Si Application Research Articles

Remediation of Cadmium Stress in Strawberry Plants Using Humic Acid and Silicon Applications.

(1) Background: Strawberry plants are strongly affected by heavy-metal-contaminated soils, which affects plant growth, yield and fruit quality. The aim of this work was to study the effects of a combination and individual application of silicon (Si) and humic acid (HA) on growth and development of Rubygem strawberries exposed to cadmium (Cd) in greenhouse conditions. (2) Methods: Morphological, physiological and biochemical parameters, including minerals in roots and leaves were determined. (3) Results: Cd stress in strawberry plants decreased plant fresh and dry weight; leaf stomatal conductance; leaf relative water content and chlorophyll content; number of leaves; leaf area; leaf N, P and K levels; and root P, N, Mg, K and Ca contents. Cd increased membrane permeability, leaf temperature, proline levels and lipid peroxidation. Si and HA individual applications to strawberries mitigated the negative effect of Cd stress on biochemical, physiological, morphological and minerals parameters by decreasing membrane permeability, leaf temperature, proline levels and lipid peroxidation. (4) Conclusions: Our findings highlighted that applications of Si, HA and Si + HA were effective in conferring Cd tolerance in strawberry plants by upregulating their many morphological, physiological and biochemical properties and reducing Cd stress.

Silicon Mediated Plant Immunity against Nematodes: Summarizing the Underline Defence Mechanisms in Plant Nematodes Interaction.

Silicon (Si) is known to stimulate plant resistance against different phytopathogens, i.e., bacteria, fungi, and nematodes. It is an efficient plant growth regulator under various biotic and abiotic stresses. Silicon-containing compounds, including silicon dioxide, SiO2 nanoparticles (NPs), nano-chelated silicon fertilizer (NCSF), sodium siliconate, and sodium metasilicate, are effective in damaging various nematodes that reduce their reproduction, galling, and disease severity. The defence mechanisms in plant-nematodes interaction may involve a physical barrier, plant defence-associated enzyme activity, synthesis of antimicrobial compounds, and transcriptional regulation of defence-related genes. In the current review, we focused on silicon and its compounds in controlling plant nematodes and regulating different defence mechanisms involved in plant-nematodes interaction. Furthermore, the review aims to evaluate the potential role of Si application in improving plant resistance against nematodes and highlight its need for efficient plant-nematodes disease management.

Foliar Application of Silicon in Vitis vinifera: Targeted Metabolomics Analysis as a Tool to Investigate the Chemical Variations in Berries of Four Grapevine Cultivars.

Silicon (Si) is a beneficial element for the growth of various crops, but its effect on plant metabolism is still not completely elucidated. Even if Si is not classified as an essential element for plants, the literature has reported its beneficial effects in a variety of species. In this work, the influence of Si foliar application on berry composition was evaluated on four grapevine cultivars. The berries of Teroldego and Oseleta (red grapes) and Garganega and Chardonnay (white grapes) were analyzed after foliar application of silicon by comparing the treated and control groups. A targeted metabolomic approach was used that focused on secondary metabolites, amino acids, sugars, and tartaric acid. Measurements were performed using liquid chromatography coupled with a diode array detector and mass spectrometry (LC-DAD-MSn), a LC-evaporative light scattering detector (ELDS), and LC-MS/MS methods specific for the analysis of each class of constituents. After the data collection, multivariate models, PCA, PLS-DA, OPLS-DA, were elaborated to evaluate the effect of Si application in the treated vs. control samples. Results were different for each grape cultivar. A significant increase in anthocyanins was observed in the Oseleta cultivar, with 0.48 mg g-1 FW in the untreated samples vs. 1.25 mg g-1 FW in the Si-treated samples. In Garganega, Si treatment was correlated with increased proline levels. In Chardonnay, the Si application was related to decreased tartaric acid. The results of this work show for the first time that Si induces cultivar specific changes in the berry composition in plants cultivated without an evident abiotic or biotic stress.

Application of Exogenous Silicon for Alleviating Photosynthetic Inhibition in Tomato Seedlings under Low-Calcium Stress.

