Search

The present study analyzed the effects of individual microbes and their consortium (Priestia endophytica NDAS01F, Bacillus licheniformis NDSA24R, and P. flexa NDAS28R) either alone or in interaction with thiourea (TU) on growth and responses of rice plants subjected to As stress (50 mg kg

Arsenic (As) is a major threat to the environment and human health due to its toxicity and carcinogenicity. Occurrence of alarming concentrations of As in water and soil leads to its bioaccumulation in crops which is a major health concern globally. Rice (Arsenic (As) contamination in water, soil, and crops is creating a difficult situation for the large population across the globe. Various efforts are being made to reduce As levels in rice as it is a staple crop. This review presents recent biotechnological advances toward the development of low As accumulating rice. The review shall be an important information resource for the readers on the topic.

Multifunctional plant growth-promoting bioinoculants are used to enhance growth, harvest yields, and add economic value to agricultural crops. In this study, such bioinoculant, BC-II-20 (Pseudomonas sp.), was isolated from the rhizospheric soil of a medicinal plant Bergenia ciliata from the Garhwal Himalayas, Uttarakhand, India. After characterization, supplementation with Pseudomonas sp. was used to study growth stimulation in a commercially important medicinal plant, Andrographis paniculata (Kalmegh), and it depicted enhanced physiological growth parameters under controlled conditions. Bacterial seed priming and also supplementation led to early and increased germination and plants displayed better vegetative growth during the entire growth stages. Early initiation of flowers and the appearance of pods occurred in inoculated plants, ultimately leading to the reduction in the life cycle of the plant. At the time of harvesting, there was an increase in the physiological parameters such as shoot length (38%), root length (14%), fresh weight (57%), dry weight (60%), number of panicles, and root branching. Photosynthetic efficiency was also higher, and ultimately, overall plant growth was improved by bacterial inoculation. The eco-friendly and sustainable use of this bioinoculant will provide an alternative to harmful chemical fertilizers and has become increasingly important. In conclusion, we reported a promising bioinoculant having plant growth-promoting traits, which promotes growth and development in A. paniculata and may be applied to other plants also.

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.

Metal contamination of the environment is a widespread problem threatening sustainable and safe crop production. Physio-biochemical and molecular mechanisms of plant responses to metal exposure have been studied to establish the best possible agronomical or biotechnological methods to tackle metal contamination. Metal stress tolerance is regulated by several molecular effectors among which microRNAs are one of the key master regulators of plant growth and stress responses in plants. MicroRNAs are known to coordinate multitude of plant responses to metal stress through antioxidant functions, root growth, hormonal signalling, transcription factors and metal transporters. The present review discusses integrative functions of microRNAs in the regulation of metal stress in plants, which will be useful for engineering stress tolerance traits for improved plant growth and productivity in metal stressed situations.

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.

Phytoremediation of environmental contaminants is a promising strategy, however, the success depends on the use of suitable plants.

Plants live under different biotic and abiotic stress conditions, and, to cope with the adversity and severity, plants have well-developed resistance mechanisms. The mechanism starts with perception of the stimuli followed by molecular, biochemical, and physiological adaptive measures. The family of LRR-RLKs (leucine-rich repeat receptor-like kinases) is one such group that perceives biotic and abiotic stimuli and also plays important roles in different biological processes of development. This has been mostly studied in the model plant, Arabidopsis thaliana, and to some extent in other plants, such as Solanum lycopersicum, Nicotiana benthamiana, Brassica napus, Oryza sativa, Triticum aestivum, Hordeum vulgare, Brachypodium distachyon, Medicago truncatula, Gossypium barbadense, Phaseolus vulgaris, Solanum tuberosum, and Malus robusta. Most LRR-RLKs tend to form different combinations of LRR-RLKs-complexes (dimer, trimer, and tetramers), and some of them were observed as important receptors in immune responses, cell death, and plant development processes. However, less is known about the function(s) of LRR-RLKs in response to abiotic and biotic stresses. Here, we give recent updates about LRR-RLK receptors, specifically focusing on their involvement in biotic and abiotic stresses in the model plant, A. thaliana. Furthermore, the recent studies on LRR-RLKs that are homologous in other plants is also reviewed in relation to their role in triggering stress response processes against biotic and abiotic stimuli and/or in exploring their additional function(s). Furthermore, we present the interactions and combinations among LRR-RLK receptors that have been confirmed through experiments. Moreover, based on GENEINVESTIGATOR microarray database analysis, we predict some potential LRR-RLK genes involved in certain biotic and abiotic stresses whose function and mechanism may be explored.

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.

