Biochar as a tool for effective management of drought and heavy metal toxicity

Composites Based on Natural Zeolites and Green Materials for the Immobilization of Toxic Elements in Contaminated Soils: A Review

Soil contamination by toxic elements is a global problem, and the remediation of contaminated soils requires complex and time-consuming technology. Conventional methods of soil remediation are often inapplicable, so an intensive search is underway for innovative and environmentally friendly ways to clean up ecosystems. The use of amendments that stabilize the toxic elements in soil by reducing their mobility and bioavailability is one of the simplest and most cost-effective ways to remediate soil. This paper provides a summary of studies related to the use of composites based on natural zeolites and green materials for the immobilization of toxic elements in contaminated soils and highlights positive examples of returning land to agricultural use. The published literature on natural zeolites and their composites has shown that combinations of zeolite with biochar, chitosan and other clay minerals have beneficial synergistic effects on toxic element immobilization and soil quality. The effects of zeolite properties, different combinations, application rates, or incubation periods on toxic elements immobilization were tested in laboratory scale or field experiments, whereas the mobility of toxic elements in soil was evaluated by chemical extractions of toxic elements transferred to the plants. This review highlights the excellent potential of natural zeolites to be used as single or combined sustainable green materials to solve environmental pollution problems related to the presence of toxic elements.

Oxygen diffusion in biochar-based mixtures as plant growth media: Experimental and modelling

A large amount of agricultural waste is produced annually. Producing biochar is an excellent solution for waste management, resource recovery, emission reduction, energy production, reduction in transportation and enhancing carbon sequestration. This study was done to investigate the aeration status of biochar-based growth media as compared with the commercial soilless medium of cocopeat-perlite. Biochars from oven-dried residues were produced by slow pyrolysis at 300 (B300) and 500°C (B500) with a rate of 2°C min-1 and using a continuous inflow of nitrogen. Sawdust (Sd), wheat straw (WS), rice hull (Rh), palm bunches (Plm) and sugarcane bagasse (SC), their biochars, vermiculite (V) and zeolite (Z) were used to prepare 13 mixed growth media. Oxygen diffusion coefficient (Dp) of media was measured at six matric potentials (h) of -5, -10, -15, -20, -40 and -60 hPa. Troeh et al. (1982) model was fitted to Dp/D0 versus air-filled porosity (AFP) data. Although AFP was more than 0.1 m3 m-3 for some media, the Dp/D0 was very low. Considering optimum Dp/D0 (i.e. 0.010-0.015) for growth substrates at h = -8 hPa, aeration status of four media (cocopeat-perlite, Rh-SCB300-Z, Sd-SCB300-Z and WSB500-Rh-V) was optimum. Highest Dp/D0 at h = -8 hPa was observed for Rh-SCB300-Z. The AFP at h = -10 hPa was highest for Rh-SCB300-Z, cocopeat-perlite and WSB500-Rh-V. Biochar-based media with good aeration status and water retention can be a suitable substitute for commercial soilless culture in greenhouse production. Overall, WSB500-Rh-V is a suitable substitute for cocopeat-perlite.

KOH-modified biochar enhances nitrogen metabolism of the chloroquine phosphate-disturbed anammox: Physical binding, EPS modulation and versatile metabolic hierarchy

Chloroquine phosphate (CQ) poses strong biotoxicity on anammox process, and thus detoxifying is essential for the stable operation of anammox in treating CQ-bearing wastewater. Biochar has been proven to simultaneously detoxify pollutant and modulate nitrogen cycle in anammox by its shelter effect and electron exchange capacity (EEC) ability. To further improve the ability of biochar to promote the nitrogen metabolism of anammox, a KOH modification strategy was used to tailor a high-EEC biochar in this work. KOH modified biochar can bind CQ for detoxification driven by hydrogen bond, π-π interaction, and electrostatic interaction. Meanwhile, the EEC of modified biochar increased by 70 % than that of pristine biochar, thus improving nitrogen removal efficiency by 55.6 % and 9.5 % than CQ and BC group, respectively. Besides, the microorganism regulated by modified biochar produced more α-helix configuration, improving EPS barrier ability to CQ and sludge granulation. Lastly, metagenomic analysis revealed that modified biochar can stimulate the Wood-Ljungdahl pathway, increased the relative abundance of CODH from 0.74 % in CQ to 1.00 % in modified BC group. It favored the proliferation of autotrophic microorganisms, especially increased the relative abundance of anammox bacteria by 86.8 % than CQ group. This work will shed the light on integrating high-EEC biochar into anammox to cope with the micropollutants stress.

The Effect of Biochar on Tomato (Solanum lycopersicum) Cultivar Micro-Tom Grown under Continuous Light

Continuous lighting (CL) has the potential to increase crop yield in greenhouse production. Tomato plants, however, when exposed to CL develop inter-vascular chlorosis, a leaf injury which causes a reduction in chlorophyll content and necrosis. The application of biochar can reduce physiological stress in plants, we examine if biochar also reduces necrosis in tomatoes when grown under CL. Faecal sludge biochar was applied to an acidic soil to examine plant growth and yield in Micro-Tom tomato plants grown under continuous light. We examined soil and plant growth properties of three soil application treatments: a control soil, biochar treatment (4%w/w) (Biochar), and a combined biochar (2% w/w) and fertilizer (2% w/w) treatment (Biochar + Fert). Faecal sludge biochar addition produced plant heights 216% greater than control and above ground biomass 583% greater than control. The biochar and fertilizer treatment group produced a 487% increase in leaf number compared to biochar. The combined biochar and fertilizer treatment produced a 398% increase in dried above ground biomass and a 177% increase in dried fruit yield compared with biochar. Plants in the biochar and fertilizer treatment group showed less visual evidence of continuous light induced leaf injury.Biochar addition did not limit continuous light induced leaf chlorosis whereas combined biochar and fertilizer treatment resulted in a significant reduction in leaf injury and death. Overall, the application of biochar and biochar and fertilizer combined increased crop yield.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42729-024-02003-5.

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.

Biochar influences phytoremediation of heavy metals in contaminated soils: an overview and perspectives

Heavy metals (HMs) contamination has gained much attention due to its high degree of toxicity for living organisms. Therefore, different techniques are underway to eradicate HMs from the environment. Among the biological techniques, phytoremediation is a suitable method, but owing to the slow rate and chance of HMs penetration into the food chain, alternative techniques are needed to reduce their phytotoxicity, and biochar is one of them. Due to the diverse characteristics, biochar immobilizes HMs in the soil by improving soil pH, ion exchange, electrostatic interactions, complexation, precipitation, surface adsorption, and microbial activation. Thereby, amendment of biochar in the HMs-contaminated soils reduces HMs toxicity to plants and limits their penetration into the food chain. In contrast, some biochars have also been studied to induce metal availability in soils and subsequently its uptake by plants. This dual role of biochar depends on the feedstock of biochar, incineration temperature, and the rate of application. Moreover, biochar treatments enhance plant growth under HMs stress by improving nutrient availability, water retention capacity, scavenging of reactive oxygen species, and photosynthetic efficiency. Owing to the beneficial characteristics of biochar in HMs-contaminated sites, the number of publications has tremendously increased. Additionally, the plant species and the types of HMs that have been tested frequently under biochar treatments in these articles have been studied. Overall, the current study would help in understanding the mechanisms of how biochar influences phytoremediation of HMs and improves plant growth in HMs-polluted soils and the current scenario of the available literature.

Time-varying contributions of FeII and FeIII to AsV immobilization under anoxic/oxic conditions: The impacts of biochar and dissolved organic carbon

Engineering black carbon (e.g. biochar) has been widely found in natural environments due to natural processes and extensive applications in engineering systems, and could influence the geochemical processes of coexisting arsenic (AsV) and FeII, especially when they are exposed to oxic conditions. Here, we studied time-varying kinetics and efficiencies of AsV immobilization by solid-phase FeII (FeIIsolid) and FeIII (FeIIIsolid) in FeII-AsV-biochar systems under both anoxic and oxic conditions at pH 7.0, with focuses on the effects of biochar surface and biochar-derived dissolved organic carbon (DOC). Under anoxic conditions, FeII could rapidly immobilize AsV via co-adsorption onto biochar surfaces, which also serves as the dominant pathway of AsV immobilization at the initial stage of reaction (0-5 min) under oxic conditions at high biochar concentrations. Subsequently, with increasing biochar concentrations, FeIIIsolid precipitation from aqueous FeII (FeIIaq) oxidation (5-60 min) starts to play an important role in AsV immobilization but in decreased efficiencies of AsV immobilization per unit iron. In the following stage (60-300 min), FeIIsolid oxidation is suppressed and leads to AsV release into solutions at >1.0 g·L-1 biochar. The decreasing efficiency of AsV immobilization over time is attributed to the gradual release of DOC into solution from biochar particles, which significantly inhibit AsV immobilization when FeIIIsolid is generated from FeIIsolid oxidation in the vicinity of biochar surfaces. Specifically, 4.06 mg·L of biochar-derived DOC can completely inhibit the immobilization of AsV in the 100 μM FeII system under oxic conditions. The findings are crucial to comprehensively understand and predict the behavior of FeII and AsV with coexisting engineering black carbon in natural environments.

