Fate of selenium in soil: A case study in a maize (Zea mays L.) field under two irrigation regimes and fertilized with sodium selenite

Rational Combination of Selenium Application Rate and Planting Density to Improve Selenium Uptake, Agronomic Traits, and Yield of Dryland Maize

Exogenous selenium application could effectively improve the selenium absorption of crops affected by different climatic conditions due to changes in the planting environment and planting conditions. We planted maize at planting densities of 67,500 plants ha-1 (D1) and 75,000 plants ha-1 (D2). Five selenium fertilizer gradients of 0 mg m-2 (Se0), 7.5 mg m-2 (Se1), 15.0 mg m-2 (Se2), 22.5 mg m-2 (Se3), and 30.0 mg m-2 (Se4) were applied to investigate the response of the plants to selenium fertilizer application in terms of the gradient selenium absorption and substance accumulation. With the increase in the amount of selenium fertilizer applied, more of the selenium fertilizer will be absorbed and transported from the leaves to the grains, and the selenium content of the grains will gradually increase and exceed the selenium content of leaves. Under the D2 density in 2022, the selenium content of the grains under Se1, Se2, Se3, and Se4 treatments increased by 65.67%, 72.71%, and 250.53%, respectively, compared with that of Se0. A total of 260.55% of the plants showed a gradient of grain > leaf > cob > stalk from the Se2 treatment, and the overall selenium content of the plants increased first and then decreased. Under the D1 density, compared with the Se0, the dry matter mass of the Se1, Se2, Se3, and Se4 treatments significantly improved by 5.84%, 1.49%, and 14.26% in 2021, and significantly improved by 4.84%, 3.50%, and 2.85% in 2022. The 1000-grain weight under Se2, Se3, and Se4 treatments improved by 8.57%, 9.06%, and 15.56% compared to that under the Se0 treatment, and the yield per ha under the Se2, Se3, and Se4 treatments was 18.58%, 9.09%, and 21.42% higher than that under Se0 treatment, respectively. In addition, a reasonable combination of selenium application rate and density could improve the chlorophyll content and stem growth of dryland maize. This lays a foundation for the efficient application of selenium fertilizer and provides an important reference.

Comprehensive evaluation of factors influencing selenium fertilization biofortification

BACKGROUND

Dietary selenium (Se) deficiency, stemming from low Se concentrations in agricultural products, threatens human health. While Se-containing fertilizers can enhance the Se content in crops, the key factors governing Se biofortification with Se fertilization remain unclear.

RESULTS

This study constructed a global meta-analysis dataset based on field experiments comprising 364 entries on Se content in agricultural products and 271 entries on their yield. Random forest models and mixed effects meta-analyses revealed that plant types (i.e., cereals, vegetables, legumes, and forages) primarily influenced Se biofortification, with Se fertilization rates being the next significant factor. The random forest model, which included variables like plant types, Se fertilization rates, methods and types of Se application, initial soil conditions (including Se content, organic carbon content, and pH), soil types, mean annual precipitation, and temperature, explained 82.14% of the variation in Se content and 48.42% of the yield variation in agricultural products. For the same agricultural products, the increase in Se content decreased with higher rates of Se fertilization. The increase in Se content in their edible parts will be negligible for cereals, forages, legumes, and vegetable crops, when Se fertilization rates were 164, 103, 144, and 147 g Se ha-1 , respectively. Conversely, while low Se fertilization rates enhanced yields, high rates led to a yield reduction, particularly in cereals.

CONCLUSION

Our findings highlight the need for balanced and precise Se fertilization strategies to optimize Se biofortification benefits and minimize the risk of yield reduction. © 2024 Society of Chemical Industry.

Selenium volatilization in plants, microalgae, and microorganisms

The augmented prevalence of Se (Se) pollution can be attributed to various human activities, such as mining, coal combustion, oil extraction and refining, and agricultural irrigation. Although Se is vital for animals, humans, and microorganisms, excessive concentrations of this element can give rise to potential hazards. Consequently, numerous approaches have been devised to mitigate Se pollution, encompassing physicochemical techniques and bioremediation. The recognition of Se volatilization as a potential strategy for mitigating Se pollution in contaminated environments is underscored in this review. This study delves into the volatilization mechanisms in various organisms, including plants, microalgae, and microorganisms. By assessing the efficacy of Se removal and identifying the rate-limiting steps associated with volatilization, this paper provides insightful recommendations for Se mitigation. Constructed wetlands are a cost-effective and environmentally friendly alternative in the treatment of Se volatilization. The fate, behavior, bioavailability, and toxicity of Se within complex environmental systems are comprehensively reviewed. This knowledge forms the basis for developing management plans that aimed at mitigating Se contamination in wetlands and protecting the associated ecosystems.

