Foliar Se Research Articles

Selenium Biofortification of Vegetables Grown in Calcareous Soil: A Pot Experiment Using 77Se as a Tracer.

Dietary selenium (Se) is vital for human health and can be provided through consumption of Se-rich vegetables. Soil Se is often poorly available and so biofortification using Se-enriched fertilizers is used to enhance dietary intake. This study aimed to (a) evaluate the feasibility of biofortifying vegetables, commonly grown in the calcareous soils of Kurdistan, with a single application of Se (10 g ha-1) as selenate and, (b) trace the fate of applied Se using an enriched stable isotope, ⁷⁷Se. A randomized block pot experiment was conducted with five vegetable species: celery, chard, lettuce, radish, and spring onion. Soils were spiked with 2 µg ⁷⁷Se per pot, simulating 10 g ha-1. Plants were harvested after 8 weeks, and both plant tissues and soils underwent sequential extraction and isotopic analysis to determine Se fractionation and source apportionment. Across all species, plant uptake of native soil Se (Ses) exceeded that of fertilizer-derived Se (Sef). Shoot concentrations of Ses ranged from 58.2 to 115 µg kg-1, while ⁷⁷Sef concentrations varied between 10.5 and 46.9 µg kg-1. Post-harvest soil analyses indicated immobilization of applied ⁷⁷Se: 55% transitioned to organically bound forms, 40% became recalcitrant, and only 5% remained in plant-available fractions. The study underscores the challenges of Se biofortification in calcareous soils, where interaction with CaCO3 may reduce Se availability. Variations in Se uptake among vegetable species highlight the importance of application timing. To enhance biofortification efficacy for fast-growing leafy vegetables, mid-season or foliar Se applications are recommended to counteract rapid soil immobilization.

Effects of silicon application on <i>Betula pendula</i> seedlings

Silicon (Si) is a beneficial element for many plant species, conferring resistance to drought and herbivory, but its effects on trees are less known. We studied responses of silver birch (<i>Betula pendula</i>), grown in peat, to liquid Si supplementation (Si concentration 0.65 mM) on 1) growth, 2) water economy and 3) element accumulation plus 4) feeding preference of an insect, <i>Epirrita autumnata</i> and a mammalian herbivore, <i>Microtus agrestis</i>. Plant growth was not affected but control (Si–) plants shed their old leaves earlier. Detached Si+ leaves lost water 11%-units less than Si–, and the integrated water-use efficiency based on <sup>13</sup>C analysis was higher in Si+. Foliar Se was higher and Mn and S lower in Si+. Root Mg concentrations were higher and Pb lower in Si+. <i>Epirrita autumnata</i> did not prefer either treatment, but <i>M. agrestis</i> preferred Si– stems. Silicon improved birch water relations as indicated by the leaf drying resistance and increased water-use efficiency. The changes in metal accumulation were probably beneficial, but the lower S/Se ratio requires attention. Furthermore, Si decreased palatability to a mammalian herbivore. Using Si as fertilizer in nurseries could be possible to increase birch tolerance to water stress and herbivory.

The Effects of Water Management, Foliar Fertilizers, and Lime Application on the Accumulation of Cd and As in Rice Grains Based on a Field Trial

The aim of this study was to explore the feasible measurement of the control of cadmium (Cd) and arsenic (As) accumulation in rice grains. A field experiment was carried out to research the effect of different treatments, including spraying silicon (Si)/selenium (Se) foliar fertilizers, the application of lime (CaO), water management (continuous flooding), and the co-application of foliar fertilizers and flooding, on Cd and As accumulation in rice grains in Guangxi Province. The results indicate that Cd accumulation in rice grains decreased under different treatments and Cd content in rice grains reached the threshold of 0.2 mg kg−1. In the single technical treatments, CaO application, flooding, spraying foliar Se fertilizer, and spraying foliar Si fertilizer decreased Cd content by 73.15%, 60.44%, 45.76%, and 36.07%, respectively. However, flooding and CaO amendment enhanced As accumulation in rice grains. The co-application of flooding and spraying foliar fertilizer can simultaneously reduce Cd and As in rice grains. In addition, they resulted in lower Cd content than the single technical treatments. Among the treatments, the lowest bioaccumulation factors of Cd and As were found after the co-application of flooding and Si foliar fertilizer, which decreased these factors by 74.02% and 22.72%, respectively. These results suggest that spraying foliar Si fertilizer combined with flooding may be a promising method to synchronously inhibit the accumulation of Cd and As in rice.

