Synthesis and characterisation of metal nanoparticles and their effects on seed germination and seedling growth in commercially important Eruca sativa

Au-Based Nanoparticles Enhance Low Temperature Tolerance in Wheat by Regulating Some Physiological Parameters and Gene Expression

One of the key problems of biology is how plants adapt to unfavorable conditions, such as low temperatures. A special focus is placed on finding ways to increase tolerance in important agricultural crops like wheat. Au-based nanoparticles (Au-NPs) have been employed extensively in this area in recent years. Au-NPs can be produced fast and easily using low-cost chemical reagents. When employed in microdoses, Au-NPs are often non-toxic to plants, animals, and people. In addition, Au-NPs mainly have favorable impacts on plants. In this study, we investigated the effect of Au-NP seed nanopriming (diameter 15.3 nm, Au concentration 5-50 µg mL-1) on cold tolerance, as well as some physiological, biochemical and molecular parameters, of cold-sustainable wheat (Triticum aestivum L.) genotype Zlata. The treatment with Au-NPs improved tolerance to low temperatures in control conditions and after cold hardening. Au-NPs treatment boosted the intensity of growth processes, the quantity of photosynthetic pigments, sucrose in leaves, and the expressions of encoded RuBisCo and Wcor15 genes. The potential mechanisms of Au-NPs' influence on the cold tolerance of wheat varieties were considered.

Exposure of Caralluma tuberculata to biogenic selenium nanoparticles as in vitro rooting agent: Stimulates morpho-physiological and antioxidant defense system

The commercial-scale production of Caralluma tuberculata faces significant challenges due to lower seed viability and sluggish rate of root growth in natural conditions. To overcome these obstacles, using phyto-mediated selenium nanomaterials as an in vitro rooting agent in plant in vitro cultures is a promising approach to facilitate rapid propagation and enhance the production of valuable therapeutic compounds. This study aimed to investigate the impact of phytosynthesized selenium nanoparticles (SeNPs) on the morphological growth attributes, physiological status, and secondary metabolite fabrication in in vitro propagated Caralluma tuberculata. The results demonstrated that a lower dose of SeNPs (100 μg/L) along with plant growth regulators (IBA 1 mg/L) had an affirmative effect on growth parameters and promoted earliest root initiation (4.6±0.98 days), highest rooting frequency (68.21±5.12%), number of roots (6.3±1.8), maximum fresh weight (710±6.01 mg) and dry weight (549.89±6.77 mg). However, higher levels of SeNPs (200 and 400 μg/L) in the growth media proved detrimental to growth and development. Further, stress caused by SeNPs at 100 μg/L along with PGRs (IBA 1 mg/L) produced a higher level of total chlorophyll contents (32.66± 4.36 μg/ml), while cultures exposed to 200 μg/L SeNPs alone exhibited the maximum amount of proline contents (10.5± 1.32 μg/ml). Interestingly, exposure to 400 μg/L SeNPs induced a stress response in the cultures, leading to increased levels of total phenolic content (3.4 ± 0.052), total flavonoid content (1.8 ± 0.034), and antioxidant activity 82 ± 4.8%). Furthermore, the combination of 100 μg/L SeNPs and plant growth regulators (1 mg/L IBA) led to accelerated enzymatic antioxidant activities, including superoxide dismutase (SOD = 4.4 ± 0.067 U/mg), peroxidase dismutase (POD = 3.3 ± 0.043 U/mg), catalase (CAT = 2.8 ± 0.048 U/mg), and ascorbate peroxidase (APx = 1.6 ± 0.082 U/mg). This is the first report that highlights the efficacy of SeNPs in culture media and presents a promising approach for the commercial propagation of C. tuberculata with a strong antioxidant defense system in vitro.

Comparative study on the toxic effects of secondary nanoplastics from biodegradable and conventional plastics on Streptomyces coelicolor M145

Because of the excellent properties, plastics have been widely used in the past decades and caused serious environmental issues. As an excellent substitute for conventional plastics, the biodegradable plastics have attracted increasing attention. However, biodegradable plastics may produce more micro/nanoplastics in the short time compared with conventional plastics, and cause more serious ecological risks. In this study, the short-term toxicity of nanoplastics released from biodegradable and conventional plastics on Streptomyces coelicolor M145 was investigated. After 30 days of degradation, the biodegradable microplastics, polylactic acid (PLA) and polyhydroxyalkanoates (PHA) released more secondary nanoplastics than conventional microplastics, polystyrene (PS). After exposure, PLA and PHA nanoplastics showed significant toxicity to M145. The survival rate of M145 cells was 16.1% after treatment with PLA nanoplastics for 7 days (PLA-7). The toxicity of PHA was lower than that of PLA. This might have been due to the agglomeration of PHA nanoplastics in the solution. Compared with the controls, the PS secondary nanoplastics showed no significant toxicity to M145. After the treatment, the production of antibiotics, actinorhodin (ACT) and undecylprodigiosin (RED), significantly increased. The yields of ACT and RED reached their maximum values after treatment with PLA-7, which were 4.2-fold and 2.1-fold higher than those of the controls, respectively. The addition of biodegradable nanoplastics significantly increased the expression of these key pathway-specific regulatory genes, leading to increased antibiotic production. This study provides toxicological insights into the impacts of conventional and biodegradable microplastics on S. coelicolor.

