Metal and metal oxide nanoparticles-induced reactive oxygen species: Phytotoxicity and detoxification mechanisms in plant cell.

Nanotechnology is advancing rapidly in this century and the industrial use of nanoparticles for new applications in the modernization of different industries such as agriculture, electronic, food, energy, environment, healthcare and medicine is growing exponentially. Despite applications of several nanoparticles in different industries, they show harmful effects on biological systems, especially in plants. Various mechanisms for the toxic effects of nanoparticles have already been proposed; however, elevated levels of reactive oxygen species (ROS) molecules including radicals [(e.g., superoxide (O2•‒), peroxyl (HOO•), and hydroxyl (HO•) and non-radicals [(e.g., hydrogen peroxide (H2O2) and singlet oxygen (1O2) is more important. Excessive production/and accumulation of ROS in cells and subsequent induction of oxidative stress disrupts the normal functioning of physiological processes and cellular redox reactions. Some of the consequences of ROS overproduction include peroxidation of lipids, changes in protein structure, DNA strand breaks, mitochondrial damage, and cell death. Key enzymatic antioxidants with ROS scavenging ability comprised of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and glutathione reductase (GR), and non-enzymatic antioxidant systems including alpha-tocopherol, flavonoids, phenolic compounds, carotenoids, ascorbate, and glutathione play vital role in detoxification and maintaining plant health by balancing redox reactions and reducing the level of ROS. This review provides compelling evidence that phytotoxicity of nanoparticles, is mainly caused by overproduction of ROS after exposure. In addition, the present review also summarizes the intrinsic detoxification mechanisms in plants in response to nanoparticles accumulation within plant cells.

The role of reduced graphene oxide on mitigation of lead phytotoxicity in Triticum aestivum L.plants at morphological and physiological levels.

Rapid global industrialization and an increase in population have enhanced the risk of heavy metals accumulation in plant bodies to disrupt the morphological, biochemical, and physiological processes of plants. To cope with this situation, reduced graphene oxide (rGO) NPs were used first time to mitigate abiotic stresses caused in plant. In this study, rGO NPs were synthesized and reduced with Tecoma stans plant leave extract through modified Hummer's methods. The well prepared rGO NPs were characterized by ultra-violet visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential, and scanning electron microscopy (SEM). However, pot experiment was conducted with four different concentrations (15, 30, 60, 120 mg/L) of rGO NPs and three different concentrations (300, 500,700 mg/L) of lead (Pb) stress were applied. To observe the mitigative effects of rGO NPs, 30 mg/L of rGO NPs and 700 mg/L of Pb were used in combination. Changes in morphological and biochemical characteristics of wheat plants were observed for both Pb stress and rGO NPs treatments. Pb was found to inhibit the morphological and biochemical characteristics of plants. rGO NPs alone as well as in combination with Pb was found to increase the chlorophyll content of wheat plants. Under Pb stress conditions and rGO NPs treatments, antioxidant enzyme activities like ascorbate peroxidases (APX), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were observed. Current findings revealed that greenly reduced graphene oxide NPs can effectively promote growth in wheat plants under Pb stress by elevating chlorophyll content of leaves, reducing the Pb uptake, and suppressing ROS produced due to Pb toxicity.

Investigation of physio-mechanical, antioxidant and antimicrobial properties of starch-zinc oxide nanoparticles active films reinforced with Ferula gummosa Boiss essential oil.

