Addition Of Se Research Articles

Effects of root iron plaque on selenite and selenate dynamics in rhizosphere and uptake by rice (Oryza sativa)

Iron plaque commonly forms on rice root surfaces under flooded conditions. However, little is known about the role of iron plaque in Se movement from rhizosphere to plant. A compartmented soil-quartz sand culture system was applied to investigate the effects of iron plaque on Se uptake by rice and document Se speciation dynamics in soil solution under flooded conditions. Rice seedlings were planted in a nylon bag containing sand and surrounded by soil amended with Se combined at rates of 0 or 0.5 mg of Se kg−1 of soil in the form of selenate or selenite. Plants were harvested at seedling stage and at maturity. Fe and Se concentrations in soil solution, in DCB extracts and Se concentrations in rice roots and shoots were determined. A visible reddish coating on root surfaces could be observed when sampled at the seedling stage and at maturity. Iron plaque on root surfaces greatly influenced Se uptake and had a higher affinity for selenite. The distribution of Se in different components of rice seedlings followed iron plaque > shoot > root, while it followed shoot > root > iron plaque at maturity. The addition of Se initially increased the soluble Se concentrations, and selenate was the main species in soil solution. Iron plaque greatly influenced Se uptake and might act as a pool to Se uptake during rice growth. Selenate or selenite addition to paddy soil showed the same effect in increasing Se concentrations in rice grain.

Efficacy of supplementation of selected medicinal mushrooms with inorganic selenium salts

The aim of the study was to evaluate the possibility of supplementation with inorganic forms of selenium (Na2SeO4 and Na2SeO3) in concentrations of 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.5 mM of three medicinal mushroom species: Agrocybe aegerita, Hericium erinaceus and Ganoderma lucidum. Tested mushroom species grew in Se additions of 0–0.6 mM (A. aegerita and H. erinaceus), while growth of G. lucidum bodies was observed for 0–0.8 mM. For the latter mushroom species, the total Se content was the highest. Content of Seorg was diverse; for control bodies it was the highest for G. lucidum (only organic forms were present), lower for A. aegerita (84% organic forms) and the lowest for H. erinaceus (56% organic forms). Accumulation of Se(IV) was generally significantly higher than Se(VI) for all tested mushroom species. There was no significant decrease of A. aegerita or G. lucidum biomass with the exception of G. lucidum bodies growing under 0.8 mM of Se species addition (15.51 ± 6.53 g). Biomass of H. erinaceus bodies was the highest under 0.2 (197.04 ± 8.73 g), control (191.80 ± 6.06 g) and 0.1 mM (185.04 ± 8.73 g) of both inorganic salts. The addition to the medium of Se salts brought about macroscopic changes in the fruiting bodies of the examined mushrooms. Concentrations exceeding 0.4 mM caused diminution of carpophores or even their total absence. In addition, colour changes of fruiting bodies were also recorded. At Se concentrations of 0.4 and 0.6 mM, A. aegerita fruiting bodies were distinctly lighter and those of H. erinaceus changed colour from purely white to white-pink.

Influence of Increased Dietary Selenium on Glutathione Peroxidase Activity and Glutathione Concentration in Erythrocytes of Lactating Sows

Abstract We studied the influence of different selenium (Se) levels on some parameters of the antioxidant potential of lactating sows. The experiment involved 15 sows of the Large White breed divided into 3 equal groups. The addition of Se (from Se-enriched yeast) amounted to 0.0, 0.25 and 0.50 mg per kg of diet in the control, Se1 and Se2 groups, respectively. Erythrocyte Se concentration, glutathione peroxidase (GPx) activity and reduced/oxygenated glutathione ratio were measured as some of the indicators of the sow’s antioxidant status. Supplementation of Se at 0.25 mg/kg of diet increased Se concentration (by 50.0%; P<0.01), GPx activity (by 17.0%: P<0.05) and reduced/ oxygenated glutathione ratio (by 29.7%; P<0.05). Addition of Se at 0.50 mg/kg of diet increased Se concentration (by 63.6%; P<0.01), GPx activity (by 34.7%; P<0.01) and reduced/oxygenated glutathione ratio (by 64.0%; P<0.01). A significant relationship (P<0.01) was found between the Se concentrations and activity of GPx in erythrocytes from sows in the Se1 and Se2 groups (r=0.76 and 0.77, respectively). Percentage of piglets weaned/born was higher (P>0.05) in the Se2 than in the Se1 and control groups. In summary, addition of 0.25 or 0.50 mg Se/kg of diet can improve antioxidant status of lactating sows, but addition of 0.25 mg Se/kg may be also sufficient.

