Concentration In Rice Grains Research Articles

Copper and ectopic expression of the Arabidopsis transport protein COPT1 alter iron homeostasis in rice (Oryza sativa L.).

Copper deficiency and excess differentially affect iron homeostasis in rice and overexpression of the Arabidopsis high-affinity copper transporter COPT1 slightly increases endogenous iron concentration in rice grains. Higher plants have developed sophisticated mechanisms to efficiently acquire and use micronutrients such as copper and iron. However, the molecular mechanisms underlying the interaction between both metals remain poorly understood. In the present work, we study the effects produced on iron homeostasis by a wide range of copper concentrations in the growth media and by altered copper transport in Oryza sativa plants. Gene expression profiles in rice seedlings grown under copper excess show an altered expression of genes involved in iron homeostasis compared to standard control conditions. Thus, ferritin OsFER2 and ferredoxin OsFd1 mRNAs are down-regulated whereas the transcriptional iron regulator OsIRO2 and the nicotianamine synthase OsNAS2 mRNAs rise under copper excess. As expected, the expression of OsCOPT1, which encodes a high-affinity copper transport protein, as well as other copper-deficiency markers are down-regulated by copper. Furthermore, we show that Arabidopsis COPT1 overexpression (C1 OE ) in rice causes root shortening in high copper conditions and under iron deficiency. C1 OE rice plants modify the expression of the putative iron-sensing factors OsHRZ1 and OsHRZ2 and enhance the expression of OsIRO2 under copper excess, which suggests a role of copper transport in iron signaling. Importantly, the C1 OE rice plants grown on soil contain higher endogenous iron concentration than wild-type plants in both brown and white grains. Collectively, these results highlight the effects of rice copper status on iron homeostasis, which should be considered to obtain crops with optimized nutrient concentrations in edible parts.

Safe limit of arsenic in soil in relation to dietary exposure of arsenicosis patients from Malda district, West Bengal- A case study

Safe limit of arsenic in soil in relation to dietary exposure of arsenicosis patients was established in Malda district of West Bengal. Out of 182 participants examined, 80 (43.9%) participants showed clinical features of arsenicosis, characterized by arsenical skin lesion (pigmentation and keratosis), while 102 participants did not have any such lesion (control). Experimental results of the twenty eight soils (own field) of the participants showed the mean Olsen extractable and total arsenic concentration of 0.206 and 6.70mgkg−1, respectively. Arsenic concentration in rice grain ranged from 2.00 to 1260μgkg−1 with the mean value of 146μgkg−1. The hazard quotient (HQ) for intake of As by human through consumption of rice varied from 0.03 to 3.52. HQ exceeds 1.0 for drinking water and rice grain grown in the study area in many cases. As high as 77.6% variation in As content in rice grain could be explained by the solubility-free ion activity model. Toxic limit of extractable As in soil for rice in relation to soil properties and human health hazard, associated with consumption of rice grain by human, was established. For example, the permissible limit of Olsen extractable As in soil would be 0.43mgkg−1 for rice cultivation, if soil pH and organic carbon content were 7.5% and 0.50%, respectively. However, the critical limit of Olsen extractable As in soil would be 0.54mgkg−1, if soil pH and organic carbon were 8.5% and 0.75%, respectively. The conceptual framework of fixing the toxic limit of arsenic in soils with respect to soil properties and human health under modeling-framework was established.

Heavy metal accumulation in rice (Oryza sativa) near electronic waste dumps and related human health risk assessment

