Se Uptake Research Articles

Effects of indole acetic acid on the growth and selenium absorption characteristics of Cyphomandra betacea seedlings

To study the effects of indole acetic acid (IAA) on the growth and selenium (Se) absorption of fruit tree, a pot experiment was conducted to study the effects of different concentrations involved in the spraying of 0 (the control), 30, 60, 90, and 120 mg/L IAA on the growth and Se uptake of C. betacea seedlings. The concentrations of 30, 60, and 90 mg/L IAA increased the various organs’ biomass and net photosynthetic rate of C. betacea seedlings compared to the control, while the concentration of 120 mg/L IAA had no significant effect on that. Only the concentration of 60 mg/L IAA increased the chlorophyll (chlorophyll a, chlorophyll b, total chlorophyll) contents in C. betacea seedlings compared to the control. The concentrations of 30, 60, and 90 mg/L IAA also increased the antioxidant enzymes’ (superoxide dismutase, peroxidase, and catalase) activities and soluble protein content of C. betacea seedlings compared to the control. For Se content, compared to the control, the concentrations of 60 and 90 mg/L IAA increased the Se contents in roots, stems, leaves, and shoots of C. betacea seedlings, and also enhanced the Se bioconcentration factor. Therefore, spraying IAA with the appropriate concentration (60–90 mg/L) could promote the C. betacea seedlings’ growth and Se absorption, and the best concentration was 60 mg/L IAA.

Selenium uptake, volatilization, and transformation by the cyanobacterium Microcystis aeruginosa and post-treatment of Se-laden biomass

With a narrow margin between beneficial and toxic effects, selenium (Se) is of great concern due to its increasing level in aquatic environments. The accumulation and transformation of Se by the cyanobacterium Microcystis aeruginosa and effects of nutrients, particularly sulfate, were investigated. The nutrient-deprived cyanobacterium removed water-borne selenate (82.2 ± 0.93%) faster than selenite (58.9 ± 1.77%), with 86.0 ± 1.41% and 77.2 ± 1.00%, respectively, of the Se accumulated in the biomass and the rest volatilized. When supplied with excess nutrients, the Se accumulation and volatilization rates were significantly inhibited, with the removal efficiency dropping to 50.2 ± 2.59% and 7.37 ± 0.93% for selenite and selenate, respectively. When M. aeruginosa was tested with inadequate, appropriate, and adequate levels of sulfate, Se uptake decreased with increasing sulfate concentrations, particularly for selenate (from 34.1 to 4.81%). Using X-ray absorption near-edge structure to speciate biomass Se, selenite and selenate were transformed to organo-Se (87.3–100%), with or without nutrients present, suggesting M. aeruginosa could efficiently reduce Se oxyanions to more bioavailable forms. With increasing sulfate levels (5.0 and 10.0 mg S/L), percentages of SeMet converted from selenite decreased by 28.2–33.0%, with 19.1–33.2% as elemental Se, while organo-Se remained dominant (93.6–95.1%) in selenate-treated M. aeruginosa. Transmission electron microscopy shows structural damage in the cell wall at exposure to selenite (1600 μg Se/L), with the intracellular structure intact. To prevent Se biomagnification along aquatic food chains, the Se-laden biomass was combusted as a post-treatment, leading to a significant reduction in Se content (∼99.2%) and Se bioavailability, with inorganic Se (45.0–70.5%) predominant in the residue.

Raman Microspectroscopic Analysis of Selenium Bioaccumulation by Green Alga Chlorella vulgaris.

Selenium (Se) is an element with many commercial applications as well as an essential micronutrient. Dietary Se has antioxidant properties and it is known to play a role in cancer prevention. However, the general population often suffers from Se deficiency. Green algae, such as Chlorella vulgaris, cultivated in Se-enriched environment may be used as a food supplement to provide adequate levels of Se. We used Raman microspectroscopy (RS) for fast, reliable, and non-destructive measurement of Se concentration in living algal cells. We employed inductively coupled plasma-mass spectrometry as a reference method to RS and we found a substantial correlation between the Raman signal intensity at 252 cm−1 and total Se concentration in the studied cells. We used RS to assess the uptake of Se by living and inactivated algae and demonstrated the necessity of active cellular transport for Se accumulation. Additionally, we observed the intracellular Se being transformed into an insoluble elemental form, which we further supported by the energy-dispersive X-ray spectroscopy imaging.

