Effect of foliar application of cerium oxide nanoparticles on growth, photosynthetic pigments, electrolyte leakage, compatible osmolytes and antioxidant enzymes activities of Calendula officinalis L

Impact of titanium dioxide (TiO2) nanoparticle and liquid leachate of mushroom compost on agronomic and biochemical response of marigold (Tagetes erecta L.) under saline stress

The cultivation of ornamental horticultural crops under salinity stress has been a challenge for growers all over the world. In this study, an attempt was made for pot cultivation of Marigold (Tagetes erecta L. var. Pusa Basanti Gainda) in salt-stressed (SS) soil (150 mM) with the combined use of mushroom compost leachate (CL) and foliar application of titanium dioxide nanoparticles (TiO2-NPs). For this purpose, a total of six pot treatments, i.e., borewell water (BW; control), T1 (BW with SS), T2 (BW with SS and TiO2-NPs), T3 (CL supplemented), T4 (CL with SS), and T5 (CL with SS and TiO2-NPs) were conducted in triplicate. The results of this study showed that CL supplementation significantly (p < 0.05) improved the physicochemical i.e., pH (14.5%), electrical conductivity (32.9%), total nitrogen (27.4%), total phosphorus (247.6%)), and nutrient (organic matter: 119.6%) profiles of soil which later helped in higher growth (30-35%) and yield (5.4-40.7%) of T. erecta. In CL-based treatments, the biochemical constituents were significantly (p < 0.05) higher than those in BW-irrigated ones. Also, the levels of selected stress defense enzymes were significantly increased under SS treatment but reduced under TiO2-NP application. Overall, it was observed that the combined application of CL and TiO2-NPs (T5 treatment) was the most helpful treatment for enhanced germination, growth, yield, biochemical parameters, and better plant enzymatic activities to cope with saline stress. This study provides a mechanistic understanding of T. erecta plants under saline stress which is crucial for the development of targeted interventions aimed at improving plant tolerance to saline conditions.

Unlocking the potential of SiO2 and CeO2 nanoparticles for arsenic mitigation in Vigna mungo L. Hepper (Blackgram)

In this study, the interaction effects of NaAsO2 (1 and 5 μM), SiO2 NPs (10 and 100 mg/L) and CeO2 NPs (10 and 100 mg/L) were assessed in Vigna mungo (Blackgram). The treatment of NaAsO2, SiO2, CeO2-NPs and combinations of NPs & As were applied to blackgram plants under hydroponic conditions. After its application, the morpho-physiological, antioxidant activity, and phytochemical study were evaluated. At 10 and 100 mg/L of SiO2 and CeO2-NPs, there was an increase in antioxidative enzymatic activity (p < 0.05) and reactive oxygen species (ROS). However, substantial ROS accumulation was observed at 1 and 5 μM NaAsO2 and 100 mg/L SiO2 NPs (p < 0.05). Additionally, at such concentrations, there is a substantial reduction in photosynthetic pigments, nitrogen fixation, chlorosis, and plant development when compared to controls (p < 0.05). The combination of SiO2 and CeO2 NPs (10 and 100 mg/L) with NaAsO2 decreased superoxide radical and hydrogen peroxide and improved SOD, CAT, APX, GR, and chlorophyll pigments (p < 0.05). Further FTIR results were evaluated for documenting elemental and phytochemical analysis.

Plant-nano interactions: A new insight of nano-phytotoxicity

Whether nanoparticles (NPs) are boon or bane for society has been a centre of in-depth debate and key consideration in recent times. Exclusive physicochemical properties like small size, large surface area-to-volume ratio, robust catalytic activity, immense surface energy, magnetism and superior biocompatibility make NPs obligatory in many scientific, biomedical and industrial ventures. Nano-enabled products are newer entrants in the present era. To attenuate environmental stress and maximize crop yields, scientists are tempted to introduce NPs as augmented supplements in agriculture. The feasible approaches for NPs delivery are irrigation, foliar spraying or seed priming. Internalization of excessive NPs to plants endorses negative implications at higher trophic levels via biomagnification. The characteristics of NPs (dimensions, type, solubility, surface charge), applied concentration and duration of exposure are prime factors conferring nanotoxicity in plants. Several reports approved NPs persuaded toxicity can precisely mimic abiotic stress effects. The signature effects of nanotoxicity include poor root outgrowth, biomass reduction, oxidative stress evolution, lipid peroxidation, biomolecular damage, perturbed antioxidants, genotoxicity and nutrient imbalance in plants. NPs stress impels mitogen-activated protein kinase signaling cascade and urges stress responsive defence gene expression to counteract stress in plants. Exogenous supplementation of nitric oxide (NO), arbuscular mycorrhizal fungus (AMF), phytohormones, and melatonin (ME) is novel strategy to circumvent nanotoxicity. Briefly, this review appraises plants' physio-biochemical responses and adaptation scenarios to endure NPs stress. As NPs stress represents large-scale contaminants, advanced research is indispensable to avert indiscriminate NPs usage for synchronizing nano-security in multinational markets.

