Foliar Exposure of Cu(OH)2 Nanopesticide to Basil ( Ocimum basilicum): Variety-Dependent Copper Translocation and Biochemical Responses

Temporal Dynamics of Copper-Based Nanopesticide Transfer and Subsequent Modulation of the Interplay Between Host and Microbiota Across Trophic Levels

During agricultural production, significant quantities of copper-based nanopesticides (CBNPs) may be released into terrestrial ecosystems through foliar spraying, thereby posing a potential risk of biological transmission via food chains. Consequently, we investigated the trophic transfer of two commonly available commercial CBNPs, Reap2000 (RP) and HolyCu (HC), in a plant-caterpillar terrestrial food chain and evaluated impacts on host microbiota. Upon foliar exposure (with 4 rounds of spraying, totaling 6.0 mg CBNPs per plant), leaf Cu accumulation levels were 726 ± 180 and 571 ± 121 mg kg-1 for RP and HC, respectively. HC exhibited less penetration through the cuticle compared to RP (RP: 55.5%; HC: 32.8%), possibly due to size exclusion limitations. While caterpillars accumulated higher amounts of RP, HC exhibited a slightly higher trophic transfer factor (TTF; RP: 0.69 ± 0.20; HC: 0.74 ± 0.17, p > 0.05) and was more likely to be transferred through the food chain. The application of RP promoted the dispersal of phyllosphere microbes and perturbed the original host intestinal microbiota, whereas the HC group was largely host-modulated (control: 65%; RP: 94%; HC: 34%). Integrating multiomics analyses and modeling approaches, we elucidated two pathways by which plants exert bottom-up control over caterpillar health. Beyond the direct transmission of phyllosphere microbes, the leaf microbiome recruited upon exposure to CBNPs further influenced the ingestion behavior and intestinal microbiota of caterpillars via altered leaf metabolites. Elevated Proteobacteria abundance benefited caterpillar growth with RP, while the reduction of Proteobacteria with HC increased the risk of lipid metabolism issues and gut disease. The recruited Bacteroidota in the RP phyllosphere proliferated more extensively into the caterpillar gut to enhance stress resistance. Overall, the gut microbes reshaped in RP caterpillars exerted a strong regulatory effect on host health. These findings expand our understanding of the dynamic transmission of host-microbiota interactions with foliar CBNPs exposure, and provide critical insight necessary to ensure the safety and sustainability of nanoenabled agricultural strategies.

CuO nanoparticles' effect on the photosynthetic performance in seed tissues of Inga laurina (Fabaceae)

Copper oxide nanoparticles (CuONPs) have been produced on a large scale because they can be applied across various fields, especially in nano-enabled healthcare and agricultural products. However, the increasing use of CuONPs leads to their release and accumulation into the environment. The CuONPs uptaken by seeds and their implications on germination behavior have been reported, but little is known or understood about their impact on photosynthesis in seed tissues. To fill knowledge gaps, this study evaluated the effects of CuONP concentrations (0-300 mg L-1) on the photosynthetic activity of Inga laurina seeds. The microscopy data showed that CuONPs had an average size distribution of 57.5 ± 0.7 nm. Copper ion release and production of reactive oxygen species (ROS) by CuONPs were also evaluated by dialysis and spectroscopy experiments, respectively. CuONPs were not able to intrinsically generate ROS and released a low content of Cu2⁺ ions (4.5%, w/w). Time evolution of chlorophyll fluorescence imaging and laser-induced fluorescence spectroscopy were used to monitor the seeds subjected to nanoparticles during 168 h. The data demonstrate that CuONPs affected the steady-state maximum chlorophyll fluorescence (F m ' ), the photochemical efficiency of photosystem II (F v / F m ), and non-photochemical quenching ( NPQ ) of Inga laurina seeds over time. Besides, the NPQ significantly increased at the seed development stage, near the root protrusion stage, probably due to energy dissipation at this germination step. Additionally, the results indicated that CuONPs can change the oscillatory rhythms of energy dissipation of the seeds, disturbing the circadian clock. In conclusion, the results indicate that CuONPs can affect the photosynthetic behavior of I. laurina seeds. These findings open opportunities for using chlorophyll fluorescence as a non-destructive tool to evaluate nanoparticle impact on photosynthetic activity in seed tissues.

Recent advances on environmental behavior of Cu-based nanomaterials in soil-plant system: A review

In recent years, copper-based nanomaterials (Cu-based NMs) have shown great potential in promoting agriculture development due to their special physicochemical characteristics. With the mass production and overuse of Cu-based NMs, there are potential effects on the soil-plant environment. Soil organisms, especially soil microorganisms, play a significant part in terrestrial or soil ecosystems; plants, as indirect organisms with soil-related Cu-based NMs, may affect human health through plant agricultural products. Understanding the accumulation and transformation of Cu-based NMs in soil-plant systems, as well as their ecotoxicological effects and potential mechanisms, is a prerequisite for the scientific assessment of environmental risks and safe application. Therefore, based on the current literature, this review: (i) introduces the accumulation and transformation behaviors of Cu-based NMs in soil and plant systems; (ii) focuses on the ecotoxicological effects of Cu-based NMs on a variety of organisms (microorganisms, invertebrates, and plants); (iii) reveals their corresponding toxicity mechanisms. It appears from studies hitherto made that both Cu-based NMs and released Cu2+ may be the main reasons for toxicity. When Cu-based NMs enter the soil-plant environment, their intrinsic physicochemical properties, along with various environmental factors, could also affect their transport, transformation, and biotoxicity. Therefore, we should push for intensifying the multi-approach research that focuses on the behaviors of Cu-based NMs in terrestrial exposure environments, and mitigates their toxicity to ensure the promotion of Cu-based NMs.