Synergistic mechanisms of lignin-based novel materials and leaf-surface selenium fertilizer in alleviating drought and heavy metal stress

Drought and heavy metal stress threaten sustainable crop production and ecosystems, highlighting the urgent need for resilient agricultural practices. The synthesis of lignin-based hydrogel (L-GH) and foliar selenium (Se) offers a potential solution to mitigate these adverse effects. However, comprehensive research on their applications in alleviating drought stress, remediating heavy metals, and enhancing crop production is limited. To address these gaps, the optimal ratio for L-GH synthesis using sodium lignosulfonate (L) and γ-polyglutamic acid (γ-PGA) as raw materials was determined through the response surface method (RSM). The synthesis mechanism and possible functional groups and structures of L-GH were identified by Fourier infrared spectroscopy (FTIR) and other characterization techniques. A pot experiment assessed the effects of L-GH (L0=0; L1=0.2 %; and L2=0.5 %) and foliar Se (L0=0; Se=3 mg.L−1) under drought (H=75 % control; HA=45 % field water capacity) on Chinese broccoli growth and the uptake of heavy metals cadmium, copper, zinc (Cd, Cu, Zn). Results indicated that L-GH hydrogel, with a layered porous structure and hydrophilic functional groups, achieved a water absorption rate of 389.17 g.g−1. Under drought and heavy metal stress, L-GH combined with Se effectively reduced the absorption of Cd and Cu. In the L2+Se treatment (0.5 % L-GH + 3 mg.L−1 Se), Cd and Cu contents decreased by 31.06 % and 72.14 %, respectively. Simultaneously, the photosynthetic activity of the plant increased, stress resistance was enhanced, and both growth and biomass accumulation were promoted. Malondialdehyde (MDA) content decreased by 78.82 %, and chlorophyll fluorescence parameters (PSII potential activity Fv/F0 and maximum photochemical efficiency Fv/Fm) increased by 49.92 % and 11.97 %, respectively. Redundancy analysis (RDA) revealed that L-GH could potentially decrease the absorption of heavy metals by enhancing soil moisture (SWC) and pH levels, increasing aggregate stability (WAS) and organic carbon (SOC) content, enhancing plant stress resistance, and promoting growth. In this study, a novel material (L-GH) capable of retaining water and immobilizing heavy metals in soil was successfully developed. The concurrent application of L-GH with Se has been shown to effectively mitigate the combined stresses of drought and heavy metals on the growth of Chinese broccoli. These findings offer valuable insights for the remediation of soil contaminated by both drought and heavy metals.

Effects of Selenate Application on Growth, Nutrient Bioaccumulation, and Bioactive Compounds in Broccoli (Brassica oleracea var. italica L.)

