Se Accumulation Research Articles

Emerging evidence on selenoneine and its public health relevance in coastal populations: a review and case study of dietary Se among Inuit populations in the Canadian Arctic.

Selenium is an essential mineral yet both deficiency and excess are associated with adverse health effects. Dietary intake of Se in humans varies greatly between populations due to food availability, dietary preferences, and local geological and ecosystem processes impacting Se accumulation into agricultural products and animal populations. We argue there is a need to evaluate and reconsider the relevance of public health recommendations on Se given recent evidence, including the metabolic pathways and health implications of Se. This argument is particularly pertinent for Inuit populations in Northern Canada, who often exceed dietary tolerable upper intake levels and exhibit very high whole blood Se concentrations due to their dependence on local country foods high in the newly discovered Se compound, selenoneine. Since selenoneine appears to have lower toxicity compared to other Se species and does not contribute to the circulating pools of Se for selenoprotein synthesis, we argue that total dietary Se or total Se in plasma or whole blood are poor indicators of Se adequacy for human health in these populations. Overall, this review provides an overview of the current evidence of Se speciation, deficiency, adequacy, and excess and implications for human health and dietary recommendations, with particular reference to Inuit populations in the Canadian Arctic and other coastal populations consuming marine foods.

Synergistic Effects of Bicarbonate and Selenium on Cadmium Transport in Karst-Adaptable Plants Based on Plant Electrical Signals

High cadmium (Cd) concentrations associated with geochemical anomalies are prevalent in carbonate-rich karstic areas, posing serious ecological risks, while the karstic soils are rich in bicarbonate (HCO3−). It is known that Selenium (Se) is a mineral element that effectively mitigates the Cd transport in plant species. However, the synergistic effects of HCO3− and Se on Cd translocation in plant species have not yet been indicated. In this study, based on plant electrophysiological measurements, we chose Orychophragmus violaceus (Ov) as experimental material and determined the growth potential, water metabolism, and nutrient translocation capacity under HCO3−-Se6+-Cd2+ treatment to identify the synergistic effects of bicarbonate and selenium on cadmium transport in karst-adaptable plants. We found 5 mM HCO3− and 0.46 mM Se6+ synergistically alleviated the Cd2+ stress on Ov, promoting growth, intracellular water metabolism, nutrient translocation efficiency, and total Se accumulation, and inhibiting the uptake of Cd in Ov. Nevertheless, 15 mM HCO3− and 0.46 mM Se6+ synergistically augmented Cd transport on Ov, resulting in growth reduction, intracellular water metabolism, nutrient translocation efficiency, and total Se concentration. Hence, it not only provides a frontier approach for the real-time monitoring of intracellular water and nutrient utilization capacity in plant species, but is also even more a theoretical idea that reveals the synergistic effects of bicarbonate and selenium on cadmium transport of plants to precisely indicate selenium supplementation to ameliorate cadmium pollution and construct a sustainable karst ecosystem in the future.

Selenium and Heavy Metals in Soil–Plant System in a Hydrogeochemical Province with High Selenium Content in Groundwater: A Case Study of the Lower Dniester Valley

The bioaccumulation of selenium (Se) and heavy metals (HMs) in plants is important because it can affect plant health and human nutrition. Recognizing the factors affecting Se accumulation in plants may have important implications for agricultural practices and human health in selenium-rich regions. The study primarily focused on the interactions between Se and HMs in the soil–plant system of the Lower Dniester Valley. Total concentrations of HMs (Cu, Mn, Zn) were determined by atomic absorption spectrometry, while Se concentrations were determined by a sensitive single-test-tube fluorometric method in solutions and extracts. Water-soluble Se (0.09 ± 0.03 mg·kg−1) in soils was 32.1% of the total Se (0.33 ± 0.13 mg·kg−1) and increased with the total rising Se content (r = 0.845). The results indicated that plants had a greater Zn accumulation capacity than that of the other HMs, suggesting its importance as a trace element for plant requirements. Se also had a high bioaccumulation rate. Se and Zn accumulation varied in different soil types, reflecting differences in bioavailability. In contrast, Mn and Cu showed low bioaccumulation, which varied with soil conditions and anthropogenic Cu pollution. Despite the Cu contamination of the soils in the investigated region, it can be inferred that the hydrogeochemical province with high Se content in groundwater has favorable conditions for Se mobilization in soils. The absence of antagonistic interactions with HMs in the soil–plant system contributes to the enhanced Se accumulation in plants in the Lower Dniester Valley. These results emphasize the complexity of the interactions between Se and HMs in the soil–plant system and their potential impact on agricultural practices.