ABSTRACTThis research was conducted to assess heavy metal contamination in the environment and within Oryza sativa. The translocation factors (TFs) and bioaccumulation factors (BAFs) for heavy metals in O. sativa and estimated daily intake (EDI) and health risk index (HRI) were measured. The samples were analyzed for heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES). Pb and Cr concentrations in water samples within and near the electronic-waste dumping area exceeded water quality standards for surface water sources from the Pollution Control Department in the Ministry of Natural Resources and Environment of Thailand (PCD). The Pb concentration in soil samples within the area also exceeded soil quality standards for habitat and agriculture from PCD. Most of the metals were highly concentrated in roots, except for Mn which has the highest concentration in leaves. Pb concentrations in rice grains exceeded the FAO/WHO standard (0.2 mg/kg). The average TF values for heavy metals from the soil to roots, roots to stems, stems to leaves, and stems to grains were Mn > Pb > Ni > Cr, Mn > Cr > Ni > Pb, Ni > Pb > Mn > Cr, and Pb > Ni > Cr > Mn, respectively. The average BAF values in O. sativa were Mn > Ni > Pb > Cr. The EDI for Cr, Pb, Mn, and Ni via O. sativa consumption were 6.19, 6.02, 370.57, and 3.80 µg/kg/day, respectively. The HRI for Cr, Pb, Mn, and Ni via O. sativa consumption were 0.30, 1.50, 2.60, and 0.002, respectively.

Total As and As Speciation in Italian Rice as Related to Producing Areas and Paddy Soils Properties.

Rice and rice-based foodstuffs are important pathways for inorganic As dietary intake. This work shows a detailed picture of As content and speciation in Italian rice, which contributes to more than one-half of the European production, and addresses the role of soil chemistry and agronomic management on As concentration in rice grain, in view of ameliorative strategies. The mean total As content in Italian white rice was 155 ± 65 μg kg-1 with significant differences among producing areas, while the mean inorganic As was 102 ± 26 μg kg-1, largely below the E.U. limit of 200 μg kg-1 for white rice, although part of the production would not be suitable for baby food production, which requires less than 100 μg kg-1 of inorganic As. The differences in As content and speciation in rice among the studied areas resulted from the complex interactions of soil, plant, and anthropic factors. Among others, Si nutrition seemed to play a key role in regulating As transfer from soil to plant.

The influence of atmospheric Hg on Hg contaminations in rice and paddy soil in the Xunyang Hg mining district, China

To date, the Xunyang mercury (Hg) mining district is the only ongoing large-scale Hg mining district in China. To understand the influence of Hg contamination mode from the Hg mining and smelting activities, 27 sampling sites in the Xunyang Hg mining district were chosen in this study. Total gaseous mercury (TGM) in ambient air was measured using a Lumex-RA915 automatic Hg analyzer in 2011. Rice samples and soil samples from rhizosphere were collected systematically and simultaneously. Total Hg (THg) and methylmercury (MeHg) concentrations in rice grain and soil samples and Hg speciation with modified sequential selective extractions were measured. The local environment was seriously polluted with Hg. The TGM (302 ± 376 ng·m−3, ranging from 24 to 2220 ng·m−3) in the local ambient air, THg (28 ± 30 mg·kg−1, ranging from 0.31 to 121 mg·kg−1) and MeHg (2.3 ± 1.9 μg·kg−1, ranging from 0.24 to 8.9 μg·kg−1) in soil samples were at the sample level with Hg contaminated area. The THg concentration (26 ± 16 μg·kg−1 ranging from 4.5 to 71 μg·kg−1) in most of the rice grain samples clearly exceeds the threshold level (20 μg·kg−1) in the Chinese national guidelines for cereals (NY 861-2004). The inorganic mercury (IHg) (9.1 ± 5.6 μg·kg−1, ranging from 1.2 to 24 μg·kg−1) and MeHg (14 ± 9.8 μg·kg−1, ranging from 2.1 to 59 μg·kg−1) concentration in rice grain samples were at the same level with Hg contaminated area. The main species of Hg in paddy soils reveal strong complex Hg and residue Hg. According to the correlation analysis, a Hg pollution mode from local Hg mining and smelting was hypothesized, including Hg emission, transportation, methylation, and uptake process.

Cadmium transfer from contaminated soils to the human body through rice consumption in southern Jiangsu Province, China.