Effect of selenium on CO<sub>2</sub> and NO<sub>3</sub><sup>-</sup> assimilation under low and adequate nitrogen supply in wheat (Triticum aestivum L.)

In order to study the mechanisms of Se-mediated growth improvement as related to carbon (C) and nitrogen (N) metabolism, wheat plants were cultivated hydroponically with adequate (4 mM, Na) or low (1 mM, Nd) N supply and treated with 10 and 50 μM Na2SeO4 for six weeks. The Se supplementation enhanced plant biomass; it was significant for shoots of Na plants at 50 μM Se. Chlorophyll fluorescence parameters were significantly lowered under Nd conditions but restored completely by Se addition reaching values of those in Na plants. Net CO2 assimilation rate (P N) decreased only slightly by limited N availability, but it enhanced significantly in both Nd and Na plants equally by 10 and 50 μM Se. Effect of Se on P N in the Na plants occurred mainly due to the stomata opening, while it was related to both stomatal and nonstomatal mechanisms in the Nd plants. The Se treatment resulted in enhancement of nitrate reductase (NR) activity in both Na and Nd plants with an optimal response at 10 μM Se. Negative correlations between nitrate concentration and NR activity indicated a partial nitrate depletion in the roots following by elevated NR activity in Nd plants. In contrast, nitrite concentrations were higher in the Se treated plants. Higher amino acids and protein concentrations in the Se-treated plants might be an indication of a general upregulation of N metabolism. However, in Na plants, the stimulation of N metabolism was not observed at 50 μM Se which could not be attributed to lesser availability of C skeletons because of maintaning higher CO2 fixation under these conditions. It implies the function of some regulatory mechanisms that are responsible for coordination of C and N metabolism in whole plant.

The Physiology and Biochemical Tolerance of Cabbage to Se (VI) Addition to the Soil and by Foliar Spraying

The effects of selenium (Se) (VI) soil fertilization with 2 μg Se L−1 or foliar spraying twice with 20 mg Se L−1 in the form of sodium (Na) selenate on the physiological and biochemical characteristics of cabbage plants were studied. The ability of the plants to take up Se and translocate it to different parts of the plants was also studied. Despite the high concentration of Se in the foliar solution, there was no effect on photosynthesis, transpiration rate, photochemical efficiency of PSII, or electron transport system activity. The amount of chlorophyll and anthocyanins were unchanged. At harvest, the concentration of Se in control plants was lower than 100 ng Se g−1 dry weight (DW), while plants treated with 20 mg Se L−1 contained 5500 ng Se g−1. Selenium enriched cabbage could be used in human nutrition. The tolerance of cabbage to Se could be explained by the formation of insoluble compounds that are not available for the plant.

Selenium addition alters mercury uptake, bioavailability in the rhizosphere and root anatomy of rice (Oryza sativa).

Mercury (Hg) is an extremely toxic pollutant, especially in the form of methylmercury (MeHg), whereas selenium (Se) is an essential trace element in the human diet. This study aimed to ascertain whether addition of Se can produce rice with enriched Se and lowered Hg content when growing in Hg-contaminated paddy fields and, if so, to determine the possible mechanisms behind these effects. Two cultivars of rice (Oryza sativa, japonica and indica) were grown in either hydroponic solutions or soil rhizobags with different Se and Hg treatments. Concentrations of total Hg, MeHg and Se were determined in the roots, shoots and brown rice, together with Hg uptake kinetics and Hg bioavailability in the soil. Root anatonmy was also studied. The high Se treatment (5 μg g(-1)) significantly increased brown rice yield by 48 % and total Se content by 2·8-fold, and decreased total Hg and MeHg by 47 and 55 %, respectively, compared with the control treatments. The high Se treatment also markedly reduced 'water-soluble' Hg and MeHg concentrations in the rhizosphere soil, decreased the uptake capacity of Hg by roots and enhanced the development of apoplastic barriers in the root endodermis. Addition of Se to Hg-contaminated soil can help produce brown rice that is simultaneously enriched in Se and contains less total Hg and MeHg. The lowered accumulation of total Hg and MeHg appears to be the result of reduced bioavailability of Hg and production of MeHg in the rhizosphere, suppression of uptake of Hg into the root cells and an enhancement of the development of apoplastic barriers in the endodermis of the roots.

