Selenium Biofortification of Soybean Seeds Influences Physiological Responses of Seedlings to Osmotic Stress

Positive influence of selenium on the modulation of ascorbate-glutathione cycle in salt stressed Setaria italica L

Soil salinity is a significant abiotic factor affecting crop yield and global distribution, hence selecting salt-tolerant crop species is crucial for food security. Foxtail millet is a resilient crop suitable for hilly, salinity, and drought-prone areas due to its ability to withstand environmental stressors. In this study, foxtail millet was subjected to high NaCl concentrations (150 mM and 200 mM) and selenium (1 μM, 5 μM, and 10 μM) as a stress mitigator. Increased salinity in foxtail plants hampered the growth with decreased pigment levels, increased H₂O₂ levels (153.6%), lipid peroxidation (32.1%), and electrolyte leakage (155.5%). The application of 1 μM Se positively influenced the root-to-shoot ratio (R) (59.2%), photosynthetic pigments, phenolic content (25.1%), flavonoid content (7%) and hence the antioxidant potential of the salt stressed plants there by decreasing the H₂O₂ levels (26.8%) and suggesting a greater ability to scavenge radicals. Both NaCl and Se induced the AsA-GSH pathway. Se supplementation significantly improved AsA-GSH pathway components such as AsA/DHA (40.8%) and GSH/GSSG ratios (39.6%) in salt-stressed foxtail millet, reducing oxidative stress and efficiently neutralizing H₂O₂. Gene expression validation confirmed that SiAPX, SiDHAR, SiMDHAR, and SiGR showed significant upregulation with 1 μM Se application in salt-stressed foxtail millet plants. However, higher Se concentrations (5 μM and 10 μM) led to a reduced fresh weight along with R, increased the MDA and H₂O₂ levels, and did not positively contribute to osmolyte accumulation or improve the AsA/DHA and GSH/GSSG ratios. Elevated Se levels also led to a decreased antioxidant potential. Among the enzymes of the AsA-GSH cycle, higher Se concentrations negatively affected APX, DHAR, MDHAR, and GR activities, indicating stress aggravation rather than mitigation at elevated doses.

White-Seeded Culinary Poppy (Papaver somniferum L.) Se Biofortification: Oil Quality, Fatty Acid Profile, and Seed Yield

The culinary poppy (Papaver somniferum L.) has been used for centuries in everyday diets, especially for food, but also as a non-food source of health-promoting ingredients. In the present study, a field trial was set with white-seeded poppy varieties collected from farmers in Croatia. The poppies were sown as a winter crop. Selenium biofortification was applied using different selenium sources, such as selenite, SeO32-, and selenate SeO42-. In the flowering stage, biofortification was carried out as follows: (1) Se-0: control; (2) SeO3_30: 30 g ha-1; (3) SeO3_60: 60 g ha-1; (4) SeO4_30: 30 g ha-1; and (5) SeO4_60: 60 g ha-1. Plants formed an average of four capsules per plant, with an average seed mass per capsule of 3.52 g. The seed yield varied from 0.91 (SeO3_30) to 1.26 t ha-1 (SeO4_30). The cold-pressed oil was characterized as good-quality since the average water content was 0.38%, insoluble impurities consisted of 0.013%, iodine number value was 135.81 g, I2 was 100 g-1, and saponification number was 188.51 mg KOH g-1, and it was on average 0.93% free fatty acids. Selenium biofortification had a significant (p ≤ 0.05) impact on Se accumulation in the seeds. Thus, the selenite form increased Se content in the seeds by about 7% compared to the control, whereas for the (4) SeO4_30 treatment, the increase was about 50%, and for (5) SeO4_60, it was even higher, about 91% compared to the control treatment. The highest content of fatty acids in the cold-pressed oil was determined for linoleic (76.31%), oleic (13.49), and palmitic (7.86%) acids.

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 selenium nanoparticles on biological and morphofunctional parameters of barley seeds (Hordéum vulgáre L.)