The production of surface compounds coated with active substances has gained significant attention in recent years. This study investigated the physical, mechanical, antioxidant, and antimicrobial properties of a composite made of starch and zinc oxide nanoparticles (ZnO NPs) containing various concentrations of Ferula gummosa essential oil (0.5%, 1%, and 1.5%). The addition of ZnO NPs improved the thickness, mechanical and microbial properties, and reduced the water vapor permeability of the starch active film. The addition of F. gummosa essential oil to the starch nanocomposite decreased the water vapor permeability from 6.25 to 5.63 g mm-2 d-1 kPa-1, but this decrease was significant only at the concentration of 1.5% of essential oils (p < 0.05). Adding 1.5% of F. gummosa essential oil to starch nanocomposite led to a decrease in Tensile Strength value, while an increase in Elongation at Break values was observed. The results of the antimicrobial activity of the nanocomposite revealed that the pure starch film did not show any lack of growth zone. The addition of ZnO NPs to the starch matrix resulted in antimicrobial activity on both studied bacteria (Staphylococcus aureus and Escherichia coli). The highest antimicrobial activity was observed in the starch/ZnO NPs film containing 1.5% essential oil with an inhibition zone of 340 mm2 on S. aureus. Antioxidant activity increased significantly with increasing concentration of F. gummosa essential oil (P < 0.05). The film containing 1.5% essential oil had the highest (50.5%) antioxidant activity. Coating also improved the chemical characteristics of fish fillet. In conclusion, the starch nanocomposite containing ZnO NPs and F. gummosa essential oil has the potential to be used in the aquatic packaging industry.

Carnauba wax-based edible coatings retain quality enhancement of orange (Citrus sinensis cv. Moro) fruits during storage.

Fruit coatings serve a dual purpose in preserving the quality of fruits. Not only do they act as a barrier against water evaporation and fungal infiltration, but they also enhance the fruit's visual appeal in the market. Yet, their influence on the fruit's quality components, which play a crucial role in determining its nutritional value, taste, and overall flavor, has remained relatively unexplored. This study aimed to evaluate the effects of carnauba wax coating on the quality of Moro oranges during storage. The selected fruits were meticulously chosen for uniformity in size. The experiment involved applying carnauba wax, a commonly used type among local producers, at four different concentrations: 0%, 0.5%, 1%, and 1.5%. These treatments were applied during various storage periods, including immediately after fruits were harvested and after 40 and 80 days. Following the application of these treatments, the oranges were stored in a controlled environment (morgue) at a temperature of 4 ± 1 °C. Subsequently, several physicochemical parameters of both the fruit flesh and skin were examined. The results unveiled a decline in the overall ascorbic acid content of the fruits. In terms of phenol content, a general decreasing trend was observed after harvesting. At each sampling interval during storage, the phenol content in uncoated fruits consistently exceeded that of their waxed counterparts. Significant reduction in fruit weight was observed throughout the storage period. Both vitamin C and total acidity levels in the fruit exhibited decreases during the storage period. As time passed, fruit firmness gradually declined, while fruit decay increased during the 40- and 80-day storage periods for untreated Moro oranges. The anthocyanin content showed an increasing trend. The study also unveiled a decline in the antioxidant capacity of citrus fruits during storage. Strong significant positive correlations were observed between total phenol content and key parameters, such as antioxidant activity (0.941**), MDA (0.364*), vitamin C content, and total carbohydrate content (0.475**). Skin radiance showed a perfect correlation with chroma and hue (1.000**). Principal component analysis revealed that the first principal component accounted for 34.27% of the total variance, out of a total of five principal components that explained 77.14% of the variance. Through cluster analysis, the variables were categorized into three distinct groups; one associated with weight loss and another with ion leakage. Considering these findings, carnauba wax-based coating emerges as a promising solution for preserving Moro oranges. It effectively mitigates fruit weight loss and helps maintain fruit firmness during storage, making it a valuable tool for fruit preservation.

Development and characterization of biogenic copper oxide nanoparticles, with an exploration of their antibacterial and antioxidant potential.