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

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

Biosynthesized silver nanoparticles enhanced wheat resistance to Bipolaris sorokiniana

Agronomic crops can benefit from the application of nanoscale materials in order to control phytopathogens and improve plant growth. Bipolaris sorokiniana, a soil- and seed-borne fungus, causes severe yield losses in wheat. In order to determine the physio-chemical changes in wheat under biotic stress of B. sorokiniana, the current study aimed to synthesis silver nanoparticles (AgNPs) using Allium sativum bulb extract. Herein, we applied the silver nanoparticles (AgNPs) as a foliar spray on two wheat varieties (Pakistan-2013, and NARC-2011) at the concentrations of 10, 20, 30, and 40 mg/L to suppress B. sorokiniana. Among all the applied concentrations of AgNPs, the 40 mg/L concentration demonstrated the most effective outcome in reduction of the intensity of spot blotch and improved the morphological, physiological, biochemical parameters, as well as antioxidant activity in wheat plant. Foliar application of AgNPs at 40 mg/L Pakistan-2013 and NARC-2011 wheat varieties significantly increased chlorophyll a 84.8% and 53.4%, chlorophyll b 28.9% and 84.3%, total chlorophyll content 294.3% and 241.2%, membrane stability index 7.5% and 6.1%, relative water contents 25.4% and 10.5%, proline content 320.5% and 609.9%, and soluble sugar content 120% and 259.4%, respectively, compared to control and diseased plant. This is the first study provides important insights into the role of phyto-mediated AgNPs in increasing resistant of wheat infected with B. sorokiniana. These findings offers valuable new insights that may be useful for reducing disease incidence in wheat fields.

Multifaceted Role of Nanomaterials in Modulating In Vitro Seed Germination, Plant Morphogenesis, Metabolism and Genetic Engineering

The agricultural practices of breeding, farm management and cultivation have improved production, to a great extent, in order to meet the food demands of a growing population. However, the newer challenges of climate change, global warming, and nutritional quality improvement will have to be addressed under a new scenario. Plant biotechnology has emerged as a reliable tool for enhancing crop yields by protecting plants against insect pests and metabolic engineering through the addition of new genes and, to some extent, nutritional quality improvement. Plant tissue culture techniques have provided ways for the accelerated clonal multiplication of selected varieties with the enhanced production of value-added plant products to increase modern agriculture. The in vitro propagation method has appeared as a pre-eminent approach for the escalated production of healthy plants in relatively shorter durations, also circumventing seasonal effects. However, there are various kinds of factors that directly or indirectly affect the efficiency of in vitro regeneration like the concentration and combination of growth regulators, variety/genotype of the mother plant, explant type, age of seedlings and other nutritional factors, and elicitors. Nanotechnology as one of the latest and most advanced approaches in the material sciences, and can be considered to be very promising for the improvement of crop production. Nanomaterials have various kinds of properties because of their small size, such as an enhanced contact surface area, increased reactivity, stability, chemical composition, etc., which can be employed in plant sciences to alter the potential and performance of plants to improve tissue culture practices. Implementing nanomaterials with in vitro production procedures has been demonstrated to increase the shoot multiplication potential, stress adaptation and yield of plant-based products. However, nanotoxicity and biosafety issues are limitations, but there is evidence that implies the promotion and further exploration of nanoparticles in agriculture production. The incorporation of properly designed nanoparticles with tissue culture programs in a controlled manner can be assumed as a new pathway for sustainable agriculture development. The present review enlists different studies in which treatment with various nanoparticles influenced the growth and biochemical responses of seed germination, as well as the in vitro morphogenesis of many crop species. In addition, many studies suggest that nanoparticles can be useful as elicitors for elevating levels of important secondary metabolites in in vitro cultures. Recent advancements in this field also depict the suitability of nanoparticles as a promising carrier for gene transfer, which show better efficiency than traditional Agrobacterium-mediated delivery. This review comprehensively highlights different in vitro studies that will aid in identifying research gaps and provide future directions for unexplored areas of research in important crop species.