To address the low Ca-induced growth inhibition of tomato plants, the mitigation effect of exogenous Si on tomato seedlings under low-Ca stress was investigated using different application methods. We specifically analyzed the effects of root application or foliar spraying of 1 mM Si on growth conditions, leaf photosynthetic properties, stomatal status, chlorophyll content, chlorophyll fluorescence, ATP activity and content, Calvin cycle-related enzymatic activity, and gene expression in tomato seedlings under low vs. adequate calcium conditions. We found that the low-Ca environment significantly affected (reduced) these parameters, resulting in growth limitation. Surprisingly, the application of 1 mM Si significantly increased plant height, stem diameter, and biomass accumulation, protected photosynthetic pigments, improved gas exchange, promoted ATP production, enhanced the activity of Calvin cycle key enzymes and expression of related genes, and ensured efficient photosynthesis to occur in plants under low-Ca conditions. Interestingly, when the same amount of Si was applied, the beneficial effects of Si were more pronounced under low-Ca conditions that under adequate Ca. We speculate that Si might promote the absorption and transport of calcium in plants. The effects of Si also differed depending on the application method; foliar spraying was better in alleviating photosynthetic inhibition in plants under low-Ca stress, whereas root application of Si significantly promoted root growth and development. Enhancing the photosynthetic capacity by foliar Si application is an effective strategy for ameliorating the growth inhibition of plants under low-Ca stress.

Synergistic Effects of Silicon and Preservative on Promoting Postharvest Performance of Cut Flowers of Peony (Paeonia lactiflora Pall.).

As a commercial high-grade cut flower, the marketability of herbaceous peony (Paeonia lactiflora Pall.) is limited by its short vase life in water. Si (silicon) is an alternative to improve the postharvest life of cut flowers. However, the effects of the combined application of Si and preservatives on the postharvest performance of cut peony flowers are unknown. In this study, the effects of a Si application and a preservative alone and collegial on the longevity of the vase life, water loss, antioxidant defense system, and stock carbohydrates level of cut flowers of three peony cultivars were investigated. It was observed that Si effectively prolonged the vase life, while the preservative alone, to a lesser extent, but markedly induced an early flowering and a greater flower diameter (flower open degree). The simultaneous use of Si and the preservatives not only showed larger flowers, but also improved the postharvest performance as characterized by an extended vase life and delayed the water loss. In addition, the Si supplementation dramatically intensified the antioxidant defense system (ameliorated antioxidant enzymes and alleviated ROS accumulation) in petals but did not increase the stock carbohydrates (starch and soluble sugars) levels, as compared to the treatment with the preservative alone. We show that a Si supplementation to a preservative is highly recommended for a large-scale use to promote the postharvest performance and competitiveness of marketed cut flowers.

The influence of silica upon quantitative, qualitative, and biochemical traits of tomato under water stress

Water stress is by far the most serious limiting factor to tomato (Solanum lycopersicom) production, particularly in Iran where located in arid and semi-arid regions. Silicon (Si) is considered an effective element to mitigate the adverse effects of water stress by promoting plant growth and production. Therefore, the present study was designed to evaluate the effects of the foliar application of Si (0, 100, and 200 mg L–1) and three water regimes – no stress (100), mild stress (80%), and severe stress (60%) – on the growth parameters, the yield, and the fruit quality as well as antioxidant status of the tomato. The imposed water stress significantly increased the total soluble solids (TSS), the total acidity (TA), and the flavonoids as well as antioxidant defense parameters such as catalase (CAT) and peroxidase (POX), while the growth parameters (plant height and leaf number) and tomato yield were decreased. In contrast, the foliar application of Si (200 mg L–1) remarkably improved the total yield of tomatoes when exposed to water stress by improving the antioxidant enzyme activities and total flavonoid compounds. In addition, the application of Si could significantly improve the growth parameters (plant height and leaf number) and fruit quality (fruit firmness and size). As a result, the foliar application of Si could be suggested as an effective strategy for imparting water stress resistance in the tomato.