Solution-processed near-infrared Cu(In,Ga)(S,Se)2 photodetectors with enhanced chalcopyrite crystallization and bandgap grading structure via potassium incorporation

Although solution-processed Cu(In,Ga)(S,Se)2 (CIGS) absorber layers can potentially enable the low-cost and large-area production of highly stable electronic devices, they have rarely been applied in photodetector applications. In this work, we present a near-infrared photodetector functioning at 980 nm based on solution-processed CIGS with a potassium-induced bandgap grading structure and chalcopyrite grain growth. The incorporation of potassium in the CIGS film promotes Se uptake in the bulk of the film during the chalcogenization process, resulting in a bandgap grading structure with a wide space charge region that allows improved light absorption in the near-infrared region and charge carrier separation. Also, increasing the Se penetration in the potassium-incorporated CIGS film leads to the enhancement of chalcopyrite crystalline grain growth, increasing charge carrier mobility. Under the reverse bias condition, associated with hole tunneling from the ZnO interlayer, the increasing carrier mobility of potassium-incorporated CIGS photodetector improved photosensitivity and particularly external quantum efficiency more than 100% at low light intensity. The responsivity and detectivity of the potassium-incorporated CIGS photodetector reach 1.87 A W−1 and 6.45 times 1010 Jones, respectively, and the − 3 dB bandwidth of the device extends to 10.5 kHz under 980 nm near-infrared light.

Selenite and Selenate Adsorption on Low-Crystalline Magnesium Oxide Under Alkaline Conditions

Natural geochemical processes and anthropogenic activities produce selenium (Se)-containing wastewater, in which selenium is present as selenous acid (Se(IV)) and selenic acid (Se(VI)). Herein, we evaluated the Se removal performances of magnesium oxide (MgO) with different crystallinities at pH 10.5. Normal MgO and low-crystalline (LC-MgO) were reacted in 1, 2, and 5 mg dm−3 Se(IV) or Se(VI) solution for 120 min. The Se concentrations of both the species did not apparently decrease in the normal MgO systems. However, >90% of Se(IV) was successfully removed by LC-MgO within 5 min under all conditions. X-ray diffraction (XRD) analysis indicated that Se(IV) was removed via surface complexation on Mg(OH)2 formed by the rapid hydration of LC-MgO. The enhancement of Se removability of the LC-MgO system was explained by the rapid hydration of the higher surface area of LC-MgO when compared with that of normal MgO. Majority of the Se(VI) (60–80%) was removed by LC-MgO during the first 20 min; however, it was gradually released back into the solution over time. During hydration, the changing XRD peak patterns and zeta potential of LC-MgO indicated that the increased charge density obtained by the accumulation of Mg2+ released via MgO dissolution would cause the temporal uptake of Se(VI) in the interlayer of Mg(OH)2. Subsequently, the charge density decreased with the hydration of Mg2+, indicating that Se(VI) was redissolved. Therefore, LC-MgO is a promising material for treating Se-containing alkaline wastewater. However, short-time operation and low concentration (<1 mg dm−3) must be ensured for successful Se(VI) removal.

Selenium uptake and grain nutritional quality are affected by nitrogen fertilization in rice (Oryza sativa L.).

