In vivo phytotoxicity, uptake, and translocation of PbS nanoparticles in maize (Zea mays L.) plants

A nano-bioengineered cobalt oxide biostimulant mediated regulation of physiological, biochemical, and antioxidant mechanisms in Zea mays

Biogenic synthesized cobalt nanoparticles (NPs), dose optimization toxicity, and metabolic studies of Zea mays are very important before their application in the field. Here, we investigate the morphological, biochemical, and metabolic response of summer maize (Zea mays) against bulk cobalt chloride and Withania-assisted bioengineered cobalt NPs. It was found that cobalt chloride as bulk and concentration of 100 mg/L NPs inhibits growth via significant changes their metabolic and biochemical molecules. While biogenic assisted with Withania, cobalt NPs with concentrations of 50 and 100 mg/L have shown a significant increase in shoot length by 15% and 9% respectively. Root length was found to be decreased at 25 mg/L and 50 mg/L as compared to control. Fresh and dry weight was found to be increased at 25 mg/L and 50 mg/L. However, chlorophyll contents seemed to decline at 25 mg/L and increased at 50 mg/L. Carbohydrate content was found to be decreased at 50 mg/L and 25 mg/L by 76% and 70% respectively. Starch content was found to be increased at 25 mg/L and 50 mg/L by 28% and 33% respectively. Nitrate content was found to be decreased at 50 mg/L by 17%. However, higher tested concentrations showed a very much decrease in these compounds. Results displayed that a small quantity of cobalt oxide nanoparticles had a stimulatory impact on the seedling development while a higher quantity encouraged an inhibitory effect. 100 mg/L also showed an increase in activities when comparison was done against control. At 25 mg/L all activities were found to be maximum. This increased level suggests that the congregation of these secondary metabolites generates an oxidative response in plants when exposed to Cobalt oxide nanoparticles and cobalt chloride. However, further mechanistic research should be adopted as our experimental findings ruled out the generalized phytotoxicity of plants.

Nanotechnology in Plant Nanobionics: Mechanisms, Applications, and Future Perspectives

Plants are vital to ecosystems and human survival, possessing intricate internal and inter-plant signaling networks that allow them to adapt quickly to changing environments and maintain ecological balance. The integration of engineered nanomaterials (ENMs) with plant systems has led to the emergence of plant nanobionics, a field that holds the potential to enhance plant capabilities significantly. This integration may result in improved photosynthesis, increased nutrient uptake, and accelerated growth and development. Plants treated with ENMs can be stress mitigators, pollutant detectors, environmental sensors, and even light emitters. This review explores recent advancements in plant nanobionics, focusing on nanoparticle (NP) synthesis, adhesion, uptake, transport, fate, and application in enhancing plant physiological functioning, stress mitigation, plant health monitoring, energy production, environmental sensing, and overall plant growth and productivity. Potential research directions and challenges in plant nanobionics are highlighted, and how material optimization and innovation are propelling the growth in the field of smart agriculture, pollution remediation, and energy/biomass production are discussed.

Phytotoxicity and growth enhancement properties of magnesium and zinc co-doped aluminum oxide nanoparticles on barley (Hordeum vulgare L.)

Nanotechnology has been utilized in diverse domains, encompassing sustainable agriculture. However, the ecotoxicity and environmental safety of nanoparticles need to be evaluated before their large-scale use. This study synthesizes and characterizes magnesium (Mg) and zinc (Zn) co-doped aluminum (Al) oxide (MgZnAl2O4) NPs and elucidates its potential growth-promoting or genotoxic performance on barley (Hordeum vulgare L.). XRD, EDX, TEM, SEM, and XPS were used to characterize the MgZnAl2O4 NPs. After characterization, the seedlings were grown in a hydroponic solution containing 0, 50, 100, 200, and 400 mg L-1 NPs for 3 weeks. The germination, growth indices, photosynthetic parameters, and nutrient absorption properties were determined. Confocal microscopy, TEM, and SEM were utilized to follow the path and reveal the structural and morphological effects of NPs. The potential genotoxic effect was evaluated using the RAPD-PCR method. Elemental composition analysis of plant parts confirmed that synthesized MgZnAl2O4 NPs, sized at 21.8 nm, were up-taken by the plant roots, leading to increased Mg, Zn, and Al contents of leaves. In addition, compared with the untreated control, the abundance of Ca, K, B, Fe, Mn, and Cu were increased by the NPs treatment. In addition, physiological indices like germination rate (~ 11%), root and leaf growth (15-29%), chlorophyll, and carotenoids (~ 39%) pigments were significantly raised by the NPs inclusion. It can be concluded that low concentrations (< 200 mg L-1) of MgZnAl2O4 NPs enhance growth parameters effectively and are safe for plant growth. On the other hand, a phytotoxic and genotoxic impact was observed at high concentrations (100-400 mg L-1). However, considerable amounts of NPs were found to be adsorbed on roots, disrupting root morphology and cell membrane integrity, thus nutrient trafficking and transport. Therefore, it is recommended that MgZnAl2O4 NPs can be used in barley breeding programs at low concentrations. Adding micro- or macroelements required by plants to the NP composition is a promising way to compensate for plant nutrition. However, the negative effects of MgZnAl2O4 NPs on the environment and other living beings due to their genotoxic effects at high doses must be carefully considered.

