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Arsenic (As), the toxic metalloid, is taken up by plant roots and transported to different parts of the plant through transporters of the essential elements due to the structural analogy. The analogy of arsenate (AsV) with phosphate enables As (V) to enter plant through phosphate transporter, while, arsenite (AsIII) which is analogous to silicic acid, is taken up by plants through aquaporins. After the uptake, the different forms of As are translocated to shoot via xylem, imposing toxicity to plants that affect their growth and yield, however this depends on the effective concentration of free As anion at particular cellular organelle /site. To this end, the role of transporters becomes crucial as the central and prime regulator of As movement throughout the plant and in various cellular compartments. It is essential to understand the precise roles of different transporters involved in As uptake and transportation to avoid As accumulation and stress in plant. Therefore, this review discusses the transporters namely, phosphate transporters, nodulin 26-like intrinsic proteins, plasma membrane intrinsic proteins, tonoplast intrinsic proteins, C-type ATP binding cassette transporters, arsenical resistance 3 transporter, inositol transporters, multidrug and toxic compound extrusion transporters, and natural resistance-associated macrophage protein transporters, which are involved in As uptake, sequestration, translocation and efflux in plants, with an emphasis on As stress tolerance through the regulation of expression of the different transporters.

Widespread distribution, toxicity and exposure through rice and rice-based food products make arsenic (As) contamination of environment a serious issue. This review discusses various strategies that can be utilised to tackle the As problem in rice, and the socioeconomic impacts of the As problem. The countries of south and south-east Asia are renowned as hotspots of As contamination owing to occurrence and enrichment of As in soil and groundwater via natural biogeochemical weathering of rocks and As-enriched sediment. The irrigation of rice is mostly applied through the use of contaminated groundwater leading to high As accumulation in rice grains. The intensification of research to address the problem of As in rice has been seen in the past two decades. It has been realised that appropriate irrigation water management, which acts as a major driver of As chemistry in soil and As uptake and transport in plants, can be an easy and affordable solution. Further, balanced supplement of various nutrient elements like selenium (Se), silicon (Si), sulfur (S), nitrogen (N), iron (Fe) and zinc (Zn) has been found to impart dual benefits in terms of reduced As toxicity as well as enhance the nutritional quality of rice grains. Several other agronomic and biotechnological approaches, processing, and cooking methods of rice were found to have profound impacts on rice As and its speciation from farms to table.

The present study assessed the utility of Allium cepa based cyto-genotoxicity bioassays in evaluating the arsenic toxicity and remediation potential of Pteris vittata on contaminated soil of Lakhimpur-Kheri district. Untreated and P. vittata treated soil extracts were used for cyto-genotoxicity tests in A. cepa. Results showed that P. vittata extracted high concentration of arsenic, which ranged from 220 to 1420 mgkg-1 in different soils. Cyto-genotoxic assessment of A. cepa showed that extract of P. vittata treated soil had lower cyto-genotoxic effects as compared to untreated soil. A higher mitotic index (10%) while lower mitotic depression (29%), relative abnormality rate (10%), chromosomal aberrations (1%) and micronuclei (2%) were detected in root meristematic cells of A. cepa exposed to remediated soil extract in comparison to untreated soil. The studies provide a simple, rapid and economic cyto-genotoxicity bioassay tool for evaluating toxicity of contaminated soils of contaminated soils as well as revealed the phytoremdiation property of P. vittata against arsenic toxicity.

Chloroplast-localized adenosine-5'-phosphosulphate reductase (APR) generates sulfite and plays a pivotal role in sulfate reduction to cysteine. The peroxisome-localized sulfite oxidase (SO), oxidizes excess sulfite to sulfate. Wild-type (WT), SO RNA-interference (SO Ri) and SO overexpression (SO OE) Arabidopsis mutants were infiltrated with sulfite. In SO Ri plants, water loss was increased due to enhancement of stomatal aperture compared to WT leaves, whereas in SO OE plants, stomatal aperture was smaller than that of the WT plants, and hence water loss was lower. Sulfite application also limited sulfate and ABA-induced stomatal closure in WT and SO Ri. The increases in APR activity in response to sulfite infiltration into WT and SO Ri leaves resulted in an increase in sulfite beyond the level of the applied sulfite, indicating that APR has an important role in sulfite-induced increases in stomatal aperture. Notably, sulfite-induced H2O2 generation by NADPH oxidase, led to enhanced APR expression and sulfite production. Suppression of APR by inhibiting NADPH oxidase and glutathione reductase2 (GR2) by diphenyleneiodonium, or mutation in APR2 or GR2, resulted in decrease in sulfite production and stomatal aperture size, further supporting the role of APR in stomatal aperture size. The importance of APR and SO in the set-up of sulfite level in leaves, and the significance of sulfite level in water loss were further demonstrated during fast and harsh drought stress in root-detached WT, gr2 and SO modified plants. The role of SO in sulfite homeostasis in relation to water consumption was shown in well-watered plants.

Scientific research has focused to delineate the core aspects of stress tolerance mechanisms and to apply the crucial components for enhancing the tolerance of plants and their growth under stressed environments. Metallothioneins (MTs) are known to play pivotal roles in stress regulation. They are known in bacteria, fungi, and all other eukaryotic organisms. MTs are low molecular weight, cysteinerich proteins. They are important metal chelators and also possess antioxidant properties. MTs work upon reactive oxygen species (ROS), whose production is induced by different stresses and is known to damage various cellular biomolecules. MT proteins are classified into two classes, plant MTs belong to class II type, while animal MTs belong to class I type. MTs have been investigated in the vast number of plant species and their crucial roles in stress modulation has been uncovered. Hence, MTs are a promising tool for stress management, acting as essential stress biomarkers and ensuring food security in the coming future to achieve sustainable development goals worldwide. This review discusses the roles of MTs in plants under different abiotic stresses, including drought, salinity, low temperature, light, in oxidative stress regulation and heavy metals homeostasis and detoxification including toxic nanoparticle management in plants.