This study outlines the synthesis of biogenic copper oxide nanoparticles (CuONPs) using an extract derived from Cassia fistula Linn (Cf) leaves through a green synthesis approach. Characterization of the synthesized CfBio-CuONPs was carried out using UV- VIS, FTIR, DLS, XRD, and TEM studies. The CfBio-CuONPs exhibited a prominent peak at 272 nm in UV-VIS spectroscopy, and XRD measurements confirmed their crystalline nature. The FTIR spectrum of CfBio-CuONPs revealed the presence of functional groups such as O-H and aromatic groups. TEM analysis confirmed that the CfBio-CuONPs were predominantly spherical with diameters ranging from 15 to 25 nm. Subsequently, the antibacterial potential of CfBio-CuONPs was evaluated against four pathogenic bacteria, including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Bacillus subtilis. Among these, B. subtilis exhibited the highest zone of inhibition (26.93 ± 2.01 mm), followed by E. coli (24.25 ± 1.04 mm), P. aeruginosa (23.98 ± 0.97 mm), and S. epidermidis (22.97 ± 1.20 mm). CfBio-CuONPs demonstrated maximum antioxidant activity (78 ± 1.54%) at a dose-dependent concentration of 2000 µg/ml. Furthermore, in vitro toxicity assessment using the toxtrak test indicated that CfBio-CuONPs exhibited a significantly stronger toxic effect value/PI against E. coli (93.52%) compared to P. aeruginosa (92.65%), B. subtilis (91.25%), and S. epidermidis (82.89%). These results underscore the notable toxicity of CfBio-CuONPs against E. coli, surpassing that against other bacteria and conventional antibiotics. This study highlights the potential utility of CfBio-CuONPs for eradicating pathogenic microorganisms and suggests potential implications for ecotoxicology. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03869-5.

Quantification of fatty acids in seed oil and important bioactive compounds in Iranian Rosa canina L. ecotypes for potential cosmetic and medicinal uses.

Rosa canina L. (Rosaceae), commonly known as the rose hip, is originated from Europe, Africa, and Asia with a long history in medicinal applications. This study aimed to analyze the morphological traits, fatty acids profile, and content of phenolic compounds, anthocyanins, vitamin C, total carotenoid, total phenol, total flavonoid, and antioxidant activity of the fruits of eleven Iranian R. canina ecotypes (RCEs). The highest coefficient of variation was obtained in 1000 seed weight (46.57%). The seed oil varied from 8.08 ± 0.17% to 16.91 ± 0.35%. Linoleic (35.41 ± 0.78% to 49.59 ± 0.96%) and eicosanoic (17.67 ± 0.06% to 25.36 ± 0.54%) acids were the predominant fatty acids in the studied samples. The anthocyanin content in the fruits was ranged from 0.98 ± 0.03 to 4.41 ± 0.04 mg cyanidin 3-glucoside/100 g of dry weight (mg C3G/100 g DW). The high content of vitamin C (103.51 ± 1.24-419.70 ± 3.12 mg/100 g DW), total carotenoid (111.22 ± 0.78-206.98 ± 1.25 mg ß-carotene equivalents per g of dry weight (mg ß-CARE/g DW)), total phenol (52.87 ± 0.82-104.52 ± 0.23 mg GAE/g DW), and total flavonoid (14.20 ± 0.12-25.18 ± 0.47 mg RE/g DW) were observed in the studied samples. Catechin (20.42 ± 0.47-19.22 ± 0.13 µg/g DW) was the major phenolic compound. The high antioxidant activity in the fruits of the plant was recorded in the studied RCEs (IC50 = 12.54 ± 0.18-26.33 ± 0.13 µg/ml). A significant correlation between some phytochemical compounds (dependent variable) and morphological features (independent variable) was found. Based on our findings, the fruit of the studied ecotypes can be used for future breeding programs and drug development.

Morpho-physiological growth performance and anti-oxidative capabilities of Acacia jacquemontii and Acacia nilotica upon exposure to Co3O4 Nbs in lead-contaminated soil.