Consumption of crops grown in cadmium-contaminated soils is an important Cd exposure route to humans. The present study utilizes statistical analysis and in vitro digestion experiments to uncover the transfer processes of Cd from soils to the human body through rice consumption. Here, a model was created to predict the levels of bioaccessible Cd in rice grains using phytoavailable Cd quantities in the soil. During the in vitro digestion, a relatively constant ratio between the total and bioaccessible Cd in rice was observed. About 14.89% of Cd in soils was found to be transferred into rice grains and up to 3.19% could be transferred from rice grains to the human body. This model was able to sufficiently predict rice grain cadmium concentrations based on CaCl2 extracted zinc and cadmium concentrations in soils (R2 = 0.862). The bioaccessible Cd concentration in rice grains was also able to be predicted using CaCl2 extracted cadmium from soil (R2 = 0.892). The models established in this study demonstrated that CaCl2 is a suitable indicator of total rice Cd concentrations and bioaccessible rice grain Cd concentrations. The chain model approach proposed in this study can be used for the fast and accurate evaluation of human Cd exposure through rice consumption based on the soil conditions in contaminated regions.

Rhizospheric iron and arsenic bacteria affected by water regime: Implications for metalloid uptake by rice

Rice is characterized by high levels of arsenic accumulation, even if cultivated in non-contaminated soils. Given the limits for arsenic concentration in rice grain recently established by the European Community, it is essential to understand the mechanisms and find solutions to this issue. Arsenic bioavailability is strictly related to water management of the rice paddy as well as to iron- and arsenic-cycling bacterial populations inhabiting the rice rhizosphere.To evaluate the effect of different agronomic conditions on the root-soil microbiota involved in arsenic mobilization, rice plants were grown in macrocosms containing non contaminated field soil under either continuous flooding, aerobic rice regime or continuous flooding with a 14 day-period of drainage before flowering. Specific groups of iron- and arsenic-cycling bacteria were assessed by real time quantitative PCR and fluorescence in situ hybridization.Continuous flooding led to the release of arsenate and iron in soil solution and produced rice grains with arsenite and organic arsenic above the recently established limits, contrary to the other agronomic conditions.Iron-reducing bacteria affiliated to the family Geobacteraceae significantly increased under continuous flooding in rhizosphere soil, in concomitance to arsenate dissolution from iron minerals. The 14 day-period of drainage before flowering allowed the recycling of iron, with the increase of Gallionella-like iron-oxidizing bacteria. This phenomenon likely influenced the decrease of arsenic translocation in rice grains.Regardless of the water regime, genes for arsenite oxidation (aioA) were the most abundant arsenic-processing genes, explaining the presence of arsenate in soil solution. The presence of arsenite and organic arsenic in rice grains produced under continuous flooding might be related to the retrieval of genes for arsenate reduction (arsC) and for arsenite methylation (arsM) in the proximity of the roots.These outcomes indicate a potential active role of rhizospheric iron- and arsenic-cycling bacteria in determining arsenic accumulation in rice grains from plants cultivated under continuous flooding, even in soil with a low arsenic content.

Impacts of Steel-Slag-Based Silicate Fertilizer on Soil Acidity and Silicon Availability and Metals-Immobilization in a Paddy Soil.

Slag-based silicate fertilizer has been widely used to improve soil silicon- availability and crop productivity. A consecutive early rice-late rice rotation experiment was conducted to test the impacts of steel slag on soil pH, silicon availability, rice growth and metals-immobilization in paddy soil. Our results show that application of slag at a rate above higher or equal to 1 600 mg plant-available SiO2 per kg soil increased soil pH, dry weight of rice straw and grain, plant-available Si concentration and Si concentration in rice shoots compared with the control treatment. No significant accumulation of total cadmium (Cd) and lead (Pb) was noted in soil; rather, the exchangeable fraction of Cd significantly decreased. The cadmium concentrations in rice grains decreased significantly compared with the control treatment. In conclusion, application of steel slag reduced soil acidity, increased plant–availability of silicon, promoted rice growth and inhibited Cd transport to rice grain in the soil-plant system.

Coated urea enhances iron and zinc concentrations in rice grain under different cultivation methods

ABSTRACTIn order to assess changes of iron (Fe) and zinc (Zn) in rice grain as affected by polyester resin coated urea (PCU) under conventional flooding cultivation (CFC) and plastic film mulching cultivation (PFMC), using prilled urea (PU) as a contrast, a three year field experiment was conducted in Central Zhejiang Province, E China, from 2008 to 2010. The mean annual Fe concentration under PFMC in brown rice was increased by 9.3%, 9.0% and 16.2%; Zn was improved by 21.8%, 16.9% and 12.9%, during 2008, 2009 and 2010, respectively. Compared PCU to PU, Fe concentration in brown rice was improved by 7.3%, 10.1% and 17.9%; Zn concentration in brown rice was improved by 14.8%, 11.3% and 8.1%, during 2008, 2009 and 2010, respectively. Non-flooded PFMC decreased soil organic matter, soil nitrogen (N) and potassium (K) compared to CFC, which suggested that long term PFMC will make soil quality maintenance difficult.