Analysis of multiple biomarkers revealed the size matters of Cu particles for barley response under foliar exposure

The impact of particle size of engineered nanoparticles (ENPs) on plant response has marginally been investigated under the foliar application so far. Concerning the significance of particle diameter for their properties and interaction with plants, the effect of size should be considered in the analysis of the effect of micronutrient-based ENPs on plants. It is of particular importance for ENPs containing Cu due to plants needing a relatively low amount of this element, thus there is a risk of overdosing during application as a fertilizer or pesticide. Here, we examined the biochemical and transcriptional response of barley (Hordeum vulgare L.) to Cu nanoparticles (nano-Cu) with different diameters (25 nm, 50 nm, 70 nm), microparticles (micro-Cu), and chelated Cu (EDTA-Cu). The plants suffering from Cu deficiency were foliar sprayed with Cu compounds at 1000 mg/L during the tillering stage. 1- and 7-day plants were analyzed in terms of biomass, Cu content, the activity of enzymes involved with antioxidant response, the content of low molecular weight compounds, and the expression of genes regulated metal homeostasis, aquaporins, and defense. The results showed that the Cu leaf level was differentiated over time and after 7 days it was higher under exposure to the smallest nano-Cu than other particulate Cu. Regardless of the duration of exposure, the Cu content was highest in plants treated with Cu-EDTA. The cluster analysis of all markers revealed a clear distinct response to the smallest nano-Cu and other particulate and ionic treatments. The bigger nano-Cu, depending on the markers, caused the medium effects between the nano-Cu 25 nm and micro-Cu and Cu-EDTA. The found size thresholds at the nanoscale will be useful for the fabrication of safe-by-design agrochemicals to provide crop security and attenuate environmental impact.

Transcriptional response of Cu-deficient barley (Hordeum vulgare L.) to foliar-applied nano-Cu: Molecular crosstalk between Cu loading into plants and changes in Cu homeostasis genes

For safe and effective nutrient management, the cutting-edge approaches to plant fertilization are continuously developed. The aim of the study was to analyze the transcriptional response of barley suffering from Cu deficiency to foliar application of nanoparticulate Cu (nano-Cu) and its ionic form (CuSO4) at 100 and 1000 mg L-1 for the examination of their supplementing effect. The initial interactions of Cu-compounds with barley leaves were analyzed with spectroscopic (ICP-OES) and microscopic (SEM-EDS) methods. To determine Cu cellular status, the impact of Cu-compounds on the expression of genes involved in regulating Cu homeostasis (PAA1, PAA2, RAN1, COPT5), aquaporins (NIP2.1, PIP1.1, TIP1.1, TIP1.2) and antioxidant defense response (SOD CuZn, SOD Fe, SOD Mn, CAT) after 1 and 7 days of exposure was analyzed. Although Cu accumulation in plant leaves was detected overtime, the Cu content in leaves exposed to nano-Cu for 7 days was 44.5% lower than in CuSO4 at 100 mg L-1. However, nano-Cu aggregates remaining on the leaf surface indicated a potential difference between measured Cu content and the real Cu pool present in the plant. Our study revealed significant changes in the pattern of gene expression overtime depending on Cu-compound type and dose. Despite the initial puzzling patterns of gene expression, after 7 days all Cu transporters showed significant down-regulation under Cu-compounds exposure to prevent Cu excess in plant cells. Conversely, aquaporin gene expression was induced after 7 days, especially by nano-Cu and CuSO4 at 100 mg L-1 due to the stimulatory effect of low Cu doses. Our study revealed that the gradual release of Cu ions from nano-Cu at a lower rate provided a milder molecular response than CuSO4. It might indicate that nano-Cu maintained better metal balance in plants than the conventional compounds, thus may be considered as a long-term supplier of Cu.

Unveiling of interactions between foliar-applied Cu nanoparticles and barley suffering from Cu deficiency

The objective of this study was to evaluate nano-Cu-plant interactions under Cu deficiency. Nano-Cu at rates of 100 and 1000 mg L^-1 was applied as foliar spray to Hordeum vulgare L. during increased demand for nutrients at tillering stage. Corresponding treatment with CuSO₄ was used to exam the nano-specific effects. Cu compounds-plant leaves interactions were analyzed with spectroscopic and microscopic methods (ICP-OES, FTIR/ATR, SEM-EDS). Moreover, the effect of Cu compounds on plants in terms of biomass, pigments content, lipid peroxidation, antiradical properties, the activity of enzymes involved in plant defense against stress (SOD, CAT, POD, GR, PAL, PPO) and the content of non-enzymatic antioxidants (GSH, GSSG, TPC) was determined after 1 and 7 days of exposure. Cu loading to plant leaves increased over time, but the content of Cu under treatment with nano-Cu at 100 mg L^-1 was lower by 76% than CuSO₄ at 7th day of exposure. The changes induced by applied Cu compounds in biochemical traits were mostly observed after 1 day. Our data showed that CuSO₄ exposure induce oxidative stress (increased MDA level and GSSG content) when compared to control and nano-Cu treated plants. Noteworthy, nano Cu at 100 mg L^-1 demonstrated enhanced stress tolerance as indicated by boosted GSH content. After 7 days, the antioxidant response was almost same compared to control sample. However, based on other indicators (pigment content, chlorosis sign, biomass), it should be noted that CuSO₄ caused serve oxidative burst of plant which may resulted in damage of defense system. Nano-Cu, especially at 100 mg L^-1, showed promising effect on plant health, and obtained results may be useful for optimizing of nano-Cu application as fertilizer agent.