The Impact of Nanomaterials on Photosynthesis and Antioxidant Mechanisms in Gramineae Plants: Research Progress and Future Prospects

As global food security faces challenges, enhancing crop yield and stress resistance becomes imperative. This study comprehensively explores the impact of nanomaterials (NMs) on Gramineae plants, with a focus on the effects of various types of nanoparticles, such as iron-based, titanium-containing, zinc, and copper nanoparticles, on plant photosynthesis, chlorophyll content, and antioxidant enzyme activity. We found that the effects of nanoparticles largely depend on their chemical properties, particle size, concentration, and the species and developmental stage of the plant. Under appropriate conditions, specific NMs can promote the root development of Gramineae plants, enhance photosynthesis, and increase chlorophyll content. Notably, iron-based and titanium-containing nanoparticles show significant effects in promoting chlorophyll synthesis and plant growth. However, the impact of nanoparticles on oxidative stress is complex. Under certain conditions, nanoparticles can enhance plants' antioxidant enzyme activity, improving their ability to withstand environmental stresses; excessive or inappropriate NMs may cause oxidative stress, affecting plant growth and development. Copper nanoparticles, in particular, exhibit this dual nature, being beneficial at low concentrations but potentially harmful at high concentrations. This study provides a theoretical basis for the future development of nanofertilizers aimed at precisely targeting Gramineae plants to enhance their antioxidant stress capacity and improve photosynthesis efficiency. We emphasize the importance of balancing the agricultural advantages of nanotechnology with environmental safety in practical applications. Future research should focus on a deeper understanding of the interaction mechanisms between more NMs and plants and explore strategies to reduce potential environmental impacts to ensure the health and sustainability of the ecosystem while enhancing the yield and quality of Gramineae crops.

Impact of pharmaceutical industry wastewater on stress physiological responses of Spirodela polyrhiza (L.) Schleiden

Impact of pharmaceutical wastewater collected from aeration tank on aquatic macrophyte Spirodela polyrhiza (L.) Schleiden was studied in the present study. Various plant parameters such as chlorophyll, protein, and proline content of wastewater-exposed plants were examined to determine the toxic impacts of pharmaceutical wastewater. In addition to these parameters, electrolyte leakage (EL) and catalase (CAT) activities in S. polyrhiza were assessed for each day of exposure to the wastewater. S. polyrhiza was exposed to four different wastewater concentrations (25%, 50%, 75%, and 100%) under laboratory conditions for 7 days. The plants experienced severe toxicity as revealed by the reduction in photosynthetic pigments, increase in electrolyte leakage, and enhancement of antioxidant enzyme (CAT) activity in S. polyrhiza with an increase in concentration and time of exposure to pharmaceutical effluent.

Evaluation of nanoceria on cadmium uptake in Triticum aestivum (L.) and its implications for dietary health risk

In recent times, significant attention has been directed toward the synthesis and application of nanoparticles (NPs) in agriculture sector. In current study, nanoceria (CeO2 NPs) synthesized by green method were employed to address cadmium (Cd) accumulation in wheat (Triticum aestivum L.) cultivated in field with excess Cd. The application of CeO2 NPs was carried out through foliar spraying, performed twice during the growth of T. aestivum. Four levels of CeO2 NPs were used: T0, T1, T2, and T3 as 0, 50, 75, and 100 mgL-1, respectively. Results highlighted the positive effects of CeO2 NPs on various growth parameters, including plant height, spike length, photosynthetic related attributes, as well as straw and grain of grains in comparison to T1 (control group). Furthermore, CeO2 NPs led to a reduction in oxidative stress in the leaves and enhanced in enzyme activities in comparison to T1. Notably, Cd concentrations in straw, roots, and grains exhibited a decline following the treatment with CeO2 NPs, in contrast to the control group. In terms of health implications, the calculated health risk index associated with dietary consumption of grains by adults remained below the defined threshold with supply of nanoparticles. Foliar application of CeO2 NPs proved to be an effective approach in reducing cadmium content in wheat grains. This reduction holds significant potential for minimizing the risk of cadmium exposure to human health through the food chain. Employing the green synthesis method amplifies the potential for extensive production and a wide array of environmental applications for CeO2 NPs. This dual capacity makes them proficient in tackling environmental stresses while concurrently mitigating adverse ecological effects.