Arsenic (As) contamination of the environment is a widespread problem with the situation at its worst in the South Asian region of West Bengal, India, and Bangladesh. In order to cope up with the problem and to be able to engineer plants in near future, there is a need to thoroughly understand the kinetics of As uptake and its impact on responses of plants. In this work, Brassica juncea (L.) Czern was used as a model system to understand kinetic interaction between As uptake and transport to the shoot and corresponding biochemical responses. The seedlings of B. juncea were exposed to 100 μM arsenite [As(III)] in hydroponics for different time points of 1, 4, and 24 hours. The As concentration was found to show a gradual increase in different tissues with time and the level of As followed the order: lower root greator than upper root greator than shoot greator than top leaves at all the times points. However, the level of hydrogen peroxide (H2O2) and the activities of NADPH oxidase, superoxide dismutase (SOD) and ascorbate oxidase (AO) were increased even at 1 h in lower shoot and leaves. The expression of transporters genes, NIP1;1, NIP2;1, NIP5;1 and NIP6;1 was found significantly up-regulated at 24 hours. This work establishes a kinetic relationship between As accumulation and ensuing biochemical responses in B. juncea.

Sesuvium portulacastrum (L.) is a halophytic phytoremediator plant with potential for significant accumulation of metals and metalloids. The present work evaluatedthe physiological and biochemical responses of Sesuvium plants to copper (Cu) exposure (100–500 μM) for 30 d in field conditions. Plants demonstrated significant copper accumulation that increased with the increase in Cu concentration of the medium (maximum 254 µg g−1 DW at 500 µM). The root dry weight was not significantly affected at 500 μM while shoot dry weight decreased significantly. Total soluble proteins, photosynthetic pigmentsand malondialdehye (MDA) were declined significantly beyond 100 μM after 30 d. Among metabolites and enzymes of thiol metabolism, total non-protein thiols (NP-SH), γ-glutamylcysteine synthetase and glutathione reductase did not show significant effect while cysteine, serine acetyltransferase, and cysteine synthaseshowed a significant decline beyond 100 μM. The level of proline, glycine betaine and total phenolics also showed decreasing trend with the increase in Cu concentration. In conclusion, plantsare potential phytoextractor of Cu but do suffer from the toxic effects of Cu at high concentration of 500 μM. Sesuvium plants therefore appear suitable for use in phytoremediation purpose at low Cu concentrations (100 – 250 μM).

The optimum growth and development of plants depend on some basic components obtained from nature. These include water, carbon dioxide, light, and mineral elements. In addition to these essential elements, certain elements known as beneficial elements support the growth of plants. Finally, some elements are required in trace and ultratrace quantities. These elements include selenium, silicon, manganese boron, cobalt, molybdenum, nickel, aluminum, copper, iodine, iron, and zinc. Selenium is a component of several important enzymes like glutathione peroxidases, thioredoxin reductase, and iodothyronine deiondinase. Silica is required by plants of the Poaceae family to gain strength, and it is essential for lodging resistance in rice plants. Nickel is also a constituent of enzymes such as urease, glyoxalase I, superoxide dismutase, [NiFe]-hydrogenase, carbon monoxide dehydrogenase, and acetyl-coenzyme A. Molybdenum is also an important component of enzyme nitrate reductase. Nickel helps the plant to metabolize urea nitrogen into a bioavailable form, that is ammonia, which leads to improved plant growth. The elements like zinc and copper are essentially required by plants in small amounts. The essential elements play important roles in various processes, such as growth hormone production, internode elongation, and various enzymatic activities. The research on beneficial elements has proven their roles in plant growth and development. In addition, an optimum supply of such beneficial and ultratrace elements helps them tackle abiotic and biotic stresses. For example, silica and selenium supplementation have been found to impart arsenic stress tolerance to rice plants. The studies point to the fact that even if the essentiality of some elements is not proved, they do perform crucial roles in plants. This chapter discusses the importance of essential, beneficial, and ultratrace elements in plant growth, development, and stress tolerance.

The adverse effects of arsenic (As) contamination are well known. Rice is a staple food for 50% of the world population but the accumulation of As into rice hampers the food security and safety. Thus the amelioration of As stress and reduction of As levels in rice are needed. In this study, transcriptome (Illumina sequencing) and proteome (2D gel electrophoresis) explored mechanisms of consortium (P. putida+C. vulgaris) mediated growth promotion and As amelioration in rice. The rice seedlings grown hydroponically in the Hewitt nutrient medium and after acclimatization, exposed to 50 µM As alone as well as with microbial consortium to observe the impact at morphological and molecular level. The inoculation of microbial consortium significantly ameliorated the As toxicity, improved growth of root hairs and maintained cellular integrity of the epidermis, exodermis and the stele region during As exposure. Several genes showed differential expression in As and As+P. putida. Down-regulation of As transporters (OsPIP2;2 and OsPIP2;3, OsTIP2;1) and higher expression of WRKY gene (WRKY28) during As+P. putida+C.vulgaris suggested reduction of As uptake in rice. The up-regulation of nutrient elements transporters (OsZIFL9, OsZIFL5, OsZIFL12 and OsZIP2, OsYSL15 and OsCOPT6) in the presence of consortium indicated the improved nutrient status of rice. Higher expression of regulatory elements like auxin/indole 3 acetic acid (AUX/IAA), WRKY and myeloblastosis (MYB) TFs and down-regulation of defense responsive genes such Glutathione-S-transferase, Peroxidase and Glutaredoxinduring As+P. putida+C.vulgaris exposure was also observed. Proteome profiling demonstrated differential abundance of proteins involved in photosynthesis (chlorophyll a/b binding protein, photosystem I Fe-S centre), energy metabolism (ATP synthase subunit beta) transport, signaling (tubulin 1, actin 1), defense (glutathione S-transferase, phenylalanine ammonia lyase) and amino acid metabolism (cysteine synthase, glutamine synthetase), which supported the As ameliorative and growth-promoting potential of microbial consortium during As stress in rice plants. The study gives comprehensive information about gene and protein changes in rice plants in As+consortium exposure.

The Arabidopsis thaliana aldehyde oxidase 3 (AAO3) catalyzes the oxidation of abscisic aldehyde (ABal) to abscisic acid (ABA). Besides ABal, plants generate other aldehydes that can be toxic above a certain threshold. AAO3 knockout mutants (aao3) exhibited earlier senescence but equivalent relative water content compared with wild-type (WT) during normal growth or upon application of UV-C irradiation. Aldehyde profiling in leaves of 24-day-old plants revealed higher accumulation of acrolein, crotonaldehyde, 3Z-hexenal, hexanal and acetaldehyde in aao3 mutants compared with WT leaves. Similarly, higher levels of acrolein, benzaldehyde, crotonaldehyde, propionaldehyde, trans-2-hexenal and acetaldehyde were accumulated in aao3 mutants upon UV-C irradiation. Aldehydes application to plants hastened profuse senescence symptoms and higher accumulation of aldehydes, such as acrolein, benzaldehyde and 4-hydroxy-2-nonenal, in aao3 mutant leaves as compared with WT. The senescence symptoms included greater decrease in chlorophyll content and increase in transcript expression of the early senescence marker genes, Senescence-Related-Gene1, Stay-Green-Protein2 as well as NAC-LIKE, ACTIVATED-BY AP3/P1. Notably, although aao3 had lower ABA content than WT, members of the ABA-responding genes SnRKs were expressed at similar levels in aao3 and WT. Moreover, the other ABA-deficient mutants [aba2 and 9-cis-poxycarotenoid dioxygenase3-2 (nced3-2), that has functional AAO3] exhibited similar aldehydes accumulation and chlorophyll content like WT under normal growth conditions or UV-C irradiation. These results indicate that the absence of AAO3 oxidation activity and not the lower ABA and its associated function is responsible for the earlier senescence symptoms in aao3 mutant.