Efficacy of soil drench and foliar application of iron nanoparticles on the growth and physiology of Solanum lycopersicum L. exposed to cadmium stress

Cadmium (Cd) can harm the yield and quality of vegetables, threatening food safety. Essential microelements such as iron are crucial for plant growth and can help alleviate heavy metal stress. Recently, nanoparticles have been studied as eco-friendly solutions for mitigating heavy metal stress in plants. In the present study, iron nanoparticles (FeNPs) at 0, 100, and 300 mg/L were applied as soil drenches and foliar sprays to tomato plants under cadmium stress. A comparison was made between the application methods of FeNPs by evaluating the growth parameters of tomato plants, including shoot length (SL), root length (RL), number of branches (NB), number of leaves per plant (NL), and leaf area (LA), as well as by assessing biochemical and antioxidant enzyme parameters. In the Cd stress treatment, the protein content decreased by 24.71%, and the phenolic and flavonoid content of the tomato plants also decreased due to cadmium stress, with levels decreasing from 16.07 to 6.9 µg and from 0.36 to 0.16 µg, respectively. Compared with the soil drench, 100 mg/L FeNPs significantly improved the parameters of Cd-stressed plants when used as a foliar spray, leading to increases in shoot length, root length, fruit weight, number of fruits, number of leaves, and number of branches by 42%, 66%, 24%, 66%, 173%, and 45%, respectively. Tomato plants treated with this spray presented increased carotenoid and lycopene contents. FeNP foliar spray also reduced Cd accumulation in plant tissues. This technique shows promise in alleviating Cd stress in vulnerable vegetable plants such as tomatoes.

Biogenic zinc oxide nanoregulator determines the quantitative analysis of morpho-anatomical and antioxidant capacity in Lactuca sativa L

Zinc oxide nanoparticles (ZnO NPs) can possibly serve as a pervasive source of essential nutrient zinc in agricultural crops in the future. The major environmental concerns with ZnO NPs might be their toxicity and incorrect dosage, which might lead to crop damage and environmental pollution. Interplay between ZnO NPs and Lactuca sativa (L. sativa) will be of interest, yet little is known about apropos interaction of these two, which will assist in optimizing the dose of ZnO NPs for their commercial use in agriculture. The current study aimed to investigate the growth, anatomical, and antioxidative responses of L. sativa against ZnO NPs and zinc acetate. ZnO NPs were foliar sprayed with concentrations of 0, 25, 50, and 100 ppm. ZnO NPs remarkably promoted L. sativa growth, leaf water content, and biomass accumulation; however, they declined root growth. The foliar spray of ZnO NPs improved the thickness of the stem hypodermis, cortex, pericycle, and phloem, while decreasing the stem diameter, thickness of the epidermis, and number of vascular bundles. ZnO NPs rigorously declined the cell area of xylem but slightly improved it in phloem. Unlike stem cells' anatomical responses to ZnO NPs, the root cells behaved otherwise. Overall, the antioxidative activity of L. sativa considerably improved at 25 ppm concentration and decreased at 100 ppm. Generally, low and medium concentrations of ZnO NPs promoted plant morphological, anatomical, and antioxidant traits, while higher doses inhibited the same traits. Contrary to this, Zn acetate displayed severe toxic effects on almost all studied anatomical traits.

Nanoparticle-specific transformations dictate nanoparticle effects associated with plants and implications for nanotechnology use in agriculture

Nanotechnology shows potential to promote sustainable and productive agriculture and address the growing population and food demand worldwide. However, the applications of nanotechnology are hindered by the lack of knowledge on nanoparticle (NP) transformations and the interactions between NPs and macromolecules within crops. In this Review, we discuss the beneficial and toxicity-relieving transformation products of NPs that provide agricultural benefits and the toxic and physiology-disturbing transformations that induce phytotoxicities. Based on knowledge related to the management of NP transformations and their long-term effects, we propose feasible design suggestions to attain nano-enabled efficient and sustainable agricultural applications.