Alternate wetting-drying (AWD) cultivation with implication on soil microbiome, nutritional dynamics and rice yield during pre-monsoon (boro) and monsoon (aman) season are not well studied. In the present 4-year field study the impact of AWD (in pre-monsoon season) is compared with conventional mode of irrigation (i.e. flooded field in monsoon season). The release of soil nutrients into the soil-aqueous system, influencing microbial populations and modulating the redox status were explored. Results indicated an increase in total content as well as bioavailability of selected nutritional elements (N, P, K, Fe, Ca, Mg, Cu and Zn) by 16-54% in the pre-monsoon cultivation relative to monsoon cultivation. Three plant growth phases (developing, milking and harvest) were considered to check the nutrient modulations in soil and plant tissues along the continuum plant growth and elemental uptake. Krona charts, relative abundance, rarefaction curve and multivariate analysis of metagenomics data showed that the pre-monsoon soil was more enriched and maintained a balance between soil pH and microbial biomass than the monsoon soil. Microbial community diversity associated with plant growth phases also found to be different depending on the seasonal alterations. Bacillus sp., Acidothiobacillus sp., Pseudomonas sp., Rhizobium sp., Burkholderia sp. were predominant in pre-monsoon soil releasing pulses of N, P, K, Ca and Mg whereas Verrucomicrobia was found to be dominant in monsoon soil where Fe was released. This study is a first of its kind that showed the combined effect of season and soil microbes on macro-micro nutritional availability in soil and enhanced plant quality. Keywords: Soil quality; Metagenomics; Nutrient availability; Pre-monsoon irrigation; Resource conservation; Soil microbiome

Unexpected bioaccumulation and biomagnification of heavy metal(loid)s (HMs) in the environment have become a predicament for all living organisms, including plants. The presence of these HMs in the plant system raised the level of reactive oxygen species (ROS) and remodeled several vital cellular biomolecules. These lead to several morphological, physiological, metabolic, and molecular aberrations in plants ranging from chlorosis of leaves to the lipid peroxidation of membranes, and degradation of proteins and nucleic acid including the modulation of the enzymatic system, which ultimately affects the plant growth and productivity. Plants are equipped with several mechanisms to counteract the HMs toxicity. Among them, seed priming (SP) technology has been widely tested with the use of several inorganic chemicals, plant growth regulators (PGRs), gasotransmitters, nanoparticles, living organisms, and plant leaf extracts. The use of these compounds has the potential to alleviate the HMs toxicity through the strengthening of the antioxidant defense system, generation of low molecular weight metallothionein's (MTs), and phytochelatins (PCs), and improving seedling vigor during early growth stages. This review presents an account of the sources, uptake and transport, and phytotoxic effects of HMs with special attention to different mechanism/s, occurring to mitigate the HMs toxicity in plants employing SP technology.

The present article represents the data for analysis of microbial consortium (

The ABO histo-blood group, the critical determinant of transfusion incompatibility, was the first genetic polymorphism discovered in humans. Remarkably, ABO antigens are also polymorphic in many other primates, with the same two amino acid changes responsible for A and B specificity in all species sequenced to date. Whether this recurrence of A and B antigens is the result of an ancient polymorphism maintained across species or due to numerous, more recent instances of convergent evolution has been debated for decades, with a current consensus in support of convergent evolution. We show instead that genetic variation data in humans and gibbons as well as in Old World monkeys are inconsistent with a model of convergent evolution and support the hypothesis of an ancient, multiallelic polymorphism of which some alleles are shared by descent among species. These results demonstrate that the A and B blood groups result from a trans-species polymorphism among distantly related species and has remained under balancing selection for tens of millions of years—to date, the only such example in hominoids and Old World monkeys outside of the major histocompatibility complex.

Water is a scarce resource in this millennium, especially clean water. Reverse osmosis (RO) technology is widely applied to achieve this goal. But, reverse osmosis waste water (ROWW) cannot be further utilized, due to the presence of a high concentration of salts, heavy metals, and pollutants of feed water. The solution to this problem may lie in employing plants for this very purpose that is phytoremediation. Phytoremediation converts this waste water into usable water with the help of plants. This is an eco-friendly technique that decontaminates the waste water in a very economical way. This mini-review thus, emphasizes on quality improvement of RO waste water through plant-based techniques with a special focus on recent studies carried out in this area. Keywords: Phytodegradation, Phytoextraction, Phytoremediation, Phytovolatilization, Reverse osmosis (RO), Reverse osmosis waste water (ROWW), Rhizodegradation.

