Biochar mitigates arsenic-induced human health risks and phytotoxicity in quinoa under saline conditions by modulating ionic and oxidative stress responses

Investigation of salt tolerance in cotton germplasm by analyzing agro-physiological traits and ERF genes expression

The development of genotypes that can tolerate high levels of salt is crucial for the efficient use of salt-affected land and for enhancing crop productivity worldwide. Therefore, incorporating salinity tolerance is a critical trait that crops must possess. Salt resistance is a complex character, controlled by multiple genes both physiologically and genetically. To examine the genetic foundation of salt tolerance, we assessed 16 F1 hybrids and their eight parental lines under normal and salt stress (15 dS/m) conditions. Under salt stress conditions significant reduction was observed for plant height (PH), bolls/plant (NBP), boll weight (BW), seed cotton yield (SCY), lint% (LP), fiber length (FL), fiber strength (FS), potassium to sodium ratio (K+/Na+), potassium contents (K+), total soluble proteins (TSP), carotenoids (Car) and chlorophyll contents. Furthermore, the mean values for hydrogen peroxide (H2O2), sodium contents (Na+), catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and fiber fineness (FF) were increased under salt stress. Moderate to high heritability and genetic advancement was observed for NBP, BW, LP, SCY, K+/Na+, SOD, CAT, POD, Car, TSP, FL, and FS. Mean performance and multivariate analysis of 24 cotton genotypes based on various agro-physiological and biochemical parameters suggested that the genotypes FBS-Falcon, Barani-333, JSQ-White Hold, Ghauri, along with crosses FBS-FALCON × JSQ-White Hold, FBG-222 × FBG-333, FBG-222 × Barani-222, and Barani-333 × FBG-333 achieved the maximum values for K+/Na+, K+, TSP, POD, Chlb, CAT, Car, LP, FS, FL, PH, NBP, BW, and SCY under salt stress and declared as salt resistant genotypes. The above-mentioned genotypes also showed relatively higher expression levels of Ghi-ERF-2D.6 and Ghi-ERF-7A.6 at 15 dS/m and proved the role of these ERF genes in salt tolerance in cotton. These findings suggest that these genotypes have the potential for the development of salt-tolerant cotton varieties with desirable fiber quality traits.

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.

Effect of silicon nanoparticle-based biochar on wheat growth, antioxidants and nutrients concentration under salinity stress

Globally, salinity is an important abiotic stress in agriculture. It induced oxidative stress and nutritional imbalance in plants, resulting in poor crop productivity. Applying silicon (Si) can improve the uptake of macronutrients. On the other hand, using biochar as a soil amendment can also decrease salinity stress due to its high porosity, cation exchange capacity, and water-holding capacity. That's why the current experiment was conducted with novelty to explore the impact of silicon nanoparticle-based biochar (Si-BC) on wheat cultivated on salt-affected soil. There were 3 levels of Si-BC, i.e., control (0), 1% Si-BC1, and 2.5% Si-BC2 applied in 3 replicates under 0 and 200 mM NaCl following a completely randomized design. Results showed that treatment 2.5% Si-BC2 performed significantly better for the enhancement in shoot and root length, shoot and root fresh weight, shoot and root dry weight, number of leaves, number of tillers, number of spikelets, spike length, spike fresh and dry weight compared to control under no stress and salinity stress (200 mM NaCl). A significant enhancement in chlorophyll a (~ 18%), chlorophyll b (~ 22%), total chlorophyll (~ 20%), carotenoid (~ 60%), relative water contents (~ 58%) also signified the effectiveness of treatment 2.5% Si-BC2 than control under 200 mM NaCl. In conclusion, treatment 2.5% Si-BC2 can potentially mitigate the salinity stress in wheat by regulating antioxidants and improving N, K concentration, and gas exchange attributes while decreasing Na and Cl concentration and electrolyte leakage. More investigations at the field level are recommended for the declaration of treatment 2.5% Si-BC2 as the best amendment for alleviating salinity stress in different crops under variable climatic conditions.

