Influence of Metal Nanoparticles (NPs) on Germination and Yield of Oat (Avena sativa) and Berseem (Trifolium alexandrinum)

Effects of copper, and aluminium in ionic, and nanoparticulate form on growth rate and gene expression of Setaria italica seedlings

This study aims to determine the effects of copper, copper oxide nanoparticles, aluminium, and aluminium oxide nanoparticles on the growth rate and expression of ACT-1, CDPK, LIP, NFC, P5CR, P5CS, GR, and SiZIP1 genes in five days old seedling of Setaria italica ssp. maxima, cultivated in hydroponic culture. Depending on their concentration (ranging from 0.1 to 1.8 mg L-1), all tested substances had both stimulating and inhibiting effects on the growth rate of the seedlings. Copper and copper oxide-NPs had generally a stimulating effect whereas aluminium and aluminium oxide-NPs at first had a positive effect but in higher concentrations they inhibited the growth. Treating the seedlings with 0.4 mg L-1 of each tested toxicant was mostly stimulating to the expression of the genes and reduced the differences between the transcript levels of the coleoptiles and roots. Increasing concentrations of the tested substances had both stimulating and inhibiting effects on the expression levels of the genes. The highest expression levels were usually noted at concentrations between 0.4 and 1.0 mg/L of each metal and metal nanoparticle, except for SiZIP1, which had the highest transcript amount at 1.6 mg L-1 of Cu2+ and at 0.1-0.8 mg L-1 of CuO-NPs, and LIP and GR from the seedling treated with Al2O3-NPs at concentrations of 0.1 and 1.6 mg L-1, respectively.

Functional annotation of proteins in Catharanthus roseus shoot cultures under biogenic zinc nanotreatment

Nano-interactions are well known for their positive as well as negative impacts on the morphological and physiological systems of plants. Keeping in mind, the conformational changes in plant proteins as one of the key mechanisms for stress adaptation responses, the current project was designed to explore the effect of glutathione-capped and uncapped zinc nano-entities on Catharanthus roseus shoot cultures. Zinc nanotreatment (0.05 μg/mL) significantly induced ester production in C. roseus shoots as detected by Gas Chromatography-Mass spectrometry. These nanotreated shoots were further subjected to peptide-centric nano-LC-MS/MS analysis. Mass spectrometry followed by a Heat map revealed a significant effect of zinc nanoparticles on 59 distinct classes of proteins as compared to control. Proteins involved in regulating stress scavenging, transport, and secondary metabolite biosynthesis were robustly altered under capped zinc nanotreatment. UniProt database identified majority of the localization of the abundantly altered protein in cell membranes and chloroplasts. STRING and Cytoscape analysis assessed inter and intra coordination of triosephosphate isomerase with other identified proteins and highlighted its role in the regulation of protein abundance under applied stress. This study highlights the understanding of complex underlying mechanisms and regulatory networks involved in proteomic alterations and interactions within the plant system to cope with the nano-effect.

Efficacy of zinc-based nanoparticles in alleviating the abiotic stress in plants: current knowledge and future perspectives

Due to sessile, plants are unable to avoid unfavorable environmental conditions which leads to inducing serious negative effects on plant growth, crop yield, and food safety. Instead, various approaches were employed to mitigate the phytotoxicity of these emerging contaminants from the soil-plant system. However, recent studies based on the exogenous application of ZnO NPs approve of their important positive potential for alleviating abiotic stress-induced phytotoxicity leads to ensuring global food security. In this review, we have comprehensively discussed the promising role of ZnO NPs as alone or in synergistic interactions with other plant growth regulators (PGRs) in the mitigation of various abiotic stresses, i.e., heavy metals (HMs), drought, salinity, cold and high temperatures from different crops. ZnO NPs have stress-alleviating effects by regulating various functionalities by improving plant growth and development. ZnO NPs are reported to improve plant growth by stimulating diverse alterations at morphological, physiological, biochemical, and ultrastructural levels under abiotic stress factors. We have explained the recent advances and pointed out research gaps in studies conducted in earlier years with future recommendations. Thus, in this review, we have also addressed the opportunities and challenges together with aims to uplift future studies toward effective applications of ZnO NPs in stress management.

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.