Gold nanoparticles as adaptogens increazing the freezing tolerance of wheat seedlings

The intensive development of nanotechnology led to the widespread application of various nanoparticles and nanomaterials. As a result, nanoparticles enter the environment and accumulate in ecosystems and living organisms. The consequences of possible impact of nanoparticles on living organisms are not obvious. Experimental data indicate that nanoparticles have both toxic and stimulating effects on organisms. In this study, we demonstrated for the first time that gold nanoparticles can act as adaptogens increasing plant freezing tolerance. Priming winter wheat (Triticum aestivum L., var. Moskovskaya 39, Poaceae) seeds for 1 day in solutions of gold nanoparticles (15-nm diameter, concentrations of 5, 10, 20, and 50 µg/ml) led to an increase in freezing tolerance of 7-day-old wheat seedlings. A relationship between an increase in wheat freezing tolerance and changes in some important indicators for its formation-growth intensity, the activity of the photosynthetic apparatus and oxidative processes, and the accumulation of soluble sugars in seedlings-was established. Assumptions on possible mechanisms of gold nanoparticles effects on plant freezing tolerance are discussed.

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.

Phytochemicals Mediated Synthesis of AuNPs from Citrullus colocynthis and Their Characterization

Engineered nanoparticles that have distinctive targeted characteristics with high potency are modernistic technological innovations. In the modern era of research, nanotechnology has assumed critical importance due to its vast applications in all fields of science. Biologically synthesized nanoparticles using plants are an alternative to conventional methods. In the present study, Citrullus colocynthis (bitter apple) was used for the synthesis of gold nanoparticles (AuNPs). UV-Vis's spectroscopy, XRD, SEM and FTIR were performed to confirm the formation of AuNPs. UV-Vis's spectra showed a characteristic peak at the range of 531.5-541.5 nm. XRD peaks at 2 θ = 38°, 44°, 64° and 77°, corresponding to 111, 200, 220 and 311 planes, confirmed the crystalline nature of AuNPs. Spherical AuNPs ranged mostly between 7 and 33 nm, and were measured using SEM. The FTIR analysis confirmed the presence of phytochemicals on the surface of AuNPs. Successful synthesis of AuNPs by seed extract of Citrullus colocynthis (bitter apple) as a capping and reducing agent represents the novelty of the present study.

Phytochemical mediated synthesis of silver nanoparticles and their antibacterial activity

In this present work, we described a bio-reduction method for the generation of silver nanoparticles (AgNPs) using aqueous leaf extract of Micrargeria wightii (M. wightii), which is a gifted alternative to other physicochemical routes. The prepared AgNPs were characterized by UV–visible spectroscopy (UV–vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (X-RD), Transmission Electron Microscopy (TEM) with EDX and Dynamic light scattering (DLS). UV–visible spectrum showed a characteristic absorption peak at 440 nm of synthesized AgNPs. FT-IR analysis confirmed the existence of plant metabolites, which are responsible for the reduction of Ag (I) ions into Ag (0) NPs. X-RD pattern studies confirm the presence of the pure face-centered cubiccrystalline nature of Ag. Energy-dispersive X-ray (E-DX) spectrum showed the elemental composition of synthesized nanoparticles. Furthermore, TEM images confirm the formation of spherical shaped nano-silver particles with sizes ranging from 30 to 70 nm and supported by particle size analyzer, Dynamic Light Scattering (DLS). Thus, the present investigation provides an easy, eco-friendly and straightforward route for the synthesis of the antibacterial agent against Bacillus subtilis subtilis and Pseudomonas aeruginosa, with 15 and 13 mm zone of inhibition (ZOI) respectively.

A review on in vivo and in vitro nanotoxicological studies in plants: A headlight for future targets

Owing to the unique properties and useful applications in numerous fields, nanomaterials (NMs) received a great attention. The mass production of NMs has raised major concern for the environment. Recently, some altered growth patterns in plants have been reported due to the plant-NMs interactions. However, for NMs safe applications in agriculture and medicine, a comprehensive understanding of bio-nano interactions is crucial. The main goal of this review article is to summarize the results of the toxicological studies that have shown the in vitro and in vivo interactions of NMs with plants. The toxicity mechanisms are briefly discussed in plants as the defense mechanism works to overcome the stress caused by NMs implications. Indeed, the impact of NMs on plants varies significantly with many factors including physicochemical properties of NMs, culture media, and plant species. To investigate the impacts, dose metrics is an important analysis for assaying toxicity and is discussed in the present article to broadly open up different aspects of nanotoxicological investigations. To access reliable quantification and measurement in laboratories, standardized methodologies are crucial for precise dose delivery of NMs to plants during exposure. Altogether, the information is significant to researchers to describe restrictions and future perspectives.

