Effect of titanium dioxide nanoparticles and co-composted biochar on growth and Cd uptake by wheat plants: A field study

Combined application of zinc oxide and iron nanoparticles enhanced Red Sails lettuce growth and antioxidants enzymes activities while reducing the chromium uptake by plants grown in a Cr-contaminated soil

Soil contamination with chromium (Cr) is becoming a primary ecological and health concern, specifically in the Kasur and Sialkot regions of Pakistan. The main objective of the current study was to evaluate the impact of foliar application of zinc oxide nanoparticles (ZnO NPs) (0, 25, 50, 100 mg L-1) and Fe NPs (0, 5, 10, 20 mg L-1) in red sails lettuce plants grown in Cr-contaminated soil. Our results showed that both ZnO and Fe NPs improved plant growth, and photosynthetic attributes by minimizing oxidative stress in lettuce plants through the stimulation of antioxidant enzyme activities. At ZnO NPs (100 mgL-1), dry weights of shoots and roots and fresh weights of shoots and roots were improved by 53%, 58%, 34%, and 45%, respectively, as compared to the respective control plants. The Fe NPs treatment (20 mgL-1) increased the dry weight of shoots and the roots and fresh weights of shoots and roots by 53%, 76%, 42%, and 70%, respectively. Application of both NPs reduced the oxidative stress caused by Cr, as evident by the findings of the current study, i.e., at the ZnO NPs (100 mgL-1) and Fe NPs (20 mgL-1), the EL declined by 32% and 44%, respectively, in comparison with respective control plants. Moreover, Fe and ZnO NPs enhanced the Fe and Zn contents in red sails lettuce plants. Application of ZnO NPs at 100 mg L-1 and Fe NPs at 20 mg L-1, improved the Zn and Fe contents in plant leaves by 86%, and 68%, respectively, as compared to the control plants. This showed that the exogenous application of these NPs helped in Zn and Fe fortification in plants. At similar of concenteration ZnO NPs, CAT and APX activities were improved by 52% and 53%, respectively. Similarly, the POD contents were improved by 17% and 45% at 5 and 10 mg/L of Fe NPs. Furthermore, ZnO and Fe NPs limited the Cr uptake by plants, and the concentration of Cr in the leaves of lettuce was under the threshold limit. The exogenous application of ZnO NPs (100 mg L-1) and Fe NPs (20 mg L-1) reduced the Cr uptake in the leaves of red sails lettuce by 57% and 51%, respectively. In conclusion, ZnO and Fe NPs could be used for the improvement of plant growth and biomass as well as nutrient fortification in stressed environments. These findings not only underscore the efficacy of nanoparticle-assisted phytoremediation but also highlight its broader implications for sustainable agriculture and environmental health. However, future studies on other crops with molecular-level investigations are recommended for the validation of the results.

Integrated physiological and transcriptomic analyzes reveal the duality of TiO2 nanoparticles on alfalfa (Medicago sativa L.)

Alfalfa (Medicago sativa L.) is a feed crop due to its rich nutrition and high productivity. The utilization of titanium oxide nanoparticles (TiO2 NPs) brings benefits to agricultural production but also has potential hazards. To investigate the duality and related mechanism of TiO2 NPs on alfalfa, its different doses including 0, 50, 100, 200, 500, and 1000 mg L- 1 (CK, Ti-50, Ti-100, Ti-200, Ti-500, and Ti-1000) were sprayed on leaves. The results showed that greater doses of TiO2 NPs (500 and 1000 mg L-1) negatively affected the physiological parameters, including morphology, biomass, leaf ultrastructure, stomata, photosynthesis, pigments, and antioxidant ability. However, 100 mg L-1 TiO2 NPs revealed an optimal positive effect; compared with the CK, it dramatically increased plant height, fresh weight, and dry weight by 22%, 21%, and 41%, respectively. Additionally, TiO2 NPs at low doses significantly protected leaf tissue, promoted stomatal opening, and enhanced the antioxidant system; while higher doses had phytotoxicity. Hence, TiO2 NPs are dose-dependent on alfalfa. The transcriptomic analysis identified 4625 and 2121 differentially expressed genes (DEGs) in the comparison of CK vs. Ti-100 and CK vs. Ti-500, respectively. They were mainly enriched in photosynthesis, chlorophyll metabolism, and energy metabolism. Notably, TiO2 NPs-induced phytotoxicity on photosynthetic parameters happened concurrently with the alterations of the genes involved in the porphyrin and chlorophyll metabolism and carbon fixation in photosynthetic organisms in the KEGG analysis. Similarly, it affected the efficiency of alfalfa energy transformation processes, including pyruvate metabolism and chlorophyll synthesis. Several key related genes in these pathways were validated. Therefore, TiO2 NPs have positive and toxic effects by regulating morphology, leaf ultrastructure, stomata, photosynthesis, redox homeostasis, and genes related to key pathways. It is significant to understand the duality of TiO2 NPs and cultivate varieties resistant to nanomaterial pollution.

