The roles of selenium in protecting plants against abiotic stresses

Se improves Cd tolerance by modulating phytohormone signaling and primary metabolism in strawberry

Cadmium (Cd) pollution leads to reduced crop yields and poses a threat to human health, making it an important environmental and agricultural safety issue. Selenium [Se(IV)] has been shown to alleviate Cd stress in plants; however, the mechanisms underlying Se-mediated protection against Cd toxicity remain largely unclear. In this study, we investigated the physiological and molecular mechanisms of Se(IV)-alleviated Cd toxicity in strawberry plants through physio-biochemical and transcriptomic analyses. Our results showed that foliar spraying with Se(IV) increased photosynthetic efficiency, reduced Cd-induced oxidative damage by enhancing antioxidant enzyme activities and soluble sugar contents, thereby improving Cd stress tolerance. Transcriptomic profiling revealed 477 common differentially accumulated transcripts (DATs), predominantly enriched in transporter activity, oxidoreductase function, and antioxidant-related processes. Notably, seven key genes involved in Cd efflux, chelation, secondary metabolite transport and nutrient uptake (FvPCR9-like, FvCBP-like, FvWAT1-like, FvMOT1, FvYW_6g02140, FvNRT2.1 and FvZIP8) exhibited opposite expression patterns under Se(IV) and Cd treatments. Supplementation with Se(IV) also modulated phytohormone signaling, nitrogen metabolism and carbon metabolism pathways, providing a multi-dimensional approach to mitigating Cd-induced physiological disruptions. This study provides novel insights into Se(IV)-mediated Cd stress adaptation, and offers promising strategies for developing low-Cd-accumulating crops, addressing critical environmental and agricultural challenges associated with heavy metal contamination.

Lignin-containing cellulose nanofiber-selenium nanoparticle hybrid enhances tolerance to salt stress in rice genotypes

Soil salinization poses a significant challenge for rice farming, affecting approximately 20% of irrigated land worldwide. It leads to osmotic stress, ionic toxicity, and oxidative damage, severely hindering growth and yield. This study investigates the potential of lignin-containing cellulose nanofiber (LCNF)-selenium nanoparticle (SeNPs) hybrids to enhance salt tolerance in rice, focusing on two rice genotypes with contrasting responses to salt stress. LCNF-SeNP hybrids were synthesized using a microwave-assisted green synthesis method and characterized through FTIR, X-ray diffraction, SEM, TEM, and TGA. The effects of LCNF/SeNPs on seed germination, physiological responses, and gene expression were evaluated under varying levels of NaCl-induced salt stress. Results indicated that LCNF/SeNPs significantly enhanced the salt tolerance of the salt-sensitive genotype IR29, as evidenced by increased germination rates, reduced salt injury scores, and higher chlorophyll content. For the salt-tolerant genotype TCCP, LCNF/SeNPs improved shoot lengths and maintained elevated chlorophyll levels under salt stress. Furthermore, LCNF/SeNPs improved ion homeostasis in both genotypes by reducing the Na+/K+ ratio, which is crucial for maintaining cellular function under salt stress. Gene expression analysis revealed upregulation of key salt stress-responsive genes, suggesting enhanced stress tolerance due to the application of LCNF/SeNPs in both genotypes. This study underscores the potential of LCNF/SeNPs as a sustainable strategy for improving crop performance in saline environments.

Physio-biochemical insights into Arsenic stress mitigation regulated by Selenium nanoparticles in Gossypium hirsutum L

Arsenic is a nonessential toxic metalloid hampering the growth and development of plants. The cotton (Gossypium hirsutum) is of great economic importance in the textile industry as well as in the production of edible oil. In developing countries, especially Pakistan, the export of cotton has a distinct position. However, there has been a significant decline in cotton production over the past few years due to climate change, heavy metals induction and biotic stresses. A notable decrease in cotton growth and product is observed in response to arsenic stress. Selenium nanoparticles (Se NPS) were prepared by green chemistry approach and characterized by UV-Vis, FTIR, and XRD to mitigate the heavy metals induced toxicity in cotton seedling. Results shows that arsenic toxicity causes a drastic decrease in photosynthesis, phenolics, proteins, growth of seedlings, relative water content, and overall plant biomass. However, these physio-biochemical attributes were upregulated by applications of Se NPs. Moreover, As stress causes severe oxidative damage by overproduction of MDA, H2O2 and reactive oxygen species (ROS). The supplementation of SeNPs positively regulate the As stress in cotton seedlings by altering important antioxidant enzymes involved in ROS detoxification such as SOD, POD, and CAT. Se NPs ameliorate the toxicity by increasing activities of enzymatic and non-enzymatic antioxidants. The accumulation of As in roots alter the architecture of roots including reduced branching of roots. Current results suggest that the applications of selenium nanoparticles especially 20 mg/L concentration confidently alleviate the As induced toxicity in cotton seedlings.

Growth and selenium bioaccumulation in rape seedlings promoted by strain Limosilactobacillus sp. LF-17

Selenium (Se) is an essential trace element that plays a critical role in human tissue formation, metabolism, and physiological functions. However, many individuals worldwide suffer from Se deficiency diseases. This study aims to evaluate the impact of Se-tolerant LF-17 agents and exogenous Na2SeO3 application on the growth, enzyme activity, and metabolic characteristics of rape seedlings. Treatment LF-3 (inoculation of Se-tolerant LF-17 agent and exogenous Na2SeO3, with the soil Se concentration of 5 mg/kg) led to a 38.62% increase in plant height and a 116.7% increase in fresh weight. And the Se-tolerant LF-17 agent in treatment LF-3 also reduced the oxidative stress induced by exogenous Na2SeO3 compared to that of treatment LF-2 (with the same amount exogenous Na2SeO3 only), as evidenced by the lower activities of SOD, POD, and CAT, as well as less content of malondialdehyde. Furthermore, the upregulation of metabolic pathways such as "cuticle, suberine, and wax biosynthesis" "flavonoid biosynthesis," and "terpenoid backbone biosynthesis" enhanced the plant's stress resistance as revealed by non-targeted metabolomics sequencing method. This approach offers promising applications for improving Se bioavailability in crops, mitigating Se toxicity, addressing global Se deficiency challenges and is expected to contribute to fulfilling the Se supplementation needs of the population.

Contributions of nitrogen metabolic enzymes in storage protein assimilation and mineral accumulation regulated by nitrogen and selenium in Triticum aestivum L

Selenium (Se) is a key mineral element beneficial for normal plant development. However, the importance of Se in altering nitrate reductase (NR) and nitrite reductase (NiR) activities to enhance grain storage protein abundance and mineral contents remains unclear. In this study, we assessed the positive responses of Se with various NO3- and NH4+ fertilizers on nutrient accumulation and storage proteins of wheat. Se (Na2SeO4) was applied as a foliar spray (75 mg Se L-1) and via fertigation (40 g Se ha-1) at grain filling stage (80 days after sowing) alongside three splits of the recommended level of different nitrogen (N) fertilizer sources (urea, calcium ammonium nitrate [CAN], nitrophos (NP) and ammonium sulfate [AS]). Foliar Se application combined with urea fertilization significantly increased NR and NiR activities in cv. Anaj-17 compared to urea application without Se. Storage protein fractions including albumin, globulin, prolamin, and glutelin were also higher with foliar Se supplementation + urea application compared to AS or CAN fertilization. Mineral accumulation in wheat grains was significantly enhanced, with increased concentrations of Se, iron (Fe), zinc (Zn), and potassium (K) observed following foliar Se application in cv. Anaj-17. Foliar Se spraying notably boosted mineral concentrations, particularly grain Se levels while the combination of various N fertilizers with Se supplementation resulted in marked variations. Moreover, photosynthetic rate (A), transpiration rate (E), stomatal conductance (Ci) and substomatal conductance (gs) were higher in cv. Anaj-17 than Ujala-16 when treated with foliar Se + urea fertilizer. While Se application had some influence on yield attributes, significant variations were observed in response to different N fertilizers. The yield attributes were affected to some extent by Se application while these characteristics varied significantly in response to different N fertilizers. In conclusion, Se supplementation as a foliar spray combined with urea as an N fertilizer considerably increased wheat grain protein fractions by boosting N metabolism enzymatic activities (NR and NiR) and increased mineral accumulation, thereby improving the nutritional value of wheat.