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 migration of extracellular antibiotic resistance genes (eARGs) in porous media is an important pathway for ARGs to spread to the subsoil and aquifer. Biochar (BC) has been widely used to reduce the mobility of soil contaminants, however, its effect on the mobility of eARGs in porous media and the mechanisms are largely unknown. Herein, the effects of BCs synthesized from wheat straw and corn straw at two pyrolysis temperatures (300 °C and 700 °C) on the transport of plasmids-carried eARGs in sand column were investigated. The BC amendments all significantly decreased the mobility of eARGs in the porous medium, but the mechanism varied with pyrolysis temperature. The higher temperature BCs had a stronger irreversible adsorption of plasmids and greatly enhanced the attachment and straining effects on plasmids during transport, thus more effectively inhibited the mobility of eARGs. The lower temperature BCs had weaker adsorption, attachment, and straining effects on plasmids, but induced generation of hydroxyl radicals in the porous medium and thereby fragmented the plasmids and hindered the amplification of eARGs. These findings are of fundamental significance for the potential application of BC in controlling the vertical spread of eARGs in soil and vadose zones.

Different natural and anthropogenic global events and activities such as urban settlements and industrial development have led to a build-up of numerous pollutants in the environment, creating problems for nature and human health. Among the pollutants, metal(loid)s are persistent and ubiquitously present in the soil, water, and air. The presence of high concentrations of metal(loid)s in water is of serious concern, as water is a basic necessity of humans and plants. Through irrigation, metal(loid)s enter and accumulate in plants, and subsequently reach humans via food. There is demand for sustainable and practical technologies for tackling the challenge of metal(loid) pollution. Nanotechnology has found its place in diverse fields including cosmetics, sensors, remediation, and medicine. Nanoremediation is an effective, feasible, and sustainable technology for cleaning up water contaminated with metal(loid)s and other chemicals. The versatility of nanomaterials is huge due to their differences in size, shape, surface chemistry, and chemical composition. This review sheds light on different nanoparticles (NPs) used for water remediation and summarizes key recent findings. The successful application of NPs in laboratory studies warrants their potential use in water clean-up from a small to a large scale.

Thiourea (TU) is a chemo-priming agent and non-physiological reactive oxygen species (ROS) scavenger whose application has been found to reduce As accumulation in rice grains along with improved growth and yield. The present field study explored TU-mediated mechanistic changes in silicon (Si) assimilation in root/shoot, biochemical and molecular mechanisms of arsenic (As) stress amelioration in rice cultivars. Gosai and Satabdi (IET-4786) rice cultivars were selected for field experiment at three different places; control field and two other As contaminated experimental fields (EF1 and EF2) in West Bengal, India. The average As reduction was observed to be 9.5% and 19.8% whereas the yield increment was 8.8% and 17.7% for gosai and satabdi, respectively among all the three experimental fields. The positive interrelation was also observed between improved internal ultrastructure anatomy and enhanced Si assimilation (36%-423%) upon TU application. The level of photosynthetic pigments was increased by 29.8%-99.2%. Further, activities of antioxidant enzymes were harmonically altered in TU supplemented plants. The expression of various As related transporter genes in flag leaf and developing grains (inflorescence) was changed in both the rice cultivars (gosai and satabdi). It was also presumably responsible for observed As reduction in grains. Thus, TU application was found to be an efficient and sustainable agronomic practice for amelioration of As toxicity in rice plants in As contaminated field conditions.

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.

Drought, a major abiotic limiting factor, could be modulated with in-built reprogramming of plants at molecular level by regulating the activity of plant developmental processes, stress endurance and adaptation. The transgenic Arabidopsis thaliana over-expressing metallothionein 1 (MT1) gene of desi chickpea (Cicer arietinum L.) was subjected to transcriptome analysis. We evaluated drought tolerance of 7 days old plants of Arabidopsis thaliana in both wild-type (WT) as well as transgenic plants and performed transcriptome analysis. Our analysis revealed 24,737 transcripts representing 24,594 genes out of which 5,816 were differentially expressed genes (DEGs) under drought conditions and 841 genes were common in both genotypes. A total of 1251 DEGs in WT and 2099 in MT1 were identified in comparison with control. Out of the significant DEGs, 432 and 944 were upregulated, whereas 819 and 1155 were downregulated in WT and MT1 plants, respectively. The physiological and molecular parameters involving germination assay, root length measurements under different stress treatments and quantitative expression analysis of transgenic plants in comparison to wild-type were found to be enhanced. CarMT1 plants also demonstrated modulation of various other stress-responsive genes that reprogrammed themselves for stress adaptation. Amongst various drought-responsive genes, 24 DEGs showed similar quantitative expression as obtained through RNA sequencing data. Hence, these modulatory genes could be used as a genetic tool for understanding and delineating the mechanisms for fine-tuning of stress responses in crop plants.