A quantitative review of the effects of biochar application on the reduction of Cu concentration in plant: a meta-analysis

Contamination and toxicity of copper (Cu) in soils are global issues, particularly in regions where Cu-based fungicides are utilized. Elevated Cu concentrations can lead to soil contamination and pose significant risks to the ecosystem, including plant life, wildlife, and human health. The application of biochar has been proposed as a viable strategy to mitigate Cu accumulation in plants. However, there is no quantitative and data-based consensus on the impact of biochar on plant Cu accumulation. In this meta-analysis, 624 data records from 65 published literature were collected and the effects of various factors, including biochar properties, experimental conditions, and soil properties on Cu accumulation in plants, were examined through meta-subgroup analysis and meta-regression models. The results obtained indicate a significant dose-dependent effect of biochar in decreasing Cu concentration in plants by an average of 23.45%. Soils with acidic pH values and medium textures were more conducive for biochar to mitigate Cu accumulation in plant tissues. In addition, manure biochar and green waste biochar were found to be more successful in decreasing Cu concentrations in plants compared to other biochar types. Biochar types with pyrolysis temperatures of > 600 °C and pH values of ≥ 10 resulted in greater decreases in plant Cu concentration. Regarding biochar application, biochar minimum range of 1% in potting experiments and 20 t/ha in field experiments have been recommended to effectively decrease Cu concentration in plants. Overall, these findings provide valuable insights into Cu transfer mitigation through food chain to human bodies and for policymakers to take preventive measures.

Improving maize yield and drought tolerance in field conditions through activated biochar application

Amidst depleting water resources, rising crop water needs, changing climates, and soil fertility decline from inorganic modifications of soil, the need for sustainable agricultural solutions has been more pressing. The experimental work aimed to inspect the potential of organically activated biochar in improving soil physicochemical and nutrient status as well as improving biochemical and physiological processes, and optimizing yield-related attributes under optimal and deficit irrigation conditions. Biochar enhances soil structure, water retention, and nutrient availability, while improving plant nutrient uptake and drought resilience. The field experiment with maize crop was conducted in Hardaas Pur (32°38.37'N, 74°9.00'E), Gujrat, Pakistan. The experiment involved the use of DK-9108, DK-6321, and Sarhaab maize hybrid seeds, with five moisture levels of evapotranspiration (100% ETC, 80% ETC, 70% ETC, 60% ETC, and 50% ETC) maintained throughout the crop seasons. Furthermore, activated biochar was applied at three levels: 0 tons/ha (no biochar), 5 tons per hectare, and 10 tons per hectare. The study's findings revealed significant improvements in soil organic matter, bulk density, nutrient profile and total porosity with biochar supplementation in soil. Maize plants grown under lower levels of ETC in biochar supplemented soil had enhanced membrane stability index (1.6 times higher) increased protein content (1.4 times higher), reduced malondialdehyde levels (0.7 times lower), improved antioxidant enzyme activity (1.3 times more SOD and POD activity, and 1.2 times more CAT activity), improved relative growth (1.05 times more) and enhanced yield parameters (26% more grain and stover yield, 16% more 1000-seed weight, 29% more total seed weight, 33% more apparent water productivity) than control. Additionally, among the two biochar application levels tested, the 5 tons/ha dose demonstrated superior efficiency compared to the 10 tons/ha biochar dose.

Phytoremediation of Hg and chlorpyrifos contaminated soils using Phaseolus vulgaris L. with biochar, mycorrhizae, and compost amendments

Anthropogenic activities, encompassing vast agricultural and industrial operations around the world, exert substantial pressure on the environment, culminating in profound ecological impacts. These activities exacerbate soil contamination problems with pollutants such as mercury (Hg) and chlorpyrifos (CPF) that are notable for their widespread presence and detrimental effects. The objective of this study is to evaluate the phytoremediation potential of Phaseolus vulgaris L., augmented with various combinations of biochar, mycorrhizal, and compost amendments, as a sustainable alternative for the remediation of soils contaminated with Hg and CPF. For this purpose, soil from a mining area with mercury contamination has been taken, to which CPF has been added in different concentrations. Then, previously germinated Phaseolus vulgaris L. seedlings with an average height of 10 cm were planted. Electrical conductivity, pH, organic matter, CPF, and Hg, as well as seedling growth parameters, have been evaluated to determine the processes of absorption of soil contaminants into the plant. A combination of biochar with mycorrhiza has been found to be an optimal choice for CPF and Hg remediation. However, all amendments have proven to be efficient in the remediation processes of the tested contaminants.

Sustainable soil management under drought stress through biochar application: Immobilizing arsenic, ameliorating soil quality, and augmenting plant growth

Rise in climate change-induced drought occurrences have amplified pollution of metal(loid)s, deteriorated soil quality, and deterred growth of crops. Rice straw-derived biochars (RSB) and cow manure-enriched biochars (CEB) were used in the investigation (at doses of 0%, 2.5%, 5%, and 7.5%) to ameliorate the negative impacts of drought, improve soil fertility, minimize arsenic pollution, replace agro-chemical application, and maximize crop yields. Even in soils exposed to severe droughts, 3 months of RSB and CEB amendment (at 7.5% dose) revealed decreased bulk density (13.7% and 8.9%), and increased cation exchange capacity (6.0% and 6.3%), anion exchange capacity (56.3% and 28.0%), porosity (12.3% and 7.9%), water holding capacity (37.5% and 12.5%), soil respiration (17.8% and 21.8%), and nutrient contents (especially N and P). Additionally, RSB and CEB decreased mobile (30.3% and 35.7%), bio-available (54.7% and 45.3%), and leachable (55.0% and 56.5%) fractions of arsenic. Further, pot experiments with Bengal gram and coriander plants showed enhanced growth (62-188% biomass and 90-277% length) and reduced arsenic accumulation (49-54%) in above ground parts of the plants. Therefore, biochar application was found to improve physico-chemical properties of soil, minimize arsenic contamination, and augment crop growth even in drought-stressed soils. The investigation suggests utilisation of cow manure for eco-friendly fabrication of nutrient-rich CEB, which could eventually promote sustainable agriculture and circular economy. With the increasing need for sustainable agricultural practices, the use of biochar could provide a long-term solution to enhance soil quality, mitigate the effects of climate change, and ensure food security for future generations. Future research should focus on optimizing biochar application across various soil types and climatic conditions, as well as assessing its long-term effectiveness.

Co-application of Parthenium biochar and urea effectively mitigate cadmium toxicity during wheat growth

Environmental contamination by cadmium (Cd), a highly toxic heavy metal, poses significant health risks to plants and humans. Biochar has been effectively used to promote plant growth and productivity under Cd stress. This study presents an innovative application of biochar derived from the invasive weed Parthenium hysterophorus to promote plant growth and productivity under Cd stress. Our study includes detailed soil and plant analyses, providing a holistic perspective on how biochar and urea amendments influence soil properties, nutrient availability, and plant physiological responses. To address these, we established seven treatments: the control, Cd alone (5 mg kg-1), biochar alone (5 %), urea alone (3 g kg-1), biochar with Cd, urea with Cd, and a combination of biochar and urea with Cd. Cd stress alone significantly reduced plant growth indicators such as shoot and root length, fresh and dry biomass, chlorophyll content, and grain yield. However, the supplementation of biochar, urea, or their combination significantly increased shoot length (by 48%, 34%, and 65%), root length (by 73%, 46%, and 70%), and fresh shoot biomass (by 4%, 31%, and 4%), respectively. This improvement is attributed to enhanced soil properties and improved nutrient absorption. The biochar-urea combination also enhanced Cd tolerance by improving total chlorophyll content by 14 %, 13 %, and 16 % compared to the control, respectively. Similaly, these treatments significantly (p < 0.05) boosted the activity of antioxidant enzymes such as catalase, peroxidase, and superoxide dismutase by 51 %, 30 %, and 51 %, respectively, thereby mitigating oxidative stress as a defensive mechanism. The Cd tolerance was improved by biochar, urea, and their combinations, which reduced Cd content in the shoots (by 60.5 %, 38.9 %, and 51.3 %), roots (by 47.5 %, 23.9 %, and 57.6 %), and grains (by 58.1 %, 30.2 %, and 38.3 %) relative to Cd stress alone, respectively. The synergistic effects of biochar and urea are achieved through improved soil properties, nutrient availability, activating antioxidant defense mechanisms, and minimizing the accumulation of metal ions in plant tissues, thereby enhancing plant defenses against Cd stress. Conclusively, converting invasive Parthenium weed into biochar and combining it with urea offers an environmentally friendly solution to manage its spreading while effectively mitigating Cd stress in crops.

Assessing biochar, clinoptilolite zeolite and zeo-char loaded nano-nitrogen for boosting growth performance and biochemical ingredients of peace lily (Spathiphyllum Wallisii) plant under water shortage

BACKGROUND

Peace lily (Spathiphyllum wallisii Regel) is an ornamental indoor plant with promising cut flower market, as well as antiviral, pharmacological and ecological potentials. Water deficiency can have sound effects on the growth performance and aesthetic quality of such plant. The aim of this study was to investigate the consequences of zeolite, biochar, and zeo-char loaded nano-nitrogen application on the growth performance and biochemical components of peace lily under water shortage conditions. An experiment was conducted over two consecutive seasons (2021-2022) at the experimental nursery of Ornamental Horticulture Department, Faculty of Agriculture, Cairo University, Giza, Egypt. Soil amendments; zeolite, biochar, and zeo-char loaded nano-nitrogen were prepared and applied to soil before cultivation.

RESULTS

Our results revealed that the new combination treatment (zeo-char loaded nano-N) had an exceeding significant effect on most of the studied parameters. Vegetative traits such as plant height (35.7 and 35.9%), leaf number per plant (73.3 and 52.6%), leaf area (40.2 and 36.4%), stem diameter (28.7 and 27.1%), root number (100 and 43.5%) and length (105.7 and 101.9%) per plant, and fresh weight of leaves (23.2 and 21.6%) were significantly higher than control (commercially recommended dose of NPK) with the application of zeo-char loaded nano-N during the two growing seasons, respectively. Similar significant increments were obtained for some macro- (N, P, K, Mg, Ca) and micro- (Fe, Zn, Mn) elements with the same treatment relative to control. Chlorophyll (18.4%) and total carotenoids (82.9 and 32.6%), total carbohydrates (53.3 and 37.4%), phenolics (54.4 and 86.9%), flavonoids (31.7% and 41.8%) and tannins (69.2 and 50%), in addition to the phytohormone gibberellic acid (GA3) followed the same trend with the application of zeo-char loaded nano-N, increasing significantly over control. Leaf histological parameters and anatomical structure were enhanced with the new combination treatment in comparison with control. Antioxidant enzymes (catalase and peroxidase), proline and abscisic acid (ABA) exhibited significant declines with zeo-char loaded nano-N treatment relative to control.