Zinc oxide nanoparticles as potential hallmarks for enhancing drought stress tolerance in wheat seedlings

Drought is one of the major abiotic stresses which negatively affects plant growth and development. The current study evaluated the effects of drought on the growth, physiology, and biochemical attributes of wheat seedlings; and examined the role of foliar application of ZnO nanoparticles in alleviating drought-induced effects. Two wheat cultivars i.e., Anaj-2017 and FSD-2018 were grown in soil-filled pots and were subjected to 100% field capacity (FC) (well watered) and 50% of FC (drought stress). Whilst different treatments of ZnO nanoparticles spray included no spray, water spray, and 50, 100, and 150 ppm ZnO. Results demonstrated that drought caused a significant reduction in seedling fresh and dry weights, photosynthetic pigmentation, and antioxidant activities compared with a well-watered treatment. Nevertheless, the application of 100 and 150 ppm of ZnO nanoparticles effectively ameliorated the negative effects of drought and enhanced the performance of both cultivars under drought. Data revealed a significant increase in fresh and dry weight of shoot and root with the application of ZnO nanoparticles. A substantial increase of 73.68% and 28.51% in chlorophyll "a" and 26.15% and 50.02% in chlorophyll "b" was recorded with the application of 100 ppm of ZnO nanoparticles in Anaj-2017 and FSD-2018, respectively over control (0 ppm). The application of these nanoparticles also triggered the antioxidant defense system and protected the crop from oxidative damage. Averaged across different stress treatments, application of 150 and 100 ppm of ZnO nanoparticles increased the peroxidase activity by 60% and 72% in FSD-2018, and 15% and 23% in Anaj-2017, respectively compared with no spray. FSD-2018 outperformed Anaj-2017 regarding its overall performance under ZnO treatments and drought conditions. In a nutshell, it can be concluded that ZnO nanoparticles ameliorated the negative impacts of drought by improving the growth, physiology, and antioxidant defense of both wheat cultivars.

The role of nanoparticles in plant biochemical, physiological, and molecular responses under drought stress: A review

Drought stress (DS) is a serious challenge for sustaining global crop production and food security. Nanoparticles (NPs) have emerged as an excellent tool to enhance crop production under current rapid climate change and increasing drought intensity. DS negatively affects plant growth, physiological and metabolic processes, and disturbs cellular membranes, nutrient and water uptake, photosynthetic apparatus, and antioxidant activities. The application of NPs protects the membranes, maintains water relationship, and enhances nutrient and water uptake, leading to an appreciable increase in plant growth under DS. NPs protect the photosynthetic apparatus and improve photosynthetic efficiency, accumulation of osmolytes, hormones, and phenolics, antioxidant activities, and gene expression, thus providing better resistance to plants against DS. In this review, we discuss the role of different metal-based NPs to mitigate DS in plants. We also highlighted various research gaps that should be filled in future research studies. This detailed review will be an excellent source of information for future researchers to adopt nanotechnology as an eco-friendly technique to improve drought tolerance.

Role of metal-nanoparticles in farming practices: an insight

Nanotechnology introduces revolutionary approaches for agriculture in the form of nano-based pesticides, fertilizers, sensors, weed-controlling agents, enhanced seed germination materials, etc. Even though metal-nanoparticles (NPs) have shown their potential to improve crop yield, the mode of action at the cellular level and fate in the human body and the environment are not well understood yet. Several metal-nanoparticles have been studied extensively by researchers for their active role in enhancing the rate of seed germination and crop quality augmentation which may happen due to several mechanisms such as increased porosity in nano-primed seeds inducing up-regulation of the expression of aquaporin and Reactive Oxygen Species (ROS) genes involved in water uptake, improving the root dehydrogenase activity to enhance the water absorption capability, etc. However, researchers have also demonstrated and reported the possible toxicity of NPs in the environment due to their agricultural practices. But the fate of NPs and their environmental impact are still unclear and largely vary based on several factors such as the size of NPs, coating material, mode of discharge and locations, etc. This review thoroughly focuses on the mode of action of various NPs in seed germination and accumulation, translocation through cells, and potential environmental and health risks.