Foliar-applied nano-cerium dioxide differentially affect morpho-physiological traits and essential oil profile of Salvia mirzayanii Rech. f. & Esfand under drought stress and post-stress recovery conditions

Drought stress is known to diminish the growth and yield of plants by altering the physiological, biochemical and molecular processes, thus threatening food security worldwide. Nanoparticles (NPs) have emerged as an effective strategy to raise plant productivity under current rapid environmental challenges. However, there is little literature on mechanisms underlying the beneficial role of re-watering in drought-stressed plants treated with NPs. In this study, the effects of cerium dioxide nanoparticles [(CeO2 NPs), 0 (control), 125, 250, 500, and 1000 mL L-1] were investigated on morpho-physiological and phytochemical traits of Salvia mirzayanii plants under different drought stress intensities [(25%, 50%, 75%, and 100% (control) of field capacity (FC) moisture] and post-stress re-watering (recovery) in a three-way factorial arrangement based on randomized complete block design. Uptake and accumulation of CeO2 NPs in the leaf tissue of plant samples were confirmed using SEM and EDX techniques. The results of ANOVA demonstrated that growth and physio-phytochemical traits were significantly (p < 0.05) affected by individual treatment and/or their double and triple interactions. Exposure to various levels of CeO2 NPs during drought stress mitigated the adverse effects of stress on growth parameters (e.g., plant height, shoot and root dry weights, and root length) and photosynthetic pigments (chlorophyll a and b) content compared to the respective controls in varying degrees. However, proline and essential oil content were increased in drought-stressed plants, and tended to decrease during the period of recovery. Before re-watering, the antioxidant enzymes, CAT, POD, and SOD, activity in leaf tissues was increased with the increase of drought stress intensity upon both treated and non-treated CeO2 NPs conditions. However, the three-way interaction results demonstrated that recovery after drought stress following CeO2 NPs application particularly 1000 mL L-1 decreased the activity of antioxidant enzymes compared to the controls. Based on GC and GC-MS analysis, all essential oil samples predominantly composed of oxygenated monoterpenes and sesquiterpenes including Decane, Spathulenol, Octane, α-Terpinyl acetate, Hexyl isovalerate, Dodecane, Butanoic acid, Linalool, δ-Cadinene, Muurolol, α-Cadinol, Eudesm-7(11)-en-4-ol, which significantly (p < 0.05) changed under different experimental treatments. The recovery after stress, however, increased only the content of δ-Cadinene in plants from severe drought stress upon foliar application of 1000 mL L-1 CeO2 NPs compared to the non-recovery period. Conclusively, integrative use of CeO2 NPs and re-watering after drought stress could be an encouraging and eco-friendly strategy to improve both drought tolerance, growth and pyhtochemical contents in S. mirzayanii plants.

Effect of green synthesized cerium oxide nanoparticles on fungal disease of wheat plants: A field study

Recently, there has been considerable attention towards the production of environmentally friendly nanoparticles (NPs). In this investigation, the successful synthesis of cerium oxide nanoparticles (CeO2 NPs) was achieved by employing an eco-friendly technique that utilized an extract from the leaves of local plant quinoa (Chenopodium quinoa L.). The synthesized CeO2 NPs were subjected to characterization using state-of-the-art methods. The prepared CeO2 NPs contained a round shape with clusters and have a size of 7-10 nm. To assess how effective CeO2 NPs derived from C. quinoa were against Ustilago tritici, a fungal disease that negatively affects wheat crop globally, a study was performed on two varieties of wheat crop comprised of Arooj (V1) and Akber (V2), cultivated under field conditions. CeO2 NPs were applied foliarly twice to the wheat crop at four different concentrations: T0 (0 mg/L), T1 (50 mg/L), T2 (75 mg/L), and T3 (100 mg/L). The results revealed that the control group (T0) exhibited the highest disease severity index (DSI) with a value of 75% compared to the other concentrations of CeO2 NPs on both varieties. At a concentration of 100 mg/L of CeO2 NPs, the DSI dropped to a minimum of 35% and 37% on both V1 and V2 respectively. These findings indicated that an increase in the concentration of CeO2 NPs has a beneficial impact on disease severity. Similar patterns have also been observed with disease incidence (DI), with the greatest efficacy observed at a concentration of 100 mg/L of CeO2 NPs. Our investigation has shown that CeO2 NPs exhibitd significant antifungal potential against U. tritici which may be a promising strategy to mitigate fungal disease and crop losses globally.

Synthesis and characterization of CeO2 and SiO2 nanoparticles and their effect on growth parameters and the antioxidant defense system in Vigna mungo L. Hepper

Engineered nanoparticles (NPs) have recently attracted a lot of attention after being tested in various agricultural plants. This paper reports the green synthesis of CeO2 NPs and SiO2 NPs from leaf extracts of Nyctanthes arbor-tristis. The physical characteristics of the produced nanoparticles were then determined using UV-visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Furthermore, the interaction effects of cerium oxide NPs (C1, C2, and C3) and silicon dioxide NPs (S1, S2, and S3) at 10 mg/L on blackgram (Vigna mungo L.) were evaluated. CeO2 and SiO2 NPs treatments enhanced the growth performance of the plants by causing a decrease in superoxide radical (SOR) and H2O2 via improving antioxidant enzymes. These findings imply that the size and shape of CeO2 and SiO2 NPs provide defense against oxidative damage to the blackgram.