The biofortification of edible crops with selenium (Se) is a common and effective strategy to address inadequate Se intake, which is suffered by millions of people worldwide. However, there is little information regarding the effects of this practice on crops belonging to the important Brassica family. To evaluate the efficacy of foliar Se application on broccoli, four treatments with varying Se concentrations were tested: 0%, 0.05%, 0.10%, and 0.15% (w/v), applied as sodium selenate during the early flowering stage. Although no overall effects on growth and biomass parameters were observed, the results indicate that the lowest Se dose (0.05-Se) was sufficient to notably increase Se concentration in the florets, even after boiling. Based on the increase to 14.2 mg Se kg−1 of dry matter in this broccoli fraction, it was estimated that consuming a 100-gram portion of boiled florets biofortified with 0.05% Se would provide approximately 140 µg of Se, which could be sufficient to potentially improve human selenium status, as previously documented. Moreover, the results obtained underscore how the application of this small dose was also adequate to reduce phytate concentration in the florets and to increase antioxidant and polyphenol concentrations, thereby improving the concentration and bioavailability of other essential nutrients, including Ca, Mg, Fe, and Zn, along with improving its quality as an antioxidant food.

Enhancement of Nutritional Substance, Trace Elements, and Pigments in Waxy Maize Grains through Foliar Application of Selenite.

Selenium (Se) is a micronutrient known for its essential role in human health and plant metabolism. Waxy maize (Zea mays L. sinensis kulesh)-known for its high nutritional quality and distinctive flavor-holds significant consumer appeal. Therefore, this study aims to assess the effects of foliar Se spraying on the nutritional quality of waxy maize grains, with a focus on identifying varietal differences and determining optimal Se dosage levels for maximizing nutritional benefits. We employed a two-factor split-plot design to assess the nutritional quality, trace elements, and pigment content of jinnuo20 (J20) and caitiannuo1965 (C1965) at the milk stage after being subjected to varying Se doses sprayed on five leaves. Our findings indicate superior nutrient content in J20 compared to C1965, with both varieties exhibiting optimal quality under Se3 treatment, falling within the safe range of Se-enriched agricultural products. JS3 (0.793) demonstrated the highest overall quality, followed by JS2 (0.606), JS4 (0.411), and JS1 (0.265), while CS0 had the lowest (-0.894). These results underscore the potential of foliar biofortification to enhance the functional component contents of waxy maize grains.

Agro-biofortification of maize with selenium for higher grain selenium contents and productivity

Selenium (Se) is a vital mineral nutrient for animal and human health, which can be supplemented through seed biofortification techniques. Present study determined the potential of improving Se content in maize grain via several Se fertilizer application methods to enhance the nutritional status of native populations. Field trials were conducted for two growing years with different Se application methods and application rates to evaluate grain Se content in maize, Se recovery, grain macro- and micro-nutrients and grain yield under rain-fed conditions. Results demonstrated that foliar and soil Se applications showed no significant impacts on maize biomass and grain yield as well as maize grain N, P, K, Ca, Mg, Fe, Mn, Cu and Zn contents. However, both foliar and soil Se application significantly enhanced the maize grain Se content. Foliar application of Se exhibited greater Se recoveries of 54 % and 108 % in the grain over soil Se fertilizer for the first and second growing seasons while the later was recorded with only 1.71 % and 0.97 % increase as compared to control. In conclusion, foliar Se application at silking stage at the rate of 8.85 µM enhanced the grain Se content in maize at minimum costs as compared to soil Se application.

Increased nutritional quality of rice grains and migration mechanisms of selenium by spraying a foliar selenium-rich nutrient solution

Foliar application of selenium (Se) is an effective method for biofortification in rice, to ensure that sufficient Se is supplied by the crop to maintain human health. In order to improve Se concentration in rice and meet the daily recommended intake for humans, a foliar Se fertilizer was applied in five regions of Liaoning and Jilin provinces, China, and its effects on rice quality, leaf morphology, and wax characteristics were assessed in field tests. The effects of alkyl polyglycosides (APG) in the Se fertilizer were evaluated, and epicuticular waxes were measured to analyze the effects of the fertilizer on plant water status. The Se fertilizer effectively enhanced organic Se levels in rice (p < 0.05), ranging from 599.8 to 2002.0 µg kg−1. An intake of 50 g d−1 of Se-enriched rice can meet nutritional requirements, with total Se intake ranging from 30.0 to 100.1 µg d−1. The Se fertilizer increased the protein content and decreased the proportion of chalky rice (p < 0.05). APG increased the wettability of Se fertilizer on the surface of leaves, so Se could be better absorbed into the leaves and accumulate in rice. The Se fertilizer increased the epicuticular wax so that moisture loss from leaves was reduced. Mean cuticular wax thicknesses were 2.36 and 2.25 µg cm2 in Daohuaxiang and Wuyou 4, respectively. These results suggest a link between the quality of rice and epicuticular wax thickness, and the foliar application of Se fertilizer shows promise for increasing Se content in rice grown in Se deficient soils.