The life cycle study revealed distinct impact of foliar-applied nano-Cu on antioxidant traits of barley grain comparing with conventional agents

Despite that the applicability of Cu-based engineered nanoparticles (ENPs) as an antibacterial and antifungal agent for plant protection has been studied widely, little is known about their role in the improvement of crop yield and quality. Here, a full life study was performed to investigate the nutritional quality and bioactivity of barley grains under foliar application of nano-/microparticulate (nano-Cu, nano-CuO, micro-Cu) and ionic Cu compounds (CuSO₄, CuEDTA). Hordeum vulgaris L. plants were sprayed with Cu compounds at 500 mg/L during the end of tillering and the beginning of heading. Yield, mineral composition, protein and dietary content, antioxidant (phenolic, anthocyanin, flavonoid, tannin, flavanol) content and antioxidant capacity of barley grain were evaluated. Grain yield was unaffected by all treatments. Only nano-Cu and ionic compounds enhanced Cu accumulation in grain: 2-fold increase was observed compared to the control (2.6 µg/kg). Nano-Cu also increased the dietary fiber content by 19.9 %, while no impact of the other treatments was determined. The content of phenolic compounds, the main group of antioxidants, remained unchanged after Cu supply. In general, for all Cu treatment, antiradical and reducing abilities were decreased or were at the similar level in relation to the control. On the other hand, chelating power in grain extracts was 2-4 times higher under nano-Cu/nano-CuO/micro-Cu than in the untreated sample, while the ionic compounds had no impact on the chelating indicator. Our results demonstrated that more favorable effects were triggered by nano-Cu than CuSO₄ or CuEDTA on the tested indicators of barley grain, despite that both compounds resulted in similar superior Cu acquisition. It suggests that nano-Cu may be considered as an alternative agent to be used as economic and traditional fertilizers.

Polystyrene microplastics protect lettuce (Lactuca sativa) from the hazardous effects of Cu(OH)2 nanopesticides

Copper-based nanopesticides are released into the environment during foliar spray application, and they could, on their own or in combination with microplastics (MPs), pose threats to environmental safety and human health. In this study, Cu(OH)₂ nanowires greatly decreased the vigor of lettuce seeds (p< 0.01) and the root length of lettuce seedlings (p< 0.01) and significantly altered the lettuce antioxidant defence system and MDA content (p< 0.05). Released Cu²⁺ played a critical role in the toxicity mechanism of Cu(OH)₂ nanowires in lettuce seedlings, as evidenced by the substantial accumulation of Cu in the seedling roots (p< 0.01) rather than in the leaves. Polystyrene (PS) MPs (1 mg/L) stimulated lettuce seedling growth, as shown by the (highly) significant increase in root and leaf length and in the seed vigor index (p< 0.01 or 0.05). Notably, PS MPs (1 mg/L) neutralized the hazardous effects of 1 mg/L Cu(OH)₂ nanowire treatment on lettuce growth, as reflected by the vitality and root length of the seedlings returning to normal levels. The PS MPs (1 mg/L) absorbed on middle root surfaces and strongly hindered Cu accumulation in lettuce roots, which was the predominant mechanism by which PS MPs suppressed the hazardous effects of the Cu(OH)₂ nanowires. This study strengthens the understanding of the toxicity and toxicity mechanisms of Cu(OH)₂ nanowires with or without PS MPs in the environment.

Effect of ZnO and CuO nanoparticles on the growth, nutrient absorption, and potential health risk of the seasonal vegetable Medicago polymorpha L

Background

Medicago polymorpha L., a seasonal vegetable, is commonly grown in China. The increasing use of nanoparticles (NPs) such as ZnO and CuO NPs in agriculture has raised concerns about their potential risks for plant growth and for human consumption. There is a lack of research on the effects of ZnO and CuO NPs on agronomic performance of Medicago polymorpha L. and their potential risks for human health.

Methods

In this study, different treatment concentrations of ZnO NPs (25, 50, 100, and 200 mg kg^-1) and CuO NPs (10, 25, 50, and 100 mg kg^-1) were used to determine their effects on the growth and nutrient absorption of Medicago polymorpha L., as well as their potential risk for human health.

Results

The results showed that ZnO and CuO NPs increased the fresh weight of Medicago polymorpha L. by 5.8-11.8 and 3.7-8.1%, respectively. The best performance for ZnO NPs occurred between 25-50 mg kg^-1 and the best performance for CuO NPs occurred between 10-25 mg kg^-1. Compared with the control, ZnO and CuO NPs improved the macronutrients phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca). The following micronutrients were also improved: iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), and manganese (Mn), with the exception of nitrogen (N) accumulation. Low treatment concentrations exhibited more efficient nutrient uptake than high treatment concentrations. A comprehensive analysis showed that the optimum concentrations were 25 mg kg^-1 for ZnO NPs and 10 mg kg^-1 for CuO NPs. The potential non-carcinogenic health risk of Medicago polymorpha L. treated with ZnO and CuO NPs was analyzed according to the estimated daily intake (EDI), the hazard quotient (HQ), and the cumulative hazard quotient (CHQ). Compared with the oral reference dose, the EDI under different ZnO and CuO NPs treatments was lower. The HQ and CHQ under different ZnO and CuO NPs treatments were far below 1. This indicated that Medicago polymorpha L. treated with ZnO and CuO NPs did not pose any non-carcinogenic health risk to the human body. Therefore, ZnO and CuO NPs were considered as a safe nano fertilizer for Medicago polymorpha L. production according to growth analysis and a human health risk assessment.