Synthesis of green and pure copper oxide nanoparticles using two plant resources via solid-state route and their phytotoxicity assessment

Among the conventional methods in synthesizing nanoparticles, the methods that use biological resources, as reducing and stabilizing agents, can be considered eco-friendly methods. In this study, the leaf tissue of green tea (Camellia sinensis L.) and lavender (Lavandula anguistifolia) were utilized by the solid-state method as a one-step and low-cost method for the biosynthesis of copper oxide nanoparticles (CuO NPs). The results of the X-ray Diffraction (XRD), field emission scanning electron spectroscopy (FESEM) and transmission electron microscopy (TEM) showed that lavender is more productive in the synthesis of pure and uniform CuO NPs (50 nm). Comparing biogenic synthesized CuO NPs with chemically synthesized CuO NPs in terms of induction of phytotoxicity, exposed in treatments with concentrations of 40, 400 and 4000 μg ml⁻¹, green CuO NPs had less inhibitory effects on the seed germination factors (i.e., germination percentage, germination rate, shoot and root length, etc.) of lettuce (Lactuca sativa L.), and tomato (Solanum lycopersicum L.) seeds. However, both green/chemically synthesized CuO NPs at their lowest concentrations (4 μg ml⁻¹), had an effective role in root and shoot expansion of lettuce and tomato seedlings.

Among the conventional methods in synthesizing nanoparticles, the methods that use biological resources, as reducing and stabilizing agents, can be considered eco-friendly methods.

Interactive Effect of Light and CdO Nanoparticles on Dodonaea viscosa Morphological, Antioxidant, and Phytochemical Properties

Cadmium nanoparticles (NPs) used in semiconducting devices are photosensitive and optically active. The objective of this study was to investigate the interactive effect of different spectral lights and CdO NPs on morphological, antioxidant, and phytochemical characteristics of Dodonaea viscosa. The plants were grown on media in the presence of green and chemically synthesized CdO NPs and under red, yellow, green, blue, and white light intensities. Results illustrated that plant morphological parameters changed in the presence of different spectral lights and NPs behaved differentially under different spectral lights. Fresh and dry weights of plants decreased in the presence of NPs in the media; however, the concentration and route of synthesis of NPs have a significant effect on these parameters. The same was observed in the case of shoot and root lengths; however, green synthesized NPs were found to be less toxic under different spectral lights. The total antixodant response increased under yellow, blue, and white lights, while the total reducing potential of plant extracts significantly varied depending upon the NP concentration and light spectrum. Different spectral lights significantly influenced the syntheses of phenolics and flavonoids under CdO NP stress and light regimes. It is concluded that toxicity of NPs also depends upon the wavelength of striking light that varies the morphological, biochemical, and antioxidative response of the plants. Furthermore, the white light might have synergistic effects of different wavelengths.

Green and Chemical Syntheses of CdO NPs: A Comparative Study for Yield Attributes, Biological Characteristics, and Toxicity Concerns

Metallic nanoparticles (NPs) have enormous applications due to their remarkable physical and chemical properties. The synthesis of NPs has been a matter of concern because chemical methods are toxic. On the contrary, biological methods are considered eco-friendly. To compare the toxicity and the environment-friendly nature of the synthesis methodologies, cadmium NPs were synthesized through chemical (Ch) (co-precipitation) and biological (plant extracts as reducing agent) methods. Cadmium nitrate was reduced with NaOH, while in the biological method, the Cd ions were reduced by Artemisia scoparia (As) and Cannabis sativa (Cs) extracts. X-ray diffraction (XRD) analysis confirmed the pure single-phase cubic structure of green and chemically synthesized CdO NPs except As-CdO NPs that were crystalline cum amorphous in nature. The size of nanoparticles was 84 nm (Cs-CdO NPs) and 42.2 nm (Ch-CdO NPs). The scanning electron microscope (SEM) images exhibited an irregular disklike morphology of nanoparticles that agglomerated more in the case of green synthesis. The antioxidant and antimicrobial potential of NPs revealed that chemically synthesized NPs have better antimicrobial capability, while the antioxidative activities were better for green-synthesized NPs. However, the low yield, high ion disassociation, and waste (unreacted metal) production in the green synthesis of CdO NPs increase the risk of contamination to biosphere. Both types of NPs did not affect the seed germination of Dodonaea viscosa. However, chemically synthesized NPs were less toxic on plant morphological response. The study concludes that the chemically synthesized CdO NPs have better morphology, significant antimicrobial activity, and less toxicity to plant species compared to green-synthesized NPs. Moreover, during the green synthesis, unreacted metals are drained, which causes contamination to the ecosystem.