The effects of selenium in rice grain composition depend on the soil nitrogen supply. Selenium and nitrogen have the potential to modify rice grain composition; however, it is unclear how the combined effect of Se and nitrogen affects the grain nutritional quality of rice. In our study, grain Se concentration was positively associated with the increased availability of nitrogen in soil. The accumulation of Se in grain of rice plants treated with Se combined with nitrogen was accompanied by an increase in expression of NRT1.1B, a rice nitrate transporter and sensor, in root. Moreover, Se potentiates the response of nitrogen supply in expression of sulfate transporter OsSULTR1.2, phosphate transporter OsPT2 and silicon transporter OsNIP2.1 in root, thereby increasing root Se uptake capacity. The combination of Se with high nitrogen increased the concentrations of protein, carbohydrates, Se, Mo and Mg, but decreased concentrations of Fe, Mn, Cu and Zn in grain. Overall, our results revealed that many of the effects of Se in rice grain composition are due to a shift in the nitrogen status of the plant.

Trophic dynamics of selenium in a boreal lake food web.

Selenium (Se) is both an essential micronutrient and a contaminant of concern that is of particular interest in mining-influenced waterbodies in Canada. The objective of this research was to characterize the trophic dynamics of selenium along a gradient of exposure concentrations in a Canadian boreal lake ecosystem. From June 20 to August 22, 2018, six limnocorrals (littoral, ∼3000L enclosures) were spiked with mean measured concentrations of 0.4, 0.8, 1.6, 3.4, 5.6 and 7.9μg Se/L as selenite, and three limnocorrals served as untreated controls (background aqueous Se=0.08-0.09μg/L). Total Se (TSe) concentrations in water, periphyton, phytoplankton, sediment, benthic macroinvertebrates, zooplankton and female finescale dace (Phoxinus neogaeus; added on day 21 of the experiment) were measured throughout and at the end of the experiment. Total Se bioaccumulation by organisms was generally non-linear. Greater uptake by phytoplankton than periphyton was observed. Taxonomic differences in accumulation of TSe by invertebrates (Heptageniidae=Chironomidae>zooplankton) were observed as well. Fish muscle and ovary tissue TSe bioaccumulation was more variable than that at lower trophic levels and uptake patterns indicated that fish did not reach steady state concentrations. This research provides field-derived models for the uptake of Se by algae and invertebrates, and contributes to a better understanding of the dynamics of TSe bioaccumulation over a gradient of exposure concentrations in cold-water lentic systems.

Temporal Influences on Selenium Partitioning, Trophic Transfer, and Exposure in a Major U.S. River

Hydrologic and irrigation regimes mediate the timing of selenium (Se) mobilization to rivers, but the extent to which patterns in Se uptake and trophic transfer through recipient food webs reflect the temporal variation in Se delivery is unknown. We investigated Se mobilization, partitioning, and trophic transfer along approximately 60 river miles of the selenium-impaired segment of the Lower Gunnison River (Colorado, USA) during six sampling trips between June 2015 and October 2016. We found temporal patterns in Se partitioning and trophic transfer to be independent of those in dissolved Se concentrations and that the recipient food web sustained elevated Se concentrations from earlier periods of high Se mobilization. Using an ecosystem-scale Se accumulation model tailored to the Lower Gunnison River, we predicted that the endangered Razorback Sucker (Xyrauchen texanus) and Colorado Pikeminnow (Ptychocheilus lucius) achieve whole-body Se concentrations exceeding aquatic life protection criteria during periods of high runoff and irrigation activity (April-August) that coincide with susceptible phases of reproduction and early-life development. The results of this study challenge assumptions about Se trophodynamics in fast-flowing waters and introduce important considerations for the management of Se risks for biota in river ecosystems.

The spotted ratfish Hydrolagus colliei as a potential biomonitor of mercury and selenium from deep-waters of the northern Gulf of California

The purpose of this work was to use the deep-water chimaera Hydrolagus colliei to examine the bioaccumulation and availability of Hg and Se in its deep-water habitat; the Se:Hg molar ratio was calculated to establish baseline information of the species and its associated ecosystem. The organisms were collected from northern Gulf of California. Hg levels in muscle were higher than liver and the opposite pattern happened with Se concentrations. Female had total lengths and weights higher than male but there were not found differences between elements concentrations by sex. Hg in muscle was correlated with weight. Molar Se:Hg ratio in muscle was the lowest compared to the liver. It was hypothesized that Hg and Se uptake to H. colliei were by its feeding habits because is a dominant species component of the demersal ecosystem and that play and important functional role in the control of oceanic ecosystem structure and function.