Nonsense-mediated decay factors are involved in the regulation of selenoprotein mRNA levels during selenium deficiency.

Selenoproteins contain the unique amino acid selenocysteine (Sec), which is encoded by the triplet UGA. Since UGA also serves as a stop codon, it has been postulated that selenoprotein mRNAs are targeted for degradation by the nonsense-mediated mRNA decay pathway (NMD). Several reports have observed a hierarchy of selenoprotein mRNA expression when selenium (Se) is limiting, whereby the abundance of certain transcripts decline while others do not. We sought to investigate the role of NMD in this hierarchical response that selenoprotein mRNAs exhibit to environmental Se status. Selenoprotein mRNAs were categorized as being predicted sensitive or resistant to NMD based on the requirements held by the current model. About half of the selenoprotein transcriptome was predicted to be sensitive to NMD and showed significant changes in mRNA abundance in response to cellular Se status. The other half that was predicted to be resistant to NMD did not respond to Se status. RNA immunoprecipitation with essential NMD factor UPF1 revealed that the mRNAs that were the most sensitive to Se status were also the most enriched on UPF1 during Se deficiency. Furthermore, depletion of SMG1, the kinase responsible for UPF1 phosphorylation and NMD activation, abrogated the decline in transcript abundance of Se-responsive transcripts. Lastly, mRNA decay rates of Se-responsive transcripts were altered upon the addition of Se to resemble the slower decay rates of nonresponsive transcripts. Taken together, these results present novel evidence in support of a crucial role for the NMD pathway in regulating selenoprotein mRNA levels when Se is limiting.

Protective role of selenium on pepper exposed to cadmium stress during reproductive stage.

The aim of the present study was to examine the effects of exogenous selenium (Se) supplementation on the tolerance of pepper (Capsicum annuum L.) cv. Suryamukhi Cluster plants to cadmium (Cd) phytotoxicity at the reproductive stage. The pepper plants were supplied with Cd (0, 0.25 or 0.50 mM) and Se (0, 3 or 7 μM), individually or simultaneously, three times during the experiment. The obtained results show that Cd had deleterious effect on pepper plants at the reproductive stage. However, Se supplementation improved the flower number, fruit number and fruit diameter in plants exposed to 0.50 mM Cd. Moreover, both Se concentrations used in 0.25 mM Cd-treated plants and 3 μM Se in 0.50 mM Cd-treated plants enhanced fruit yield per plant as compared to Cd-alone treatment. The chlorophyll concentrations significantly increased in the fruits of Cd-exposed plants after Se addition. However, Se supplementation reduced total carotenoids and total soluble solid (TSS) concentrations in the pepper fruits exposed to Cd. Selenium also generally enhanced the total antioxidant activity of pepper fruits subjected to Cd. Both Se concentrations used increased mean productivity (MP), stress tolerance index (STI) and yield stability index (YSI) in plants grown in the medium containing 0.25 mM Cd. At low concentration (3 μM), Se significantly increased geometric mean productivity (GMP), STI and YSI of plant exposed to 0.50 mM Cd. The highest Cd concentration in the fruits was achieved at 0.50 mM Cd and Se application significantly reduced Cd accumulation in the Cd-exposed plants. Our results indicate that application of Se can alleviate Cd toxicity in pepper plants at the reproductive stage by restricting Cd accumulation in fruits, enhancing their antioxidant activity and thus improving the reproductive and stress tolerance parameters.