Comparative Analysis of the Effect of Inorganic and Organic Chemicals with Silver Nanoparticles on Soybean under Flooding Stress

Extensive utilization of silver nanoparticles (NPs) in agricultural products results in their interaction with other chemicals in the environment. To study the combined effects of silver NPs with nicotinic acid and potassium nitrate (KNO3), a gel-free/label-free proteomic technique was used. Root length/weight and hypocotyl length/weight of soybean were enhanced by silver NPs mixed with nicotinic acid and KNO3. Out of a total 6340 identified proteins, 351 proteins were significantly changed, out of which 247 and 104 proteins increased and decreased, respectively. Differentially changed proteins were predominantly associated with protein degradation and synthesis according to the functional categorization. Protein-degradation-related proteins mainly consisted of the proteasome degradation pathway. The cell death was significantly higher in the root tips of soybean under the combined treatment compared to flooding stress. Accumulation of calnexin/calreticulin and glycoproteins was significantly increased under flooding with silver NPs, nicotinic acid, and KNO3. Growth of soybean seedlings with silver NPs, nicotinic acid, and KNO3 was improved under flooding stress. These results suggest that the combined mixture of silver NPs, nicotinic acid, and KNO3 causes positive effects on soybean seedling by regulating the protein quality control for the mis-folded proteins in the endoplasmic reticulum. Therefore, it might improve the growth of soybean under flooding stress.

Silver nanoparticles and silver salt (AgNO3) elicits morphogenic and biochemical variations in callus cultures of sugarcane

The research work was arranged to check the role of AgNPs and silver ions on callus cells of sugarcane (Saccharum spp. cv CP-77,400). AgNPs were synthesized chemically and characterized by UV-Vis spectra, XRD and SEM. AgNPs and silver ions were applied in various concentrations (0, 20, 40, 60 ppm) to sugarcane calli and the induced stress was characterized by studying various morphological and biochemical parameters. AgNPs and silver ions treatments produced high levels of malondialdehyde, proline, proteins, TP and TF contents. Similarly, CAT, SOD and POX activity was also significant in both treatments. The lower concentration of AgNPs and silver ions (20 ppm) provided maximum intracellular GSH level. This work mainly showed effects of AgNPs and silver ions on sugarcane calli in terms of morphological aberrations and cell membrane damage due to severe oxidative stress and production of enhanced levels of enzymatic and non-enzymatic antioxidants as self-defence to tolerate oxidative stress by scavenging reactive oxygen species. These preliminary findings will provide the way to study ecotoxicity mechanism of the metal ions and NPs in medicine industry and in vitro toxicity research. Furthermore, silver ions alone and their chemically synthesised AgNPs can be used for various biomedical applications in future.

Biogenic zinc oxide nanoparticles-enhanced biosynthesis of lignans and neolignans in cell suspension cultures of Linum usitatissimum L

Zinc oxide nanoparticles (NPs) have emerged as a novel elicitor for enhanced biosynthesis of secondary metabolites in in vitro plant cell cultures. The current study was aimed to explore elicitation abilities of ZnO-NPs for enhanced accumulation of lignans and neolignans in cell cultures of Linum usitatissimum. We optimized concentration of zinc oxide NPs before carrying out a full-fledged experiment. Subsequently, an optimum dose of 100 mg/l was introduced into the culture medium on day 0, days 0 and 15, and finally days 0 and 25. We observed that repeated elicitation stimulated various parameters and physiological responses in Linum usitatissimum cell cultures than one-time elicitation. Repeated elicitation of cell cultures on day 0 and 15 resulted in highest fresh weight (412.16 g/l) and lignans production (secoisolariciresinol diglucoside 284.12 mg/l: lariciresinol diglucoside 86.97 mg/l). Contrarily, repeated elicitation on day 0 and 25 resulted in highest DW (13.53 g/l), total phenolic production (537.44 mg/l), total flavonoid production (123.83 mg/l) and neolignans production (dehydrodiconiferyl alcohol glucoside 493.28 mg/l: guaiacylglycerol-β-coniferyl alcohol ether glucoside 307.69 mg/l). Enhancement in plant growth and secondary metabolites accumulation was several fold higher than controls. Furthermore, a linear relationship existed between total phenolic and flavonoid contents which in turn was correlated with higher antioxidant activities.

