Toxic Chromium Research Articles

Physiological and transcriptomic evidence of antioxidative system and ion transport in chromium detoxification in germinating seedlings of soybean

Chromium (Cr) toxicity impairs the productivity of crops and is a major threat to food security worldwide. However, the effect of Cr toxicity on seed germination and transcriptome of germinating seedlings of soybean crop has not been fully explored. In this study, two Cr-tolerant lines (J82, S125) and two Cr-sensitive ones (LD1, RL) were screened out of twenty-one soybean (Glycine max L.) genotypes based on seed germination rate, seed germinative energy, seed germination index, and growth of germinating seedlings under 50 mg L−1 Cr treatment. We found that Cr stress inhibits the growth of soybean seed germinating seedlings due to the Cr-induced overaccumulation of reactive oxygen species (ROS). Significantly different levels of element contents, antioxidant enzyme activities, malondialdehyde content were observed in the four soybean genotypes with contrasting Cr tolerance. Further, a total of 13,777 differentially expressed genes (DEGs) were identified in transcriptomic sequencing and 1298 DEGs in six gene modules were found highly correlated with the physiological traits by weighted correlation network analysis (WGCNA) analysis. The DEGs encoding antioxidant enzymes, transcription factors, and ion transporters are proposed to confer Cr tolerance in soybean germinating seedlings by reducing the uptake and translocation of Cr, decreasing the level of ROS, and keeping the osmotic balance in soybean germinating seedings. In conclusion, our study provided a molecular regulation network on soybean Cr tolerance at seed germinating stage and identified candidate genes for molecular breeding of low Cr accumulation soybean cultivars.

Chromium toxicity and tolerance mechanisms in plants through cross-talk of secondary messengers: An overview of pathways and mechanisms

Environmental sources of chromium (Cr) such as solid waste, battery chemicals, industrial /waste, automotive exhaust emissions, mineral mining, fertilizers, and pesticides, have detrimental effects on plants. An excessive amount of Cr exposure can lead to toxic accumulations in human, animal, and plant tissues. In plants, diverse signaling molecules like hydrogen sulfide (H2S) and nitric oxide (NO) play multiple roles during Cr stress. Consequently, the molecular mechanisms of Cr toxicity in plants, such as metal binding, modifying enzyme activity, and damaging cells are examined by several studies. The reactive oxygen species (ROS) that are formed when Cr reacts with lipids, membranes, DNA, proteins, and carbohydrates are all responsible for damage caused by Cr. ROS regulate plant growth, programmed cell death (PCD), cell cycle, pathogen defense, systemic communication, abiotic stress responses, and growth. Plants accumulate Cr mostly through the root system, with very little movement to the shoots. The characterization of stress-inducible proteins and metabolites involved in Cr tolerance and cross-talk messengers has been made possible due to recent advances in metabolomics, transcriptomics, and proteomics. This review discusses Cr absorption, translocation, subcellular distribution, and cross-talk between secondary messengers as mechanisms responsible for Cr toxicity and tolerance in plants. To mitigate this problem, soil-plant systems need to be monitored for the biogeochemical behavior of Cr and the identification of secondary messengers in plants.

Study on histo-biochemical biomarkers of chromium induced toxicity in Labeorohita

Aquatic environment gets highly polluted due to the presence of heavy metals, which are usually discharged into water bodies because of rapid industrialization. The main purpose of this study is to evaluate the effects of chromium toxicity on histo-biochemical biomarkers of Labeo rohita. A total of 240 randomly selected fish were distributed into four aquaria (n = 20). Three groups designated as T1, T2 and T3 were exposed with 1/3rd, 1/5th and 1/10th of LC50 of chromium chloride, and the fourth group was chromium-free control (T0). Results showed a significant (p < 0.05) decrease in blood parameters such as hematocrit, red blood cells, hemoglobin, mean cell hemoglobin and platelets. In contrast, mean cell volume and white blood cell values increased significantly. The results obtained by comet assay showed that DNA damage was increased significantly (p < 0.05) in chromium-exposed groups compared to the control. At the histopathological level, observed alterations in the gill tissues are degeneration of epithelium, fusion of secondary lamellae, lamellar curling, hypertrophy, telangiectasis and oedema, while in the liver is necrosis, dilation of the vein, congestion of blood vessels, hepatocytes degeneration, melano-macrophage centers, pigmentation and hemorrhage. In the kidney, histological alterations such as glomerular destruction, necrosis, damaged blood vessels, oedema and pigmentation were seen. Those results suggest that chromium has the ability to bring variations DNA integrity, histopathology and blood of Labeo rohita.