CONCLUSION

These findings suggest that incorporating soil amendments with nano- nutrients could provide a promising approach towards improving growth performance and quality of ornamental, medicinal and aromatic species under water deficiency conditions.

Unraveling the mechanisms of biochar and steel slag in alleviating lithium stress in tomato (Solanum lycopersicum L.) plants via modulation of antioxidant defense and methylglyoxal detoxification pathways

With progress in technology, soaring demand for lithium (Li) has led to its release into the environment. This study demonstrated the mitigation of the adverse effects of Li stress on tomato (Solanum lycopersicum L.) by the application of waste materials, namely coconut shell biochar (CBC) and steel slag (SS). To explore the impact of Li treatment on tomato plants different morphological, biochemical parameters and plant defense system were analyzed. Tomato plants exposed to Li had shorter roots and shoots, lower biomass and relative water contents, and showed decreases in physiological variables, as well as increases in electrolyte leakage and lipid peroxidation. However, the application of CBC and SS as passivators, either singly or in combination, increased growth variables of tomato and relieved Li-induced oxidative stress responses. The combined CBC and SS amendments reduced Li accumulation 82 and 90% in tomato roots and shoots, respectively, thereby minimizing the negative impacts of Li. Antioxidant enzymes SOD, CAT, APX and GR reflected 4, 5, 30, and 52% and glyoxalase enzymes I and II 7 and 250% enhancement in presence of both CBC and SS in Li treated soil, with a concurrent decrease in methylglyoxal content. Lithium treatment triggered oxidative stress, increased enzymatic and non-enzymatic antioxidant levels, and induced the synthesis of thiols and phytochelatins in roots and shoots. Hence, co-amendment with CBC and SS protected tomato plants from Li-induced oxidative damage by increasing antioxidant defenses and glyoxalase system activity. Both CBC, generated from agricultural waste, and SS, an industrial waste, are environmentally benign, safe, economical, and non-hazardous materials that can be easily applied on a large scale for crop production in Li-polluted soils. The present findings highlight the novel reutilization of waste materials as renewable assets to overcome soil Li problems and emphasize the conversion of waste into wealth and its potential for practical applications.

Integrated physio-biochemistry and RNA-seq revealed the mechanism underlying biochar-mediated alleviation of compound heavy metals (Cd, Pb, As) toxicity in cotton

Biochar has been recognised as an efficacious amendment for the remediation of compound heavy metal contamination in soil. However, the molecular mechanism of biochar-mediated tolerance to compound heavy metal toxicity in cotton is unknown. The objective of this research was to investigate the positive impact of biochar (10 g·kg-1) on reducing damage caused by compound heavy metals (Cd, Pb, and As) in cotton (Gossypium hirsutum L.). The results revealed that biochar reduced Cd concentrations by 24.9 % (roots), and decreased Pb concentrations by 37.1 % (roots) and 59.53 % (stems). Biochar maintained ionic homoeostasis by regulating the expression of metal transporter proteins such as ABC, HIPP, NRAMP3, PCR, and ZIP, and genes related to the carbon skeleton and plasma membrane. Biochar also downregulated genes related to photosynthesis, thereby increasing photosynthesis. Biochar re-established redox homoeostasis in cotton by activating signal transduction, which regulated the activity of the enzymes POD, SOD, and CAT activity; and the expression of related genes. This research revealed the molecular mechanism by which biochar confers resistance to the harmful effects of compound heavy metal toxicity in cotton. The application of biochar as a soil amendment to neutralise the toxicity of compound heavy metals is recommended for cash crop production.

Microbial-assistance and chelation-support techniques promoting phytoremediation under abiotic stresses

Phytoremediation, the use of plants to remove heavy metals from polluted environments, has been extensively studied. However, abiotic stresses such as drought, salt, and high temperatures can limit plant growth and metal uptake, reducing phytoremediation efficiency. High levels of HMs are also toxic to plants, further decreasing phytoremediation efficacy. This manuscript explores the potential of microbial-assisted and chelation-supported approaches to improve phytoremediation under abiotic stress conditions. Microbial assistance involves the use of specific microbes, including fungi that can produce siderophores. Siderophores bind essential metal ions, increasing their solubility and bioavailability for plant uptake. Chelation-supported methods employ organic acids and amino acids to enhance soil absorption and supply of essential metal ions. These chelating agents bind HMs ions, reducing their toxicity to plants and enabling plants to better withstand abiotic stresses like drought and salinity. Managed microbial-assisted and chelation-supported approaches offer more efficient and sustainable phytoremediation by promoting plant growth, metal uptake, and mitigating the effects of heavy metal and abiotic stresses. Managed microbial-assisted and chelation-supported approaches offer more efficient and sustainable phytoremediation by promoting plant growth, metal uptake, and mitigating the effects of HMs and abiotic stresses.These strategies represent a significant advancement in phytoremediation technology, potentially expanding its applicability to more challenging environmental conditions. In this review, we examined how microbial-assisted and chelation-supported techniques can enhance phytoremediation a method that uses plants to remove heavy metals from contaminated sites. These approaches not only boost plant growth and metal uptake but also alleviate the toxic effects of HMs and abiotic stresses like drought and salinity. By doing so, they make phytoremediation a more viable and effective solution for environmental remediation.

An animal charcoal contaminated cottage industry soil highlighted by halophilic archaea dominance and decimation of bacteria

An animal charcoal contaminated cottage industry soil in Lagos, Nigeria (ACGT) was compared in an ex post facto study with a nearby unimpacted soil (ACGC). Hydrocarbon content was higher than regulatory limits in ACGT (180.2 mg/kg) but lower in ACGC (19.28 mg/kg). Heavy metals like nickel, cadmium, chromium and lead were below detection limit in ACGC. However, all these metals, except cadmium, were detected in ACGT, but at concentrations below regulatory limits. Furthermore, copper (253.205 mg/kg) and zinc (422.630 mg/kg) were above regulatory limits in ACGT. Next generation sequencing revealed that the procaryotic community was dominated by bacteria in ACGC (62%) while in ACGT archaea dominated (76%). Dominant phyla in ACGC were Euryarchaeota (37%), Pseudomonadota (16%) and Actinomycetota (12%). In ACGT it was Euryarchaeota (76%), Bacillota (9%), Pseudomonadota (7%) and Candidatus Nanohaloarchaeota (5%). Dominant Halobacteria genera in ACGT were Halobacterium (16%), Halorientalis (16%), unranked halophilic archaeon (13%) Salarchaeum (6%) and Candidatus Nanohalobium (5%), whereas ACGC showed greater diversity dominated by bacterial genera Salimicrobium (7%) and Halomonas (3%). Heavy metals homeostasis genes, especially for copper, were fairly represented in both soils but with bacterial taxonomic affiliations. Sites like ACGT, hitherto poorly studied and understood, could be sources of novel bioresources.

Biochar with KMnO4-hematite modification promoted foxtail millet growth by alleviating soil Cd and Zn biotoxicity

The excessive accumulation of Cd and Zn in soil poisons crops and threatens food safety. In this study, KMnO4-hematite modified biochar (MnFeB) was developed and applied to remediate weakly alkaline Cd-Zn contaminated soil, and the heavy metal immobilization effect, plant growth, and metal ion uptake of foxtail millet were studied. MnFeB application reduced the phytotoxicity of soil heavy metals; bioavailable acid-soluble Cd and Zn were reduced by 57.79% and 35.64%, respectively, whereas stable, non-bioavailable, residual Cd and Zn increased by 96.44% and 32.08%, respectively. The chlorophyll and total protein contents and the superoxide dismutase (SOD)activity were enhanced, whereas proline, malondialdehyde, the H2O2 content, glutathione reductase (GR), ascorbate peroxidase (APX) and catalase (CAT) activities were reduced. Accordingly, the expressions of GR, APX, and CAT were downregulated, whereas the expression of MnSOD was upregulated. In addition, MnFeB promoted the net photosynthetic rate and growth of foxtail millet plants. Furthermore, MnFeB reduced the levels of Cd and Zn in the stems, leaves, and grains, decreased the bioconcentration factor of Cd and Zn in shoots, and weakened the translocation of Cd and Zn from roots to shoots. Precipitation, complexation, oxidation-reduction, ion exchange, and π-π stacking interaction were the main Cd and Zn immobilization mechanisms, and MnFeB reduced the soil bacterial community diversity and the relative abundance of Proteobacteria and Planctomycetota. This study provides a feasible and effective remediation material for Cd- and Zn-contaminated soils.

A comprehensive review on biochar against plant pathogens: Current state-of-the-art and future research perspectives

Plant pathogens cause a serious menace to food production. The diseases caused by pathogens are estimated to cause a yield loss of about 14.1 %, whereas, in India, up to 26 %. Several plant pathogens like Pythium, Phytophthora, Rhizoctonia, Sclerotinia, Fusarium, and Verticillium can cause 50-75 % yield losses in cereals, cotton, and horticultural crops (fruits, vegetables, and flowers) 10-100 % in pulses, 30-60 % loses in oilseed crops and 40-50 % in plantation crops. Biochar as soil amendment is emerging as an effective environment friendly substitute for fungicides to counter plant pathogens. It has also been reported to induce resistance in plants to combat plant pathogens by activating the two important defense pathways such as salicylic acid, jasmonate/ethylene defense, and triggering the plant's antioxidant enzymatic activities. Biochar promotes soil health and consequently improves the plant health, resulting in reduced incidence of disease. This novel amendment also helps in the priming of expression of genes against foliar fungal pathogen infection. This review paper will summarize the effect of biochar incorporation in the plant disease management as well as on their growth parameters.