Magnesium oxide nanoparticles and thidiazuron enhance lead phytoaccumulation and antioxidative response in Raphanus sativus L

An in vitro study was conducted to evaluate the effects of thidiazuron (TDZ) growth regulator and magnesium oxide (MgO) nanoparticles on radish (Raphanus sativus L.) under lead (Pb) stress. Effects of TDZ and MgO on seed germination, growth, biomass, total phenolics and flavonoids, antioxidant potential, and Pb phytoaccumulation in different plant parts were assessed. Nanoparticles of MgO were synthesized with leaf extract of Sageretia thea (Osbeck) plant. Thidiazuron and MgO nanoparticles were added to growth media in individual and in combinations. Lead (50 mg L^-1) was added to growth media. Thidiazuron and MgO nanoparticles increased plant growth, phenolic and flavonoid contents, free radical scavenging activity, and lead phytoaccumulation. The increase was highly significant in TDZ and MgO nanoparticle combination treatments (T5, T6). Treatment (T6) showed a sixfold increase in Pb accumulation (1721.73 ± 17.4 μg g^-1 dry biomass) as compared to control (274.29 ± 4.23 μg^-1g^-1). Total phenolic and dry biomass showed significantly positive correlation in leaves (R² = 0.73), stem (R² = 0.58), and roots (R² = 0.72). The correlation of Pb accumulation and phenolic contents was significantly positive in root (R² = 0.80), stem (R² = 0.92), and leaves (R² = 0.69). Flavonoid showed a positive correlation with dry biomass and Pb accumulation. Antioxidant activity was highly increased in leaves followed by stem and root. Findings show that TDZ in combination with MgO nanoparticles can play a significant role in secondary metabolite production and Pb phytoaccumulation.

Ecotoxicology of silver nanoparticles and their derivatives introduced in soil with or without sewage sludge: A review of effects on microorganisms, plants and animals

Silver nanoparticles (AgNPs) are widely incorporated in many products, partly due to their antimicrobial properties. The subsequent discharge of this form of silver into wastewater leads to an accumulation of silver species (AgNPs and derivatives resulting from their chemical transformation), in sewage sludge. As a result of the land application of sewage sludge for agricultural or remediation purposes, soils are the primary receiver media of silver contamination. Research on the long-term impact of AgNPs on the environment is ongoing, and this paper is the first review that summarizes the existing state of scientific knowledge on the potential impact of silver species introduced into the soil via sewage sludge, from microorganisms to earthworms and plants. Silver species can easily enter cells through biological membranes and affect the physiology of organisms, resulting in toxic effects. In soils, exposure to AgNPs may change microbial biomass and diversity, decrease plant growth and inhibit soil invertebrate reproduction. Physiological, biochemical and molecular effects have been documented in various soil organisms and microorganisms. Negative effects on organisms of the dominant form of silver in sewage sludge, silver sulfide (Ag₂S), have been observed, although these effects are attenuated compared to the effects of metallic AgNPs. However, silver toxicity is complex to evaluate and much remains unknown about the ecotoxicology of silver species in soils, especially with respect to the possibility of transfer along the trophic chain via accumulation in plant and animal tissues. Critical points related to the hazards associated with the presence of silver species in the environment are described, and important issues concerning the ecotoxicity of sewage sludge applied to soil are discussed to highlight gaps in existing scientific knowledge and essential research directions for improving risk assessment.

Effect of green synthesised silver nanoparticles on morphogenic and biochemical variations in callus cultures of kinnow mandarin (Citrus reticulata L.)

Citrus reticulata is economically important tree fruit crop in Pakistan, fortified with various nutrients and minerals including Vitamin C and secondary metabolites. Nanotechnology is a twenty‐first century science and deals with production of minute particles termed as nanoparticles. In present study, silver nanoparticles (AgNPs) were synthesised through green method by utilising leaves of Olea europea as main reducing and capping agent. The synthesised AgNPs were characterised through UV visible spectroscopy, SEM, and energy dispersive X‐ray. Furthermore, different concentrations of AgNPs (10, 20, 30 ppm) in combination with Thidiazuron (0.5, 1.0 mg/l) were added onto MS medium to study development and secondary metabolites production in callus culture of C. reticulata . Callus induction percentage (96%) was more in 20 ppm AgNPs and 1 mg/l TDZ concentration. Moreover, high total phenolic, flavonoid contents, and antioxidant activity was observed in 20 ppm AgNPs combined with 0.5 and 1 mg/l TDZ. Enzymatic components (SOD, POD and CAT) were increased in MS medium augmented with 30 ppm AgNPs and TDZ. The total protein content (TPC) was significant in callus cultures treated with TDZ only. This study provides the first evidence of green synthesised AgNPs on callus culture developments and further quantification of biochemical profiling in C. reticula.