Estimation of health risks due to copper-based nanoagrochemicals

This study estimated health risks due to two types of copper-based nanoagrochemicals (Cu (OH)₂ and CuO nanoparticles (NPs)), during inadvertent ingestion of soil and consumption of leafy vegetables for a hypothetical exposure scenario. The dissolution of copper-based nanoagrochemicals in human digestive system was considered for estimating realistic doses. No risk was found during soil ingestion (hazard quotient (HQ) <1). HQ (no dissolution of Cu (OH) ₂ nanopesticides) (HQ= 0.015) comes out to be 2 times higher than that of HQ (100% dissolution of Cu (OH)₂ nanopesticides into copper ions) (HQ= 0.007). In case of risk from consumption of leafy vegetables, the following order of risk was found (high to low HQ value): Cu (OH)₂ (HQ= 1925) >CuO NPs (1402). Combined exposure of Cu (OH)₂ nanopesticide through soil ingestion as well as consumption of contaminated edible leafy vegetables resulted in health risks. The calculated maximum allowable applicable concentration values of Cu (OH)₂ and CuO NPs without posing risk to human and plant toxicity were found to be 1.14 and 0.45 mg/L, respectively. These findings can be used now for deciding safe use of copper-based nanoagrochemicals.

Soil and foliar exposure of soybean (Glycine max) to Cu: Nanoparticle coating-dependent plant responses

In this study, we investigated the effects of citric acid (CA) coated copper oxide nanoparticles (CuO NPs) and their application method (foliar or soil exposure) on the growth and physiology of soybean (Glycine max). After nanomaterials exposure via foliar or soil application, Cu concentration was elevated in the roots, leaves, stem, pod, and seeds; distribution varied by plant organ and surface coating. Foliar application of CuO NPs at 300 mg/L and CuO-CA NPs at 75 mg/L increased soybean yield by 169.5% and 170.1%, respectively. In contrast, foliar and soil exposure to ionic Cu with all treatments (75 and 300 mg/L) had no impact on yield. Additionally, CuO-CA NPs at 300 mg/L significantly decreased Cu concentration in seeds by 46.7%, compared to control, and by 44.7%, compared to equivalent concentration of CuO NPs. Based on the total Cu concentration, CuO NPs appeared to be more accessible for plant uptake, compared to CuO-CA NPs, inducing a decrease in protein content by 56.3% and inhibiting plant height by 27.9% at 300 mg/kg under soil exposure. The translocation of Cu from leaf to root and from the root to leaf through the xylem was imaged by two-photon microscopy. The findings indicate that citric acid coating reduced CuO NPs toxicity in soybean, demonstrating that surface modification may change the toxic properties of NPs. This research provides direct evidence for the positive effects of CuO-CA NPs on soybean, including accumulation and in planta transfer of the particles, and provides important information when assessing the risk and the benefits of NP use in food safety and security.

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.

Nano-enabled agrochemicals/materials: Potential human health impact, risk assessment, management strategies and future prospects

Nanotechnology is a rapidly developing technology that will have a significant impact on product development in the next few years. The technology is already being employed in cutting-edge cosmetic and healthcare products. Nanotechnology and nanoparticles have a strong potential for product and process innovation in the food industrial sector. This is already being demonstrated by food product availability made using nanotechnology. Nanotechnologies will have an impact on food security, packaging materials, delivery systems, bioavailability, and new disease detection materials in the food production chain, contributing to the UN Millennium Development Goals targets. Food products using nanoparticles are already gaining traction into the market, with an emphasis on online sales. This means that pre- and post-marketing regulatory frameworks and risk assessments must meet certain standards. There are potential advantages of nanotechnologies for agriculture, consumers and the food industry at large as they are with other new and growing technologies. However, little is understood about the safety implications of applying nanotechnologies to agriculture and incorporating nanoparticles into food. As a result, policymakers and scientists must move quickly, as regulatory systems appear to require change, and scientists should contribute to these adaptations. Their combined efforts should make it easier to reduce health and environmental impacts while also promoting the economic growth of nanotechnologies in the food supply chain. This review highlighted the benefits of a number of nano enabled agrochemicals/materials, the potential health impacts as well as the risk assessment and risk management for nanoparticles in the agriculture and food production chain.

Metabolomic Response of Early-Stage Wheat (Triticum aestivum) to Surfactant-Aided Foliar Application of Copper Hydroxide and Molybdenum Trioxide Nanoparticles

Surfactants are commonly used in foliar applications to enhance interactions of active ingredients with plant leaves. We employed metabolomics to understand the effects of TritonTM X-100 surfactant (SA) and nanomaterials (NMs) on wheat (Triticum aestivum) at the molecular level. Leaves of three-week-old wheat seedlings were exposed to deionized water (DI), surfactant solution (SA), NMs-surfactant suspensions (Cu(OH)2 NMs and MoO3 NMs), and ionic-surfactant solutions (Cu IONs and Mo IONs). Wheat leaves and roots were evaluated via physiological, nutrient distribution, and targeted metabolomics analyses. SA had no impact on plant physiological parameters, however, 30+ dysregulated metabolites and 15+ perturbed metabolomic pathways were identified in wheat leaves and roots. Cu(OH)2 NMs resulted in an accumulation of 649.8 μg/g Cu in leaves; even with minimal Cu translocation, levels of 27 metabolites were significantly changed in roots. Due to the low dissolution of Cu(OH)2 NMs in SA, the low concentration of Cu IONs induced minimal plant response. In contrast, given the substantial dissolution of MoO3 NMs (35.8%), the corresponding high levels of Mo IONs resulted in significant metabolite reprogramming (30+ metabolites dysregulated). Aspartic acid, proline, chlorogenic acid, adenosine, ascorbic acid, phenylalanine, and lysine were significantly upregulated for MoO3 NMs, yet downregulated under Mo IONs condition. Surprisingly, Cu(OH)2 NMs stimulated wheat plant tissues more than MoO3 NMs. The glyoxylate/dicarboxylate metabolism (in leaves) and valine/leucine/isoleucine biosynthesis (in roots) uniquely responded to Cu(OH)2 NMs. Findings from this study provide novel insights on the use of surfactants to enhance the foliar application of nanoagrochemicals.