The effect of selenium biological enhancement on cucumber growth and powdery mildew control under greenhouse conditions

In this study, we clarified the effects of selenium fertilizer application on the growth of cucumber, explored the impact of exogenous selenium on the control of powdery mildew and its pathogens. Selenium-enriched ionic fertilizer and cucumber were selected as the test materials. A one-way, randomized design was adopted to set up four selenium solutions with concentrations of 0 mg/L, 3 mg/L, 6 mg/L, and 12 mg/L to investigate the effects of biofortification with different amounts of selenium concentrations on the growth of cucumber and the occurrence of powdery mildew in greenhouses. A leaf inoculation test was conducted by setting up three groups of treatments: water and fungicide (seedling fungicide) as the control groups, and 6 mg/L selenium-enriched ionic fertilizer as the treatment group. These treatments were selected to investigate the effect of selenium on the control of powdery mildew in greenhouse-grown cucumbers as well as the effect of selenium on the germination of powdery mildew pathogen spores. The results demonstrated that both the 6 mg/L and 12 mg/L selenium-enriched ionic fertilizer solutions had growth-promoting and yield-increasing effects on cucumber and that the difference in the growth-promoting effects of these treatments was insignificant. The 3 mg/L, 6 mg/L, and 12 mg/L treatments improved the nutritional quality of cucumber fruits, reducing the total acidity of the fruits and increasing the content of soluble proteins in the fruits; the 6 mg/L and 12 mg/L treatments increased the content of selenium in the fruits, and the difference in selenium enrichment between the two treatments was not significant. The 6 mg/L selenium solution had the greatest effectiveness in alleviating leaf photosynthesis inhibition by the powdery mildew fungus, in mitigating powdery mildew damage and in reducing the plant disease index. The results of the leaf inoculation trials revealed that at a concentration of 6 mg/L, the effects of the selenium-enriched ionic fertilizer were comparable to those of pharmaceutical treatments for powdery mildew disease. The activities of superoxide dismutase and peroxidase in all treatments tended to increase but then decreased within 72 h after pathogen inoculation. Nevertheless, selenium fertilizer treatment inhibited the germination of powdery mildew pathogen conidia, the number of conidial germination shoot tubes and mycelium formation.

Cadmium accumulation, sub-cellular distribution and interactions with trace metals (Cu, Zn, Fe, Mn) in different rice varieties under Cd stress

Rice (Oryza sativa L.) is a staple food in most Asian countries, although it serves as a significant carrier of cadmium (Cd) accumulation. Developing low-Cd accumulating rice varieties is crucial for minimizing Cd contamination in soil and rice grains while also mitigating harmful health consequences. In the present study examined the Cd accumulation and sub-cellular distribution of both high Cd (IR-50) and low Cd (White Ponni) rice varieties under Cd-treated hydroponic nutrient solutions. The results showed that under all Cd treatments, overall plant height, plant fresh and dry biomass reduced substantially in both rice varieties compared to the control. Both rice varieties accumulated more Cd in their roots than shoots, with IR-50 accumulating higher Cd levels. Iron (Fe) concentrations were higher in both roots and shoots of both rice varieties compared to other trace elements. Translocation factor (TF) values were < 1, indicating limited Cd translocation from roots to shoots. Cd was mainly distributed in the epidermis, cortex, and bulliform cells of both rice varieties roots, and shoots. The peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) enzymes activity significantly increased in both IR-50 and WP rice varieties when exposed to Cd treatment. The current study concluded that the IR-50 rice variety accumulated and distributed more Cd than the WP rice variety under different Cd treatments. As a result, WP exhibited higher Cd tolerance, while IR-50 became more susceptible to Cd stress.

Selenium Improves Yield and Quality in Prunella vulgaris by Regulating Antioxidant Defense, Photosynthesis, Growth, Secondary Metabolites, and Gene Expression Under Acid Stress

Prunella vulgaris, an essential component of traditional Chinese medicine, is suitable for growing in soil with a pH value ranging from 6.5 to 7.5. However, it is primarily cultivated in acidic soil regions of China, where its growth is frequently compromised by acidic stress. Selenium (Se) has been recognized for its potential to enhance stress tolerance in plants. However, its role in acid-stress-induced oxidative stress is not clear. In this study, the effects of varying Se concentrations on the growth and quality of P. vulgaris under acidic stress were investigated. The results showed that acid stress enhanced antioxidant enzyme activities, non-enzymatic antioxidant substances, and osmolyte content, accompanied by an increase in oxidant production and membrane damage. Furthermore, it decreased the photosynthetic capacity, inhibited root and shoot growth, and diminished the yield of P. vulgaris. In contrast, exogenous application of Se, particularly at 5 mg L-1, markedly ameliorated these adverse effects. Compared to acid-stressed plants, 5 mg L-1 Se treatment enhanced superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione peroxidase activities by 150.19%, 54.94%, 43.43%, and 45.55%, respectively. Additionally, soluble protein, soluble sugar, and proline contents increased by 11.75%, 23.32%, and 40.39%, respectively. Se application also improved root architecture and alleviated membrane damage by reducing hydrogen peroxide, superoxide anion, malondialdehyde, and electrolyte leakage levels. Furthermore, it significantly enhanced the photosynthetic capacity by elevating pigment levels, the performance of PSI and PSII, electron transfer, and the coordination of PSI and PSII. Consequently, plant growth and spica weight were significantly promoted, with a 12.50% increase in yield. Moreover, Se application upregulated key genes involved in flavonoid and phenolic acid metabolic pathways, leading to elevated levels of total flavonoids, caffeic acid, ferulic acid, rosmarinic acid, and hyperoside by 31.03%, 22.37%, 40.78%, 15.11%, and 20.84%, respectively, compared to acid-stressed plants. In conclusion, exogenous Se effectively alleviated the adverse effects of acid stress by improving the antioxidant system, growth, and photosynthetic capacity under acid stress, thus enhancing the yield and quality of P. vulgaris.

Transformation and accumulation of selenium nanoparticles in the soil-rice system under different water management

The effects of foliar application of selenium nanoparticles (SeNPs) on rice growth and Se accumulation has been studied, but soil application of SeNPs on rice Se uptake and its transformation in soil remain limited. Water management is a key agronomic practice in rice cultivation. This study examined the effects of varying water management regimes (continuous flooding [CF] and alternating wet and dry [AWD]) and concentrations (0, 0.5, and 2 mg·kg-1) of SeNPs on rice growth, Se accumulation, soil Se transformations, and bacterial communities in a pot experiment. Results revealed that soil-applied SeNPs enhanced growth and Se accumulation of rice. Compared with CF treatment, AWD treatment promoted the accumulation of Se in rice but decreased leaf photosynthetic activity and Se content in leaf organelles. After soil application of SeNPs, soil Se fractions were dominated by organic-bound Se (OM-Se) and residual Se (RES-Se). SeNPs in soil have higher transformation rate at low concentration and AWD water management. Water management and SeNP application jointly affected the rhizosphere bacterial community structure. 2 mg·kg-1 SeNPs increased Chloroflexi abundance by 12.3 % and 30.6 % in CF and AWD water management, respectively. The increase in Chloroflexi abundance facilitated the conversion of stable Se fractions (OM-Se and RES-Se) to active Se fractions (soluble Se and carbonate bound Se) in soil. The present study may provide theoretical support for Se biofortification in rice grown in Se-deficient regions.

Spatial distribution and driving factors of soil selenium on the Leizhou Peninsula, southern China

Selenium (Se) is an essential element for humans, playing a critical role in the functioning of the immune system. The global prevalence of dietary Se deficiency is a significant public health concern, largely attributed to the low levels of Se present in crops. The sufficient Se in plants and humans is determined by the presence of stable Se sources in the soil. The Leizhou Peninsula is an important agricultural region in China, but the concentration and spatial distribution of Se in its soils remain unclear. To address this issue, we analyzed Se concentration data from 3333 soil samples collected at the depth of 0-20 cm from the Leizhou Peninsula, covering an area of 13,225 km2. The results indicate that the mean soil Se concentration was 0.50 mg kg-1, with Se-enriched soils being widely distributed. This provides prospects for the development of Se-enriched crops. Using random forest (RF) modeling and correlation analysis, the clay minerals (Fe-Al oxides), chemical index of alteration (CIA), and soil organic carbon (SOC) have been identified as the principal determinants of Se distribution in soil. During the weathering processes of the basalts, Fe-Al oxides serve as a crucial factor in Se accumulation in the red soils. Furthermore, the tropical climate further contributes to increasing the degree of weathering and the proportion of clay minerals and SOC in the soil. Atmospheric deposition derived from marine and precipitation is another important factor that promotes Se flux into soils. In conclusion, the distribution pattern of Se is jointly determined by the weathering process of basalt and climatic conditions. The results of the geographically weighted regression (GWR) analysis revealed that SOC, Al2O3, TFe2O3 and CIA change spatially and exhibit a spatial non-stationarity relationship with Se. This study offers a theoretical foundation and practical guidance for the sustainable development of Se-enriched agriculture and similar climate settings worldwide.

Soil Application of Selenium in Wheat (Triticum aestivum L.) Under Water Stress Improves Grain Quality and Reduces Production Losses

Selenium (Se) is an essential element for humans. However, much of the world's human population is deficient in this element, which has become a public health problem. This study aimed to evaluate whether applying severe water stress to wheat plants (Triticum aestivum L.) could allow Se to reduce the production losses and increase the grain quality, thereby contributing to the reduction in hidden hunger. The experiment was conducted in a randomized block design with four replications in a 5 × 2 factorial scheme, with five doses of Se (0.00, 0.25, 0.50, 1.00, and 2.00 mg dm-3) and two irrigation conditions (with and without water deficit). When sodium selenate (Na2SeO4) was applied to the soil, the grains were rich in Se. Under low doses, there was an enrichment of the grains in sulfur, iron, copper, and zinc as well as total free amino acids and total soluble proteins, and lower losses in productivity under severe water stress. Higher doses decreased the concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2), increased the catalase activity, and increased the water use efficiency (WUE). Therefore, applying Se at a dose of 0.25 mg dm-3 is effective for the biofortification of wheat grains. It enhances grain nutritional quality, increases Se bioaccessibility, and reduces production losses under water stress conditions.