Modulation of callus growth and secondary metabolites in different Thymus species and Zataria multiflora micropropagated under ZnO nanoparticles stress

Thymus species are aromatic plants with diverse applications in food industries and medicine. This study was conducted to evaluate the potential effect of ZnO nanoparticles (NPs) on callus proliferation and thymol and carvacrol production in three Thymus species, that is, T. vulgaris, T. daenensis, and T. kotschyanus, and Zataria multiflora. For this purpose, callus induction was performed on Murashige and Skoog (MS) medium containing different plant growth regulators (PGRs). After optimization of callus growth, the effects of different concentrations of ZnO NPs (100 and 150 mg L^-1 ) were investigated. MS containing 2 mg L^-1 of 2, 4-dichlorophenoxy acetic acid (2,4-D) and 1 mg L^-1 of kinetin (Kin) revealed significantly highest fresh weight (0.18 g) of callus in T. kotschyanus. Callus growth rate (0.079 mm day^-1 ) was found highest in T. vulgaris under similar conditions. Moreover, highest callus induction (92.50%) was achieved by T. kotschyanus in MS containing 2.5 mg L^-1 of 2,4-D. Regarding the highest content of thymol (22.8 mg L^-1 ) and carvacrol (0.68 mg L^-1 ) evaluated by high-performance liquid chromatography, best results were achieved under 150 mg L^-1 of ZnO NPs in T. kotschyanus and T. daenesis, respectively. This is simple and cost-effective method to be applied on industrial level for production of enhanced secondary metabolites content.

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.

Toxicity of ZnSe nanoparticles to Lemna minor: Evaluation of biological responses

A clear consequence of the increasing application of nanotechnology is its adverse effect on the environment. Semiconductor nanoparticles are among engineered nanomaterials that have been considered recently for their specific characteristics. In the present work, zinc selenide nanoparticles (ZnSe NPs) were synthesized and characterized by XRD, TEM, DLS and SEM. Biological aspects related to the impact of nanoparticles and Zn²⁺ ions were analyzed on the aquatic higher plant Lemna minor. The localization of ZnSe NPs in the root cells of L. minor was determined by TEM and fluorescence microscopy. Then, the entrance of ZnSe NPs into the plant cells was evaluated by a range of biological tests. The outcomes revealed that both the NPs and the ionic forms noticeably poisoned L. minor. In one hand, growth parameters and physiological indices such as photosynthetic pigments content were decreased. On the other hand, the activities of some antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)), as well as the contents of nonenzymatic antioxidants (phenols and flavonoids) were elevated. Taken together, high concentration of ZnSe NPs and Zn²⁺ triggered phytotoxicity which in turn provoked the plants' defense system. The changes in antioxidant activities confirmed a higher toxicity by Zn²⁺ ions in comparison with ZnSe NPs. It means that the considered ions are more hazardous to the living organisms than the nanoparticles.

Seed germination and biochemical profile of Citrus reticulata (Kinnow) exposed to green synthesised silver nanoparticles

The biosynthesis of silver nanoparticles (AgNPs) is substantial for its applications in different fields. The Moringa oleifera leaves were used as reducing and stabilising agent for the biosynthesis of AgNPs. The synthesised AgNPs were characterised through UV-visible spectroscopy, zeta analyser, scanning electron microscopy (SEM) and energy dispersive Xray (EDX). In this study, effects of the synthesised AgNPs were also evaluated on nucellus tissues germination frequency and biochemical parameters of plant tissues. Nucellus tissues of Citrus reticulata were inoculated on MS medium supplemented with 10, 20, 30 and 40 µg/ml suspension of the synthesised AgNPs. Green synthesised AgNPs enhanced the in vitro germination because of low toxicity and nonfriendly issues. Significant results were obtained for germination parameters i.e. root and shoot length and seedling vigour index in response to 30 µg/ml suspension of green synthesised AgNPs. The 30 µ/ml suspension of AgNPs also enhanced antioxidant activity (41%) and SOD activity (0.36 nM/min/mg FW) while total phenolic content (4.7 µg/mg FW) and total flavonoid content (1.1 µg/mg FW) was significantly high when MS medium was fortified with 40 µg/ml suspension of the synthesised AgNPs. The content of total protein was significant (558 µg/BSA Eq/mg FW) in control plantlets as compared to the other treatments.

In vitro germination and biochemical profiling of citrus reticulata in response to green synthesised zinc and copper nanoparticles

Green synthesis of nanoparticles by using plants is an emerging class of nanobiotechnology. It revolutionizes all the fields of nanobiotechnology by synthesizing chemical‐free nanoparticles for various purposes. In the present study, zinc and copper nanoparticles were synthesized by using the white leaves of Allium cepa and further characterized through Zeta analyzer and Scanning electron microscopy. Zeta analyzer elucidated that zinc nanoparticles ranged from 8‐32 nm while copper nanoparticles ranged from 15‐30 nm. Scanning electron microscopy clarified that zinc nanoparticles were irregular while copper nanoparticles were spherical in shape. The effects of green synthesized nanoparticles were evaluated on the germination frequency and biochemical parameters of plant tissues. The nucellus tissues were inoculated on Murashige and Skoog (MS) medium augmented with 30 µg/ml suspension of zinc and copper nanoparticles. Green synthesized nanoparticles enhanced the in vitro germination parameters because of their low toxicity and high efficacy. Significant results were obtained for germination parameters in response to the applications of zinc nanoparticles as compared to copper nanoparticles. These nanoparticles could also induce stress in plantlets by manipulating the endogenous mechanism as a result various defence compounds are produced which have potential in treating various human ailments. Copper nanoparticles showed higher toxicity as compared to zinc nanoparticles and triggered the production of antioxidative enzymes and non‐ enzymatic compounds.