Assessment of some toxic elements (Co, Cr, Mn, Se, and As) in muscle, offal, hair, and blood of camels (Camelus dromedaries) and their risk assessment.

Camel meat tainted with heavy metals or trace elements may pose a health risk to consumers. Heavy metal contamination poses a severe danger due to both their toxicity and bioaccumulation in the food chain. To estimate the residual levels of heavy metals (Co, Cr, Mn, Se, and As) in muscle, liver, kidney, hair, and serum of three camel breeds (Magaheem, Maghateer, and Wadha) collected from Al-Omran abattoir, Al-Ahsa, Saudi Arabia. A total of 225 tissue samples (muscles, liver, kidney, serum, and hair) were taken and analyzed using an Atomic Absorption Spectrophotometer. Health risk assessment was assessed using the guidelines set by the US Environmental Protection Agency. Camel breed significantly (p < 0.05) influences Co, Cr, Mn, and Se accumulation and distribution in organs and muscle; however, arsenic accumulation was not significantly affected (p < 0.05) by camel breeds. The highest values of Co, Cr, Se, and Mn in all examined samples were detected in the liver samples of Maghateer and Magaheem breeds. Furthermore, significant strong positive correlation between serum and liver cobalt, chromium, manganese, and arsenic. The estimated daily intake owing to camel meat consumption was less than the tolerated daily intake. Heavy metals were distributed among different breeds of camel. Trace elements (Pb and Cd) in meat and offal were below the international maximum permissible limit. The correlation between samples reflects the role of hair as a good tool for the identification of heavy metal pollution.

Factors controlling accumulation and bioavailability of selenium in paddy soils: A case study in Luxi County, China

Selenium (Se) accumulation in rice (Oryza sativa L.) has become a major global concern. Se offers multiple health benefits in humans; however, its inadequate or excessive intake can be harmful. Therefore, determining the factors driving Se abundance and bioavailability in paddy soils is essential to ensure the safety of human Se intake. This study investigated the accumulation, bioavailability, and distribution of Se in 820 paddy soil and rice grain samples from Luxi County, China to assess how soil properties (soil organic matter [SOM], cation exchange capacity [CEC], and pH), geographical factors (parent materials, elevation, and mean annual precipitation [MAP] and temperature [MAT]), and essential micronutrients (copper [Cu], zinc [Zn], and manganese [Mn]) govern Se accumulation and bioavailability in paddy soils. Results showed that the average soil Se content was 0.36 mg kg−1, which was higher than that in China (0.29 mg kg−1). Alternatively, the average rice grain Se content was 0.032 mg kg−1, which was lower than the minimum allowable content in Se-rich rice grains (0.04 mg kg−1). Five studied parent materials all had a significant effect on soil Se content but had little effect on Se bioavailability (p < 0.05). CEC, elevation, and SOM, as well as the soil contents of Cu, Zn, and Mn were positively correlated with soil Se content, but pH, MAP, and MAT were negatively correlated. Correspondingly, Se bioavailability was negatively correlated with SOM and soil Zn content, but positively correlated with MAP and grain contents of Cu, Zn, and Mn. Furthermore, partial least squares path analysis revealed the interactive impacts of the influencing factors on Se accumulation and bioavailability in soils. On this basis, prediction models were established to predict Se accumulation and bioavailability in paddy soils, thereby providing theoretical support for developing efficient control measures to meet Se challenges in agriculture.

Selenium biofortification improves bioactive composition and antioxidant status in Plantago ovata Forsk., a medicinal plant