Potential Development of Biochar in Africa as an Adaptation Strategy to Climate Change Impact on Agriculture

One of the most important obstacles to increasing agricultural production yields worldwide, especially in developing economies such as those in Africa is the continued degradation of soils due to climate change. In response to this threat, one of the strategies advocated is biochar technology, which is one of the emerging sustainable and climate-friendly soil amendments. This article reviews a brief description of biochar, the advantages and disadvantages of its use, and the prospects for developing its potential impact on agricultural productivity in African countries with a case study in Burkina Faso. Biochar is mainly useful for soil carbon sequestration, increasing and maintaining soil fertility, environmental management, and as a renewable energy source. However, it can have secondary effects including negative impacts on human health, pollution, and water quality. Furthermore, the positive results of biochar use in Africa suggest a prospect for ensuring the feasibility of biochar technology in policy decisions as a sustainable alternative to agricultural land management in the combat against climate change. As recommendations, a combination of improved seed varieties, and SWC (Soil and Water Conservation) techniques with the application of Biochar will be a perfect innovation for an intelligent adaptation practice to the destructive action of climate change in agriculture.

Influence of biochar produced from negative pressure-induced carbonization on transformation of potentially toxic metal(loid)s concerning plant physiological characteristics in industrially contaminated soil

Soil contamination and its subsequent impact on the food chain is a pressing challenge in the present day. The application of biochar has demonstrated a significant and positive effect on soil health, thereby enhancing plant growth and development. However, the application of biochar (BC) produced from negative pressure-induced carbonization to mitigate metal(loid) contamination is a new strategy that has been studied in current research. Results depicted that the application of biochar derived from the negative pressure carbonization (vacuum-assisted biochar (VBC) has a significant (p ≤ 0.05) positive impact on plant growth and physiological characteristics by influencing immobilization and speciation of metal(loid) in the soil system. Moreover, the interactive effect of VBC on physiological characteristics (photosynthesis, gas exchange, and chlorophyll contents) and antioxidant activities of maize (Zea mays L.) was significantly (p ≤ 0.05) positive by confining the translocation and movement of metal(loid)s to the aerial part of the maize plant. X-ray diffraction (XRD) provided information on the structural and chemical changes induced by the VBC-500 °C explaining metal(loid) adsorption onto mineral surfaces and complexation that can affect their mobility, availability, and toxicity in the contaminated soil. Fourier transform infrared spectroscopy (FTIR) further provided a more detailed understanding of the metal(loid)s and biochar complexation mechanisms influenced by VBC-based functional groups -OH, C-Hn, -COOH, CO, C-O-C, CC, C-O, C-H, OH, and C-C in the binding process. These results suggest that the application of biochar prepared at 500 °C under negative pressure-induced carbonization conditions to the soil is the most efficient way to reduce the uptake and transfer of metal(loid)s by influencing their mobility and availability in the soil-plant system.

Salicylic Acid- and Potassium-Enhanced Resilience of Quinoa (Chenopodium quinoa Willd.) against Salinity and Cadmium Stress through Mitigating Ionic and Oxidative Stress

Salinity and cadmium (Cd) contamination of soil are serious environmental issues threatening food security. This study investigated the role of salicylic acid (SA) and potassium (K) in enhancing the resilience of quinoa against the combined stress of salinity and Cd. Quinoa plants were grown under NaCl (0, 200 mM) and Cd (0, 100 µM) stress, with the addition of 0.1 mM SA and 10 mM K, separately or in combination. The joint stress of Cd and NaCl caused >50% decrease in plant growth, chlorophyll contents, and stomatal conductance compared to the control plants. The higher accumulation of Na and Cd reduced the uptake of K in quinoa tissues. The joint stress of salinity and Cd caused an 11-fold increase in hydrogen peroxide and 13-fold increase in thiobarbituric acid reactive substances contents, and caused a 61% decrease in membrane stability. An external supply of 0.1 mM SA and 10 mM K helped plants to better adapt to salinity and Cd stress with less of a reduction in plant biomass (shoot 19% and root 24%) and less accumulation of Na and Cd in plant tissues. The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) were enhanced by 11-fold, 10-fold, 7.7-fold, and 7-fold, respectively, when SA and K were applied together to the plants subjected to the joint stress of Cd and salinity. Based on the values of the bioconcentration factor (>1), the translocation factor (<1), and the higher tolerance index, it was clear that Cd-contaminated, salty soils could be stabilized with quinoa under the combined supply of SA and K.