Foliar application of zinc and selenium regulates cell wall fixation, physiological and gene expression to reduce cadmium accumulation in rice grains

Zinc (Zn) and selenium (Se) are beneficial elements for crops, enhancing crop quality and alleviating heavy metal toxicity. However, there is limited research on the role of foliar Zn and Se in the mechanism of reducing cadmium (Cd) uptake in crops. A field experiment was conducted to investigate the effect on subcellular distribution, leaf antioxidant enzyme activities, and the transcriptional regulation in the process of Cd accumulation of rice grains after foliar applications of Zn, Se, and their mixed solutions (ZnSe). The results show that Zn and ZnSe reduced Cd content in the grains of three different rice (13.9 %-21.8 %/11.9 %-29.5 %) by enhancing the fixation capacity of Cd in the flag leaf by improving the binding efficiency between pectin and Cd in the cell wall. Increased flag leaf antioxidant enzyme activities further mitigated the toxic effects of Cd on rice, while Zn and ZnSe treatments upregulated genes related to metal-binding proteins and antioxidant enzymes and downregulated metal transport genes. This study systematically elucidates the mechanisms by which foliar application of ZnSe alleviates Cd toxicity through the regulation of gene expression and physiological functions, providing a theoretical basis for reducing Cd accumulation in rice and ensuring the safe production of food.

Hazardous or Advantageous: Uncovering the Roles of Heavy Metals and Humic Substances in Shilajit (Phyto-mineral) with Emphasis on Heavy Metals Toxicity and Their Detoxification Mechanisms

Shilajit is a phyto-mineral diffusion and semi-solid matter used as traditional medicine with extraordinary health benefits. This study provides a comprehensive data on Shilajit with emphasis on heavy metal profile, associated toxicities, and metal detoxification mechanisms by humic substances present in Shilajit. Data was searched across papers and traditional books using Google Scholar, PubMed, Science Direct, Medline, SciELO, Web of Science, and Scopus as key scientific databases. Findings showed that Shilajit is distributed in almost 20 regions of the world with uses against 20 health problems as traditional medicine. With various humic substances, almost 11 biological activities were reported in Shilajit. This phyto-mineral diffusion possesses around 65 heavy metals including the toxic heavy metals like Cu, Al, Pb, As, Cd, and Hg. However, humic substances in Shilajit actively detoxify around 12 heavy metals. The recommended levels of heavy metals by WHO and FDA in herbal drugs is 0.20 and 0.30 ppm for Cd, 1 ppm for Hg, 10.00 ppm for As and Pb, 20 ppm for Cu, and 50 ppm for Zn. The levels of reported metals in Shilajit were found to be lower than the permissible limits set by WHO and FDA, except in few studies where exceeded levels were reported. Shilajit consumption without knowing permissible levels of metals is not safe and could pose serious health problems. Although the humic substances and few metals in Shilajit are beneficial in terms of chelating toxic heavy metals, the data on metal detoxification still needs to be clarified.

The curious case of selenium hyperaccumulation in Coelospermum decipiens from the Cape York Peninsula (Queensland, Australia)

BACKGROUND AND AIMS

The tropical shrub Coelospermum decipiens (Rubiaceae) is an extreme selenium (Se) hyperaccumulator, reported to accumulate up to 1140 µg Se g-1 when found growing on soils with levels of Se below the limit of detection (i.e. <0.01 mg Se kg-1) leading to a bioconcentration factor of >100 000.

METHODS

Coelospermum decipiens plants were sampled from different populations in far north Queensland and analysed for Se concentrations. Plant material was subjected to synchrotron X-ray fluorescence microscopy (XFM) and synchrotron X-ray absorption spectroscopy (XAS) investigations to gain insights into the elemental distribution and chemical speciation of Se.

RESULTS

The foliar Se concentrations ranged from 100 to 1000 µg Se g-1, except for the seeds, which had up to 28 000 µg Se g-1. The soils from the Hope Vale area were locally Se-enriched up to 48 mg Se kg-1, but there was no relationship between soil and plant Se concentrations. Synchrotron XFM analysis revealed that Se was localized in the blade margin tissue of the younger leaves, whilst the XAS analysis determined that Se occurs as an organo-Se compound.

CONCLUSIONS

We report the occurrence of seleniferous soils in the Cape York Peninsula soils for the first time, which may partly explain the evolution of Se hyperaccumulation in C. decipiens. The extremely high concentrations of Se in the seeds is suggestive of a herbivory protection function. The capacity of this species to accumulate and hyperaccumulate Se from non-seleniferous soils is akin to that of other 'seed'-based accumulators, such as some members of the Lecythidaceae family.

Cooperation of selenium, iron and phosphorus for simultaneously minimizing cadmium and arsenic concentrations in rice grains

Cadmium (Cd) and arsenic (As), two toxic elements to humans, are ubiquitously coexisting contaminant found in paddy fields. The accumulation of Cd and As in rice, a major food source for many people around the world, can pose a serious threat to food safety and human health. Therefore, it is crucial to be aware of these contaminants and take adequate measures to reduce the accumulation of these two elements in rice. Developing an effective method to simultaneously reduce the accumulation of Cd) and As in rice is challenging. In this study, a pot experiment was conducted to investigate the synergistic effects of selenium (Se), iron (Fe) and phosphorus (P) on the uptake, transport and accumulation of cadmium and arsenic in rice by analyzing the physical and chemical properties of the soil, the elemental concentrations and their interrelationships in the rice tissues, and the composition and morphology of the iron plaque (IP). The results showed that the combined treatments of Se, Fe and P had positive effects on reducing Cd and As accumulation in rice, reducing Cd concentrations in brown rice by 3.86-51.88 % and As concentrations by 25.37-40.81 %. The possible mechanisms for the reduction of As and Cd concentrations in rice grains were: (i) Combined application of Fe, P and Se can effectively reduce the soil available Cd and As concentration. (ii) Combined application significantly improved the formation of IP at the tillering stage and increased the crystalline iron oxides in IP, promoting the deposition of SiO2 in rice roots, thereby effectively inhibiting the uptake of Cd and As by rice roots. (iii) Interplay and interaction between elements facilitated by transporter proteins could contribute to the synergistic mitigation of Cd and As by Se, Fe and P. This study provides a valuable new approach for effective control of Cd and As concentration of rice grown in co-contaminated soil.

Comparative Study on the Response of Hyssop (Hyssopus officinalis L.), Salvia (Salvia officinalis L.), and Oregano (Origanum vulgare L.) to Drought Stress Under Foliar Application of Selenium

Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.

Selenate simultaneously alleviated cadmium and arsenic accumulation in rice (Oryza sativa L.) via regulating transport genes

Cadmium (Cd) and arsenic (As) have contrasting biogeochemical behaviors in paddy soil, which posed an obstacle for reducing their accumulation in rice (Oryza sativa L.) simultaneously. In this study, selenate exhibited a more effective ability than selenite on simultaneous alleviation of Cd and As accumulation in rice under Cd-As co-exposure, and the mechanisms need to be further investigated. The results showed that selenate significantly decreased the root Cd and As contents by 59%-83% and 43%-72% compared to Cd-As compound exposure, respectively. Correspondingly, it significantly down-regulated the expression of uptake-related genes OsNramp5 (87.1%) and OsLsi1 (95.5%) in rice roots. Decreases in Cd (64.5%) and As (16.2%) contents in shoots were also found after selenate addition. Moreover, selenate may promoted the reduction of As(V) to As(Ⅲ) and As(III) efflux to the external medium, resulting in decreased As accumulation and As(Ⅲ) proportion in rice shoots and roots. In addition, selenate could promote the binding of Cd (by 14%-24%) and As (by 9%-15%) in the cell wall, and significantly reduced the oxidative stress by elevating levels of antioxidant enzymes (by 10%-105%) and thiol compounds (by 6%-210%). Additionally, selenate significantly down-regulated the expression of OsNramp1 (49.3%) and OsLsi2 (82.1%) associated with Cd and As transport in rice. These findings suggest selenate has the potential to be an effective material for the simultaneous reduction of Cd and As accumulation in rice under Cd-As co-contamination.

Foliar application of selenium and gibberellins reduce cadmium accumulation in soybean by regulating interplay among rhizosphere soil metabolites, bacteria community and cadmium speciation

Both selenium (Se) and gibberellins (GA3) can alleviate cadmium (Cd) toxicity in plants. However, the application of Se and GA3 as foliar spray to against Cd stress on soybean and its related mechanisms have been poorly explored. Herein, this experiment evaluated the effects of Se and GA3 alone and combined application on soybean rhizosphere microenvironment, Cd accumulation and growth of soybean seedlings. The results revealed that both Se and GA3 can effectively decrease the accumulation of Cd in soybean seedlings. Foliar application of Se, GA3 and their combination reduced Cd contents in soybean seedlings respectively by 21.70 %, 27.53 % and 45.07 % when compared with the control treatment, suggest a synergistic effect of Se and GA3 in decreasing Cd accumulation. Se and GA3 also significantly increased diversity and abundance of the metabolites in rhizosphere, which consequently played an important role in shaping rhizosphere bacteria community and improve rhizosphere soil physicochemical properties of Cd contaminated soil, as well as decreased the Cd available forms contents but enhance the immobilized form levels. Overall, this study affords a novel approach on mitigating Cd accumulation in soybean seedlings which is attributed to Se and GA3 regulated interplay among rhizosphere soil metabolites, bacteria community and cadmium speciation.