Current research on ecotoxicity of metal-based nanoparticles: from exposure pathways, ecotoxicological effects to toxicity mechanisms

Metal-based nanoparticles have garnered significant usage across industries, spanning catalysis, optoelectronics, and drug delivery, owing to their diverse applications. However, their potential ecological toxicity remains a crucial area of research interest. This paper offers a comprehensive review of recent advancements in studying the ecotoxicity of these nanoparticles, encompassing exposure pathways, toxic effects, and toxicity mechanisms. Furthermore, it delves into the challenges and future prospects in this research domain. While some progress has been made in addressing this issue, there is still a need for more comprehensive assessments to fully understand the implications of metal-based nanoparticles on the environment and human well-being.

Nanoparticles and root traits: mineral nutrition, stress tolerance and interaction with rhizosphere microbiota

MAIN CONCLUSION

This review article highlights a broader perspective of NPs and plant-root interaction by focusing on their beneficial and deleterious impacts on root system architecture (RSA). The root performs a vital function by securing itself in the soil, absorbing and transporting water and nutrients to facilitate plant growth and productivity. In dicots, the architecture of the root system (RSA) is markedly shaped by the development of the primary root and its branches, showcasing considerable adaptability in response to changes in the environment. For promoting agriculture and combating global food hunger, the use of nanoparticles (NPs) may be an exciting option, for which it is essential to understand the behaviour of plants under NPs exposure. The nature of NPs and their physicochemical characteristics play a significant role in the positive/negative response of roots and shoots. Root morphological features, such as root length, root mass and root development features, may regulated positively/negatively by different types of NPs. In addition, application of NPs may also enhance nutrient transport and soil fertility by the promotion of soil microorganisms including plant growth-promoting rhizobacteria (PGPRs) and also soil enzymes. Interestingly the interaction of nanomaterials (NMs) with rhizospheric bacteria can enhance plant development and soil health. However, some studies also suggested that the increased use of several types of engineered nanoparticles (ENPs) may disrupt the equilibrium of the soil-root interface and unsafe morphogenesis by causing the browning of roots and suppressing the growth of root and soil microbes. Thus, this review article has sought to compile a broader perspective of NPs and plant-root interaction by focusing on their beneficial or deleterious impacts on RSA.

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.

Metabolomics reveals the phytotoxicity mechanisms of foliar spinach exposed to bulk and nano sizes of PbCO3

PbCO3 is an ancient raw material for Pb minerals and continues to pose potential risks to the environment and human health through mining and industrial processes. However, the specific effects of unintentional PbCO3 discharge on edible plants remain poorly understood. This study unravels how foliar application of PbCO3 induces phytotoxicity by potentially influencing leaf morphology, photosynthetic pigments, oxidative stress, and metabolic pathways related to energy regulation, cell damage, and antioxidant defense in Spinacia oleracea L. Additionally, it quantifies the resultant human health risks. Plants were foliarly exposed to PbCO3 nanoparticles (NPs) and bulk products (BPs), as well as Pb2+ at 0, 5, 10, 25, 50, and 100 mg·L-1 concentrations once a day for three weeks. The presence and localization of PbCO3 NPs inside the plant cells were confirmed by TEM-EDS analysis. The maximum accumulation of total Pb was recorded in the root (2947.77 mg·kg-1 DW for ion exposure), followed by the shoot (942.50 mg·kg-1 DW for NPs exposure). The results revealed that PbCO3 and Pb2+ exposure had size- and dose-dependent inhibitory effects on spinach length, biomass, and photosynthesis attributes, inducing impacts on the antioxidase activity of CAT, membrane permeability, and nutrient elements absorption and translocation. Pb2+ exhibited pronounced toxicity in morphology and chlorophyll; PbCO3 BP exposure accumulated the most lipid peroxidation products of MDA and H2O2; and PbCO3 NPs triggered the largest cell membrane damage. Furthermore, PbCO3 NPs at 10 and 100 mg·L-1 induced dose-dependent metabolic reprogramming in spinach leaves, disturbing the metabolic mechanisms related to amino acids, antioxidant defense, oxidative phosphorylation, fatty acid cycle, and the respiratory chain. The spinach showed a non-carcinogenic health risk hierarchy: Pb2+ > PbCO3 NPs > PbCO3 BPs, with children more vulnerable than adults. These findings enhance our understanding of PbCO3 particle effects on food security, emphasizing the need for further research to minimize their impact on human dietary health.