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.

Multivariate characterization of biochemical and physiological attributes of quinoa (Chenopodium quinoa Willd.) genotypes exposed to nickel stress: implications for phytoremediation

Nickel (Ni) is an essential element for plants; however, excessive uptake of Ni causes phytotoxicity in plants. The phytotoxic effects of Ni on the growth of quinoa and the underlaying mechanisms for Ni tolerance and phytoremediation are unknown. Hence, the present study investigated Ni tolerance and accumulation potential of two quinoa genotypes (Puno and Vikinga). Both genotypes were exposed to Ni (0, 100, 200, 300, and 400 μM) in half-strength Hoagland nutrient solution for three weeks. Results revealed that shoot and root lengths, biomass, stomatal conductance, and chlorophyll contents were decreased with the increase of Ni concentration. Excessive uptake of Ni resulted in the limited uptake of K by root and its translocation to shoot. Ni caused oxidative stress in plants by overproduction of H2O2 leading to lipid peroxidation of cell membranes. Genotype Puno showed greater tolerance to Ni than Vikinga based on tolerance index, lower bioconcentration factor, and translocation factor. Greater tolerance of Puno was mainly attributed to improved physiological responses and amelioration of oxidative stress by induction of antioxidant enzymes such as peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). It was revealed through multivariate analysis that Ni had strong negative correlations with growth and physiological attributes and positive associations with oxidative stress attributes. The study demonstrated genotypic variation in response to varying Ni concentrations and Puno performed better than Vikinga for phytostabilization of Ni-contaminated soils.

The critical role of biochar to mitigate the adverse impacts of drought and salinity stress in plants

Drought stress (DS) is a potential abiotic stress that is substantially reducing crop productivity across the globe. Likewise, salinity stress (SS) is another serious abiotic stress that is also a major threat to global crop productivity. The rapid climate change increased the intensity of both stresses which pose a serious threat to global food security; therefore, it is urgently needed to tackle both stresses to ensure better crop production. Globally, different measures are being used to improve crop productivity under stress conditions. Among these measures, biochar (BC) has been widely used to improve soil health and promote crop yield under stress conditions. The application of BC improves soil organic matter, soil structure, soil aggregate stability, water and nutrient holding capacity, and the activity of both beneficial microbes and fungi, which leads to an appreciable increase in tolerance to both damaging and abiotic stresses. BC biochar protects membrane stability, improves water uptake, maintains nutrient homeostasis, and reduces reactive oxygen species production (ROS) through enhanced antioxidant activities, thereby substantially improving tolerance to both stresses. Moreover, BC-mediated improvements in soil properties also substantially improve photosynthetic activity, chlorophyll synthesis, gene expression, the activity of stress-responsive proteins, and maintain the osmolytes and hormonal balance, which in turn improve tolerance against osmotic and ionic stresses. In conclusion, BC could be a promising amendment to bring tolerance against both drought and salinity stresses. Therefore, in the present review, we have discussed various mechanisms through which BC improves drought and salt tolerance. This review will help readers to learn more about the role of biochar in causing drought and salinity stress in plants, and it will also provide new suggestions on how this current knowledge about biochar can be used to develop drought and salinity tolerance.

Responses of individual and combined polystyrene and polymethyl methacrylate nanoplastics on hormonal content, fluorescence/photochemistry of chlorophylls and ROS scavenging capacity in Lemna minor under arsenic-induced oxidative stress