Specificity and Plasticity of the Functional Ionome of Brassica napus and Triticum aestivum Subjected to Macronutrient Deprivation.

The composition of the functional ionome was studied in Brassica napus and Triticum aestivum with respect to the response of 20 elements under macronutrient deprivation. Analysis of relative root contents showed that some nutrients, such as Fe, Ni, Cu, Na, V, and Co, were largely sequestered in roots. After 10 days of deprivation of each one of these 6 macronutrients, plant growth was similar to control plants, and this was probably the result of remobilization from roots (Mg and Ca) or old leaves (N, P, K, S). Some tissue concentrations and net nutrient uptakes into roots were either decreased or increased, revealing multiple interactions (93 in wheat, 66 in oilseed rape) that were common to both species (48) or were species specific. While some interactions have been previously described (increased uptake of Na under K deficiency; or increased uptake of Mo and Se under S deficiency), a number of new interactions were found and some key mechanisms underlying their action have been proposed from analysis of Arabidopsis mutants. For example, nitrate uptake seemed to be functionally linked to Na(influx, while the uptake of vanadium was probably mediated by sulfate transporters whose expression was stimulated during S deprivation.

Effects of algal blooms on selenium species dynamics: A case study in the Changjiang Estuary, China

The selenium cycle in the marine environment is sensitive to biological activity, but knowledge of dissolved Se species dynamics during coastal algal blooms is limited. Selenium species dynamics during diatom blooms in the Changjiang Estuary were investigated in a survey of dissolved inorganic and organic Se. Dissolved inorganic Se (Se(IV) + Se(VI)) was the predominant species in river-dominanated areas, while dissolved organic selenide (DOSe) was predominant in ocean-dominanated areas. Relationships between DOSe and chromophoric dissolved organic matter involved both humic- and protein-like components, suggesting distinct sources of DOSe in river- and ocean-dominance areas, respectively. A three-endmember-mixing model was used to describe biological processes in ocean-dominanated surface waters. In diatom-bloom areas, the co-occurrence of depletion of Se(IV) and Se(VI) (of ~90% and 30%, respectively) and a 44% increase in production of DOSe indicates that phytoplankton act as vectors for Se species transformation. A Se(IV)*P indicator was developed to quantify limiting concentrations of Se(IV) in water relative to that of phosphorus. Negative Se(IV)*P concentrations indicate that Se(IV) is limited due to biological utilization of dissolved inorganic phosphorus by diatoms, resulting in secondary uptake of Se(VI) in the Changjiang Estuary.

Phosphorus and selenium uptake, root morphology, and carboxylates in the rhizosheath of alfalfa (Medicago sativa) as affected by localised phosphate and selenite supply in a split-root system.

Low availability of phosphorus (P) is a key limiting factor for the growth of many crops. Selenium (Se) is a nutrient for humans that is acquired predominantly from plants. Localised P and Se supply may affect P- and Se-uptake efficiency. Our aim was to examine the mechanisms of alfalfa (Medicago sativa L.) to acquire P and Se when the elements are heterogeneously or homogeneously distributed in soil, and how P and Se supply affect plant growth and uptake of P and Se. We conducted a split-root experiment growing alfalfa in a loess soil with two distribution patterns (i.e. heterogeneous and homogeneous) of P and Se. The application rates of P (KH2PO4) and Se (Na2SeO3) were 0 and 20mgPkg-1, and 0 and 1mgSekg-1, respectively. Our results showed that plants absorbed more Se when both P and Se were supplied homogeneously than when supplied heterogeneously. Supplying Se had a positive effect on plant P content. Localised P supply resulted in the exudation of more carboxylates by roots than homogeneous P supply did. Soil microbial biomass P was significantly greater when P was supplied homogeneously. Shoot-to-root translocation of Se had a positive effect on P-uptake efficiency. These results indicated that, compared with homogeneous P supply, localised P supply promoted P and Se uptake by increasing the amount of rhizosheath carboxylates and weakening the competition between roots and microbes. Translocation of Se within plant organs was promoted by the application of P, thus enhancing the P-uptake efficiency of alfalfa.

