Effects of Arsenic and Their Mitigation in Plants (original) (raw)
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.
Metabolic Responses to Arsenite in Rice Seedlings that Differed in Grain Arsenic Concentration
Crop Science, 2017
A rsenic (As) occurs naturally in air, water, and soil and, being ubiquitous in the environment, is also present in all edible and nonedible plant tissues. Arsenic ingestion can have both acute and long-term effects, making it a poison and a well-known carcinogen. Rice (Oryza sativa L.) has a propensity to uptake more As than other plants because cultivation commonly occurs in flooded soils where anoxic conditions make As more bioavailable. Some geographic regions have notably high concentrations of As in their drinking and irrigation water supplies, which inadvertently contaminate staple food crops such as rice . Under flooded field conditions, anoxic conditions reduce inorganic As(V) to As(III) and soil microorganisms methylate As , converting inorganic As into organic As. Both the chemical reduction and the conversion
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.