Nanoparticles-Based Delivery Systems for Salicylic Acid as Plant Growth Stimulator and Stress Alleviation

The population growth tendency leads to an increase in demand for food products, and in particular, products obtained from the processing of plants. However, there are issues of biotic and abiotic stresses that can significantly reduce crop yields and escalate the food crisis. Therefore, in recent years, the development of new methods of plant protection became an important task. One of the most promising ways to protect plants is to treat them with various phytohormones. Salicylic acid (SA) is one of the regulators of systemic acquired resistance (SAR) signaling pathways. These mechanisms are able to protect plants from biotic and abiotic stresses by increasing the expression of genes that encode antioxidant enzymes. However, salicylic acid in high doses can act as an antagonist and have the negative rebound effect of inhibition of plant growth and development. To maintain optimal SA concentrations in the long term, it is necessary to develop systems for the delivery and slow release of SA in plants. The purpose of this review is to summarize and study methods of delivery and controlled release of SA in a plant. Various carriers-based nanoparticles (NPs) synthesized from both organic and inorganic compounds, their chemical structure, impacts on plants, advantages, and disadvantages are comprehensively discussed. The mechanisms of controlled release of SA and the effects of the use of the considered composites on the growth and development of plants are also described. The present review will be helpful to design or fabricate NPs and NPs-based delivery systems for salicylic acid-controlled release and better understating of the mechanism of SA-NPs interaction to alleviate stress on plants.

Foliar application of nanoceria attenuated cadmium stress in okra (Abelmoschus esculentus L.)

Foliar application of nanoparticles (NPs) as a means for ameliorating abiotic stress is increasingly employed in crop production. In this study, the potential of CeO₂-NPs as stress suppressants for cadmium (Cd)-stressed okra (Abelmoschus esculentus) plants was investigated, using two cycles of foliar application of CeO₂-NPs at 200, 400, and 600 mg/l. Compared to untreated stressed plants, Cd-stressed plants treated with CeO₂-NPs presented higher pigments (chlorophyll a and carotenoids). In contrast, foliar applications did not alter Cd root uptake and leaf bioaccumulation. Foliar CeO₂-NPs application modulated stress enzymes (APX, SOD, and GPx) in both roots and leaves of Cd-stressed plants, and led to decreases in Cd toxicity in plant's tissues. In addition, foliar application of CeO₂-NPs in Cd-stressed okra plants decreased fruit Cd contents, and improved fruit mineral elements and bioactive compounds. The infrared spectroscopic analysis of fruit tissues showed that foliar-applied CeO₂-NPs treatments did not induce chemical changes but induced conformational changes in fruit macromolecules. Additionally, CeO₂-NPs applications did not alter the eating quality indicator (Mg/K ratio) of okra fruits. Conclusively, the present study demonstrated that foliar application of CeO₂-NPs has the potential to ameliorate Cd toxicity in tissues and improve fruits of okra plants.

Foliar Application of Iron Oxide Nanoparticles Promotes Growth, Mineral Contents, and Medicinal Qualities of Solidago virgaurea L

Goldenrod (Solidago virgaurea L.) is considered for their medicinal properties for humans. These properties are attributed to some volatile compounds that can be extracted from above- and underground organs of plants. More ingredients of medicinal plants are undoubtedly considered by herbal medicine activists. The study aimed to promote Solidago yield and quality under foliar application of Fe₂O₃ nanoparticles that can be considered as a safe and healthy fertilizer on the basis of US Food and Drug Administration (FDA) regulatory process about color additives. The experiment was performed with concentrations of Fe₂O₃ nanoparticles (0, 0.5, or 1 mg L^-1) and foliar application times (1, 2, 3, 4, or 5 times) on 4- to 5-leaf plants of Solidago virgaurea. Results showed that 4 times foliar application of 1 mg L^-1 caused the best plant growth and mineral element contents (nitrogen, phosphorous, potassium, copper, and zinc) except for Fe content that the more the times of foliar application, the more the Fe content increased. However, the flavonoid (rutin and quercetin) and essential oils (caryophyllene, alpha-pinene, camphene, limonene, linalool, myrcene, and terpinene) as biochemical and medicinal qualities of the treated plants were remarkably promoted when 1 mg L^-1 of nanoparticles was sprayed 5 times. Furthermore, the more the element contents, the more the ingredients. Finally, based on the goals of herbal medicine activists for the production of the essence, extract, or herb, both 5 and 4 times of foliar applications of ferric oxide nanoparticles are safe and may be economic and recommendable.