Synergistic Interaction Between PbbZIP88 and PbSRK2E Enhances Drought Resistance in Pear Through Regulation of PbATL18 Expression and Stomatal Closure

Drought poses significant challenges to agricultural production, ecological stability and global food security. While wild pear trees exhibit strong drought resistance, cultivated varieties show weaker drought tolerance. This study aims to elucidate the molecular mechanisms underlying pear trees' response to drought stress. We identified a drought resistance-related transcription factor, PbbZIP88, which binds to and activates the expression of the drought-responsive gene PbATL18. Overexpression of PbbZIP88 in Arabidopsis and pear seedlings resulted in enhanced drought resistance and significantly improved physiological parameters under drought stress. We discovered that PbbZIP88 interacts with the key protein PbSRK2E in the ABA signalling pathway. This interaction enhances PbbZIP88's ability to activate PbATL18 expression, leading to higher levels of PbATL18. Furthermore, the PbbZIP88 and PbSRK2E interaction accelerates the regulation of stomatal closure under ABA treatment conditions, reducing water loss more effectively. Experimental evidence showed that silencing PbbZIP88 and PbSRK2E genes significantly decreased drought resistance in pear seedlings. In conclusion, this study reveals the synergistic role of PbbZIP88 and PbSRK2E in enhancing drought resistance in pear trees, particularly in the upregulation of PbATL18 expression, and the accelerated promotion of stomatal closure. These findings provide new candidate genes for breeding drought-resistant varieties and offer a theoretical foundation and technical support for achieving sustainable agriculture.

Modern perspectives of heavy metals alleviation from oil contaminated soil: A review

Heavy metal poisoning of soil from oil spills causes serious environmental problems worldwide. Various causes and effects of heavy metal pollution in the soil environment are discussed in this article. In addition, this study explores new approaches to cleaning up soil that has been contaminated with heavy metals as a result of oil spills. Furthermore, it provides a thorough analysis of recent developments in remediation methods, such as novel nano-based approaches, chemical amendments, bioremediation, and phytoremediation. The objective of this review is to provide a comprehensive overview of the removal of heavy metals from oil-contaminated soils. This review emphasizes on the integration of various approaches and the development of hybrid approaches that combine various remediation techniques in a synergistic way to improve sustainability and efficacy. The study places a strong emphasis on each remediation strategy that can be applied in the real-world circumstances while critically evaluating its effectiveness, drawbacks, and environmental repercussions. Additionally, it discusses the processes that reduce heavy metal toxicity and improve soil health, taking into account elements like interactions between plants and microbes, bioavailability, and pollutant uptake pathways. Furthermore, the current study suggests that more research and development is needed in this area, particularly to overcome current barriers, improve our understanding of underlying mechanisms, and investigate cutting-edge ideas that have the potential to completely transform the heavy metal clean up industry.

Biochar is an organomineral tool for mitigation of Cd toxicity in rice embedded soil and plant

Cadmium (Cd) contamination poses a significant threat to plants and human, as it can easily accumulate in plant tissues, leading to biochemical and physiological disorders. There is a growing interest in using biochar to mitigate the absorption of heavy metals by rice plants. This study tested peach biochar (PB) and its various levels of applications to evaluate the promising level for Cd remediation in contaminated soil. The application of PB3 had a significant impact on Cd mitigation, with extractable Cd (AB-DTPA) in soil decreasing from 66 mg kg-1 to 18 mg kg-1. Cd content in shoots decreased from 2.5 mg kg-1 to 0.9 mg kg-1, and in grains decreased from 1.1 mg kg-1 to 0.5 mg kg-1. Moreover, the PB treatment led to increased rice yield, from 4.9 to 10 g pot-1, and biological yield, from 4 to 20 g pot-1. The soil also showed improved organic matter content, increasing from 0.4% to 0.7%, and enhanced levels of nitrogen (N), phosphorus (P), and potassium (K), by increases from 2.1 g pot-1 to 5 g pot-1, 58 mg kg-1 to 83 mg kg-1, and 40 mg kg-1 to 63 mg kg-1, respectively. These findings demonstrate the potential of PB in mitigating Cd contamination in soil and reducing its uptake by rice plants.

Recent progress on conservation and restoration of soil fertility for horticulture

Soil serves as a fundamental and valuable asset in horticultural activities, and preserving and restoring soil quality is critical to ensuring the long-term profitability and sustainability of these operations. Human activities and natural processes are the primary causes of natural resource degradation, with soil erosion emerging as a significant threat across multiple degradation pathways. Thus, comprehensive management of water and soil resources is required to promote sustainable horticulture and protect natural ecosystems. The advancement and dissemination of innovative technologies, coupled with the prudent utilization of natural resources with potential management approaches, are urgently needed to mitigate the deterioration of water and soil quality. The soil's fertility can be enhanced further by including cover crops that add organic matter into the soil, which results in strengthened structural integrity and encourages fertile and healthy soil; by employing green manure as well as expanding legumes that absorb N from the air via the biological N fixation; using micro-dose fertilizer to compensate for expenses via plant absorption as well as additional techniques; as well as minimizing expenses employing leaching beneath the plant's rooting region. This review discusses strategies for optimizing soil properties and increasing nutrient accessibility, as well as novel approaches to improving water utilization, waste reduction, and ecosystem preservation. Finally, implementing integrated and environmentally sound soil management strategies is critical for addressing the challenges posed by global warming and the limited availability of resources inherent in horticultural practices.

Putting Biochar in Action: A Black Gold for Efficient Mitigation of Salinity Stress in Plants. Review and Future Directions

Soil salinization is a serious concern across the globe that is negatively affecting crop productivity. Recently, biochar received attention for mitigating the adverse impacts of salinity. Salinity stress induces osmotic, ionic, and oxidative damages that disturb physiological and biochemical functioning and nutrient and water uptake, leading to a reduction in plant growth and development. Biochar maintains the plant function by increasing nutrient and water uptake and reducing electrolyte leakage and lipid peroxidation. Biochar also protects the photosynthetic apparatus and improves antioxidant activity, gene expression, and synthesis of protein osmolytes and hormones that counter the toxic effect of salinity. Additionally, biochar also improves soil organic matter, microbial and enzymatic activities, and nutrient and water uptake and reduces the accumulation of toxic ions (Na+ and Cl), mitigating the toxic effects of salinity on plants. Thus, it is interesting to understand the role of biochar against salinity, and in the present Review we have discussed the various mechanisms through which biochar can mitigate the adverse impacts of salinity. We have also identified the various research gaps that must be addressed in future study programs. Thus, we believe that this work will provide new suggestions on the use of biochar to mitigate salinity stress.

Investigating the carcinogenic and non-carcinogenic health hazards of heavy metal ions in Spinacia oleracea grown in agricultural soil treated with biochar and humic acid

This study addressed the bioaccumulation and human health risk among the consumption of Spinacia oleracea grown in agricultural soil treated with humic acid (189-2310 ppm) and biochars (0.00-5.10%.wt). The biochars came from two local feedstocks of rice-husk (RH) and sugar-beet-pulp (SBP) pyrolyzed at temperatures 300 and 600 °C. Total concentrations of Cu, Cd, and Ni found in both the soil and biomass/biochar exceeded global safety thresholds. The bioaccumulation levels of HMs in spinach leaves varied, with Fe reaching the highest concentration at 765.27 mg kg-1 and Cd having the lowest concentration at 3.31 mg kg-1. Overall, the concentrations of Zn, Cd, Pb, and Ni in spinach leaves exceeded the safety threshold limits, so that its consumption is not recommended. The assessment of hazard quotient (HI) for the HMs indicated potential health hazards for humans (HI > 1) from consuming the edible parts of spinach. The biochar application rates of 4.35%wt and 0.00%.wt resulted in the highest (3.69) and lowest (3.15) HI values, respectively. The cumulative carcinogenic risk (TCR) ranged from 0.0085 to 0.0119, exceeding the cancer risk threshold. Introducing 5.10%wt biomass/biochar resulted in a 36% rise in TCR compared to the control. The utilization of humic acid alongside HMs-polluted biochars results in elevated levels of HMs bioaccumulation exceeding the allowable thresholds in crops (with a maximum increase of 49% at 2000 ppm humic acid in comparison to 189 ppm). Consequently, this raised the HI by 46% and the TCR by 22%. This study demonstrated that the utilization of HMs-polluted biochars could potentially pose supplementary health hazards. Moreover, it is evident that the utilization of HMs-polluted biochars in treating metal-contaminated soil does not effectively stabilize or reduce pollution.

