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Coastal areas are facing increasing heavy metal contamination from various human activities, posing a severe threat to aquatic and coastal biodiversity. Mangroves, abundant in coastal and marine ecosystems, are particularly vulnerable to the accumulation of toxic inorganic pollutants and heavy metals (HMs). Mangroves have proved to be effective in mitigating heavy metal pollution through a range of mechanisms, including avoidance, chelation, sequestration, tolerance, excretion, and filtration. Studies highlighted a higher metal bioconcentration of metals in mangrove roots compared to leaves, indicating their remarkable endurance capability towards high levels of HMs. The uptake of HMs by mangrove roots occurs through passive diffusion across cell plasma membranes or active transport, regulated by metal ion transporters and influenced by electrochemical and/or concentration potential gradients. In phytoremediation strategies, mangrove plants employ several physiochemical mechanisms to avoid HMs uptake, such as cell wall immobilization, complexation with biomolecules like phytochelatins (PCs), and extracellular barriers at the root endodermis. Moreover, mangroves can develop iron-plaques on their root surface, acting as reservoirs for immobilized HMs and significantly influencing their sequestration, particularly in wastewater containing Cr, Pb, and Ni ions. Mangroves would also trigger antioxidant defenses to cope with the absorbed HMs and normalize the excessive production of reactive oxygen species (ROS)-mediated oxidative stress. However, the antioxidant response in mangroves varies depending on the concentration and type of toxic HMs, plant species, and exposure duration. Additionally, mangroves excrete excessive amounts of HMs through salt glands via adaxial trichomes, allowing them to mitigate phytotoxicity. Although mangroves demonstrate a high tolerance capacity towards HMs, hydrological alteration, deforestation, marine construction, and marine anthropogenic activities pose significant threats to several global mangrove species. In conclusion, conducting multiple toxicity tests using early mangrove seedlings are imperative that threshold effect concentrations of various HMs be determined under natural environmental conditions encompassing nutrients, salinity, temperature, and the presence of several contaminants. Besides, long-term, large-scale mesocosm experiments in real-field settings should be conducted in future to obtain more realistic and reliable insights into the uptake and tolerance of HMs in mangroves. [Display omitted] • Coastal ecosystem is endangered due to heavy metal contamination due to anthropogenic activities. • Mangroves ecosystem faced adverse effects of HMs toxicities. • Mangroves species mitigate HMs toxicities dependent on HMs type and concentration. • Mangroves tolerate HMs toxicity through cell wall immobilization, complexation with biomolecules and extracellular barriers. • Mangroves Phytoremediate HMs phytotoxicity through salt glands via adaxial trichomes. [ABSTRACT FROM AUTHOR]

Numerous abiotic stressors including heavy metal stresses, specifically cadmium (Cd) stress in agricultural bio-system hinder the plant adequate growth. The present study was aimed to reveal the protective role of silicon (Si) application with two levels and to recognize the optimum level of Si for wheat plants grown hydroponically under three different levels of Cd toxicities. In methodology, we used nine treatments with three levels of Si (0, 1, and 3 mmol L−1; Na 2 SiO 3) against three levels of Cd (0, 50, 200 μmol L−1; CdCl 2) with three biological replicates. The results of our study demonstrated that Si incorporation with the advantage of 3 mmol L−1 in cultured media with Cd50 and Cd200 demolished the toxic effects of Cd on the leaves of wheat plants by increasing plant dry biomass by 88% and 262%, leaf area by 48% and 57%, total chlorophyll contents by 120% and 74%, catalase (CAT) activity by 92% and 110%, superoxide dismutase (SOD) activity by 62% and 78%, peroxidase (POD) activity by 66% and 40%, ascorbic acid (AsA) contents by 33% and 34%, glutathione (GHS) contents by 39% and 30% and reduced MDA contents by 56% and 50%, H 2 O 2 contents by 61% and 66%, and EL contents by 56% and 47% as parallel to Cd corresponding levels. In addition, Si incorporation with the advantage of 3 mmol L−1 significantly increased relative water contents (RWC) to maintain the cell turgor pressure and protect the plant from wilting and cells flaccid and enhanced membrane stability index (MSI) to protect the plant from logging under damaging effects of Cd toxicities. Based on the present findings, Si can be considered a quasi-essential element that enhanced wheat tolerance against Cd toxicity by limiting uptake, accumulation, and translocation of Cd and through regulating antioxidative defense mechanisms. • The Cd accumulation in the leaves of wheat was enhanced under Cd stress alone. • Silicon supply alleviated Cd-induced phytotoxicity in wheat leaves. • Silicon application significantly reduced Cd translocation and thereby its uptake. • Silicon application enhanced nutrients uptake including Si and regulated defense mechanism. • The Si3 (3 mmol L−1) was more effective than Si1 (1 mmol L−1) under all Cd levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Uptake and translocation of heavy metals exert a range of toxic effects in plants. • Heavy metals cause a range of physiological and biochemical alterations in plants. • Phytohormones can effectively improve plants' resistance to heavy metal stress. • Phytohormones regulate heavy metal toxicity by up-regulating stress-responsive genes. • Phytohormonal cross-talk is also important in the alleviation of heavy metal toxicity. Heavy metal (HM)-mediated toxic effects on plants have attained considerable attention worldwide as they directly threaten the food supply chain. Although various measures have been taken to mitigate the adverse effects of heavy metal stress in plants, significant research gaps must be proactively addressed. Fascinatingly, the exogenous application of phytohormones has recently attained substantial interest in regulating the negative effects of HM stress. Phytohormones are signaling transductional molecules that mitigate HM toxicity in plants and support their growth and development. Both exogenous treatments and manipulation of the endogenous status of phytohormones through regulating their signaling/biosynthesis-related genes are effective strategies for protecting plants against HM-induced toxic effects. However, to achieve maximum benefits from phytohormone-mediated subcellular mechanisms to mitigate HM toxicity, it is necessary to gain in-depth understanding on their potential pathways. The current review focuses primarily on the major mechanistic phytohormonal-mediated approaches involved in alleviating the toxic effects of HMs in plants. Moreover, the potential roles of major phytohormones in triggering protein molecules, signaling transductions, and gene expressions to avoid, tolerate, or alleviate HM toxicity in plants are also discussed. This information provides systematic understanding on the mechanisms of phytohormones in modulating heavy metal tolerance in plants and could help to guide the development of strategies to improve plant tolerance against HM toxicity. [ABSTRACT FROM AUTHOR]