The respective effects of soil heavy metal fractions by sequential extraction procedure and soil properties on the accumulation of heavy metals in rice grains and brassicas.

This study was carried out to examine heavy metal accumulation in rice grains and brassicas and to identify the different controls, such as soil properties and soil heavy metal fractions obtained by the Community Bureau of Reference (BCR) sequential extraction, in their accumulation. In Guangdong Province, South China, rice grain and brassica samples, along with their rhizospheric soil, were collected from fields on the basis of distance downstream from electroplating factories, whose wastewater was used for irrigation. The results showed that long-term irrigation using the electroplating effluent has not only enriched the rhizospheric soil with Cd, Cr, Cu, and Zn but has also increased their mobility and bioavailability. The average concentrations of Cd and Cr in rice grains and brassicas from closest to the electroplating factories were significantly higher than those from the control areas. Results from hybrid redundancy analysis (hRDA) and redundancy analysis (RDA) showed that the BCR fractions of soil heavy metals could explain 29.0 and 46.5% of total eigenvalue for heavy metal concentrations in rice grains and brassicas, respectively, while soil properties could only explain 11.1 and 33.4%, respectively. This indicated that heavy metal fractions exerted more control upon their concentrations in rice grains and brassicas than soil properties. In terms of metal interaction, an increase of residual Zn in paddy soil or a decrease of acid soluble Cd in the brassica soil could enhance the accumulation of Cd, Cu, Cr, and Pb in both rice grains and brassicas, respectively, while the reducible or oxidizable Cd in soil could enhance the plants' accumulation of Cr and Pb. The RDA showed an inhibition effect of sand content and CFO on the accumulation of heavy metals in rice grains and brassicas. Moreover, multiple stepwise linear regression could offer prediction for Cd, Cu, Cr, and Zn concentrations in the two crops by soil heavy metal fractions and soil properties.

Identification of introgression lines of Oryza glaberrima Steud. with high mineral content in grains

ABSTRACTMineral concentrations in cereals are crucial for human health, especially for people who consume cereals as a subsistence diet. Although rice (Oryza sativa L.) is one of most important staple crops in the world, starch constitutes a large portion of its grains, and mineral concentrations are lower than in other staple crops. One solution is the improvement of mineral concentrations in rice grains through biofortification, and this approach requires investigation of genetic resources that confer high mineral concentrations to rice grains. In the present study, we performed 2 years of field experiments, in 2012 and 2013, and determined sodium (Na), magnesium (Mg), phosphorus (P), potassium (K), calcium (Ca), boron (B), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn) and molybdenum (Mo) concentrations in the rice grains of 40 introgression lines derived from a cross between a japonica cultivar, Taichung 65 (T65), and African rice, Oryza glaberrima Steud. Substantial variation in mineral concentrations was observed among the 40 introgression lines. We selected several elite lines that had significantly higher concentrations of minerals, including Fe, Cu, Zn, Mo, Mg, P and Ca than the cultivated rice T65. These lines could be novel potential materials for breeding programs for biofortification and provide us with positional information for the candidate loci in the O. glaberrima genome responsible for high mineral concentrations in rice grains.