Effect of Phytosynthesized Selenium and Cerium Oxide Nanoparticles on Wheat (Triticum aestivum L.) against Stripe Rust Disease

In this study, selenium nanoparticles (SeNPs) and cerium oxide nanoparticles (CeONPs) were synthesized by using the extract of Melia azedarach leaves, and Acorus calamusas rhizomes, respectively, and investigated for the biological and sustainable control of yellow, or stripe rust, disease in wheat. The green synthesized NPs were characterized by UV-Visible spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD). The SeNPs and CeONPs, with different concentrations (i.e., 10, 20, 30, and 40 mg/L), were exogenously applied to wheat infected with Puccinia striformis. SeNPs and CeONPs, at a concentration of 30 mg/L, were found to be the most suitable concentrations, which reduced the disease severity and enhanced the morphological (plant height, root length, shoot length, leaf length, and ear length), physiological (chlorophyll and membrane stability index), biochemical (proline, phenolics and flavonoids) and antioxidant (SOD and POD) parameters. The antioxidant activity of SeNPs and CeONPs was also measured. For this purpose, different concentrations (50, 100, 150, 200 and 400 ppm) of both SeNPs and CeONPs were used. The concentration of 400 ppm most promoted the DPPH, ABTS and reducing power activity of both SeNPs and CeONPs. This study is considered the first biocompatible approach to evaluate the potential of green synthesized SeNPs and CeONPs to improve the health of yellow, or stripe rust, infected wheat plants and to provide an effective management strategy to inhibit the growth of Puccinia striformis.

Application of Cerium Dioxide Nanoparticles and Chromium-Resistant Bacteria Reduced Chromium Toxicity in Sunflower Plants

The continuous increase in the heavy metals concentration in the soil due to anthropogenic activities has become a global issue. The chromium, especially hexavalent chromium, is highly toxic for living organisms due to high mobility, solubility, and carcinogenic properties. Considering the beneficial role of nanoparticles and bacteria in alleviating the metal stress in plants, a study was carried out to evaluate the role of cerium dioxide (CeO₂) nanoparticles (NPs) and Staphylococcus aureus in alleviating the chromium toxicity in sunflower plants. Sunflower plants grown in chromium (Cr) contaminated soil (0, 25, and 50 mg kg^-1) were treated with CeO₂ nanoparticles (0, 25, and 50 mg L^-1) and S. aureus. The application of Cerium Dioxide Nanoparticles (CeO₂ NPs) significantly improved plant growth and biomass production, reduced oxidative stress, and enhanced the enzymatic activities in the sunflower plant grown under chromium stress. The application of S. aureus further enhanced the beneficial role of nanoparticles in alleviating metal-induced toxicity. The maximum improvement was noted in plants treated with both nanoparticles and S. aureus. The augmented application of CeO₂ NPs (50 mg l^-1) at Cr 50 mg kg^-1 increased the chl a contents from 1.2 to 2.0, chl b contents 0.5 to 0.8 and mg g^-1 FW, and decreased the leakage of the electrolyte from 121 to 104%. The findings proved that the application of CeO₂ nanoparticles and S. aureus could significantly ameliorate the metal-induced stress in sunflower plants. The findings from this study can provide new horizons for research in the application of nanoparticles in phytoremediation and bioremediation.

Foliar Application of Cerium Oxide-Salicylic Acid Nanoparticles (CeO2:SA Nanoparticles) Influences the Growth and Physiological Responses of Portulaca oleracea L. under Salinity

In the present study, the effects of foliar application of salicylic acid (100 μM), cerium oxide (50 mg L⁻¹), and cerium oxide:salicylic acid nanoparticles (CeO₂: SA-nanoparticles, 50 mg L⁻¹ + 100 μM) on the growth and physiological responses of purslane (Portulaca oleracea L.) were examined in non-saline and saline conditions (50 and 100 mM NaCl salinity). Foliar applications mitigated salinity-induced adverse effects, and the highest plant height and N, P, Mg, and Mn content were recorded in the variant with non-saline × foliar use of CeO₂: SA-nanoparticles. The highest values of fresh and dry weight were noted in the treatment with no-salinity × foliar use of CeO₂:SA-nanoparticles. The highest number of sub-branches was observed in the foliar treatments with CeO₂-nanoparticles and CeO₂:SA-nanoparticles without salinity stress, while the lowest number was noted in the 100 mM NaCl treatment. Moreover, the foliar application of CeO₂:SA-nanoparticles and cerium-oxide nanoparticles improved the total soluble solid content, K, Fe, Zn, Ca, chlorophyll a, and oil yield in the plants. The salinity of 0 and 50 mM increased the K content, 1000-seed weight, total soluble solid content, and chlorophyll b content. The use of 100 mM NaCl with no-foliar spray increased the malondialdehyde, Na, and H₂O₂ content and the Na⁺/K⁺ ratio. No-salinity and 50 mM NaCl × CeO₂: SA-nanoparticle interactions improved the anthocyanin content in plants. The phenolic content was influenced by NaCl₁₀₀ and the foliar use of CeO₂:SA-nanoparticles. The study revealed that the foliar treatment with CeO₂:SA-nanoparticles alleviated the side effects of salinity by improving the physiological responses and growth-related traits of purslane plants.