Foliar-selenium enhances plant growth and arsenic accumulation in As-hyperaccumulator Pteris vittata: Critical roles of GSH-GSSG cycle and arsenite antiporters PvACR3

It is known that selenium (Se) enhances plant growth and arsenic (As) accumulation in As-hyperaccumulator Pteris vittata, but the associated mechanisms are unclear. In this study, P. vittata was exposed to 50 μM arsenate (AsV) under hydroponics plus 25 or 50 μM foliar selenate. After 3-weeks of growth, the plant biomass, As and Se contents, As speciation, malondialdehyde (MDA) and glutathione (GSH and GSSG) levels, and important genes related to As-metabolism in P. vittata were determined. Foliar-Se increased plant biomass by 17 - 30 %, possibly due to 9.1 - 19 % reduction in MDA content compared to the As control. Further, foliar-Se enhanced the As contents by 1.9-3.5 folds and increased arsenite (AsIII) contents by 64 - 136 % in the fronds. The increased AsV reduction to AsIII was attributed to 60 - 131 % increase in glutathione peroxidase activity, which mediates GSH oxidation to GSSG (8.8 -29 % increase) in the fronds. Further, foliar-Se increased the expression of AsIII antiporters PvACR3;1-3;3 by 1.6 - 2.1 folds but had no impact on phosphate transporters PvPht1 or arsenate reductases PvHAC1/2. Our results indicate that foliar-Se effectively enhances plant growth and arsenic accumulation by promoting the GSH-GSSG cycle and upregulating gene expression of AsIII antiporters, which are responsible for AsIII translocation from the roots to fronds and AsIII sequestration into the fronds. The data indicate that foliar-Se can effectively improve phytoremediation efficiency of P. vittata in As-contaminated soils.

Application of selenium to reduce heavy metal(loid)s in plants based on meta-analysis

Agricultural soils are currently at risk of pollution from toxic heavy metal(loid)s (HMs) due to human activities, resulting in the excessive accumulation of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), lead (Pb) and zinc (Zn) in food plants. This poses significant risks to human health. Exogenous selenium (Se) has been proposed as a potential solution to reduce HMs accumulation in plants. However, there is currently a lack of comprehensive quantitative overview regarding its influence on the accumulation of HMs in plants. This study utilized meta-analysis to consolidate the existing knowledge on the impact of Se amendments on plant HMs accumulation from contaminated soil media. The present study conducted a comprehensive meta-analysis on literature published prior to December 2023, investigating the effects of different factors on HMs accumulation by meta-subgroup analysis and meta-regression model. Se application showed an inhibitory effect on plant uptake of Hg (28.9%), Cr (25.5%), Cd (25.2%), Pb (22.0%), As (18.3%) and Cu (6.00%) concentration. There was a significant difference in the levels of HMs between treatments with Se application and those without Se application in various plant organs. The percentage changes in the HMs contents of the organs varied from -13.0% to -22.0%. Compared with alkaline soil (pH > 8), Se application can reduce more HMs contents in plants in acidic soil (pH < 5.5) and neutral soil (pH = 5.5-8). For daily food plants(e.g. rice, wheat and corn), Se application can reduce HMs contents in Oryza sp., Triticum sp. and Zea sp., ranging from 14.0-20.0%. Our study emphasizes that the impact of Se on reducing HMs depends on the single or combined effects of Se concentration, plant organs, plant genera and soil pH condition.

Selenium improved arsenic toxicity tolerance in two bell pepper (Capsicum annuum L.) varieties by modulating growth, ion uptake, photosynthesis, and antioxidant profile

Bell pepper (Capsicum annuum L.); an important spice crop of the region is a rich source of vitamins and antioxidants having many health benefits. Many biotic and abiotic factors contribute towards growth and yield losses of this crop. Arsenic (As) toxicity is a global issue, but it is particularly critical in developing countries. The current study was designed to evaluate the efficacy of selenium (Se) in mitigating the toxic effects of As in two varieties (HSP-181 A and PS09979325) of Capsicum annuum L. Different concentrations of As (0, 50, and 100 µM) and Se (0, 5, and 10 µM) were tested using 14 days old seedlings of C. annuum L. The As stress caused a significant (P ≤ 0.001) reduction in growth, uptake of nutrients, and eco-physiological attributes in both varieties however, the response was specific. While the overproduction of osmo-protectants and antioxidants intensified the symptoms of oxidative stress. The maximum reduction in shoot length (45%), fresh weight (29%), and dry weight (36%) was observed in under 100 µM As stress. The organic acids exudation from the roots of both cultivars were significantly increased with the increase in As toxicity. The Se treatment significantly (p ≤ 0.001) improved growth, nutrient uptake, gas exchange attributes, antioxidant production, while decreased oxidative stress indicators, and As uptake in the roots and shoots of all the subjects under investigation. It is concluded from the results of this study that Se application increased photosynthetic efficiency and antioxidant activity while decreasing As levels, organic acid exudation, and oxidative stress indicators in plants. Overall, the var. PS09979325 performed better and may be a good candidate for future pepper breeding program.

Rhizosphere enrichment and crop utilization of selenium and metals in typical permian soils of Enshi

Enshi, China, is renowned as "Selenium(Se) Capital" where widely distributed soils derived from Permian parent rocks are notably rich in Se, as well as metals, particularly cadmium(Cd). However, the soil enrichment and crop uptake of Se and metals in these high-Se and high-Cd areas are not well understood. To propose the optimal crop planting plan to ensure the safety of agricultural products, we investigated the soils and corresponding typical crops (rice, tea, and maize). The results showed significant soil enrichment of elements, with average contents (mg/kg) as follows: Cr (185), Zn (126), Cu (58.8), Pb (31.1), As (15.7), Se (6.85), Cd (5.41), and Hg (0.211). All soil Se contents were above 0.4 mg/kg, indicating Se-rich soils. Se primarily existed in an organic-bound form, accounting for an average proportion of 61.3%, while Cd was mainly exchangeable, with an average of 62.5%. Cd exhibited higher activity according to the Relative Index of Activity (RIA). Nemerow single-factor index analysis confirmed significant soil contamination, with Cd showing the highest level, followed by Cr and Cu, while Pb had the lowest level. Tea exhibited a high Se rich ratio (82.0%) without exceeding the Cd standard. In contrast, corn and rice had relatively lower Se-rich ratios (42.0% and 51.5% respectively) and high rates of Cd exceeding the standard, at 49.0% and 61.0% respectively. Canonical analysis revealed that rice was more influenced by soil factors related to Se and Cd compared to maize and tea crops. Therefore, tea cultivation in the Enshi Permian soil area is recommended for safe crop production. This study provides insights into the enrichment, fractionation, and bioavailability of soil Se, Cd, and other metals in the high-Se and high-Cd areas of permian stratas in Enshi, offering a scientific basis for selecting local food crops and producing safe Se-rich agricultural products in the region.

Selenium spatial distribution and bioavailability of soil-plant systems in China: a comprehensive review

Selenium (Se) has a dual nature, with beneficial and harmful effects on plants, essential for both humans and animals, playing a crucial role in ecosystem regulation. Insufficient Se in specific terrestrial environments raises concerns due to its potential to cause diseases, while excess Se can lead to severe toxicity. Thus, maintaining an optimal Se level is essential for living organisms. This review focuses first on Se transformation, speciation, and geochemical properties in soil, and then provides a concise overview of Se distribution in Chinese soil and crops, with a focus on the relationship between soil Se levels and parent materials. Additionally, this paper explores Se bioavailability, considering parent materials and soil physicochemical properties, using partial least squares path modeling for analysis. This paper aimed to be a valuable resource for effectively managing Se-enriched soil resources, contributing to a better understanding of Se role in ecosystems.

Common metabolism and transcription responses of low-cadmium-accumulative wheat (Triticum aestivum L.) cultivars sprayed with nano-selenium

Cadmium (Cd) contamination in soils threatens food security, while cultivating low-Cd-accumulative varieties, coupled with agro-nanotechnology, offers a potential solution to reduce Cd accumulation in crops. Herein, foliar application of selenium nanoparticles (SeNPs) was performed on seedlings of two low-Cd-accumulative wheat (Triticum aestivum L.) varieties grown in soil spiked with Cd at 3 mg/kg. Results showed that foliar application of SeNPs at 0.16 mg/plant (SeNPs-M) significantly decreased the Cd content in leaves of XN-979 and JM-22 by 46.4 and 40.8 %, and alleviated oxidative damage. The wheat leaves treated with SeNPs-M underwent significant metabolic and transcriptional reprogramming. On one hand, four specialized antioxidant metabolites such as L-Tyrosine, beta-N-acetylglucosamine, D-arabitol, and monolaurin in response to SeNPs in JM-22 and XN-979 is the one reason for the decrease of Cd in wheat leaves. Moreover, alleviation of stress-related kinases, hormones, and transcription factors through oxidative post-translational modification, subsequently regulates the expression of defense genes via Se-enhanced glutathione peroxidase. These findings indicate that combining low-Cd-accumulative cultivars with SeNPs spraying is an effective strategy to reduce Cd content in wheat and promote sustainable agricultural development.