Selenium oxyanion exchange with Mg(II)-Fe(III) and Fe(II)-Fe(III) layered double hydroxides

Immobilization of selenium oxyanions from water resources is a helpful strategy to mitigate exposure to Se at concentrations toxic to human and ecosystem health. Pyroaurite-type minerals are layered double hydroxides with high anion exchange capacity with relevance in subsurface environments and applicable to water treatment technologies. Three types of Mg(II)-Fe(III) pyroaurites and Fe(II)-Fe(III) green rusts were evaluated in kinetic studies to determine the influence of different interlayer anions on the uptake of dissolved selenate (SeO42−) and selenite (HSeO3−, SeO32−). Selenate and selenite uptake extents with pyroaurites were controlled by the identity of the interlayer anion according to the order Cl−> SO42−> CO32−, as predicted by known interlayer anion preferences for LDH. The kinetics of Se uptake typically expressed a rapid initial anion exchange step followed by a slow re-exchange back to solution due to competition with expelled interlayer anions. Excess dissolved interlayer anions and high pH values exacerbated this reverse exchange of Se. The results suggest Se oxyanions taken up by pyroaurites may not be firmly sequestered. Selenate uptake by redox-active green rust appears to be subject to the same interlayer anion preference as non-redox active pyroaurite, suggesting that the ability of green rust to reduce selenium oxyanions may be limited by the anion exchange process.

Significant Accumulation of Iodine and Selenium in Chicory (Cichorium intybus L. var. foliosum Hegi) Leaves after Foliar Spraying.

The interactions between the uptake of selenium (as selenite and selenate) and iodine (as iodate and iodide) by red chicory (Cichorium intybus L. var. foliosum Hegi) and their effects on selected morphological and physiological characteristics were investigated. Seedlings were transplanted to the field, and at the onset of head formation, the plants were foliar-sprayed with the following solutions: Milli-Q water (control), Se (IV), Se (VI), I (−I), I (V), Se (IV) + I (−I), Se (IV) + I (V), Se (VI) + I (−I) and Se (VI) + I (V). The different treatments had no significant effects on the yield (39.8–51.5 t ha−1) and mass (970–1200 g) of the chicory heads. The selenium content in Se-treated plants was up to 5.5-times greater than the control plants. The iodine content in the chicory leaves enriched with I was 3.5-times greater than the control plants. Iodide or iodate, applied together with selenite in the spray solution, increased the uptake of Se by chicory plants, while both forms of iodine, applied together with selenate, reduced the uptake of Se. Plants treated with I (V) had lower amounts of chlorophyll a and carotenoids than the control, while respiratory potential was higher than the control, which indicated the possible presence of stress in I (V)-treated plants. However, the potential photochemical efficiency of photosystem II was similar and close to the theoretical maximum (0.83) in the control and treated groups, which indicated that all of the plants were in good condition. Furthermore, the plant mass and yield were comparable in the control and treated groups. Molecular studies, like gene expression analysis, would represent a major upgrade of the present study by defining the mechanisms of Se and I uptake and their interactions and by enhancing the knowledge of the Se and I transporters.