Arsenic in rice agrosystems (water, soil and rice plants) in Guayas and Los Ríos provinces, Ecuador

Geogenic arsenic (As) can accumulate and reach high concentrations in rice grains, thus representing a potential threat to human health. Ecuador is one of the main consumers of rice in South America. However, there is no information available about the concentrations of As in rice agrosystems, although some water bodies are known to contain high levels of the element. We carried out extensive sampling of water, soil, rice plants and commercial rice (obtained from local markets). Water samples were analysed to determine physico-chemical properties and concentrations of dissolved arsenic. Soil samples were analysed to determine total organic C, texture, total Fe and amorphous Fe oxyhydroxides (FeOx), total arsenic (tAs) and the bioavailable fraction (AsMe). The different plant parts were analysed separately to determine total (tAs), inorganic (iAs) and organic arsenic (oAs). Low concentrations of arsenic were found in samples of water (generally <10μgl−1) and soil (4.48±3mgkg−1). The tAs in the rice grains was within the usual range (0.042–0.125mgkg−1 dry weight, d.w.) and was significantly lower than in leaves (0.123–0.286mgkg−1 d.w.) and stems (0.091–0.201mgkg−1 d.w.). The FeOx and tAs and also AsMe in flood water were negatively correlated with tAs in the plants. However, the concentrations of As in stems and leaves were linearly correlated with tAs in the soil and flood water. The relationship between tAs and arsenic in the grain fitted a logarithmic function, as did that between tAs in the grain and the stem. The findings seem to indicate that high concentrations of arsenic in the environment (soil or water) or in the rice stem do not necessarily imply accumulation of the element in the grain. The iAs form was dominant (>80%) in all parts of the rice plants.

Cadmium Accumulation Characteristic in a Soil-rice System in Zhejiang Province, China

Cadmium (Cd) pollution of rice grain or soil is of increasing concern. This study investigates the concentrations of Cd in soil-rice system in parts area of Zhejiang province and analysis the effects of soil pH and organic matter content on the available Cd concentration in soil and the Cd accumulation of rice grain. The results showed that Cd concentrations in 90 rice grain samples range from 0.01 to 0.31 mg/kg, with an average of 0.1 mg/kg. There is high Cd accumulation in soil that 40% of soil samples were polluted by Cd. The available Cd concentrations in soils had a range of 0.01-0.25 mg/kg, with an average of 0.10 mg/kg. The total Cd concentrations in soil were not the uniquely determined factor for the Cd accumulation of rice grain, Cd concentrations in rice grain were also significantly positive correlated with the available Cd concentrations in soil. The soil pH value and SOM also negatively correlated with available Cd concentrations in soils and Cd concentration in corresponding rice grain. The results indicated the variations of Cd concentration in rice grain were related to Cd concentrations in corresponding soils. Also, soil pH and organic matter content influence the Cd concentrations in soils and affected Cd absorption in rice.

Modest amendment of sewage sludge biochar to reduce the accumulation of cadmium into rice(Oryza sativa L.): A field study

Much research has considered the influence of biochars on the availability and phytoaccumulation of potentially toxic elements (PTEs) from soil. However, the vast majority of these studies use, what are arguably, unrealistic and unpractical amounts of biochar (10, 50 and even up to 100 t/ha). To offer a more realistic insight into the influence of biochar on PTE partitioning and phytoaccumulation, a field study, using modest rates of biochar application (1.5, 3.0 t/ha), was undertaken. Specifically, the research investigated the influence of sewage sludge biochar (SSBC) on the accumulation of Cd into rice (Oryza sativa L.) grown in Cd contaminated (0.82 ± 0.07 mg/kg) paddy soil. Results indicated, Cd concentrations in rice grains to significantly (p < 0.05) decrease from 1.35 ± 0.09 mg/kg in the control to 0.82 ± 0.07 mg/kg and 0.80 ± 0.21 mg/kg in the 1.5 t/ha and 3.0 t/ha treatments, respectively. Accordingly, the hazardous quotient (HQ) indices for Cd, associated with rice grain consumption, were also reduced by ∼40%. SSBC amendment significantly (p < 0.05) increased grain yields from 1.90 ± 0.08 g/plant in the control to 2.17 ± 0.30 g/plant and 3.40 ± 0.27 g/plant in the 1.5 t/ha and 3.0 t/ha treatments, respectively. Thus, the amendment of SSBC to contaminated paddy soils, even at low application rates, could be an effective approach to mitigate Cd accumulation into rice plants, to improve rice grain yields, and to thereby improve food security and protect public health.

Effect of different amendments on rice (Oryza sativa L.) growth, yield, nutrient uptake and grain quality in Ni-contaminated soil.