Nanoplastics alter the adverse impacts of hazardous contaminants such as heavy metals by changing their adsorption and accumulation. Few findings are available on the interaction between nanoplastic and heavy metals in plants. However, there is no report on the mechanisms for removing metal stress-mediated oxidative damage by the combination treatments of nanoplastics. To address this lack of information, polystyrene nanoplastic (PS, 100 mg L^-1) and polymethyl methacrylate (PMMA, 100 mg L^-1) were hydroponically applied to Lemna minor exposed to arsenate (As, 100 μM) for 7 days. PS or PMMA caused a reduction in the contents of N, P, K, Ca, Mg and Mn, but the improved contents were detected in the presence of PS or PMMA plus As stress. The hormone contents (auxin, gibberellic acid, cytokinin, salicylic acid and jasmonic acid) reduced by stress were re-arranged through PS or PMMA applications. Based on chlorophyll efficiency, fluorescence kinetics and performance of PSII, the impaired photosynthesis by As stress was improved via PS or PMMA applications. This alleviation did not continue under the combined form of PS and PMMA in As-applied plants. All analyzed antioxidant activity (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR)) decreased or unchanged under As, PS or PMMA. Due to the inactivation of the defense system, L. minor had high levels of hydrogen peroxide (H₂O₂) and thiobarbituric acid reactive substances (TBARS), showing lipid peroxidation. After As toxicity, induvial applications of PS or PMMA indicated the activated enzyme capacity (SOD, POX, GST and GPX) and upregulated AsA/DHA, GSH/GSSG and redox state of GSH, which facilitated the removal of radical accumulation. The efficiency of the antioxidant system in As + PS + PMMA-applied L. minor was not enough to remove damage induced by As stress; hereby, TBARS and H₂O₂ contents were similar to the As-treated group. Our findings from alone or combined application of PS and PMMA provide new information to advance the tolerance mechanism against As exposure in L. minor.

Potential of magnetic quinoa biosorbent composite and HNO3 treated biosorbent for effective sequestration of chromium (VI) from contaminated water

The present study aims to prepare novel quinoa biosorbent (QB), acid activated QB (QB/Acid) and its nanocomposite with magnetic nanoparticles (QB/MNPs) for batch scale Cr removal from contaminated water. The Cr adsorption was systematically studied at different pH (2-9), adsorbent dosage (1-3 g/L), initial concentration (25-200 mg/L), contact time (180 min) and competing ions in water. Maximum Cr adsorption was observed onto QB/MNPs (57.4 mg/L), followed by QB/Acid (46.35 mg/g) and QB (39.9 mg/g). The Cr removal by QB/MNPs was higher than QB/Acid and QB. Results revealed that the highest Cr removal was obtained at optimum pH 4, 25 mg/L, and 2 g/L dosage. The FTIR spectra displayed various functional groups on adsorbents surface serving as a potential scaffold to remove Cr from contaminated water. The equilibrium and kinetic Cr adsorption data best fitted with Freundlich and pseudo-second order models, respectively (R² ≥ 0.96). The QB/MNPs showed excellent reusability in five adsorption/desorption cycles (4.7% decline) with minor leaching of Fe (below threshold level). The coexisting ions in groundwater showed an inhibitory effect on Cr sequestration (5%) from water. The comparison of Cr adsorption by QB/MNPs and QB/Acid showed better potential for Cr sequestration than various previously explored adsorbents in the literature.

The involvement of hydrogen sulphide in melatonin-induced tolerance to arsenic toxicity in pepper (Capsicum annuum L.) plants by regulating sequestration and subcellular distribution of arsenic, and antioxidant defense system

Melatonin (MT) and hydrogen sulphide (H₂S) are recognised as vital biomolecules actively taking part in plant defence systems as free radical scavengers and antioxidants against a myriad of biotic and abiotic stressors. However, it has been yet unknown in plants subjected to arsenic (As) toxicity whether or not H₂S interacts with MT to regulate endogenous antioxidant defence system. Prior to beginning As stress (As-S) treatments, MT (0.10 mM) was applied externally to plants daily for three days. AsS was then started for two weeks with As(V) (0.1 mM as Na₂HAsO₄·7H₂O). The treatment of As reduced plant biomass (24.4%) and chlorophyll a (51.7%), chlorophyll b (25.9%), while it increased subcellular As in roots and leaves, levels of glutathione (GSH), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), methylglyoxal (MG), H₂S and phytochelatins (PCs) in pepper plants. In As-stressed pepper plants, the application of MT increased plant biomass (16.3%), chlorophyll a (52.7%), chlorophyll b (28.2%), antioxidant enzymes' activities, and H₂S accumulation, while it lowered the concentrations of MDA and H₂O₂. In As-treated plants, GSH and phytochelatins (PCs) were increased by MT by regulating As sequestration to make it harmless. The addition of MT increased As accumulation in the vacuoles of roots and caused the soluble fraction of As in vacuoles to become less toxic to vital organelles. MT-induced tolerance to As stress was further enhanced using NaHS, a source of H₂S. Hypotaurine (0.1 mM HT), a H₂S scavenger, was applied to the control and As-stressed plants together with MT and MT + NaHS to determine whether H₂S was implicated in MT-induced increased As-S tolerance. By reducing H₂S generation in pepper plants, HT counteracted the beneficial effects of MT, whereas the addition of NaHS to MT + HT restored the negative effects of HT, proving that H₂S is necessary for the pepper plants As-stress tolerance caused by MT.