The purpose of this work was to study the effect of selenium nanoparticles (Se NPs) on the biological and morphofunctional parameters of barley seeds (Hordéum vulgáre L.) We used seeds of Hordéum vulgáre L. with reduced morphofunctional characteristics. For the experiment, Se NPs were synthesized and stabilized with didecyldimethylammonium chloride. It was found that Se NPs have a spherical shape and a diameter of about 50 nm. According to dynamic light scattering data, the average hydrodynamic radius of the particles was 28 ± 8 nm. It is observed that the nanoparticles have a positive ζ-potential (+ 27.3 mV). For the experiment, we treated Hordéum vulgáre L. seeds with Se NPs (1, 5, 10 and 20 mg/L). The experiment showed that treatment of Hordéum vulgáre L. seeds with Se NPs has the best effect on the length of roots and sprout at concentration of 5 mg/L and on the number and thickness of roots at 10 mg/L. Germinability and germination energy of Hordéum vulgáre L. seeds were higher in group treated with 5 mg/L Se NPs. Analysis of macrophotographs of samples, histological sections of roots and 3D visualization of seeds by microcomputing tomography confirmed the best effect at 5 mg/L Se NPs. Moreover, no local destructions were detected at concentrations > 5 mg/L, which is most likely due to the inhibition of regulatory and catalytic processes in the germinating seeds. the treatment of Hordéum vulgáre L. seeds with > 5 mg/L Se NPs caused significant stress, coupled with intensive formation of reactive oxygen species, leading to a reorientation of root system growth towards thickening. Based on the results obtained, it was concluded that Se NPs at concentrations > 5 mg/L had a toxic effect. The treatment of barley seeds with 5% Se NPs showed maximum efficiency in the experiment, which allows us to further consider Se NPs as a stimulator for the growth and development of crop seeds under stress and reduced morphofunctional characteristics.

Selenium seed priming enhanced the growth of salt-stressed Brassica rapa L. through improving plant nutrition and the antioxidant system

Various abiotic stresses may affect the germination, growth, and yield of direct-seeded vegetable crops. Seed priming with effective antioxidant mediators may alleviate these environmental stresses by maintaining uniformity in seed germination and improving the subsequent health of developing seedlings. Salt-induced stress has become a limiting factor for the successful cultivation of Brassica rapa L., especially in Southeast Asian countries. The present study was performed to elucidate the efficacy of seed priming using selenium (Se) in mitigating salt-induced oxidative stress in turnip crops by reducing the uptake of Na+. In this study, we administered three different levels of Se (Se-1, 75 μmol L-1; Se-2, 100 μmol L-1; and Se-3, 125 μmol L-1) alone or in combination with NaCl (200 mM). Conspicuously, salinity and Se-2 modulated the expression levels of the antioxidant genes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX). The upregulated expression of stress-responsive genes alleviated salt stress by scavenging the higher reactive oxygen species (ROS) level. The stress ameliorative potential of Se (Se-2 = 100 μmol L-1) enhanced the final seed germination percentage, photosynthetic content, and seedling biomass production up to 48%, 56%, and 51%, respectively, under stress. The advantageous effects of Se were attributed to the alleviation of salinity stress through the reduction of the levels of malondialdehyde (MDA), proline, and H2O2. Generally, treatment with Se-2 (100 μmo L-1) was more effective in enhancing the growth attributes of B. rapa compared to Se-1 (75 μmo L-1) and Se-3 (125 μmo L-1) under salt-stressed and non-stressed conditions. The findings of the current study advocate the application of the Se seed priming technique as an economical and eco-friendly approach for salt stress mitigation in crops grown under saline conditions.