Silicon and selenium alleviate cadmium toxicity in Artemisia selengensis Turcz by regulating the plant-rhizosphere

Soil cadmium (Cd) pollution has emerged as a pressing concern due to its deleterious impacts on both plant physiology and human well-being. Silicon (Si) is renowned for its ability to mitigate excessive Cd accumulation within plant cells and reduce the mobility of Cd in soil, whereas Selenium (Se) augments plant antioxidant capabilities and promotes rhizosphere microbial activity. However, research focusing on the simultaneous utilization of Si and Se to ameliorate plant Cd toxicity through multiple mechanisms within the plant-rhizosphere remains comparatively limited. This study combined hydroponic and pot experiments to investigate the effects of the combined application of Si and Se on Cd absorption and accumulation, as well as the growth and rhizosphere of A. selengensis Turcz under Cd stress. The results revealed that a strong synergistic effect was observed between both Si and Se. The combination of Si and Se significantly increased the activity and content of enzymes and non-enzyme antioxidants within A. selengensis Turcz, reduced Cd accumulation and inhibiting its translocation from roots to shoots. Moreover, Si and Se application improved the levels of reducing sugar, soluble protein, and vitamin C, while reducing nitrite content and Cd bioavailability. Furthermore, the experimental results showed that the combination of Si and Se not only increased the abundance of core rhizosphere microorganisms, but also stimulated the activity of soil enzymes, which effectively limited the migration of Cd in the soil. These findings provided valuable insights into the effective mitigation of soil Cd toxicity to plants and also the potential applications in improving plant quality and safety.

Genome-Wide Identification of OsZIPs in Rice and Gene Expression Analysis under Manganese and Selenium Stress

Zinc (Zn)- and iron (Fe)-regulating transport-like proteins (ZIPs) are a class of proteins crucial for metal uptake and transport in plants, particularly for Zn and Fe absorption and distribution. These proteins ensure the balance of trace elements essential for plant growth, development, and metabolic activities. However, the role of the rice (Oryza sativa) OsZIP gene family in manganese (Mn) and selenium (Se) transport remains underexplored. This research conducted an all-sided analysis of the rice OsZIPs and identified 16 OsZIP sequences. Phylogenetic analysis categorized the OsZIPs predominantly within the three subfamilies. The expression levels of OsZIPs in rice root and leaf subjected to Mn and Se toxicity stress were examined through quantitative real-time PCR (qRT-PCR). The findings revealed significant differential expression of many OsZIPs under these conditions, indicating a potential regulating effect in the response of rice to Mn and Se toxicity. This work lays a foundation for further functional studies of OsZIPs, enhancing our understanding of the response mechanisms of rice to Mn and Se toxicity and their roles in growth, development, and environmental adaptation.

Utilizing transcriptomics and proteomics to unravel key genes and proteins of Oryza sativa seedlings mediated by selenium in response to cadmium stress

BACKGROUND

Cadmium (Cd) pollution has declined crop yields and quality. Selenium (Se) is a beneficial mineral element that protects plants from oxidative damage, thereby improving crop tolerance to heavy metals. The molecular mechanism of Se-induced Cd tolerance in rice (Oryza sativa) is not yet understood. This study aimed to elucidate the beneficial mechanism of Se (1 mg/kg) in alleviating Cd toxicity in rice seedlings.

RESULTS

Exogenous selenium addition significantly improved the toxic effect of cadmium stress on rice seedlings, increasing plant height and fresh weight by 20.53% and 34.48%, respectively, and increasing chlorophyll and carotenoid content by 16.68% and 15.26%, respectively. Moreover, the MDA, ·OH, and protein carbonyl levels induced by cadmium stress were reduced by 47.65%, 67.57%, and 56.43%, respectively. Cell wall metabolism, energy cycling, and enzymatic and non-enzymatic antioxidant systems in rice seedlings were significantly enhanced. Transcriptome analysis showed that the expressions of key functional genes psbQ, psbO, psaG, psaD, atpG, and PetH were significantly up-regulated under low-concentration Se treatment, which enhanced the energy metabolism process of photosystem I and photosystem II in rice seedlings. At the same time, the up-regulation of LHCA, LHCB family, and C4H1, PRX, and atp6 functional genes improved the ability of photon capture and heavy metal ion binding in plants. Combined with proteome analysis, the expression of functional proteins OsGSTF1, OsGSTU11, OsG6PDH4, OsDHAB1, CP29, and CabE was significantly up-regulated under Se, which enhanced photosynthesis and anti-oxidative stress mechanism in rice seedlings. At the same time, it regulates the plant hormone signal transduction pathway. It up-regulates the expression response process of IAA, ABA, and JAZ to activate the synergistic effect between each cell rapidly and jointly maintain the homeostasis balance.

CONCLUSION

Our results revealed the regulation process of Se-mediated critical metabolic pathways, functional genes, and proteins in rice under cadmium stress. They provided insights into the expression rules and dynamic response process of the Se-mediated plant resistance mechanism. This study provided the theoretical basis and technical support for crop safety in cropland ecosystems and cadmium-contaminated areas.

Selenium in plants: A nexus of growth, antioxidants, and phytohormones

Selenium (Se) is an essential micronutrient for both human and animals. Plants serve as the primary source of Se in the food chain. Se concentration and availability in plants is influenced by soil properties and environmental conditions. Optimal Se levels promote plant growth and enhance stress tolerance, while excessive Se concentration can result in toxicity. Se enhances plants ROS scavenging ability by promoting antioxidant compound synthesis. The ability of Se to maintain redox balance depends upon ROS compounds, stress conditions and Se application rate. Furthermore, Se-dependent antioxidant compound synthesis is critically reliant on plant macro and micro nutritional status. As these nutrients are fundamental for different co-factors and amino acid synthesis. Additionally, phytohormones also interact with Se to promote plant growth. Hence, utilization of phytohormones and modified crop nutrition can improve Se-dependent crop growth and plant stress tolerance. This review aims to explore the assimilation of Se into plant proteins, its intricate effect on plant redox status, and the specific interactions between Se and phytohormones. Furthermore, we highlight the proposed physiological and genetic mechanisms underlying Se-mediated phytohormone-dependent plant growth modulation and identified research opportunities that could contribute to sustainable agricultural production in the future.

Selenium and Bacillus proteolyticus SES increased Cu-Cd-Cr uptake by ryegrass: highlighting the significance of key taxa and soil enzyme activity

Many studies have focused their attention on strategies to improve soil phytoremediation efficiency. In this study, a pot experiment was carried out to investigate whether Se and Bacillus proteolyticus SES promote Cu-Cd-Cr uptake by ryegrass. To explore the effect mechanism of Se and Bacillus proteolyticus SES, rhizosphere soil physiochemical properties and rhizosphere soil bacterial properties were determined further. The findings showed that Se and Bacillus proteolyticus SES reduced 23.04% Cu, 36.85% Cd, and 9.85% Cr from the rhizosphere soil of ryegrass. Further analysis revealed that soil pH, organic matter, soil enzyme activities, and soil microbial properties were changed with Se and Bacillus proteolyticus SES application. Notably, rhizosphere key taxa (Bacteroidetes, Actinobacteria, Firmicutes, Patescibacteria, Verrucomicrobia, Chloroflexi, etc.) were significantly enriched in rhizosphere soil of ryegrass, and those taxa abundance were positively correlated with soil heavy metal contents (P < 0.01). Our study also demonstrated that in terms of explaining variations of soil Cu-Cd-Cr content under Se and Bacillus proteolyticus SES treatment, soil enzyme activities (catalase and acid phosphatase) and soil microbe properties showed 42.5% and 12.2% contributions value, respectively. Overall, our study provided solid evidence again that Se and Bacillus proteolyticus SES facilitated phytoextraction of soil Cu-Cd-Cr, and elucidated the effect of soil key microorganism and chemical factor.