Enhancing salinity tolerance in cucumber through Selenium biofortification and grafting

BackgroundSalinity stress is a major limiting factor for plant growth, particularly in arid and semi-arid environments. To mitigate the detrimental effects of salinity stress on vegetable production, selenium (Se) biofortification and grafting onto tolerant rootstocks have emerged as effective and sustainable cultivation practices. This study aimed to investigate the combined effects of Se biofortification and grafting onto tolerant rootstock on the yield of cucumber grown under salinity stress greenhouse conditions. The experiment followed a completely randomized factorial design with three factors: salinity level (0, 50, and 100 mM of NaCl), foliar Se application (0, 5, and 10 mg L-1 of sodium selenate) and grafting (grafted and non-grafted plants) using pumpkin (Cucurbita maxima) as the rootstock. Each treatment was triplicated.ResultsThe results of this study showed that Se biofortification and grafting significantly enhanced salinity tolerance in grafted cucumbers, leading to increased yield and growth. Moreover, under salinity stress conditions, Se-Biofortified plants exhibited increased leaf relative water content (RWC), proline, total soluble sugars, protein, phenol, flavonoids, and antioxidant enzymes. These findings indicate that Se contributes to the stabilization of cucumber cell membrane and the reduction of ion leakage by promoting the synthesis of protective compounds and enhancing antioxidant enzyme activity. Moreover, grafting onto pumpkin resulted in increased salinity tolerance of cucumber through reduced Na uptake and translocation to the scion.ConclusionIn conclusion, the results highlight the effectiveness of Se biofortification and grafting onto pumpkin in improving cucumber salinity tolerance. A sodium selenate concentration of 10 mg L-1 is suggested to enhance the salinity tolerance of grafted cucumbers. These findings provide valuable insights for the development of sustainable cultivation practices to mitigate the adverse impact of salinity stress on cucumber production in challenging environments.

Foliar Spray with Selenium to Mitigate the Impact of Water Stress on Chemical, Enzymatic, and Hormonal Parameters of Garlic Allium sativum L.

The current research explored the beneficial role of selenium (Se) in alleviating the negative impacts of water stress on the chemical, enzymatic, and hormonal parameters of garlic plants via manipulating chemo-physiological mechanisms. A field experiment was executed at the research station of the Faculty of Agriculture, University of Kufa, Iraq in September 2022 using a randomized complete block design with three replicates based on a strip-plot system. Three water levels (100%, 80%, and 60%) were set up in the whole plots while foliar application of selenium (Se) with three concentrations (0, 10, and 20) mg.L-1 were assigned to the subplots. Our findings revealed a significant increase in the leaf content of free proline acid, sulfur, and ABA, as well as an increase in the activity of the antioxidant enzymes SOD and CAT when reducing irrigation levels from (100% to 60%) of the water requirement. While there was a significant decline in the plant hormones GA3 and IAA content in garlic leaves @ (60%) level of irrigation. The plants treated with foliar selenium @ (20 mg.L-1) enhanced most of the studied characteristics of garlic plants grown at different water levels. Moreover’ the full water requirement in combination with foliar Se @ (20 mg.L-1) provided the highest values of GA3 and IAA which were both comparable to the interaction treatment of water level @ (80%) and foliar Se @ (20 mg.L-1).