Application of silicon and biochar alleviates the adversities of arsenic stress in maize by triggering the morpho-physiological and antioxidant defense mechanisms

Arsenic (As) contamination in the soil adversely affects crop productivity, grain quality, and human health. A pot experiment was performed to assess the sole and combined effects of Si and biochar on growth, physiological and antioxidant defense mechanisms, yield, and grain quality of maize. Soil treatments comprised of control (no treatment), As, Si, biochar, Si + biochar, As + Si, As + biochar, and As + Si + biochar placed in a completely randomized design with three replications. As toxicity significantly reduced chlorophyll a (5.18%), chlorophyll b (33.87%), chlorophyll a + b (11.67%), and primary metabolites [soluble protein (54.93%), amino acids (24.85%), total soluble sugars (39.77%), and phenolic contents (25.88%)], while increasing the activities of enzymatic antioxidants such as superoxide dismutase (SOD) by 43.51%, peroxidase (POD) by 47.93%, catalase (CAT) by 47.98%, and ascorbate peroxidase (APX) by 59.02%, as well as that of lipid peroxidation in the leaves of maize. In addition, As contamination reduced the grain yield and yield-related attributes relative to the respective controls. Among the soil applications, the interactive effect of Si and biochar improved maize grain yield (12.12%) by triggering activities of enzymatic antioxidants and proline contents and reducing the H2O2 and MDA contents. The combined application of Si and biochar enhanced the Si contents in shoots of the control and As-contaminated plants, while significantly reducing As concentration in shoots (69%) and grains (142%). In conclusion, the combined application of Si and biochar was found to be a fruitful soil amendment strategy to improve the yield of maize and reduce the toxic limit of As under As-contaminated soil. The results of this study may be useful for the cultivation of food crops under AS-contaminated soils, but before commercial recommendation, more trails are required under field conditions.

Effects of the Foliar Application of Water-soluble Chitosan or Na2SiO3 Fertilizer on the Pb Accumulation by a Low-Pb Accumulator Brassica napus Grown on Farmland Surrounding a Working Smelter.

Field experiments were conducted to investigate the effects of two foliar fertilizers, water-soluble chitosan (WSC) and Na2SiO3 (Si), on the accumulation of Pb by a low-Pb accumulator Brassica napus cultivar (QY-1) grown at two mildly Pb-contaminated farmland sites surrounding working smelters in Jiyuan city, Henan province, China. Regardless of the frequency of the fertilizer treatments, the foliar application of WSC (0.01%) or Si (0.15%) significantly increased the QY-1 biomass and decreased the grain Pb concentrations. Compared with the control treatment, spraying plants once with WSC or Si during the flowering period achieved the best effect in the two soils with different pollution, which may be because inhibiting the accumulation of Pb in grains by decreasing the husk-to-grain transfer coefficient. Thus, the foliar application of WSC or Si combined with the cultivation of a low-Pb accumulator is a promising approach for optimizing the utility of Pb-contaminated farmland affected by atmospheric deposition.

Silicon actively mitigates the negative impacts of soil cadmium contamination on garlic growth, yield, quality and edible safety

Potential health risks of cadmium (Cd) in agroecosystems migrating to the human body along the food chain have become a worldwide hotspot issue, but information on phytotoxicity mitigation and product quality and safety assessment of Cd-stressed garlic is still lacking. Thus, based on the response performance of garlic yield and quality to soil pH and Cd level, this study systematically revealed the effects of silicon (Si) on the growth, yield, quality, photosynthesis, fluorescence, antioxidant system, tissue Cd residues and edible safety of Cd-stressed garlic. The results showed that garlic yield and quality decreased with increasing soil Cd levels, while the lower soil pH exacerbated Cd contamination. When exposed to 1.2 mg kg−1 Cd, the bulb yield at pH 5.50 was 5.51% lower than that at pH 6.89, while the Cd residues in the bulb were 8.77% higher. Notably, 0.67∼2.0 g kg−1 Si application enhanced bulb yield (by 12.09%∼39.32%) and quality (e.g., allicin, by 6.67%∼40.00%) and simultaneously reduced Cd absorption, translocation and accumulation (e.g., bioconcentration coefficient, by 13.01%∼86.17%). Si mitigated Cd-induced phytotoxicity mainly by improving root activity, antioxidant enzyme activity, photosynthesis and fluorescence. Si increased the soil pH, which contributed to Cd fixation. These results provide significant theoretical guidance for garlic safety production and heavy metal risk prevention in agroecosystems.