Critical Review: Role of Inorganic Nanoparticle Properties on Their Foliar Uptake and in Planta Translocation

There is increasing pressure on global agricultural systems due to higher food demand, climate change, and environmental concerns. The design of nanostructures is proposed as one of the economically viable technological solutions that can make agrochemical use (fertilizers and pesticides) more efficient through reduced runoff, increased foliar uptake and bioavailability, and decreased environmental impacts. However, gaps in knowledge about the transport of nanoparticles across the leaf surface and their behavior in planta limit the rational design of nanoparticles for foliar delivery with controlled fate and limited risk. Here, the current literature on nano-objects deposited on leaves is reviewed. The different possible foliar routes of uptake (stomata, cuticle, trichomes, hydathodes, necrotic spots) are discussed, along with the paths of translocation, via the phloem, from the leaf to the end sinks (mature and developing tissues, roots, rhizosphere). This review details the interplays between morphological constraints, environmental stimuli, and physical-chemical properties of nanoparticles influencing their fate, transformation, and transport after foliar deposition. A metadata analysis from the existing literature highlighted that plant used for testing nanoparticle fate are most often dicotyledon plants (75%), while monocotyledons (as cereals) are less considered. Correlations on parameters calculated from the literature indicated that nanoparticle dose, size, zeta potential, and affinity to organic phases correlated with leaf-to-sink translocation, demonstrating that targeting nanoparticles to specific plant compartments by design should be achievable. Correlations also showed that time and plant growth seemed to be drivers for in planta mobility, parameters that are largely overlooked in the literature. This review thus highlights the material design opportunities and the knowledge gaps for targeted, stimuli driven deliveries of safe nanomaterials for agriculture.

Drilling into the Metabolomics to Enhance Insight on Corn and Wheat Responses to Molybdenum Trioxide Nanoparticles

Metabolomics is an emerging tool to understand the potential implications of nanotechnology, particularly for agriculture. Although molybdenum (Mo) is a known plant micronutrient, little is known of its metabolic perturbations. Here, corn and wheat seedlings were exposed to MoO₃ nanoparticles (NPs) and the corresponding bioavailable Mo⁶⁺ ion at moderate and excessive levels through root exposures. Physiologically, corn was more sensitive to Mo, which accumulated up to 3.63 times more Mo than wheat. In contrast, metabolomics indicated 21 dysregulated metabolites in corn leaves and 53 in wheat leaves. Five more metabolomic pathways were perturbed in wheat leaves compared to corn leaves. In addition to the overall metabolomics analysis, we also analyzed individual metabolite classes (e.g., amino acids, organic acids, etc.), yielding additional dysregulated metabolites in plant tissues: 7 for corn and 7 for wheat. Most of these were amino acids as well as some sugars. Additional significantly dysregulated metabolites (e.g., asparagine, fructose, reduced glutathione, mannose) were identified in both corn and wheat, due to Mo NP exposure, by employing individual metabolite group analysis. Targeted metabolite analysis of individual groups is thus important for finding additional significant metabolites. We demonstrate the value of metabolomics to study early stage plant responses to NP exposure.

Soil-aged nano titanium dioxide effects on full-grown carrot: Dose and surface-coating dependent improvements on growth and nutrient quality

Rutile titanium dioxide nanoparticles (nTiO₂) were weathered in field soil at 0, 100, 200, and 400 mg Ti/kg soil for four months. Two types of nTiO₂ with different surface coatings (hydrophilic and hydrophobic), uncoated nTiO₂ (pristine), and the untreated control were included. Thereafter, carrot seeds (Daucus carota L.) were sown in those soils and grown in a growth chamber for 115 days until full maturity. A comparison was made between this and our previous unaged study, where carrots were treated in the same way in soil with freshly amended nTiO₂. The responses of plants depended on the nTiO₂ surface coating and concentration. The aged hydrophobic and hydrophilic-coated nTiO₂ induced more positive effects on plant development at 400 and 100 mg Ti/kg soil, respectively, compared with control and pristine treatments. Taproot and leaf fresh biomass and plant height were improved by up to 64%, 40%, and 40% compared with control, respectively. Meanwhile, nutrient elements such as Fe in leaves, Mg in taproots, and Ca, Zn, and K in roots were enhanced by up to 66%, 64%, 41, 143% and 46%, respectively. However, the contents of sugar, starch, and some other metal elements in taproots were negatively affected, which may compromise their nutritional quality. Taken together, the overall growth of carrots was benefited by the aged nTiO₂ depending on coating and concentration. The aging process served as a potential sustainable strategy to alleviate the phytotoxicity of unweathered nanoparticles.

