Iron oxide nanoparticles doped biochar ameliorates trace elements induced phytotoxicity in tomato by modulation of physiological and biochemical responses: Implications for human health risk

Nano-Manganese and H2S Signalling Improve Rapeseed Tolerance to Chromium Stress by Regulating Cellular Metabolism and Downstream Pathways

A cutting-edge smart nano-hybrid technology, offering potential benefits for plants, has recently been developed to address the pervasive issue of heavy metal pollution. This study explored the potential of this technology in mitigating chromium (Cr) stress in rapeseed using a nano-based system that integrates 100 μM hydrogen sulphide (H2S) and 50 μM manganese nanoparticles (Mn-NPs). This strategy reveals Cr-stress tolerance mechanisms through physiological assessments and transcriptome data analysis. The results demonstrated that Cr stress substantially inhibited rapeseed growth while increasing oxidative damage markers (MDA and ROS levels). Conversely, Mn-NP and H2S co-treatment significantly mitigated these effects, as shown by: (1) restored growth metrics, (2) improved photosynthetic performance and membrane integrity, (3) optimized Mn/H2S homeostasis, and (4) reduced tissue Cr accumulation. The reduction in Cr content was attributed to enhanced Cr-detoxification mechanisms, driven by the upregulation of enzymatic antioxidant activities, like superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase. Transcriptomic profiling revealed marked upregulation of genes involved in core metabolic processes, including photosynthetic pathways, carbon assimilation, secondary metabolite biosynthesis, inositol/phosphatidylinositol signalling systems, and stress-response networks. Under Cr stress, Mn-NP and H2S co-treated rapeseed plants displayed enhanced tolerance, highlighting the crucial role of these signalling agents in activating Cr-defence mechanisms. Our findings demonstrate that the integration of nanotechnology and gasotransmitter signalling molecule H2S presents a novel strategy for enhancing heavy metal tolerance and plant productivity in contaminated soils.

Nanoparticles as catalysts of agricultural revolution: enhancing crop tolerance to abiotic stress: a review

Ensuring global food security and achieving sustainable agricultural productivity remains one of the foremost challenges of the contemporary era. The increasing impacts of climate change and environmental stressors like drought, salinity, and heavy metal (HM) toxicity threaten crop productivity worldwide. Addressing these challenges demands the development of innovative technologies that can increase food production, reduce environmental impacts, and bolster the resilience of agroecosystems against climate variation. Nanotechnology, particularly the application of nanoparticles (NPs), represents an innovative approach to strengthen crop resilience and enhance the sustainability of agriculture. NPs have special physicochemical properties, including a high surface-area-to-volume ratio and the ability to penetrate plant tissues, which enhances nutrient uptake, stress resistance, and photosynthetic efficiency. This review paper explores how abiotic stressors impact crops and the role of NPs in bolstering crop resistance to these challenges. The main emphasis is on the potential of NPs potential to boost plant stress tolerance by triggering the plant defense mechanisms, improving growth under stress, and increasing agricultural yield. NPs have demonstrated potential in addressing key agricultural challenges, such as nutrient leaching, declining soil fertility, and reduced crop yield due to poor water management. However, applying NPs must consider regulatory and environmental concerns, including soil accumulation, toxicity to non-target organisms, and consumer perceptions of NP-enhanced products. To mitigate land and water impacts, NPs should be integrated with precision agriculture technologies, allowing targeted application of nano-fertilizers and nano-pesticides. Although further research is necessary to assess their advantages and address concerns, NPs present a promising and cost-effective approach for enhancing food security in the future.

Remediation of chromium contaminated water and soil by nitrogen and iron doped biochars

Chromium (Cr) is a toxic and redox-sensitive contaminant that has accumulated in water and soil systems, becoming a serious issue worldwide. Producing novel remedial materials with enhanced removal efficiency from plentiful available sources is a pleasing aspect for Cr removal. This review explores valuable insights into the production of nitrogen doped biochar (N/BC), iron doped biochar (Fe/BC), and iron‑nitrogen doped biochar (Fe-N/BC) and their application for Cr (trivalent (Cr(III)) and hexavalent (Cr(VI)) removal. Specifically, this review focuses on conferring knowledge about producing environmentally friendly N and Fe doped BCs with enhanced surface functionalities, physicochemical properties, and holding capacities for removing Cr(VI) through adsorption and reduction. Affecting factors for Cr(VI) removal by N/BC, Fe/BC, and Fe-N/BC through reviewing the literature on the reaction system pH, mass transfer driving forces, effect of coexisting ions, BC production conditions, and redox potential are overviewed. Notably, isotherm and kinetic models and removal mechanisms of Cr(VI) by N/BC, Fe/BC, and Fe-N/BC with the assistance of characterization analyses, experimental results, and computational modeling methods are explored. Finally, the regeneration, cost evaluation, and environmental implications, as well as the real-world applications and environmental risks of N/BC, Fe/BC, and Fe-N/BC are discussed. This review shows that N and Fe doped BCs are remedial materials that can potentially remediate Cr(VI) contaminated water and soil.