Impact of nanopollution on plant growth, photosynthesis, toxicity, and metabolism in the agricultural sector: An updated review

Nanotechnology provides distinct benefits to numerous industrial and commercial fields, and has developed into a discipline of intense interest to researchers. Nanoparticles (NPs) have risen to prominence in modern agriculture due to their use in agrochemicals, nanofertilizers, and nanoremediation. However, their potential negative impacts on soil and water ecosystems, as well as plant growth and physiology, have caused concern for researchers and policymakers. Concerns have been expressed regarding the ecological consequences and toxicity effects associated with nanoparticles as a result of their increased production and usage. Moreover, the accumulation of nanoparticles in the environment poses a risk, not only because of the possibility of plant damage but also because nanoparticles may infiltrate the food chain. In this review, we have documented the beneficial and detrimental effects of NPs on seed germination, shoot and root growth, plant biomass, and nutrient assimilation. Nanoparticles exert toxic effects by inducing ROS generation and stimulating cytotoxic and genotoxic effects, thereby leading to cell death in several plant species. We have provided possible mechanisms by which nanoparticles induce toxicity in plants. In addition to the toxic effects of NPs, we highlighted the importance of nanomaterials in the agricultural sector. Thus, understanding the structure, size, and concentration of nanoparticles that will improve plant growth or induce plant cell death is essential. This updated review reveals the multifaceted connection between nanoparticles, soil and water pollution, and plant biology in the context of agriculture.

Copper and Silver Nanoparticle Seed Priming and Foliar Spray Modulate Plant Growth and Thrips Infestation in Capsicum spp

Nanoparticles (NPs) have the potential to improve plant health and secondary metabolite production. In the present study, three different NPs, i.e., Ag, Cu, and Cu-Ag NPs were produced in the range from 25 to 86 nm, with zeta potentials ranging from -28.8 to -38.5 mV. The synthesized NPs were used for seed priming and foliar spray on three varieties of Capsicum annuum. L, i.e., Arka Sweta (AS), Arka Meghana (AM), and Arka Harita (AH) plants grown under greenhouse conditions. Seed priming at various concentrations of NPs (1, 10, 20 ppm) enhanced the seed germination (96%), seedling vigor index (2494-3112.66), seedling length (6-49%), and biomass (46%) of 45 days old Arka Meghana seedlings. Additionally, all plant tissues accumulated significantly higher amounts of chlorophyll (51-142%), carotenoids (23-94.2%), total phenolic content (73%), and total flavonoid content (57%), compared with the control (p ≤ 0.05). The foliar spray of NPs (20-100 ppm) has a protective effect on the chili plants against thrips infestation (30-76%). The foliar spray enhanced chlorophyll (15-62%), carotenoids (15-50%), total phenolic content (20-62%), total flavonoid content (64-99%), reducing sugars (15-97%), total antioxidant activity (15-142%), ferric reducing antioxidant power assay (15-109%), DPPH (129-54 mg mL-1), and capsaicinoids (capsaicin and dihydrocapsaicin) (82-128%). This study illustrates that Ag, Cu, and Cu-Ag NPs suppress thrips infestation and proliferation with enhanced plant growth and biochemical activity, which is inversely proportional to the NP size. Chemical NPs play a crucial role in the economic significance of chili plants, offering a promising avenue for developing pesticides to effectively combat thrips infestation. This advancement holds great potential in enhancing the overall agronomic productivity of the chili crops.

Translocation of CdS nanoparticles in maize (Zea mays L.) plant and its effect on metabolic response

Cadmium sulfide nanomaterials are of great concern because of their potential toxicity and unavoidable releases due to multiple commercial applications of nanoparticles (NPs). Commercial NPs act as mediators of damage to plant cells and pose potential toxicity to plants and human health. In the current study, investigated the phytotoxicology, absorption, translocation, antioxidant enzyme activity, and metabolic profiles of maize (Zea mays L.) seedlings exposed to different hydroponic treatments for fifteen days. The different concentrations of CdS NPs (3, 15, 30, 50, and 100 mg/L), 0.3 mg/L Cd ions, and unexposed control were performed in treatments. The results indicated that CdS NPs could present phytotoxic effects on seed germination and root elongation. Compared to the control, the CdS NPs dramatically reduced the shoots and root biomass, as well as the shape of the roots. Transmission electron microscopy and energy-dispersive mapping confirmed that CdS NPs could penetrate the maize root epidermis and bioaccumulate in the shoots with high concentrations. According to metabolomics studies, exposure to CdS NPs and Cd ions would result in metabolic disruption. Based on the statistical analysis, 290 out of 336 metabolites (86.30%) were obviously inhibited. The findings of this study demonstrated possible risks of emerging potential toxic NPs, and the release of these NPs to environment is a serious concern for agricultural activities.