BackgroundSelenium (Se) is an essential micronutrient for humans, but its deficiency as well as toxicity affects large number of people worldwide. Plantago ovata, a commercially important medicinal plant, is mainly cultivated in western regions of India, where elevated levels of Se have been found in soil. Thus, we evaluated the potential of Se biofortification in P. ovata via phytoremediation and its effect on the bioactive composition.ResultsThe results showed a significant alteration in various morphological and physiological parameters in a dose-dependent manner. The 10 µM Se dose improved seedling height, biomass and total chlorophyll content. There was a gradual increase in total Se content, with highest accumulation of 457.65 µg/g FW at 500 µM Se treatment. Se positively affected the antioxidative metabolism which was measured from the change in total antioxidant capacity, radical scavenging activity and Metallothionein 2 expression. Increasing levels of Se also affected the PAL activity, total polyphenol and flavonoid content. Caffeic acid, Coumaric acid and Rutin were found to be the most abundant phenolic compounds.ConclusionsLow levels of selenium (below 50 µM) can successfully improve Se accumulation and elicit production of various polyphenols without hampering plant growth. Thus, Se fortification of P. ovata seedlings via phytoremediation appears to be a feasible and efficient way to enhance its nutraceutical value in dietary products.

Agronomic and Genetic Strategies to Enhance Selenium Accumulation in Crops and Their Influence on Quality.

Selenium (Se) is an essential trace element that plays a crucial role in maintaining the health of humans, animals, and certain plants. It is extensively present throughout the Earth's crust and is absorbed by crops in the form of selenates and selenite, eventually entering the food chain. Se biofortification is an agricultural process that employs agronomic and genetic strategies. Its goal is to enhance the mechanisms of crop uptake and the accumulation of exogenous Se, resulting in the production of crops enriched with Se. This process ultimately contributes to promoting human health. Agronomic strategies in Se biofortification aim to enhance the availability of exogenous Se in crops. Concurrently, genetic strategies focus on improving a crop's capacity to uptake, transport, and accumulate Se. Early research primarily concentrated on optimizing Se biofortification methods, improving Se fertilizer efficiency, and enhancing Se content in crops. In recent years, there has been a growing realization that Se can effectively enhance crop growth and increase crop yield, thereby contributing to alleviating food shortages. Additionally, Se has been found to promote the accumulation of macro-nutrients, antioxidants, and beneficial mineral elements in crops. The supplementation of Se biofortified foods is gradually emerging as an effective approach for promoting human dietary health and alleviating hidden hunger. Therefore, in this paper, we provide a comprehensive summary of the Se biofortification conducted over the past decade, mainly focusing on Se accumulation in crops and its impact on crop quality. We discuss various Se biofortification strategies, with an emphasis on the impact of Se fertilizer strategies on crop Se accumulation and their underlying mechanisms. Furthermore, we highlight Se's role in enhancing crop quality and offer perspective on Se biofortification in crop improvement, guiding future mechanistic explorations and applications of Se biofortification.

The physiological responses of celery (Apium graveolens L.) and its ability to accumulate selenium when inoculated with Funneliformis mosseae

Celery (Apium graveolens L.) has a strong capacity to enrich selenium (Se) and is a good system for research on Se enrichment in vegetables. Arbuscular mycorrhizal fungi (AMF) are commonly used plant symbionts that affect plant growth and their effectiveness is plant species specific. However, there is little research on the effects of AMF inoculation on the accumulation and translocation of Se in celery. The treatments in this study included inoculation with AMF (+AMF) and the application of different types and concentrations of exogenous Se. We evaluated the growth, root mycorrhizal colonization, photosynthetic pigment content, ascorbate-glutathione cycle (ASA-GSH cycle), the accumulation and translocation of Se and the combination of AMF + Se compared with an untreated control. The application of low concentrations of Se (≤10 mg kg−1) stimulated celery growth, while high concentrations (>20 mg kg−1) had the opposite effect. The inhibition of celery growth was more severe with Se6+ than Se4+ when applied at the same concentration. The accumulation of Se improved in all the organs of celery as the supply increased. AMF had a significant positive effect on the accumulation and translocation of Se. In addition, +AMF significantly increased the shoot height and root fresh weight of celery and reduced the inhibitory effect of Se on growth. However, +AMF had slight effects on the levels of photosynthetic pigments and the ASA-GSH cycle. +AMF combined with 10 mg kg−1 sodium selenite (Se4+) is an effective way to produce Se-rich celery.