Foliar Selenium Application to Reduce the Induced-Drought Stress Effects in Coffee Seedlings: Induced Priming or Alleviation Effect?

This study aimed to investigate the role of Se supply in improving osmotic stress tolerance in coffee seedlings while also evaluating the best timing for Se application. Five times of Se foliar application were assessed during induced osmotic stress with PEG-6000 using the day of imposing stress as a default, plus two control treatments: with osmotic stress and without Se, and without osmotic stress and Se. Results demonstrated that osmotic stress (OS) promoted mild stress in the coffee plants (ψw from -1.5MPa to -2.5 MPa). Control plants under stress showed seven and five times lower activity of the enzymes GR and SOD compared with the non-stressed ones, and OS was found to further induce starch degradation, which was potentialized by the Se foliar supply. The seedlings that received foliar Se application 8 days before the stress exhibited higher CAT, APX, and SOD than the absolute control (-OS-Se)-771.1%, 356.3%, and 266.5% higher, respectively. In conclusion, previous Se foliar spray is more effective than the Se supply after OS to overcome the adverse condition. On the other hand, the post-stress application seems to impose extra stress on the plants, leading them to reduce their water potential.

Selenium improves the medicinal safety and quality of Bletilla striata by promoting the fixation of cadmium in root: Pot and field experiments

Soil cadmium (Cd) pollution poses a considerable threat to the safe production of traditional Chinese medicine (TCM) in China. The tubers of Bletilla striata, a precious TCM, are widely used to treat various ailments. However, the medicinal safety and quality of tubers are significantly affected by high Cd accumulation. While selenium (Se) is known to reduce Cd concentration in traditional crops, its impact on Cd content in medicinal parts and overall quality remains underexplored. To bridge the gap, a pot experiment and field validation were conducted to determine the effectiveness of foliar Se application. The results revealed that Se effectively counteracted Cd damage. Compared to Cd treatment alone, Se at 1.5 mg L−1 significantly decreased Cd content by 46.33 %, increased the biomass by 21.48 %, and raised the total phenolic, flavonoid, saponin, and polysaccharide contents by 46.31 %, 30.46 %, 27.08 %, and 29.01 %, respectively, in tubers. Furthermore, this study explored the mechanism of Se action. Se facilitated Cd accumulation in root cell walls and soluble fractions, enhanced the synthesis of phytochelatins (PC), and stored them in the form of PC-Cd complexes. These findings have profound implications for the cultivation of TCM, ensuring its safety, and promoting sustainable agricultural practices.

Effects of soil amendments and foliar selenium applications on soil cadmium immobilization and wheat accumulation

Wheat cadmium (Cd) contaminationis one of the environmental and agricultural concerns worldwide. Here, the effects of foliar selenium (Se) and soil amendments (lime, biofuel ash and sodium sulfide (DSO), iron mine tailing and alkali lignin (MX)) applications on the soil Cd fractions and wheat Cd accumulations were studied by incubation, greenhouse pot, and field plot experiments. The results showed that in soil incubation experiment, lime and MX applications significantly increased soil pH and DSO applications significantly decreased soil pH, while all the three amendments can significantly reduce the available Cd fractions by 16-21%. Foliar spraying can significantly increase the growth and yield of the high-Cd-accumulating-cultivar (Puxing5). In the greenhouse experiment, lime and MX applications considerably decreased grain Cd concentrations by 53-56% and 41-52% for Puxing5 and by 9-38% and 23-28% for Zhoumai30, respectively. In the field experiment, the Cd concentrations were significantly reduced by 67-69% and 69-74% in Puxing5 grain by lime and MX applications, respectively. DSO applications also significantly reduced Cd concentrations in grains by 56-59% for Puxing5 and by 22-27% for Zhoumai30 in the greenhouse experiment, but in contrast, increased Cd concentrations in field experiment by 20-23%. Our results implicate that the incubation and greenhouse experiments are necessary to be verified in the field and the foliar Se application is recommended when considered both the financial costs and production safety.