Effect of exogenous l-aspartate nano‑calcium on root growth, calcium forms and cell wall metabolism of Brassica napus L

Currently, l-aspartate nano‑calcium (Ca(L-asp)-NPs) has been sued as a calcium supplement for humans, but its effects on plants are not well elucidated. This study aimed to investigate the effect of exogenous Ca(L-asp)-NPs on the growth of rapeseed (Brassica napus L.) for the first time. Different concentrations (0, 50, 100, 150, and 200 mg L^-1) of Ca(L-asp)-NPs and 1.18 g L^-1 Ca(NO₃)₂ were used in the nutrient solution. The results indicated that Ca²⁺ released from Ca(L-asp)-NPs were absorbed by the roots, and had a significant effect on plant height, root length, biomass accumulation, and root structure formation, especially on the growth and development of coarse roots at 100 mg L^-1 Ca(L-asp)-NPs. Calcium (Ca) accumulation, Ca-pectinate, Ca-phosphate and Ca‑carbonate, and Ca-oxalate in plant roots and leaves were positively linked with Ca(L-asp)-NPs concentration. For cell wall, Ca(L-asp)-NPs treatment increased the content of pectin, and the activity of cell wall degrading enzymes in roots, such as pectin methyl-esterase (PME), cellulose enzyme (CE), polygalacturonase (PG), and β-galactosidase (β-Gal). For cell membrane osmotic regulation, Ca(L-asp)-NPs promoted the accumulation of soluble sugar and soluble protein. This finding suggests that 100 mg L^-1 Ca(L-asp)-NPs had the best growth-promoting effect on rapeseed. This study provides a valuable reference for exogenous Ca(L-asp)-NPs as new nano Ca supplements for plant growth.

Molecular Effects of Biogenic Zinc Nanoparticles on the Growth and Development of Brassica napus L. Revealed by Proteomics and Transcriptomics

Plants are indispensable on earth and their improvement in terms of food security is a need of time. The current study has been designed to investigate how biogenic zinc nanoparticles (Zn NPs) can improve the growth and development of Brassica napus L. In this study, Zn NPs were synthesized utilizing Mentha arvensis aqueous extracts, and their morphological and optical properties were assessed using UV-Visible spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The synthesized Zn NPs were irregular in shape, indicating aggregation in pattern, with an average particle size of 30 nm, while XRD analysis revealed the crystalline structure of nanoparticles. The growth and development of B. napus varieties (Faisal canola and Shiralee) were assessed after foliar treatments with different concentrations of biogenic Zn NPs. In B. napus varieties, exposure to 15 mg/L Zn NPs dramatically increased chlorophyll, carotenoid content, and biomass accumulation. Similarly, proteomic analyses, on the other hand, revealed that proteins associated with photosynthesis, transport, glycolysis, and stress response in both Brassica varieties were substantially altered. Such exposure to Zn NPs, differential expression of genes associated with photosynthesis, ribosome structural constituents, and oxidative stress response were considerably upregulated in B. napus var. (Faisal and Shiralee canola). The results of this study revealed that foliar applications of biogenic Zn NPs influence the transcriptome and protein profiling positively, therefore stimulating plant growth and development.

Influence of metallic, metallic oxide, and organic nanoparticles on plant physiology

Nanotechnology is a research area that has experienced tremendous development given the enormous potential of nanoparticles (NPs) to influence almost all industries and conventional processes. NPs have been extensively used in agriculture to improve plant physiology, production, and nutritional values of plant-based products. The large surface area and small size are some of the desired attributes for NPs that can substantially ameliorate plants' physiological processes, thereby improving crop production. Nevertheless, the results derived from such research have not always been positive as NPs have been shown, in some cases, to negatively affect plants due to their potentially toxic nature. These toxic effects depend upon the size, concentration, nature, zeta potential, and shape of nanoparticles, as well as the used plant species. The most common response of plants under NPs toxicity is the activation of antioxidant systems and the production of secondary metabolites. The mitigation of such NPs-induced stress highly varies depending on the amount of NPs applied to the plant growth stage and the environmental conditions. On the contrary, higher photosynthetic rates, higher chlorophyll, and proline content, improved homeostasis, hormonal balance, and nutrient assimilation are the favorable physiological changes after NPs applications. Alternatively, NPs do not always exhibit positive or negative impacts on plants, and no physiological influences are sometimes observed. Considering such diversity of responses after the use of NPs on plants, this review summarizes the progress made in nanotechnology on the influence of different NPs in plant physiology through the use of indexes like seed germination, root and shoot morphology, photosynthesis, and their impact when used as carriers of cell signaling molecules such as nitric oxide (NO). Understanding the intimate dynamics of nanoparticle toxicity in plants can prove to be fruitful for the development of areas like agronomy, horticulture, plant pathology, plant physiology, etc. That, in return, can assist to ensure agricultural sustainability. Similarly, this may also help to pave the way to combat the drastic climate change and satisfy growing food demands for the ever-increasing world population. Further studies on molecular and genetic levels can certainly broaden the current understanding of NPs-plant interactions and devise the respective mitigation strategies for environmental safety.

