Se Application Research Articles

Exogenous selenium foliar application on nutrition, grain yield and quality of rice (Oryza sativa L.)

Selenium (Se) supplementation through plant-based foods is easy to implement and effective; therefore, it is important to explore the Se-enrichment ability of staple grains and analyze their quality. The purpose of this study was to investigate the effects of foliar application of Se on the quality, Se-enriched capacity, organic Se composition and content of rice under field cultivation. The results showed that exogenous Se application at 80 mg L−1 contributed the most to the yield, and eight elements differed accordingly to the application of Se, promoted the accumulation of Se-containing organic matter in rice grain. This indicates that rational foliar application of Se can effectively improve the quality of rice grains. Moreover, selenomethionine (SeMet), selenocysteine (SeCys2), and Se-methylselenocysteine (Se-MeSeCys) are important components of Se-enriched in hydrolyzed proteins in grains. Based on these results, foliar spraying of Se is a suitable method to supplement rice with additional Se and can improve the yield and quality of rice grains, particularly the quality of organic Se and Se-containing amino acids.

Agronomic, biochemical and bioactive properties of sage (Salvia officinalis L.) affected by foliar selenium spraying

The sage is a perennial medicinal and aromatic plant belonging to the Lamiaceae family. Macro-micro elements have an important place in the development of this plant. One of these elements is selenium. This study aims to examine the effect of foliar selenium (Se) application on the agronomic, biochemical, and bioactive properties of sage. The plant height (PH), fresh herb yield (FHY), dry herb yield (DHY), and dry leaf yield (DLY) as agronomic properties, and Se content in the plant (SCP), ascorbic acid content (AAC), total phenolic content (TPC), antioxidant activity (AA) and mineral composition (MC) as biochemical and bioactive properties were investigated in this context. The experiment was carried out in four replications over three years in 2018, 2019, and 2020. In the study, 0 (control), 100, 200, 400, and 800 g ha−1 Se were applied to sage leaves. At the end of the study, it was determined that Se application was effective on the agronomic characteristics of the sage, except for the first year. The application of 100 g ha−1 Se in FHY, DHY, DLY, AA, and TPC properties emerged as the recommended dose since it reached the highest values. In addition, it was evaluated that the Se application did not have a statistically significant effect on the SCP. For years with statistical significance, 400 g ha−1 Se application was recommended in terms of AAC and 100 g ha−1 Se application in terms of AA and TPC.

Selenium Application Provides Nutritional and Metabolic Benefits to Wheat Plants

Selenium is beneficial to plants and is essential for animals and humans, which justifies any efforts for producing Se-enriched wheat grains worldwide. This study aimed to (i) verify if wheat is an efficient species to be used for Se biofortification in tropical agroecosystems and (ii) assess the influence of Se on the physiological and biochemical parameters of wheat plants. Selenium was applied as sodium selenate (Na2SeO4) at different doses (12, 21, 38, 68, and 120 g ha−1) in soil. The dose of 120 g ha−1 of Se resulted in Se contents of 7.98 and 2.27 mg kg−1 in the leaves and grains, respectively. The supply of 38 g ha−1 of Se increased the total soluble sugar content by 50%, with reducing sugars increasing by 17% and sucrose augmenting 53%, compared with that in the control. The doses of 12, 68, and 120 g of Se ha−1 promoted a significant increase in catalase activity. In addition, Se application increased carbohydrate and nutrient contents. Our findings indicate that wheat is a good species for agronomic biofortification with Se via soil application in tropical agroecosystems. Selenium proved to be a valuable element for plants since it provides physiological and biochemical benefits.