Nanotoxicity assessment in plants: an updated overview

Nanotechnology is rapidly emerging and innovative interdisciplinary field of science. The application of nanomaterials in agricultural biotechnology has been exponentially increased over the years that could be attributed to their uniqueness, versatility, and flexibility. The overuse of nanomaterials makes it crucial to determine their fate and distribution in the in vitro (in cell and tissue cultures) and in vivo (in living species) biological environments by investigating the nano-biointerface. The literature states that the beneficial effects of nanoparticles come along with their adverse effects, subsequently leading to an array of short-term and long-term toxicities. It has been evident that the interplay of nanoparticles with abiotic and biotic communities produces several eco-toxicological effects, and the physiology and biochemistry of crops are greatly influenced by the metabolic alterations taking place at cellular, sub-cellular, and molecular levels. Numerous risk factors affect nanoparticle's accumulation, translocation, and associated cytogenotoxicity. This review article summarizes the contributing factors, possible mechanisms, and risk assessment of hazardous effects of various types of nanoparticles to plant health. The methods for evaluating the plant nanotoxicity parameters have been elaborated. Conclusively, few recommendations are put forward for designing safer, high-quality nanomaterials to protect and maintain environmental safety for smarter agriculture demanded by researchers and industrialists.

Engineered nanoparticles in plant growth: Phytotoxicity concerns and the strategies for their attenuation

In the agricultural sector, the use of engineered nanoparticles (ENPs) has been acclaimed as the next big thing for sustaining and increasing crop productivity. A vast amount of literature is available regarding the growth-promoting attributes of different ENPs. In this context, it has been emphasized that the ENPs can bolster vegetative growth, leaf development, and seed setting and also help in mitigating the effects of abiotic and biotic stresses. At the same time, there have been a lot of speculations and concerns regarding the phytotoxicity of ENPs off-late. In this connection, many research articles have presented the negative effects of ENPs on plant systems. These studies have highlighted that almost all the ENPs impart a certain degree of phytotoxicity in terms of reduction in growth, biomass, impairment of photosynthesis, oxidative status of plant cells, etc. Mostly, the ENPs based on metal or metal oxides (Cd, Cr, Pb, Ag, Ce, etc.) and nonmetals (C) that are introduced into the environment are known to incite inhibitory effects. However, the phytotoxicity of ENPs are known to be determined mostly by the chemical nature of the element, size, surface charge, coating molecules, and abiotic factors like pH and light. This review article, therefore, elucidates the phytotoxic properties of different ENPs and the plant responses induced at the molecular level subjected to nanoparticle exposure. Moreover, the article highlights the probable strategies that may be adopted for the suppression of the phytotoxicity of ENPs to ensure the safe and sustainable application of ENPs in crop fields.

Potential Threat of Lead Oxide Nanoparticles for Food Crops: Comprehensive Understanding of the Impacts of Different Nanosized PbOx (x = 1, 2) on Maize (Zea mays L.) Seedlings In Vivo

PbO_x (PbO₂ and PbO, x = 1, 2) nanoparticles are emerging contaminants in dust, soil, and water due to extensive application of commercial lead products. As far as we know, the current studies are first conducted to understand the phytotoxic effects of PbO₂ (10 ± 3 nm) and PbO NPs (20 ± 5 nm) on maize (Zea mays L.) grown in hydroponic treatments. The exposure assays indicated that phytotoxic effects were dose- and size-dependent on PbO_x NPs. Water uptake would be the crucial mechanism to govern the effects of PbO_x on maize seed germination and root elongation, while the nanosize of particles and water transpiration processes would control maize growth and biomass production. PbO_x NPs significantly influenced the macro- and micronutrients in roots and shoots of maize and significantly affected the maize growth and grain development. Our findings provide clear-cut evidence that PbO/PbO₂ NPs can bioaccumulate in maize cell organelles via apoplastic and symplastic routes from the seed and root pathways along with water uptake and transportation. The significance of this research elucidates the impacts of PbO/PbO₂ NPs on food security and indicates the threat of emerging PbO/PbO₂ NPs to human dietary health.

In vivo phytotoxic effect of yttrium-oxide nanoparticles on the growth, uptake and translocation of tomato seedlings (Lycopersicon esculentum)