Mitigating cadmium accumulation and toxicity in plants: The promising role of nanoparticles

Cadmium (Cd) is a highly toxic heavy metal that adversely affects humans, animals, and plants, even at low concentrations. It is widely distributed and has both natural and anthropogenic sources. Plants readily absorb and distribute Cd in different parts. It may subsequently enter the food chain posing a risk to human health as it is known to be carcinogenic. Cd has a long half-life, resulting in its persistence in plants and animals. Cd toxicity disrupts crucial physiological and biochemical processes in plants, including reactive oxygen species (ROS) homeostasis, enzyme activities, photosynthesis, and nutrient uptake, leading to stunted growth and reduced biomass. Although plants have developed defense mechanisms to mitigate these damages, they are often inadequate to combat high Cd concentrations, resulting in yield losses. Nanoparticles (NPs), typically smaller than 100 nm, possess unique properties such as a large surface area and small size, making them highly reactive compared to their larger counterparts. NPs from diverse sources have shown potential for various agricultural applications, including their use as fertilizers, pesticides, and stress alleviators. Recently, NPs have emerged as a promising strategy to mitigate heavy metal stress, including Cd toxicity. They offer advantages, such as efficient absorption by crop plants, the reduction of Cd uptake, and the enhancement of mineral nutrition, antioxidant defenses, photosynthetic parameters, anatomical structure, and agronomic traits in Cd-stressed plants. The complex interaction of NPs with calcium ions (Ca2+), intracellular ROS, nitric oxide (NO), and phytohormones likely plays a significant role in alleviating Cd stress. This review aims to explore the positive impacts of diverse NPs in reducing Cd accumulation and toxicity while investigating their underlying mechanisms of action. Additionally, it discusses research gaps, recent advancements, and future prospects of utilizing NPs to alleviate Cd-induced stress, ultimately promoting improved plant growth and yield.

Alleviated lead toxicity in rice plant by co-augmented action of genome doubling and TiO2 nanoparticles on gene expression, cytological and physiological changes

Lead is a very toxic and futile heavy metal for rice plants because of its injurious effects on plant growth and metabolic processes. Polyploidy or whole genome doubling increases the ability of plants to withstand biotic and abiotic stress. Considering the beneficial effects of nanoparticles and tetraploid rice, this research was conducted to examine the effectiveness of tetraploid and titanium dioxide nanoparticles (TiO2 NPs) in mitigating the toxic effects of lead. A diploid (E22-2x) and it's tetraploid (T-42) rice line were treated with Pb (200 μM) and TiO2 NPs (15 mg L-1). Lead toxicity dramatically reduced shoot length (16 % and 4 %) and root length (17 % and 9 %), biological yield (55 % and 36 %), and photosynthetic activity, as evidenced by lower levels of chlorophyll a and b (30 % and 9 %) in E-22 and T-42 rice cultivars compared to the control rice plants, respectively. Furthermore, lead toxicity amplified the levels of reactive oxygen species (ROS), such as malondialdehyde and H2O2, while decreasing activities of all antioxidant enzymes, such as superoxidase, peroxidase, and glutathione predominately in the diploid cultivar. Transmission electron microscopy and semi-thin section observations revealed that Pb-treated cells in E22-2x had more cell abnormalities than T-42, such as irregularly shaped mitochondria, cell wall, and reduced root cell size. Polyploidy and TiO2 reduced Pb uptake in rice cultivars and expression levels of metal transporter genes such as OsHMA9 and OsNRAMP5. According to the findings, genome doubling alleviates Pb toxicity by reducing Pb accumulation, ROS, and cell damage. Tetraploid rice can withstand the toxic effect of Pb better than diploid rice, and TiO2 NPs can alleviate the toxic impact of Pb. Our study findings act as a roadmap for future research endeavours, directing the focus toward risk management and assessing long-term impacts to balance environmental sustainability and agricultural growth.

Effect of green-synthesized copper oxide nanoparticles on growth, physiology, nutrient uptake, and cadmium accumulation in Triticum aestivum (L.)

