Effects of Arsenic and Their Mitigation in Plants (original) (raw)
Related papers
Potential Arsenic Enrichment Problems of Rice and Vegetable Crops
Elevated arsenic level in ground water has emerged as extreme calamity exposing a large population in to the risk of arsenic toxicity from drinking water sources and agricultural products, especially through ground water irrigation. Arsenic concentration of irrigated groundwater, soil, crops and vegetables were assessed in high arsenic affected blocks of Nadia district. Consumption of arsenic contaminated drinking water is the primary route of exposure, along with food as additional source. Arsenic concentrations in irrigation water, field soil and in different parts of grown crops have been assessed to show the bioaccumulation level of arsenic in food chain. Arsenic in irrigated water ranges from 0.23 to 0.73 mg L -1 and 3.58 to 8.50 mg Kg -1 of dry weight in irrigated soil. Inorganic arsenic concentration in various edible and useful parts of rice plants in our experiment are in the order of 2.52 1 to 5.97 mg Kg -1 of dry weight in straw; 0.71 to 1.79 mg Kg -1 of dry weight in husk and 0.10 to 0.81mg Kg -1 of dry weight in rice grain. Higher range of arsenic is assessed in the rabi season vegetables like in spinach 0.96 to 1.63 mg Kg -1 of dry weight, 0.051 to 1.14 mg Kg -1 of dry weight in tomato fruit, and 1.45 to 3.24 mg Kg -1 of dry weight in Bengal gram. Relationships among ground water arsenic content, soil arsenic and edible parts of crops and vegetables have been assessed. Concentration factor and enrichment factor indicates towards the potential risk of human health due to dietary arsenic transfer in to the crops and vegetables.
Arsenic Pollution in Agriculture: Its Uptake and Metabolism in Plant System
Arsenic Pollution in Agriculture: Its Uptake and Metabolism in Plant System, 2016
Arsenic is widely distributed in the soil, water, air and all living matters. Presently arsenic pollution through food-chain contamination is a major health concern worldwide. It poses menacing damage compared to arsenic pollution in drinking water. Arsenic may occur in both inorganic and organic forms. Arsenate can compete with phosphate within the plant cells disturbing the energy flow in the cell. Arsenite reacts with a number of enzymes and tissue proteins that can cause inhibition of cellular function and finally death. Arsenate is taken up by plants via phosphate uptake system, while arsenite is taken up through water channels or aquaporins in the roots. Arsenic is then transported from root to leaves through xylem. However, different forms of arsenic have different translocation efficiencies. Different crop plants have exhibited varying tendencies to accumulate arsenic in different plant parts in the following order, root > stem > leaf > economic produce. Plants can combat with arsenic accumulation either by formation of antioxidant enzyme system or by chelating the toxin with certain ligands (e.g. metallothioneins, phytochelatins) or by sequestering them in sub- or extra-cellular organelles and thus prevents the normal metabolic process from the interference of arsenic.
Strategies for Reducing Arsenic Content in Rice: A review
Journal of Central European Green Innovation
Arsenic (As) is one of the most toxic metalloid that can enter the food chain through ingestion of As contaminated water or food, posing a serious threat to human health. Among cereals, rice could contain the highest amount of As because of the special growing conditions. Therefore, the importance of the reduction of As concentration in rice is essential. Many studies have been conducted to understand the mechanism of arsenic uptake, accumulation and translocation. The interactions between As and plants are influenced by soil type and other factors such as pH, mineral contents and redox status of the soil, As speciation, and microbial activity. Different nutrients including phosphates, iron, silicon and sulfur effectively regulate the uptake and accumulation of As in different parts of plants. Genetic variation has also effect on As accumulation of rice grain. Water management practices can help to decrease As content of rice plants due to changing the redox status of the soil. Phos...