Influencing factors of selenium transformation in a soil-rice system and prediction of selenium content in rice seeds: a case study in Ninghua County, Fujian Province

Selenium (Se) is an essential element for human and animal health and has antioxidant, anticancer, and antiviral effects. However, more than 100 million people in China do not have enough Se in their diets, resulting in a state of low Se in the human body. Since the absorption of Se by crop seeds depends not only on the Se content in soil, there are many omissions and misjudgments in the division of Se-rich producing areas. Soil pH, total iron oxide content (TFe2O3), soil organic matter (SOM), and P and S contents were the main factors affecting Se migration and transformation in the soil-rice system. In this study, we compared the performance of the back propagation neural network (BP network) and multiple linear regression (MLR) using 177 pairs of soil-rice samples. Our results showed that the BP network had higher accuracy than MLR. The accuracy and precision of the prediction data met the requirements, and the prediction data were reliable. Based on the Se data of surface paddy fields, 26,900 ha of Se-rich rice planting area was planned using this model, accounting for 77% of the paddy field area. In the planned Se-rich area for rice, the proportion of soil Se content greater than 0.4 mg·kg-1 was only 5.29%. Our research is of great significance for the development of Se-rich lands.

A novel slow-release selenium approach for cadmium reduction and selenium enrichment in rice (Oryza sativa L.)

In this study, a novel slightly-soluble selenium (Se) fertilizer (SSF) was successfully applied to address the problems of Cd pollution in paddy soil and rice, and Se deficiency in human beings. The pot and field experiments showed that Cd content in the rice grains was reduced by 48.4%-82.89% and Se content was increased nearly by 30-fold comparing the control group. The application of SSF increased the soil pH and significantly reduced the DGT-extracted Cd in the soil. Moreover, DCB-extractable Fe content on the surface of roots was prompt by SSF, which formed a physical barrier, namely iron plaque (IP), to inhibit Cd translocation to the above-ground tissues of the rice plants. The Cd content in the IP was also decreased before the filling period, possibly contributing to the reduction in major Cd accumulation in the rice grains. In addition, the continuous Se increase and Cd reduction in the IP by the SSF gradually exceeded that of water-soluble Se during the three periods of rice plant growth. This suggests that SSF has high potential to be an effective Se fertilizer for inhibiting Cd uptake and enriching Se in rice.

Direct immobilization of Se(IV) from acidic Se(IV)-rich wastewater via ferric selenite Co-precipitation

The attenuation of acidic Se(IV)-rich wastewater, including those associated with acid mine drainage (AMD) and nonferrous metallurgical wastewater (NMW), presents a serious environmental challenge. This study investigates the effects of diverse factors from pH values to Se(IV)/Fe(III) molar ratios, initial Se(IV) concentrations, and alkali neutralization agents on the direct co-precipitation of ferric selenites in AMD and NMW systems involving different orders of Fe(III) and alkali addition. Our results show that amorphous sulfate-substituted ferric (hydrogen) selenite and Se(IV)-bearing ferrihydrite-schwertmannite are the major Se(IV)-attenuation solids except that gypsum is an additional phase in the NMW system with Ca(OH)2 neutralization. Produced ferric selenites achieve 98-99.8% of Se(IV) immobilization under optimal conditions of pH 4.5, Se(IV)/Fe(III) molar ratios of 0.0625-0.5, and initial Se(IV) concentrations of 0.15-1.3 mmol·L-1. Moreover, completing FeSO4+ and FeHSeO32+/FeSeO3+ complexes as well as different ferric selenite co-precipitates are shown to collectively control aqueous Se(IV) remaining. Specifically, three distinct trends of aqueous Se(IV) concentrations separately correspond to changes in the four factors. The co-precipitation in the NMW system via pH adjustment followed by Fe(III) addition is more efficient for Se(IV) fixation than that in the AMD system because of minimal complexation, concurrent Fe(III) hydrolysis, and enhanced ferric selenite co-precipitation in the former.