Biochar and nanoscale silicon synergistically alleviate arsenic toxicity and enhance productivity in chili peppers (Capsicum annuum L.)

Arsenic (As) contamination in agricultural soils threatens crop productivity and food safety. In this study, we examined the efficacy of biochar (BC) and silicon nanoparticles (SiNPs) as environmentally sustainable soil amendments to alleviate As toxicity in chili (Capsicum annuum L.) plants. Our findings revealed that As stress severely inhibited the growth parameters of Capsicum annuum L., and subsequently reduced yield. However, the application of BC and SiNPs into the contaminated soil significantly reversed these negative effects, promoting plant length and biomass, particularly when applied together in a synergistic manner. Arsenic stress led to increased oxidative damage, as evidenced by a 29% increase in leaf malondialdehyde content as compared to the healthy plants. Nevertheless, the synergistic (BC + SiNPs) application effectively modulated antioxidant enzyme activity, resulting in a remarkable 55% and 66% enhancement in the superoxide dismutase and catalase levels, respectively, boosting chili's resistance against oxidative stress. Similarly, BC + SiNPs amendments improved photosynthesis by 52%, stomatal conductance by 39%, soluble sugars by 42%, and proteins by 30% as compared with those of control treatment. Additionally, the combined BC + SiNPs application significantly reduced root As content by 61% and straw As by 37% as compared with the control one. Transmission electron microscopy confirmed that the synergistic use of BC and SiNPs preserved chili leaf ultrastructure, shielding against As-induced damage. Overall, the supplementation of contaminated soil with BC and SiNPs was proved to be a sustainable strategy for mitigating As toxicity in chili peppers, enhancing plant growth, physiology, and yield, and thereby food safety.

Multivariate characterization of salicylic acid and potassium induced physio-biochemical and phytoremediation responses in quinoa exposed to lead and cadmium contamination

The levels of soils pollutants such as lead (Pb) and cadmium (Cd) have significantly increased recently resulting in ecological disturbances and threatening crop production. Various amendments have been employed to enhance the tolerance of crops to withstand Cd and Pb stresses. However, the role of combined application of potassium (K) and of salicylic acid (SA) for Cd and Pb stress mitigation and phytoremediation by quinoa (Chenopodium quinoa Willd) has not been comprehended well. In the present study, the effect of 10 mM K and 0.1 mM SA was tested on the quinoa plants subjected to 250 μM Pb and/or 100 μM Cd. The Pb and Cd treatments were applied separately or together. Phytotoxicity induced by Pb and Cd resulted in drastic decrease (>60%) in chlorophyll contents, stomatal conductance, and plant biomass. The collective treatment of Pb and Cd induced an increase in the concentration of hydrogen peroxide (13-fold) and lipid peroxidation (16-fold) that resulted in a 61% reduction in membrane stability. The application of 10 mM K and/or 0.1 mM SA was remarkable in mitigating the adverse effect of Pb and Cd. The reduction in plant biomass was 17% when 10 mM K and 0.1 mM SA were applied together under the combined treatment of both the metals. The simultaneous application of K and SA effectively mitigated oxidative stress by enhancing the activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase by 12, 10, 7 and 10-folds respectively. The positive effect of K and SA on these attributes resulted in a remarkable reduction in metal accumulation and translocation and lipid peroxidation. The stressed plants supplemented with K and SA exhibited a significant improvement in the membrane stability index, chlorophyll content, and stomatal conductance. This study concluded that the combined application of K and SA could be a good approach for reducing Pb and Cd phytotoxicity in quinoa and enhancing their phytostabilization potential in the contaminated soils.