Selenium Fertilizer Improves Microbial Community Structure and Diversity of Rhizospheric Soil and Selenium Accumulation in Tomato Plants

ABSTRACT Selenium (Se) is an essential microelement in living organisms, and has a beneficial effect on plant growth and stress tolerance at low concentrations. Se biofortification is commonly practiced in agriculture and is considered the best method for increasing human Se uptake. This study aimed to investigate the effects of Se fertilizer application on Se accumulation and microbial communities in the rhizospheric soil of tomato plants. A pot experiment with five treatments, i.e. (a) non-Se fertilizer as control (Ck) and Se fertilizer in the form of (b) sodium selenite (1 mg kg−1), (c) sodium selenite (5 mg kg−1), (d) sodium selenate (1 mg kg−1), and (e) sodium selenate (5 mg kg−1) was set up. The results showed that Se content in the tomato plants’ parts gradually increased with an increasing concentration of sodium selenate or selenite. Sodium selenate significantly increased tomato yield and improved Se accumulation in tomato plants. Se-treated treatments decreased the abundance of soil microbial community, and had no effect on the Chao1 and Shannon indices of them. Furthermore, Se application increased the relative abundance of Acidobacteriota and Actinobacteriota involved in the decomposition of organic matter, reducing Bacteriodota and Ascomyta, and significantly affected the bacterial community structure. Thus, Se fertilizer application increased the crop yield, improved Se accumulation, and the structure and diversity of rhizospheric soil microbial community in the tomato plants. In line with our experiment, 5 mg kg−1 concentration selenate is a reasonable way to harvest Se-enriched tomatoes.

Nanoparticles synergy: Enhancing wheat (Triticum aestivum L.) cadmium tolerance with iron oxide and selenium

Nanotechnology is capturing great interest worldwide due to their stirring applications in various fields and also individual application of iron oxide nanoparticle (FeO − NPs) and selenium nanoparticles (Se − NPs) have been studied in many literatures. However, the combined application of FeO and Se − NPs is a novel approach and studied in only few studies. For this purpose, a pot experiment was conducted to examine various growth and biochemical parameters in wheat (Triticum aestivum L.) under the toxic concentration of cadmium (Cd) i.e., 50 mg kg−1 which were primed with combined application of two levels of FeO and Se − NPs i.e., 15 and 30 mg L−1 respectively. The results showed that the Cd toxicity in the soil showed a significantly (P < 0.05) declined in the growth, gas exchange attributes, sugars, AsA-GSH cycle, cellular fractionation, proline metabolism in T. aestivum. However, Cd toxicity significantly (P < 0.05) increased oxidative stress biomarkers, enzymatic and non-enzymatic antioxidants including their gene expression in T. aestivum. Although, the application of FeO and Se − NPs showed a significant (P < 0.05) increase in the plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress, and Cd uptake. In addition, individual or combined application of FeO and Se − NPs enhanced the cellular fractionation and decreases the proline metabolism and AsA − GSH cycle in T. aestivum. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

Selenium treatment alters the accumulation of osmolytes in arsenic-stressed rice (Oryza sativa L.).

Arsenic (As), one of the major pollutants in the soil, is an important environmental concern as its consumption can cause adverse health symptoms in living organisms. Its contamination of rice grown over As-contaminated areas is a serious concern in South Asian countries. Selenium (Se) has been reported to influence various osmolytes under metal stress in plants. The present study reports the role of Se in mitigating As stress in rice by modulating osmolyte metabolism. Rice plants grown in As-amended soil (2.5-10mgkg-1) in pots were treated with sodium selenate (0.5-1.0mg Se kg-1 soil) in glass house conditions and leaf samples were collected at 60 and 90days after sowing (DAS). As-treated rice leaves displayed a reduction in relative water content (RWC) and dry weight than control with a maximum reduction of 1.68- and 2.47-fold in RWC and 1.95- and 1.69-fold in dry weight in As10 treatment at 60 and 90 DAS, respectively. Free amino acids (1.38-2.26-fold), proline (3.88-3.93-fold), glycine betaine (GB) (1.27-1.72-fold), choline (1.67-3.1-fold), total soluble sugars (1.29-1.61-fold), and reducing sugars (1.67-2.19-fold) increased in As-treated rice leaves as compared to control at both stages. As stress increased the γ-aminobutyric acid (GABA), putrescine content, and glutamate decarboxylase activity whereas diamine oxidase and polyamine oxidase activities declined by 1.69-1.88-fold and 1.52-1.86-fold, respectively. Se alone or in combination with As improved plant growth, RWC, GB, choline, putrescine, and sugars; lowered proline and GABA; and showed a reverse trend of enzyme activities related to their metabolism than respective As treatments. As stress resulted in a higher accumulation of osmolytes to combat its stress which was further modulated by the Se application. Hence, the current investigation suggested the role of osmoprotectants in Se-induced amelioration of As toxicity in rice plants.