Pyrolyzed and unpyrolyzed residues enhance maize yield under varying rates of application and fertilization regimes

Biochar is increasingly gaining popularity due to its extensive recommendation as a potential solution for addressing the concerns of food security and climate change in agroecosystems, with biochar application for increased carbon sequestration, enhanced soil fertility, improved soil health, and increased crop yield and quality. There have been multiple studies on crop yield utilizing various biochar types and application amounts; however, none have focused on the influence of diverse biochar types at various pyrolysis temperatures with different application amounts and the integration of fertilizer regimes in maize crops. Therefore, a two-year factorial field experiment was designed in a temperate Himalayan region of India (THRI) to evaluate the residual effect of different biochar on maize yield under different pyrolysis temperatures, various application rates and fertilizer regimes. The study included three factors viz., amendment type (factor 1), rate of application (factor 2) and fertilizer regime (factor 3). Amendment type included 7 treatments: No biochar- control (A1), apple biochar @ 400 °C pyrolysis temperature (A2), apple biochar @ 600 °C pyrolysis temperature (A3), apple residue biomass (A4), dal weed biochar @ 400 °C pyrolysis temperature (A5), dal weed biochar @ 600 °C pyrolysis temperatures (A6), and dal weed residue biomass (A7). The rate of application included 3 levels: Low (L- 1 t ha-1), medium (M- 2 t ha-1), and high (H- 3 t ha-1). At the same time, the fertilizer regimes included 2 treatments: No fertilizer (N) and recommended dose of fertilizer (F). The results revealed that among the various amendment type, rate of application and fertilizer regimes, the A3 amendment, H rate of application and F fertilizer regime gave the best maize growth and productivity outcome. Results revealed that among the different pyrolyzed residues used, the A3 amendment had the highest plant height (293.87 cm), most kernels cob-1 (535.75), highest soil plant analysis development (SPAD) value (58.10), greatest cob length (27.36 cm), maximum cob girth (18.18 cm), highest grain cob yield (1.40 Mg ha-1), highest grain yield (4.78 Mg ha-1), higher test weight (305.42 gm), and highest stover yield (2.50 Mg ha-1). The maximum dry weight in maize and the number of cobs plant-1 were recorded with amendments A4 (14.11 Mg ha-1) and A6 (1.77), respectively. The comparatively 2nd year of biochar application than the 1st year, the H level of the rate of application than the L rate and the application and integration of the recommended dose of fertilizer in maize results in significantly higher values of growth and productivity in maize. Overall, these findings suggest that the apple biochar @ 600 °C pyrolysis temperature (A3) at a high application rate with the addition of the recommended dose of fertilizer is the optimal biochar for enhancing the growth and productivity of maize in the THRI.

Optimizing biochar, vermicompost, and duckweed amendments to mitigate arsenic uptake and accumulation in rice (Oryza sativa L.) cultivated on arsenic-contaminated soil

The accumulation of arsenic (As) in rice (Oryza sativa L.) grain poses a significant health concern in Bangladesh. To address this, we investigated the efficacy of various organic amendments and phytoremediation techniques in reducing As buildup in O. sativa. We evaluated the impact of five doses of biochar (BC; BC0.1: 0.1%, BC0.28: 0.28%, BC0.55: 0.55%, BC0.82: 0.82% and BC1.0: 1.0%, w/w), vermicompost (VC; VC1.0: 1.0%, VC1.8: 1.8%, VC3.0: 3.0%, VC4.2: 4.2% and VC5.0: 5.0%, w/w), and floating duckweed (DW; DW100: 100, DW160: 160, DW250: 250, DW340: 340 and DW400: 400 g m- 2) on O. sativa cultivated in As-contaminated soil. Employing a three-factor five-level central composite design and response surface methodology (RSM), we optimized the application rates of BC-VC-DW. Our findings revealed that As contamination in the soil negatively impacted O. sativa growth. However, the addition of BC, VC, and DW significantly enhanced plant morphological parameters, SPAD value, and grain yield per pot. Notably, a combination of moderate BC-DW and high VC (BC0.55VC5DW250) increased grain yield by 44.4% compared to the control (BC0VC0DW0). As contamination increased root, straw, and grain As levels, and oxidative stress in O. sativa leaves. However, treatment BC0.82VC4.2DW340 significantly reduced grain As (G-As) by 56%, leaf hydrogen peroxide by 71%, and malondialdehyde by 50% compared to the control. Lower doses of BC-VC-DW (BC0.28VC1.8DW160) increased antioxidant enzyme activities, while moderate to high doses resulted in a decline in these activities. Bioconcentration and translocation factors below 1 indicated limited As uptake and translocation in plant tissues. Through RSM optimization, we determined that optimal doses of BC (0.76%), VC (4.62%), and DW (290.0 g m- 2) could maximize grain yield (32.96 g pot- 1, 44% higher than control) and minimize G-As content (0.189 mg kg- 1, 54% lower than control). These findings underscore effective strategies for enhancing yield and reducing As accumulation in grains from contaminated areas, thereby ensuring agricultural productivity, human health, and long-term sustainability. Overall, our study contributes to safer food production and improved public health in As-affected regions.

Mechanistic and future prospects in rhizospheric engineering for agricultural contaminants removal, soil health restoration, and management of climate change stress

Climate change, food insecurity, and agricultural pollution are all serious challenges in the twenty-first century, impacting plant growth, soil quality, and food security. Innovative techniques are required to mitigate these negative outcomes. Toxic heavy metals (THMs), organic pollutants (OPs), and emerging contaminants (ECs), as well as other biotic and abiotic stressors, can all affect nutrient availability, plant metabolic pathways, agricultural productivity, and soil-fertility. Comprehending the interactions between root exudates, microorganisms, and modified biochar can aid in the fight against environmental problems such as the accumulation of pollutants and the stressful effects of climate change. Microbes can inhibit THMs uptake, degrade organic pollutants, releases biomolecules that regulate crop development under drought, salinity, pathogenic attack and other stresses. However, these microbial abilities are primarily demonstrated in research facilities rather than in contaminated or stressed habitats. Despite not being a perfect solution, biochar can remove THMs, OPs, and ECs from contaminated areas and reduce the impact of climate change on plants. We hypothesized that combining microorganisms with biochar to address the problems of contaminated soil and climate change stress would be effective in the field. Despite the fact that root exudates have the potential to attract selected microorganisms and biochar, there has been little attention paid to these areas, considering that this work addresses a critical knowledge gap of rhizospheric engineering mediated root exudates to foster microbial and biochar adaptation. Reducing the detrimental impacts of THMs, OPs, ECs, as well as abiotic and biotic stress, requires identifying the best root-associated microbes and biochar adaptation mechanisms.

Plant growth-promoting rhizobacteria and biochar as bioeffectors and bioalleviators of drought stress in faba bean (Vicia faba L.)

Plants are subjected to a variety of abiotic stressors, including drought stress, that are fatal to their growth and ability to produce under natural conditions. Therefore, the present study was intended to investigate the drought tolerance potential of faba bean (Vicia faba L.) plants under the co-application of biochar and rhizobacteria, Cellulomonas pakistanensis (National Culture Collection of Pakistan (NCCP)11) and Sphingobacterium pakistanensis (NCCP246). The experiment was initiated by sowing the inoculated seeds with the aforementioned rhizobacterial strains in earthen pots filled with 3 kg of sand-mixed soil and 5% biochar. The morphology of biochar was observed with highly porous nature, along with the detection of various essential elements. The biochemical and physiological data showed that phenolic compounds and osmolytes were adversely affected by the induction of drought stress. However, the application of biochar and rhizobacteria boosted the level of flavonoids on average by 52.03%, total phenols by 50.67%, soluble sugar by 82.85%, proline by 76.81%, glycine betaine by 107.25%, and total protein contents by 89.18% in all co-treatments of biochar and rhizobacteria. In addition, stress indicator compounds, including malondialdehyde (MDA) contents and H2O2, were remarkably alleviated by 54.21% and 47.03%, respectively. Similarly, the amplitude of antioxidant enzymes including catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase was also enhanced by 63.80%, 80.95%, 37.87%, and 58.20%, respectively, in all co-treatments of rhizobacteria and biochar. Conclusively, biochar and rhizobacteria have a magnificent role in enhancing the drought tolerance potential of crop plants by boosting the physio-biochemical traits and enhancing the level of antioxidant enzymes.

Fabrication of engineered biochar for remediation of toxic contaminants in soil matrices and soil valorization

Biochar has emerged as an efficacious green material for remediation of a wide spectrum of environmental pollutants. Biochar has excellent characteristics and can be used to reduce the bioavailability and leachability of emerging pollutants in soil through adsorption and other physico-chemical reactions. This paper systematically reviewed previous researches on application of biochar/engineered biochar for removal of soil contaminants, and underlying adsorption mechanism. Engineered biochar are derivatives of pristine biochar that are modified by various physico-chemical and biological procedures to improve their adsorption capacities for contaminants. This review will promote the possibility to expand the application of biochar for restoration of degraded lands in the industrial area or saline soil, and further increase the useable area. This review shows that application of biochar is a win-win strategy for recycling and utilization of waste biomass and environmental remediation. Application of biochar for remediation of contaminated soils may provide a new solution to the problem of soil pollution. However, these studies were performed mainly in a laboratory or a small scale, hence, further investigations are required to fill the research gaps and to check real-time applicability of engineered biochar on the industrial contaminated sites for its large-scale application.

Effects of environmental metal and metalloid pollutants on plants and human health: exploring nano-remediation approach

Metal and metalloid pollutants severely threatens environmental ecosystems and human health, necessitating effective remediation strategies. Nanoparticle (NPs)-based approaches have gained significant attention as promising solutions for efficient removing heavy metals from various environmental matrices. The present review is focused on green synthesized NPs-mediated remediation such as the implementation of iron, carbon-based nanomaterials, metal oxides, and bio-based NPs. The review also explores the mechanisms of NPs interactions with heavy metals, including adsorption, precipitation, and redox reactions. Critical factors influencing the remediation efficiency, such as NPs size, surface charge, and composition, are systematically examined. Furthermore, the environmental fate, transport, and potential risks associated with the application of NPs are critically evaluated. The review also highlights various sources of metal and metalloid pollutants and their impact on human health and translocation in plant tissues. Prospects and challenges in translating NPs-based remediation from laboratory research to real-world applications are proposed. The current work will be helpful to direct future research endeavors and promote the sustainable implementation of metal and metalloid elimination.

Effect of naringenin based nanocomposites and pure naringenin on cumin (Cuminum cyminum L.) under drought stress

Key message

Naringenin based nanocomposite alleviate the harmful effects of drought stress in Cuminum cyminum and enhance carefully the plant tolerance against drought condition with different mechanisms.