Foliar Application of Selenium Associated with a Multi-Nutrient Fertilizer in Soybean: Yield, Grain Quality, and Critical Se Threshold.

Selenium uptake and its content in soybean grains are affected by Se application methods. This study evaluated the impact of Se foliar application combined with a multi-nutrient fertilizer (MNF) on soybean, establishing a Se threshold to better understand the relationship between Se content in grains and yield of two genotypes (58I60 Lança and M5917). Two trials were conducted in a 4 × 2 factorial design: four Se rates (0, 10, 40, 80 g Se ha-1) and two methods of foliar Se application (Se combined or not with MNF). Foliar fertilizers were applied twice, at phenological stages of beginning of pod development and grain filling. Grain yield increased with the application of MNF, yet Se rates increased Se contents linearly up to 80 g Se ha-1, regardless of the use of MNF. Lança and M5917 genotypes had grain Se critical thresholds of 1.0 and 3.0 mg kg-1, respectively. The application of Se favored higher contents of K, P, and S in grains of genotype Lança and higher contents of Mn and Fe in grains of genotype M5917. Our findings highlight the importance of addressing different Se fertilization strategies as well as genotypic variations when assessing the effects of Se on soybean yield and grain quality.

Effect of Foliar Application of Sodium Selenate on Mineral Relationships in Brassicaceae Crops

The relationships of selenium (Se) with other elements in plants is important for producing functional food with high Se contents and a predicted quality. To unveil the peculiarities of the element interactions, eight botanical varieties of Brassica oleracea L. were grown in similar conditions with or without foliar application of sodium selenate. High varietal differences, elicited by the Se supply, were recorded with regard to the accumulation of the elements examined, except for Mg, P and Si. Cabbage florets (broccoli and cauliflower) were characterized by both the lowest total mineral content and number of elements showing content changes under the Se supply (7–8 out of 25), whereas in Savoy cabbage, the highest number of minerals displayed content changes (13–14 from 25). The Se treatment did not significantly interfere with the high correlation coefficients recorded between Sr–Ca, Co–Ni and Zn–Mg (0.824–0.952). The selenium biofortification value varied from 12 to 138 depending on the species and was inversely correlated with the Si accumulation in the control plants (r = −0.872, p &lt; 0.001). A significant decrease in the correlation coefficients occurred due to the Se supply regarding Zn with P and Co, Ca with Co and Li, Li and V, and Na and Sn, while the V–Pb relationship was significantly enhanced. Among the 25 elements studied, Cr demonstrated the highest number of significant correlation coefficient changes (with K, Na, P, Si, Zn, Cu, Co, I, As, Pb, and V). The results of this research prove the variability of the element interactions under foliar Se treatments in Brassica oleracea plants and reveal, for the first time, an inverse correlation between the Se biofortification level and Si content in untreated plants.

Biochemical Response of Okra (Abelmoschus esculentus L.) to Selenium (Se) under Drought Stress

Drought stress restricts the growth of okra (Abelmoschus esculentus L.) by disrupting its biochemical and physiological functions. The current study was conducted to evaluate the role of selenium (0, 1, 2, and 3 mg Se L−1 as a foliar application) in improving okra tolerance to drought (control (100% field capacity-FC), mild stress (70% FC), and severe stress (35% FC)) imposed 30 days after sowing (DAS). Drought (severe) markedly decreased chlorophyll (32.21%) and carotenoid (39.6%) contents but increased anthocyanin (40%), proline (46.8%), peroxidase (POD by 12.5%), ascorbate peroxidase (APX by 11.9%), and catalase (CAT by 14%) activities. Overall, Se application significantly alleviated drought stress-related biochemical disturbances in okra. Mainly, 3 mg Se L−1 significantly increased chlorophyll (21%) as well as anthocyanin (15.14%), proline (18.16%), and antioxidant activities both under drought and control conditions. Selenium played a beneficial role in reducing damage caused by oxidative stress, enhancing chlorophyll and antioxidants contents, and improved plant tolerance to drought stress. Therefore, crops including okra especially, must be supplemented with 3 mg L−1 foliar Se for obtaining optimum yield in arid and semiarid drought-affected areas.