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

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

Antioxidants as modulators of arsenic-induced oxidative stress tolerance in plants: An overview

Arsenic (As) is a highly toxic contaminant in the environment. Although both inorganic and organic types of arsenic exist in the environment, the most common inorganic forms of As that adversely affect plants are arsenite (As III) and arsenate (As V). Despite no evidence for As being essential for plant growth, exposure of roots to this element can cause its uptake primarily via transporters responsible for the transport of essential mineral nutrients. Arsenic exposure even at low concentrations disturbs the plant normal functioning via excessive generation of reactive oxygen species, a condition known as oxidative stress leading to an imbalance in the redox system of the plant. This is associated with considerable damage to the cell components thereby impairing normal cellular functions and activation of several cell survival and cell death pathways. To counteract this oxidative disorder, plants possess natural defense mechanisms such as chemical species and enzymatic antioxidants. This review considers how different types of antioxidants participate in the oxidative defense mechanism to alleviate As stress in plants. Since the underlying phenomena of oxidative stress tolerance are not yet fully elucidated, the potential for "Omics" technologies to uncover molecular mechanisms are discussed. Various strategies to improve As-induced oxidative tolerance in plants such as exogenous supplementation of effective growth regulators, protectant chemicals, transgenic approaches, and genome editing are also discussed thoroughly in this review.

Physiological and biochemical characterization of Kalongi (Nigella sativa) against arsenic stress: Implications for human health risk assessment

Arsenic (As) is a toxic metalloid that exhibits a varying degree of toxicity in plants depending upon the redox status of its species. Elemental arsenic [As(0)] is the least toxic of all the As species, however, under conducive environmental conditions, it can be readily oxidized into toxic forms. The present experiment was designed to evaluate the deleterious effects of As when applied in As(0) form on the morpho-physiological attributes of Kalongi (Nigella sativa). Seeds of N. sativa were sown in soil contaminated with various levels of As (0, 1.875, 3.75, 7.5, 15.0, and 30.0 mg nA(0) kg^-1 soil). The results indicated that plant biomass and grain yield of N. sativa were not much affected by various levels of As except at 30 mg nA(0) kg^-1 soil. Activities of antioxidant enzymes (SOD, APX, POX, and CAT), phenolic contents, and carotenoids were enhanced in response to the overproduction of H₂O₂, subsequently inhibiting lipid peroxidation. Arsenic accumulation in different plant organs increased with increasing soil As levels in the given trend root > shoot > leaf > seedpod > seed. Arsenic uptake affected the uptake of other elements (P, Fe, Zn, K, Na, Ca). Adaptive changes in total chlorophyll contents, MDA contents, and antioxidant enzymatic defense mechanism in response to As stress suggest that the N. sativa is tolerant to moderate As stress. Therefore, this crop can be cultivated on moderately As-contaminated soils without any significant risks of economic losses and food chain contamination.

Nickel tolerance and phytoremediation potential of quinoa are modulated under salinity: multivariate comparison of physiological and biochemical attributes

Soils salinization along with heavy metals contamination is among the serious environmental menaces. The present experiment was conducted to study the combined influence of salinity and nickel (Ni) on growth and physiological attributes of quinoa (Chenopodium quinoa Willd.). Thirty-day-old healthy and uniform seedlings of quinoa genotype A7 were exposed to different concentrations of Ni (0, 100, 200, 400 µM), NaCl (0, 150, 300 mM) and their combinations for three weeks. Results indicated that plant growth, pigments and stomatal conductance decreased with increasing Ni concentrations in nutrient solution. Combining lower level of salt (150 mM NaCl) with Ni resulted in improvement in growth and physiological attributes of quinoa. However, the combined application of higher level of salt (300 mM NaCl) with Ni was more detrimental for plant growth and caused more oxidative stress (H₂O₂ and TBARS) than the alone treatments. The oxidative stress was mitigated by 5.5-fold, 5-fold and 15-fold increase in the activities of SOD, CAT and APX, respectively. The concentration of Na was increased, while K and Ni decreased under the combined treatment of Ni and salinity. Multivariate analysis revealed that a moderate level of salinity had positive effects on growth and Ni phytoremediation potential of quinoa. The higher tolerance index, bioconcentration factor and lower translocation factor depicted that quinoa genotype A7 can be cultivated for phytostabilization of Ni under salinity stress. It was concluded that NaCl salinity level of 150 mM is promising for increasing growth of quinoa on Ni contaminated soils.