Spatial distribution and main drivers of soil selenium in Taihu Lake Basin, Southeast China

Selenium (Se) is an essential micronutrient that is both hazardous and beneficial to living organisms. However, few studies have examined soil Se distribution and its driving mechanisms on a large basin scale. Thus, multivariate statistics, geostatistics, boosted regression trees, and structural equation models were used to investigate the spatial distribution, driving factors, and multivariate interactions of soil Se based on 1753 topsoil samples (0–20 cm) from the Taihu Lake Basin. The results indicated that the soil Se concentration ranged from 0.12 to 57.26 mg kg−1, with a mean value of 0.90 mg kg−1. Overall, the spatial pattern of soil Se gradually decreased from south to north with approximately 1.06% of the soil contaminated with Se. Moisture index (MI), soil moisture (SM), and ≥ 0 ℃ accumulative temperature (AAT0) were the main determinants of soil Se accumulation. Additionally, the substantial effect of SM∩AAT0 on soil Se concentrations demonstrated that climate-soil interactions largely governed the spatial pattern of soil Se. The Se-enriched and Se-contaminated soils occurred mainly in regions with high precipitation, MI, SM, AAT0, and soil organic matter. This study provides a theoretical basis and practical guidance for the remediation of soil Se contamination and the sustainable development of Se-enriched agriculture.

Genome-Wide Identification of Selenium-Responsive MicroRNAs in Tea Plant (Camellia sinensis L. O. Kuntze)

Anadequate selenium (Se) intake can enhance human immunity and prevent diseases development. About one billion people in the world have varying degrees of Se deficiency in the world. Organic Se from tea infusion is the most easily absorbed and utilized Se form by the human body. Therefore the production of tea plants rich in Se is an effective way to increase Se dietary intake, but there are few studies on the involvement and functions of miRNAs in the responses of tea plants after Se treatment. MicroRNAs (miRNAs) are endogenous (non-coding) single-stranded RNAs that play crucial roles in regulating plant nutrient element acquisition and accumulation. Physiological analysis discovered that the total Se content in tea plant roots markedly increased under 0.05 mmol·L−1 selenite treatment, with no toxicity symptoms in the leaves and roots. To screen the miRNAs responsive to Se treatment in tea plants, miRNA libraries were constructed from the tea cultivar “Echa 1”. Using high-throughput sequencing, 455 known miRNAs and 203 novel miRNAs were identified in this study. In total, 13 miRNAs were selected that were differentially expressed in tea plants’ roots under 0.05 mmol·L−1 selenite treatments. Gene Ontology enrichment analysis revealed that the target genes of the differentially expressed miRNAs mainly belonged to the metabolic process, membrane, and catalytic activity ontologies. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis suggested that beta-alanine, taurine, hypotaurine, and sulfur metabolism were the most enriched pathways among the differentially expressed miRNAs, implying their involvement in Se accumulation and tolerance in tea plants. Further characterization of the data revealed that the number of novel miRNAs was comparable to that of known miRNAs, indicating that novel miRNAs significantly contributed to the regulation of Se accumulation in tea plant roots. Thisstudy lays the foundation for further research on the regulatory mechanisms underlying Se accumulation and tolerance in tea plants, providing targets to molecular breeding strategies for improving tea nutritional properties.

Environmental selenium and human longevity: An ecogeochemical perspective

Selenium (Se) has been called the “longevity element” by the scientific community because it has anti-cancer, anti-inflammatory, and anti-oxidant activity in humans. The geochemical properties and biological functions of Se have been widely studied in various fields, including geology, agriculture, and medicine. Bama Yao Autonomous County (Bama), a typical township in China with high longevity among the population, was selected as the research area. The present study organically combines the geological background, dietary structure, absorption and metabolism, and other biogeochemical aspects to comprehensively analyze the anti-aging properties of Se under high-Se conditions and a fiber-rich polysaccharide diet. Biogeochemical samples of surface soil, food, human hair, and urine were systematically collected from the environment and the residents, and the content and speciation of Se were analyzed. Concentrations of Se in the soil were moderate to high for Bama, with high-Se soil in 77.21% of the samples. Water-soluble Se concentrations were also high, 90% of the samples with moderate to high Se, and had a significant positive correlation with Se concentrations in crops. With both high total and high available Se, dietary samples from the study area showed Se-enriched characteristics. Accordingly, Se intake was also high (82.54 μg/d) in the population, strongly maintaining the normal bodily functions of the elderly. Accumulation and metabolism of Se in the population were assessed based on concentrations of Se in the hair and urine of residents over 60 years old. Continuous accumulation of Se was found to occur from 71 to 80 years of age. Concentrations of Se in residents under 71 years old and over 80 years old were in a state of loss. Overall, Se absorption and metabolism are maintained at the optimal physiological state, which is one of the primary factors maintaining the health and longevity of the elderly people in the study area.