Determination of glutathione in cells by capillary electrophoresis-laser induced fluorescence

Glutathione (GSH) is vital for oxidative stress resistance and heavy metals detoxification. It is significant to develop a sensitive and accurate quantitative GSH approach for the toxicity mechanism for studying heavy metals in cells. A high-sensitive capillary electrophoresis-laser induced fluorescence (CE-LIF) detection approach was proposed in this study to detect GSH content in cells. The approach employed HepG2 cells as an object and 2,3-naphthalenedicarboxaldehyde (NDA) with the active group of aromatic o-dialdehyde as a labeling reagent. The effects of buffer solution types, pH, additives on the GSH reaction rate with NDA, and the sensitivity of NDA-GSH were systematically investigated. The sensitivity of NDA-GSH and the reaction rate of GSH with NDA were compared in tris(hydroxymethyl)aminomethane (Tris) buffer solution at pH 7.4 or 9.2 and borate-Tris buffer solution at pH 9.2. The results revealed that the NDA-GSH sensitivity was the highest and the reaction rate of GSH and NDA was the fastest in borate buffer solution at pH 9.2. The effects of the four additives on the sensitivity of NDA-GSH were further compared. The best additive was revealed to be β-cyclodextrin (β-CD). GSH reacted with NDA to reach equilibrium within 5 min under the optimal experimental conditions, and the electrophoretic signal of NDA-GSH could be seen in 3 min. Quantitative analysis of GSH in HepG2 cells was performed using an external standard approach by determining a series of GSH standard solutions. The results revealed that the approach had a good linear relationship with the peak area vs. concentration (0.01-20.00 mmol/L) of GSH. The limit of detection (LOD) and limit of quantification (LOQ) of GSH were determined using signal-to-noise ratios of 3 (S/N=3) and 10 (S/N=10), which were 0.006 μmol/L and 0.020 μmol/L, respectively. The approach's spiked recoveries were 95.7%-112.6%, with relative standard deviations of the approach being 3.8%-5.0% (n=3). This approach offers high sensitivity, good stability, accuracy, and reliability. To study the relationship between the toxicity of arsenic and chromium on HepG2 cells and the content of GSH in HepG2 cells, the effects of arsenic and chromium with different valences on cell viability were analyzed. The results illustrated that the cytotoxicity of potassium dichromate (Cr(Ⅵ)) was the strongest. The variations of GSH content in HepG2 cells stimulated with arsenite (As(Ⅲ)), arsenate (As(Ⅴ)), chromium chloride (Cr(Ⅲ)), and Cr(Ⅵ) were analyzed by the proposed approach and analysis of intracellular GSH imaging. The results revealed that the stimulation group i. e. analyzed doses (low-dose 2 mg/L, high-dose 5 mg/L) of As(Ⅲ), As(Ⅴ), and Cr(Ⅲ) had no obvious effect on GSH content in HepG2 cells compared with the control group, whereas high-dose Cr(Ⅵ) can significantly reduce GSH content in HepG2 cells. Considering the analysis of cytotoxicity of As(Ⅲ), As(Ⅴ), Cr(Ⅲ), and Cr(Ⅵ), it shows that the content of GSH in HepG2 cells is related to cytotoxicity, and the content of GSH will decrease with the increase in cytotoxicity.

EFFECTS OF CHROMIUM STRESS ON SEED GERMINATION AND EARLY SEEDLING GROWTH PERFORMANCES OF PEARL MILLET PENNISETUM GLAUCUM (L.) R. BR. (POACEAE)