Rice ( Oryza sativa L.) is one of the main staple food crops which is inherently low in micronutrients, especially iron (Fe), and can lead to severe Fe deficiency in populations having higher consumption of rice. Soils polluted with nickel (Ni) can cause toxicity to rice and decreased Fe uptake by rice plants. We investigated the potential role of biochar (BC) and gravel sludge (GS), alone and in combination, forin situ immobilization of Ni in an industrially Ni-contaminated soil at original and sulfur-amended altered soil pH. Our further aim was to increase Fe bioavailability to rice plants by the exogenous application of ferrous sulfate to the Ni-immobilized soil. Application of the mixture of both amendments reduced grain Ni concentration, phytate, Phytate/Fe, Phyt/Zn molar ratios, and soil DTPA-extractable Ni. In addition,the amendment mixture increased 70% Fe and 229% ferritin concentrations in rice grains grown in the soil at original pH. The Fe and ferritin concentrations in S-treated soil was increased up to 113 and 383% relative to controlrespectively. This enhanced Fe concentration and corresponding ferritin in rice grains can be attributed to Ni/Fe antagonism where Ni has been immobilized by GS and BC mixture. This proposed technique can be used to enhancegrowth, yield, and Fe biofortification in rice by reducing soil pH while in parallel in situ immobilizing Ni in polluted soil.

Optimal Soil Eh, pH, and Water Management for Simultaneously Minimizing Arsenic and Cadmium Concentrations in Rice Grains.

Arsenic (As) and cadmium (Cd) concentrations in rice grains are a human health concern. We conducted field experiments to investigate optimal conditions of Eh and pH in soil for simultaneously decreasing As and Cd accumulation in rice. Water managements in the experiments, which included continuous flooding and intermittent irrigation with different intervals after midseason drainage, exerted striking effects on the dissolved As and Cd concentrations in soil through changes in Eh, pH, and dissolved Fe(II) concentrations in the soil. Intermittent irrigation with three-day flooding and five-day drainage was found to be effective for simultaneously decreasing the accumulation of As and Cd in grain. The grain As and Cd concentrations were, respectively, linearly related to the average dissolved As and Cd concentrations during the 3 weeks after heading. We propose a new indicator for expressing the degree to which a decrease in the dissolved As or Cd concentration is compromised by the increase in the other. For minimizing the trade-off relationship between As and Cd in rice grains in the field investigated, water management strategies should target the realization of optimal soil Eh of -73 mV and pH of 6.2 during the 3 weeks after heading.

Low-cadmium rice (Oryza sativa L.) cultivar can simultaneously reduce arsenic and cadmium concentrations in rice grains

ABSTRACTIn previous research, we produced a japonica rice (Oryza sativa L.) cultivar (‘Koshihikari Kan No. 1’) with nearly undetectable levels of cadmium (Cd) in the grains. In this study, we hypothesized that growing this cultivar aerobically would simultaneously reduce arsenic (As) and Cd concentrations in the grains. We grew this cultivar and ‘Koshihikari’, its parent, in paddy fields with different soil properties under three water regimes: flooded conditions (FLD), alternate wetting and drying conditions (AWD) and water-saving conditions (WAS). FLD for several weeks before and after heading significantly increased the grain As concentration in both cultivars. AWD, with the soil re-flooded just after disappearance of the ponded water, reduced grain As concentrations by an average of 27% relative to FLD for both cultivars. WAS, with irrigation after drying of the soil surface, decreased grain As concentrations by an average of 43.1% for ‘Koshihikari Kan No. 1’ and 48.2% for ‘Koshihikari’ compared to FLD. Although AWD and WAS remarkably increased grain Cd concentrations in ‘Koshihikari’, ‘Koshihikari Kan No. 1’ had nearly undetectable levels of grain Cd in all treatments. Compared with ‘Koshihikari’ in FLD, grain yield of ‘Koshihikari Kan No. 1’ and ‘Koshihikari’ decreased by averages of 2% for AWD and 4 to 6% for WAS. In addition, WAS tended to decrease grain quality slightly for both cultivars. Although aerobic conditions such as WAS have somewhat adverse effects on grain yield and quality, growing the low-Cd cultivar aerobically is the most practical way to simultaneously reduce Cd and As contents in the rice grains.