The potential toxicity and ecological risks of rare-earth nanoparticles in the environment have become a concern due to their widespread application and inevitable releases. The integration of hydroponics experiments, partial least squares structural equation modeling (PLS-SEM), and Transmission Electron Microscopy (TEM) were utilized to investigate the physiological toxicity, uptake and translocation of yttrium oxide nanoparticles (Y₂O₃ NPs) under different hydroponic treatments (1, 5, 10, 20, 50 and 100 mg·L^-1 of Y₂O₃ NPs, 19.2 mg·L^-1 Y(NO₃)₃ and control) in tomato (Lycopersicon esculentum) seedlings. The results indicated that Y₂O₃ NPs had a phytotoxic effect on tomato seedlings' germination, morphology, physiology, and oxidative stress. The Y₂O₃ NPs and soluble Y^III reduced the root elongation, bud elongation, root activity, chlorophyll, soluble protein content and superoxide dismutase and accelerated the proline and malondialdehyde in the plant with increasing concentrations. The phytotoxic effects of Y₂O₃ NPs on tomato seedlings had a higher phytotoxic effect than soluble Y^III under the all treatments. The inhibition rates of different levels of Y₂O₃ NPs in shoot and root biomass ranged from 0.2% to 6.3% and 1.0-11.3%, respectively. The bioaccumulation and translocation factors were less than 1, which suggested that Y₂O₃ NPs significantly suppressed shoot and root biomass of tomato seedlings and easily bioaccumulated in the root. The observations were consistent with the process of concentration-dependent uptake and translocation factor and confirmed by TEM. Y₂O₃ NPs penetrate the epidermis, enter the cell wall, and exist in the intercellular space and cytoplasm of mesophyll cells of tomato seedlings by endocytic pathway. Moreover, PLS-SEM revealed that the concentration of NPs significantly negatively affects the morphology and physiology, leading to the change in biomass of plants. This study demonstrated the possible pathway of Y₂O₃ NPs in uptake, phytotoxicity and translocation of Y₂O₃ NPs in tomato seedlings.

Understanding the phytotoxic impact of Al3+, nano-size, and bulk Al2O3 on growth and physiology of maize (Zea mays L.) in aqueous and soil media

The release and accumulation of metal-oxide nanoparticles in soils have threatened terrestrial plants. However, limited knowledge is available on the accumulation of nano-Al₂O₃ (22 nm), bulk-Al₂O₃ (167 nm), and Al³⁺ by maize plants and the subsequent impact on its physiology and growth in agar (0.7% w/v), hydroponic (1X), and soil. Maize plants were cultivated with 0.05-2 mg g^-1 or ml^-1 of three Al types and their biological attributes, oxidative status, Al bioaccumulation, and translocation were measured. The ICP-MS results revealed a dose-dependent increase (P ≤ 0.05 or ≤0.01) in Al content in maize tissues following nano-Al₂O₃ and Al³⁺ exposure, however, plants exposed to bulk-Al₂O₃ showed no significant uptake of Al. Atomic mapping by EDX during SEM analysis and TEM revealed varied distributions of nano-Al₂O₃ from roots to aerial parts and intracellular transportation. Al deposition in tissues followed the order: Al³⁺ > nano-Al₂O₃ > bulk-Al₂O₃ and therefore, a similar trend of toxicity was observed for seed germination, the emergence of plant organs, length, biomass accumulation, total chlorophyll, phosphorus content, and total soluble protein. Oxidative stress was profoundly induced dose-dependently and was highest at 2 mg ml^-1 or g^-1 of Al³⁺ and nano-Al₂O₃ when superoxide radical formation, proline induction, activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (GPX), and glutathione reductase (GR) and membrane lipid peroxidation were measured. Aluminum toxicity was found higher in hydroponically grown maize compared to soil-grown maize. Forty days exposure in soil showed greater inhibition of maize growth compared to 20 days exposure. This study is significant in understanding the maize response to different Al types in soil and soil-free media.

Potential Applications of Engineered Nanoparticles in Plant Disease Management: A Critical Update

Plant diseases caused by pathogenic entities pose severe issues to global food security. Effective sensory applications and tools for the effective determination of plant diseases become crucial to the assurance of food supply and agricultural sustainability. Antibody-mediated molecular assays and nucleic acid are gold-standard approaches for plant disease diagnosis, but the evaluating methodologies are liable, complex, and laborious. With the rise in global food demand, escalating the food production in threats of diverse pathogen ranges, and climate change is a major challenge. Engineered nanoparticles (NPs) have been inserted into conventional laboratory sequence technologies or molecular assays that provide a remarkable increment in selectivity and sensitivity. In the present scenario, they are useful in plant disease management as well as in plant health monitoring. The use of NPs could sustainably mitigate numerous food security issues and or threats in disease management by decreasing the risk of chemical inputs and alleviating supra detection of pathogens. Overall, this review paper discusses the role of NPs in plant diseases management, available commercial products. Additionally, the future directions and their regulatory laws in the usage of the nano-diagnostic approach for plant health monitoring have been explained.