Toxicity monitoring signals analysis of selenite using microbial fuel cells

Microbial fuel cells (MFCs) based biosensors are widely studied to environmental monitoring. The suitable responsive signal is important for microbial electrochemical sensors. However, the responsive signals of toxins have not been investigated in detail. Using sodium selenite as a toxic substance, the different response signals are analyzed over a concentration range from 0 to 150 mg/L in the double chambered. The output voltage and power density had the opposite trend between 0 and 2.5 mg/L and 2.5-150 mg/L. To analyze the reasonable signal of Se(IV) monitoring sensor, correlation analysis of concentrations and responsive signal data (maximum voltage, maximum power density, coulombic recovery, coulombic efficiency, and normalized energy recovery, etc.) has been accomplished. The high concentration of exogenous selenite (2.5-100 mg/L) is negatively correlated with maximum voltage (r = -0.901, p < 0.01) and max power density (r = -0.910, p < 0.01). The low concentration of exogenous selenite is positively correlated with average voltage, max power density, coulombic yield (r = 0.973, 0.999 and 0.975, respectively. p < 0.05). Furthermore, Illumina sequencing results indicate that the addition of sodium selenite solution changes the anode community structure, thereby affecting the removal efficiency of organic matter, which may be the reason why coulombic efficiency and normalized energy recovery are not suitable as sensing signal. Overall, based on the analysis of experimental data, the maximum power density is the best response signal, which provides a reference for the selection of sensor response signal based on microbial fuel cells.

Selenium Species and Fractions in the Rock-Soil-Plant Interface of Maize (Zea mays L.) Grown in a Natural Ultra-Rich Se Environment

Selenium (Se) enrichments or deficiency in maize (Zea mays L.), one of the world's most important staple foods and livestock feeds, can significantly affect many people's diets, as Se is essential though harmful in excess. In particular, Se-rich maize seems to have been one of the factors that led to an outbreak of selenosis in the 1980s in Naore Valley in Ziyang County, China. Thus, this region's geological and pedological enrichment offers some insight into the behavior of Se in naturally Se-rich crops. This study examined total Se and Se species in the grains, leaves, stalks, and roots of 11 maize plant samples, Se fractions of soils around the rhizosphere, and representative parent rock materials from Naore Valley. The results showed that total Se concentrations in the collected samples were observed in descending order of soil > leaf > root > grain > stalk. The predominant Se species detected in maize plants was SeMet. Inorganic Se forms, mainly Se(VI), decreased from root to grain, and were possibly assimilated into organic forms. Se(IV) was barely present. The natural increases of Se concentration in soils mainly affected leaf and root dry-weight biomasses of maize. In addition, Se distribution in soils markedly correlated with the weathered Se-rich bedrocks. The analyzed soils had lower Se bioavailability than rocks, with Se accumulated predominantly as recalcitrant residual Se. Thus, the maize plants grown in these natural Se-rich soils may uptake Se mainly from the oxidation and leaching of the remaining organic-sulfide-bound Se fractions. A viewpoint shift from natural Se-rich soils as menaces to possibilities for growing Se-rich agricultural products is also discussed in this study.

Effects of Basal Selenium Fertilizer Application on Agronomic Traits, Yield, Quality, and Se Content of Dryland Maize

To explore the efficiency of selenium (Se) fertilizer application in dryland maize, we tested five Se fertilizer application treatments: 0 g ha^-1 (Se0), 75 g ha^-1 (Se1), 150 g ha^-1 (Se2), 225 g ha^-1 (Se3), and 300 g ha^-1 (Se4). Compared with Se0, Se2 increased the leaf area, chlorophyll content, internode length, plant height, and ear height by 7.95%, 3.20%, 13.19%, 1.89%, and 7.98%, respectively. Se2 and Se3 significantly affected the stem internode diameter, cortex thickness, and cellulose content, which were positively correlated with lodging resistance. Compared with Se0, Se3 promoted the contents of soluble sugar, crude protein, crude fat, and starch in grains, which increased by 9.48%, 6.59%, 1.56%, and 4.82%, respectively. It implies that maize grain application of Se significantly improves their Se content. Se1 did not observably influence the growth of maize, and the promoting effect of Se4 on maize decreased. The lodging resistance of maize as analyzed by Pearson correlation analysis correlated with the application of Se fertilizer. It proved that higher yield, grain quality, grain Se content, and lodging resistance of stems were concerned with Se fertilizer application in the range of 150-225 g ha^-1. The results provide useful information for Se fertilizer treatment in dryland maize.