Selenium increases antimony uptake in ramie (Boehmeria nivea L.) by enhancing the physiological, antioxidative, and ionomic mechanisms

Ramie (Boehmeria nivea L.) is a promising phytoremediation candidate due to its high tolerance and enrichment capacity for antimony (Sb). However, challenges arise as Sb accumulated mainly in roots, complicating soil extraction. Under severe Sb contamination, the growth of ramie may be inhibited. Strategies are needed to enhance Sb accumulation in ramie's aboveground parts and improve tolerance to Sb stress. Considering the beneficial effects of selenium (Se) on plant growth and enhancing resistance to abiotic stresses, this study aimed to investigate the potential use of Se in enhancing Sb uptake by ramie. We investigated the effects of Se (0.5, 1, 2, 5, or 10 μM) on ramie growth, Sb uptake and speciation, antioxidant responses, and ionomic profiling in ramie under 10 mg/L of SbIII or antimonate (SbV) stresses. Results revealed that the addition of 0.5 μM Se significantly increased shoot biomass by 75.73% under SbIII stress but showed minimal effects on shoot and root length in both SbIII and SbV treatments. Under SbIII stress, 2 μM Se significantly enhanced Sb concentrations by 48.42% in roots and 62.88% in leaves. In the case of SbV exposure, 10 μM Se increased Sb content in roots by 42.57%, and 1 μM Se led to a 91.74% increase in leaves. The speciation analysis suggested that Se promoted the oxidation of SbIII to less toxic SbV to mitigate Sb toxicity. Additionally, Se addition effectively minimized the excess reactive oxygen species produced by Sb exposure, with the lowest malondialdehyde (MDA) content at 0.5 μM Se under SbIII and 2 μM Se under SbV, by activating antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and glutathione peroxidase. Ionomic analysis revealed that Se helped in maintaining the homeostasis of certain nutrient elements, including magnesium, potassium (K), calcium (Ca), iron (Fe), and copper (Cu) in the SbIII-treated roots and K and manganese (Mg) in the SbV-treated roots. The results suggest that low concentrations of Se can be employed to enhance the phytoremediation of Sb-contaminated soils using ramie.

Transcriptome and co-expression network revealed molecular mechanism underlying selenium response of foxtail millet (Setaria italica)

Introduction

Selenium-enriched foxtail millet (Setaria italica) represents a functional cereal with significant health benefits for humans. This study endeavors to examine the impact of foliar application of sodium selenite (Na2SeO4) on foxtail millet, specifically focusing on selenium (Se) accumulation and transportation within various plant tissues.

Methods

To unravel the molecular mechanisms governing selenium accumulation and transportation in foxtail millet, we conducted a comprehensive analysis of selenium content and transcriptome responses in foxtail millet spikelets across different days (3, 5, 7, and 12) under Na2SeO4 treatment (200 μmol/L).

Results

Foxtail millet subjected to selenium fertilizer exhibited significantly elevated selenium levels in each tissue compared to the untreated control. Selenate was observed to be transported and accumulated sequentially in the leaf, stem, and spikes. Transcriptome analysis unveiled a substantial upregulation in the transcription levels of genes associated with selenium metabolism and transport, including sulfate, phosphate, and nitrate transporters, ABC transporters, antioxidants, phytohormone signaling, and transcription factors. These genes demonstrated intricate interactions, both synergistic and antagonistic, forming a complex network that regulated selenate transport mechanisms. Gene co-expression network analysis highlighted three transcription factors in the tan module and three transporters in the turquoise module that significantly correlated with selenium accumulation and transportation. Expression of sulfate transporters (SiSULTR1.2b and SiSULTR3.1a), phosphate transporter (PHT1.3), nitrate transporter 1 (NRT1.1B), glutathione S-transferase genes (GSTs), and ABC transporter (ABCC13) increased with SeO4 2- accumulation. Transcription factors MYB, WRKY, and bHLH were also identified as players in selenium accumulation.

Conclusion

This study provides preliminary insights into the mechanisms of selenium accumulation and transportation in foxtail millet. The findings hold theoretical significance for the cultivation of selenium-enriched foxtail millet.

Selenium-Induced Enhancement in Growth and Rhizosphere Soil Methane Oxidation of Prickly Pear

As an essential element for plants, animals, and humans, selenium (Se) has been shown to participate in microbial methane oxidation. We studied the growth response and rhizosphere methane oxidation of an economic crop (prickly pear, Rosa roxburghii Tratt) through three treatments (Se0.6 mg/kg, Se2.0 mg/kg, and Se10 mg/kg) and a control (Se0 mg/kg) in a two-month pot experiment. The results showed that the height, total biomass, root biomass, and leaf biomass of prickly pear were significantly increased in the Se0.6 and Se2.0 treatments. The root-to-shoot ratio of prickly pear reached a maximum value in the Se2 treatment. The leaf carotenoid contents significantly increased in the three treatments. Antioxidant activities significantly increased in the Se0.6 and Se2 treatments. Low Se contents (0.6, 2 mg/kg) promoted root growth, including dry weight, length, surface area, volume, and root activity. There was a significant linear relationship between root and aboveground Se contents. The Se translocation factor increased as the soil Se content increased, ranging from 0.173 to 0.288. The application of Se can improve the state of rhizosphere soil's organic C and soil nutrients (N, P, and K). Se significantly promoted the methane oxidation rate in rhizosphere soils, and the Se10 treatment showed the highest methane oxidation rate. The soil Se gradients led to differentiation in the growth, rhizosphere soil properties, and methane oxidation capacity of prickly pear. The root Se content and Se translocation factor were significantly positively correlated with the methane oxidation rate. Prickly pear can accumulate Se when grown in Se-enriched soil. The 2 mg/kg Se soil treatment enhanced growth and methane oxidation in the rhizosphere soil of prickly pear.

Biochar and nano biochar: Enhancing salt resilience in plants and soil while mitigating greenhouse gas emissions: A comprehensive review

Salinity stress poses a significant challenge to agriculture, impacting soil health, plant growth and contributing to greenhouse gas (GHG) emissions. In response to these intertwined challenges, the use of biochar and its nanoscale counterpart, nano-biochar, has gained increasing attention. This comprehensive review explores the heterogeneous role of biochar and nano-biochar in enhancing salt resilience in plants and soil while concurrently mitigating GHG emissions. The review discusses the effects of these amendments on soil physicochemical properties, improved water and nutrient uptake, reduced oxidative damage, enhanced growth and the alternation of soil microbial communities, enhance soil fertility and resilience. Furthermore, it examines their impact on plant growth, ion homeostasis, osmotic adjustment and plant stress tolerance, promoting plant development under salinity stress conditions. Emphasis is placed on the potential of biochar and nano-biochar to influence soil microbial activities, leading to altered emissions of GHG emissions, particularly nitrous oxide(N2O) and methane(CH4), contributing to climate change mitigation. The comprehensive synthesis of current research findings in this review provides insights into the multifunctional applications of biochar and nano-biochar, highlighting their potential to address salinity stress in agriculture and their role in sustainable soil and environmental management. Moreover, it identifies areas for further investigation, aiming to enhance our understanding of the intricate interplay between biochar, nano-biochar, soil, plants, and greenhouse gas emissions.

Screening of mustard cultivars for phytoremediation of heavy metals contamination in wastewater irrigated soil systems

The mustard (Brassica juncea L.) plant is a well-known and widely accepted hyper-accumulator of heavy metals. The genetic makeup of mustard's cultivars may significantly impact their phytoremediation capabilities. The present study aimed to investigate the growth performance, yield attributes, and heavy metal accumulation potential of B. juncea cv. Varuna, NRCHB 101, RH 749, Giriraj, and Kranti, cultivated in soil irrigated with wastewater (EPS) and bore-well water (MPS). EPS contributed more Cr, Cd, Cu, Zn, and Ni to tested mustard cultivars than the MPS. EPS reduced morphological, biochemical, physiological, and yield attributes of tested mustard cultivars significantly (p < 0.05) than the MPS. Among the tested cultivars of mustard plants, Varuna had the highest heavy metal load with the lowest harvest index (35.8 and 0.21, respectively). Whereas NRCHB 101 showed the lowest heavy metal load with the highest harvest index (26.9 and 0.43, respectively). The present study suggests that B. juncea cv. Varuna and NRCHB 101 could be used for the phytoextraction of heavy metals and reducing their contamination in food chain, respectively in wastewater irrigated areas of peri-urban India. The outcomes of the present study can also be utilized to develop a management strategy for sustainable agriculture in heavy metal polluted areas resulting from long-term wastewater irrigation.

Transcriptome Analysis Reveals the Mechanism of Exogenous Selenium in Alleviating Cadmium Stress in Purple Flowering Stalks (Brassica campestris var. purpuraria)

In China, cadmium (Cd) stress has a significant role in limiting the development and productivity of purple flowering stalks (Brassica campestris var. purpuraria). Exogenous selenium supplementation has been demonstrated in earlier research to mitigate the effects of Cd stress in a range of plant species; nevertheless, the physiological and molecular processes by which exogenous selenium increases vegetable shoots' resistance to Cd stress remain unclear. Purple flowering stalks (Brassica campestris var. purpuraria) were chosen as the study subject to examine the effects of treatment with sodium selenite (Na2SeO3) on the physiology and transcriptome alterations of cadmium stress. Purple flowering stalk leaves treated with exogenous selenium had higher glutathione content, photosynthetic capacity, and antioxidant enzyme activities compared to the leaves treated with Cd stress alone. Conversely, the contents of proline, soluble proteins, soluble sugars, malondialdehyde, and intercellular CO2 concentration tended to decrease. Transcriptome analysis revealed that 2643 differentially expressed genes (DEGs) were implicated in the response of exogenous selenium treatment to Cd stress. The metabolic pathways associated with flavonoid production, carotenoid synthesis, glutathione metabolism, and glucosinolate biosynthesis were among those enriched in these differentially expressed genes. Furthermore, we discovered DEGs connected to the production route of glucosinolates. This work sheds fresh light on how purple flowering stalks' tolerance to cadmium stress is improved by exogenous selenium.