Ecotoxicological and regulatory aspects of environmental sustainability of nanopesticides

Recent years have seen the development of various colloidal formulations of pesticides and other agrochemicals aimed at use in sustainable agriculture. These formulations include inorganic, organic or hybrid particulates, or nanocarriers composed of biodegradable polymers, that can provide a better control of the release of active ingredients. The very small particle sizes and high surface areas of nanopesticides may however also lead to some unintended (eco)toxicological effects due to the way in which they interact with the target and non-target species and the environment. The current level of knowledge on ecotoxicological effects of nanopesticides is scarce, especially in regard to the fate and behaviour of such formulations in the environment. Nanopesticides will however have to cross a stringent regulatory scrutiny before marketing in most countries for health and environmental risks under a range of regulatory frameworks that require pre-market notification, risk assessment and approval, followed by labelling, post-market monitoring and surveillance. This review provides an overview of the key regulatory and ecotoxicological aspects relating to nanopesticides that will need to be considered for environmentally-sustainable use in agriculture.

Effects of nano-enabled agricultural strategies on food quality: Current knowledge and future research needs

It is becoming more feasible to use nano-enabled agricultural products such as nanofertilizers and nanopesticides to improve the efficiency of agrochemical delivery to crop plants. Experimental results have shown that nano-agrochemicals have great potential for reducing the environmental impact of traditional agrochemicals while simultaneously significantly increasing crop production. However, emerging data suggest that nano-enabled products are not only capable of increasing yield, but also result in alterations in crop quality. Variation in proteins, sugars, starch content, as well as in metallic essential elements have been reported. Verbi gratia, albumin, globulin, and prolamin have been significantly increased in rice exposed to CeO₂ engineered nanoparticles (ENPs), while CeO₂, CuO, and ZnO ENPs have increased Ca, Mg, and P in several crops. Conversely, reductions in Mo and Ni have been reported in cucumber and kidney beans exposed to CeO₂ and ZnO engineered nanomaterials, respectively. However, reports on specific effects in human health due to the consumption of agricultural products obtained from plants exposed to nano-agrochemicals are still missing.

Harnessing the Potential of Roots of Traditional Power Plant: Ocimum

Genus Ocimum of Labiatae is well known in all traditional medicinal systems like Ayurveda, Unani, Siddha, and Homeopathy. The pharmaceutical activities of different species of Ocimum attributed to all plant parts. Roots are the most significant vital organ of the plant, as they absorb water and nutrients from soil and transport to aerial parts of the plants. Roots of Ocimum were found helpful with free-radical scavenging activity to improve physical and mental strength as well as to treat diabetes, malaria, and liver problems. Antibacterial activity of Ocimum roots and its main component, rosmarinic acid, is very beneficial to protect against several human pathogens, including bacteria and viruses. Being so important in every way, roots of Ocimum need healthy rhizosphere. Bacteria, fungi, nematodes, types of soil, fungicide, pesticides, salt, radioactive elements, as well as heavy metal contaminations, affect roots and overall growth of Ocimum in positive or negative ways. Each component of rhizosphere (natural, treatment or contamination) affects the roots, which highlights current ecological scenario to discover biosafe and more productive approaches. For such prestigious organ of Ocimum, development of in vitro root cultures and hairy root cultures assists to reduce the efforts and timing of the traditional cultivation process along with elimination of negative factors in rhizosphere. Different strains of Agrobacterium rhizogenes, various media compositions, as well as discrete treatments, like elicitors, on nonidentical species or cultivars of Ocimum boost the root induction, biomass, and accumulation of phytoceuticals differently. Hairy roots and in vitro roots of Ocimum accumulate higher quantity of therapeutic metabolites. These metabolites include several phenolics (like rosmarinic acid, 3-hydroxybenzoic acid, m-coumaric acid, p-coumaric acid, caffeic acid, ferulic acid, vanillic acid, chicoric acid, and lithospermic acid), triterpenes (such as betulinic acid, 3-epimaslinic acid, alphitolic acid, euscaphic acids, oleanolic acid, and ursolic acid) as well as flavonoids (flavones, flavonols, and dihydroflavonols). This review highlights pharmaceutical applications of Ocimum roots, a great deal of rhizosphere components and in vitro culturing techniques to enhance biomass as well as chief phytoceuticals.

Antioxidant and defense genetic expressions in corn at early-developmental stage are differentially modulated by copper form exposure (nano, bulk, ionic): Nutrient and physiological effects

In the present study, Zea mays seedlings grown under nano Cu(OH)₂ (nCu), bulk Cu(OH)₂ (bCu), and ionic CuSO₄ (iCu) compound exposure were harvested after six days. The nutritional profile was determined to be significantly disrupted in the roots by 1000 ppm bCu treatment, resulting in a 58.7% reduction in potassium compared to the control. In the shoots, a significant decrease of manganese was observed for 10 and 1000 ppm iCu treatments with 55.7% and 64.2% reductions, respectively. The overall protein content and catalase (CAT) enzymatic activity, however, remained unaffected in either roots or shoots, while an absence of polyphenol oxidase (PPO) activity was observed for all samples. The genetic expression of defense-related genes, metallothionein (MT), CAT, ascorbate peroxidase (APX), and PPO was assessed. The genetic expression of MT was upregulated 50-fold in roots treated with 1000 ppm bCu. There were no significant differences in CAT transcripts among the various treatments, while APX was upregulated 28 and 19-fold in shoots treated with 10 ppm bCu and 10 ppm nCu, respectively. Meanwhile, APX mRNA levels were downregulated five-fold in shoots treated with 1000 ppm iCu. Thus, indicating that the role of APX in plant defense was reinforced in seedlings exposed to low concentration of particulate Cu compounds. Remarkably, no PPO expression was found in any of the treatments and controls, which suggests this enzyme is expressed only under specific external factors or seedlings have an "immature" cascade signaling activation of the PPO system. Taken together, these results show that bCu and nCu treatments at a low concentration do not compromise vital cell machinery but rather elicit the enhancement of defense responses as observed through the increase in APX expression. Furthermore, under optimal concentrations, these Cu treatments show promise in enhancing corn defense responses, which can ultimately lead to increases in future global crop yields.