Abstract

In the recent years, drought stress is considered as one of the most important stressful conditions for agricultural plants. Reducing the effects of drought on plants is a crucial need nowadays, which calls for innovative methods. Naringenin is one of the most known plant flavonoids with antioxidant properties. In the present work, a naringenin based nanocomposite containing carboxymethylcellulose (CMC) as carrier (CMC-Nar) with an average size of 65 nm were synthesized by coacervation method. In order to investigate the effect of CMC nanocomposites containing naringenin (CMC-Nar) and pure naringenin in modulating the effects of drought stress, cultivation of Cuminum cyminum (varieties: Isfahan and Kashan) was carried out in greenhouse conditions. Drought stress was imposed as 30% of the field capacity. Various physiological, biochemical, and phytochemical assays were performed after treating the plants in drought conditions (30%). The results indicated that treatment of nanocomposites (CMC-Nar) and pure naringenin at drought conditions increased growth and photosynthetic parameters such as germination, shoot and root fresh weight, shoot dry weight, and chlorophyll content of the Cumin. Stress markers such as malondialdehyde, H2O2, and electrolyte leakage decreased under the treatment of narinjenin and especially nanocomposites (CMC-Nar) under drought conditions. Moreover, under same condition and treatments, some biochemical parameters including soluble sugar and total protein increased but the activity of antioxidant enzymes and the level of free amino acids has gone down. Compatible Solutes (Proline and glycine betaine) also increased. There was an increase in phytochemical parameters such as total phenols, flavonoids, anthocyanin, and tannins under naringenin and nanocomposites (CMC-Nar) treatment in drought conditions. In general, nanocomposites and pure naringenin reduced the harmful effects of drought stress, and the ameliorating impacts of nanocomposites (CMC-Nar) are more than pure naringenin. According to the results: In most cases, the impact of drought stress was modulated to a greater extent by (CMC-Nar) nanocomposites in the Isfahan variety compared to the Kashan variety. This research tries to propose a new method to reduce the effects of drought stress on Cuminum cyminum.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01460-7.

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.

Genome-Wide Identification, Characterization, and Expression Analysis of the BES1 Family Genes under Abiotic Stresses in Phoebe bournei

The BRI1 EMS suppressor 1(BES1) transcription factor is a crucial regulator in the signaling pathway of Brassinosteroid (BR) and plays an important role in plant growth and response to abiotic stress. Although the identification and functional validation of BES1 genes have been extensively explored in various plant species, the understanding of their role in woody plants-particularly the endangered species Phoebe bournei (Hemsl.) Yang-remains limited. In this study, we identified nine members of the BES1 gene family in the genome of P. bournei; these nine members were unevenly distributed across four chromosomes. In our further evolutionary analysis of PbBES1, we discovered that PbBES1 can be divided into three subfamilies (Class I, Class II, and Class IV) based on the evolutionary tree constructed with Arabidopsis thaliana, Oryza sativa, and Solanum lycopersicum. Each subfamily contains 2-5 PbBES1 genes. There were nine pairs of homologous BES1 genes in the synteny analysis of PbBES1 and AtBES1. Three segmental replication events and one pair of tandem duplication events were present among the PbBES1 family members. Additionally, we conducted promoter cis-acting element analysis and discovered that PbBES1 contains binding sites for plant growth and development, cell cycle regulation, and response to abiotic stress. PbBES1.2 is highly expressed in root bark, stem bark, root xylem, and stem xylem. PbBES1.3 was expressed in five tissues. Moreover, we examined the expression profiles of five representative PbBES1 genes under heat and drought stress. These experiments preliminarily verified their responsiveness and functional roles in mediating responses to abiotic stress. This study provides important clues to elucidate the functional characteristics of the BES1 gene family, and at the same time provides new insights and valuable information for the regulation of resistance in P. bournei.

Phytoremediation of contaminated sediment combined with biochar: Feasibility, challenges and perspectives

The accumulation of contaminants in sediments is accelerated by human activities and poses a major threat to ecosystems and human health. In recent years, various remediation techniques have been developed for contaminated sediments. In this review, a bibliometric analysis of papers on sediment remediation indexed in the WOS database between 2009 and 2023 was conducted using VOSviewer. We describe the development of biochar and plants for sediment contaminant removal. However, the single processes of biochar remediation and phytoremediation can be impeded by (i) low efficiency, (ii) poor tolerance of plants towards pollutants, (iii) difficulty in biochar to degrade pollutants, and (iv) biochar aging causing secondary pollution. Fortunately, combination remediation, realized through the combination of biochar and plants, can overcome the shortcomings of their individual applications. Therefore, we suggest that the remediation of contaminants in sediments can be accomplished by combining biochar with macrophytes and considering multiple limiting factors. Here, we explore the challenges that co-remediation with biochar and macrophytes will face in achieving efficient and sustainable sediment remediation, including complex sediment environments, interaction mechanisms of biochar-macrophyte-microorganisms, emerging pollutants, and integrated life cycle assessments, which can provide references for combined biochar and plant remediation of sediments in the future.

Unlocking the potential of biochar in the remediation of soils contaminated with heavy metals for sustainable agriculture

Agricultural soils contaminated with heavy metals (HMs) impose a threat to the environmental and to human health. Amendment with biochar could be an eco-friendly and cost-effective option to decrease HMs in contaminated soil. This paper reviews the application of biochar as a soil amendment to immobilise HMs in contaminated soil. We discuss the technologies of its preparation, their specific properties, and effect on the bioavailability of HMs. Biochar stabilises HMs in contaminated soil, enhance the overall quality of the contaminated soil, and significantly reduce HM uptake by plants, making it an option in soil remediation for HM contamination. Biochar enhances the physical (e.g. bulk density, soil structure, water holding capacity), chemical (e.g. cation exchange capacity, pH, nutrient availability, ion exchange, complexes), and biological properties (e.g. microbial abundance, enzymatic activities) of contaminated soil. Biochar also enhances soil fertility, improves plant growth, and reduces the plant availability of HMs. Various field studies have shown that biochar application reduces the bioavailability of HMs from contaminated soil while increasing crop yield. The review highlights the positive effects of biochar by reducing HM bioavailability in contaminated soils. Future work is recommended to ensure that biochars offer a safe and sustainable solution to remediate soils contaminated with HMs.

Graphene oxide-based aerogel stimulates growth, mercury accumulation, photosynthesis-related gene expression, antioxidant efficiency and redox status in wheat under mercury exposure

Mercury (Hg) pollution is a global concern in cropland systems. Hg contamination causes a disruption in the growth, energy metabolism, redox balance, and photosynthetic activity of plants. In the removal of Hg toxicity, a recent critical strategy is the use of aerogels with biodegradability and biocompatibility. However, it is unknown how graphene oxide-based aerogels stimulate the defense systems in wheat plants exposed to Hg toxicity. Therefore, in this study, the photosynthetic, genetic, and biochemical effects of reduced graphene oxide aerogel treatments (gA; 50-100-250 mg L-1) were examined in wheat (Triticum aestivum) under Hg stress (50 μM HgCl2). The relative growth rate (RGR) significantly decreased (84%) in response to Hg stress. However, the reduced RGR and water relations (RWC) of wheat were improved by gA treatments. The impaired gas exchange levels (stomatal conductance, carbon assimilation rate, intercellular CO2 concentrations, and transpiration rate) caused by stress were reversed under Hg plus gAs. Additionally, stress hampered chlorophyll fluorescence (Fv/Fo, Fv/Fm), and under Hg toxicity the expression of psaA genes was reduced (>0.4-fold), but psaB gene was significantly up-regulated (>3-fold) which are the genes involved in PSI. By increasing expression patterns of both genes relating to PSI, gAs reversed the adverse consequences on Fv/Fo and Fv/Fm in the presence of excessive Hg concentration. The activities of glutathione S-transferase (GST), glutathione reductase (GR), catalase (CAT), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) decreased under Hg toxicity. On the other hand, the activities of superoxide dismutase (SOD), APX, GST, and glutathione peroxidase (GPX) increased following gA treatments against stress, leading to the successful elimination of toxic levels of H2O2 and lipid peroxidation (TBARS content) by decreasing the levels by about 30%, and 40%, respectively. By modulating enzyme/non-enzyme activity/contents including the AsA-GSH cycle, gAs contributed to the protection of the cellular redox state. Most important of all, gA applications were able to reduce Hg intake by approximately 66%. Therefore, these results showed that gAs were effective in highly inhibiting Hg uptake and could significantly increase wheat tolerance to toxicity by eliminating Hg-induced oxidative damage and inhibiting metabolic processes involved in photosynthesis. The findings obtained from the study provide a new perspective on the alleviation roles of reduced graphene oxide aerogels as an effective adsorbent for decreasing damages of mercury toxicity in wheat plants.

Effect of drought and soil heavy metal contamination on three maple species: a case study of Kastamonu University campus in Türkiye

This study investigated the effects of heavy metals and drought on tree drying in three maple species located in the Kastamonu Campus in northwestern Türkiye. Soil samples were taken from 0-30 cm depth under maple species, and some soil properties were analyzed. The standardized precipitation evapotranspiration index was calculated for the drought impression using 71 years of climate data. The severe drought has had its effect (1.516) since August 2020. There was an extreme drought in January and February 2021 (-2.032 and -2.076, respectively), and this drought effect lasted until August as a severe drought. Chromium concentration at maple species was almost twice higher than the Maximum Allowable Limit for Türkiye (> 100 mg kg-1). The highest nickel concentration was found under Acer pseudoplatanus (97.25 mg kg-1) and Acer negundo (108.13 mg kg-1). The sampling sites were nonsignificant for copper (p = 0.806), lead (p = 0.916), and zinc (p = 0.866) heavy metals. Phyllosticta minima and Phyllactinia marissallii were detected in maple trees. In conclusion, it is understood that drought and heavy metal accumulation (chromium, nickel) in the soil affect tree drying. Physiological drought was first seen in trees due to the lack of rainfall in 2020. Soils were contaminated with heavy metals, and finally, diseases were seen. These results show that adverse climate events due to global climate change will have a negative impact on the growth and development of maple species, as their severity is expected to increase in the next few years.