Arsenic contamination of the environment is a serious problem threatening the health of millions of people exposed to arsenic (As) via drinking water and crops grown in contaminated areas. The remediation of As-contaminated soil and water bodies needs to be sustainable, low-cost and feasible to apply in the most affected low-to-middle income countries, like India and Bangladesh. Phytoremediation is an aesthetically appreciable and successful approach that can be used for As decontamination with use of the best approach(es) and the most promising plant(s). However, phytoremediation lacks the required speed and sometimes the stress caused by As could diminish plants’ potential for remediation. To tackle these demerits, we need augment plants’ potential with appropriate technological methods including microbial and nanoparticles applications and genetic modification of plants to alleviate the As stress and enhance As accumulation in phytoremediator plants. The present review discusses the As phytoremediation prospects of soil and water bodies and the usefulness of various plant systems in terms of high biomass, high As accumulation, bioenergy potential, and economic utility. The potential and prospects of assisted phytoremediation approaches are also presented.

The study implements a periodical intermittent water cycle during rice cultivation providing insight potential in minimizing soil bio-available arsenic. Soil As concentrations were 34 ± 0.49 and 72.03 ± 0.54 mg kg-1 As respectively in two selected fields with rice cultivars gosai and satabdi, in comparison to 42.26 ± 0.37 and 83.69 ± 0.48 mg kg-1 in continuously flooded field soil, determined through ICP-MS. The study found higher translocation of silicon from soil to rice plant parts under intermittent irrigation having pH range of 7.6–9.4 and greater availability of soil organic content that in turn release more labile silicon from soil to aqueous phase for plant accumulation. This increased uptake of silicon strengthens rice shoots, nodes and leaf xylem-phloem integrity compared to conventional continuously flooded rice cultivation approach, suppressing the arsenic translocation, as observed under FE-SEM real-time imaging. Fresh plants were analysed for bioaccumulation and translocation factors of arsenic and silicon to justify the enhanced silicon uptake under proposed practice. Plant stress regulator enzymes viz. malondialdehyde (MDA), total protein, superoxide dismutase (SOD), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) from both conditions and found to be better in intermittent method over conventional practice with higher productivity.

The accumulation of arsenic (As), a toxic carcinogenic element, in rice plants is a matter of significant environmental and human health concern. This study was performed to analyze the impact of As on ionome profile of rice (Oryza sativa L.) plants. The rice seedlings were subjected either to fixed concentration of 20 μM arsenite [As(III)] for different durations (1, 3, 7, 15 and 30 d) or to different concentrations of As(III) (0, 3, 5, 10, 20, and 50 μM) for fixed duration of 15 d. In both concentration- and duration-dependent experiments, As concentration in leaves and roots was found to increase progressively. The maximum As level was observed at 50 μM in concentration dependent experiment (185 μg g-1 dw in leaves and 9027 μg g-1 dw in roots) and at 30 d in duration dependent experiment (78 μg g-1 dw in leaves and 6175 μg g-1 dw in roots). In concentration dependent experiment, Ni showed a progressive increase while Cu (at all concentrations) and Mn (beyond 5 μM) a decline in both leaves and roots. Zn and Co showed an increase in leaves while a decline in roots. A similar trend of different element concentration was recorded in duration dependent experiment. The present analyses thus highlight that As exposure has profound influence on elemental composition of rice seedlings. Therefore, the health and safety aspects of As impacted rice plants must also be assessed from the perspective of other elemental concentrations.

The present study measured arsenic (As) concentrations in soil, groundwater and rice grain samples in two villages, Sarapur and Chinili, under Chakdaha block, Nadia district, West Bengal, India. This study also included a survey of the two villages to understand the knowledge among villagers about the As problem. Soil and groundwater samples were collected from fields in two villages while rice grain samples were collected from villagers’ houses. The results revealed the presence of As in higher concentrations than the maximum permissible limit of As in drinking water (10 µg L−1 and 50 µg L−1 by WHO and Indian standard, respectively) in groundwater [124.50 ± 1.11 µg L−1 (Sarapur) and 138.20 ± 1.34 µg L−1 (Chinili)]. The level of As in soil was found to range from 47.7 ± 0.14 to 49.3 ± 0.19 mg Kg−1 in Sarapur and from 57.5 ± 0.25 to 62.5 ± 0.44 mg Kg−1 in Chinili which are also higher than European Union maximum acceptable limit in agricultural soil (i.e. 20 mg Kg−1). The analysis of As in rice grains of five varieties, collected from residents of two villages, showed the presence of higher than recommended safe level of As in rice by FAO/WHO (0.2 mg Kg−1). The As concentration order was Gosai (0.95 ± 0.044 mg kg−1), Satabdi (0.79 ± 0.038 mg kg−1), Banskathi (0.60 ± 0.026 mg kg−1), Kunti (0.47 ± 0.018 mg kg−1) and Ranjit (0.29 ± 0.021 mg kg−1). Importantly, Gosai and Satabdi were the most popular varieties being consumed by local people. The data of consumption of rice per day in the survey was used for the measurement of average daily dose and hazard quotient. It was seen that the As hazard was negatively correlated to the age of residents. Therefore, children and toddlers were at higher risk of As exposure than elderly people. In addition, people with skin related As toxicity symptoms were also cited in the two villages. The study emphasized the severity of As problem in remote areas of West Bengal, India where people consume As tainted rice due to lack of awareness about the As problem and associated health issues.

Selenium (Se) is an essential element for many animals including humans, prokaryotes and a few green algae. For plants, Se essentiality is yet to be demonstrated. Nevertheless, it is well r...