Interfacial reactions in Sn/Bi2Te3, Sn/Bi2Se3 and Sn/Bi2(Te1−xSex)3 couples

Bi2(Te1−xSex)3 is an important kind of n-type thermoelectric material. In this study, interfacial reactions at 250°C in the Sn/Bi2Te3, Sn/Bi2Se3 and Sn/Bi2(Te1−xSex)3 couples are examined. In the Sn/Bi2Te3 couple, the reaction zone is found to be non-planar and the reaction path is liquid/(liquid+SnTe)/Bi2Te3. But with only 2.0at.%Se addition to the Bi2Te3 substrate, very different reaction results are observed. In the Sn/Bi2(Te1−xSex)3 couple, the reaction layers are planar, and the reaction path is liquid/SnTe/BiTex/Bi2(Te1−xSex)3. In the Sn/Bi2Se3 couple, the reaction layers are also planar, the reaction path is liquid/SnSe/BiSe/Bi2Se3, and the Bi content in the SnSe phase varies. The growth rates in the Sn/Bi2Te3 couples are very fast, and the reaction layer is as thick as 1174μm in just 15min. Very dramatic reduction of growth rates has been observed with Se addition to the substrates, and the reaction layer is only 9μm in the Sn/Bi2(Te2.9Se0.1) couples after reaction for 30min.

In vitro effects of selenium on copper-induced changes in lipid metabolism of grass carp (Ctenopharyngodon idellus) hepatocytes.

The present study was performed to evaluate the in vitro effects of selenium (Se) supplementation to prevent copper (Cu)-induced changes in lipid metabolism of hepatocytes from grass carp (Ctenopharyngodon idellus). Four groups (control and 100 μM Cu in combination with 0, 5, and 10 μM Se, respectively) were chosen. Compared with the control, activities of glucose 6-phosphatedehydrogenase, 6-phosphogluconate dehydrogenase, malic enzyme, and carnitine palmitoyltransferase I (CPT I) of all three Cu-exposed groups at 24 and 48 h were significantly greater. However, among three Cu-exposed groups, increasing Se concentration tended to increase activities of G6PD and ME at 24 h and 6PGD activity at 24 and 48 h but decreased CPT I activity at 24 h. Compared with the control, Cu exposure alone, or in combination with Se, downregulated mRNA levels of sterol regulatory element-binding protein-1 (SREBP-1c), fatty acid synthase (FAS), acetyl-CoA carboxylase, peroxisome proliferator activated receptor alpha (PPARα), CPT I, and hormone-sensitive lipase (HSL) at 24 h as well as SREBP-1c, FAS, and ACC mRNA levels at 48 h. However, upregulated mRNA levels of PPARα, CPT I, and HSL, as well as decreased triglyceride content, were recorded at 48 h. Thus, although toxic at greater levels, lower levels of Se provided significant protection against Cu-induced changes in lipid metabolism. For the first time, our study indicates the dose- and time-dependent effects of Se addition on changes in lipid metabolism induced by Cu in fish hepatocytes and provides new insights into Se-Cu interaction at both enzymatic and molecular levels.

Selenium affects physiological parameters and phytochelatins accumulation in cucumber (Cucumis sativus L.) plants grown under cadmium exposure

The aim of the present study was to examine the effects of exogenous selenium (Se) on the tolerance of cucumber plants to cadmium (Cd) stress. The cucumber plants grown in a nutrient solution were supplied with Cd (0, 25 or 50μM) and Se (0, 5 or 10μM), individually or simultaneously. Under Cd-stress, there were no significant differences in the shoot biomass of the Se-supplied plants as compared to the Cd-exposed plants. However, the fresh weight (FW) of roots increased significantly after supplementation of a 50μM Cd-polluted nutrient solution with 10μM Se. The accumulation of phytochelatins (PCs) was detected in the plants treated with 25 or 50μM Cd, individually or simultaneously with Se, with a higher level noted in the roots. When the individual PCs isoforms were considered, the predominance of PC4 in the Cd-exposed roots and of PC2 in the Cd-exposed leaves was evident. An enrichment of Cd-treated plants with Se caused a reduction of PCs accumulation in roots, but did not change its concentration in leaves. The addition of Se to the Cd-containing growth media did not affect GSH accumulation in roots and leaves, as compared to Cd-alone treatment. Moreover, the supplementation of Cd-exposed plants with Se provoked a significant decrease in the level of lipid peroxides as well as a reduction of Cd content in the root tissues. Our results imply that the degree of disturbances provoked by Cd could be partially ameliorated by Se supplementation, probably due to the inhibition of Cd accumulation and a reduced lipid peroxidation in the root tissues as well as the improvement of cell membranes stability in the leaf tissues. However, the effect of Se on the Cd-stressed plants greatly depended on the proportion of these two elements in the nutrient solution.