Developmental toxicity induced by Cu(OH)2 nanopesticide in zebrafish embryos

The current study evaluates the adverse effects of Cu(OH)₂ nanopesticide (CNPE) on the early life stages of zebrafish (Danio rerio). The developmental toxicity was determined using different parameters such as mortality (including LC₅₀ ), hatching, heart rates, malformations, and alteration of the gene expressions. Zebrafish embryos (4 hpf-hours postfertilization) were exposed to 1.0, 2.0, 4.0, 8.0, and 16.0 mg/l CNPE doses until 96 hpf. The 96 hours LC₅₀ was recorded at 6.258 mg/l. Seventy-two hpf total malformation index values for 2.0, 4.0, and 8.0 mg/l CNPE doses were 4.3, 7.2 and 7.9, respectively. 1.0 mg/l CNPE is not toxic for the zebrafish embryos/larvae. 2.0 to 8.0 CNPE doses caused some abnormalities in embryos/larvae morphology, including lack of body parts, tail deformities, chorda deformity, bubbled head, scoliosis, lordosis, weak or non-pigmentation, decreased heart rate and larva length. 16.0 mg/l CNPE caused mortality in 72 hpf. The expression levels of seven immune system-related genes (il-1β, il-8, cebp, tlr4, hsp70, NF-kB, and mtf-1) were examined. The transcription level of il-1β, il-8, tlr4, hsp70, and NF-kB genes significantly increased in the CNPE exposure groups. While the expression of the mtf-1 gene considerably decreased, the cebp gene expression level did not change in the 4.0 and 8.0 mg/l CNPE doses. In conclusion, CNPE could induce developmental toxicity with malformations in embryos/larvae and alter the gene expression.

Bok choy (Brassica rapa) grown in copper oxide nanoparticles-amended soils exhibits toxicity in a phenotype-dependent manner: Translocation, biodistribution and nutritional disturbance

The comparative toxicity of nano/bulk cupric oxide (CuO) and ionic copper (Cu) in Rosie and Green bok choy (Brassica rapa) varieties, with higher and lower anthocyanin contents, respectively, was investigated. Both phenotypes were cultivated for 70 days in natural soil amended with nano CuO (nCuO), bulk CuO (bCuO), and Cu chloride (CuCl₂) at 75, 150, 300, and 600 mg Cu/kg soil. Essential elements in tissues, agronomical parameters, chlorophyll content, and Cu distribution in leaf were determined. In both varieties, nCuO treatments significantly increased Cu uptake in roots, compared with bCuO and CuCl₂ (p ≤ 0.05). At all treatment concentrations, Rosie variety had more Cu than Green. More physiological impairments such as chlorophyll and leaf biomass reduction were observed in treated-Rosie varieties, compared to Green plants. The adverse effects were higher in nCuO-treated plants than their bCuO- or ionic Cu-exposed counterparts. Different distribution patterns of the translocated Cu in leaf midrib and parenchyma depended on particle size and plant phenotype, as demonstrated by two-photon microscopy. The different effects of CuO-based compounds in Rosie and Green varieties may be related to the anthocyanin content. These findings help to understand the factors involved in nanoparticles uptake and translocation to plant edible parts.

In vitro and in vivo impact assessment of eco-designed CuO nanoparticles on non-target aquatic photoautotrophic organisms

This work has assessed the impact of copper oxide nanoparticles (CuONPs), designed via green route, toward photosynthetic apparatus on aquatic photoautotrophic organisms. In order to filling knowledge gaps, in vitro and in vivo assays were performed, using cyanobacterial phycocyanin (C-PC) from Arthrospira platensis and Lemna valdiviana plants (duckweed), respectively. Impairment in light energy transfer became evident in C-PC exposed to CuONPs, giving rise to an increase of light absorption and a suppression of fluorescence emission. Fourier transform infrared spectroscopy (FTIR) results showed that C-PC structures might be altered by the nanoparticles, also revealed that CuONPs preferably interacts with -NH functional groups. The data also revealed that CuONPs affected the chlorophyll a content in duckweed leaves. In addition, photosystem II (PSII) performance was significantly affected by CuONPs, negatively impacting the PSII photochemical network. In summary, the results point out that, even eco-friendly designed, CuONPs may negatively affect the photosynthetic process when accumulated by aquatic photoautotrophs.

Study of organochlorine pesticides and heavy metals in soils of the Juarez valley: an important agricultural region between Mexico and the USA

The Juarez Valley is an important agricultural region in northern Mexico, conveniently organized into three modules (I to III). For decades, their soils have been exposed to organochlorine pesticides (OCPs) and also have been irrigated with wastewaters, which may contain heavy metals. Nowadays, there is very limited information regarding the presence of OCPs and heavy metals in these soils. Thus, the aim of this study was to diagnose these soils for OCPs and heavy metal content by using gas chromatography coupled with electron micro-capture detector and atomic absorption spectrometry, respectively. The results indicated that 4,4'-dichlorodiphenyldichloroethylene and 4,4'-dichlorodiphenyltrichloroethane were primarily disseminated across the three modules since they were found in 100% and 97% of the analyzed soils, respectively. According to international regulations, none of the determined OCP concentrations are out of the limits. Additionally, the Cu, Zn, Fe, Pb, and Mn were found in all sampled soils from the three modules. The highest concentration of Fe was found in module II (1902.7 ± 332.2 mg kg^-1), followed by Mn in module III (392.43 ± 74.43 mg kg^-1), Zn in module I (38.36 ± 26.57 mg kg^-1), Pb in module II (23.48 ± 6.48 mg kg^-1), and Cu in module I (11.04 ± 3.83 mg kg^-1) (p ≤ 0.05). These values did not exceed the limits proposed by international standards. The Cd was detected in most of the analyzed soils and all their values, with an average of 2 mg kg^-1, surpassed the Mexican standards (0.35 mg kg^-1). This study has mapped the main OCPs and heavy metals in the Juarez Valley and can serve as a starting point to further monitor the behave of xenobiotics. Since these recalcitrant compounds might be bio-accumulated in biological systems, further analytical methods, as well as remediation techniques, should be developed.