Aims The aims of the study were to (i) isolate and characterize arsenic-tolerant bacterial strains, (ii) study the plant growth-promoting traits and (iii) explore their bioremediation potential. Methods and results Indigenous arsenic hypertolerant bacterial isolates NM02 and NM03 were screened as they were capable of growing at 150 mmol l-1 As (V) and 70 mmol l-1 As (III). They were identified on the basis of morphological, physiological and biochemical parameter and 16sDNA sequence as Bacillus flexus and Acinetobacter junii respectively. Genomic DNA analysis for the investigation of ars operon revealed the presence of metalloregulatory arsC gene, suggesting their ability to detoxify arsenic. The analysis for siderophore, phosphate solubilization, indole acetic acid (IAA) and ACC deaminase highlighted the intrinsic plant growth-promoting rhizobacteria traits of both the bacterial strains. The energy dispersive spectroscopy analysis proved the potential of cellular arsenic sequestration within the strains. Moreover, Fourier-transform infrared spectra revealed the repositioning of the spectral bands in As presence, indicating the presence of those functional groups on the bacterial surface that is involved in As adsorption. Conclusions Our results indicate that bacterial strains NM02 and NM03 were identified as potent applicants for arsenic bioremediation and possess the ability to facilitate plant growth. Significance and impact of the study The bacterial strains are proficient in As detoxification and can be employed for arsenic bioremediation; a cost-effective and in situ remediation technique for the polluted soil.

Arsenic contamination of environment is a serious issue that has grown in proportion over the years. Arsenic becomes enriched in groundwater due to several redox and biological processes that has been exacerbated due to human intervention. In India, arsenic contamination is widespread and has been reported from West Bengal, Uttar Pradesh, Bihar, Assam, and other states. Arsenic is a highly toxic element and can cause several ailments in humans including cancers. Hence, there is a need to provide safe water to people for drinking purposes and for other daily uses. In this regard, several physicochemical and biological methods are available, which need to be implemented for the purpose. A few of the important low cost and easy methods include precipitation, adsorption, and membrane processes-based filters. Apart from this, biological (bioremediation and phytoremediation) methods have been proposed. The present book chapter gives an overview of arsenic problem and its mitigation strategies.

Arsenic (As) is a toxic metalloid present at high levels in groundwater and soil in several parts of world. Arsenic not only affects crop yield and quality in contaminated areas but also threatens the health of millions of people throughout the world through food production and consumption. Arsenic is well known to induce cancer in humans, and extensive studies have led to suggestion of a number of possible mechanisms including induction of oxidative stress and genotoxic and epigenetic modifications. In the past few decades, it has been understood that the microbiome profile of gut affects the overall health of a human being. It has become clear that food, through its basic effects on microbiome properties, influences the human health. The research on arsenic-gut microbiome is a recent avenue with a lot of research in the last decade on several aspects such as diet, sex, locality, and age-related effects on arsenic-induced microbiome perturbation. This review presents an account of arsenic contamination and arsenic soil microbial interactions and also discusses arsenic toxicity to humans with a major focus on arsenic microbiome research.

Arsenic (As) is a ubiquitous environmental carcinogen that enters the human food chain mainly through rice grains. In the present study, we evaluated the potential of thiourea (TU; non-physiological reactive oxygen species scavenger) in mitigating the negative effects of arsenic (As) stress in indica rice variety IR64, with the overall aim to reduce grain As accumulation. At seedling stage, As + TU treatment induced the formation of more numerous and longer crown roots compared with As alone. The As accumulation in main root, crown root, lower leaf and upper leaf was significantly reduced to 0.1-, 0.14-, 0.16-, 0.14-fold, respectively in As + TU treated seedlings compared with those of As alone. This reduced As accumulation was also coincided with light-dependent suppression in the expression levels of aquaporins and photosynthesis-related genes in As + TU treated roots. In addition, the foliar-supplemented TU under As-stress maintained reducing redox conditions which decreased the rate of As accumulation in flag leaves and, eventually grain As by 0.53-fold compared with those of As treatment. The agronomic feasibility of TU was validated under naturally As contaminated sites of Nadia (West Bengal, India). The tiller numbers and crop productivity (kg seed/ha) of TU-sprayed plants were increased by 1.5- and 1.18-fold, respectively; while, grain As accumulation was reduced by 0.36-fold compared with those of water-sprayed control. Thus, this study established TU application as a sustainable solution for cultivating rice in As-contaminated field conditions.

The role of the cytosolic O-acetylserine-(thiol) lyase A (OASTLA), chloroplastic OASTLB and mitochondrion OASTLC in plant resistance/sensitivity to selenate was studied in Arabidopsis plants. Impairment in OASTLA and B resulted in reduced biomass, chlorophyll and soluble protein levels compared with impaired OASTL C and Wild-Type treated with selenate. The lower organic-Se and protein-Se levels followed by decreased organic-S, S in proteins and total glutathione in oastlA and oastlB compared to Wild-Type and oastlC are indicative that Se accumulation is not the main cause for the stress symptoms, but rather the interference of Se with the S-reduction pathway. The increase in sulfite oxidase, adenosine 5′-phosphosulfate reductase, sulfite reductase and OASTL activity levels, followed by enhanced sulfite and sulfide, indicate a futile anabolic S-starvation response to selenate-induced organic-S catabolism in oastlA and oastlB compared to Wild-Type and oastlC.Additionally, the catabolic pathway of L-cysteine degradation was enhanced by selenate, and similar to L-cysteine producing activity, oastlA and B exhibited a significant decrease in L-cysteine desulfhydrase (DES) activity, compared with WT, indicating a major role of OASTLs in L-cysteine degradation. This notion was further evidenced by sulfide dependent DES in-gel activity, immunoblotting, immunoprecipitation with specific antibodies and identification of unique peptides in activity bands generated by OASTLA, B and C. Similar responses of the OASTLs in Seleno-Cysteine degradation was demonstrated in selenate stressed plants. Notably, no L-cysteine and L-Seleno-Cysteine DES activity bands but those related to OASTLs were evident. These results indicate the significance of OASTLs in degrading L-cysteine and L-SelenoCysteine in Arabidopsis.SummaryThe cytosolic OASTLA and chloroplastic OASTLB have significantly higher desulfhydrase activity rates than the cytosolic DES1 and are able to degrade L-Cys and L-SeCys to sulfide and selenide, respectively in Arabidopsis.