Correlations of the Structural Properties of a Complete R2PX Series (X = Hydrogen or Halogen)

AbstractThe CgP(Se)X series (X = H, F, Cl, Br and I; CgP = 6‐phospha‐2,4,8‐trioxa‐1,3,5,7‐tetramethyladamant‐6‐yl) is generated by the addition of elemental Se to the corresponding CgPX. The crystal structures of CgPX (X = H, F, Cl, Br and I) and CgP(Se)X (X = F, Cl, Br and I) are compared. The JP,Se values are correlated with the P–Se distance and the electronegativity of X. For both the CgP(Se)X and the CgPX series, the P–C bond lengths correlate with the P–X bond lengths and with the C–P–C bond angle. These trends can be explained in terms of the δ+ charge on the P atom, which has been calculated in the gas phase. Cone‐angle measurements suggest that CgPCl, CgPBr and CgPI have essentially the same steric bulk.

Alleviation of nickel toxicity in wheat (Triticum aestivum L.) seedlings by selenium supplementation

Abstract Hydroponically grown wheat seedlings were treated with 50 μM N i and/or 15 μM Se. After a 7-day culture period, their growth parameters, N i, Se, F e, and M g contents, electrolyte leakage, photosynthetic pigment concentrations, and photochemical activity of photosystem II were determined. Exposure of wheat seedlings to N i alone resulted in reduction in the total shoot and root lengths, by 22% and 50%, respectively. Addition of Se to the N i-containing medium significantly improved the growth of these organs, compared to the seedlings subjected to N i alone. Application of Se decreased the accumulation of N i in shoots and roots and partially alleviated the N i-induced decrease in F e and M g concentations in shoots. Electrolyte leakage increased in response to N i stress, but in shoots it was diminished by Se supplementation. Exposure to N i led to a decrease in chlorophyll a and b contents and enhancement of chlorophyll a/b ratio, but did not influence the concentration of carotenoids. Enrichment of the N i-containing medium with Se significantly increased chlorophyll b content, compared to the seedlings treated with N i alone. Photochemical activity, estimated in terms of the maximum quantum yield of photosystem II , decreased in response to N i treatment but was significantly improved by simultaneous addition of Se. Results of our study suggest that alleviation of N i toxicity in wheat seedlings by Se supplementation may be related to limitation of N i uptake.

Effects of selenium and vitamin E supplementation on selenium distribution and meat quality of pigs

The study was conducted on 60 pigs kept in individual pens. The animals were allocated to four groups. The growing-finishing pigs from the control group were fed with basic feed containing 0.3 mg selenium (Se) derived from Na2SeO3 kg−1 and 60 mg of dl-α-tocopheryl acetate kg−1. The remaining three groups were differentiated by adding 0.2 mg kg−1 Se-enriched yeast (Saccharomyces cerevisiae) and/or 60 mg vitamin E to feed (grower and finisher). Our results show that the addition of organic Se to inorganic Se commonly used in pig feed caused a significant increase in hepatic Se and muscle. This indicates the possibility of using these products as functional foods to improve Se status in humans residing within regions which are deficient in this trace element. We found no beneficial effect of supplementation with vitamin E and Se on the quality of the meat.