Selenium - An environmentally friendly micronutrient in agroecosystem in the modern era: An overview of 50-year findings

Agricultural productivity is constantly being forced to maintain yield stability to feed the enormously growing world population. However, shrinking arable and nutrient-deprived soil and abiotic and biotic stressor (s) in different magnitudes put additional challenges to achieving global food security. Though well-defined, the concept of macro, micronutrients, and beneficial elements is from a plant nutritional perspective. Among various micronutrients, selenium (Se) is essential in small amounts for the life cycle of organisms, including crops. Selenium has the potential to improve soil health, leading to the improvement of productivity and crop quality. However, Se possesses an immense encouraging phenomenon when supplied within the threshold limit, also having wide variations. The supplementation of Se has exhibited promising outcomes in lessening biotic and abiotic stress in various crops. Besides, bulk form, nano-Se, and biogenic-Se also revealed some merits and limitations. Literature suggests that the possibilities of biogenic-Se in stress alleviation and fortifying foods are encouraging. In this article, apart from adopting a combination of a conventional extensive review of the literature and bibliometric analysis, the authors have assessed the journey of Se in the "soil to spoon" perspective in a diverse agroecosystem to highlight the research gap area. There is no doubt that the time has come to seriously consider the tag of beneficial elements associated with Se, especially in the drastic global climate change era.

Abiotic stress-induced secondary metabolite production in Brassica: opportunities and challenges

Over the decades, extensive research efforts have been undertaken to understand how secondary plant metabolites are affected by genetic, environmental, and agronomic factors. Understanding the genetic basis of stress-response metabolite biosynthesis is crucial for sustainable agriculture production amidst frequent occurrence of climatic anomalies. Although it is known that environmental factors influence phytochemical profiles and their content, studies of plant compounds in relation to stress mitigation are only emerging and largely hindered by phytochemical diversities and technical shortcomings in measurement techniques. Despite these challenges, considerable success has been achieved in profiling of secondary metabolites such as glucosinolates, flavonoids, carotenoids, phenolic acids and alkaloids. In this study, we aimed to understand the roles of glucosinolates, flavonoids, carotenoids, phenolic acids and alkaloids in relation to their abiotic stress response, with a focus on the developing of stress-resilient crops. The focal genus is the Brassica since it (i) possesses variety of specialized phytochemicals that are important for its plant defense against major abiotic stresses, and (ii) hosts many economically important crops that are sensitive to adverse growth conditions. We summarize that augmented levels of specialized metabolites in Brassica primarily function as stress mitigators against oxidative stress, which is a secondary stressor in many abiotic stresses. Furthermore, it is clear that functional characterization of stress-response metabolites or their genetic pathways describing biosynthesis is essential for developing stress-resilient Brassica crops.

Selenite reduced cadmium uptake, interfered signal transduction of endogenous phytohormones, and stimulated secretion of tartaric acid based on a combined analysis of non-invasive micro-test technique, transcriptome and metabolome

Selenium (Se) can reduce uptake and translocation of cadmium (Cd) in plants via plenty of ways, including regulation of root morphology. However, the underlying mechanisms on how Se will regulate root morphology under metal(loid) stresses are not fully illustrated. To fill up this knowledge gap, we investigated the effects of 0.5 mg L-1 selenite (Se(IV)) on root exudates, root morphology, root endogenous hormones, and Cd uptake efficiency of rice under the 1 mg L-1 Cd stress condition. The results showed that Se(IV) significantly reduced shoot and root Cd concentrations, and decreased Cd uptake efficiency via root hairs determined by a non-invasive micro-test (NMT) technology. When compared to the 1 mg L-1 Cd (Cd1) treatment, addition of 0.5 mg L-1 Se(IV) (1) significantly reduced root surface area and tip numbers, and non-significantly reduced root length, but significantly enhanced root diameter and root volume; (2) significantly enhanced concentrations of tartaric acid in the root exudate solution, root auxin (IAA) and root jasmonic acid (JA) via a UHPLC or a HPLC analysis; (3) significantly up-regulated metabolites correlated with synthesis of IAA, JA, gibberellin (GA), and salicylic acid, such as GA53, M-SA, (+/-)7-epi-JA, and derivatives of tryptophan and indole in the metabolome analysis. However, results of transcriptome analysis showed that (1) no upregulated differentially expressed genes (DEGs) were enriched in IAA synthesis; (2) some upregulated DEGs were found to be enriched in JA and GA53 synthesis pathways. In summary, although Se(IV) stimulated the synthesis of IAA, JA, and GA53, it significantly inhibited root growth mainly by 1) affecting signal transduction of IAA and GA; 2) altering IAA polar transport and homeostasis; and 3) regulating DEGs including SAUR32, SAUR36, SAUR76, OsSub33, OsEXPA8, OsEXPA18, and Os6bglu24.

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.

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.

Nanoparticles modulate heavy-metal and arsenic stress in food crops: Hormesis for food security/safety and public health

Heavy metal and arsenic (HM-As) contamination at the soil-food crop interface is a threat to food security/safety and public health worldwide. The potential ecotoxicological effects of HM-As on food crops can perturb normal physiological, biochemical, and molecular processes. To protect food safety and human health, nanoparticles (NPs) can be applied to seed priming and soil amendment, as 'manifestation of hormesis' to modulate HM-As-induced oxidative stress in edible crops. This review provides a comprehensive overview of NPs-mediated alleviation of HM-As stress in food crops and resulting hormetic effects. The underlying biochemical and molecular mechanisms in the amelioration of HM-As-induced oxidative stress is delineated by covering the various aspects of the interaction of NPs (e.g., magnetic particles, silicon, metal oxides, selenium, and carbon nanotubes) with plant microbes, phytohormone, signaling molecules, and plant-growth bioregulators (e.g., salicylic acid and melatonin). With biotechnical advances (such as clustered regularly interspaced short palindromic repeats (CRISPR) gene editing and omics), the efficacy of NPs and associated hormesis has been augmented to produce "pollution-safe designer cultivars" in HM-As-stressed agriculture systems. Future research into nanoscale technological innovations should thus be directed toward achieving food security, sustainable development goals, and human well-being, with the aid of HM-As stress resilient food crops.

Mechanism of selenite tolerance during barley germination: A combination of tissue selenium metabolism alterations and ascorbate-glutathione cycle modulation

Selenite is widely used to increase Selenium (Se) content in cereals, however excessive selenite may be toxic to plant growth. In this study, barley was malted to elucidate the action mechanism of selenite in the generation and detoxification of oxidative toxicity. The results showed that high doses (600 μM) of selenite radically increased oxidative stress by the elevated accumulation of superoxide and malondialdehyde, leading to phenotypic symptoms of selenite-induced toxicity like stunted growth. Barley tolerates selenite through a combination of mechanisms, including altering Se distribution in barley, accelerating Se efflux, and increasing the activity of some essential antioxidant enzymes. Low doses (150 μM) of selenite improved barley biomass, respiratory rate, root vigor, and maintained the steady-state equilibrium between reactive oxygen species (ROS) and antioxidant enzyme. Selenite-induced proline may act as a biosignal to mediate the response of barley to Se stress. Furthermore, low doses of selenite increased the glutathione (GSH) and ascorbate (AsA) concentrations by mediating the ascorbate-glutathione cycle (AsA-GSH cycle). GSH intervention and dimethyl selenide volatilization appear to be the primary mechanisms of selenite tolerance in barley. Thus, results from this study will provide a better understanding of the mechanisms of selenite tolerance in crops.

Comprehensive understanding of the regulatory mechanism by which selenium nanoparticles boost CO2 fixation and cadmium tolerance in lipid-producing green algae under recycled medium

Recycled medium plus cadmium is a promising technique for reducing the cultivation cost and enhancing the yield of microalgae lipids. However, oxidative stress and cadmium toxicity significantly hinder the resulting photosynthetic efficiency, cell growth and cell activity. Herein, selenium nanoparticles (SeNPs) were used to increase the total biomass, biolipid productivity, and tolerance to cadmium. Wide-ranging analyses of photosynthesis, energy yield, fatty acid profiles, cellular ultrastructure, and oxidative stress biomarkers were conducted to examine the function of SeNPs in CO2 fixation and cadmium resistance in Ankistrodesmus sp. EHY. The application of 15 μM cadmium and 2 mg L-1 SeNPs further enhanced the algal biomass productivity and lipid productivity to 500.64 mg L-1 d-1 and 301.14 mg L-1 d-1, respectively. Moreover, the rates of CO2 fixation, chlorophyll synthesis and total nitrogen removal were similarly increased by the application of SeNPs. Exogenous SeNPs strengthened cell growth and cadmium tolerance by upregulating photosynthesis, the TCA cycle and the antioxidant system, reducing the uptake and translocation of cadmium, and decreasing the levels of reactive oxidative stress (ROS), extracellular polymeric substances (EPSs) and cellular Cd2+ level in EHY under recycled medium and cadmium stress conditions. Additionally, a maximum energy yield of 127.40 KJ L-1 and a lipid content of 60.15% were achieved in the presence of both SeNPs and cadmium stress. This study may inspire the efficient disposal of recycled medium and biolipid production while also filling the knowledge gaps regarding the mechanisms of SeNP functions in carbon fixation and cadmium tolerance in microalgae.