Increasing the resistance of the hollyhock plant to cold stress: silicon or selenium

It is well-known that freezing affects crop growth worldwide and significantly reduces crop production in the affected regions. The study objective was to investigate the effect of sodium silicate and sodium selenite individually or in combination on Alcea rosea plants grown under cold temperature stress. In this work, hollyhock plants were grown with sodium selenite and sodium silicate to 1/2 Hoagland solution, including 1) control, 1 mM sodium sulfate, 2) 1 mM sodium silicate 3), 0.03 mM sodium selenite, 4) 1 mM sodium silicate + 0.03 mM sodium selenite and exposed to nonfreezing (20 °C) and freezing temperature (−4 °C). Nutritional elements, photosynthesis parameters, electrolyte leakage, malondialdehyde, water content, osmolytes, and antioxidant enzymes were determined. The application of Si + Se effectively enhanced the Si and Se content of leaves (54% and 164%) compared to control plants. The combined Si and Se addition increased phenols, water-soluble sugars, proline, chlorophyll, net photosynthesis (Pn), and stomatal size under cold stress. Moreover, Si and Se in combination in stressed plants inhibited electrolyte leakage and malondialdehyde (MDA) by increasing the activities of enzymes such as superoxidase dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). The maximal to minimal values of essential oil content, relative water content (RWC), and stomatal density depended on the treatment: Si + Se > Si = Se. By increasing K content, phenol, proline, and water-soluble sugars, Si + Se > Si > Se application decreased the adverse effects of cold stress on the dry weight of the hollyhock.

Selenium biofortification impacts nutritional composition and storage proteins in wheat grains

Selenium (Se) biofortification of staple crops can be used as a valuable pathway to prevent Se deficiency in human diet. In this study, a pot experiment was performed under semi-controlled conditions to investigate the response of indigenous wheat cultivars to different Se concentrations (0 to 100 mg L-1) and to also assess the effects of Se foliar application on the storage proteins in wheat grains. A linear increase in Se concentrations in the grains of various wheat cultivars was observed (up to 158 μg kg-1) in response to Se application rates. It was observed that Gandum-1, Fakhar-e-Bhakkar-17, Ujala-16 and Anaj-17 were the most responsive wheat cultivars to Se application rates and accumulated the highest Se concentrations in grains. Though Se foliar treatments did not significantly affect the wheat yield, a highly significant correlation was observed between the Se application rates and the concentration of mineral nutrients (iron, zinc, calcium and potassium). Moreover, the exogenous Se supply considerably enhanced the concentrations of different storage proteins viz. albumin, globulin, prolamin and glutelin in wheat grains. The target hazard quotient of all Se application rates was found less than the toxic levels. In conclusion, wheat cultivars differ in their ability to accumulate Se concentrations in grains and biofortifying the most responsive wheat cultivars could be used as an efficient agronomic strategy to overcome widespread Se deficiency in human population.

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.

DNA demethylation by transitory 5‐azacytidine treatment improves somatic embryogenesis yield for regeneration and breeding of cork oak