Differential Uptake and Translocation of Cadmium and Lead by Quinoa: A Multivariate Comparison of Physiological and Oxidative Stress Responses

Contamination of soils with cadmium (Cd) and lead (Pb) has emerged as a serious environmental issue that reduces crop productivity. However, the metals tolerance and accumulation potential of quinoa (Chenopodium Quinoa Willd) under the combined stress of Cd and Pb has not yet been explored. In the present hydroponic study, the physiological and biochemical characteristics of quinoa exposed to Cd and Pb were explored. Four-week-old plants of quinoa genotype ‘Puno’ were grown under different concentrations of Cd (0, 50 and 100 µM), Pb (0, 250 and 500 µM) alone as well as in combinations. The results showed that with increasing Cd and Pb levels in the nutrient solution, the plant biomass, stomatal conductance and chlorophyll contents were decreased. However, the concurrent application of higher concentrations of Cd (100 µM) and Pb (500 µM) caused even more reduction in the plant biomass (more than 50% than the control) and physiological attributes. The combined application of Pb and Cd caused oxidative stress through an overproduction of H2O2 (10-fold) and TBARS (12.5-fold), leading to decrease in membrane stability (52%). The oxidative stress was alleviated by a 7-fold, 10-fold and 9-fold overactivation of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), respectively. An excessive uptake of Cd resulted in a limited uptake of Pb and K in the roots and shoots of quinoa plants. The Cd and Pb tolerance and uptake potential of Puno showed its ability to stabilize Cd and Pb in co-contaminated soils.

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

Use of untreated municipal wastewater (WW) contains toxic trace elements that pose a serious threat to the soil-plant-human continuum. The use of biochar (BC) is a promising approach to minimize trace element induced toxicity in the ecosystem. Therefore, the present study aims to evaluate the efficacy of BC derived from wheat straw and iron oxide nanoparticles doped biochar (IO-BC) to reduce trace element buildup in soil and plants that consequently affect tomato plant growth and physiological activity under WW irrigation. The BC and IO-BC were applied at four levels (0, 0.5, 1, and 1.5%) in WW irrigated soils. The results indicated that the addition of WW + BC and WW + IO-BC resulted in significant reduction in trace element mobility in soil. Interestingly, the application of WW + IO-BC (1.5%) was more effective in reducing trace element mobility and bioavailability in soil by 78% (As), 58% (Cr), 46% (Pb) and 50% (Cd) compared to WW irrigation, and thus reduced trace element accumulation and toxicity in plants. Results revealed that WW irrigation negatively affected tomato growth, fruit yield, physiology and antioxidative response. Addition of WW + BC and WW + IO-BC ameliorated the oxidative stress (up to 65% and 58% in H₂O₂ and MDA) and increased plant tolerance (up to 49% in POD and APX activity). The risk indices also showed minimum human health risk (H1 < 1) from tomato after the addition of BC or IO-BC in WW irrigated soils. It is concluded that IO-BC addition in WW irrigated soil could assist in reducing trace elements accumulation and toxicity in tomato and associated human health risks.