Enhancing soil resilience and crop physiology with biochar application for mitigating drought stress in durum wheat (Triticumdurum)

The use of biochar has recently garnered significant attention as an agricultural management technique highly endorsed by the scientific community. Biochar, owing to its high carbon content, contributes to increased organic matter storage in the soil, consequently enhancing crop growth. This study aimed to elucidate changes in physicochemical soil fertility and durum wheat (Triticum durum) var. Vitron production under the influence of three biochar doses (0 g/kg, 5 g/kg, and 15 g/kg of soil) in combination with varying levels of drought stress (100 %, 80 %, 40 %, and 20 % of field capacity 'FC'). Notably, we observed a substantial increase in all physicochemical soil parameters, except for active calcium carbonate equivalent (ACCE), which displayed lower values (8.78 ± 1.43 %) in soils treated with biochar compared to control soil (15.69 ± 4.03 %). The biochar dose of 5 g/kg yielded the highest moisture content (8.81 %) and pH value (7.83). However, the highest organic matter content (4.89 ± 0.17 %) and total calcium carbonate equivalent 'TCCE' (3.67 ± 0.48 %) were observed with the dose 15 g/kg. Nevertheless, regarding plant growth, no improvements were observed in terms of height and above-ground biomass (AGB). Conversely, leaf surface area exhibited significant changes with biochar application, along with an increase in chlorophyll pigment content. On the other hand, drought stress significantly hindered plant height, AGB, and leaf water reserves, resulting in values of 13.48 ± 1.60 cm, 1.57 ± 0.31g/plant, and 41.79 ± 1.67 %, respectively. The interaction between biochar and water stress appeared to mitigate and limit the impact of stress. Notably, an enhancement in organic matter storage and soil water reserves was observed. For example, the moisture content in the control soil was 6.95 %, while it increased to 12.76 % for 15g biochar/kg and 80 % FC. A similar trend was observed for organic matter, TCCE, and electrical conductivity. This effect positively influenced chlorophyll a and b content, as well as leaf water content. However, when stress was combined with biochar amendment, plant height and AGB decreased. The addition of biochar improved soil fertility and physiological parameters of wheat plants. Nevertheless, when combined with water stress, especially in cases of reduced water reserves, productivity did not witness any significant improvements.

A non-invasive method to predict drought survival in Arabidopsis using quantum yield under light conditions

BACKGROUND

Survival rate (SR) is frequently used to compare drought tolerance among plant genotypes. While a variety of techniques for evaluating the stress status of plants under drought stress conditions have been developed, determining the critical point for the recovery irrigation to evaluate plant SR often relies directly on a qualitative inspection by the researcher or on the employment of complex and invasive techniques that invalidate the subsequent use of the tested individuals.

RESULTS

Here, we present a simple, instantaneous, and non-invasive method to estimate the survival probability of Arabidopsis thaliana plants after severe drought treatments. The quantum yield (QY), or efficiency of photosystem II, was monitored in darkness (Fv/Fm) and light (Fv'/Fm') conditions in the last phase of the drought treatment before recovery irrigation. We found a high correlation between a plant's Fv'/Fm' value before recovery irrigation and its survival phenotype seven days after, allowing us to establish a threshold between alive and dead plants in a calibration stage. This correlation was maintained in the Arabidopsis accessions Col-0, Ler-0, C24, and Kondara under the same conditions. Fv'/Fm' was then applied as a survival predictor to compare the drought tolerance of transgenic lines overexpressing the transcription factors ATAF1 and PLATZ1 with the Col-0 control.

CONCLUSIONS

The results obtained in this work demonstrate that the chlorophyll a fluorescence parameter Fv'/Fm' can be used as a survival predictor that gives a numerical estimate of the Arabidopsis drought SR before recovery irrigation. The procedure employed to get the Fv'/Fm' measurements is fast, non-destructive, and requires inexpensive and easy-to-handle equipment. Fv'/Fm' as a survival predictor can be used to offer an overview of the photosynthetic state of the tested plants and determine more accurately the best timing for rewatering to assess the SR, especially when the symptoms of severe dehydration between genotypes are not contrasting enough to identify a difference visually.

Metal behavior and soil quality changes induced by the application of tailor-made combined biochar: An investigation at pore water scale

The remediation performance of biochar varies based on the biomass used for its production. Further innovation involves developing tailor-made biochar by combining different raw materials to compensate for the limitations of pure biochar. Therefore, tailor-made combined biochar produced from the co-pyrolysis of pig manure and invasive Japanese knotweed (P1J1), as well as biochars produced from these feedstocks separately, i.e., pure pig manure (PM) and pure Japanese knotweed (JK), were applied to Pb and As contaminated soil to evaluate the biochar-induced changes on soil properties, microbial activity, DOM, and metal and metalloids solubility at the soil pore water scale. Biochar application reduced soluble Pb, whereas enhanced the As mobility; the increased soil pH after biochar addition played a fundamental role in reducing the Pb solubility, as revealed by their significant negative correlation (r = -0.990, p < 0.01). In contrast, the release of dissolved P strongly influenced As mobilization (r = 0.949, p < 0.01), especially in P-rich PM and P1J1 treatments, while JK showed a marginal effect in mobilizing As. Soils treated with PM, P1J1, and JK mainly increased Gram-negative bacteria by 56 %, 52 %, and 50 %, respectively, compared to the control. Fluorescence excitation-emission matrix spectroscopy combined with parallel factor analysis identified three components in pore water DOM, C1 (long wavelength humic-like), C2 (short wavelength humic-like), and C3 (protein-like), which were dominant respectively in the P1J1, JK, and PM-added soil. A principal component analysis (PCA) confirmed that the PM and P1J1 had similar performance and were more associated with releasing P and Mg and specific DOM components (C1 and C3). Meanwhile, P1J1 supplemented soil OM/OC and K, similar to JK. The results of this study suggest that combined biochar P1J1 can comprehensively enhance soil quality, embodying the advantages of pure PM and JK biochar while overcoming their shortcomings.

Physiological and biochemical mechanisms of grain yield loss in fumitory (Fumaria parviflora Lam.) exposed to copper and drought stress

Soil contamination with heavy metals adversely affects plants growth, development and metabolism in many parts of the world including arid and semi-arid regions. The aim of this study was to investigate the single and combined effects of drought and copper (Cu) stresses on seed yield, and biochemical traits of Fumaria parviflora in a split - factorial experiment at Research Field of Payam-E-Noor university of Kerman during 2019. The collected seeds from two Cu contaminated regions were evaluated under drought and Cu (0, 50, 150, 300, and 400 mg/kg) stresses. Drought stress levels were depletion of 50% (D1), 70% (D2) and 85% (D3) soil available water. The individual effects of drought and copper stresses were similar to each other as both reduced seed yield. The highest seed yield was observed at Cu concentration of 50 mg/kg under non-drought stress conditions. The maximum values of malondialdehyde (0.47 µmol/g), proline (2.45 µmol/g FW), total phenolics (188.99 mg GAE/g DW) and total flavonoids (22.1 mg QE/g DW) were observed at 400 mg/kg Cu treatment. However, the strongest antioxidant activity (83.95%) through DPPH assay, and the highest total soluble carbohydrate (115.23 mg/g DW) content were observed at 300 and 150 mg/kg Cu concentration under severe drought stress, respectively. The highest amount of anthocyanin (2.18 µmol/g FW) was observed at 300 mg/kg Cu and moderate drought stress. The findings of this study showed a high tolerance of F. parviflora plant to moderate drought stress and Cu exposure up to 150 mg/kg by modulating defense mechanisms, where grain yield was slightly lower than that of control. The results could also provide a criterion for the selection of tolerance species like F. parviflora for better acclimatization under Cu mines and/or agricultural contaminated soils subjected to drought stress.

N,S-codoped biochar outperformed N-doped biochar on co-activation of H2O2 with trace dissolved Fe(Ⅲ) for enhanced oxidation of organic pollutants

Co-activation of H2O2 with biochar and iron sources together provides an attractive strategy for efficient removal of refractory pollutants, because it can solve the problems of slow Fe(Ⅱ) regeneration in Fenton/Fenton-like processes and of low •OH yield in biochar-activated process. In this study, a wood-derived biochar (WB) was modified by heteroatom doping for the objective of enhancing its reactivity toward co-activation of H2O2. The performance of the co-activated system using doped biochars and trace dissolved Fe(Ⅲ) on oxidation of organic pollutants was evaluated for the first time. The characterizations using X-ray photoelectron spectroscopy (XPS), Raman spectra and electrochemical analyses indicate that heteroatom doping introduced more defects in biochar and improved its electron transfer capacity. The oxidation experiments show that heteroatom doping improved the performance of biochar in the co-activated process, in which the N,S-codoped biochar (NSB) outperformed the N-doped biochar (NB) on oxidation of pollutants. The reaction rate constant (kobs) for oxidation of sulfadiazine in NSB + Fe + H2O2 is 2.25 times that in NB + Fe + H2O2, and is 72.9 times that in the Fenton-like process without biochar, respectively. The mechanism investigations indicate that heteroatom doping enhanced biochar's reactivity on catalyzing the decomposition of H2O2 and on reduction of Fe(Ⅲ) due to the improved electron transfer/donation capacity. In comparison with N-doping, N,S-codoping provided additional electron donor (thiophenic C-S-C) for faster regeneration of Fe(Ⅱ) with less amount of doping reagent used. Furthermore, co-activation with NSB maintained to be efficient at a milder acidic pH than Fenton/Fenton-like processes, and can be used for oxidation of different pollutants and in real water. Therefore, this research provides a novel, sustainable and cost-efficient method for oxidation of refractory pollutants.