Immense crowd of heavy metal in cultivated land is evolving as a global concern as a result of boosted level of soil toxicity. Amongst various metals, Lead (Pb) contamination has become alarming for plant and human heath through ingesting of polluted soils and food crops. To counterfeit this, a nanotechnological neutralizer effective in form of soiling of cobalt oxide Co3O4 Nbs to Acacia jacquemontii and Acacia nilotica with various meditations as 25, 50, 75 and 100 ppm). A Substantial result was observed on growth of plants but premium results were got by applications of cobalt oxide Nbs at 75 ppm. By this means, enhanced root length (39%), fresh weight (32%), shoot length (58%), as well as dry weight (28%) in selected Acacia species compared to control. Chlrophy contents in A. jacquemontii were estimated to be 0.23, 2.73 and 3.19 mg/L with treated with different concentrations of cobalt Nbs while in A. nilotica, the contents were 0.51, 2.93 and 3.12 mg/L respectively on same concentration. The atomic absorption (AAS), antioxidant activity and defendable positive comeback by using Co3O4 Nbs. Hence, the greenly synthesized Co3O4 Nbs counter acts lead toxicity to override and preserving the growth of plant. Such nanotechnological kits can consequently enhance the alternative system to stunned toxicity for distinguish the yield demand end to end with the progress of agronomic management approaches.

Application of guar (Cyamopsis tetragonoloba L.) gum in food technologies: A review of properties and mechanisms of action.

With the world continuing to push toward modernization and the consumption of processed foods growing at an exponential rate, the demand for texturizing agents and natural additives has also risen as a result. It has become increasingly common to use thickening agents in food products to modify their rheological and textural properties and enhance their quality characteristics. They can be divided into (1) animal derived (chitosan and isinglass), (2) fermentation produced (xanthan and curdlan), (3) plant fragments (pectin and cellulose), (4) seaweed extracts (agar and alginate), and (5) seed flours (guar gum and locust bean gum). The primary functions of these materials are to improve moisture binding capacity, modify structural properties, and alter flow behavior. In addition, some have another responsibility in the food sector, such as the main ingredient in the delivery systems (encapsulation) and nanocomposites. A galactomannan polysaccharide extracted from guar beans (Cyamopsis tetragonolobus), known as guar gum (GG), is one of them, which has a wide range of utilities and possesses popularity among scientists and consumers. In the world of modernization, GG has found its way into numerous industries for use in food, cosmetics, pharmaceuticals, textiles, and explosives. Due to its ability to form hydrogen bonds with water molecules, it imparts significant thickening, gelling, and binding properties to the solution as well as increases its viscosity. Therefore, this study is aimed to investigate the characteristics, mechanisms, and applications of GG in different food technologies.

Morphological diversity, phenolic acids, and antioxidant properties in eryngo (Eryngium caucasicum Trautv): Selection of superior populations for agri-food industry.

Eryngo (Eryngium caucasicum Trautv) a widespread species of the Apiaceae reveals high nutritional value and therapeutic properties due to the significant content of biologically active metabolites such as essential oils, phenolic compounds, and flavonoids. The present study was performed to evaluate the morphological and biochemical variability and antioxidant properties of naturally grown populations of eryngo. One-way ANOVA showed significant (p < .01) differences in the majority of parameters measured among the studied populations. The range of fresh weight was from 1.3 to 12.0 g/plant, while dry weight varied from 0.01 to 6.0 g/plant. The highest variation was observed for essential oil yield (CV = 205.32%) followed by essential oil content (CV = 126.23%) and chicoric acid content (CV = 71.18%). Total phenolics content varied from 8.85 to 88.15 mg GAE/g extract. Total flavonoids value ranged from 5.41 to 134.40 mg QE/g extract. Rosmarinic acid and chicoric acid contents varied from 0.118-1.234 and 0.014-0.597 µg/g DW, respectively. DPPH free radical scavenging activity varied from 76.12 to 513.5 µg/mL, while it ranged from 156.7 to 477.1 µg/mL with the ferrous ions (Fe2+) chelating assay. Rosmarinic acid and chicoric acid showed a significant and positive correlation (r 0.01 = 0.81 and r 0.05 = 0.40) with total phenolics, respectively. The Ward dendrogram analysis revealed two different clusters based on the parameters measured, confirming high morpho-phytochemical variability among the individuals and populations. Principal component analysis (PCA) revealed eight PCs which contributed to 99.97% of the overall variance, and leaf length, essential oil content, and antioxidant activity in terms of DPPH and Fe2+ chelating techniques were the most effective attributes for characterizing and selecting the studied population. Based on the traits related to vegetative yield and antioxidant properties, eight individuals from two populations were superior for breeding and/or farming programs.