Chemosphere, 2017
Growing rice on arsenic (As)-contaminated soil or irrigating with As-contaminated water leads to significant accumulation of As in grains. Moreover, rice accumulates more As into grains than other cereal crops. Thus, rice consumption has been identified as a major route of human exposure to As in many countries. Inorganic As species are carcinogenic and could pose a considerable health risk to humans even at low dietary concentration. Genotypic variation and concentration of nutrients such as iron, manganese, phosphate, sulfur and silicon are the two main factors that affect As accumulation in rice grains. Therefore, in addition to better growth and yield of plants, application of specific nutrients in optimum quantities offers an added benefit of decreasing As content in rice grains. These nutrient elements influence speciation of As in rhizosphere, compete with As for root uptake and interfere with As translocations to the shoot and ultimately accumulation in grains. This papers c...
Arsenic (As) is a metalloid that poses serious environmental threats due to its behemoth toxicity and wide abundance. The use of arsenic-contaminated groundwater for irrigation purpose in crop fields elevates arsenic concentration in surface soil and in the plants. In many arsenic-affected countries, including Bangladesh and India, rice is reported to be one of the major sources of arsenic contamination. Rice is much more efficient at accumulating arsenic into the grains than other staple cereal crops. Rice is generally grown in submerged flooded condition, where arsenic bioavailability is high in soil. As arsenic species are phytotoxic, they can also affect the overall production of rice, and can reduce the economic growth of a country. Once the foodstuffs are contaminated with arsenic, this local problem can gain further significance and may become a global problem, as many food products are exported to other countries. Large-scale use of rainwater in irrigation systems, bioremediation by arsenic-resistant organisms and hyperaccumulating plants, and the aerobic cultivation of rice are some possible ways to reduce the extent of bioaccumulation in rice. Investigation on a complete food chain is urgently needed in the arsenic-contaminated zones, which should be our priority in future researches.
Arsenic Accumulation and Metabolism in Rice ( Oryza sativa L.)
Environmental Science & Technology, 2002
The 5 use of arsenic (As) contaminated groundwater for irrigation of crops has resulted in elevated concentrations of arsenic in agricultural soils in Bangladesh, West Bengal (India), and elsewhere. Paddy rice (Oryza sativa L.) is the main agricultural crop grown in the arsenic-affected areas of Bangladesh. There is, therefore, concern regarding accumulation of arsenic in rice grown those soils. A greenhouse study was conducted to examine the effects of arsenic-contaminated irrigation water on the growth of rice and uptake and speciation of arsenic. Treatments of the greenhouse experiment consisted of two phosphate doses and seven different arsenate concentrations ranging from 0 to 8 mg of As L -1 applied regularly throughout the 170)day post-transplantation growing period until plants were ready for harvesting. Increasing the concentration of arsenate in irrigation water significantly decreased plant height, grain yield, the number of filled grains, grain weight, and root biomass, while the arsenic concentrations in root, straw, and rice husk increased significantly. Concentrations of arsenic in rice grain did not exceed the food hygiene concentration limit (1.0 mg of As kg -1 dry weight). The concentrations of arsenic in rice straw (up to 91.8 mg kg -1 for the highest As treatment) were of the same order of magnitude as root arsenic concentrations (up to 107.5 mg kg -1 ), suggesting that arsenic can be readily translocated to the shoot. While not covered by food hygiene regulations, rice straw is used as cattle feed in many countries including Bangladesh. The high arsenic concentrations may have the potential for adverse health effects on the cattle and an increase of arsenic exposure in humans via the plant-animal-human pathway. Arsenic concentrations in rice plant parts except husk were not affected by application of phosphate. As the concentration of arsenic in the rice grain was low, arsenic speciation was performed only on rice straw to predict the risk associated with feeding contaminated straw to the cattle. Speciation of arsenic in tissues (using HPLC-ICP-MS) revealed that the predominant species present in straw was arsenate followed by arsenite and dimethylarsinic acid (DMAA). As DMAA is only present at low concentrations, it is unlikely this will greatly alter the toxicity of arsenic present in rice.