Silicon Palliates Chromium Toxicity through the Formation of Root Hairs in Rice (Oryza sativa) Mediated by GSH and IAA.

Along with the rapidly increasing environmental contamination by heavy metals, the exposure of plants to chromium has also magnified, resulting in a declined productivity. Hexavalent chromium [Cr(VI)], the most toxic form of Cr, brings about changes in plant processes at morpho-physiological and biochemical levels. However, silicon (Si) is known to mitigate the impact of abiotic stresses in plants. Here, we demonstrate Si-mediated alleviation of Cr(VI) toxicity and its effects on root hair formation in rice seedlings. Reduced glutathione (GSH) and indole-3 acetic acid (IAA, an important auxin) were assessed for their involvement in root hair formation after the application of Si to Cr(VI)-stressed plants, and our results confirmed their crucial significance in such developmental processes. The expression analysis of genes involved in GSH biosynthesis (OsGS2) and regeneration (OsGR1), and auxin biosynthesis (OsTAA1 and OsYUCCA1) and transport (OsAUX1 and OsPIN1) corroborated their positive role in Si-mediated root hair formation in Cr(VI)-stressed rice seedlings. Moreover, the results indicated that nitric oxide (NO) seems a probable but not fundamental component in Si-mediated formation of roots in rice during exposure to Cr(VI) stress. In this study, the indispensable role of GSH and IAA, redox homeostasis of GSH and IAA biosynthesis and transport are discussed with regard to Si-mediated formation of root hairs in rice under Cr(VI) stress. The results of the study suggest that Si is a protective agent against Cr(VI) stress in rice, and the findings can be used to develop Cr(VI) stress-tolerant varieties of rice with enhanced productivity.

Silicon enhances plant resistance to Fusarium wilt by promoting antioxidant potential and photosynthetic capacity in cucumber (Cucumis sativus L.).

Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum (Fo), is a severe soil-borne disease affecting cucumber production worldwide, particularly under monocropping in greenhouses. Silicon (Si) plays an important role in improving the resistance of crops to Fusarium wilt, but the underlying mechanism is largely unclear. Here, an in vitro study showed that 3 mmol·l-1 Si had the best inhibitory effect on the mycelial growth of F. oxysporum in potato dextrose agar (PDA) culture for 7 days. Subsequently, the occurrence of cucumber wilt disease and its mechanisms were investigated upon treatments with exogenous silicon under soil culture. The plant height, stem diameter, root length, and root activity under Si+Fo treatment increased significantly by 39.53%, 94.87%, 74.32%, and 95.11% compared with Fo only. Importantly, the control efficiency of Si+Fo was 69.31% compared with that of Fo treatment. Compared with Fo, the activities of peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) significantly increased by 148.92%, 26.47%, and 58.54%, while the contents of H2O2, , and malondialdehyde (MDA) notably decreased by 21.67%, 59.67%, and 38.701%, respectively, in roots of cucumber plants treated with Si + Fo. Compared with Fo treatment, the net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum RuBisCO carboxylation rates (Vcmax), maximum RuBP regeneration rates (Jmax), and activities of ribulose-1,5-bisphosphate carboxylase (RuBisCO), fructose-1,6-bisphosphatase (FBPase), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the expression of FBPA, TPI, SBPase, and FBPase in Si+Fo treatment increased significantly. Furthermore, Si alleviated stomatal closure and enhanced endogenous silicon content compared with only Fo inoculation. The study results suggest that exogenous silicon application improves cucumber resistance to Fusarium wilt by stimulating the antioxidant system, photosynthetic capacity, and stomatal movement in cucumber leaves. This study brings new insights into the potential of Si application in boosting cucumber resistance against Fusarium wilt with a bright prospect for Si use in cucumber production under greenhouse conditions.

Silicon fertilizer mediated structural variation and niche differentiation in the rhizosphere and endosphere bacterial microbiome and metabolites of sugarcane.