An assessment of integrated amendments of biochar and soil replacement on the phytotoxicity of metal(loid)s in rotated radish-soya bean-amaranth in a mining acidy soil

Knowledge is insufficient on feasible remediation techniques to agricultural soils contaminated by multiple heavy metal(loid)s with elevated concentrations and extreme acidy from acid mine drainages (AMD). We aimed to elucidate the effect of integrated biochar (BC) and soil replacement on improving the mining soil properties and then alleviating the phytotoxicity of As, Pb, Cd, Cu, and Zn on radish (Raphanus sativus L.)-soya bean (Glycine max Merr.) -amaranth (Amaranthus tricolor L.) rotation and the potential risk of crops to human health. Biochar and soil replacement showed outstanding effects on improving soil properties by increasing soil pH values, reducing available metal(loid)s, and enhancing the activity of catalase, urease and acid phosphatase. Also, the integrated technique regulated the physiological disorders of crops caused by metal(loid)s, specifically increasing chlorophyll content and reducing malondialdehyde (MDA) in the three crops, and reducing the content of metal(loid)s in edible parts of plants. The combination of biochar and soil replacement exhibited better remediation effect than the single application of biochar or soil replacement, which played different roles in remediating mining farmland. Biochar exhibited efficacy in soil pH amelioration, metal stabilization and soil enzyme activity enhancement, while soil replacement alleviated metal(loid)s stress through the dilution effect. Among the 8 treatments, only biochar combined with 35% (S35BC) and 50% (S50BC) of replaced soil could achieve the safe production of the three crops under the three-season crop rotation.

Biochar and Chitosan Regulate Antioxidant Defense and Methylglyoxal Detoxification Systems and Enhance Salt Tolerance in Jute (Corchorus olitorius L.)

We investigated the role of biochar and chitosan in mitigating salt stress in jute (Corchorus olitorius L. cv. O-9897) by exposing twenty-day-old seedlings to three doses of salt (50, 100, and 150 mM NaCl). Biochar was pre-mixed with the soil at 2.0 g kg⁻¹ soil, and chitosan-100 was applied through irrigation at 100 mg L⁻¹. Exposure to salt stress notably increased lipid peroxidation, hydrogen peroxide content, superoxide radical levels, electrolyte leakage, lipoxygenase activity, and methylglyoxal content, indicating oxidative damage in the jute plants. Consequently, the salt-stressed plants showed reduced growth, biomass accumulation, and disrupted water balance. A profound increase in proline content was observed in response to salt stress. Biochar and chitosan supplementation significantly mitigated the deleterious effects of salt stress in jute by stimulating both non-enzymatic (e.g., ascorbate and glutathione) and enzymatic (e.g., ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase superoxide dismutase, catalase, peroxidase, glutathione S-transferase, glutathione peroxidase) antioxidant systems and enhancing glyoxalase enzyme activities (glyoxalase I and glyoxalase II) to ameliorate reactive oxygen species damage and methylglyoxal toxicity, respectively. Biochar and chitosan supplementation increased oxidative stress tolerance and improved the growth and physiology of salt-affected jute plants, while also significantly reducing Na⁺ accumulation and ionic toxicity and decreasing the Na⁺/K⁺ ratio. These findings support a protective role of biochar and chitosan against salt-induced damage in jute plants.

Effect of a Passivator Synthesized by Wastes of Iron Tailings and Biomass on the Leachability of Cd/Pb and Safety of Pak Choi (Brassica chinensis L.) in Contaminated Soil

Cadmium (Cd) and lead (Pb) carry a high heavy-metal-toxic risk for both animals and plants in soil. In this study, iron-based biochar (T-BC) was prepared by co-pyrolysis using wastes of iron tailings and biomass with urea as the functioning agents. Field-emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and toxicity-characteristic leaching procedure (TCLP) methods were employed to analyze the physicochemical characteristics of T-BC. Additionally, a pot trial was conducted to examine the effects of T-BC on the physiological characteristics of pak choi (Brassica campestris L.), the availability of heavy metals, and enzyme activities in the soils. The results show that toxic metals have been volatilized by the roasting process and immobilized within T-BC via the formation of stable metal-compounds during the co-pyrolysis process, which satisfies the requirements of a soil passivator. Incubation experiments showed that the DTPA-extractable Cd and Pb in contaminated soils decreased with an increasing amendment rate. Moreover, in the pot experiments, by adding 1% (w/w) T-BC into soils, the soils benefited from its large adsorption, complex precipitation, and immobilization capacity. Approximately 36% Cd and 29% Pb concentrations of edible parts in pak choi were reduced. The amendment proved promising for the stabilization of Cd and Pb in contaminated soils, while providing a strategy for solving the residual waste of tailings and biomass.