The importance and status of the micronutrient selenium in South Africa: a review

Selenium (Se) is a vital micronutrient with widespread biological action but leads to toxicity when taken in excessive amounts. The biological benefits of Se are mainly derived from its presence in active sites of selenoproteins such as glutathione peroxidase (GPx). An enzyme whose role is to protect tissues against oxidative stress by catalysing the reduction of peroxidase responsible for various forms of cellular damage. The benefits of Se can be harvested when proper regulations of its intake are used. In South Africa, Se distribution in people's diets and animals are low with socio-economic factors and heterogeneous spread of Se in soil throughout the country playing a significant role. The possible causes of low Se in soils may be influenced by underlying geological material, climatic conditions, and anthropogenic activities. Sedimentary rock formations show higher Se concentrations compared to igneous and metamorphic rock formations. Higher Se concentrations in soils dominates in humid and sub-humid areas of South Africa. Furthermore, atmospheric acid deposition dramatically influences the availability of Se to plants. The studies reviewed in this article have shown that atomic absorption spectroscopy (AAS) is the most utilised analytical technique for total Se concentration determination in environmental samples and there is a lack of speciation data for Se concentrations. Shortcomings in Se studies have been identified, and the future research directions of Se in South Africa have been discussed.

Selenium distribution in cultivated Argosols and Gleyosols of dry and paddy lands: A case study in Sanjiang Plain, Northeast China

Distribution pattern of selenium (Se) fractions in soil could influence Se content in crops and thereby intake of Se in human body. In order to investigate the effects of soil types and farming conditions on Se distribution in small-scaled cultivated land developed under the same conditions of climate, topography and parent materials, two types of soils (i.e., Argosols and Gleyosols) from paddy and dry lands in the Sanjiang Plain of Northeast China were selected. Total Se (T-Se) content in Argosols was influenced by organic carbon (Org C) content and pH of bulk topsoil. In Gleyosols, it was mainly affected by Org C content in dry land and pH in paddy land, respectively. In rice root associated topsoil, organic matter associated Se (OM-Se) accounted for 70% of T-Se. Compared with pH (median 6.10) and OM weakly bound Se (OW-Se) (0.14 ± 0.04 mg kg^-1) of Argosols, the higher pH (median 6.77) resulted in less OW-Se (0.10 ± 0.04 mg kg^-1) of Gleyosols. Vertical distribution of Se in borehole cores within the depth of 0-900 cm was mainly affected by the soil type. Se accumulated mainly within 0-150 cm depth (horizon A, E and B) in Argosols and above 40 cm depth (horizon H), existing prominently as OM strongly bound Se (OS-Se), in Gleyosols. Within the depth of 0-150 cm, various Se fractions for both soils were probably controlled by reductive fixation and complexation of Org C; In the alkaline paddy land, DOM-complexed Se was the main composition of A-Se. The findings of this study could help in understanding the mechanisms of Se distribution and enrichment in soils developed under different formation processes and farming conditions.

Geochemistry of selenium, barium, and iodine in representative soils of the Brazilian Amazon rainforest

The Amazon rainforest is a heterogeneous ecosystem and its soils exhibit geographically variable concentrations of trace elements. In this region, anthropic activities - e.g., agriculture and mining - are numerous and varied, and even natural areas are at risk of contamination by trace elements, either of geogenic or anthropogenic origin. A reliable dataset of benchmark values for selenium (Se), barium (Ba), and iodine (I) concentrations in soils is needed for use as a reference in research and public policies in the region. In this study, 9 selected sites in the Brazilian Amazon rainforest within areas represented by Oxisols and Ultisols were assessed for relevant soil physicochemical characteristics, along with the concentrations of total Se (Se_Tot), total Ba (Ba_Tot), and sequentially-extracted soluble Se (Se_Sol) and adsorbed Se (Se_Ad) in 3 different soil layers (0-20, 20-40, and 40-60 cm). In addition, organically bound-Se (Se_Org) and total I (I_Tot) concentrations in the surface layer (0-20 cm) were measured. Soil Se concentrations (Se_Tot) were considered safe and are likely a result of contributions of sedimentary deposits from the Andes. Available Se (Se_Sol + Se_Ad) accounted for 4.5% of Se_Tot, on average, while Se_Org in the topsoil accounted for more than 50% of Se_Tot. Barium in the western Amazon (state of Acre) and central Amazon (Anori, state of Amazonas) exceeded national prevention levels (PVs). Furthermore, the average I_Tot in the studied topsoils (5.4 mg kg^-1) surpassed the worldwide mean. Notwithstanding, the close relationship found between the total content of the elements (Se, Ba, and I) and soil texture (clay, silt, and sand) suggests their geogenic source. Finally, our data regarding Se_Tot, Ba_Tot, and I_Tot can be used to derive regional quality reference values for Amazon soils and also for updating prevention (PV) and investigation (IV) values established for selected elements by the Brazilian legislation.