The effects of fullerene on photosynthetic apparatus, chloroplast-encoded gene expression, and nitrogen assimilation in Zea mays under cobalt stress

Carbon nanostructures, such as the water-soluble fullerene (FLN) derivatives, are considered perspective agents for agriculture. FLN can be a novel nano-agent modulating plant response against stress conditions. However, the mechanism underlying the impacts of FLN on plants in agroecosystems remains unclear. Zea mays was exposed to exogenous C₆₀ -FLN applications (FLN1: 100; FLN2: 250; and FLN3: 500 mg L^-1 ) with/without cobalt stress (Co, 300 μM) for 3 days (d). In the maize chloroplasts, Co stress disrupted the photosynthetic efficiency and the expression of genes related to the photosystems (psaA and psbA). FLNs effectively improved the efficiency and photochemical reaction of photosystems. Co stress induced the accumulation of reactive oxygen species (ROS) as confirmed by ROS-specific fluorescence in guard cells. Co stress increased only chloroplastic superoxide dismutase (SOD) and peroxidase (POX). Stress triggered oxidative damages in maize chloroplasts, measured as an increase in TBARS content. In Co-stressed seedlings exposed to FLN1 and FLN2 exposures, the hydrogen peroxide (H₂ O₂ ) was scavenged through the nonenzymes/enzymes-related to the AsA-GSH cycle by preserving ascorbate (AsA) conversion, as well as GSH/GSSG and glutathione (GSH) redox state. Also, the alleviation effect of FLN3 against stress could be attributed to increased glutathione S-transferase (GST) activity and AsA regeneration. FLN applications reversed the inhibitory effects of Co stress on nitrogen assimilation. In maize chloroplasts, FLN increased the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH), nitrite reductase (NiR), and glutamine synthetase (GS), which provided conversion of inorganic nitrogen (N) into organic N. The ammonium (NH₄ ⁺ ) toxicity was removed via GS and GDH but not glutamate synthase (GOGAT). The increased NAD-GDH (deaminating) and NADH-GDH (aminating) activities indicated that GDH was needed more for NH₄ ⁺ detoxification. Therefore, FLN exposure to Co-stressed maize plants might play a role in N metabolism regarding the partitioning of N assimilates. Exogenous FLN conceivably removed Co toxicity by improving the expressions of genes related to reaction center proteins of photosystems, increasing the level of enzymes related to the defense system, and improving the N assimilation in maize chloroplasts.

The combined toxicity and mechanism of multi-walled carbon nanotubes and nano zinc oxide toward the cabbage

The natural environment is a complex system, and there is never only one kind of nanomaterial entering the environment. However, many studies only considered the plant toxicity of one kind of nanomaterial and do not consider the influence of two or more kinds of nanomaterials on plant toxicity. Multi-walled carbon nanotubes (MWCNTs) and zinc oxide nanoparticles (ZnO NPs) are two common and widely used nanomaterials in water environment, so these two kinds of nanomaterials were chosen to explore the effects of their combined toxicity on cabbage. This study investigated the toxicity of MWCNTs combined with ZnO NPs on cabbage by measuring the length of roots and stems, chlorophyll content, oxidative stress, antioxidant enzyme activity, metal element content, and root scanning electron microscopy. The toxicity of single MWCNTs toward cabbage was attributed to direct oxidative damage, while the toxicity of single ZnO NPs toward cabbage was due to the high level of zinc concentration. Moreover, ZnO NPs (10 mg/L) ameliorated MWCNTs toxicity toward cabbage by improving the activity of antioxidant enzymes. ZnO NPs (50 and 100 mg/L) because of the high content of zinc disrupted the balance of other metals in the plant and increased the toxicity of MWCNTs. In conclusion, the combined toxicity of different concentrations and types of nanomaterials should be considered for a more accurate assessment of environmental risks.

Transfer, transportation, and accumulation of cerium-doped carbon quantum dots: Promoting growth and development in wheat

New cerium-doped carbon quantum dots (CDs:Ce) were developed in this study using hydrothermal synthesis method. The small and uniform sizes and nearly spherical lattice of CDs:Ce indicate its high stability, satisfactory water solubility, and biocompatibility. Wheat was treated with Ce, CDs, and different concentrations (0.01, 0.025, 0.05, 0.1, 0.2, and 0.4 mg/mL) of CDs:Ce. The results showed that, compared with the control group, Ce, CDs, and CDs:Ce could promote the growth and development of wheat in a certain concentration range. Wheat demonstrated the optimal morphological index (compared with the control, the root number, root length, leaf length, and plant height were increased by 45%, 57%, 28%, and 46%, respectively), maximum chlorophyll content (increased by 51%) and peroxidase activity (increased by 76%), and minimum malondialdehyde content (reduced by 68%) after treatment of 0.025 mg/mL of CDs:Ce. Hence, wheat plants can adsorb and transport CDs:Ce from roots to stems and leaves through fibrovascular tissues. The majority of CDs:Ce are concentrated in roots while some accumulate in leaves. A considerable amount of CDs:Ce gather in cell walls, fibrovascular tissues, leaf veins, and stomata. CDs:Ce can be applied to agricultural production activities as a new agricultural nanofertilizer and technology of plant in vivo imaging.