AbstractSomatic embryogenesis (SE) is a crucial biotechnological tool for large‐scale mass propagation of selected material, genetic transformation and breeding, with many advantages for forest tree improvement. However, the application of SE in forest species is limited because of their recalcitrance. SE is also a valuable system for studying cell reprogramming, acquisition of totipotency and embryo development. Increasing evidence reveals that epigenetic reprogramming takes place during SE through DNA methylation, although there is scarce information on forest species. In this work, we have evaluated DNA methylation dynamics during SE and the effects of the DNA demethylating agent 5‐azacytidine (AzaC) in cork oak. After induction and early stages of SE, a reduced DNA methylation level is observed, followed by an increase of methylation during embryo differentiation. These changes in DNA methylation during SE progression were associated with expression profiles of DNA methyltransferase genes QsMET1, QsDRM2 and QsCMT3, and DNA demethylase QsDME‐like. Treatment with AzaC reduced DNA methylation, promoted SE induction rate and proembryogenic masses proliferation, and induced the expression of the SE marker gene QsSERK1‐like. However, continuous AzaC treatment hindered embryo differentiation, suggesting that DNA methylation is needed for further embryo development. Interestingly, AzaC removal from the culture medium of embryogenic masses restored embryo development and led to a significant increase in somatic embryo production compared with untreated cultures. These findings open new possibilities using transitory treatments with small molecule epigenetic modulators, as AzaC, to enhance SE yields for forestry breeding programs.

Control location could confuse the evaluation of passivation effect of iron-based biochar and selenium application on wheat grain cadmium accumulation

Inhibiting cadmium (Cd) accumulation in wheat grain could reduce the risk of Cd exposure to human. This study conducted a field experiment and evaluated the effect of iron-based biochar and selenium (Se) application individually or together on Cd accumulation in wheat grains in Cd contaminated soils. Considering the soil Cd heterogeneity in field, we set up 13 replicates of control (CK) and three replicates of each treatment. Results clearly showed that CK location could greatly affect the evaluation whether the difference in the wheat grain Cd concentration between treatments and CK was significant. When we assessed the difference between the treatments (foliar and soil application of Se, iron-based biochar application) and the adjacent CK, there was insignificant difference in the wheat grain Cd concentration between treatment and CK groups. Although soil application of 2 mg kg-1 Se or foliar application of 4 mg L-1 Se significantly increased the grain Se concentration as compared with the adjacent CK, but they still could not reduce the Cd concentrations in wheat grain. However, when we selected the CK that had the highest averaged grain Cd concentration, foliar and soil application of Se could significantly reduce the wheat grain Cd concentration by 47.7% and 41.3-46.1%, respectively. No matter which CK was selected, application of Fe-based biochar had no significant impact on Cd accumulation in wheat grain, and there was insignificant difference in DTPA-Cd concentrations between the iron-based biochar treatment and adjacent control. In conclusion, applying Fe-based biochar and Se in the field could not reduce the Cd accumulation in wheat grain in Cd contaminated weakly alkaline soils.

Exogenous application of selenium on sunflower (Helianthus annuus L.) to enhance drought stress tolerance by morpho-physiological and biochemical adaptations.

Drought stress poses a significant obstacle to agricultural productivity, particularly in the case of oilseed crops such as sunflower (Helianthus annuus L.). Selenium (Se) is a fundamental micronutrient that has been recognized for its ability to enhance plant resilience in the face of various environmental stresses. The FH-770 sunflower variety was cultivated in pots subjected to three stress levels (100% FC, 75% FC, and 50% FC) and four Se application rates (0 ppm, 30 ppm, 60 ppm, and 90 ppm). This research aimed to investigate the effect of exogenously applied Se on morpho-physiological and biochemical attributes of sunflower to improve the drought tolerance. Foliar Se application significantly lowered H2O2 (hydrogen peroxide; ROS) (20.89%) accumulation that markedly improved glycine betaine (GB) (74.46%) and total soluble protein (Pro) (68.63%), improved the accumulation of ascorbic acid (AA) (25.51%), total phenolics (TP) (39.34%), flavonoids (Flv) (73.16%), and anthocyanin (Ant) (83.73%), and improved the activity of antioxidant system superoxide dismutase (SOD) (157.63%), peroxidase (POD) (100.20%), and catalase (CAT) (49.87%), which ultimately improved sunflower growth by 36.65% during drought stress. Supplemental Se significantly increased shoot Se content (93.86%) and improved calcium (Ca2+), potassium (K+), and sodium (Na+) ions in roots by 36.16%, 42.68%, and 63.40%, respectively. Selenium supplements at lower concentrations (60 and 90 ppm) promoted the growth, development, and biochemical attributes of sunflowers in controlled and water-deficient circumstances. However, selenium treatment improved photosynthetic efficiency, plant growth, enzymatic activities, osmoregulation, biochemical characteristics, and nutrient balance. The mechanisms and molecular processes through which Se induces these modifications need further investigation to be properly identified.