Zinc Oxide Nanoparticles Improve Pleioblastus pygmaeus Plant Tolerance to Arsenic and Mercury by Stimulating Antioxidant Defense and Reducing the Metal Accumulation and Translocation

The utilization of nanoparticles to potentially reduce toxicity from metals/metalloids in plants has increased in recent years, which can help them to achieve tolerance under the stressful conditions. An in vitro experiment was conducted to investigate five different levels of zinc oxide nanoparticles (ZnO-NPs; 0, 50, 100, 150, and 200 μM) both alone and in combination with 150 μM arsenic (As) and 150 μM mercury (Hg) in one-year-old Pleioblastus pygmaeus (Miq.) Nakai plants through four replications. The results demonstrated that As and Hg alone had damaging effects on the plant growth and development. However, the addition of various concentrations of ZnO-NPs led to increased antioxidant activity, proline (79%) content, glycine betaine (71%) content, tyrosine ammonia-lyase (43%) activity, phenylalanine ammonia-lyase (69%) activity, chlorophyll indices, and eventually plant biomass, while the lipoxygenase activity, electrolyte leakage, soluble protein, hydrogen peroxide content, and thiobarbituric acid reactive substances were reduced. We concluded that ZnO-NPs detoxified As and Hg toxicity in the plants through increasing antioxidant activity, reducing As and Hg accumulation, As and Hg translocation from roots to shoots, and adjusting stomatal closure. This detoxification was further confirmed by the reduction of the translocation factor of As and Hg and the enhancement of the tolerance index in combination with ZnO-NPs. However, there is a need for further investigation with different metals/metalloids.

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.

Green Synthesized Metal Oxide Nanoparticles Mediate Growth Regulation and Physiology of Crop Plants under Drought Stress

Metal oxide nanoparticles (MONPs) are regarded as critical tools for overcoming ongoing and prospective crop productivity challenges. MONPs with distinct physiochemical characteristics boost crop production and resistance to abiotic stresses such as drought. They have recently been used to improve plant growth, physiology, and yield of a variety of crops grown in drought-stressed settings. Additionally, they mitigate drought-induced reactive oxygen species (ROS) through the aggregation of osmolytes, which results in enhanced osmotic adaptation and crop water balance. These roles of MONPs are based on their physicochemical and biological features, foliar application method, and the applied MONPs concentrations. In this review, we focused on three important metal oxide nanoparticles that are widely used in agriculture: titanium dioxide (TiO2), zinc oxide (ZnO), and iron oxide (Fe3O4). The impacts of various MONPs forms, features, and dosages on plant growth and development under drought stress are summarized and discussed. Overall, this review will contribute to our present understanding of MONPs' effects on plants in alleviating drought stress in crop plants.

Synergistic Effects of Zinc Oxide Nanoparticles and Bacteria Reduce Heavy Metals Toxicity in Rice (Oryza sativa L.) Plant

Heavy metals (HMs) are toxic elements which contaminate the water bodies in developing countries because of their excessive discharge from industrial zones. Rice (Oryza sativa L) crops are submerged for a longer period of time in water, so irrigation with HMs polluted water possesses toxic effects on plant growth. This study was initiated to observe the synergistic effect of bacteria (Bacillus cereus and Lysinibacillus macroides) and zinc oxide nanoparticles (ZnO NPs) (5, 10, 15, 20 and 25 mg/L) on the rice that were grown in HMs contaminated water. Current findings have revealed that bacteria, along with ZnO NPs at lower concentration, showed maximum removal of HMs from polluted water at pH 8 (90 min) as compared with higher concentrations. Seeds primed with bacteria grown in HM polluted water containing ZnO NPs (5 mg/L) showed reduced uptake of HMs in root, shoot and leaf, thus resulting in increased plant growth. Furthermore, their combined effects also reduced the bioaccumulation index and metallothionine (MTs) content and enhanced the tolerance index of plants. This study suggested that synergistic treatment of bacteria with lower concentrations of ZnO NPs helped plants to reduce heavy metal toxicity, especially Pb and Cu, and enhanced plant growth.

