might lead to human health risks.

Impact of copper oxide nanoparticles on the germination, seedling growth, and physiological responses in Brassica pekinensis L

Wide application of nanoparticles causes considerable environmental, health, and safety problems. However, their potential impact and mechanisms on plant growth are not completely clear. In the present study, the effects of different concentration of copper oxide nanoparticles (nCuO) on seed germination and seedling growth, as well as physiological parameters of Brassica pekinensis L., were investigated. The seeds were exposed to 10-, 100-, and 1000-mg L-1 nCuO suspensions and 0.8-mg L-1 Cu2+ released from 1000-mg L-1 nCuO for 7 day. The results showed that nCuO did not affect the germination rate, germination potential, and germination index of B. pekinensis but significantly affected the vitality index. The growth of roots and shoots of B. pekinensis was promoted at 10-mg L-1 nCuO, while they were inhibited under 1000-mg L-1 nCuO and Cu2+ ion treatments, and roots suffered more damage than shoots. Cu content in shoots and roots of B. pekinensis increased with increasing concentrations of nCuO, which is significantly higher in roots as compared with shoots. Roots and shoots accumulated more Cu under nCuO treatments compared with Cu2+ ion treatment. nCuO treatments led to significant lignification in roots of B. pekinensis. Furthermore, nCuO increased in the contents of soluble sugar and protein in shoots, while nCuO at 1000 mg L-1 significantly inhibited the content of soluble protein in roots. In addition, concentration-dependent augmentation of lipid peroxidation, hydrogen peroxide and superoxide generation, and antioxidant enzyme activity were noticed in shoots and roots of B. pekinensis seedlings under nCuO and Cu2+ ion treatments. Altogether, the results strongly suggested that the phytotoxicity of nCuO in B. pekinensis was caused by both the nanoparticles itself and the released Cu2+ ions.