Materials interacting with inorganic selenium from the perspective of electrochemical sensing

Inorganic selenium, the most common form of harmful selenium in the environment, can be determined using electrochemical sensors, which are compact, fast, reliable and easy-to-operate devices. Despite progress in this area, there is still significant room for developing high-performance selenium electrochemical sensors. To achieve this, one should take into account (i) the electrochemical process that selenium undergoes on the electrode; (ii) the valence state of selenium species in the sample and (iii) modification of the sensor surface by a material with high affinity to selenium. The goal of this review is to provide a knowledge base for these issues. After the Introduction section, mechanisms and principles of the electrochemical reduction of selenium are introduced, followed by a section introducing the modification of electrodes with materials interacting with selenium and a section dedicated to speciation methods, including the reduction of non-detectable Se(VI) to detectable Se(IV). In the following sections, the main types of materials (metallic, polymers, hybrid (nano)materials…) interacting with inorganic selenium (mostly absorbents) are reviewed to show the diversity of properties that may be endowed to sensors if the materials were to be used for the modification of electrodes. These features for the main material categories are outlined in the conclusion section, where it is stated that the engineered polymers may be the most promising modifiers.

Application of sodium selenate to cowpea (Vigna unguiculata L.) increases shoot and grain Se partitioning with strong genotypic interactions

BACKGORUND

Cowpea is a crop widely used in developing countries due its rusticity. Besides its rich genotypic variability, most breeding programs do not explore its potential to improve elements uptake. Selenium (Se) is a scarce element in most soils, resulting in its deficiency being common in human diets. This study aimed to evaluate the interaction between biofortification with Se and genotypic variation in cowpea, on the concentrations of Se in roots, leaves + stem and grains.

METHODS

Twenty-nine cowpea genotypes were grown in a greenhouse in the absence (control) and presence of Se (12.5 μg Se kg^-1 soil) as sodium selenate, in fully randomized scheme. The plants were cultivated until grains harvest. The following variables were determined: roots dry weight (g), leaves + stems dry weight (g), grains dry weight (g), Se concentration (mg kg^-1) in roots, leaves + stems and grains, and Se partitioning to shoots and grains.

RESULTS

Selenium application increased the Se concentration in roots, leaves + stems and grains in all genotypes. At least twofold variation in grain Se concentration was observed among genotypes. Selenium application did not impair biomass accumulation, including grain dry weight. Genotype "BRS Guariba" had the largest Se concentration in grains and leaves + stems. Genotype MNC04-795 F-158 had the largest partitioning of Se to shoots and grain, due to elevated dry weights of leaves + stems and grain, and high Se concentrations in these tissues.

CONCLUSION

This information might be valuable in future breeding programs to select for genotypes with better abilities to accumulate Se in grain to reduce widespread human Se undernutrition.