Heavy metals are widely available in the environment due to the natural processes, industrial, anthropogenic activities and ultimately in the results contaminate the immediate environment. The presence of the heavy metals such as Pb, Cd, Cr, Ni, Fe and Cu in environment disturb the quality of ecosystems, soils, water, air and vegetation. The chromium metal at higher level in ecosystem is an alarming signal for both developed and developing countries. Pennisetum glaucum is an annual grass which is widely cultivated in drought, rain fed and high temperature areas. The limited amount of literature available on the impact of chromium stress on P. glaucum. This study was conducted to investigate the beneficial or harmful effect of chromium stress on seed germination and seedling growth performances of P. glaucum in in vitro conditions. The different concentration of chromium 0, 25, 50, 75 and 100 ppm was applied. In present study, the overall results suggests the variable response on the rate of seed germination percentage and plant growth of P. glaucum to chromium stress was recorded. Results showed that the chromium treatment at 25 ppm significantly (p&lt;0.05) reduced root growth of P. glaucum. The chromium at 50 ppm level significantly decreased the rate of percentage of seed germination of P. glaucum. The seedling dry weight of P. glaucum seedling was decreased highly at 75 ppm chromium. Root / shoot ratio also decreased due to gradual increase in chromium from low (25 ppm) to higher (100 ppm) levels. Similarly, the chromium at 25 to 100 ppm gradually decreased the percentage of tolerance and seedling vigor index of P. glaucum. An effective efforts for minimize the chromium toxicity and tolerance in plants are required.

Detoxification and Removal of Hexavalent Chromium in Aquatic Systems: Applications of Bioremediation

Chromium is a transition metal with a wide range of applications in leather tanning, textile, electroplating, stainless steel production, inorganic chemical production and wood preservation industries due to yellow colouration, corrosion resistance, higher melting-point and crystalline structure with raging of oxidation states from 0 to +6. Trivalent and hexavalent chromium are the most abundant forms of chromium discharged into the aquatic environment by industries. It has been reported that hexavalent chromium is highly toxic than trivalent chromium due to the higher solubility, mobility and tendency to accumulate in higher trophic levels, which, therefore, become bioavailable and causes carcinogenic, mutagenic and teratogenic effects on most microorganisms and animals, growth inhibition, morphological and physiological changes and yield reductions in plants. Therefore, it is essential to detoxify the above hazardous pollutants up to permissible limits, which local and international authorities have legislated concerning its threat towards biotic components. Hexavalent chromium detoxification is possible to achieve using three methods i.e. physical, chemical and biological methods. These remediation processes can eliminate highly toxic hexavalent chromium or transform it into a less toxic form of trivalent chromium, completely or partially by adsorption and reduction. Biological remediation is considered a cost-effective and ecofriendly method compared to physical and chemical remediation. Further, many biological agents have been identified as agents that can tolerate the hexavalent chromium toxicity up to certain higher levels depending on the internal and external environmental factors, indicating different metal tolerance mechanisms that are assumed to be applied in metal remediation aspects. According to the testimonies of novel bioremediation studies, some hexavalent chromium tolerant organisms such as plants, bacteria, unicellular and multicellular fungi and algae are promising eco-friendly alternatives in detoxification and hexavalent chromium removal perspective. This article reviews the bioremediation approaches available for hexavalent chromium detoxification and removal and highlights the strengths and weaknesses of current bioremediation methods.

Adsorption Characteristics of Indigenous Chromium-Resistant Aspergillus niger Strain Isolated from Red Soil for Remediation of Toxic Chromium in Red Soil Environments.

The microbial treatment of soil has great potential to reduce chromium pollution. Here, an indigenous chromium-resistant Aspergillus niger strain (A1) was isolated and screened from heavily chromium-contaminated red soil in Yunnan Province, China using a traditional isolation method and a selective culture experiment. The molecular identification of A1 was achieved using 18S rRNA sequencing. The tolerance of the strain to toxic chromium was evaluated through pure laboratory culture. The adsorption effect and mechanism of A1 on chromium in red soil were further studied. The study concluded that A1 exhibited strong activity with exposure to 500 mg·L-1 Cr6+. Chromium adsorption by A. niger occurred mainly through intracellular metabolism, surface complexations with EPS, and chemical reduction with -C=C-, -OXuH, NH2, and -C=0. The optimized results showed that A1 had the best Cr6+ removal effect at pH 4, 40 °C, and a 60 h culture time. Compared with the inoculating of exogenous microbial agents, after inoculating A1 into the chromium-contaminated red soil, Cr6+ content was significantly reduced, and the high-toxicity chromium state (water-soluble and exchange states) decreased, whereas the low-toxicity chromium state (precipitation and residue states) increased. The results of red soil ITS also showed that the inoculation of indigenous microorganisms can better colonize the red soil. This study proves the feasibility of the application of indigenous A. niger to address red soil chromium pollution and provides a new idea and theoretical support for red soil remediation.