Effects of Se-enrichment on yield, fruit composition and ripening of tomato (Solanum lycopersicum) plants grown in hydroponics

Selenium appears to be effective in promoting plant development and delaying the onset of senescence. Besides the effects on the metabolism and physiology of different crops, controlled increases in Se concentrations enhance the health-related properties of the produce. To study the effects of selenium on fruit composition and ripening physiology, an experiment was carried out on tomato (Solanum lycopersicum) plants grown in hydroponics. Sodium selenate was added to the nutrient solution at a rate of 0 (control) and 1mgSeL−1. The selenium added to the nutrient solution was absorbed by the roots, and the Se concentration was higher in leaves than in fruits. The addition of Se did not significantly influence the cumulative yield of tomato plants, but a delay in the onset of fruit ripening was detected, and the harvesting of control plants began earlier than in Se-treated plants. The addition of Se did not significantly affect the qualitative parameters with the exception of β-carotene content, which was lower in red ripe fruit treated with selenium. Since β-carotene accumulation is a ripening-related event in tomato, the lower amount of this compound may be associated with a general delay of ripening. This is confirmed by the reduced biosynthetic rate of ethylene, observed in Se-treated tomatoes, which also showed a reduced rate in colour change. This thus confirmed that ripening-related processes, such as the degradation of chlorophyll and the synthesis of carotenoids, are affected by selenium - with potential benefits in terms of storage and shelf-life. Our results showed that 100g of tomato hydroponically grown with a nutrient solution supplemented with Se provided a total of 58μg Se. Thus, the daily consumption of 100g of enriched tomato does not lead to Se toxicity, but can even provide a rational Se supplementation. This suggests that the addition of Se in a nutrient solution is useful for producing tomatoes with greater beneficial properties for human health.

The effect of Se doping on spectroscopic and electrical properties of GeTe

Selenium doped thin films of GeTe alloys were investigated for their structural modifications by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, X-ray photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The band gap increase from 0.69 to 1.10eV with increasing Se addition signifies the possibility of band gap tuning in the material. Disorder decreases, band widens and conductivity saturates about 0.20at.% of Se addition. Structural changes are explained by the bond theory of solids. The as-deposited films are amorphous and 0.50at.% Se alloy forms a homogeneous amorphous phase with a mixture of GeSe and TeSe bonds. The XPS core level spectra and Raman spectra investigation clearly indicate the formation of GeSe, GeTe2 and TeSe bonds with Se addition. Crystallization temperature is found to be increasing with Se and the 0.10at.% Se alloy is found to have a higher resistance contrast compared to other Se concentration alloys. Up to 0.10at.% of Se addition can enhance GeTe phase change memory properties.

A dual effect of Se on Cd toxicity: evidence from plant growth, root morphology and responses of the antioxidative systems of paddy rice

It is well established that low levels of selenium (Se) are protective against low levels of cadmium (Cd) toxicity and can significantly reduce Cd uptake in plants. However, our previous study reported that the addition of Se hampered the growth of paddy rice exposed to high levels of Cd and enhanced Cd uptake. The relevant mechanisms underlying the dual effects of Se on Cd uptake and toxicity are unclear. This study attempted to illustrate the potential mechanisms of the effect of selenite on Cd toxicity and uptake in paddy rice using hydroponic culture, mainly focusing on the changes in root morphology and the responses of antioxidative enzymes to low and high levels of Se and Cd. A root image analysis system equipped with WinRHIZO image analysis software was used to analyze the root morphology. When no Cd was added, a level of Se as low as 0.2 mg L−1 decreased the shoot malondialdehyde (MDA) content and enhanced the growth of paddy rice; however, Se levels of up to 0.8 mg L−1 inhibited the growth and increased the MDA content of shoots, demonstrating the dual effect of Se on plants. Superoxide dismutase (SOD) appeared to be activated, especially in the roots, when Se was added to solutions containing a high concentration of Cd; however, single addition of Se or Cd inhibited SOD activity. The addition of Se to a solution containing Cd stimulated only root ascorbate peroxidase (APX) activity. Peroxidase (POD) and catalase (CAT) enzymes appeared to have limited roles in detoxifying Cd when increasing amounts of Se were added. When Se was absent from the solution, Cd levels as low as 1 mg L−1 had beneficial effects on root growth but not on shoot growth; however, these beneficial effects were accompanied by a significant increase in shoot MDA content. Cd levels higher than 4 mg L−1 inhibited the growth of shoots and roots, suggesting that Cd toxicity had occurred in the paddy rice. The addition of Se to the treatments containing Cd significantly reduced the proportion of fine roots and tended to increase the proportion of coarse roots, which might explain the decreases in Cd uptake in this study and the decreases in the uptake of other minerals observed in other studies. The addition of Se could mitigate the toxicity of Cd; however, these protective effects are likely dependent on the doses of Se and Cd. Several Se-mediated mechanisms for the mitigation of Cd toxicity were proposed, including (1) an increase in the proportion of coarse roots to reduce Cd uptake and (2) the activation of certain antioxidative enzymes. When 12 mg L−1 Cd was added to the solution, the addition of Se inhibited plant growth instead of mitigating the toxicity of Cd; this finding was thought to be related to the increased permeability of the root cells to Cd due to the damaged cell membranes produced by Se supplementation.