An Overview of Arsenic Dynamics in Lowland Rice Ecosystem
Arsenic naturally occurs in many environmental media, such as rocks, soil, sediments, and surface/groundwater and it can further be released into the aquatic and terrestrial ecosystem via natural and anthropogenic activities. Amongst the main contributing sources of As contamination of soil and water are geologic origin, pyritic mining, agriculture and coal burning. Soils contain both organic and inorganic arsenic species. Inorganic As species are more toxic to living organisms than organic forms. The majority of As in aerated soils exists as H2AsO4− (acid soils) or HAsO42− (neutral and basic). However, H3AsO3 is the predominant species in anaerobic soils, where arsenic availability is higher and As (III) is more weakly retained in the soil matrix than As(V). The availability of As in soils is usually driven by multiple factors and processes such as the presence of Fe-oxides and/or phosphorus, (co)precipitation in salts, pH, organic matter, clay content, rainfall amount, etc. The available and most labile As fraction can potentially be taken up by plant roots, although the concentration of this fraction is usually low. The status of current scientific knowledge allows us to manage as contamination in the soil-plant system and to mitigate arsenic’s effects. Hence it is imperative to understand the mechanisms of As uptake and translocation by rice and the present paper focuses on the journey of As from soil to human through the rice grains.
Scientific Reports
Environmental contamination of arsenic (As) and its accumulation in rice (Oryza sativa L.) is of serious human health concern. In planta speciation of As is an important tool to understand As metabolism in plants. In the present study, we investigated root to shoot As translocation and speciation in rice exposed to inorganic and methylated As. Arsenate (As V) and methylarsonate (MA V) were efficiently reduced to arsenite (As III) and MA III , respectively in rice root and shoot but no trivalent form of dimethylarsinate (DMA V) was detected. Further, up to 48 and 83% of root As in As V and MA V exposed plants, respectively were complexed with various thiols showing up to 20 and 16 As species, respectively. Several mixed As-and MA-complexes with hydroxymethyl-phytochelatin, DesGlyphytochelatin, hydroxymethyl-GSH and cysteine were identified in rice. Despite high complexation in roots, more As was translocated to shoots in MA V exposed plants than As V , with shoot/root As transfer factor being in order DMA V > MA V > As V. Moreover, in shoots 78% MA III and 71% As III were present as weakly bound species which is alarming, as MA III has been found to be more cytotoxic than As III for human and it could also be an important factor inducing straighthead (spikelet sterility disorder) in rice. Arsenic (As) is ubiquitously present, considered as a non-essential metalloid for plants and animals, and poses serious health hazards to humans. High levels of As in soil and water have been reported around the world through geothermal, mining and industrial activities, agricultural applications and contaminated ground water 1,2. Ground water of many countries, particularly in the Indian subcontinent, are naturally highly enriched with As and posing toxicity through drinking water and food chain contamination 3,4. Agricultural fields are the net sink for thousands of tons of As being transferred each year through contaminated irrigation water in these areas 5,6. The typical As concentration in soil solution of paddy fields varies from 0.01 to 3 μ M, however, as high as 33 μ M As has been reported in a paddy field irrigated with As-laden ground water 7,8. Further, a significant yield loss has been reported in the crops grown in As contaminated areas 8. Thus, a threat to the sustainability of food production has been recognized as the other side of the As calamity 8,9. Understanding the mechanism of As toxicity in plants is crucial to find a sustainable solution to the problem. Arsenic exists in various chemical forms in the environment, which differ considerably in plant uptake, mobility and toxicity. Thus, speciation of As in various plant parts is an important tool to understand the in planta transformation and metabolism of various As species. Inorganic arsenate [HAsO 4 2− or As V ] and arsenite [H 2 AsO 3 − or As III ] are the predominant species in water and soil, however, in soil considerable amount of methylated arsenic species [methylarsonic acid; MA V and dimethylarsinic acid; DMA V ] may also be present due to microbial action 10-13 or due to past uses of methylated As compounds (sodium salt of MA V and DMA V or cacodylic acid) as pesticides and herbicides 4,14. Arsenate is taken up by the plants through phosphate transporters 15 , while As III is taken up by nodulin26-like intrinsic (NIPs) aquaporin channels, along with neutral solutes like glycerol, ammonia and silicic acid 16. The rice aquaporin Lsi1 also