The microbiomes of plant are potential determinants of plant growth, productivity, and health. They provide plants with a plethora of functional capacities, namely, phytopathogens suppression, access to low-abundance nutrients, and resistance to environmental stressors. However, a comprehensive insight into the structural compositions of the bacterial abundance, diversity, richness, and function colonizing various microenvironments of plants, and specifically their association with bioactive compounds and soil edaphic factors under silicon (Si) amendment remains largely inconclusive. Here, high-throughput sequencing technology and nontargeted metabolite profiling method were adopted to test the hypotheses regarding microbiome niche abundance, diversity, richness, function, and their association with bioactive compounds and soil edaphic factors within different ecological niches (leaf, stem, root, rhizosphere, and bulk soils) under Si amendment during cane growth were we addressed. Our results demonstrated that Si correspondingly increased sugarcane theoretical production and yield, and remarkably enhanced soil nutrient status, especially Si, AP, and AK. It was also observed that bacterial diversity demonstrated tissue-dependent distribution patterns, with the bulk soil, rhizosphere soil, and root endosphere revealing the highest amount of bacterial diversity compared with the stem and leaf tissues. Moreover, Si exhibited the advantage of considerably promoting bacterial abundance in the various plant compartments. Co-occurrence interactions demonstrated that Si application has the potential to increase bacterial diversity maintenance, coexistence, and plant–soil systems bacteria connections, thereby increasing the functional diversity in the various plant tissues, which, in turn, could trigger positive growth effects in plants. Network analysis further revealed that metabolite profiles exhibited a strong association with bacterial community structures. It was also revealed that Si content had a considerable positive association with bacterial structures. Our findings suggest that the dynamic changes in microbe’s community composition in different plant and soil compartments were compartment-specific. Our study provides comprehensive empirical evidence of the significance of Si in agriculture and illuminated on differential metabolite profiles and soil microbe’s relationship.

Silicon modifies C:N:P stoichiometry and improves the physiological efficiency and dry matter mass production of sorghum grown under nutritional sufficiency

Silicon (Si) may be involved in the modification of C:N:P stoichiometry and in physiological processes, increasing sorghum growth and grain production. The objective was to evaluate the effect of Si supply on C:N:P:Si stoichiometry, physiological response, growth, and grain production of sorghum. The experiment was carried out in pots with four concentrations of Si: 0; 1.2; 2.4; and 3.6 mmol L−1 in a completely randomized design, with six replicates. Physiological attributes and dark green color index were measured and grain and biomass production were determined. Posteriorly, the plant material was ground to determine silicon (Si), carbon (C), nitrogen (N), and phosphorus (P) contents in order to analyze C:N:P:Si stoichiometry. C:Si and C:N ratios decreased at all Si concentrations applied (1.2, 2.4, and 3.6 mmol L−1) and in all plant parts studied, being lower at 3.6 mmol L−1. The lowest C:P ratios of leaves and roots were observed at 3.6 mmol L−1 Si and the lowest C:P ratio of stems was observed at 1.2 mmol L−1 Si. Si concentrations were not significant for the N:P ratio of leaves. The highest N:P ratio of stems was observed at 3.6 mmol L−1, while the lowest N:P ratio of roots was observed at 2.4 and 3.6 mmol L−1. Regardless of photosynthetic parameters, the application of 1.2 mmol L−1 Si enhanced photosynthetic rate. The application of 2.4 and 3.6 mmol L−1 enhanced stomatal conductance and dark green color index. The mass of 1000 grains was not influenced by Si applications, while Si applications at all concentrations studied (1.2, 2.4, and 3.6 mmol L−1) enhanced shoot and total dry matter, not affecting root dry matter and grain production. In conclusion, Si supply modifies C:N:P:Si stoichiometry and increases physiologic parameters, growth, development, and grain production in sorghum.

Silicon Supplementation Alleviates the Salinity Stress in Wheat Plants by Enhancing the Plant Water Status, Photosynthetic Pigments, Proline Content and Antioxidant Enzyme Activities.