The present study delineates the interactions of arsenic (As), a carcinogenic metalloid, and thiourea (TU), a non-physiological reactive oxygen species (ROS) scavenger, in rice plants grown in As contaminated fields in West Bengal, India. The study was performed for four consecutive seasons (two boro and two aman) in 2016 and 2017 with two local rice cultivars; Gosai and Satabdi (IET-4786) in a control and two As contaminated experimental fields. Thiourea (0.05% wt/vol) treatment was given in the form of seed priming and foliar spray. Thiourea significantly improved growth and yield of rice plants and reduced As concentration in root, shoot, husk and grains in both cultivars and fields. The reduction in As concentration ranged from 10.3% to 27.5% in four seasons in different fields. The average (four seasons) increase in yield was recorded about ~8.1% and ~11.5% in control, ~20.2% and ~18.6% in experimental field 1, and ~16.2% and ~24.1% in experimental field 2, for gosai and satabdi, respectively. Mean hazard quotient (HQ) and incremental lifetime cancer risk (ILCR) values of As reduced upon TU supplementation for both cultivars as compared to that of non-TU plants. Hence, TU can be effectively used to cultivate rice safely in As contaminated fields.

Arsenic (As) contamination is now prevalent in large areas of a number of countries. Arsenic stress during vegetative and reproductive phases of plant growth affects the growth, flowering, and fruit/grain development due to a number of physiological, biochemical, and molecular effects. The metabolism of carbon, nitrogen, and sulfur is affected along with changes in photosynthetic and respiratory processes. The avoidance of As toxicity requires fine-tuning of several processes starting from uptake and transport of As to As detoxification and prevention of stress manifestation. Thus, the regulatory processes promoting concerted action of several pathways become an important determinant of As stress tolerance of a plant. These include various phytohormones (auxins, jasmonates, ethylene, abscisic acid, salicylic acid, etc.), transcription factors, microRNAs, reactive oxygen and reactive nitrogen species, and kinases. It is also important to note that an early perception of arsenic entry into plants and signaling of the information to distant parts (leaves) ensure that plants remain prepared to tackle the As stress. Although the research on signaling aspects of arsenic stress is yet in the primary stage, the information available is of potential application and future research. The present work describes current knowledge on perception and signaling of As stress in plants.

Metals are ubiquitously present in the environment and are crucial for life on earth. This is because several metals perform life saving biological functions. However, there are other metals, which are non-essential. The entry of toxic metals into plants causes physiological and biochemical disturbances and also affects molecular responses. The growth and development of plants are affected that ultimately reduces the yield and quality of plant produce. Another aspect of this issue is that through plant produce, metals gain entry into humans and cause several ailments including cancer. Hence, the concentration of toxic metals in plants and plant based food products needs to be regulated effectively. The present chapter gives an overview of metal toxicity to plants and the status of metal accumulation in various crop plants, fruits, vegetables, etc.

Micronutrient deficiencies have assumed prominence as ‘hidden hunger’; especially iron (Fe) and zinc (Zn) have received considerable attention. Deficiencies of iron and zinc in humans lead to a variety of health-related issues related to growth, metabolic, immune and disease and general fitness. Improving the nutritional quality of staple crops seems to be an effective and straightforward solution to the problem. Despite conventional breeding methods employed for this purpose, success has been limited to the existing diversity in the gene pool. Various other strategies have been used to combat these deficiencies including supplementation, food fortification and modification of food preparation and processing methods. Biofortification aims at either increasing accumulation of these minerals in edible parts, endosperm, or to increase their bioavailability. Another strategy is to use biotechnological tools to improve trace element nutrition in staple foods such as cereals and legumes. This may be achieved by the introduction of genes that code for trace element-binding proteins, overexpression of storage proteins already present and/or increased expression of proteins that are responsible for trace element uptake into plants. Alternative approach is also to use genetically modification to reduce, inhibitors of trace element absorption such as phytate. The present chapter outlines the progress made in the application of biotechnological approaches to enhance crop quality for Fe and Zn nutrition.

The increasing industrialization and urbanization are also triggering environmental pollution, mostly unnoticed, in the case of soil pollution due to uncontrolled contamination by toxic elemental dispersion. The present study focused on this aspect and studied the clean-up of urban soil in a low-cost and eco-friendly way to restrict arsenic (As), lead (Pb) and mercury (Hg) contamination. Four potential ornamental plants, Catharanthus roseus (vinca), Cosmos bipinnatus (cosmos), Gomphrena globose (globosa) and Impatiens balsamina (balsamina) were used along with zero valent iron (ZVI) nanoparticles (Fe NPs) for remediation of the soil spiked with As (70 mg kg−1), Pb (600 mg kg−1) and Hg (15 mg kg−1) in a 60 d pot experiment. All plants were divided into four groups viz. control, spiked, spiked+20 mg kg−1 ZVI NP and spiked+50 mg kg−1 ZVI NP. FTIR and SEM were used for ZVI NP characterization. Soil and plant analyses and elemental assessments were done using ICP-MS, XRF and SEM. Among the four plants, cosmos showed the maximum accumulation of toxic elements (41.24 ± 0.022 mg kg−1 As, 139.15 ± 11.2 mg kg−1 Pb and 15.57 ± 0.27 mg kg−1 Hg) at 60 d. The application of ZVI NP at 20 mg kg−1 dosage was found to further augment plants’ potential for metal(loid)s accumulation without negatively hampering their growth. Cosmos were observed to reduce soil As from 81.35 ± 1.34 mg kg−1 to 28.16 ± 1.38 mg kg−1 (65.38%), Pb from 1132.47 ± 4.66 to 516.09 ± 3.15 mg kg−1 (54.42%) and Hg from 17.35 ± 0.88 to 6.65 ± 0.4 mg kg−1 (61.67%) at 60 d in spiked + 20 mg kg−1 ZVI NP treatment. Balsamina was the most sensitive plant and showed the least metal(loid)s accumulation. In conclusion, three of these plants are potent enough to use together for a better and enhanced removal of toxic elements from the contaminated soil with cosmos to be the best amongst these in urban areas.