Selenium-Priming mediated growth and yield improvement of turnip under saline conditions

Salt toxicity is one of the foremost environmental stresses that declines nutrient uptake, photosynthetic activity and growth of plants resulting in a decrease in crop yield and quality. Seed priming has become an emergent strategy to alleviate abiotic stress and improve plant growth. During the current study, turnip seed priming with sodium selenite (Na2SeO3) was investigated for its ability to mitigate salt stress. Turnip (Brassica rapa L. var. Purple Top White Globe) seeds primed with 75, 100, and 125 μML-1 of Se were subjected to 200 mM salt stress under field conditions. Findings of the current field research demonstrated that salt toxicity declined seed germination, chlorophyll content, and gas exchange characteristics of B. rapa seedling. Whereas, Se-primed seeds showed higher germination rate and plant growth which may be attributed to the decreased level of hydrogen peroxide (H2O2) and malondialdehyde (MDA) decreased synthesis of proline (36%) and besides increased total chlorophyll (46%) in applied turnip plants. Higher expression levels of genes encoding antioxidative activities (CAT, POD, SO,D and APX) mitigated oxidative stress induced by the salt toxicity. Additionally, Se treatment decreased Na+ content and enhanced K+ content resulting in elevated K+/Na+ ratio in the treated plants. The in-silico assessment revealed the interactive superiority of Se with antioxidant enzymes including CAT, POD, SOD, and APX as compared to sodium chloride (NaCl). Computational study of enzymes-Se and enzymes-NaCl molecules also revealed the stress ameliorative potential of Se through the presence of more Ramachandran-favored regions (94%) and higher docking affinities of Se (-6.3). The in-silico studies through molecular docking of Na2SeO3, NaCl, and ROS synthesizing enzymes (receptors) including cytochrome P450 (CYP), lipoxygenase (LOX), and xanthine oxidase (XO), also confirmed the salt stress ameliorative potential of Se in B. rapa. The increased Ca, P, Mg, and Zn nutrients uptake nutrients uptake in 100 μML-1 Se primed seedlings helped to adjust the stomatal conductivity (35%) intercellular CO2 concentration (32%), and photosynthetic activity (41%) resulting in enhancement of the yield attributes. More number of seeds per plant (6%), increased turnip weight (115 gm) root length (17.24 cm), root diameter (12 cm) as well as turnip yield increased by (9%tons ha-1) were recorded for 100 μML-1 Se treatment under salinity stress. Findings of the current research judiciously advocate the potential of Se seed priming for salt stress alleviation and growth improvement in B. rapa.

Soil acidification and salinity: the importance of biochar application to agricultural soils

Soil acidity is a serious problem in agricultural lands as it directly affects the soil, crop production, and human health. Soil acidification in agricultural lands occurs due to the release of protons (H+) from the transforming reactions of various carbon, nitrogen, and sulfur-containing compounds. The use of biochar (BC) has emerged as an excellent tool to manage soil acidity owing to its alkaline nature and its appreciable ability to improve the soil's physical, chemical, and biological properties. The application of BC to acidic soils improves soil pH, soil organic matter (SOM), cation exchange capacity (CEC), nutrient uptake, microbial activity and diversity, and enzyme activities which mitigate the adverse impacts of acidity on plants. Further, BC application also reduce the concentration of H+ and Al3+ ions and other toxic metals which mitigate the soil acidity and supports plant growth. Similarly, soil salinity (SS) is also a serious concern across the globe and it has a direct impact on global production and food security. Due to its appreciable liming potential BC is also an important amendment to mitigate the adverse impacts of SS. The addition of BC to saline soils improves nutrient homeostasis, nutrient uptake, SOM, CEC, soil microbial activity, enzymatic activity, and water uptake and reduces the accumulation of toxic ions sodium (Na+ and chloride (Cl-). All these BC-mediated changes support plant growth by improving antioxidant activity, photosynthesis efficiency, stomata working, and decrease oxidative damage in plants. Thus, in the present review, we discussed the various mechanisms through which BC improves the soil properties and microbial and enzymatic activities to counter acidity and salinity problems. The present review will increase the existing knowledge about the role of BC to mitigate soil acidity and salinity problems. This will also provide new suggestions to readers on how this knowledge can be used to ameliorate acidic and saline soils.

Heavy Metal Induced Oxidative Stress Mitigation and ROS Scavenging in Plants

Although trace elements are essential for life, environmental contamination due to metal accumulation and overuse in various sectors, such as healthcare, agriculture, industry, and cosmetics, poses significant health concerns. Exposure of plants to heavy metals leads to the overproduction of reactive oxygen species (ROS) due to their ability to change mitochondrial membrane permeability and restrict the action of ROS clearance enzymes in the cellular antioxidant system. The interaction of ROS with cellular membranes, heavy-metal-induced interactions directly or indirectly with different macromolecules, and signaling pathways leads to the accumulation of environmental pollutants and oxidative stress in exposed organisms. The heavy metal-ROS-cell signaling axis affects various pathological processes such as ATP depletion, excess ROS production, mitochondrial respiratory chain damage, decoupling of oxidative phosphorylation, and mitochondrial death. This review focuses on discussing the toxic effects of different heavy metals on plants, with particular emphasis on oxidative stress, its consequences, and mitigation strategies.

Efficacy of Carbon Nanodots and Manganese Ferrite (MnFe2O4) Nanoparticles in Stimulating Growth and Antioxidant Activity in Drought-Stressed Maize Inbred Lines

Despite being the third most-consumed crop, maize (Zea mays L.) is highly vulnerable to drought stress. The predominant secondary metabolite in plants is phenolic acids, which scavenge reactive oxygen species to minimize oxidative stress under drought stress. Herein, the effect of carbon nanodots (CND) and manganese ferrite (MnFe2O4) nanoparticles (NP) on the drought stress tolerance of maize has been studied. The experimental results revealed that the highest leaf blade length (54.0 cm) and width (3.9 cm), root length (45.2 cm), stem diameter (11.1 mm), root fresh weight (7.0 g), leaf relative water content (84.8%) and chlorogenic (8.7 µg/mL), caffeic (3.0 µg/mL) and syringic acid (1.0 µg/mL) contents were demonstrated by CND-treated (10 mg L-1) inbred lines (GP5, HW19, HCW2, 17YS6032, HCW3, HCW4, HW7, HCW2, and 16S8068-9, respectively). However, the highest shoot length (71.5 cm), leaf moisture content (83.9%), shoot fresh weight (12.5 g), chlorophyll content (47.3), and DPPH free radical scavenging activity (34.1%) were observed in MnFe2O4 NP-treated (300 mg L-1) HF12, HW15, 11BS8016-7, HW15, HW12, and KW7 lines, respectively. The results indicate that CND and MnFe2O4 NP can mitigate drought stress effects on different accessions of the given population, as corroborated by improvements in growth and physio-biochemical traits among several inbred lines of maize.

Phenylalanine supply alleviates the drought stress in mustard (Brassica campestris) by modulating plant growth, photosynthesis, and antioxidant defense system

Mustard (Brassica campestris L.) is a major oilseed crop that plays a crucial role in agriculture. Nevertheless, a number of abiotic factors, drought in particular, significantly reduce its production. Phenylalanine (PA) is a significant and efficacious amino acid in alleviating the adverse impacts of abiotic stressors, such as drought. Thus, the current experiment aimed to evaluate the effects of PA application (0 and 100 mg/L) on brassica varieties i.e., Faisal (V1) and Rachna (V2) under drought stress (50% field capacity). Drought stress reduced the shoot length (18 and 17%), root length (12.1 and 12.3%), total chlorophyll contents (47 and 45%), and biological yield (21 and 26%) of both varieties (V1 and V2), respectively. Foliar application of PA helped overcome drought-induced losses and enhanced shoot length (20 and 21%), total chlorophyll contents (46 and 58%), and biological yield (19 and 22%), whereas reducing the oxidative activities of H2O2 (18 and 19%), MDA concentration (21 and 24%), and electrolyte leakage (19 and 21%) in both varieties (V1 and V2). Antioxidant activities, i.e., CAT, SOD, and POD, were further enhanced under PA treatment by 25, 11, and 14% in V1 and 31, 17, and 24% in V2. Overall findings suggest that exogenous PA treatment reduced the drought-induced oxidative damage and improved the yield, and ionic contents of mustard plants grown in pots. It should be emphasized, however, that studies examining the impacts of PA on open-field-grown brassica crops are still in their early stages, thus more work is needed in this area.

Indigenously produced biochar retains fertility in sandy soil through unique microbial diversity sustenance: a step toward the circular economy

Introduction

Agricultural productivity in the arid hot desert climate of UAE is limited by the unavailability of water, high temperature, and salt stresses. Growing enough food under abiotic stresses and decreasing reliance on imports in an era of global warming are a challenge. Biochar with high water and nutrient retention capacity and acid neutralization activity is an attractive soil conditioner. This study investigates the microbial community in the arid soil of Dubai under shade house conditions irrigated with saline water and the shift in the microbial community, following 1 year of amendment with indigenously prepared biochar from date palm waste.

Methods

Amplicon sequencing was used to elucidate changes in bacterial, archaeal, and fungal community structures in response to long-term biochar amendment. Samples were collected from quinoa fields receiving standard NPK doses and from fields receiving 20 and 30 tons ha^-1 of biochar, in addition to NPK for 1 year. Water holding capacity, pH, electrical conductivity, calcium, magnesium, chloride, potassium, sodium, phosphorus, total carbon, organic matter, and total nitrogen in the soil from biochar-treated and untreated controls were determined.

Results and discussion

The results show that soil amendment with biochar helps retain archaeal and bacterial diversity. Analysis of differentially abundant bacterial and fungal genera indicates enrichment of plant growth-promoting microorganisms. Interestingly, many of the abundant genera are known to tolerate salt stress, and some observed genera were of marine origin. Biochar application improved the mineral status and organic matter content of the soil. Various physicochemical properties of soil receiving 30 tons ha^-1 of biochar improved significantly over the control soil. This study strongly suggests that biochar helps retain soil fertility through the enrichment of plant growth-promoting microorganisms.