Silicon (Si) is the most abundant element on earth after oxygen and is very important for plant growth under stress conditions. In the present study, we inspected the role of Si in the mitigation of the negative effect of salt stress at three concentrations (40 mM, 80 mM, and 120 mM NaCl) in two wheat varieties (KRL-210 and WH-1105) with or without Si (0 mM and 2 mM) treatment. Our results showed that photosynthetic pigments, chlorophyll stability index, relative water content, protein content, and carbohydrate content were reduced at all three salt stress concentrations in both wheat varieties. Moreover, lipid peroxidation, proline content, phenol content, and electrolyte leakage significantly increased under salinity stress. The antioxidant enzyme activities, like catalase and peroxidase, were significantly enhanced under salinity in both leaves and roots; however, SOD activity was drastically decreased under salt stress in both leaves and roots. These negative effects of salinity were more pronounced in WH-1105, as KRL-210 is a salt-tolerant wheat variety. On the other hand, supplementation of Si improved the photosynthetic pigments, relative water, protein, and carbohydrate contents in both varieties. In addition, proline content, MDA content, and electrolyte leakage were shown to decline following Si application under salt stress. It was found that applying Si enhanced the antioxidant enzyme activities under stress conditions. Si showed better results in WH-1105 than in KRL-210. Furthermore, Si was found to be more effective at a salt concentration of 120 mM compared to low salt concentrations (40 mM, 80 mM), indicating that it significantly improved plant growth under stressed conditions. Our experimental findings will open a new area of research in Si application for the identification and implication of novel genes involved in enhancing salinity tolerance.

Effects of foliar silicon (Si) applications on tobacco plant under salt stress

Tuzluluk bitkilerde verim ve kaliteyi olumsuz yönde etkileyen en önemli abiyotik stres faktörleri arasında yer almasına karşılık, silisyum (Si) bitkilerde stres faktörlerini azaltan bir element olarak bilinmektedir. Bu çalışmada tütün bitkisinde tuz stresinin neden olduğu hasara karşı yapraktan Si uygulamalarının koruyucu etkisinin araştırılması amaçlanmıştır. Çalışmada dört farklı (0, 1.5, 3, 4.5 ve 6 dS m-1) tuz dozu altında yetiştirilen Canik 190/5 tütün çeşidine yapraktan 1 ve 2 defa Si uygulamaları yapılmıştır. Tüm bitki kuru madde verimi, Na, K, Ca, Mg, P konsantrasyonu ile K/Na oranı incelenmiştir. Artan dozlarda tuz uygulamaları tütün bitkisinin yeşil aksam kuru madde veriminde azalmaya neden olurken, yapraktan Si uygulamaları kuru madde verimlerindeki azalmayı yavaşlatmıştır. Kontrol uygulamalarının ortalama bitki kuru madde verimi 6.42 g bitki-1 iken, yapraktan 1 defa Si uygulamasında bu değer 6.65 g bitki-1’e çıkmış, yapraktan 2 defa Si uygulamasında ise 7.08 g bitki-1’e çıkmıştır. Silisyum uygulamaları tütün bitkisinin Na konsantrasyonlarında azalmaya neden olurken, K konsantrasyonları ile K/Na oranlarında artışa neden olarak bitkinin tuza karşı dayanıklılığını arttırmıştır. Çalışma sonucunda; tütün bitkisinin tuz stresine karşı dayanıklılığının arttırılmasında yapraktan Si uygulamalarının pozitif etkisinin olabileceği, uygulama sayısı bakımından ise yapraktan 2 defa uygulamanın daha etkili olduğu ortaya çıkmıştır.

Short-term responses of Spinach (Spinacia oleracea L.) to the individual and combinatorial effects of Nitrogen, Phosphorus and Potassium and silicon in the soil contaminated by boron.