Cadmium (Cd) stress in crops has been serious concern while little is known about the copper oxide nanoparticles (CuO NPs) effects on Cd accumulation by crops. This study investigated the effectiveness of CuO NPs in mitigating Cd contamination in wheat (Triticum aestivum L.) cultivation through a pot experiment, presenting an eco-friendly solution to a critical agricultural concern. The CuO NPs, synthesized using green methods, exhibited a circular shape with a crystalline structure and a particle size ranging from 8 to 12 nm. The foliar spray of CuO NPs was applied in four different concentrations i.e. control, 25, 50, 75, 100 mg/L. The obtained data demonstrated that, in comparison to the control group, CuO NPs had a beneficial influence on various growth metrics and straw and grain yields of T. aestivum. The green CuO NPs improved T. aestivum growth and physiology under Cd stress, enhanced selected enzyme activities, reduced oxidative stress, and decreased malondialdehyde levels in the T. aestivum plants. CuO NPs lowered Cd contents in T. aestivum tissues and boosted the uptake of essential nutrients from the soil. Overall, foliar applied CuO NPs were effective in minimizing Cd contents in grains thereby reducing the health risks associated with Cd excess in humans. However, more in depth studies with several plant species and application methods of CuO NPs are required for better utilization of NPs in agricultural purposes.

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.

Green synthesis and characterization of silver and copper nanoparticles and their use as an effective adsorbent for chromium removal and recovery from wastewater

Chromium (Cr) is one of the hazardous heavy metals that is naturally carcinogenic and causes various health problems. Metallic nanoparticles such as silver and copper nanoparticles (Ag NPs and Cu NPs) have gained great attention because of their unique chemical, physical, and biological attributes, serving diverse and significant role in various useful and sustainable applications. In the present study, both of these NPs were synthesized by green method in which Azadirachta indica plant extract was used. These nanoparticles were characterized by using advanced instrumental techniques such as Fourier transmission infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope attached with energy-dispersive spectroscopy (SEM-EDS), and elemental mapping. These environmentally friendly nanoparticles were utilized for the batch removal of Cr from the wastewater. For analysis of adsorption behaviour, a range of kinetic isotherm models (Freundlich, Temkin, Dubinin, and Langmuir) and kinetic models (pseudo-first-order and pseudo-second-order) were used for the Cu-NPs and Ag-NPs. Cu NPs exhibited the highest Cr removal efficiency (96%) within a contact time of 10-15 min, closely followed by Ag NPs which achieved a removal efficiency of 94% under the similar conditions. These optimal outcomes were observed at a sorbent dose of 0.5 g/L for Ag NPs and 0.7 g/L for Cu NPs. After effectively capturing Cr using these nanoparticles, the sorbates were examined through SEM-EDX analysis to observe how much Cr metal was attached to the nanoparticles, potentially for future use. The analysis found that Ag-NPs captured 18% of Cr, while Cu-NPs captured 12% from the aqueous solution. More precise experimental conditions are needed for higher Cr removal from wastewater and determination of the best conditions for industrial-level Cr reuse. Although nanomaterial exhibit high efficiency and selectivity for Cr removal and recovery from wastewater, more research is necessary to optimize their synthesis and performance for industrial-scale applications and develop efficient methods for Cr removal and recovery.

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.

Nitric oxide induces antioxidant machinery, PSII functioning and artemisinin biosynthesis in Artemisia annua under cadmium stress

Soil contamination by heavy metals poses a significant environmental challenge, as the practical implementation of existing remediation technologies in the field has encountered numerous obstacles. This has necessitated the requirement of finding alternate solutions to reduce the harm caused to plants. In this study, nitric oxide (NO) was investigated for its potential to reduce cadmium (Cd) toxicity in A. annua plants. Although NO plays a vital role in the growth and development of plants, information on its role in reducing abiotic stress in plants is limited. A. annua plants were exposed to 20 and 40 mg/kg Cd regardless of the addition of exogenous sodium nitroprusside (SNP), a NO donor, at 200 µM concentration. Results showed that SNP treatment improved plant growth, photosynthesis, chlorophyll fluorescence, pigment content, and artemisinin production while reducing Cd accumulation and improving membrane stability in A. annua during Cd stress. The results demonstrated that NO can effectively reverse Cd-induced damage in A. annua by modulating the antioxidant system, maintaining redox homeostasis, and improving photosynthetic performance and different fluorescence parameters such as Fv/Fm, ФPSII, and ETR. The supplementation of SNP caused a substantial improvement in chloroplast ultrastructure, stomatal behavior, and different attributes relate to glandular secretory trichomes, which in turn increased artemisinin production; 14.11 % in plants exposed to Cd stress of 20 mg/kg. Our findings highlight that NO could be useful in mediating the repair of Cd-induced damage to A. annua, and suggest that it may play a critical role in plant signaling networks, improving plant adaptability to Cd stress. The results have important implications for developing new strategies to mitigate the negative impacts of environmental contaminants on plant health, and ultimately, the ecosystem.