Novel multifunctional natural selenium supplement development, in vitro and in vivo analysis, and risk-benefit assessment: Selenium-enriched chicory as a case study

Selenium (Se) is essential for the modification of human life functions and has a double-edged sword effect. However, the development of Se supplements for both medicinal and dietary is rare. Critical in vivo and in vitro correlation studies still unexplored. In this study, we developed Se-enriched chicory for the first time using chicory as a model plant. The distribution of Se and its species transformation were elucidated. In vivo and in vitro absorption correlation, safety and risk-benefit management were also focused. Results in this study showed that foliar Se application is more beneficial for cultivating Se-enriched chicory compared to root application. What is striking is SeIV converted to SeVI, SeMet, SeCys2 and SeMeCys in chicory, which is more favorable for human absorption and reduces toxicity. In gastric phase in vitro, Se from Se-enriched chicory exhibited high bioaccessibility (79.4%). The relative bioavailability of liver and kidneys as effect endpoints in vivo at high exposure to Se with 76.5%. In addition, this study first analyzed and established robust in vivo-in vitro correlations of Se in Se-enriched chicory. The prediction model for liver-gastric fluid had the best correlation (R2 = 0.853, p < 0.05). Meanwhile, graded assessment strategy revealed that the risk-benefit of Se-enriched chicory for dietary and TCM needs to be balanced separately. All evidence suggests that Se-enriched chicory could be a new candidate plant for Se supplements in the event of Se deficiency. This research will provide cases and insights into future studies and reduce the uncertainty of Se intake risk and benefit assessment from Se-enriched products.

Integrated eco-physiological, biochemical, and molecular biological analyses of selenium fortification mechanism in alfalfa.

Foliar Se (IV) application at 100mg/kg can act as a positive bio-stimulator of redox, photosynthesis, and nutrient metabolism in alfalfa via phenotypes, nutritional compositions, biochemistry, combined with transcriptome analysis. Selenium (Se) is an essential element for mammals, and plants are the primary source of dietary Se. However, Se usually has dual (beneficial/toxic) effects on the plant itself. Alfalfa (Medicago sativa L.) is one of the most important forage resources in the world due to its high nutritive value. In this study, we have investigated the effects of sodium selenite (Se (IV)) (0, 100, 200, 300, and 500mg/kg) on eco-physiological, biochemical, and transcriptional mechanisms in alfalfa. The phenotypic and nutritional composition alterations revealed that lower Se (IV) (100mg/kg) levels positively affected alfalfa; it enhanced the antioxidant activity, which may contribute to redox homeostasis and chloroplast function. At 100mg/kg Se (IV) concentration, the H2O2, and malondialdehyde (MDA) contents decreased by 36.72% and 22.62%, respectively, whereas the activity of glutathione peroxidase (GPX) increased by 31.10%. Se supplementation at 100mg/kg increased the plant pigments contents, the light-harvesting capacity of PSII (Fv/Fm) and PSI (ΔP700max), and the carbon fixation efficiency, which was demonstrated by enhanced photosynthesis (37.6%). Furthermore, alfalfa shifted carbon flux to protein synthesis to improve quality at 100mg/kg of Se (IV) by upregulating carbohydrate and amino acid metabolic genes. On the contrary, at 500mg/kg, Se (IV) became toxic. Higher Se (IV) disordered the plant antioxidant system, increasing H2O2 and MDA by 14.2 and 4.3%, respectively. Moreover, photosynthesis was inhibited by 20.2%, and more structural substances, such as lignin, were synthesized. These results strongly suggest that Se (IV) at a concentration of 100mg/kg act as the positive bio-stimulator of redox metabolism, photosynthesis, and nutrient in alfalfa.

