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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. Image 1 • Implementation of intermittent irrigation in rice cultivation significantly reduces arsenic accumulation in rice plant. • Dry-wet irrigation practice renders the lesser arsenic mobilization involving soil physico-chemical parameters. • Soil silicon dissolution is enhanced under intermittent dry-wet phase from H 4 SiO 4 bound minerals. • Increased silicon uptake suppresses arsenic translocation and improves rice internal ultra-structure. • Stress markers are lower in silicon rich plants under intermittent irrigation over conventional flooding practice. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a toxic element with the potential to cause health effects in humans. Besides rice is a source of both amino acids (AAs) and mineral nutrients, it is undesired source of As for billions of people consuming rice as the staple food. Selenium (Se) is an essential metalloid, which can regulate As toxicity by strengthening antioxidant potential. The present study was designed to investigate As III stress mitigating effect of Se VI in rice. The level of As, thiolic ligands and AAs was analyzed in rice seedlings after exposure to As III /Se VI alone and As III +Se VI treatments. Selenate supplementation (As III 25 μM+Se VI 25 μM) decreased total As accumulation in both root and shoot (179 & 144%) as compared to As III alone treatment. The As III +Se VI treatment also induced the levels of non-protein thiols (NPTs), glutathione (GSH) and phytochelatins (PCs) as compared to As III alone treatment and also modulated the activity of enzymes of thiol metabolism. The content of amino acids (AAs) was significantly altered with Se VI supplementation. Importantly, essential amino acids (EAAs) were enhanced in As III +Se VI treatment as compared to As III alone treatment. In contrast, stress related non-essential amino acids (NEAAs) like GABA, Glu, Gly, Pro and Cys showed enhanced levels in As III alone treatment. In conclusion, rice supplemented with Se VI tolerated As toxicity with reduced As accumulation and increased the nutrition quality by increasing EAAs. [ABSTRACT FROM AUTHOR]

The present study evaluated uranium (U) removal ability and tolerance to low level nuclear waste (LLNW) of an aquatic weed Hydrilla verticillata . Plants were screened for growth in 10%–50% waste treatments up to 3 d. Treatments of 20% and 50% waste imposed increasing toxicity with duration assessed in terms of change in fresh weight and in the levels of photosynthetic pigments and thiobarbituric acid-reactive substances. U concentration, however, did not show a progressive increase and was about 42 μg g −1 dw from 20% to 50% waste at 3 d. This suggested that a saturation stage was reached with respect to U removal due to increasing toxicity. However, in another experiment with 10% waste and 10% waste+10 ppm U treatments, plants showed an increase in U concentration with the maximum level approaching 426 μg g −1 dw at 3 d without showing any toxicity as compared to that at 20% and 50% waste treatments. Hence, plants possessed significant potential to take up U and toxicity of LLNW limited their U removal ability. This implies that the use of Hydrilla plants for U removal from LLNW is feasible at low concentrations and would require repeated harvesting at short intervals. [ABSTRACT FROM AUTHOR]

In the present study, Hydrilla verticillata plants were exposed to arsenate (AsV; 50μM) and arsenite (AsIII; 5μM) under variable S supply: deficient (2μM S, –S), normal (1mM S, +S) and excess (2mM S, +HS). Arsenic accumulation (μgg−1 dw) in +HS plants was about 2-fold higher upon exposure to both AsV (30) and AsIII (50) than that observed in +S (12 & 24) and –S (14 & 26) plants. Despite lower As accumulation, –S plants experienced the maximum oxidative stress owing to an inadequate response of enzymatic and molecular antioxidants and significant decline in total thiols and the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG). By contrast +HS plants had significant increase in total thiols and an improved redox status, did not demonstrate any negative impact to antioxidants except catalase and hence experienced the least increase in oxidative stress parameters. In conclusion, an increase in S supply to plants may improve their accumulation capacity for As through enhanced tolerance caused by a positive effect on thiol metabolism and antioxidant status of the plants. [Copyright &y& Elsevier]

The physiological, biochemical, and proteomic changes in germinating rice seedlings were investigated under arsenic stress. A marked decrease in germination percentage, shoot, and root elongation as well as plant biomass was observed with arsenic treatments, as compared to control, whereas accumulation of arsenic and malondialdehyde (MDA) in seedlings were increased significantly with increasing arsenic concentration (both AsIII and AsV). The up-regulation of some antioxidant enzyme activities and the isozymes of superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), peroxidase (POD, EC 1.11.1.7), and glutathione reductase (GR, 1.6.4.2) substantiated that arsenic accumulation generated oxidative stress, which was more pronounced in As(III) treatment. We also studied the protective effect of reduced glutathione (GSH) and cysteine (Cys) to As(III)/As(V) stressed seedlings. Both GSH and Cys imparted enhanced tolerance to seedlings against arsenic stress. Seedlings growth improved while level of MDA declined significantly when GSH and Cys were supplemented to As(III)/As(V) treatments suggesting GSH and Cys-mediated protection against oxidative stress. The arsenic content was highest in roots of seedlings grown in As(III) in the presence of GSH/Cys. However, in case of As(V) plus GSH or Cys, the arsenic content in seedlings was highest in shoots. The results are suggestive of differential metabolism of As(III) and As(V) in rice. [Copyright &y& Elsevier]

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. [Display omitted] • P.putida + C.vulgaris ameliorated arsenic toxicity by modulating the defensive pathways. • P.putida + C.vulgaris efficient to modulate transcription factors which provide tolerance by reducing As uptake. • P.putida + C.vulgaris modulated the expression of transporters. • Rice with high nutritional value during As exposure achieved through P.putida + C.vulgaris. [ABSTRACT FROM AUTHOR]

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 −1 arsenic, 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. [ABSTRACT FROM AUTHOR]

• Rice grains and rice based food products were analyzed for As, Zn, Cu and Fe. • Arsenic concentration showed a range of 0.04 – 0.45 μg g-1 in rice grains. • Hazard Quotient was found to be >1 for rice grains in all cities. • The carcinogenic risk of As for rice grains was higher than acceptable safe limit. • Rice consumption may not provide daily recommended Fe to people in most cities. The present study measured arsenic (As), copper (Cu), zinc (Zn) and iron (Fe) concentrations in grains of different rice varieties and rice based food products collected from various cities located in Gangetic basin in India. Total 44 rice samples were collected from local markets from different locations and analyzed for elemental concentrations by Atomic Absorption Spectroscopy. The results showed that the mean concentration of As, Zn, Cu and Fe were 0.15 ± 0.10, 117 ± 24, 4.6 ± 0.5 and 32.5 ± 5.7 μg g-1 dw, respectively in rice grains and 0.17 ± 0.09, 193 ± 241, 4.5 ± 1.0 and 45.7 ± 25 μg g-1 dw, respectively in rice based food products. The hazard quotient (HQ) of As was the lowest in Patna (2.4) and the highest in Kolkata (5.0) but it was always higher than threshold value of one. The carcinogenic risk of the As for rice grains was found to be higher (10-3) than safe range of 10-6-10-4 set by USEPA except Jabalpur. Daily consumption analyses also indicated that consumption of rice and rice products was not sufficient to fulfill daily requirement of Fe in most of the cities. The present results implicate that the consumption of rice and rice products may act as source of As on one hand and may not provide sufficient essential elements on the other. [ABSTRACT FROM AUTHOR]