Development and mapping of seleniferous soils in northwestern India

Periodic surveys were undertaken to identify and characterize Se-contaminated soils in northwestern India. Total Se content varied from 0.023 to 4.91mgkg−1 in 0–15cm surface soil and 0.64–515.0mgkg−1 in samples of vegetation. Selenium-contaminated land occupying an area of 865ha was classified into different categories based on total Se content of soils as moderately contaminated (0.5–2.0mg Sekg−1) and highly contaminated (>2.0mg Sekg−1). The normal soils contained <0.5mg Sekg−1. The soil map was prepared using village level cadastral maps. Se-contaminated soils were silty loam to silty clay loam in texture and tested pH 7.9–8.8, electrical conductivity 0.3–0.7dSm−1, calcium carbonate 0.1–4.1% and organic carbon 0.4–1.0%. Selenium was present throughout the soil profile up to 2m depth; 0–15cm surface soil layer contained 1.5 to 6.0 times more Se than in subsurface layers.Selenium content in rock samples collected from lower and upper Shiwalik sub-Himalayan ranges varied from 1864 to 2754 and 11 to 847μgkg−1, respectively. The sediments transported through seasonal rivulets linking the Shiwalik ranges to affected sites contained 0.57–2.89mg Sekg−1. The underground water containing 2.5–69.5μg SeL−1 used for irrigating transplanted rice grown in Se-contaminated area resulted in a net Se addition in soil up to 881gha−1y−1; possibly further aggravating the Se-toxicity problem. Presence of substantial amount of Se in rock samples and sediments of seasonal rivulets suggests that Se-rich materials are being transported from Shiwalik hills and deposited in regions where seasonal rivulets end up.

EFFECTS OF SELENIUM ENRICHMENT OF TOMATO PLANTS ON RIPE FRUIT METABOLISM AND COMPOSITION

EFFECTS OF SELENIUM ENRICHMENT OF TOMATO PLANTS ON RIPE FRUIT METABOLISM AND COMPOSITION

A new methodology involving stable isotope tracer to compare simultaneously short- and long-term selenium mobility in soils

A better understanding of Se fate in soils is required for different environmental issues, such as radioactive waste management or soil fertilization procedures. In these contexts, the mobility and speciation of Se have to be studied at both short and long terms after Se inputs. Here, we present a new methodology to monitor simultaneously the reactivity of added (isotopic enriched tracers) and ambient Se at trace level in soils by high-performance liquid chromatography inductively coupled plasma mass spectrometry (ICP-MS) following specific extractions. To do so, the collision/reaction cell of the ICP-MS instrument and the interference corrections were optimized to measure reliably the four major Se isotopes. To exemplify the method capabilities, the behaviors of added (77)Se(IV) and ambient Se were followed up in two soils submitted to an ageing process during 3 months. The solid/liquid distribution of added Se reached a steady state after 1 month while its speciation and distribution among soil solid phases were still changing after 3 months. The results clearly demonstrate that slow processes are involved in Se retention and transformation in soils. The usual short-term experiments (<1 month) performed after Se addition are thus not suitable for long-term risk assessment. Interestingly, the behavior of added Se tended to that of ambient Se, suggesting that ambient Se would be useful to infer the fate of Se input over long time scales.