Nanoparticles and root traits: mineral nutrition, stress tolerance and interaction with rhizosphere microbiota

MAIN CONCLUSION

This review article highlights a broader perspective of NPs and plant-root interaction by focusing on their beneficial and deleterious impacts on root system architecture (RSA). The root performs a vital function by securing itself in the soil, absorbing and transporting water and nutrients to facilitate plant growth and productivity. In dicots, the architecture of the root system (RSA) is markedly shaped by the development of the primary root and its branches, showcasing considerable adaptability in response to changes in the environment. For promoting agriculture and combating global food hunger, the use of nanoparticles (NPs) may be an exciting option, for which it is essential to understand the behaviour of plants under NPs exposure. The nature of NPs and their physicochemical characteristics play a significant role in the positive/negative response of roots and shoots. Root morphological features, such as root length, root mass and root development features, may regulated positively/negatively by different types of NPs. In addition, application of NPs may also enhance nutrient transport and soil fertility by the promotion of soil microorganisms including plant growth-promoting rhizobacteria (PGPRs) and also soil enzymes. Interestingly the interaction of nanomaterials (NMs) with rhizospheric bacteria can enhance plant development and soil health. However, some studies also suggested that the increased use of several types of engineered nanoparticles (ENPs) may disrupt the equilibrium of the soil-root interface and unsafe morphogenesis by causing the browning of roots and suppressing the growth of root and soil microbes. Thus, this review article has sought to compile a broader perspective of NPs and plant-root interaction by focusing on their beneficial or deleterious impacts on RSA.

Potential of amino acids-modified biochar in mitigating the soil Cu and Ni stresses - Targeting the tomato growth, physiology and fruit quality

Trace heavy metals (HMs) such as copper (Cu) and nickel (Ni) are toxic to plants, especially tomato at high levels. In this study, biochar (BC) was treated with amino acids (AA) to enhance amino functional groups, which effectively alleviated the adverse effects of heavy metals (HMs) on tomato growth. Hence, this study aimed to evaluate the effect of glycine and alanine modified BC (GBC/ABC) on various tomato growth parameters, its physiology, fruit yield and Cu/Ni uptake under Cu and Ni stresses. In a pot experiment, there was 21 treatments with three replications having two rates of simple BC and glycine/alanine enriched BC (0.5% and 1% (w/w). Cu and Ni stresses were added at 150 mg kg-1 respectively. Plants were harvested after 120 days of sowing and subjected to various analysis. Under Cu and Ni stresses, tomato roots accumulated more Cu and Ni than shoots and fruits, while GBC and ABC application significantly enhanced the root and shoot dry weight irrelevant to the stress conditions. Both rates of GBC decreased the malondialdehyde and hydrogen peroxide levels in plants. The addition of 0.5% GBC with Cu enhanced the tomato fruit dry weight by 1.3 folds in comparison to the control treatment; while tomato fruit juice content also increased (50%) in the presence of 0.5% GBC with Ni as compared to control. In summary, these results demonstrated that lower rate of GBC∼0.5% proved to be the best in mitigating the Cu and Ni stress on tomato plant growth by enhancing the fruit production.

Silicon-nanoparticles loaded biochar for soil arsenic immobilization and alleviation of phytotoxicity in barley: Implications for human health risk

Arsenic (As)-induced environmental pollution and associated health risks are recognized on a global level. Here the impact of cotton shells derived biochar (BC) and silicon-nanoparticles loaded biochar (nano-Si-BC) was explored on soil As immobilization and its phytotoxicity in barley plants in a greenhouse study. The barley plants were grown in a sandy loam soil with varying concentrations of BC and nano-Si-BC (0, 1, and 2%), along with different levels of As (0, 5, 10, and 20 mg kg-1). The FTIR spectroscopy, SEM-EDX, and XRD were used to characterize BC and nano-Si-BC. Results revealed that As treatment had a negative impact on barley plant development, grain yield, physiology, and anti-oxidative response. However, the addition of nano-Si-BC led to a 71% reduction in shoot As concentration compared to the control with 20 mg kg-1 of As, while BC alone resulted in a 51% decline. Furthermore, the 2% nano-Si-BC increased grain yield by 94% compared to control and 28% compared to BC. The addition of 2% nano-Si-BC to As-contaminated soil reduced oxidative stress (34% H2O2 and 48% MDA content) and enhanced plant As tolerance (92% peroxidase and 46% Ascorbate peroxidase activity). The chlorophyll concentration in barley plants decreased due to oxidative stress. Additionally, the incorporation of 2% nano-Si-BC resulted in a 76% reduction in water soluble and NaHCO3 extractable As. It is concluded that the use of BC or nano-Si-BC in As contaminated soil for barley resulted in a low human health risk (HQ < 1), as it effectively immobilized As and promoted higher activity of antioxidants.