Effects of sulfur application on selenium uptake and seed selenium speciation in soybean (Glycine max L.) grown in different soil types

AimsThe objective of the present study was to elucidate the effects of sulfur (S) application on selenium (Se) uptake and seed Se speciation in high-protein soybean (Glycine max L.) grown in different soil types. MethodsPot experiments were conducted with soybean plants grown in yellow-brown soil (pH 5.68) and in calcareous alluvial soil (pH 7.87). Sodium selenate (Na2SeO4, 2 mg kg−1) was applied to soil with or without S fertilizer (S, 100 mg kg−1). ResultsSoybean grain yield and total biomass in calcareous alluvial soil were both approximately 1.3-fold the levels in yellow-brown soil. Following Se application, seed Se concentration in calcareous alluvial soil was 3.2-fold the concentration in yellow-brown soil, although additional S application reduced the corresponding seed Se concentrations by 55.6% and 38.6%, respectively. Generally, Se application facilitated Se translocation and enrichment in soybean seeds. Organic Se accounted for 92% of seed total Se and Se-methionine (>90%) was always the major Se species. Available Se (soluble and exchangeable fractions) accounted for 50.7% (yellow-brown soil) and 70.1% (calcareous alluvial soil) of soil total Se under Se treatment, while additional S application decreased the corresponding proportion of soluble Se by 12.6% and 14.4%. ConclusionsThe bioavailability of selenate in calcareous alluvial soil was higher than the bioavailability in yellow-brown soil and was more negatively affected by S application. Although S application inhibited Se uptake in soybean plants in both soil types, it did not influence seed Se speciation and Se-methionine was the major Se species.

Selenium Toxicity in Plants and Environment: Biogeochemistry and Remediation Possibilities.

Selenium (Se) is a widely distributed trace element with dual (beneficial or toxic) effects for humans, animals, and plants. The availability of Se in the soil is reliant on the structure of the parental material and the procedures succeeding to soil formation. Anthropogenic activities affect the content of Se in the environment. Although plants are the core source of Se in animal and human diet, the role of Se in plants is still debatable. A low concentration of Se can be beneficial for plant growth, development, and ecophysiology both under optimum and unfavorable environmental conditions. However, excess Se results in toxic effects, especially in Se sensitive plants, due to changing structure and function of proteins and induce oxidative/nitrosative stress, which disrupts several metabolic processes. Contrary, Se hyperaccumulators absorb and tolerate exceedingly large amounts of Se, could be potentially used to remediate, i.e., remove, transfer, stabilize, and/or detoxify Se-contaminants in the soil and groundwater. Thereby, Se-hyperaccumulators can play a dynamic role in overcoming global problem Se-inadequacy and toxicity. However, the knowledge of Se uptake and metabolism is essential for the effective phytoremediation to remove this element. Moreover, selecting the most efficient species accumulating Se is crucial for successful phytoremediation of a particular Se-contaminated area. This review emphasizes Se toxicity in plants and the environment with regards to Se biogeochemistry and phytoremediation aspects. This review follows a critical approach and stimulates thought for future research avenues.

Effect of Selenium Form and Salicylic Acid on the Accumulation of Selenium Speciation Forms in Hydroponically Grown Lettuce

Selenium (Se) uptake by plants depends on its form and salicylic acid (SA) can increase the efficiency of plant biofortification in Se. This study investigated the effects of selenite (Na2SeO3) and selenomethionine (SeMet) applied individually or together with SA on a total content of Se, Se speciation forms, yield and content of sugars and ascorbic acid of lettuce, as well as activity of selenocysteine methyltransferase (smt) and methionine methyltransferase (mmt) genes of the Se metabolic pathway. Lettuce was grown in the nutrient film technique (NFT) system. Se and SA were used at doses of 0.5 and 10.0 mg dm−3 of the nutrient solution, respectively. The treatments were: 1. control, 2. Na2SeO3, 3. Na2SeO3 + SA, 4. SeMet, 5. SeMet + SA, 6. SA. Se was accumulated more in the roots than the leaves. SeMet was more effective in biofortification than Na2SeO3. SA enhanced Se uptake, especially organic Se. Plants supplied with SeMet alone or SeMet + SA accumulated in their leaves mainly SeMet and methylselenocysteine (MeSeCys), while those treated with Na2SeO3 or Na2SeO3 + SA accumulated MeSeCys and selenite (SeO3−2). The roots showed no expression of smt, while the expression of two mmt genes was independent of either Se or SA. The leaves of plants supplied with Na2SeO3 demonstrated the strongest expression of mmt and smt.