Melatonin improves the removal and the reduction of Cr(VI) and alleviates the chromium toxicity by antioxidative machinery in Rhodobacter sphaeroides

Bioremediation with photosynthetic bacteria (PSB) is thought to be a promising removal method for hexavalent chromium [Cr(VI)]-containing wastewater. In the present study, Rhodobacter sphaeroides (R. sphaeroides) SC01 was used for the investigation of Cr(VI) removal in Cr(VI)-contaminated solution in the presence of melatonin. It was found that exogenous melatonin alleviated oxidative damage to R. sphaeroides SC01, increased Cr (VI) absorption capacity of cell membrane, and improved the reduction efficiency of Cr(VI) via the activation of chromate reductants. The results showed that melatonin could further promote the increase in Cr(VI) removal efficiency, reaching up to 97.8%. Furthermore, melatonin application resulted in 296.9%, 44.4%, and 69.7% upregulation of ascorbic acid (AsA), glutathione (GSH), and cysteine (Cys) relative to non-melatioin treated R. sphaeroides SC01 at 48 h. In addition, the resting cells, cell-free supernatants (CFS), and cell-free extracts (CFE) with melatonin had a higher Cr(VI) removal rate of 18.6%, 82.0%, and 15.2% compared with non-melatonin treated R. sphaeroides SC01. Fourier transform infrared spectroscopy (FTIR) revealed that melatonin increased the binding of Cr(III) with PO43− and CO groups on cell membrane of R. sphaeroides SC01. X-ray diffractometer (XRD) analysis demonstrated that melatonin remarkably bioprecipitated the production of CrPO4·6H2O in R. sphaeroides SC01. Hence, these results indicated that melatonin plays the important role in the reduction and uptake of Cr(VI), demonstrating it is a great promising strategy for the management of Cr(VI) contaminated wastewater in photosynthetic bacteria.

Toxic chromium in water and the effects on the human body: a systematic review

Abstract Both in developed and developing countries, there is a growing concern about the dangerous hexavalent chromium, in the consumption of drinking water. Hexavalent chromium is recognized to have a negative impact on the human body, both in the short and long term. The purpose of this study is to evaluate the relationship between hexavalent chromium in water and its impact on human health. A systematic review of the international literature is applied, according to the instructions of PRISMA protocol, in the databases PubMed and Scopus, for the years 2005–2022. The systematic literature review was conducted using inclusion and exclusion criteria, and appropriate keywords for exposure and outcome. A total of 18 studies met all inclusion criteria. Most research concludes that hexavalent chromium is a risk factor for humans, as opposed to trivalent chromium who is a protective factor. A study indicates the consumption of drinking water with high concentrations of hexavalent chromium, as a protective factor for human life, while eight of the total studies suggest hexavalent chromium as a potential risk factor. It is necessary to clarify the origin, the mode of action, and the negative impact has on human health, to create appropriate preventive and intervention measures.

Biosorption of Hexavalent Chromium using Fungal Strains Isolated from Soil

Chromium tolerant fungal strains were isolated from heavy metal contaminated environments and identified using morphological and microscopic observation followed by ribotyping. The microorganisms with the maximum tolerance were analyzed by inoculating each fungus in a PD medium supplemented with hexavalent Chromium salts. The presence of the metal was estimated by the acidic reaction with the 1, 5-diphenylcarbazide method using a spectrophotometer (UV – Vis) at 540 nm. Among all the fungal strains, the most tolerant under maximum enrichment was identified as Paecilomyces lilacinus by a zone of inhibition on the PDA medium. The effect of environmental parameters like pH and temperature on the growth and heavy metal removal also were analyzed. Among the fungal strains, Aspergillus niger, A. terreus, and Paecilomyces lilacinus could tolerate Chromium (VI) toxicity up to 800 mgL-1. All the fungi were able to completely remove the heavy metal Cr (VI) at the concentration of 10mg/L, where the maximum growth was obtained. However, the organisms could remove the Chromium in higher concentrations at a slow rate. The maximum removal was recorded at acidic pH (4.0) under ambient temperature (30oC). The fungal species, Paecilomyces lilacinus exposed to UV- radiation for up to 10 minutes, enhanced its bio-sorption efficiency compared to the normal strain.