Remediation of soil polluted with Pb and Cd and alleviation of oxidative stress in Brassica rapa plant using nanoscale zerovalent iron supported with coconut-husk biochar

Accumulation of toxic elements by plants from polluted soil can induce the excessive formation of reactive oxygen species (ROS), thereby causing retarded plants' physiological attributes. Several researchers have remediated soil using various forms of zerovalent iron; however, their residual impacts on oxidative stress indicators and health risks in leafy vegetables have not yet been investigated. In this research, nanoscale zerovalent iron supported with coconut-husk biochar (nZVI-CHB) was synthesized through carbothermal reduction process using Fe2O3 and coconut-husk. The stabilization effects of varying concentrations of nZVI-CHB and CHB (250 and 500 mg/kg) on cadmium (Cd) and lead (Pb) in soil were analyzed, and their effects on toxic metals induced oxidative stress, physiological properties, and antioxidant defence systems of the Brassica rapa plant were also checked. The results revealed that the immobilization of Pb and Cd in soil treated with CHB was low, leading to a higher accumulation of metals in plants grown. However, nZVI-CHB could significantly immobilize Pb (57.5-62.12%) and Cd (64.1-75.9%) in the soil, leading to their lower accumulation in plants below recommended safe limits and eventually reduced carcinogenic risk (CR) and hazard quotient (HQ) for both Pb and Cd in children and adults below the recommended tolerable range of <1 for HQ and 10-6 - 10-4 for CR. Also, a low dose of nZVI-CHB significantly mitigated toxic metal-induced oxidative stress in the vegetable plant by inhibiting the toxic metals uptake and increasing antioxidant enzyme activities. Thus, this study provided another insightful way of converting environmental wastes to sustainable adsorbents for soil remediation and proved that a low-dose of nZVI-CHB can effectively improve soil quality, plant physiological attributes and reduce the toxic metals exposure health risk below the tolerable range.

Iron enriched quinoa biochar enhances Nickel phytoremediation potential of Helianthus annuus L. by its immobilization and attenuation of oxidative stress: implications for human health

The present study was performed to assess Ni-immobilization and the phytoremediation potential of sunflower by the application of quinoa stalks biochar (QSB) and its magnetic nanocomposite (MQSB). The QSB and MQSB were characterized with FTIR, SEM, EDX, and XRD to get an insight of their surface properties. Three-week-old seedlings of sunflower were transplanted to soil spiked with Ni (0, 15, 30, 60, 90 mg kg-1), QSB and MQSB (0, 1, and 2%) in the wire house under natural conditions. The results showed that increasing Ni levels inhibited sunflower growth and yield due to the high production of reactive oxygen species (ROS) and lipid peroxidation. Enzyme activities like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POX) also increased as Ni levels increased. However, the application of QSB and MQSB reduced Ni uptake, root-shoot, and shoot-seed translocation and decreased the generation of ROS, and lowered the activity of SOD, CAT, APX, and POX, leading to improved growth and yield, especially with MQSB. This was verified through SEM, EDX, XRD, and FTIR. It can be concluded that QSB and MQSB can effectively enhance Ni-tolerance in sunflowers and mitigate oxidative stress and human health risks.

Efficacy of metallic nanoparticles in attenuating the accumulation and toxicity of chromium in plants: Current knowledge and future perspectives

Nanoparticles have emerged as cutting-edge technology for the improvement of crops yield and safe cultivation of agricultural plants, especially in peripheral areas impaired with toxic heavy metals including chromium (Cr). The uncontrolled release of Cr mainly from anthropogenic factors is substantially polluting the surrounding environment, thereby extensively accumulated in soil-plant system. The excessive Cr-accretion in plant tissues disturbed the morph-physiological, biochemical, cellular, metabolic and molecular processes, and impaired the plants functionality. Therefore, it is obligatory to restrict the accumulation and toxic effects of Cr in plant organs. Recent studies on metallic nanoparticles (MNPs) such as iron oxide, silicon dioxide, copper oxide and zinc oxide have approved their efficacy as potent pool to curb the Cr-induced phytotoxicities and improved the plant tolerance. MNPs attenuated the bioaccumulation and phytotoxicity of Cr by utilizing key mechanisms such as improved photosynthetic machinery, regulation of cellular metabolites, greater chelation capacity to bind with Cr, release of corresponding metallic ions, upsurge in the uptake of essential nutrients, activation of antioxidants (enzymatic and non-enzymatic), reduction in oxidative stress, and cellular injuries, thus improvement in plant growth performances. We have briefly discussed the current knowledge and research gaps in existing literature along with possible recommendations for future research. Overall, Cr-detoxification by MNPs may depends upon the target plant species, Cr speciation, plant growth stages (seedling, vegetative and ripening etc.), treatment methods (foliar spray, seed priming and nutrient solution etc.), type, size, dose and coating of applied MNPs, and conditions (hydroponic and soil environment etc.). This review would help plant scientists to develop MNPs based strategies such as nano-fertilizers to alleviate the Cr-accumulation and its toxic impacts. This may leads to safe and healthy food production. The review outcomes can provide new horizons for research in the applications of MNPs for the sustainable agriculture.