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

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

Nano zinc elicited biochemical characterization, nutritional assessment, antioxidant enzymes and fatty acid profiling of rapeseed

The use of nanomaterials in agriculture is a current need and could be helpful in overcoming food security risks. Brassica napus L. is the third most important crop for edible oil, having double low unsaturated fatty acids. In the present study, we investigated the effects of green synthesized Zn NPs on biochemical effects, antioxidant enzymes, nutritional quality parameters and on the fatty acid profile of rapeseed (B. napus). Plant-mediated synthesis of zinc nanoparticles (Zn NPs) was carried out using Mentha arvensis L. leaf extract followed by characterization through ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-Ray (EDX), and X-Ray diffraction (XRD). NPs exhibited irregular shapes ranging in size from 30-70 nm and EDX analysis confirmed 96.08% of Zn in the sample. The investigated biochemical characterization (protein content, proline content, total soluble sugar (TSS), total flavonoid content (TFC), and total phenolic content (TPC) showed a substantial change on exposure to Zn NPs. A dose-dependent gradual increase was observed in the antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Oil and moisture contents dropped significantly from the control level in the rapeseed (B. napus) varieties. However, different trends in nutritional (Zn, Na+, K+) and fatty acid profiling of B. napus have been noted. This study demonstrates that Zn NPs have the potential to improve the biochemical, nutritional, antioxidant enzymes, and fatty acid profile of B. napus varieties.

Phytotoxic effect of silver nanoparticles on seed germination and growth of terrestrial plants

Silver nanoparticles (AgNP) exhibit size and concentration dependent toxicity to terrestrial plants, especially crops. AgNP exposure could decrease seed germination, inhibit seedling growth, affect mass and length of roots and shoots. The phytotoxic pathway has been partly understood. Silver (as element, ion or AgNP) accumulates in roots/leaves and triggers the defense mechanism at cellular and tissue levels, which alters metabolism, antioxidant activities and related proteomic expression. Botanical changes (either increase or decrease) in response to AgNP exposure include reactive oxygen species generation, superoxide dismutase activities, H₂O₂ level, total chlorophyll, proline, carotenoid, ascorbate and glutathione contents, etc. Such processes lead to abnormal morphological changes, suppression of photosynthesis and/or transpiration, and other symptoms. Although neutral or beneficial effects are also reported depending on plant species, adverse effects dominate in majority of the studies. More in depth research is needed to confidently draw any conclusions and to guide legislation and regulations.

Metallic nanoparticles influence the structure and function of the photosynthetic apparatus in plants

The applications of nanoparticles continue to expand into areas as diverse as medicine, bioremediation, cosmetics, pharmacology and various industries, including agri-food production. The widespread use of nanoparticles has generated concerns given the impact these nanoparticles - mostly metal-based such as CuO, Ag, Au, CeO₂, TiO₂, ZnO, Co, and Pt - could be having on plants. Some of the most studied variables are plant growth, development, production of biomass, and ultimately oxidative stress and photosynthesis. A systematic appraisal of information about the impact of nanoparticles on these processes is needed to enhance our understanding of the effects of metallic nanoparticles and oxides on the structure and function on the plant photosynthetic apparatus. Most nanoparticles studied, especially CuO and Ag, had a detrimental impact on the structure and function of the photosynthetic apparatus. Nanoparticles led to a decrease in concentration of photosynthetic pigments, especially chlorophyll, and disruption of grana and other malformations in chloroplasts. Regarding the functions of the photosynthetic apparatus, nanoparticles were associated with a decrease in the photosynthetic efficiency of photosystem II and decreased net photosynthesis. However, CeO₂ and TiO₂ nanoparticles may have a positive effect on photosynthetic efficiency, mainly due to an increase in electron flow between the photosystems II and I in the Hill reaction, as well as an increase in Rubisco activity in the Calvin and Benson cycle. Nevertheless, the underlying mechanisms are poorly understood. The future mechanistic work needs to be aimed at characterizing the enhancing effect of nanoparticles on the active generation of ATP and NADPH, carbon fixation and its incorporation into primary molecules such as photo-assimilates.