Effects of foliar selenium application on Se accumulation, elements uptake, nutrition quality, sensory quality and antioxidant response in summer-autumn tea

Summer-autumn tea is characterized by high polyphenol content and low amino acid content, resulting in bitter and astringent teast. However, these qualities often lead to low economic benefits, ultimately resulting in a wastage of tea resources. The study focused on evaluating the effects of foliar spraying of glucosamine selenium (GLN-Se) on summer-autumn tea. This foliar fertilizer was applied to tea leaves to assess its impact on plant development, nutritional quality, elemental uptake, organoleptic quality, and antioxidant responses. The results revealed that GlcN-Se enhanced photosynthesis and yield by improving the antioxidant system. Additionally, the concentration of GlcN-Se positively correlated with the total and organic selenium contents in tea. The foliar application of GlcN-Se reduced toxic heavy metal content and increased the levels of macronutrients and micronutrients, which facilitated adaptation to environmental changes and abiotic stresses. Furthermore, GlcN-Se significantly improved both non-volatile and volatile components of tea leaves, resulting in a sweet aftertaste and nectar aroma in the tea soup. To conclude, the accurate and rational application of exogenous GlcN-Se can effectively enhance the selenium content and biochemical status of tea. This improvement leads to enhanced nutritional quality and sensory characteristics, making it highly significant for the tea industry.

Improving red pitaya fruit quality by nano-selenium biofortification to enhance phenylpropanoid and betalain biosynthesis

Red pitaya, the representative tropical and subtropical fruit, is vulnerable to quality deterioration due to climate or agronomic measures. Nano-selenium (Nano-Se) has shown positive effects on crop biofortification in favour of reversing this situation. In this study, Se could be enriched efficiently in red pitayas via root and foliar application by Nano-Se, which induced higher phenolic acids (16.9–94.2%), total phenols (15.7%), total flavonoids (29.5%) and betacyanins (34.1%) accumulation in flesh. Richer antioxidative features including activities of SOD (25.2%), CAT (33.8%), POD (77.2%), and levels of AsA (25.7%) and DPPH (14.7%) were obtained in Nano-Se-treated pitayas as well as in their 4–8 days shelf-life. The non-targeted metabolomics indicated a boost in amino acids, resulting in the stimulation of phenylpropanoid and betalain biosynthesis. In conclusion, the mechanism of Nano-Se biofortification for red pitaya might be fortifying pigment, as well as the enzymatic and non-enzymatic antioxidant substances formation by regulating primary and secondary metabolism facilitated by Se accumulation.

Selenomethionine supplementation and expression of selenosugars, selenocysteine, and other selenometabolites in rat liver.

Selenomethionine (SeMet) as a methionine analog can be incorporated into protein. In turkeys, we recently found that selenium (Se) as selenite is not metabolized to SeMet but rather to selenosugars (seleno-N-acetyl galactosamine) bound to protein as well as to selenocysteine (Sec) in selenoproteins. To characterize the metabolism of SeMet, we fed rats graded levels of SeMet from 0 to 5µg Se/g in a Se-deficient diet for 4 wk, and investigated the fate and accumulation of liver Se using high pressure liquid chromatography (HPLC) coupled with Se-specific inductively coupled plasma mass spectrometry (ICP-MS) and molecule specific (Orbitrap MS/MS) detection. Up to 0.24µg Se/g (Se requirement for maximal glutathione peroxidase activity), Sec accounted for ∼40% of total liver Se whereas SeMet only accounted for 3-11%. Analysis of water-soluble extracts found negligible low molecular weight (LMW) Se species in rats fed 0 and 0.08µg Se/g, including no SeMet. At 0.24µg Se/g and above, SeMet accounted for only 10% of LMW Se species, whereas methyl- and glutathionyl-selenosugars accounted for 70% of LMW Se species. Above the Se requirement, SeMet was ∼30% of the proteinaceous amino acids, whereas Sec levels fell to 5% in rats fed 5µg Se/g as SeMet. Last, considerably less inorganic Se was bound to liver protein with high SeMet as compared to selenite in a parallel study. SeMet is efficiently metabolized and mixes with the common Se metabolite pool, where Se is preferentially incorporated into Sec and Sec-selenoproteins until selenoproteins plateau; with high SeMet intake, Se is increasingly accumulated as LMW selenosugars and as selenosugar-decorated proteins.