Hydrothermal synthesis and characterization of selenium-doped MoS2 for enhanced optoelectronic properties

Transition metal dichalcogenides show layered crystal structure with Van der Waals forces spanning the adjacent layers. Robust covalent bonds within each 2D sheet contribute to their outstanding electrical and optical properties. The incorporation of a chalcogen atom as a composite leads to enhanced optical and electrical characteristics of the TMDs, which could make them potential candidates for opto-electronic applications. In the present study, we have described the synthesis and characterizations of Se doped MoS2 nanolayers using a facile one-step hydrothermal method. XRD analysis revealed the diffraction peaks corresponding to MoS2 as well as Se which suggested the successful incorporation of selenium into MoS2 nanolayers. Optical analysis revealed an increased band gap of 1.01 eV after the addition of selenium, determined through UV-visible spectroscopy with a refractive index of 3.36. The morphological analysis by FESEM showed the formation of nanolayers and the EDX pattern showed the presence of Mo, S and Se. The enhanced bandgap of the as-synthesized material and the increased absorption in the UV region ensures its usage for the fabrication of efficient broadband photodetectors. Our future research focuses on the potential application of Se doped MoS2 nanolayers in the field of efficient photodetectors.

Interactive effects of selenium and arsenic on phenolic constituents and antioxidant activity in rice (Oryza sativa L.)

Arsenic (As) is a heavy toxic metalloid found in air, water and soil that adversely affects the plant growth by inducing oxidative stress in plants. Its contamination of rice is a serious problem throughout the world. Selenium (Se) is a beneficial micronutrient for plants that acts as an antioxidant at low doses and protect the plants against number of environmental stresses either by modulating the primary metabolic pathways or regulating the production of phenolic compounds. In the present investigation, effect of Se on different phenolics, enzymes related to their metabolism and antioxidative potential were studied in As stressed rice leaves. Rice plants were grown in pots containing sodium arsenate (2–10 mg As(V) kg−1 soil) and sodium selenate (0.5–1 mg Se kg−1 soil), both alone and in combination and leaf samples were analyzed for various biochemical parameters. Phenolic constituents increased in rice leaves with As(V) treatment from 2 to 5 mg kg−1 soil and leaves exposed to As(V) @ 5 mg kg−1 soil exhibited 1.7, 1.9 and 2.5 fold increase in total phenolics, o-dihydroxyphenols and flavonols, respectively at grain filling stage. Binary application of Se + As improved various phenolic constituents, FRAP, reducing power and antioxidant activities as compared to control. PAL, TAL and PPO activities increased from 1.3 to 4.6 fold in combined As + Se treatment at both the stages. Anthocyanin contents showed a decline (10.8 fold) with increasing As doses and its content improved at both the stages with maximum increase of 3.76 fold with As5+Se1 combination. Binary application of As + Se improved gallic acid, chlorogenic acid, 3-hydroxy benzoic acid and kaempferol contents than control whereas catechin and coumaric acid showed the reverse trend. Application of Se can modulate phenolic constituents in leaf and grains of rice Cv PR126 due to As stress that helped plants to adapt to excess As and resulted in improved plant growth.

Alterations in the multilevel structure and depolymerization behavior of gluten induced by selenium in fermented dough

This study was conducted to evaluate the alterations of multilevel structure of gluten induced by selenium (Se) and their relationship with the properties of the fermented dough. The results of molecular weight distributions indicated that the degree of gluten aggregation decreased as the Se content in the fermented dough increased. Moreover, the elevated Se content led to a higher percentage of β-sheet in the dough proteins, indicating a more stable structure after depolymerization. Intermolecular interactions indicated that Se disrupted covalent cross-linking between gluten by affecting disulfide (SS) bonds. The levels of glutathione (GSH), free sulfhydryl and SS bond in the dough increased with increasing Se content. This suggested that more GSH was produced by Se induced yeast, which reacted with intermolecular SS in gluten, resulting in reduced gluten cross-linking. Meanwhile, Se affected the viscoelasticity and enhanced the height of the fermented dough. Improved quality of the steamed bread was found with even pore distributions and reduced hardness. This study has the potential to expand the application of Se in the fermented food industry and offer practical ways to increase Se consumption in Se-deficient areas.