While of lesser prevalence than boron (B) deficient soils, B-rich soils are important to study as they can cause B toxicity in the field and subsequently decrease crop yields in different regions of the world. We have conducted the present study to examine the role of the individual or combined application of silicon (Si) and NPK fertilizer in B-stressed spinach plants (Spinacia oleracea L.). S. oleracea seedlings were subjected to different NPK fertilizers, namely, low NPK (30 kg ha–2) and normal NPK (60 kg ha–2)], which were also supplemented by Si (3 mmol L–1), for varying levels of B in the soil i.e., 0, 250, and 500 mg kg–1. Our results illustrated that the increasing levels of B in the soil caused a substantial decrease in the plant height, number of leaves, number of stems, leaf area, plant fresh weight, plant dry weight, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content, net photosynthesis, stomatal conductance, transpiration rate, magnesium content in the roots, magnesium contents in the shoots, phosphorus content in the roots, phosphorus content in the leaves in the shoots, iron content in the roots, iron content in the shoots, calcium content in the roots, and calcium content in the shoots. However, B toxicity in the soil increased the concentration of malondialdehyde, hydrogen peroxide, and electrolyte leakage which were also manifested by the increasing activities of enzymatic [superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)], and non-enzymatic antioxidants (phenolic, flavonoid, ascorbic acid, and anthocyanin content). B toxicity in the soil further increased the concentration of organic acids in the roots such as oxalic acid, malic acid, formic acid, citric acid, acetic acid, and fumaric acid. The addition of Si and fertilizer levels in the soil significantly alleviated B toxicity effects on S. oleracea by improving photosynthetic capacity and ultimately plant growth. The increased activity of antioxidant enzymes in Si and NPK-treated plants seems to play a role in capturing stress-induced reactive oxygen species, as was evident from the lower levels of oxidative stress indicators, organic acid exudation, and B concentration in the roots and shoots of Si and NPK-treated plants. Research findings, therefore, suggested that the Si and NPK application can ameliorate B toxicity in S. oleracea seedlings and result in improved plant growth and composition under metal stress as depicted by the balanced exudation of organic acids.

Alleviation of Cadmium Stress by Silicon Supplementation in Peas by the Modulation of Morpho-Physio-Biochemical Variables and Health Risk Assessment.

Agricultural soil quality degradation by potentially toxic elements, specifically cadmium (Cd), poses a significant threat to plant growth and the health of humans. However, the supplementation of various salts of silicon (Si) to mitigate the adverse effect of Cd on the productivity of peas (Pisum sativum L.) is less known. Therefore, the present investigation was designed to evaluate the exogenous application at various levels (0, 0.50, 1.00 and 1.50 mM) of silicate compounds (sodium and potassium silicates) on pea growth, gaseous exchange, antioxidant enzyme activities and the potential health risk of Cd stress (20 mg kg−1 of soil) using CdCl2. The findings of the study showed that Cd stress significantly reduced growth, the fresh and dry biomass of roots and shoots and chlorophyll content. In addition, electrolyte leakage, antioxidant enzymes and the content of Cd in plant tissues were enhanced in Cd-induced stressed plants. An application of Si enhanced the development of stressed plants by modulating the growth of fresh and dry biomass, improving the chlorophyll contents and decreasing leakage from the plasma membrane. Furthermore, Si addition performed a vital function in relieving the effects of Cd stress by stimulating antioxidant potential. Hence, a significant level of metal protection was achieved by 1.00 mM of potassium silicate application under the Cd levels related to stress conditions, pointing to the fact that the Si concentration required for plant growth under Cd stress surpassed that which was required for general growth, enzymatic antioxidants regulation and limiting toxic metal uptake in plant tissues under normal conditions. The findings of this research work provide a feasible approach to reduce Cd toxicity in peas and to manage the entry and accumulation of Cd in food crops.