The Combined Effect of ZnO and CeO2 Nanoparticles on Pisum sativum L.: A Photosynthesis and Nutrients Uptake Study

Cerium oxide nanoparticles (CeO2 NPs) and zinc oxide nanoparticles (ZnO NPs) are emerging pollutants that are likely to occur in the contemporary environment. So far, their combined effects on terrestrial plants have not been thoroughly investigated. Obviously, this subject is a challenge for modern ecotoxicology. In this study, Pisum sativum L. plants were exposed to either CeO2 NPs or ZnO NPs alone, or mixtures of these nano-oxides (at two concentrations: 100 and 200 mg/L). The plants were cultivated in hydroponic system for twelve days. The combined effect of NPs was proved by 1D ANOVA augmented by Tukey's post hoc test at p = 0.95. It affected all major plant growth and photosynthesis parameters. Additionally, HR-CS AAS and ICP-OES were used to determine concentrations of Cu, Mn, Fe, Mg, Ca, K, Zn, and Ce in roots and shoots. Treatment of the pea plants with the NPs, either alone or in combination affected the homeostasis of these metals in the plants. CeO2 NPs stimulated the photosynthesis rate, while ZnO NPs prompted stomatal and biochemical limitations. In the mixed ZnO and CeO2 treatments, the latter effects were decreased by CeO2 NPs. These results indicate that free radicals scavenging properties of CeO2 NPs mitigate the toxicity symptoms induced in the plants by ZnO NPs.

Recent insights into the impact, fate and transport of cerium oxide nanoparticles in the plant-soil continuum

The advent of the nanotechnology era offers a unique opportunity for sustainable agriculture provided that the exposure and toxicity are adequately assessed and properly controlled. The global production and application of cerium oxide nanoparticles (CeO₂-NPs) in various industrial sectors have tremendously increased. Most of the nanoparticles end up in water and soil where they interact with soil microorganisms and plants. Investigating the uptake, translocation and accumulation of CeO₂-NPs is critical for its safe application in agriculture. Plant uptake of CeO₂-NPs may lead to their accumulation in different plant tissues and interference with key metabolic processes of plants. Soil microbes can also be affected by increasing CeO₂-NPs in soil, leading to changes in the physiology and enzymatic activity of soil microorganisms. The interactions between CeO₂-NPs, microbes and plants in the agricultural system need systemic research in ecologically relevant conditions. In the present review, The uptake pathways and in-planta translocation of CeO₂-NPs,and their impact on plant morphology, nutritional values, antioxidant enzymes and molecular determinants are presented. The role of CeO₂-NPs in modifying soil microbial community in plant rhizosphere is also discussed. Overall, the review aims to provide a comprehensive account on the behaviour of CeO₂-NPs in soil-plant systems and their potential impacts on the soil microbial community and plant health.

Protective effects of cerium oxide nanoparticles in grapevine (Vitis vinifera L.) cv. Flame Seedless under salt stress conditions

High levels of soil salinity can cause substantial decline in growth and productivity of crops worldwide, thus representing a major threat to global agriculture. In recent years, engineered nanoparticles (NPs) have been deemed as a promising alternative in combating abiotic stress factors, such as salinity. In this context, the present study was designed to explore the potential of cerium oxide nanoparticles (CeO₂NPs) in alleviating salt stress in grapevine (Vitis vinifera L. cv. Flame Seedless) cuttings. Specifically, the interaction between CeO₂ NPs (25, 50 and 100 mg L^-1) and salinity (25 and 75 mM NaCl) was evaluated by assaying an array of agronomic, physiological, analytical and biochemical parameters. Treatments with CeO₂ NPs, in general, alleviated the adverse impacts of salt stress (75 mM NaCl) significantly improving relevant agronomic traits of grapevine. CeO₂ NPs significantly ameliorated chlorophyll damage under high levels of salinity. Furthermore, the presence of CeO₂ NPs attenuated salinity-induced damages in grapevine as indicated by lower levels of proline, MDA and EL; however, H₂O₂ content was not ameliorated by the presence of CeO₂ NPs under salt stress. Additionally, salinity caused substantial increases in enzymatic activities of GP, APX and SOD, compared with control plants. Similar to stress conditions, all concentrations of CeO₂ NPs triggered APX activity, while the highest concentration of CeO₂ NPs significantly increased GP activity. However, CeO₂ NPs did not significantly modify SOD activity. Considering mineral nutrient profile, salinity increased Na and Cl content as well as Na/K ratio, while it decreased K, P and Ca contents. Nevertheless, the presence of CeO₂ NPs did not lead to significant alterations in Na, K and P content of salt-stressed plants. Taken together, current findings suggest that CeO₂ NPs could be employed as promising salt-stress alleviating agents in grapevine.