Short term changes in the abundance of nitrifying microorganisms in a soil-plant system simultaneously exposed to copper nanoparticles and atrazine

Copper nanoparticles (NCu) may co-exist with other pollutants in agricultural soils, such as pesticides. However, this has been little evaluated yet. Thus, possible effects of the simultaneous applications of pesticides and NCu on biogeochemical cycles are expected, for example on the nitrogen cycle. Therefore, the aim of this work was to evaluate the effect of simultaneous application of the herbicide atrazine (ATZ) and NCu on the abundance of total bacteria and nitrifying communities: ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Moreover, the ATZ dissipation was evaluated. A soil-plant system containing ATZ at field dose (3 mg a.i. kg^-1) was mixed with two doses of NCu (0.05% or 0.15% w/w). Changes in the abundance of 16S rRNA and ammonia monooxygenase (amoA) genes of AOA and AOB were evaluated by real-time quantitative PCR (qPCR) at three sampling times (1, 15 and 30 days). The residual ATZ and nitrate production were also measured. The results showed significant differences in microbial composition and abundance over the 30 days of the experiment. Particularly, an initial decrease was observed in total bacterial abundance due to the presence of ATZ and NCu respect to ATZ alone (~60%). The abundance of AOA was also remarkably reduced (~85%), but these communities gradually recovered towards the end of the experiment. Conversely, AOB abundance initially increased (>100%) and remained mainly unaltered in soil exposed to ATZ and NCu 0.15% w/w, where nitrate formation was also constant. Moreover, NCu decreased the ATZ dissipation, which was translated in a 2-fold increase on the ATZ half-life values (T_1/2). This study demonstrates that the simultaneous presence of NCu and ATZ may represent a risk for the total bacteria present in soil and sensitive microorganisms such as nitrifying communities, and changes in the dissipation of the pesticide could influence this process.

Toxicity of copper hydroxide nanoparticles, bulk copper hydroxide, and ionic copper to alfalfa plants: A spectroscopic and gene expression study

Bulk Cu compounds such as Cu(OH)₂ are extensively used as pesticides in agriculture. Recent investigations suggest that Cu-based nanomaterials can replace bulk materials reducing the environmental impacts of Cu. In this study, stress responses of alfalfa (Medicago sativa L.) seedlings to Cu(OH)₂ nanoparticle or compounds were evaluated. Seeds were immersed in suspension/solutions of a Cu(OH)₂ nanoform, bulk Cu(OH)₂, CuSO₄, and Cu(NO₃)₂ at 25 and 75 mg/L. Six days later, the germination, seedling growth, and the physiological and biochemical responses of sprouts were evaluated. All Cu treatments significantly reduced root elongation (average = 63%). The ionic compounds at 25 and 75 mg/L caused a reduction in all elements analyzed (Ca, K, Mg, P, Zn, and Mn), excepting for S, Fe and Mo. The bulk-Cu(OH)₂ treatment reduced K (48%) and P (52%) at 75 mg/L, but increased Zn at 25 (18%) and 75 (21%) mg/L. The nano-Cu(OH)₂ reduced K (46%) and P (48%) at 75 mg/L, and also P (37%) at 25 mg/L, compared with control. Confocal microscopy images showed that all Cu compounds, at 75 mg/L, significantly reduced nitric oxide, concurring with the reduction in root growth. Nano Cu(OH)₂ at 25 mg/L upregulated the expression of the Cu/Zn superoxide dismutase gene (1.92-fold), while ionic treatments at 75 mg/L upregulated (∼10-fold) metallothionein (MT) transcripts. Results demonstrated that nano and bulk Cu(OH)₂ compounds caused less physiological impairments in comparison to the ionic ones in alfalfa seedlings.

ZnO nanoparticles increase photosynthetic pigments and decrease lipid peroxidation in soil grown cilantro (Coriandrum sativum)

The growth of the nanotechnology industry has raised concerns about its environmental impacts. In particular, the effect on terrestrial plants, which are the primary producers of the global food chain, is widely debated. In this study, cilantro plants (Coriandrum sativum) were cultivated for 35 days in soil amended with ZnO nanoparticles (N ZnO), bulk ZnO (B ZnO) and ZnCl₂ (ionic/I Zn) at 0-400 mg/kg. Photosynthetic pigments, lipid peroxidation, ¹NMR-based metabolic, and ICP-based metallomic profiles were evaluated. All Zn compounds increased the chlorophyll content by at least 50%, compared to control. Only N ZnO at 400 mg/kg decreased lipid peroxidation by 70%. ¹NMR data showed that all compounds significantly changed the carbinolic-based compounds, compared with control. Highest root and shoot uptake of Zn was observed at B 400 and I 100, respectively. Results of this study corroborates that N ZnO at a concentration <400 mg/kg improved photosynthesis pigments and the defense response in cilantro plants cultivated in organic soil.