Selenium Biofortification: Roles, Mechanisms, Responses and Prospects

The trace element selenium (Se) is a crucial element for many living organisms, including soil microorganisms, plants and animals, including humans. Generally, in Nature Se is taken up in the living cells of microorganisms, plants, animals and humans in several inorganic forms such as selenate, selenite, elemental Se and selenide. These forms are converted to organic forms by biological process, mostly as the two selenoamino acids selenocysteine (SeCys) and selenomethionine (SeMet). The biological systems of plants, animals and humans can fix these amino acids into Se-containing proteins by a modest replacement of methionine with SeMet. While the form SeCys is usually present in the active site of enzymes, which is essential for catalytic activity. Within human cells, organic forms of Se are significant for the accurate functioning of the immune and reproductive systems, the thyroid and the brain, and to enzyme activity within cells. Humans ingest Se through plant and animal foods rich in the element. The concentration of Se in foodstuffs depends on the presence of available forms of Se in soils and its uptake and accumulation by plants and herbivorous animals. Therefore, improving the availability of Se to plants is, therefore, a potential pathway to overcoming human Se deficiencies. Among these prospective pathways, the Se-biofortification of plants has already been established as a pioneering approach for producing Se-enriched agricultural products. To achieve this desirable aim of Se-biofortification, molecular breeding and genetic engineering in combination with novel agronomic and edaphic management approaches should be combined. This current review summarizes the roles, responses, prospects and mechanisms of Se in human nutrition. It also elaborates how biofortification is a plausible approach to resolving Se-deficiency in humans and other animals.

Application of Fe-biochar composites for selenium (Se+6) removal from aqueous solution and effect of the presence of competing anions under environmentally relevant conditions

This study's aim was to compare biochar and steam activated biochar functionalized with iron for removal of selenium as selenate from solutions also containing nitrate and sulfate. The Fe-biochar composites were made impregnating iron (ferric nitrate) onto regular biochar (RB) and steam activated biochar (SAB), forming the Fe-biochar composites FeRB and FeSAB. Iron oxyhydroxide deposits were observed on the surface of FeRB using Raman spectroscopy analysis, but not on the FeSAB surface. Unmodified biochar samples did not remove selenium, as Se(VI), from solution, whereas FeRB and FeSAB recovered 8.3 mg-Se⋅g-composite^-1 and 5.9 mg-Se⋅g-composite^-1, respectively. Higher Se uptake was achieved at higher Fe-loads and lower acetone:biochar ratio, to a maximum of 17.3 mg-Se⋅g-composite^-1 (FeRB). Washing after Fe-impregnation using deionized water diminished nitrate and Fe-leaching from the Fe-biochar composites while removing selenium. Se(VI) and sulfate uptake were observed when washed composites were tested in the presence of possible competing ions at environmentally relevant concentrations ([Se]_t=0 = 1.01 ± 0.03 mg⋅L^-1; [N-NO₃^-]_t=0 = 40.2 ± 0.2 mg⋅L^-1; and [SO₄^2-]_t=0 = 496 ± 25 mg⋅L^-1). One of the possible mechanisms of removal might be the complexation of Se with the iron oxyhydroxide deposits (goethite and hematite) found on the FeRB surface.

Selenium and Nano-Selenium Biofortification for Human Health: Opportunities and Challenges

Selenium is an essential micronutrient required for the health of humans and lower plants, but its importance for higher plants is still being investigated. The biological functions of Se related to human health revolve around its presence in 25 known selenoproteins (e.g., selenocysteine or the 21st amino acid). Humans may receive their required Se through plant uptake of soil Se, foods enriched in Se, or Se dietary supplements. Selenium nanoparticles (Se-NPs) have been applied to biofortified foods and feeds. Due to low toxicity and high efficiency, Se-NPs are used in applications such as cancer therapy and nano-medicines. Selenium and nano-selenium may be able to support and enhance the productivity of cultivated plants and animals under stressful conditions because they are antimicrobial and anti-carcinogenic agents, with antioxidant capacity and immune-modulatory efficacy. Thus, nano-selenium could be inserted in the feeds of fish and livestock to improvise stress resilience and productivity. This review offers new insights in Se and Se-NPs biofortification for edible plants and farm animals under stressful environments. Further, extensive research on Se-NPs is required to identify possible adverse effects on humans and their cytotoxicity.

Determination of the geographical origin of maize (Zea mays L.) using mineral element fingerprints

BACKGROUND

Maize (Zea mays L.) is a staple cereal crop and feed crop throughout the world. In this article, a mineral element fingerprinting technique was applied to single out suitable element indicators to determine the geographical origin of maize. A total of 90 fresh maize samples were collected in 2107 from Jilin, Gansu, and Shandong provinces in China. The contents of 25 mineral elements in all maize samples were measured by inductively coupled plasma mass spectrometry (ICP-MS). The composition of mineral elements was analyzed by multivariate statistical analysis, including one-way analysis of variance (one-way ANOVA), principal component analysis (PCA), k-nearest neighbor (KNN) analysis, and stepwise linear discriminant analysis (SLDA).