Foliar-applied nanoscale zero-valent iron (nZVI) and iron oxide (Fe3O4) induce differential responses in growth, physiology, antioxidative defense and biochemical indices in Leonurus cardiaca L.

The impacts of nZVI and iron oxides on growth, physiology and elicitation of bioactive antioxidant metabolites in medicinal aromatic plants must be critically assessed to ensure their safe utilization within the food chain and achieve nutritional gains. The present study investigated and compared the morpho-physiological and biochemical changes of Leonurus cardiaca L. plants as affected by various concentrations (0, 250, 500 and 1000 mg L-1) of nZVI and Fe3O4. The foliar uptake of nZVI was verified through Scanning Electron Microscopy (SEM) images and Energy Dispersive X-ray (EDX) analytical spectra. Plants exposed to nZVI at low concentration showed comparatively monotonic deposition of NPs on the surface of leaves, however, the agglomerate size of nZVI was raised as their doses increased, leading to remarkable changes in anatomical and biochemical traits. 250 mg L-1 nZVI and 500 mg L-1 Fe3O4 significantly (P < 0.05) increased plant dry matter accumulation by 37.8 and 27% over the control, respectively. The treatments of nZVI and Fe3O4 at 250 mg L-1 significantly (P < 0.01) improved chlorophyll a content by 22.4% and 15.3% as compared to the control, and then a rapid decrease (by 14.8% and 4.1%) followed at 1000 mg L-1, respectively. Both nZVI and Fe3O4 at 250 mg L-1 had no significant impact on malondialdehyde (MDA) formation, however, at an exposure of 500-1000 mg L-1, the MDA levels and cellular electrolyte leakage were increased. Although nZVI particles could be utilized by plants and enhanced the synthesis of chlorophylls and secondary metabolites, they appeared to be more toxic than Fe3O4 at 1000 mg L-1. Exposure to nZVI levels showed positive, negative and or neutral impacts on leaf water content compared to control, while no significant difference was observed with Fe3O4 treatments. Soluble sugar, total phenolics and hyperoside content were significantly increased upon optimum concentrations of employed treatments-with 250 mg L-1 nZVI being most superior. Among the extracts, those obtained from plants treated with 250-500 mg L-1 nZVI revealed the strong antioxidant activity in terms of scavenging free radical (DPPH) and chelating ferrous ions. These results suggest that nZVI (at lower concentration) has alternative and additional benefits both as nano-fertilizer and nano-elicitor for biosynthesis of antioxidant metabolites in plants, but at high concentrations is more toxic than Fe3O4.

Guar (Cyamopsis tetragonoloba L.) plant gum: From biological applications to advanced nanomedicine.

Natural polymers are an efficient class of eco-friendly and biodegradable polymers, because they are readily available, come from natural sources, inexpensive and can be chemically modified with the correct reagents. Guar gum (GG) is a natural polymer with great potential to be used in pharmaceutical formulations due to its unique composition and lack of toxicity. GG can be designed to suit the needs of the biological and medical engineering sectors. In the development of innovative drug delivery systems, GG is commonly utilized as a rate-controlling excipient. In this review, different properties of GG including chemical composition, extraction methods and its usefulness in diabetes, cholesterol lowering, weight control, tablet formulations as well as its food application were discussed. The other purpose of this study is to evaluate potential use of GG and its derivatives for advanced nanomedicine such as drug delivery, tissue engineering and nanosensing. It should be noted that some applicable patents in medical area have also been included in the rest of this survey to extend knowledge about guar gum and its polymeric nature.