The nitrogen (N)-rich ureides allantoin and allantoate, which are products of purine catabolism, play a role in N delivery in Leguminosae. Here, we examined their role as an N source in nonlegume plants using Arabidopsis (Arabidopsis thaliana) plants mutated in XANTHINE DEHYDROGENASE1 (AtXDH1), a catalytic bottleneck in purine catabolism. Older leaves of the Atxdh1 mutant exhibited early senescence, lower soluble protein, and lower organic N levels as compared with wild-type older leaves when grown with 1 mm nitrate but were comparable to the wild type under 5 mm nitrate. Similar nitrate-dependent senescence phenotypes were evident in the older leaves of allantoinase (Ataln) and allantoate amidohydrolase (Ataah) mutants, which also are impaired in purine catabolism. Under low-nitrate conditions, xanthine accumulated in older leaves of Atxdh1, whereas allantoin accumulated in both older and younger leaves of Ataln but not in wild-type leaves, indicating the remobilization of xanthine-degraded products from older to younger leaves. Supporting this notion, ureide transporter expression was enhanced in older leaves of the wild type in low-nitrate as compared with high-nitrate conditions. Elevated transcripts and proteins of AtXDH and AtAAH were detected in low-nitrate-grown wild-type plants, indicating regulation at protein and transcript levels. The higher nitrate reductase activity in Atxdh1 leaves compared with wild-type leaves indicated a need for nitrate assimilation products. Together, these results indicate that the absence of remobilized purine-degraded N from older leaves of Atxdh1 caused senescence symptoms, a result of higher chloroplastic protein degradation in older leaves of low-nitrate-grown plants.

Eichhornia crassipes (water hyacinth), imparts deficiency of soluble arsenic and other toxic metal (loid)s through rhizofiltration and phytoaccumulation. Without proper management strategy, this phytoremediation of metal (loid)s might fail and get reverted back to the environment, contaminating the nearby water bodies. This study, focused on bio-conversion of phytoremediating hyacinths, spiked with 100 times and greater arsenic, lead and cadmium concentrations than the average water contamination, ranging in 58.81 ± 0.394, 16.74 ± 0.367, 12.18 ± 0.153 mg Kg−1arsenic, 18.95 ± 0.212, 9.53 ± 0.054, 6.83 ± 0.306 mg kg−1 lead and 2.79 ± 0.033, 1.39 ± 0.025, 0.92 ± 0.045 mg kg−1 cadmium, respectively in root, shoot and leaves, proving it's phytoaccumulation capacity. Next, these hyacinths has been used as a source of organic supplement for preparing vermicompost using Eisenia fetida following analysis of total metal content and sequential extraction. Control soil was having 134.69 ± 2.47 mg kg−1 arsenic in compare to 44.6 ± 0.91 mg kg−1 at premature stage of compost to 23.9 ± 1.55 mg kg−1 at mature compost indicating sustainable fate of phytoremediated vermicompost. This vermiremediation of arsenic and other toxic elements, restricted the bioavailability of soil pollutants. Furthermore, processed compost amended as organic fertilizer, growing chickpea, coriander, tomato and chilli plant, resulted in negligible metal(loid)s in treated samples, enhancing also plant's growth and production.

In the present study, arsenic (As) toxicity amelioration potential of a consortium of plant growth promoting rhizobacterium (Pseudomonas putida) and alga (Chlorella vulgaris) was evaluated during arsenate (AsV) exposure to rice (Oryza sativa) plants for 15 d. The consortium mediated amelioration of As toxicity was evident through improved growth of rice plants (root and shoot length and biomass) and reduced oxidative stress [as level of superoxide radicals (O2 −), hydrogen peroxide (H2O2) and membrane damage]. The positive responses were attributable to a significant decline in As accumulation in root (94 mg kg−1 dw) and shoot (51 mg kg−1 dw) in consortium (P. putida + C. vulgaris) inoculated seedlings as compared to As alone exposed plants (156 and 98 mg kg−1 dw, respectively). There were also significant changes in the level of various nutrient elements (Mn, Fe, Co, Zn, Mo and Cu), thiols and in the activities of antioxidant and thiol metabolism enzymes in the consortium inoculated seedlings that allowed the plants to tolerate As stress effectively and achieve better growth. The study demonstrated that consortium of P. putida and C. vulgaris may alleviate As stress and improve growth of rice seedlings along with reduction in As levels.

A study was performed for phyto-genotoxic assay of chromium (Cr) and arsenic (As) through Allium cepa. Various concentrations (0, 1, 3, 6 and 12 mg L−1) of Cr and As for 48 and 168 h time points exposed to A. cepa. The phytotoxic effects of metal(loid) were evident through inhibited root length and root protein. Metal(loid) toxicity also lead to genotoxic effects, which included depression of mitotic index and increased frequency of chromosomes aberrations like break, fragments, c-metaphase, multipolar arrangements etc. Genotoxic endpoint as progressive frequency of micronuclei in interphase of root meristem cells in treated plants was also observed. This genotoxic endpoint revealed carcinogenic nature of both aforementioned metal(loid). Along with inhibition in root length and protein content, depression in mitotic index as well as stimulation of various abnormality in mitotic cell division indicated that both metal(loid) are hazardous in nature and causing harmful effect on the environment.

Zinc is an essential element that is also renowned for widespread contamination and toxicity at high concentrations. The present study was carried out to analyze the responses induced by lower, as well as higher, doses of zinc (0–200 mg/L), in the form of zinc oxide nanoparticles (ZnO NPs) in wheat and maize, for a period of 21 days. Accumulation of zinc increases with increasing Zn doses in both wheat and maize, with higher doses being in wheat (121 mg/kg in root and 66 mg/kg in shoot) than in maize (95 mg/kg in root and 48 mg/kg in shoot). The activity of alpha-amylase showed increase, while that of dehydrogenase decline, in response to ZnO NPs. The length and biomass of plants and photosynthetic pigments increased slightly upon ZnO NPs supply. Malondialdehyde content showed a progressive increase in root and shoot of both plants. However, in response, antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase) showed increase up to lower concentrations (100 mg/L) of ZnO NPs but decline variably at higher levels (150–200 mg/L) in wheat and maize. The results suggest that lower supply of ZnO NPs (100 mg/L) could be stimulatory to the growth of plants and can be recommended as a Zn fertilizer source for crop production.