Remediation potential of biochar and selenium for mitigating chromium-induced stress in spinach to minimize human health risk

The contamination of agricultural soils with metals and metalloids significantly affects crop productivity. The objective of the present study was to investigate how the combined application of biochar and selenium (Se) could mitigate the adverse effects of chromium (Cr) stress on spinach. The effects of selenium (Na2SeO4) (1 mg L − 1) and biochar (5 %, w/w) application both individually and in combination were evaluated on the basis of growth, physio-biochemical and antioxidant potential of spinach grown under Cr stress (100 µM [29.40 mg] using K2Cr2O7 of soil) and without Cr stress as control (0 µM). The results indicated that Cr stress decreased the root length (34.62 %), shoot length (35.32 %), number of leaves (23.18 %), root dry weight (12.00 %), and leaf dry weight (24.36 %) under Cr stress by lowering relative water content (RWC) and chlorophyll concentrations due to increased electrolyte leakage (64.03 %) and the Cr accumulation in leaves. However, the combined application of biochar and Se significantly enhanced the fresh and dry biomass under Cr stress and control conditions. The synergistic effect of Se and biochar partly alleviates the effects of Cr stress in spinach by up-regulating the antioxidant system, reducing lipid peroxidation (60.00 %), increasing leaf soluble sugars (25.22 %), and simultaneously decreasing electrolyte leakage. The combined effect of Se and biochar proved better results as compared to the sole application in minimizing Cr uptake in leaves (52.08 %) and limiting the health risk assessment values. Overall, this study highlights that the combined application of biochar and Se is an innovative and eco-friendly approach to improving the physio-biochemical defense responses against Cr stress in spinach plants.

The effects of in ovo feeding of selenized glucose on liver selenium concentration and antioxidant capacity in neonatal broilers

Selenium is an essential trace element for humans and animals. As the active center of selenoproteins, the addition of selenium is beneficial to enhance the antioxidant ability. However, the high cost limits the application of organic Se in agriculture animal production. Selenized glucose (SeGlu) is a newly invented organoselenium material with good stability, low toxicity and low cost. This assay found that SeGlu was able to increase selenium deposition in liver of newborn broilers, and enhance the antioxidant capacity of liver by elevating the activities of antioxidant enzymes such as total superoxide dismutase and glutathione peroxidase. This paper as the first example clarifying the mechanism of SeGlu to enhance the antioxidant ability of chicks, shows that SeGlu can be used as an organic selenium enrichment additive for early nutrition of poultry. As a cross-discipline study involving chemistry, biology and agriculture animal science, the work may be beneficial for studies in related fields and prompt the development of the selenium science.

Computational and experimental analysis of foxtail millet under salt stress and selenium supplementation.

Salinity stress is a major threat to crop growth and productivity. Millets are stress-tolerant crops that can withstand the environmental constraints. Foxtail millet is widely recognized as a drought and salinity-tolerant crop owing to its efficient ROS scavenging mechanism. Ascorbate peroxidase (APX) is one of the reactive oxygen species (ROS) scavenging enzymes that leads to hydrogen peroxide (H2O2) detoxification and stabilization of the internal biochemical state of the cell under stress. This inherent capacity of the APX enzyme can further be enhanced by the application of an external mitigant. This study focuses on the impact of salt (NaCl) and selenium (Se) application on the APX enzyme activity of foxtail millet using in silico and in-vitro techniques and mRNA expression studies. The NaCl was applied in the concentrations, i.e., 150mM and 200mM, while the Se was applied in 1μM, 5μM, and 10μM concentrations. The in silico studies involved three-dimensional structure modeling and molecular docking. The in vitro studies comprised the morphological and biochemical parameters, alongside mRNA expression studies in foxtail millet under NaCl stress and Se applications. The in silico studies revealed that the APX enzyme showed better interaction with Se as compared to NaCl, thus suggesting the enzyme-modulating role of Se. The morphological and biochemical analysis indicated that Se alleviated the NaCl (150mM and 200mM) and induced symptoms at 1µM as compared to 5 and 10µM by enhancing the morphological parameters, upregulating the gene expression and enzyme activity of APX, and ultimately reducing the H2O2 content significantly. The transcriptomic studies confirmed the upregulation of chloroplastic APX in response to salt stress and selenium supplementation. Hence, it can be concluded that Se as a mitigant at lower concentrations can alleviate NaCl stress in foxtail millet.