New insights into the role of nanotechnology in microbial food safety.

Today, the role of nanotechnology in human life is undeniable as a broad range of industries, particularly food and medicine sectors, have been dramatically influenced. Nanomaterials can contribute to food safety by forming new nano-sized ingredients with modified physicochemical characteristics. Nanotechnologies can inhibit the growth of food spoilage microorganisms by recruiting novel and unique agents that are involved in removal of microbes from foods or prevent adhesion of microbial cells to food surfaces. Hence, nanotechnology could be considered as a high-potential tool in food packaging, safety, and preservation. Moreover, the prevention of biofilm formation by disturbing the attachment of bacteria to the food surface is another useful nanotechnological approach. Recently, nanoparticle-based biosensors have been designed and developed to detect the food-borne pathogens and hazardous substances through complicated mechanisms. During the past half-century, many methods such as freeze-drying and spray drying have been employed for increasing the viability in food industries; however, the other novel approaches such as encapsulation methods have also been developed. Admittedly, some beneficial bacteria such as probiotics bring diverse benefits for human health if only they are in a sufficient number and viability in the food products and gastrointestinal tract (GI). Encapsulation of these valuable microbial strains by nanoparticles improves the survival of probiotics under harsh conditions such as extreme levels of temperature, pH, and salinity during the processing of food products and within the GIT tract. The survival and effectiveness of encapsulated microorganisms depends on different factors including function of cell wall components in bacteria and type of coating materials. This review aims to broadly explore the potential of different aspects of nanotechnology in food industry, especially for packaging, preservation, safety, and viability.

Integral water capacity (IWC) and least limiting water range (LLWR): prediction using plant growth indices and soil properties.

Soil water availability is an important field of study in soil water and plant relationship. Least limiting water range (LLWR) and integral water capacity (IWC) are two important concepts which are used for water availability to plant. LLWR is determined from four moisture coefficients (θ AFP, θ FC, θ SR, θ PWP) that are the soil water contents 10% air-filled porosity (AFP), at field water capacity (FC), 2 MPa penetration resistance (SR), and permanent wilting point (PWP), respectively. The computation is dependent on critical values, so IWC was introduced to avoid using the critical limits that sharply rises in a cut-off from 0 to 1 at the wet end of water release curve or sharply falls from 1 to 0 at the dry side in the previous concepts of water availability for plant. IWC is the integral of differential water capacity function (C(h)) in the amplitude of 0 to infinity soil matric potential (h) multiplied by some weighting functions (ω i (h)) each considering the effect of various soil limitations on water availability to plants. Up to now, the effect of different soil attributes and the tillage treatments have been reviewed on LLWR. The effect of soil various physical and chemical limitations such as soil hydraulic conductivity (K(h)), aeration, SR, and salinity has been considered on IWC computation. LLWR and especially IWC have been seldom studied using plant real response. Results of few studies about LLWR and IWC using stomatal conductance and canopy temperature showed that their values were considerably different with those computed based on previously introduced critical limits for LLWR and weighting functions for IWC. These differences indicate that the critical limits proposed by da Silva et al. (Soil Sci Soc Am J 58:1775-1781, 1994) and weighting functions by Groenevelt et al. (Aust J Soil Res 39:577-598, 2001) may not be applied indiscriminately for all plants and should to be modified according to plant response. Physiological characteristics like transpiration and photosynthesis rate, chlorophyll index, leaf water potential, and relative water content also could be appropriate indices for monitoring plant water status and computation the real value of LLWR and IWC in the field or greenhouse for various types of plants.

Physiological and antioxidative responses to GO/PANI nanocomposite in intact and demucilaged seeds and young seedlings of Salvia mirzayanii.