Silicon Reduces the Severity of Fusarium Infection on Young Wheat Parts In Vitro

Background: Although silicon (Si) has been referred as an essential element for controlling destructive diseases of wheat, available data are limited about enhancing adult wheat resistance against Fusarium causing head blight. Also, no reports seem to exist on the use of Si to reduce Fusarium seedling blight (FSB) on young wheat parts in vitro. Under in vitro conditions, Fusarium infection happened at the seedling stage cannot be called Fusarium head blight, because it is not a “head” disease, instead it could be called “FSB”. Objective and Methods: This research aimed to elucidate the bio-efficacy of soluble Si at 1.7 mM to increase wheat resistance to FSB measured by latent period (LP) of detached leaf inoculation, area under disease progress curve (AUDPC) of Petri-dish inoculation and coleoptile length reduction (CLR) of a coleoptile infection detected in vitro. Si treatments were applied to six bread and durum wheat cultivars of contrasting susceptibility to disease infected with four Fusarium species displaying a diverse pathogenicity. Results: Differences were observed on wheat detached leaves and seedlings in the resistance of Si-Fusarium-inoculated treatments relative to fungal-inoculated-controls, showing the beneficial role played by this element in decreasing head blight disease symptoms on young plant parts under in vitro conditions. In all wheat cultivars infected with different Fusarium species, the application of Si did increase host resistance measured in vitro; 1.7 mM Si resulted in significantly higher LP and lesser AUDPC and CLR compared with controls. More importantly, Si at 1.7 mM increased host resistance of susceptible to moderately susceptible cultivars measured by LP, AUDPC and CLR to the same level of resistance exhibited by a wheat cultivar high in quantitative resistance without Si. Conclusion: This is the first report presenting the utility of three distinct in vitro bio-assays to investigate the effect of Si in the wheat- FSB pathosystem. The application of silicon to complement host resistance to head blight appears to be an effective strategy for disease management in wheat.

Thermal activation mechanism of sulfur impurities in sulfur-hyperdoped silicon films

Thermal annealing has been widely used in the fabrication of microelectronic devices. However, the sub-bandgap infrared (wavelength λ = 1100–2500 nm) absorption of deep-level impurity hyperdoped Si wafer material usually decreases after thermal annealing treatment. This restricts the application of hyperdoped Si in room-temperature infrared photodetectors and broad-spectrum solar cells. Using a newly developed fabrication method, hyperdoping of Si with S was achieved by the nanosecond laser melting of Si/S composite films. Then, a thermal annealing treatment of S-hyperdoped Si (Si:S) films was carried out in a temperate range of T = 473–1273 K and a time range of t = 60–600 s under nitrogen ambient condition. The results show that at T = 1223 or 1273 K and t = 300 or 600 s, the sub-bandgap infrared and above-bandgap (λ = 200–1100 nm) absorbance were several times higher than those of unannealed Si:S films. Furthermore, the product of sheet electron concentration and electron mobility (NS×μ) indicates that these annealing conditions also showed better electrical properties than those of unannealed Si:S films. Combined with the microstructure analysis, the thermal activation mechanism can be proposed as follows: The thermal annealing treatment increased the crystallinity of Si:S films and the concentration of electrically active S impurities in the films. Then, the active S impurity atoms increased the ability of chemical bonding with Si atoms and forming SiS2. This effect induced by thermal annealing led to a high potential of optoelectronic devices fabricated with such Si:S films.

Alleviation of Cd-polluted paddy soils through Si fertilizer application and its effects on the soil microbial community

In this study, the effects of slag-based Si fertilizers on Cd-polluted paddy soils, soil microbial diversity, and functional properties were evaluated through a long-term field experiment conducted in a double-rice cropping system in southern China. The results showed that soil pH significantly increased from 5.15 to 6.13 after seven years of Si fertilization. Cd accumulation in both the soil and rice plants were significantly decreased for all the Si fertilizers treatments. Treatments using Si fertilizer in powder form exhibited the best alleviation effects, where soil available Cd decreased from 0.50 mg kg−1 to 0.43 mg kg−1, and Cd accumulation in rice roots, straw, and grains decreased by 32.2 %, 57.2 %, and 45.5 %, respectively, than that in the control. Following Si application, the soil microbial richness and Shannon diversity increased from 6731 to 7549 and 7.12 to 7.28, respectively. Proteobacteria, Nitrospirae, and Gemmatimonadetes, were significantly enriched in the Si-treated samples, whereas Verrucomicrobia, Chlamydiia, Ktedonobacteria and Candidatus_Saccharibacteria exhibited opposite patterns. Bioinformatics analysis using phylogenetic investigation of communities by reconstruction of unobserved states tools revealed that the varied microbial community induced functional adaption of soil microorganisms involved in metabolism, genetic information processing, cellular processes, and environmental information processing. The soil pH, NH4-N, and available Cd and Si contents were the key factors that best explained the variations in bacterial community composition among different treatments. Slag-based Si fertilizers are effective for Cd detoxication and can benefit the growth of rice plants throng the regulation of soil microorganisms.