Effect of nano cerium oxide on soybean (Glycine max L. Merrill) crop exposed to environmentally relevant concentrations

This study evaluated the uptake and translocation of cerium nanoparticles (CeO2 NPs) and soluble Ce(NO3)3 by soybean plants (Glycine max L. Merrill) under the whole plant life-cycle and relevant environmental concentrations, 0.062 and 0.933 mg kg-1, which represent maximal values for 2017 in agricultural soils and sludge treated soils, respectively. The experiments were carried out using a nutrient solution. Cerium was detected in the soybean roots epidermis and cortex, leaves, and grains, but it neither impaired plant development nor grain yield. The concentration of Ce in the shoot increased as a function of time for plants treated with Ce(NO3)3, while it remained constant for plants treated with CeO2 NPs. It means that CeO2 NPs were absorbed in the same rate as biomass production, which suggests that they are taken up and transported by water mass flow. Single-particle inductively coupled plasma mass spectrometry revealed clusters of CeO2 NPs in leaves of plants treated with 25 nm CeO2 NPs (ca. 30-45 nm). The reprecipitation of soluble cerium from Ce(NO3)3 within the plant was not confirmed. Finally, bioconcentration factors above one were found for the lowest concentrated treatments. Since soybean is a widespread source of protein for animals, we draw attention to the importance of evaluating the effects of Ce entrance in the food chain and its possible biomagnification.

Biostimulation and toxicity: The magnitude of the impact of nanomaterials in microorganisms and plants

Background

Biostimulation and toxicity constitute the continuous response spectrum of a biological organism against physicochemical or biological factors. Among the environmental agents capable of inducing biostimulation or toxicity are nanomaterials. On the < 100 nm scale, nanomaterials impose both physical effects resulting from the core’s and corona’s surface properties, and chemical effects related to the core’s composition and the corona’s functional groups.

Aim of Review

The purpose of this review is to describe the impact of nanomaterials on microorganisms and plants, considering two of the most studied physical and chemical properties: size and concentration.

Key Scientific Concepts of Review

Using a graphical analysis, the presence of a continuous biostimulation-toxicity spectrum is shown considering different biological responses. In microorganisms, the results showed high susceptibility to nanomaterials. Simultaneously, in plants, a hormetic response was found related to nanomaterials concentration and, in a few cases, a positive response in the smaller nanomaterials when these were applied at a higher level. With the above, it is concluded that: (1) microorganisms are more susceptible to nanomaterials than plants, (2) practically all nanomaterials seem to induce responses from biostimulation to toxicity in plants, and (3) the kind of response observed will depend in a complex way on the nanomateriaĺs physical and chemical characteristics, of the biological species with which they interact, and of the form and route of application and on the nature of the medium -soil, soil pore water, and biological surfaces- where the interaction occurs.

Carotenoids from Cyanobacteria: A Biotechnological Approach for the Topical Treatment of Psoriasis

In this study, five cyanobacteria strains (Alkalinema aff. pantanalense LEGE15481, Cyanobium gracile LEGE12431, Nodosilinea (Leptolyngbya) antarctica LEGE13457, Cuspidothrix issatschenkoi LEGE03282 and Leptolyngbya-like sp. LEGE13412) from the Blue Biotechnology and Ecotoxicology Culture Collection (LEGE CC) of CIIMAR were explored for their biotechnological potential in the treatment of psoriasis. Different extracts were characterized for their pigment profile by HPLC-PDA. The antioxidant potential of the extracts was assessed against the superoxide anion radical (O₂^•-). Their anti-inflammatory and antiproliferative potential was assessed in vitro using the macrophages RAW 264.7 and the human keratinocytes HaCaT as cell-line models, respectively. Terrestrial and freshwater strains presented the highest carotenoid content (33193-63926 μg/g dry extract), with all-trans-β-carotene, zeaxanthin, echinenone and lutein derivatives being the most abundant carotenoids. Acetone was the most effective solvent for pigment extraction. The acetone extracts presented the lowest IC₅₀ values (0.29-0.38 mg dry extract/mL) regarding O₂^•- scavenging, and revealed anti-inflammatory potential, with N. antarctica LEGE13457, A. pantanalense LEGE15481 and Leptolyngbya-like sp. LEGE13412 reducing the nitric oxide (NO) in RAW 264.7 cell culture medium in about 25% (p < 0.05). With the exception of A. pantanalense LEGE15481, all the extracts significantly reduced keratinocyte proliferation (p < 0.05), demonstrating a selective toxicity among the different cell lines. Overall, Leptolyngbya-like sp. LEGE13412 and N. antarctica LEGE13457 seem promising for further exploitation in the framework of psoriasis, due to their antioxidant, anti-inflammatory and antiproliferative potential.