Combined toxicity of zinc oxide nanoparticles and cadmium inducing root damage in Phytolacca americana L

In recent years, nano-contamination in the soil environment has aroused concern. But it is still uncertain whether the interactions of nano- and metal-pollutants would have a combined toxic effect on plants. In this study, we investigated the effects of joint exposure to zinc oxide nanoparticles (ZnO NPs) and Cd on the root tissue of Phytolacca americana L. Spin-polarized density functional theory simulations assumed that the plant may undergo metal toxicity or acidosis upon joint exposure to ZnO NPs/Cd. Subsequently, experimental exposure of P. americana verified the combined toxic effects. The plant grew normally with a single treatment of ZnO NPs (500 mg/kg) or low doses of Cd (10 mg/kg). However, root growth was significantly inhibited with the combined treatments (up to 43% reduction); additionally, Cd ions were transported to the shoot, leading to shoot growth inhibition (translocation factor > 1). The antioxidant enzymes in the root (superoxide dismutase, peroxidase, and catalase) were highly activated to resist stress, accompanied by a greater than two-fold increase in thiobarbituric acid reactive substances. Corresponding to physiological indicators, biological transmission electron microscopy revealed severe damage to the root cells. Moreover, ZnO NPs/Cd accumulation was observed in the root cytoderm, which confirmed the toxicity of the combined effects. Our study provides insight into the potential combined toxicity of ZnO NPs and heavy metals in polluted environments, such as mining areas and electronic waste sites, and agricultural soils.

A biocide delivery system composed of nanosilica loaded with neem oil is effective in reducing plant toxicity of this biocide

One possible way to reduce the environmental impacts of pesticides is by nanostructuring biocides in nanocarriers because this promotes high and localized biocidal activity and can avoid toxicity to non-target organisms. Neem oil (NO) is a natural pesticide with toxicity concerns to plants, fish, and other organisms. Thus, loading NO in a safe nanocarrier can contribute to minimizing its toxicity. For this study, we have characterized the integrity of a nanosilica-neem oil-based biocide delivery system (SiO₂NP#NO BDS) and evaluated its effectiveness in reducing NO toxicity by the Allium cepa test. NO, mainly consisted of unsaturated fatty acids, was well binded to the SiO₂NP with BTCA crosslinker. Overall, this material presented all of its pores filled with the NO with fatty acid groups at both the surface and bulk level of the nanoparticle. The thermal stability of NO was enhanced after synthesis, and the NO was released as zero-order model with a total of 20 days without burst release. The SiO₂NP#NO BDS was effective in reducing the individual toxicity of NO to the plant system. NO in single form inhibited the seed germination of A. cepa (EC₅₀ of 0.38 g L^-1), and the effect was no longer observed at the BDS condition. Contrarily to the literature, the tested NO did not present cyto- and geno-toxic effects in A. cepa, which may relate to the concentration level and composition.

Smart nanomaterial and nanocomposite with advanced agrochemical activities

Conventional agriculture solely depends upon highly chemical compounds that have negatively ill-affected the health of every living being and the entire ecosystem. Thus, the smart delivery of desired components in a sustainable manner to crop plants is the primary need to maintain soil health in the upcoming years. The premature loss of growth-promoting ingredients and their extended degradation in the soil increases the demand for reliable novel techniques. In this regard, nanotechnology has offered to revolutionize the agrotechnological area that has the imminent potential over conventional agriculture and helps to reform resilient cropping systems withholding prominent food security for the ever-growing world population. Further, in-depth investigation on plant-nanoparticles interactions creates new avenues toward crop improvement via enhanced crop yield, disease resistance, and efficient nutrient utilization. The incorporation of nanomaterial with smart agrochemical activities and establishing a new framework relevant to enhance efficacy ultimately help to address the social acceptance, potential hazards, and management issues in the future. Here, we highlight the role of nanomaterial or nanocomposite as a sustainable as well stable alternative in crop protection and production. Additionally, the information on the controlled released system, role in interaction with soil and microbiome, the promising role of nanocomposite as nanopesticide, nanoherbicide, nanofertilizer, and their limitations in agrochemical activities are discussed in the present review.

Risks and phyto-uptake of micro-nano size particulates bound with potentially toxic metals in Pb-contaminated alkaline soil (NW China): The role of particle size fractions

The fate and risk in the environment of potentially toxic metals (PTMs) pollutants depends on the size-fractions of contaminated soil. In this study, the variable micro-nano size-fractions of 50-250 μm, 5-50 μm, 1-5 μm, <1 μm in long-term Pb-contaminated alkaline soil (NW China) were obtained by Sequential Wet Sieving Separation Procedure (SWSSP). The chemical speciation, mobility and risk of PTMs in micro-nano particle fractions as well as their uptaken and translocation in Maize (Zea mays L.) plant were systematically determined. The results demonstrated that higher accumulation of both investigated PTMs was observed in the fine fractions of <1 μm. The metallic Pb predominantly occurred in all size-fractions (65%-86%) identified by XPS, and the reducible forms of lead oxide (Ⅱ,Ⅳ) would also likely preferred to enrich in the fine fraction of <1 μm. The mobility and bioaccessibility of PTMs in fine fraction of <1 μm were higher than other fractions, which were identified by the multi-indices, enrichment factor (EF), accumulation factor (AF), mobility factor (MF), potential ecological risk index of single metal (E_rⁱ) and the comprehensive potential ecological risk index (RI). The scenario for phyto-uptake of Pb and Cu in <1 μm soil nanoparticles under pot tests indicated that the Pb and Cu enriched in <1 μm with high ecological risk were inclined to translocate into the Maize roots and shoots with nano size fractions. The results implied that further environmental management should be needed in order to prevent the risk of PTMs from Pb-bearing micro-nano size fractions in the industrial contaminated alkaline soil.