Exploring the new dimensions of selenium research to understand the underlying mechanism of its uptake, translocation, and accumulation.

Selenium (Se) is a vital mineral for both plants and animals. It is widely distributed on the earth's crust and is taken up by the plants as selenite or selenate. Plants substantially vary in their physiological response to Se. The amount of Se in edible plants is genetically controlled. Its availability can be determined by measuring its phytoavailability in soil. The low concentration of Se in plants can help them in combating stress, whereas higher concentrations can be detrimental to plant health and in most cases it is toxic. Thus, solving the double-edged sword problem of nutritional Se deficiency and its elevated concentrations in environment requires a better understanding of Se uptake and metabolism in plants. The studies on Se uptake and metabolism can help in genetic biofortification of Se in plants and also assist in phytoremediation. Moreover, Se uptake and transport, especially biochemical pathways of assimilation and incorporation into proteins, offers striking mechanisms of toxicity and tolerance. These developments have led to a revival of Se research in higher plants with significant break throughs being made in the previous years. This review explores the new dimensions of Se research with major emphasis on key research events related to Se undertaken in last few years. Further, we also discussed future possibilities in Se research for crop improvement.

Selenium Biofortification and Interaction With Other Elements in Plants: A Review.

Selenium (Se) is an essential element for humans and animals and its deficiency in the diet is a global problem. Crop plants are the main source of Se for consumers. Therefore, there is much interest in understanding the factors that govern the accumulation and distribution of Se in the tissues of crop plants and the mechanisms of interaction of Se absorption and accumulation with other elements, especially with a view toward optimizing Se biofortification. An ideal crop for human consumption is rich in essential nutrient elements such as Se, while showing reduced accumulation of toxic elements in its edible parts. This review focuses on (a) summarizing the nutritional functions of Se and the current understanding of Se uptake by plant roots, translocation of Se from roots to shoots, and accumulation of Se in grains; and (b) discussing the influence of nitrogen (N), phosphorus (P), and sulfur (S) on the biofortification of Se. In addition, we discuss interactions of Se with major toxicant metals (Hg, As, and Cd) frequently present in soil. We highlight key challenges in the quest to improve Se biofortification, with a focus on both agronomic practice and human health.

Insights into uptake, accumulation, and subcellular distribution of selenium among eight wheat (Triticum aestivum L.) cultivars supplied with selenite and selenate

Selenium (Se)-enriched wheat can be improved by altering Se sources and selecting wheat cultivars. Such improvement can affect subcellular distribution and speciation of Se in wheat. Thus, a pot experiment was conducted to investigate Se uptake and distribution when Se was applied as selenite or selenate at low and high rates (1 and 10 mg kg−1, respectively). Moreover, Se’s impact on the grain and biomass yield of eight wheat cultivars was also investigated. The subcellular distribution and speciation of Se were also explored to elucidate Se metabolism and micro-distribution pattern in wheat. Results showed that biomass and grain yield were decreased with the application of both selenite and selenate in almost all the cultivars, regardless of the Se rate. Application high Se rate resulted in a significant (p < 0.05) decrease in grain yield and biomass compared with low rate of Se. Compared with the low rate of selenite application, the grain and the biomass yield of ZM-9023 significantly (p < 0.05) increased by about 15% for low rate of selenate application. In addition, both selenite and selenate treatment increased the uptake of Se in each part of wheat, compared with the control. Selenium was mostly accumulated in the grain and root of wheat under selenite treatment, while more Se accumulation was found in leaves and straw for selenate application. Further investigation on the subcellular distribution of Se showed that the proportion of Se in soluble fraction was significantly (p < 0.05) higher in wheat leaves than that in organelle fraction and cell walls (46%–66%). Meanwhile, Se6+ was the main species found in soluble fraction, whereas SeMet and MeSeCys were the species predominantly stored in organelle fraction. In conclusion, wheat cultivar ZM-9023 is the most Se-rich potential cultivar, and the isolation of Se in the soluble fraction plays an important role in Se tolerance and accumulation.