Secondary Metabolite Profile and Pharmacological Opportunities of Lettuce Plants following Selenium and Sulfur Enhancement

Selenium (Se) is an essential trace nutrient for humans and animals owing to its role in redox regulation, thyroid hormone control factors, immunity, inflammatory reactions, brain activities, and carbohydrate regulation. It is also important to support muscle development, as well as for reproductive and cardiovascular well-being. Furthermore, sulfur is known to be a healing element, due to the remarkable function of specialized and secondary S-containing compounds. The scope of the current study was to determine the impact of Se and S enrichment on the secondary metabolite accumulation and antibacterial and NO inhibition activities in green and red leaf lettuce (V1 and V2, respectively). The plants were grown in a hydroponic system supplied with different S concentrations (S0: 0, S1: 1 mM and S2: 1.5 mM K₂SO₄) via the nutrient solution and foliar-applied varying levels of Se (0, 0.2 and 2.6 µM). Electrospray ionization-quadrupole time-of-flight mass spectrometry (ESI-QTOF/MS) combined with ultra-performance liquid chromatography (UPLC) was used to identify the secondary metabolites in green and red lettuce. The results indicated that extracts of the biofortified lettuce were not cytotoxic to Vero kidney cells at the highest concentration tested of 1 mg/mL. The ESI/MS of the tentatively identified metabolites showed that the response values of 5-O-caffeoylquinic acid, cyanidin 3-O-galactoside, quercetin 3-O-(6''-acetyl-glucoside) and quercetin 3-O-malonylglucoside were induced synergistically under higher Se and S levels in red lettuce plants. The acetone extract of red lettuce had antibacterial activity against Pseudomonas aeruginosa, with a minimum inhibitory concentration (MIC) of 0.156 and 0.625 μg/mL under S2/Se1 and S2/Se2 treatments, respectively. As with antibacterial activity, the acetone extract of green (V1) lettuce treated with adequate (S1) and higher S (S2) under Se-limiting conditions showed the ability to inhibit nitric oxide (NO) release from macrophages. NO production by macrophages was inhibited by 50% at respective concentrations of 106.1 ± 2.4 and 101.0 ± 0.6 μg/mL with no toxic effect on the cells, in response to S1 and S2, respectively, under Se-deficient conditions (Se0). Furthermore, the red cultivar (V2) exhibited the same effect as the green cultivar (V1) regarding NO inhibition, with IC₅₀ = 113.0 ± 4.2 μg/mL, in response to S1/Se2 treatments. Collectively, the promising NO inhibitory effect and antibacterial activity of red lettuce under the above-mentioned conditions might be attributed to the production of flavonoid glycosides and phenylpropanoic acid esters under the same condition. To the best of our knowledge, this is the first report to show the novel approach of the NO inhibitory effect of Se and S enrichment in food crops, as an indicator for the potential of Se and S as natural anti-inflammatory agents.

In-Vivo Biophoton Emission, Physiological and Oxidative Responses of Biostimulant-Treated Winter Wheat (Triticum eastivum L.) as Seed Priming Possibility, for Heat Stress Alleviation

High temperature induces oxidative processes in wheat, the alleviation of which is promising using biostimulants. Priming has been used for enhancing stress tolerance of seedlings. However, the usage of biostimulants for priming is an unexplored area under either normal or stress conditions. Therefore, the aim of our study was to evaluate the heat stress alleviation capability of differentially applied biostimulant treatments on wheat seedlings. The investigation included stress parameters (fresh/dry weight ratio, chlorophyll content estimation, antioxidant capacity and lipid oxidation) combined with biophoton emission measurement, since with this latter non-invasive technique, it is possible to measure and elucidate in vivo stress conditions in real-time using lipid oxidation-related photon emissions. We confirmed that a single biostimulant pretreatment increased antioxidant capacity and decreased biophoton release and lipid oxidation, indicating the reduction of the harmful effects of heat stress. Therefore, biophoton emission proved to be suitable for detecting and imaging the effects of heat stress on wheat seedlings for the first time. Two-way analysis of variance (ANOVA) revealed that biostimulant (p = 4.01 × 10⁻⁷) treatments, temperature (p = 9.07 × 10⁻⁸), and the interaction of the two factors (p = 2.07 × 10⁻⁵) had a significant effect on the overall count per second values of biophoton emission, predicting more efficient biostimulant utilization practices, even for seed priming purposes.