The current study aimed to investigate the impacts of different concentrations of GO/PANI nanocomposites (25, 50 and 100 mg L-1), in comparison with GO and PANI, on seed germination behaviors, morpho-physiological and biochemical traits in intact (mucilaginous) and demucilaged seeds, and young seedlings of the medicinal plant Salvia mirzayanii. Upon exposure to GO, seed germination was delayed and reduced, and growth attributes (root and shoot length, shoot fresh weight, and total chlorophyll content) declined, all of which could be attributed to the reductions in water uptake and oxidative stress particularly in demucilaged seeds. A hormetic dose-dependent response was observed for the growth traits in both intact and demucilaged seedlings upon exposure to GO/PANI concentrations, i.e. low-concentration stimulation and high-concentration repression. Elevated levels of H2O2 in shoot tissue of the seedlings exposed to GO and high concentration of GO/PANI, in comparison with those exposed to low levels of GO/PANI and control, were linked with the activities of the antioxidant enzymes SOD, CAT, POD, and total phenolics. Overall, the results showed high toxicity of GO on germination and early growth of S. mirzayani that was more evident in demucilaged seedlings, whereas GO/PANI stimulated germination, and the effects on seedling growth were stimulatory or inhibitory depending on the application dose and presence of mucilage. Furthermore, the capacity of GO/PANI nanocomposites to improve germination and cause a regular porosity pattern in roots accompanied by improved water uptake and early establishment of S. mirzayanii propose potential implications of GO/PANI nanocomposites for seeds/plants in drought-prone ecosystems.

Toxicity assessment of multi-walled carbon nanotubes on Cucurbita pepo L. under well-watered and water-stressed conditions.

The rapid increase in the production and application of various types of nanomaterials increases the possibility of their presence in total environment, which subsequently raises concerns about their potential threats to the first trophic level of organisms, specifically under varying environmental constraints. In this work, seeds of Cucurbita pepo L. were cultured in MS basal medium exposed to multi-walled carbon nanotubes (MWCNTs) at different concentrations (0, 125, 250, 500 and 1000µgmL-1) under two levels of water potential, well-watered (0MPa) and water stress (-1.5MPa) induced by polyethylene glycol (PEG 6000) for 14 days. Seeds exposed to MWCNTs showed reduction in germination percentage, root and shoot length, biomass accumulation and vigor index in a dose-dependent manner. However, seedlings germinated in MWCNTs-fortified media had significantly lower germination and growth attributes than those of control under water stress conditions. This happened due to increased oxidative injury indices including hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents, as well as electrolyte leakage index (ELI) of tissues. The impaired morpho-physiological and biochemical processes of seedlings exposed to different concentrations of MWCNTs under both PEG-induced stress and non-stress growing conditions were consequence of changes in the activation of various cellular antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (POD). Taken together, our findings reveal that MWCNTs played negative role on seed germination and subsequent growth of C. pepo L. seedlings under both levels of water potential.

Mechanisms underlying toxicity and stimulatory role of single-walled carbon nanotubes in Hyoscyamus niger during drought stress simulated by polyethylene glycol.

In this study, seeds of Hyoscyamus niger were exposed to different concentrations (50-800µgmL-1) of single-walled carbon nanotubes (SWCNTs) under different levels of drought stress (0.5-1.5MPa) for 14days. Germinated seeds were subsequently allowed to grow in the same culture media for 7 more days to test the further response of the seedlings in terms of biochemical changes to the employed treatments. Seeds subjected to drought showed reduction in germination percentage, vigor and lengths of roots and shoots. However, inclusion of SWCNTs at the two lowest concentrations significantly alleviated the drought stress (up to moderate levels only)-induced reduction in germination and growth attributes. This happened due to increased water uptake, up-regulation of mechanisms involved in starch hydrolysis, and reduction in oxidative injury indices including H2O2, malondialdehyde contents and electrolyte leakage. The improved plant performance under PEG-induced drought stress was a consequence of changes in the expression of various antioxidant enzymes including SOD, POD, CAT, and APX, and also biosynthesis of proteins, phenolics, and specific metabolites such as proline. Results demonstrate that treatment by low concentrations of SWCNTs can induce tolerance in seedlings against low to moderate levels of drought through enhancing water uptake and activating plant defense system.