In vitro seed germination and biochemical profiling of Artemisia absinthium exposed to various metallic nanoparticles

In the recent years, nanotechnology has attained much attention in the every field of science. The synthesis, characterisation and applications of metallic nanoparticles (MNPs) have become an important branch of nanotechnology. In the current study, MNPs were synthesised through polyols process and applied in vitro to study their effect on medicinally important plant : Artemisia absinthium. The current study strives to check the effect of MNPs, i.e., Ag, Cu and Au on seed germination, root and shoot length, seedling vigour index (SVI) and biochemical profiling in A. absinthium. The seeds were inoculated on MS medium supplemented with various combinations of MNPs suspension. The seed germination was greatly influenced upon the application of MNPs and was recorded highest for the silver nanoparticles (AgNPs) suspensions. The best result for seed germination (98.6%) was obtained in MS medium supplemented with AgNPs as compared to control (92.9%) and other nanoparticles, i.e., copper (69.6%) and gold (56.5%), respectively, after 35 days of inoculation. Significant results were obtained for root length, shoot length and SVI in response to application of AgNPs as compared to copper nanoparticles (CuNPs) and gold nanoparticles (AuNPs). These nanoparticles (NPs) could induce stress in plants by deploying the endogenous mechanism. In response to these stresses, plants produce various defence compounds. Total phenolic content (TPC) and total flavonoid content (TFC) were significant in the MS medium supplemented with AgNPs as compared to other NPs, while DPPH radical scavenging assay (RSA) was highest in AuNPs treated plantlets. The MNPs showed higher toxicity level and enhanced secondary metabolites production, total phenolic content, total flavonoid content, antioxidant activity, superoxide dismutase (SOD) activity and total protein content.

Effects of bimetallic nanoparticles on seed germination frequency and biochemical characterisation of Eruca sativa

In the modern era of science and technology, nanotechnology is becoming popular science field because materials at nanoscale contain improved physical, chemical and biological properties. This study aimed to explore the capacity of bimetallic nanoparticle alloys of silver (Ag), copper (Cu), gold (Au) in different ratios to evaluate the effects on medicinally important plant Eruca sativa. Biochemical parameters of Eruca sativa were studied by applying bimetallic alloy nanoparticles. Seeds of Eruca sativa were germinated on Murashige and Skoog medium with various combinations of nanoparticles suspension employed in concentration of (30 µg/ml). Bimetallic alloys were considered as a stress inducing factor in plants while studying the phytotoxicity. Many secondary metabolites were released because defensive mechanism of plants was active in response to stress. Such secondary metabolites produced in medicinal plants have a great capability in treating the human diseases. In the authors' study, nanoparticles of small size and of high toxicity effect produced more secondary metabolites like total protein content, total flavonoids and total phenolic content.

Effect of ZnO Nanoparticles on Brassica nigra Seedlings and Stem Explants: Growth Dynamics and Antioxidative Response

Nanoparticles (NPs) have diverse properties when compared to respective chemicals due to their structure, surface to volume ratio, morphology, and reactivity. Toxicological effects of metallic NPs on organisms including plants have been reported. However, to the best of our knowledge, there is still not any report on the effect of NPs on in vitro culture of plant explants. In this study, ZnO NPs concentration ranging from 500 to 1500 mg/L adversely affects the Brassica nigra seed germination and seedling growth and also lead to an increase in the antioxidative activities and non-enzymatic antioxidants. While, culturing the stem explants of B. nigra on Murashige and Skoog (MS) medium at lower concentration of ZnO NPs (1-20 mg/L) resulted in the production of white thin roots with thick root hairs. At 10 mg/L ZnO NPs, shoots emergence is also observed. The developed calli/roots showed 79% DPPH (2,2-diphenyl-1-picryl hydrazyl) radical scavenging activity at 10 mg/L. The total antioxidant and reducing power potential also significantly affected in presence of ZnO NPs. Moreover, an increase in non-enzymatic antioxidative molecules, phenolics (up to 0.15 μg GAE/mg FW) and flavonoids (up to 0.22 μg QE/mg FW), depending on NPs concentration is also observed. We conclude that ZnO NPs may induce roots from explants cultured on appropriate medium that can be used for production of valuable secondary metabolites.