Hexavalent chromium-reducing plant growth-promoting rhizobacteria are utilized to bio-fortify trivalent chromium in fenugreek by promoting plant development and decreasing the toxicity of hexavalent chromium in the soil

BackgroundFenugreek is known to have good anti-diabetes properties. Moreover, several studies accounted that the trivalent form of chromium [Cr(III)] also have anti-diabetic properties. However, its hexavalent form i.e., Cr(VI) is known to be highly toxic and carcinogenic to living beings and retarded plant growth even if it is present in low concentration in soil. Many plant growth-promoting rhizobacteria (PGPR) are reported to have the potential to reduce the Cr(VI) into Cr(III) in soil. In view of the above, the present objective was designed to effectively utilize Cr(VI) reducing PGPRs for the growth and development of fenugreek plant in Cr(VI) amended soil, apart from reducing Cr(VI) in soil and fortification of Cr(III) in the aerial part of plants. MethodsThe experiment was carried out to evaluate the effect of Cr(VI)-reducing PGPRs viz. Bacillus cereus (SUCR44); Microbacterium sp. (SUCR140); Bacillus thuringiensis (SUCR186) and B. subtilis (SUCR188) on growth, uptake and translocation of Cr as well as other physiological parameters in fenugreek grown under artificially Cr(VI) amended soil (100 mg kg−1 of Cr(VI) in soil). ResultsThe aforementioned concentration of Cr(VI) in soil cause severe reduction in root length (41 %), plant height (43 %), dry root (38 %) and herb biomass (48 %), when compared with control negative (CN; uninoculated plant not grown in Cr(VI) contaminated soil). However, the presence of Microbacterium sp.˗SURC140 (MB) mitigates the Cr toxicity resulting in improved root length (92 %), plant height (86 %), dry root (74 %) and herb biomass (99 %) as compared with control positive (CP; uninoculated plants grown in Cr(VI) contaminated soil). The maximum reduction in bioavailability (82 %) of Cr(VI) in soil and its uptake (50 %) by the plant were also observed in MB-treated plants. However, All Cr(VI)-reducing PGPRs failed to decrease the translocation of Cr to the aerial parts. Moreover, the plant treated with MB observed diminution in relative water content (13 %), electrolyte leakage (16%) and lipid peroxidation (38 %) as well as higher chlorophyll (37 %) carotenoids (17 %) contents and antioxidants (18%) potential. ConclusionThis study demonstrates that MB can lower the Cr(VI) toxicity to the plant by reducing the bioavailable Cr(VI), consequently reducing the Cr(VI) toxicity level in soil and helping in improving the growth and yield of fenugreek. Additionally, Cr(III) uptakes and translocation may improve the effectiveness of fenugreek in treating diabetes.

Establishment of an in vitro Protocol for Chromium Toxicity Tolerance Screening in Banana

Establishment of an in vitro Protocol for Chromium Toxicity Tolerance Screening in Banana

Hexavalent-Chromium-Induced Oxidative Stress and the Protective Role of Antioxidants against Cellular Toxicity.

Hexavalent chromium is a highly soluble environmental contaminant. It is a widespread anthropogenic chromium species that is 100 times more toxic than trivalent chromium. Leather, chrome plating, coal mining and paint industries are the major sources of hexavalent chromium in water. Hexavalent chromium is widely recognised as a carcinogen and mutagen in humans and other animals. It is also responsible for multiorgan damage, such as kidney damage, liver failure, heart failure, skin disease and lung dysfunction. The fate of the toxicity of hexavalent chromium depends on its oxidation state. The reduction of Cr (VI) to Cr (III) is responsible for the generation of reactive oxygen species (ROS) and chromium intermediate species, such as Cr (V) and Cr (IV). Reactive oxygen species (ROS) are responsible for oxidative tissue damage and the disruption of cell organelles, such as mitochondria, DNA, RNA and protein molecules. Cr (VI)-induced oxidative stress can be neutralised by the antioxidant system in human and animal cells. In this review, the authors summarise the Cr (VI) source, toxicity and antioxidant defence mechanism against Cr (VI)-induced reactive oxygen species (ROS).