Physiological and biochemical effects of Ti3AlC2 nanosheets on rice (Oryza sativa L.)

MAX phase materials are a new type of nanomaterial with wide applications, but the potential effects of MAX phase materials on plants have not been reported. Herein, we selected Ti₃AlC₂ nanosheets as a typical MAX phase material to investigate its potential impacts on rice (Oryza sativa L.) at 0-1000 μg·mL^-1. The foliar application of Ti₃AlC₂ at 100 and 1000 μg·mL^-1 inhibited the growth of rice seedlings by producing excess reactive oxygen species (ROS). Furthermore, foliar spraying of Ti₃AlC₂ at 100 μg·mL^-1 decreased the stomatal aperture (78.6%) and increased the number of trichomes (100%). These responses demonstrated that the application of Ti₃AlC₂ could interfere with the immune system of plants by changing the structure and function of leaves, disturbing the activities of antioxidant enzymes. According to the above results, we concluded that the toxicity of Ti₃AlC₂ nanosheets on plants was mainly caused by the release of titanium ions. This study provides a valuable reference for understanding the impact of MAX phase materials on plants.

Impact of Nanoparticles on Plant Growth, Development, and Biomass

Nanoparticles are an extensive class of naturally occurred or man-made objects; it has been widely using in our daily life. As increasing usage, nanoparticles are also released into the environment and are becoming an emerged environmental pollution. In the past decade, impact of nanoparticles on plant growth and development has been becoming a major research topic in the environmental toxicology. In this chapter, we introduce a step-by-step protocol for investigating the effects of nanoparticles on plant growth and development as well as biomass production. Additionally, this protocol also tests the water content and the rate of root and up-ground part to better explain the impact of nanoparticles on plant growth. This protocol adopts plant tissue culture technology to culture plants which makes test easier and can be tested anytime during the year.

Knowledge domain and emerging trends in nanoparticles and plants interaction research: A scientometric analysis

The potential releases of nanoparticles (NPs) into soil medium have drawn considerable attention due to the increasing production and application of NPs worldwide. Understanding the interactions between NPs and plants is particularly important to assess the risks of NPs in the soil ecosystem. Although important knowledge has been gained about the NPs-plants interactions, current results of numerous published articles are still scattered. Therefore, this paper reviews the scientific progress in the NPs-plants interactions via a scientometric analysis to identify the main gaps and to provide future perspectives. Scientific documents on the interaction of nanoparticles and plant research during the period January 2000-July 2020 have been collected from Web of Science core collection and analyzed using CiteSpace. Overall, 9 scientometric indicators, i.e. literature quantity and growth trend, contributing countries, authors, institutions, keywords, cited journals, cited authors, and cited articles, are employed to understand the results retrieved from the 961 documents collected. The number of studies on nano-plant interaction research has been growing at an average annual rate of 56%. 71 countries and around 3380 authors have contributed to this field. Among the cited journals, Environmental Science and Technology stands out as the most-cited journal followed by Science of the Total Environment and Environmental Pollution, respectively. Moreover, the keyword citation burst, an indicator of the most active area of research or emerging trend, indicates that the beneficial side of nanoparticles and the trophic transfer require further exploration. This paper will be beneficial for fully understanding the salient research themes and the research trends of nano-plant interaction in future.

To-Do and Not-To-Do in Model Studies of the Uptake, Fate and Metabolism of Metal-Containing Nanoparticles in Plants

Due to the increasing release of metal-containing nanoparticles into the environment, the investigation of their interactions with plants has become a hot topic for many research fields. However, the obtention of reliable data requires a careful design of experimental model studies. The behavior of nanoparticles has to be comprehensively investigated; their stability in growth media, bioaccumulation and characterization of their physicochemical forms taken-up by plants, identification of the species created following their dissolution/oxidation, and finally, their localization within plant tissues. On the basis of their strong expertise, the authors present guidelines for studies of interactions between metal-containing nanoparticles and plants.