Hydrilla verticillata (L.f.) Royle is a widely distributed aquatic weed having prolific growth habits and a wide range of habitat. It can tolerate a wide range of physical and chemical conditions of water and can survive in low nutrient supply. Hydrilla is a potential accumulator of several metals and metalloids. The accumulation potential of Hydrilla plants is attributable to induced synthesis of thiol (-SH) containing ligands like glutathione and phytochelatins. Further, the uptake of metal(loid)s from both roots and leaves and movement in acropetal and basipetal directions allows plants to take up large quantity of metal(loid)s in short time span. Secondarily, antioxidant system is comprising of enzymatic and non-enzymatic components was found to rescue plants from metal(loid) induced oxidative stress. The used biomass of Hydrilla can be further utilized for composting, briquetting, pyrolysis and gasification. The high calorific fuel obtained from Hydrilla was found to have high heating value (44.06 MJ/kg) and low oxygen content (

The symbiotic associations between plants, microbes and fungi are examples of living in harmony. The intimate association between the arbuscular mycorrhizal fungi (AMF) and their host plants benefits the latter in nutrient (viz., phosphate, nitrogen etc.) acquisition in exchange of carbohydrates. Arsenic (As) accumulation in rice grains has become a serious issue in some parts of world having high As levels in soil and groundwater. To this end, experiments have demonstrated ameliorative potential of AMF colonization on As stress in rice. AMF colonization not only influences As concentrations in grains but also the speciation of As and reduces the ratios of inorganic/organic As concentrations. Positive influences of AMF colonization have also been linked to alteration in transport of As and phosphate, photosynthetic reactions and improved growth. A role of 14-3-3 proteins in AMF colonization under As stress is also suggested in recent studies. Importantly, grain yield has been found to increase in presence of AMF colonization. In this review, we discuss the molecular intricacies of rice-AMF in the context of As stress.

Arsenic is a highly toxic carcinogenic element whose contamination in groundwater and soil has emerged as a problem of unprecedented scale in last few years. The arsenic exposure to humans occurs through drinking water and food and threatens to increase incidences of cancer and other ailments drastically in future. To safeguard people from arsenic through food, research has focused on understanding in depth mechanisms of arsenic stress responses in plants. These included laboratory-based and field studies and encompassed morphological, physiological, biochemical and molecular assays and also whole genome transcriptome and proteome analyses. These studies led to information about changes at biochemical and molecular levels which are reflected in morphological and growth changes. Further, the involvement of various signalling and regulatory elements has been revealed. Among these, microRNAs (miRNAs), which are 20-25 base pairs long RNAs, have emerged as important players in mediated arsenic stress responses in plants. miRNAs have been found to regulate signalling elements, transcription factors, hormones biosynthesis and responses, oxidative stress responses, sulphur metabolism etc. This review presents a discussion on miRNAs involvement in arsenic stress responses in plants and also sheds light on future perspectives.

Salicornia and Sarcocornia are almost identical halophytes whose edible succulent shoots hold promise for commercial production in saline water. Enhanced sulfur nutrition may be beneficial to crops naturally grown on high sulfate. However, little is known about sulfate nutrition in halophytes. Here we show that Salicornia europaea (ecotype RN) exhibits a significant increase in biomass and organic-S accumulation in response to supplemental sulfate, whereas Sarcocornia fruticosa (ecotype VM) does not, instead exhibiting increased sulfate accumulation. We investigated the role of two pathways on organic-S and biomass accumulation in Salicornia and Sarcoconia: the sulfate reductive pathway that generates Cys and l-Cys desulfhydrase that degrades Cys to H2S, NH3, and pyruvate. The major function of O-acetyl-Ser-(thiol) lyase (OAS-TL; EC 2.5.1.47) is the formation of l-Cys, but our study shows that the OAS-TL A and OAS-TL B of both halophytes are enzymes that also degrade l-Cys to H2S. This activity was significantly higher in Sarcocornia than in Salicornia, especially upon sulfate supplementation. The activity of the sulfate reductive pathway key enzyme, adenosine 5′-phosphosulfate reductase (APR, EC 1.8.99.2), was significantly higher in Salicornia than in Sarcocornia. These results suggest that the low organic-S level in Sarcocornia is the result of high l-Cys degradation rate by OAS-TLs, whereas the greater organic-S and biomass accumulation in Salicornia is the result of higher APR activity and low l-Cys degradation rate, resulting in higher net Cys biosynthesis. These results present an initial road map for halophyte growers to attain better growth rates and nutritional value of Salicornia and Sarcocornia.

The prokaryotic βγ-crystallins are a large group of uncharacterized domains with Ca(2+)-binding motifs. We have observed that a vast number of these domains are found appended to other domains, in particular, the carbohydrate-active enzyme (CAZy) domains. To elucidate the functional significance of these prospective Ca(2+) sensors in bacteria and this widespread domain association, we have studied one typical example from Clostridium beijerinckii, a bacterium known for its ability to produce acetone, butanol, and ethanol through fermentation of several carbohydrates. This novel glycoside hydrolase of family 64 (GH64), which we named glucanallin, is composed of a βγ-crystallin domain, a GH64 domain, and a carbohydrate-binding module 56 (CBM56). The substrates of GH64, β-1,3-glucans, are the targets for industrial biofuel production due to their plenitude. We have examined the Ca(2+)-binding properties of this protein, assayed its enzymatic activity, and analyzed the structural features of the β-1,3-glucanase domain through its high-resolution crystal structure. The reaction products resulting from the enzyme reaction of glucanallin reinforce the mixed nature of GH64 enzymes, in contrast to the prevailing notion of them being an exotype. Upon disabling Ca(2+) binding and comparing different domain combinations, we demonstrate that the βγ-crystallin domain in glucanallin acts as a Ca(2+) sensor and enhances the glycolytic activity of glucanallin through Ca(2+) binding. We also compare the structural peculiarities of this new member of the GH64 family to two previously studied members. IMPORTANCE We have biochemically and structurally characterized a novel glucanase from the less studied GH64 family in a bacterium significant for fermentation of carbohydrates into biofuels. This enzyme displays a peculiar property of being distally modulated by Ca(2+) via assistance from a neighboring βγ-crystallin domain, likely through changes in the domain interface. In addition, this enzyme is found to be optimized for functioning in an acidic environment, which is in line with the possibility of its involvement in biofuel production. Multiple occurrences of a similar domain architecture suggest that such a “βγ-crystallination”-mediated Ca(2+) sensitivity may be widespread among bacterial proteins.

Arsenic accumulation in rice grains is a serious issue. This is due to the fact that rice is consumed all over the world in different forms by children to adults and also in particular high amount in certain regions of the world. Further, rice, from both arsenic contaminated and rather uncontaminated areas, has been found to have higher than permissible levels of As in grains (0.2 mg kg−1 dw). The presence of arsenic has also been detected in rice-based food products including baby foods. Hence, there is a greater need to devise feasible low-cost practices to reduce arsenic in rice grains. A number of chemical-based agronomic, feasible approaches have been studied till date which do hold a promise for achieving desirable arsenic reduction in rice grains. The present chapter discusses up-to-date knowledge on strategies for arsenic reduction in rice grains.