Mitigation of Negative Effects of Chromium (VI) Toxicity in Faba Bean (Vicia faba) Plants through the Supplementation of Kinetin (KN) and Gibberellic Acid (GA3)

The present study was carried out to explore the possible role of kinetin and gibberellic acid (GA3) on faba bean under chromium (Cr) stress. Cr treatment negatively affected growth and biomass production, reduced photosynthetic pigments, and inhibited photosynthesis, gas exchange parameters, antioxidant enzymes, and the glyoxylase cycle. Moreover, Cr stress enhanced the production of malondialdehyde (MDA, 216.11%) and hydrogen peroxide (H2O2, 230.16%), electrolyte leakage (EL, 293.30%), and the accumulation of proline and glycine betaine. Exogenous application of kinetin and GA3 increased growth and biomass, improved pigment contents and photosynthesis, as well as up-regulated the antioxidant system by improving the antioxidant enzyme activities and the content of nonenzymatic components, and the glyoxylase cycle. Additionally, kinetin and GA3 application displayed a considerable enhancement in proline (602.61%) and glycine betaine (423.72), which help the plants to maintain water balance under stress. Furthermore, a decline in Cr uptake was also observed due to kinetin and GA3 application. Exogenous application of kinetin and GA3 ameliorated the toxic effects of Cr in faba bean plants, up-shooting the tolerance mechanisms, including osmolyte metabolism and the antioxidant system.

Selenium and molybdenum synergistically alleviate chromium toxicity by modulating Cr uptake and subcellular distribution in Nicotiana tabacum L.

Chromium (Cr) is a harmful heavy metal that poses a serious threat to plants and animals. Selenium (Se) and molybdenum (Mo) are two beneficial elements for plant growth and resistance. However, their interactive effects on Cr uptake and distribution are poorly understood. Therefore, a hydroponics experiment was conducted to explore the effects of the use of Se and Mo alone and simultaneously on mitigating Cr toxicity. In this study, Nicotiana tabacum L. seedlings were exposed to control, 50 µM Cr, 50 μM Cr + 2 μM Se, 50 μM Cr + 1 μM Mo, or 50 μM Cr + 2 μM Se + 1 μM Mo in Hoagland solution. After 2 weeks, the plant biomass, Cr, Se and Mo contents, photosynthesis, leaf ultrastructure, antioxidant system, subcellular distribution and associated gene expression in Nicotiana tabacum L. were determined. The results showed that simultaneous use of Se and Mo promoted tobacco growth under Cr stress, as evidenced by reducing reactive oxygen species (ROS) content and reducing Cr translocation factor (TF) and inducing a 51.3% reduction in Cr content in shoots. Additionally, Se-Mo interactions increased the levels of glutathione (GSH) and phytochelatin (PC) and the distribution of Cr in the cell walls and organelles. Furthermore, the relative expression of PCS1 was upregulated, while those of NtST1 and MSN1 were downregulated. The results concluded that the simultaneous use of Se and Mo effectively alleviated Cr toxicity in Nicotiana tabacum L., which not only offers an efficient way for crops to resist Cr toxicity but also provides evidence for the benefit of Se combined with Mo.

Inoculation of plant-growth-promoting rhizobacteria and earthworms in the rhizosphere reinstates photosynthetic attributes and secondary metabolites in Brassica juncea L. under chromium toxicity

Inoculation of plant-growth-promoting rhizobacteria and earthworms in the rhizosphere reinstates photosynthetic attributes and secondary metabolites in Brassica juncea L. under chromium toxicity

Sorption Behavior, Speciation, and Toxicity of Microplastic-Bound Chromium in Multisolute Systems

Sorption Behavior, Speciation, and Toxicity of Microplastic-Bound Chromium in Multisolute Systems

Biochemical properties and heavy metal analysis of a commercial fish Opisthopterus tardoore