Spatial Variability of Rice Grain Arsenic in Confined and Unconfined Basins of Ganges River Floodplain Soils of Bangladesh

Arsenic (As) accumulates in rice grain from contaminated irrigation water and soils may vary with the land types and water receiving basins. Two confined and one unconfined basins comprised of different land types in the As contaminated Ganges River Floodplain soils of Faridpur district of Bangladesh were selected to assess the contribution of different land types on spatial distribution of As uptake by rice grain. Sites in Faridpur Sadar and Madhukhali upazilas were confined basins, while a third site in Boalmari upazila was an unconfined basin connected to a river. Each site consisted of a mosaic of between 16-31 shallow tube well (STW) irrigation command areas with water As concentrations ranging from about 20 to 170 ?g-l in Faridpur and Boalmari sites and 20-110 ?g-l in Madhukhali site. Soil arsenic concentrations ranged from about 4-42, 5-31 and 5-29 mg kg-1 in Madhukhali, Faridpur Sadar and Boalmari, respectively, while the resultant rice grain As were 0.22 - 0.69, 0.095 – 0.751 and 0.030 – 0.92 mg kg-1, respectively. Arsenic concentrations in rice grain of different sites were in the order of Madhukhal&gt;Faridpur Sadar&gt;Boalmari basin. Arsenic accumulated high in the confined basins because of its less mobilization while more mobilization and loss of As in the open unconfined basin was obvious which materialized in the rice grain arsenic of the corresponding study sites.J. Environ. Sci. &amp; Natural Resources, 8(2): 51-55 2015

Zinc Concentration in Rice (Oryza sativa L.) Grains and Allocation in Plants as Affected by Different Zinc Fertilization Strategies

ABSTRACTConcern over the food chain transfer of zinc (Zn) is increasing because of its importance in human health. A field experiment was conducted on a low Zn soil to determine the effect of different Zn fertilization strategies on grain Zn concentration and Zn allocation in different plant tissues of rice. Six treatments were used: (1) no Zn fertilization; (2) soil fertilization at transplanting; (3) Zn soil fertilization at transplanting and flowering; (4) foliar application during grain filling; (5) foliar applications during tillering, flowering, and grain filling; and (6) combination of treatments 3 and 5. Zn fertilization significantly increased Zn concentration in brown rice. The largest effect on grain Zn was observed by combination of soil and foliar applications. The increase in brown rice was much smaller (20%) than the increase in the vegetative parts (100%), indicating that grain Zn concentration of rice is not strongly increased by Zn fertilization. More increased Zn by Zn fertilization was allocated into straw not into grain. From the perspective of human nutrition, it seems that there is too little scope to enhance Zn concentration in rice by fertilization alone. the major bottleneck to increase Zn concentration in rice grain seems to be internal translocation/retranslocation of Zn from shoot to panicle or from rachis to grain, rather than root uptake of Zn from the soil.

Subcellular Distribution of Cadmium in Two Paddy Rice Varieties with Different Cooking Methods

Cadmium (Cd) is a non-essential element that is highly mobile within organisms where, following plant uptake, subcellular distribution plays an important role in plant tolerance and detoxification. Cd uptake and subcellular distribution were studied in two paddy rice varieties (Japonica and Indica) hydroponically cultivated in Cd-containing solutions. Japonica rice grains containing Cd were also collected from a Cd-contaminated site and subjected to various cooking treatments (boiled, stir-fried, steamed, and control) to determine the influence of cooking method on the subcellular distribution of Cd. Cd treatment inhibited both shoot height and root length, especially in Japonica, where for the same Cd treatment, Japonica accumulated more Cd in roots and shoots than Indica. Most of the accumulated Cd (92% - 99%) was bound to the cell wall and vacuoles, and decreased in the order: soluble fraction (Fs) > cell wall fraction (Fcw) > organelle fraction (Fco). Subcellular Cd concentrations in rice grains were significantly affected by cooking treatment. The proportion of trophically available Cd decreased with increase in cooking duration and temperature, indicating that consuming steamed and stir-fried rice had a lower Cd exposure risk than consuming boiled rice.