Diversity of arbuscular mycorrhizal fungi in seleniferous soils and their role in plant growth promotion.

The present study aimed to investigate the molecular diversity of arbuscular mycorrhizal fungi (AMF) in natural seleniferous soils and their role in protecting plants from Se toxicity. The genomic DNA extracted from maize roots grown in seleniferous and non-seleniferous regions was amplified using AMF-specific primers by nested PCR. The 1.5kb amplicon spanning pSSU-ITS-pLSU of 18S rRNA of AMF was deciphered using the Illumina Miseq Next Generation Sequencing (NGS) technique. A total of 17 AMF species from the seleniferous region and 18 AMF species from the non-seleniferous region were identified. The number of reads of Glomus irregularis, G. custos, and G. intraradices was higher in seleniferous soil than in non-seleniferous soil, indicating their tolerance to Se. A consortium of Se-tolerant AMF inoculum was prepared and inoculated to maize plants, grown in natural seleniferous soils. AMF-inoculated plants had healthy growth with higher root, shoot, and grain biomass than non-AMF-inoculated plants. AMF inoculation leads to higher Se accumulation in roots but lesser Se accumulation in shoots and seeds of inoculated maize plants as compared to control plants. Present study results suggest that AMF species from seleniferous soils have the potential to be used as biofertilizers to improve plant growth and tolerate Se toxicity in seleniferous soils.

Intercropping with Solanum sect. Solanum (Solanaceae) increases selenium uptake of ‘Summer Black’ grapevine

AbstractTo improve the selenium (Se) absorption of grape, in this study, a pot experiment was carried out to study the effects of intercropping with four Solanum sect. Solanum (Solanaceae), including Solanum nigrum var. humile, Solanum diphyllum, Solanum nigrum, and Solanum alatum, on the Se absorption of ‘Summer Black’ grapevine. Intercropping increased the malondialdehyde contents in ‘Summer Black’ grapevine, which in turn reduced the biomass, photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoid) contents, and antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) activities of ‘Summer Black’ grapevine. Except S. alatum, intercropping with S. nigrum var. humile, S. diphyllum, and S. nigrum increased the Se content in ‘Summer Black’ grapevine, which increased the shoot Se content of ‘Summer Black’ grapevine by 56.2%, 18.1%, and 45.1%, respectively, compared with the monoculture. Additionally, correlation and grey relational analyses revealed that the root Se content was the most closely associated with the shoot Se content. In conclusion, intercropping with S. nigrum var. humile, S. diphyllum, and S. nigrum promote the Se accumulation in ‘Summer Black’ grapevine but inhibit its growth, and intercropping with S. nigrum var. humile has the best effect on the improvement of Se level in ‘Summer Black’ grapevine, which can be used for Se‐enriched grape production.

Water extract of Fagopyrum dibotrys (D. Don) Hara straw increases selenium accumulation in peach seedlings under selenium-contaminated soil

To promote the selenium (Se) uptakes in fruit trees under Se-contaminated soil, the effects of water extract of Fagopyrum dibotrys (D. Don) Hara straw on the Se accumulation in peach seedlings under selenium-contaminated soil were studied. The results showed that the root biomass, chlorophyll content, activities of antioxidant enzymes, and soluble protein content of peach seedlings were increased by the F. dibotrys straw extract. The different forms of Se (total Se, inorganic Se, and organic Se) were also increased in peach seedlings following treatment with the F. dibotrys straw extract. The highest total shoot Se content was treated by the 300-fold dilution of F. dibotrys straw, which was 30.87% higher than the control. The F. dibotrys straw extract also increased the activities of adenosine triphosphate sulfurase (ATPS), and adenosine 5'-phosphosulfate reductase (APR) in peach seedlings, but decreased the activity of serine acetyltransferase (SAT). Additionally, correlation and grey relational analyses revealed that chlorophyll a content, APR activity, and root biomass were closely associated with the total shoot Se content. Overall, this study shows that the water extract of F. dibotrys straw can promote Se uptake in peach seedlings, and 300-fold dilution is the most suitable concentration.