Biofortification revisited: Addressing the role of beneficial soil microbes for enhancing trace elements concentration in staple crops

Trace element deficiency is a pervasive issue contributing to malnutrition on a global scale. The primary cause of this hidden hunger is related to low dietary intake of essential trace elements, which is highly prevalent in numerous regions across the world. To address deficiency diseases in humans, fortification of staple crops with vital trace elements has emerged as a viable solution. Current methods for fortifying crops encompass chemical amendments, genetic breeding, and transgenic approaches, yet these approaches possess certain limitations, constraining their agricultural application. In contrast, fortifying staple crops through the utilization of soil-beneficial microbes has emerged as a promising and economically feasible approach to enhance trace element content in crops. A specific subset of these beneficial soil microbes, referred to as plant growth-promoting microbes, have demonstrated their ability to influence the interactions between plants, soil, and minerals. These microbes facilitate the transport of essential soil minerals, such as zinc, iron, and selenium, into plants, offering the potential for the development of tailored bioinoculants that can enhance the nutritional quality of cereals, pulses, and vegetable crops. Nevertheless, further research efforts are necessary to comprehensively understand the molecular mechanisms underlying the uptake, transport, and augmentation of trace element concentrations in staple crops. By delving deeper into these mechanisms, customized bioinoculants of soil-beneficial microbes can be developed to serve as highly effective strategies in combating trace element deficiency and promoting global nutritional well-being.

Exploring the Effects of Selenium and Brassinosteroids on Photosynthesis and Protein Expression Patterns in Tomato Plants under Low Temperatures

This study aimed to assess the effects of low-temperature stress on two tomato cultivars (S-22 and PKM-1) treated with 24-epibrassinolide (EBL) and selenium (Se) by determining the changes in the proteomics profiles, growth biomarkers, biochemical parameters, and physiological functions. The growth parameters, photosynthetic traits, and activity of nitrate reductase in the S-22 and PKM-1 plants were markedly reduced by exposure to low temperatures. However, the combined application of EBL and Se under different modes significantly enhanced the aforementioned parameters under stress and non-stress conditions. Exposure to low temperatures increased the activities of the antioxidant enzymes (catalase, peroxidase, and superoxide dismutase) and the proline content of leaves, which were further enhanced by treatment with Se and EBL in both varieties. This research sheds light on the potential for employing exogenous EBL and Se as crucial biochemical tactics to assist tomato plants in surviving low-temperature stress. Moreover, the differentially expressed proteins that were involved in plant metabolism following the combined application of EBL and Se under low-temperature stress were additionally identified. Functional analysis revealed that the Q54YH4 protein plays an active role against plant stressors. The conserved regions in the protein sequences were analyzed for assessing the reliability of plant responses against the external application of EBL and Se under low temperatures.

Effect of Dietary Selenium on the Growth and Immune Systems of Fish

Dietary selenium (Se) is an essential component that supports fish growth and the immune system. This review attempts to provide insight into the biological impacts of dietary Se, including immunological responses, infection defense, and fish species growth, and it also identifies the routes via which it enters the aquatic environment. Dietary Se is important in fish feed due to its additive, antioxidant, and enzyme properties, which aid in various biological processes. However, excessive intake of it may harm aquatic ecosystems and potentially disrupt the food chain. This review explores the diverse natures of dietary Se, their impact on fish species, and the biological methods for eliminating excesses in aquatic environments. Soil has a potential role in the distribution of Se through erosion from agricultural, industrial, and mine sites. The research on dietary Se's effects on fish immune system and growth can provide knowledge regarding fish health, fish farming strategies, and the health of aquatic ecosystems, promoting the feed industry and sustainable aquaculture. This review provides data and references from various research studies on managing Se levels in aquatic ecosystems, promoting fish conservation, and utilizing Se in farmed fish diets.

Se Ameliorates Cd Toxicity in Oilseed rape (Brassica napus L.) Seedlings by Inhibiting Cd Transporter Genes and Maintaining root Plasma Membrane Integrity

Se (Selenium) has been reported to be an important protective agent to decreases Cd (Cadmium) induced toxic in plants. However, it remains unclear how Se mitigates the uptake of Cd and increased the resistance to Cd toxicity. Hydroponic experiments were arranged to investigate the changes of physiological properties, root cell membrane integrity and Cd-related transporter genes in rape seedlings. Comparison of the biomass between the addition of Se and the absence of Se under Cd exposure showed that the Cd-induced growth inhibition of rape seedlings was alleviated by Se. Cd decreased the photosynthetic rate (Pn), stomatal conductance (Gs) and photosynthetic pigment content including chlorophyll a, chlorophyll b and carotenoid. However, all these parameters were all significantly improved by Se addition. Moreover, exposure to Se resulted in a decrease in Cd concentration in both shoot and root, ranging from 4.28 to 27.2%. Notably, the application of Se at a concentration of 1 µmol L- 1 exhibited the best performance. Furthermore, Se enhanced cell membrane integrity and reduced superoxide anion levels, thereby contributing to the alleviation of cadmium toxicity in plants. More critically, Se decreased the expression levels of root Cd-related transporter genes BnIRT1, BnHMA2 and BnHMA4 under Cd stress, which are responsible for Cd transport and translocation. These results are important to increase crop growth and reduce Cd load in the food chain from metal toxicity management and agronomical point of view.

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.

Spectroscopic Analyses Highlight Plant Biostimulant Effects of Baker's Yeast Vinasse and Selenium on Cabbage through Foliar Fertilization

The main aim of this study is to find relevant analytic fingerprints for plants' structural characterization using spectroscopic techniques and thermogravimetric analyses (TGAs) as alternative methods, particularized on cabbage treated with selenium-baker's yeast vinasse formulation (Se-VF) included in a foliar fertilizer formula. The hypothesis investigated is that Se-VF will induce significant structural changes compared with the control, analytically confirming the biofortification of selenium-enriched cabbage as a nutritive vegetable, and particularly the plant biostimulant effects of the applied Se-VF formulation on cabbage grown in the field. The TGA evidenced a structural transformation of the molecular building blocks in the treated cabbage leaves. The ash residues increased after treatment, suggesting increased mineral accumulation in leaves. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) evidenced a pectin-Iα-cellulose structure of cabbage that correlated with each other in terms of leaf crystallinity. FTIR analysis suggested the accumulation of unesterified pectin and possibly (seleno) glucosinolates and an increased network of hydrogen bonds. The treatment with Se-VF formulation induced a significant increase in the soluble fibers of the inner leaves, accompanied by a decrease in the insoluble fibers. The ratio of soluble/insoluble fibers correlated with the crystallinity determined by XRD and with the FTIR data. The employed analytic techniques can find practical applications as fast methods in studies of the effects of new agrotechnical practices, while in our particular case study, they revealed effects specific to plant biostimulants of the Se-VF formulation treatment: enhanced mineral utilization and improved quality traits.

Selenite affected photosynthesis of Oryza sativa L. exposed to antimonite: Electron transfer, carbon fixation, pigment synthesis via a combined analysis of physiology and transcriptome

Selenium (Se) is a microelement that can counteract (a)biotic stresses in plants. Excess antimony (Sb) will inhibit plant photosynthesis, which can be alleviated by appropriate doses of Se but the associated mechanisms at the molecular levels have not been fully explored. Here, a rice variety (Yongyou 9) was exposed to selenite [Se(IV), 0.2 and 0.8 mg L-1] alone or combined with antimonite [Sb(III), 5 and 10 mg L-1]. When compared to the 10 mg L-1 Sb treatment alone, addition of Se in a dose-dependent manner 1) reduced the heat dissipation efficiency resulting from the inhibited donors, Sb concentrations in shoots and roots, leaf concentrations of fructose, H2O2 and O2•-; 2) enhanced heat dissipation efficiency resulting from the inhibited accepters value, concentrations of Chl a, sucrose and starch, and the enzyme activity of adenosine diphosphate glucose pyrophosphorylase, sucrose phosphate synthase, and sucrose synthase; but 3) did not alter gas exchange parameters, concentrations of Chl b and total Chl, enzyme activity of soluble acid invertase, and values of maximum P700 signal, photochemical efficiency of PSI and electron transport rate of PSI. Se alleviated the damage caused by Sb to the oxygen-evolving complex and promoted the transfer of electrons from QA to QB. When compared to the 10 mg L-1 Sb treatment alone, addition of Se 1) up-regulated genes correlated to synthesis pathways of Chl, carotenoid, sucrose and glucose; 2) disturbed signal transduction pathway of abscisic acid; and 3) upregulated gene expression correlated to photosynthetic complexes (OsFd1, OsFER1 and OsFER2).