The arsenic (As) contamination demands its remediation from the environment which is naturally possible by the application of Pteris vittata L. However, biomonitoring of phytoremediation potential of P. vittata at chromosomal and DNA level is still meager. The present study was designed to biomonitor the phytoremediation efficiency of P. vittata through phytotoxic and cyto-genotoxic biomarkers assessment using Trigonella foenum-graecum L. (Fenugreek; Methi) as test system. Study revealed hyperaccumulation potential of P. vittata which extracted arsenic in its tissues. Biomonitoring evaluation depicted that phytotoxic damage was reduced in Trigonella exposed to remediated soil, which was revealed through reduced electrolyte leakage, hydrogen peroxide and MDA content. Moreover, cyto-genetic endpoints like mitotic depression (44.03%), relative abnormality rate (16.6%) and chromosomal abnormality frequency (1.06%) were also lesser in test plants grown in remediated soil compared to those grown in non-remediated soil. Along with this various chromosomal aberrations like stickiness, breaks, laggards, bridges, fragmentations and micronuclei were also augmented in test plants exposed to non-remediated arsenic enriched soil. It was evident that arsenic enriched soil caused toxicity to plants in dose-dependent manner that was assessable through the analysis of biochemical parameters and cyto-genetic biomarkers. The cyto-genetic biomarkers are very efficient, simple and non-expensive tools to biomonitor arsenic toxicity at chromosomal as well as DNA level to assess the remediation potential of P. vittata in field conditions.

The roles of cytosolic O-acetylserine-(thiol)-lyase A (OASTLA), chloroplastic OASTLB, and mitochondrial OASTLC in plant selenate resistance were studied in Arabidopsis. Impairment in OASTLA and OASTLB resulted in reduced biomass, chlorophyll and soluble protein content compared with selenate-treated OASTLC-impaired and wild-type plants. The generally lower total selenium (Se), protein-Se, organic-sulfur and protein-sulfur (S) content in oastlA and oastlB compared with wild-type and oastlC leaves indicated that Se accumulation was not the main cause for the stress symptoms in these mutants. Notably, the application of selenate positively induced S-starvation markers and the OASTLs, followed by increased sulfite reductase, sulfite oxidase activities, and increased sulfite and sulfide concentrations. Taken together, our results indicate a futile anabolic S-starvation response that resulted in lower glutathione and increased oxidative stress symptoms in oastlA and oastlB mutants. In-gel assays of l-cysteine and l-seleno-cysteine, desulfhydrase activities revealed that two of the three OASTL activity bands in each of the oastl single mutants were enhanced in response to selenate, whereas the impaired proteins exhibited a missing activity band. The absence of differently migrated activity bands in each of the three oastl mutants indicates that these OASTLs are major components of desulfhydrase activity, degrading l-cysteine and l-seleno-cysteine in Arabidopsis.

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.

The present study analysed the levels of potentially toxic elements along with physico-chemical properties of agricultural soil samples (n = 59) collected from fields situated along the path of river Ganga in the middle Gangetic floodplain in two districts, Ballia and Ghazipur. Arsenic (As), chromium (Cr), copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), iron (Fe) and manganese (Mn) levels were analysed by Wavelength Dispersive-X-Ray Fluorescence Spectroscopy (WD-XRF) and the associated health risks along with diverse indices were calculated. The mean concentrations of As, Cu, Cr, Pb, Zn and Ni were found to be 15, 42, 85, 18, 87 and 47 mg kg

Abiotic stress in plants is a crucial issue worldwide, especially heavy-metal contaminants, salinity, and drought. These stresses may raise a lot of issues such as the generation of reactive oxygen species, membrane damage, loss of photosynthetic efficiency, etc. that could alter crop growth and developments by affecting biochemical, physiological, and molecular processes, causing a significant loss in productivity. To overcome the impact of these abiotic stressors, many strategies could be considered to support plant growth including the use of nanoparticles (NPs). However, the majority of studies have focused on understanding the toxicity of NPs on aquatic flora and fauna, and relatively less attention has been paid to the topic of the beneficial role of NPs in plants stress response, growth, and development. More scientific attention is required to understand the behavior of NPs on crops under these stress conditions. Therefore, the present work aims to comprehensively review the beneficial roles of NPs in plants under different abiotic stresses, especially heavy metals, salinity, and drought. This review provides deep insights about mechanisms of abiotic stress alleviation in plants under NP application.

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.