RESULTS

As compared by one-way ANOVA, the contents of 19 mineral elements in maize samples were significantly different among three provinces. Principal component analysis based on these 19 elements could obtain preliminary visual classification groups of maize samples. K-nearest neighbor analysis produced a total correct classification rate of 83.9% on the training set, and 82.2% on the prediction set. The SLDA model, based on eight indicative elements (Na, Cr, Rb, Sr, Mo, Cs, Ba, and Pb) obtained a total correct classification rate of 92.2% with cross-validation.

CONCLUSION

The mineral element fingerprinting technique combined with multivariate statistical analysis could be a helpful method to identify the geographical origin of maize. © 2019 Society of Chemical Industry.

Selenium biofortification in the 21st century: status and challenges for healthy human nutrition

BACKGROUND

Selenium (Se) is an essential element for mammals and its deficiency in the diet is a global problem. Plants accumulate Se and thus represent a major source of Se to consumers. Agronomic biofortification intends to enrich crops with Se in order to secure its adequate supply by people.

SCOPE

The goal of this review is to report the present knowledge of the distribution and processes of Se in soil and at the plant-soil interface, and of Se behaviour inside the plant in terms of biofortification. It aims to unravel the Se metabolic pathways that affect the nutritional value of edible plant products, various Se biofortification strategies in challenging environments, as well as the impact of Se-enriched food on human health.

CONCLUSIONS

Agronomic biofortification and breeding are prevalent strategies for battling Se deficiency. Future research addresses nanosized Se biofortification, crop enrichment with multiple micronutrients, microbial-integrated agronomic biofortification, and optimization of Se biofortification in adverse conditions. Biofortified food of superior nutritional quality may be created, enriched with healthy Se-compounds, as well as several other valuable phytochemicals. Whether such a food source might be used as nutritional intervention for recently emerged coronavirus infections is a relevant question that deserves investigation.

Selenium maintains cytosolic Ca2+ homeostasis and preserves germination rates of maize pollen under H2O2-induced oxidative stress

Selenium (Se) displays antioxidant properties that can be exploited, in plants, to counteract abiotic stresses caused by overly-produced reactive oxygen species (ROS). Here, we show that fertigation of maize crops with sodium selenate effectively protects pollen against oxidative stress. Pollen isolated from Se-treated plants (Se1) and untreated controls (Se0) was incubated in vitro with H₂O₂ to produce oxidative challenge. Given the impact of ROS on Ca²⁺ homeostasis and Ca²⁺-dependent signaling, cytosolic Ca²⁺ was measured to monitor cellular perturbations. We found that H₂O₂ disrupted Ca²⁺ homeostasis in Se0 pollen only, while Se1 samples were preserved. The same trend was observed when Se0 samples were treated with sodium selenate or Se-methionine, which recapitulated in vitro the protective capacity of Se-fertigation. Furthermore, we found that germination rates were much better retained in Se1 as compared to Se0 (46% vs 8%, respectively) after exposure to 20 mM H₂O₂. The same was observed with Se0 pollen treated with Se-methionine, which is the organic form of Se into which most fertigated sodium selenate converts in the plant. These results, together, show a close correlation between ROS, Ca²⁺ homeostasis and pollen fertility, and provide strong evidence that Se-fertigation is an excellent approach to preserve or enhance agricultural productivity.

Zea mays L. Grain: Increase in Nutraceutical and Antioxidant Properties Due to Se Fortification in Low and High Water Regimes

This work aimed to investigate the effect of selenium (Se) and irrigation on the grain yield, on the forms of Se, phenols, and carotenes, and on some antioxidant activities of maize ( Zea mays L.) grains. To reach this goal, a 2 year experiment was undertaken. Maize was fertigated with sodium selenite at the rate of 200 g of Se ha^-1 and grown under two water regimes. While the irrigation did not show a clear effect on the selected parameters, Se fertigation increased the contents of inorganic and organic Se forms, xanthophyll, and salicylic acid. Furthermore, while Se fertigation decreased the hydroxycinnamic acid content, generally higher antioxidant activities were found in Se-treated grains than in the control. These findings suggest that Se fertigation increases most of the nutraceutical values of maize grains, which therefore might improve human and livestock health and could increase the maize grain shelf life and its byproducts.