Engineered nanomaterial-mediated changes in the metabolism of terrestrial plants.

Engineered nanomaterials (ENMs) possess remarkable physicochemical characteristics suitable for different applications in medicine, pharmaceuticals, biotechnology, energy, cosmetics and electronics. Because of their ultrafine size and high surface reactivity, ENMs can enter plant cells and interact with intracellular structures and metabolic pathways which may produce toxicity or promote plant growth and development by diverse mechanisms. Depending on their type and concentration, ENMs can have positive or negative effects on photosynthesis, photochemical fluorescence and quantum yield as well as photosynthetic pigments status of the plants. Some studies have shown that ENMs can improve photosynthetic efficiency via increasing chlorophyll content and light absorption and also broadening the spectrum of captured light, suggesting that photosynthesis can be nano-engineered for harnessing more solar energy. Both up- and down-regulation of primary metabolites such as proteins and carbohydrates have been observed following exposure of plants to various ENMs. The potential capacity of ENMs for changing the rate of primary metabolites lies in their close relationship with activation and biosynthesis of the key enzymes. Several classes of secondary metabolites such as phenolics, flavonoids, and alkaloids have been shown to be induced (mostly accompanied by stress-related factors) in plants exposed to different ENMs, highlighting their great potential as elicitors to enhance both quantity and quality of biologically active secondary metabolites. Considering reports on both positive and negative effects of ENMs on plant metabolism, in-depth studies are warranted to figure out the most appropriate ENMs (type, size and optimal concentration) in order to achieve the desirable effect on specific metabolites in a given plant species. In this review, we summarize the studies performed on the impacts of ENMs on biosynthesis of plant primary and secondary metabolites and mention the research gaps that currently exist in this field.

Phytochemical Variations and Enhanced Efficiency of Antioxidant and Antimicrobial Ingredients in Salvia officinalis as Inoculated with Different Rhizobacteria.

Plants produce a variety of secondary metabolites to improve their performance upon exposure to pathogens, pests, herbivores, or environmental stresses. Secondary metabolism in plants is, therefore, highly regulated by presence of biotic or abiotic elicitors in the environment. The present research was undertaken to characterize plant growth-promoting attributes of four plant growth-promoting rhizobacteria (PGPR) including two Pseudomonas fluorescens (Pf Ap1, Pf Ap18) and two P. putida (Pp Ap9, Pp Ap14) strains, and to determine their role (individually or in consortium) on growth of Salvia officialis, and biosynthesis of secondary metabolites such as essential oils (EOs), total phenolics, and flavonoids. The antioxidant and antibacterial properties of the extracts and EOs obtained from the inoculated plants were also investigated. The PGPR inoculum was applied to soil, cuttings, and foliage. Results indicated that different PGPR strains varied in their efficiency for production of auxin, siderophore, 1-aminocyclopropane-1-carboxylate deaminase, and phosphate solubilization. All individually inoculated plants had significantly higher shoot and root biomass, leaf P content, EOs yield, total phenolics, and flavonoids content compared to uninoculated control plants. The major constituents of EOs, cis-thujene, camphor, and 1,8-cineol, increased following inoculation with reference PGPRs. Although the extract from all inoculated plants had improved antioxidant activity, it was remarkable for the Pf Ap18 strain, which had the lowest IC50 value across treatments. Antibacterial assay of various EOs and their major constituents against pathogenic bacteria showed that the highest activity was observed against Staphylococcus aureus using EOs of Pp Ap14 source. Based on our findings, we suggest that individual inoculation with effective PGPR strains can substantially improve plant growth and secondary metabolism in S. officinalis plants.