Silicon-nanoparticles doped biochar is more effective than biochar for mitigation of arsenic and salinity stress in Quinoa: Insight to human health risk assessment

The increasing contamination of soil with arsenic (As), and salinity has become a menace to food security and human health. The current study investigates the comparative efficacy of plain biochar (BC), and silicon-nanoparticles doped biochar (SBC) for ameliorating the As and salinity-induced phytotoxicity in quinoa (Chenopodium quinoa Willd.) and associated human health risks. Quinoa was grown on normal and saline soils (EC_e 12.4 dS m^-1) contaminated with As (0, 20 mg kg^-1) and supplemented with 1% of BC or SBC. The results demonstrated that plant growth, grain yield, chlorophyll contents, and stomatal conductance of quinoa were decreased by 62, 44, 48, and 66%, respectively under the blended stress of As and salinity as compared to control. Contrary to this, the addition of BC to As-contaminated saline soil caused a 31 and 25% increase in plant biomass and grain yield. However, these attributes were increased by 45 and 38% with the addition of SBC. The H₂O₂ and TBARS contents were enhanced by 5 and 10-fold, respectively under the combined stress of As and salinity. The SBC proved to be more efficient than BC in decreasing oxidative stress through overexpressing of antioxidant enzymes. The activities of superoxide dismutase, peroxidase, and catalase were enhanced by 5.4, 4.6, and 11-fold with the addition of SBC in As-contaminated saline soil. Contamination of grains by As revealed both the non-carcinogenic and carcinogenic risks to human health, however, these effects were minimized with the addition of SBC. As accumulation in grains was decreased by 65-fold and 25-fold, respectively for BC and SBC in addition to As-contaminated saline soil. The addition of SBC to saline soils contaminated with As for quinoa cultivation is an effective approach for decreasing the food chain contamination and improving food security. However, more research is warranted for the field evaluation of the effectiveness of SBC in abating As uptake in other food crops cultivated on As polluted normal and salt-affected soils.

Comparative efficiency of silica gel, biochar, and plant growth promoting bacteria on Cr and Pb availability to Solanum melongena L. in contaminated soil irrigated with wastewater

Crop irrigation with untreated wastewater is a routine practice in developing countries that causes multiple human health consequences. A comparative study was performed to regulate total Cr and Pb stress in soil and Solanum melongena L. plant. For this purpose, 0.2% chitosan polymerized silica gel (CP-silica gel), 1.5% zinc-enriched biochar (ZnBc), and three bacterial species such as Trichococcus sp. (B1), Pseudomonas alcaligenes (B2), and Bacillus subtilis (B3) were selected. Initially, a biosorption trial was conducted to test the heavy metal removal efficiency of three bacterial species B1, B2, and B3 for 24 h. Hence, B3 showed maximum Cr and Pb removal efficiency among the studied bacterial isolates. Then, a pot study was conducted with 12 different treatments having three replicates. After harvesting, different growth and biochemical parameters such as chlorophyll concentration, proteins, phenolics, reactive oxygen species, and antioxidant enzymes were analyzed. The results demonstrated that wastewater application significantly (p ≤ 0.01) reduced the fresh and dry weights of the root, stem, and leaves due to high total Cr and Pb toxicity. However, CP-silica gel and ZnBc treatments performed best when applied in combination with B3. The concentration of leaf total Cr was significantly decreased (91 and 85%) with the application of ZnBc + B3 and CP-Silica gel + B3, respectively, as compared to control. There was a reduction in stem hydrogen peroxide (87%) and malondialdehyde (81%) recorded with CP-silica gel + B3 treatment due to enhanced activities of antioxidant enzymes viz. ascorbate peroxidase (6-folds) and catalase (7-folds) relative to control. Similarly, leaf total phenolics (3-folds) and protein (6-folds) contents were enhanced with CP silica gel+B3 application relative to control. Overall, CP-silica gel and ZnBc with B3 application proved to be the most appropriate treatments and can be used in developing countries to limit the deleterious effects of total Cr and Pb pollution.