Life-cycle selenium accumulation and its correlations with the rhizobacteria and endophytes in the hyperaccumulating plant Cardamine hupingshanensis

Cardamine hupingshanensis (C. hupingshanensis) is known for its ability to hyperaccumulate selenium (Se). However, the roles of the rhizobacteria or endophytes in Se hyperaccumulation have not been explored in C. hupingshanensis. Here, in-situ-like pot experiments were conducted to investigate the characteristics of Se accumulation throughout C. hupingshanensis growth stages and its correlations with rhizobacteria and endophytes under varying soil Se levels. Results showed that Se levels in roots, stems and leaves increased from the seedling to bolting stage, but remained relatively stable during the flowering and maturity. Leaves exhibited the highest Se levels (736.48 ± 6.51 mg/kg DW), followed by stems (575.39 ± 27.05 mg/kg DW), and lowest in roots (306.62 ± 65.45 mg/kg DW) under high-Se stress. The Se translocation factors from soils to C. hupingshanensis roots was significantly higher (p < 0.05) in low-Se soils compared to medium- and high-Se soils. Rhizobacterial diversity showed significant positive correlations (p < 0.05) with both total and bioavailable soil Se contents. The levels of soil Se and growth stages of C. hupingshanensis were found to have significant effects (p < 0.03) on the compositions of rhizosphere bacteria and C. hupingshanensis endophytes. Low-abundance bacteria (< 5%), including Gemmatimonadetes, Latescibacteria and Nitrospirae, were identified to potentially increase the bioavailable Se levels in the rhizosphere. The Se accumulation significantly decreased (p < 0.05) in C. hupingshanensis grown in sterilized low- (32.4%), medium- (17%) and high-Se (42%) soils. Endophytes in C. hupingshanensis, such as Firmicutes and Proteobacteria, were likely recruited from the rhizobacteria, as evidenced by the isolated bacterial strains, and played an important role in Se hyperaccumulation, particularly during the flowering stage. This study provides new insights into potential mechanism underlying Se hyperaccumulation in C. hupingshanensis.

Isolation and identification of green alga Chlorella vulgaris HNUFU001 for environmental selenium enrichment in heterotrophic growth regime

Microalgae, particularly Chlorella, have promising selenium (Se) enrichment capacity and great potential in wastewater treatment and the development of nutraceuticals. To acquire Chlorella strains with strong heterotrophic propensity and robust Se tolerance, this research utilized a heterotrophic isolation strategy along with a high Se concentration medium as selection factors. The combined sequence of the ribosomal small subunit (SSU) and internal transcribed spacer (ITS) was utilized for phylogenetic analysis, and comparative analysis of ITS secondary structures was also integrated to identify the desired strain. A novel subtropical microalgal strain, Chlorella vulgaris HNUFU001 with high Se tolerance, was isolated from water samples in a lake at Hainan University, China. Gaussian process regression was utilized to assess the strain's growth under varying Se concentrations. The intracellular accumulation and extracellular removal of Se were measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), respectively. The maximum intracellular organic Se (92 % of total Se) was observed as 108.835 μg/g dry weight (DW) for 1 mg/L Se treatment. The highest Se removal rate was 40 %. The high Se tolerance and enrichment traits enable Chlorella vulgaris HNUFU001 to be a promising candidate for the heterotrophic production of organic Se-related nutraceuticals.

Morpho-Physiological and Antioxidative Responses of Wheat Seedlings to Different Forms of Selenium

Selenium (Se) deficiency in human and animal nutrition is primarily due to low levels of Se in soils. It can be prevented by enriching crops, such as wheat, with Se through agronomic biofortification. Although Se is not essential for plants, it shows a dual effect on their metabolism depending on its concentration. This study aimed to elucidate the impact of five different concentrations (0.4, 4, 20, 40, and 400 mg/kg) of selenate and selenite on the oxidative status and antioxidative response of wheat (Triticum aestivum L., cv. Kraljica) shoots and roots. According to morpho-physiological analyses, selenite was found to have a lower toxicity threshold than selenate. The measurement of oxidative stress biomarkers showed that Se did not cause oxidative damage to wheat seedlings due to the activation of detoxification mechanisms at the biochemical level, which depended on the type of tissue, concentration, and form of applied Se. Treatment with 20 mg/kg of selenate can be recommended for wheat seedling biofortification due to a sufficient increase in Se accumulation in shoots without signs of toxicity. These results contribute to a better understanding of wheat seedlings’ physiological and biochemical responses to Se and the development of more effective biofortification strategies.