The presence of arsenic (As) in the groundwater threatens human health throughout the world. The problem is severe in southeastern parts of Asia especially India, Bangladesh, China, etc. because the population density is very high in comparison to the other western countries. Groundwater, which is the main source of drinking water in these areas, has been found to have As as high as 300 ppb. Out of 29 states in India, reports of As contamination have emerged from 17 states. The number of As-affected districts and the number of people affected have grown ever since the initial reports of As contamination came to knowledge in the 1980s. The present situation of As contamination in India is of great concern. This chapter focuses on presenting the As contamination status of India and also elaborates the possible reasons for groundwater As contamination in the Indo-Gangetic region.

Arsenic contamination, throughout the world, and its access to people through rice, rice-based food products, fish, mushrooms, vegetables, etc., is alarming. Furthermore, people residing in the heart of arsenic contaminated areas are at risk of exposure through drinking water too. There is an urgent need to counteract this burgeoning issue through cost-effective, feasible approaches that can be handled even at a local village level by untrained local people. To this end, phytoremediation offers hope for fulfilling these requirements. This chapter discusses phytoremediation prospects for arsenic affected environments.

Arsenic (As) is a ubiquitously distributed toxic element, and it has been present in the environment since the very beginning of evolution. Hence, microbes to higher organisms possess mechanisms to tackle arsenic that include conversion of arsenic from one form to another including inorganic to organic and vice versa. Microbes present in different environments possess a number of pathways for arsenic conversion and therefore play a crucial role in arsenic cycling in the environment. Arsenic contamination has emerged as a serious problem in some parts of the world in the past few decades. These include Bangladesh, India, China, Vietnam, Pakistan, etc. The presence of arsenic in soil and groundwater in affected areas also leads to the entry of arsenic in plants. The level of arsenic accumulation in plants including edible portions depends on the arsenic species. In this scenario, microbes, which affect arsenic speciation, can play a role in regulating arsenic accumulation and consequently arsenic stress in plants. The microbes can therefore be utilized effectively to safeguard crop plants from arsenic. If the microbes also possess plant growth-promoting ability, this strategy can impart further benefits. A number of plant growth-promoting microbes (PGPMs) have been identified, characterized and utilized for the improvement of growth of plants in arsenic-contaminated environment as well as for the reduction of arsenic levels in plants. This review presents the role of microbes in arsenic cycling in the environment and discusses efforts for their utilization in the amelioration of arsenic stress in plants.

Ulmus pumila L. is an excellent afforestation and biofuel tree that produces high-quality wood, rich in starch. In addition, U. pumila is highly adaptable to adverse environmental conditions, which is conducive to its utilization for vegetating saline soils. However, little is known about the physiological responses and transcriptional regulatory network of U. pumila under salt stress. In this study, we exposed five main cultivars in saline–alkali land (Upu2, 5, 8, 11, and 12) to NaCl stress. Of the five cultivars assessed, Upu11 exhibited the highest salt resistance. Growth and biomass accumulation in Upu11 were promoted under low salt concentrations (&lt, 150 mM). However, after 3 months of continuous treatment with 150 mM NaCl, growth was inhibited, and photosynthesis declined. A transcriptome analysis conducted after 3 months of treatment detected 7009 differentially expressed unigenes (DEGs). The gene annotation indicated that these DEGs were mainly related to photosynthesis and carbon metabolism. Furthermore, PHOTOSYNTHETIC ELECTRON TRANSFERH (UpPETH), an important electron transporter in the photosynthetic electron transport chain, and UpWAXY, a key gene controlling amylose synthesis in the starch synthesis pathway, were identified as hub genes in the gene coexpression network. We identified 25 and 62 unigenes that may interact with PETH and WAXY, respectively. Overexpression of UpPETH and UpWAXY significantly increased the survival rates, net photosynthetic rates, biomass, and starch content of transgenic Arabidopsis plants under salt stress. Our findings clarify the physiological and transcriptional regulators that promote or inhibit growth under environmental stress. The identification of salt-responsive hub genes directly responsible for photosynthesis and starch synthesis or metabolism will provide targets for future genetic improvements.

The present study analysed time (0.5 h to 24 h) and tissue [roots, old leaves (OL) and young leaves (YL)] dependent nature of arsenic (As) accumulation and ensuing responses in two contrasting varieties of rice (Oryza sativa L.); Pooja (tolerant) and CO-50 (moderately sensitive). Arsenic accumulation was 5.4-, 4.7- and 7.3-fold higher at 24 h in roots, OL and YL, respectively of var. CO-50 than that in var. Pooja. Arsenic accumulation in YL depicted a delayed accumulation; at 2 h onwards in var. Pooja (0.23 µg g−1 dw) while at 1 h onwards in var. CO50 (0.26 µg g−1 dw). The responses of oxidative stress parameters, antioxidant enzymes, metabolites and ions were also found to be tissue- and time-dependent and depicted differential pattern in the two varieties. Among hormone, salicylic acid and abscisic acid showed variable response in var. Pooja and var. CO-50. Metabolite analysis depicted an involvement of various metabolites in As stress responses of two varieties. In conclusion, an early sensing of the As stress, proper coordination of hormones, biochemical responses, ionic and metabolic profiles allowed var. Pooja to resist As stress and reduce As accumulation more effectively as compared to that of var. CO-50.

The present study was performed with two contrasting genotypes of rice, tolerant (Pooja) and moderately sensitive (CO-50), to evaluate their differential responses to arsenic (As, 50 mg kg−1 soil) stress without or with thiourea (TU, 6.57 mM) application. The study analyzed tissue specific responses (root, old leaf; OL and young leaf; YL) of rice plants. TU was applied at different stages, viz., seed soaking and 25 days after sowing (DAS) and final harvesting was done at 45 DAS. Arsenic accumulation in Pooja roots (1067.94 μ g g−1 dw), OL (131.67 μ g g−1 dw) and YL (38.34 μ g g−1 dw) was lower than that detected in CO-50 roots (4763.97 μ g g−1 dw), OL (866.94 μ g g−1 dw) and YL (334.08 μ g g−1 dw) in As alone treatment. Arsenic stressed plants of both varieties showed reduced growth, decline in photosynthetic pigments and protein content. There was an increase in activity of antioxidant enzymes, SOD and GPX and total S in both varieties and root anatomical features were disturbed. Pooja showed lesser toxicity as compared to that of CO-50 in terms of various analyzed responses. The positive effects of TU on two varieties were visible as enhanced plant’s growth in comparison to As alone treatment. The biochemical parameters showed a change in As+TU treatment so as to approach towards control value. The positive effect of TU was attributable to significant decline in As concentrations in both varieties. In conclusion, TU application can be a sustainable and feasible way to reduce As toxicity and accumulation in rice in field.