Aim: The study was designed to evaluate various biochemical parameters, protein expression, antioxidant enzymes and heavy metals by testing an edible fish Opisthopterus tardoore. Methodology: The experimental fish were collected from five major fish markets of Bhubaneswar, India and distribution of carbohydrate, lipid and protein content were assessed in muscle tissues. To enhance the understanding of molecular mechanism, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of crude proteins was conducted. Catalase (CAT) and guaiacol peroxidase (GPX) activities were determined both spectrophotometrically and by native gel electrophoresis. For heavy metal analysis, three toxic elements viz.,chromium, cadmium and lead were examined by atomic absorption spectrophotometer. Results: The muscle tissues showed variation in the concentrations of carbohydrate (0.17 ± 0.02 to 0.28 ± 0.04 % f.wt.), lipid (3.48 ± 0.27 to 6.62 ± 0.44 % d. wt.) and protein (1.56 ± 0.11 to 2.92 ± 0.16 % f. wt.) with respect to the markets from where fish samples were collected. The protein profiling study revealed the disappearance as well as de novo synthesis of some proteins. The activities of CAT and GPX were determined for establishing a possible bioindicator of metal toxicity in fish. A rapid disturbance in their enzymatic actions was noticed which was also confirmed through native polyacrylamide gel electrophoresis with respect to fish samples. The heavy metals analysis manifested a varying level of accumulation of Cr whereas Pb and Cd were found below the detection limits. Interpretation: The biochemical disturbances and accumulation of Cr in muscle tissues of O. tardoore reflect the pollution status of nearby coastal areas of the Bay of Bengal, Odisha. Key words: Biochemical analysis, Chromium toxicity, Guaiacol peroxidase, Opisthopterus tardoore, Protein expression

Rare earth element scandium mitigates the chromium toxicity in Lemna minor by regulating photosynthetic performance, hormonal balance and antioxidant machinery

Chromium (Cr) toxicity is a serious problem that threatens the health of living organisms and especially agricultural production. The presence of excess Cr leads to biomass loss by causing the imbalance of biochemical metabolism and inhibiting photosynthetic activity. A new critical approach to cope with Cr toxicity is the use of the rare earth elements (REEs) as an antioxidant defence system enhancer in plants. However, the effect of scandium (Sc), which is one of the REEs, is not clear enough in Lemna minor exposed to Cr toxicity. For this purpose, the photosynthetic and biochemical effects of scandium (50 μM and 200 μM Sc) treatments were investigated in Lemna minor under Cr stress (100 μM, 200 μM and 500 μM Cr). Parameters related to photosynthesis (Fv/Fm, Fv/Fo) were suppressed under Cr stress. Stress altered antioxidant enzymes activities and hormone contents. Sc applications against stress increased the activities of superoxide dismutase (SOD), NADPH oxidase (NOX), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and glutathione S-transferase (GST). In addition to the antioxidant system, the contents of indole-3-acetic acid (IAA), abscisic acid (ABA) and jasmonic acid (JA) were also rearranged. However, in all treatment groups, with the provision of ascorbate (AsA) regeneration and effective hormone signaling, reactive oxygen species (ROS) retention which result in high hydrogen peroxide (H2O2) content and lipid peroxidation (TBARS) were effectively removed. Sc promoted the maintenance of cellular redox state by regulating antioxidant pathways included in the AsA-GSH cycle. Our results showed that Sc has great potential to confer tolerance to duckweed by reducing Cr induced oxidative damage, protecting the biochemical reactions of photosynthesis, and improving hormone signaling.

Quercetin ameliorates chromium toxicity through improvement in photosynthetic activity, antioxidative defense system; and suppressed oxidative stress in Trigonella corniculata L.

Environmental stresses, including heavy metals accumulation, have posed an immense threat to the agricultural ecosystem, leading to a reduction in the yield of crucial crops. In this study, we evaluated the role of quercetin (Qu) in the alleviation of chromium (Cr) stress in Fenugreek (Trigonella corniculata L.). Different levels of Qu were prepared during the experiment, i.e., 15, 25, and 40 μM. For Cr toxification in potted soil, potassium chromate (K2Cr2O7) was used. Cr toxification reduced growth of T. corniculata seedlings. Cr stress also reduced fiber, ash, moisture, carbohydrate, protein, fats, and flavonoid contents. However, seed priming with Qu improved growth and physiochemical characteristics of T. corniculata seedlings grown in normal and Cr-contaminated soil. Seed priming with Qu escalated intercellular CO2 concentration, stomatal conductance, transpiration rate, and photosynthetic rate in T. corniculata seedlings. Application of Qu also increased the activity of antioxidative enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) in T. corniculata seedlings exposed to normal and Cr-contaminated soil. Application of Qu incremented the activity of SOD, POD, CAT, and APX, which were increased by 28, 22, 29, and 33%, respectively, in T. corniculata grown in Cr-toxic soil as compared to control treatment. Chromium stress alleviation was credited to the enhanced activity of the antioxidative defensive system in T. corniculata seedlings. It is proposed that Qu supplementation can be used to mitigate other abiotic stresses in plants.