Nanotechnology offers many potential solutions for sustainable agroecosystem, including improvement in nutrient use efficiency, efficacy of pest management, and minimizing the adverse environmental effects of agricultural production. Herein, we first highlighted the integrated application of nanotechnology and precision agriculture for sustainable productivity. Application of nanoparticle mediated material and advanced biosensors in precision agriculture is only possible by nanochips or nanosensors. Nanosensors offers the measurement of various stresses, soil quality parameters and detection of heavy metals along with the enhanced data collection, enabling precise decision-making and resource management in agricultural systems. Nanoencapsulation of conventional chemical fertilizers (known as nanofertilizers), and pesticides (known as nanopesticides) helps in sustained and slow release of chemicals to soils and results in precise dosage to plants. Further, nano-based disease detection kits are popular tools for early and speedy detection of viral diseases. Many other innovative approaches including biosynthesized nanoparticles have been evaluated and proposed at various scales, but in fact there are some barriers for practical application of nanotechnology in soil-plant system, including safety and regulatory concerns, efficient delivery at field levels, and consumer acceptance. Finally, we outlined the policy options and actions required for sustainable agricultural productivity, and proposed various research pathways that may help to overcome the upcoming challenges regarding practical implications of nanotechnology. [Display omitted] • Nanotechnology, an innovative scientific field, is now applied in almost all scientific studies. • Integrated application of nanotechnology with precision agriculture can sustain the agricultural production. • Various kinds of nano-sensors and biosynthesized nanoparticles are applied in agriculture for better crop productivity. • Excessive nanoparticles application is a serious concern due to their unknown release in environmental compartments. • Toxicity concerns causing nanotechnology application limited, especially related to human health should be investigated. [ABSTRACT FROM AUTHOR]

• A critical review of photocatalytic and biodesulphurization methods is presented. • The mechanism of coal desulphurization is critically discussed. • Challenges faced in photocatalytic desulphurization are highlighted. • A hybrid system for biodesulphurization in synergy with CO 2 mitigation is proposed. • Cost analysis of simultaneous biodesulphurization and CO 2 consumption is reviewed. Developing efficient methods for deep desulphurization of commercial fuel is of utmost importance due to the environmental impact of sulphur and stringent government regulations for sulphur-free fuel. This review highlighted the significance of photo-assisted biocatalytic desulphurization of coal and introduced novel strategies that combine coal desulphurization with CO 2 mitigation. The interactions between microbes and the mechanisms underlying the biodesulphurization of coal were thoroughly discussed. Furthermore, the effect of coal structure and porosity on the desulphurization of inorganic sulphur was analyzed. It is acknowledged that achieving high catalytic efficiency and stability of the catalyst during photocatalytic desulphurization remains a challenge. The review also identified microbial species that are most suitable for simultaneous biodesulphurization and CO 2 mitigation, taking into account their mutualistic growth patterns. Besides, the mechanisms and cost-benefit analysis of coal biodesulphurization with high CO 2 consumption by bacterial communities in a hybrid system were further examined. The insights provided in this review can offer a comprehensive understanding of the design of a hybrid system capable of self-capturing CO 2 from polluted atmospheres and utilizing it in a reactor for cost-effective coal biodesulphurization, which holds great potential for combating smog and global warming. [ABSTRACT FROM AUTHOR]