Treatment of Ginkgo biloba with Exogenous Sodium Selenite Affects Its Physiological Growth, Changes Its Phytohormones, and Synthesizes Its Terpene Lactones

Ginkgolide is a unique terpenoid natural compound in Ginkgo biloba, and it has an important medicinal value. Proper selenium has been reported to promote plant growth and development, and improve plant quality, stress resistance, and disease resistance. In order to study the effects of exogenous selenium (Se) on the physiological growth and the content of terpene triolactones (TTLs) in G. biloba seedlings, the seedlings in this work were treated with Na2SeO3. Then, the physiological indexes, the content of the TTLs, and the expression of the related genes were determined. The results showed that a low dose of Na2SeO3 was beneficial to plant photosynthesis as it promoted the growth of ginkgo seedlings and increased the root to shoot ratio. Foliar Se application significantly increased the content of soluble sugar and protein and promoted the content of TTLs in ginkgo leaves; indeed, it reached the maximum value of 7.95 mg/g in the ninth week, whereas the application of Se to the roots inhibited the synthesis of TTLs. Transcriptome analysis showed that foliar Se application promoted the expression levels of GbMECPs, GbMECT, GbHMGR, and GbMVD genes, whereas its application to the roots promoted the expression of GbDXS and GbDXR genes. The combined analysis results of metabolome and transcriptome showed that genes such as GbDXS, GbDXR, GbHMGR, GbMECPs, and GbCYP450 were significantly positively correlated with transcription factors (TFs) GbWRKY and GbAP2/ERF, and they were also positively correlated with the contents of terpene lactones (ginkgolide A, ginkgolide B, ginkgolide M, and bilobalide). Endogenous hormones (MeJA-ILE, ETH, and GA7) were also involved in this process. The results suggested that Na2SeO3 treatment affected the transcription factors related to the regulation of endogenous hormones in G. biloba, and further regulated the expression of genes related to the terpene synthesis structure, thus promoting the synthesis of ginkgo TTLs.

Soil and foliar selenium application: Impact on accumulation, speciation, and bioaccessibility of selenium in wheat (Triticum aestivum L.).

A comprehensive study in selenium (Se) biofortification of staple food is vital for the prevention of Se-deficiency-related diseases in human beings. Thus, the roles of exogenous Se species, application methods and rates, and wheat growth stages were investigated on Se accumulation in different parts of wheat plant, and on Se speciation and bioaccessibility in whole wheat and white all-purpose flours. Soil Se application at 2 mg kg–1 increased grains yield by 6% compared to control (no Se), while no significant effects on yield were observed with foliar Se treatments. Foliar and soil Se application of either selenate or selenite significantly increased the Se content in different parts of wheat, while selenate had higher bioavailability than selenite in the soil. Regardless of Se application methods, the Se content of the first node was always higher than the first internode. Selenomethionine (SeMet; 87–96%) and selenocystine (SeCys2; 4–13%) were the main Se species identified in grains of wheat. The percentage of SeMet increased by 6% in soil with applied selenite and selenate treatments at 0.5 mg kg–1 and decreased by 12% compared with soil applied selenite and selenate at 2 mg kg–1, respectively. In addition, flour processing resulted in losses of Se; the losses were 12–68% in white all-purpose flour compared with whole wheat flour. The Se bioaccessibility in whole wheat and white all-purpose flours for all Se treatments ranged from 6 to 38%. In summary, foliar application of 5 mg L–1 Se(IV) produced wheat grains that when grounds into whole wheat flour, was the most efficient strategy in producing Se-biofortified wheat. This study provides an important reference for the future development of high-quality and efficient Se-enriched wheat and wheat flour processing.