Effect of Foliar Application of Silicon and Selenium on the Growth, Yield and Fruit Quality of Tomato in the Field

Tomato (Solanum lycopersicon) is a widely produced and consumed fruit vegetable worldwide. Silicon (Si) and selenium (Se) can promote crop growth and development. However, the effects of these elements on tomato fruit quality have not been investigated comprehensively, nor are their combined effects on yield and quality clear. The aim of this study was to investigate the effects of foliar application of Si and Se on tomato growth, yield and fruit quality. The tomato plants were foliarly applied with 1 mM Si and 25 μM Se individually or in combination, and the experiment was carried out in a plastic arch shed at Yangling in spring. Our results demonstrated improved plant growth by application of Si and Se, with the effect of combined treatment being more obvious. Application of Si individually or in combination with Se increased the yield. Se addition increased the concentrations of soluble sugars, vitamin C, phenols, anthocyanin, lycopene, carotenoids, Se and protein, and decreased the nitrate level, but did not affect the concentration of total organic acids in the fruit. Si application induced similar changes to Se addition in the levels of sucrose and protein in the fruit, but had no effect on other quality traits. The combined Si and Se treatment did not show significant superior effects on the fruit quality over their individual applications. Our results suggest that Si and Se application improved the tomato plant growth. Si and Se application, respectively, had obvious effects in the yield increase and quality improvement, and the combined treatment had positive effects on both aspects. The study may provide a theoretical base for the application of Se and Si fertilizers in tomato production.

Selenium foliar application contributes to decrease ratio of water-soluble fluoride and improve physio-biochemical components in tea leaves

The tea plant accumulates elevated levels of fluoride (F) from environmental sources. Drinking tea containing high F levels poses a potential threat to human health. Selenium (Se) was applied by foliar spray to investigate its effects on F accumulation and physiology in tea plant. Foliar application of different forms of Se, i.e., Na2SeO3, Kappa-selenocarrageenan, Selenomethionine and Nanoselenium, reduced F content in tea leaves by 10.17 %−44.28 %, 16.12 %−35.41 %, 22.19 %−45.99 % and 22.24 %−43.82 %, respectively. Foliar spraying Se could increase F accumulation in pectin through increasing pectin content and pectin demethylesterification to bind more F in the cell wall, which decreased the proportion of water-soluble fluoride in tea leaves. Application of Se significantly decreased the contents of chromium (39.6 %−72.0 %), cadmium (48.3 %−84.4 %), lead (2.2 %−44.4 %) and copper (14.1 %−44.6 %) in tea leaves. Foliar spraying various forms of Se dramatically increased the Se content and was efficiently transformed into organic Se accounting for more than 80 % in tea leaves. All Se compounds increased peroxidase activity by 3.3 %−35.5 % and catalase activity by 2.6 %−99.4 %, reduced malondialdehyde content by 5.6 %−37.1 %, and increased the contents of chlorophyll by 0.65 %−31.8 %, carotenoids by 0.24 %−27.1 %, total catechins by 1.6 %−21.0 %, EGCG by 4.4 %−17.6 % and caffeine by 9.1 %−28.6 %. These results indicated that Se application could be served as a potential efficient and safe strategy diminishing the concentration of F in tea leaves.