Silicon Supplementation Research Articles

Transporters regulate silicon uptake to make stripe rust resistant wheat genotypes more effective

Silicon (Si) supplementation is known to aid plants in mitigating various biotic and abiotic stressors. However, the mechanisms underlying Si-mediated stress alleviation, particularly the involvement of Si transporters and genotype-specific responses, remain poorly understood. Against this backdrop, we investigated the role of Si transporters in biotic stress alleviation in specific wheat genotypes infected with stripe rust. The primary objectives were to assess the role of Si accumulation in stripe rust resistance across different wheat genotypes and to determine how Si transporters affect their resistance responses. Twenty wheat genotypes were evaluated for their ability to accumulate Si in shoots, revealing significant variations among the selected genotypes. Resistant genotypes showed higher Si concentrations than susceptible ones, leading to the selection of two contrasting genotypes, viz., WW-120 (resistant) and K-88 (susceptible), for further analysis. In these genotypes, the expression of Si transporters and various physiological and biochemical responses were studied under stripe rust infestation with and without Si supplementation. We found that Si supplementation upregulated the expression of Si transporters, with a more pronounced increase in the resistant genotype than in the susceptible one, resulting in higher Si accumulation in the former. Moreover, differential physiological and biochemical responses to rust infection and Si supplementation were observed in both genotypes, indicating genotype-dependent variations across all measured variables. Our results suggest that higher Si accumulation in resistant wheat genotypes, due to the upregulation of Si transporters, plays a crucial role in their defense against rust infection. Further elucidation of these mechanisms could be used to enhance plant resistance to biotic stressors through targeted Si management.

Optimizing Drought-Resistant Cowpea Cultivar Selection Mediated by Silicon Supplementation using TOPSIS tool

Optimizing Drought-Resistant Cowpea Cultivar Selection Mediated by Silicon Supplementation using TOPSIS tool

Transient Expression of Nicotiana tabacum Silicon-Induced Histidine-Rich Defensins in Nicotiana benthamiana Limits Necrotic Lesion Development Caused by Phytopathogenic Fungi.

Silicon (Si) supplementation permits plants to better deter infection. Supplementing hydroponically-propagated Nicotiana tabacum with 1 mM potassium silicate (K2SiO3) reduced necrotic lesion development on detached leaves by both Botrytis cinerea and Sclerotinia sclerotiorum. Previously, a family of Si-induced genes was identified in N. tabacum. These genes were members of the Solanaceous Histidine-Rich Defensin (HRD) superfamily and were termed NtHRD1s (the first identified family of Nicotiana tabacum Histidine-Rich Defensins). Defensins were originally identified to participate in innate immunity. Thus, the NtHRD1s were tested for antimicrobial effects on plant pathogens. Transient expression of NtHRD1 genes within Nicotiana benthamiana leaves restricted the development of necrotic lesions caused by B. cinerea and S. sclerotiorum. Thus, the NtHRD1s may be an additional Si-responsive factor conferring beneficial effects on plants.

Impact of Integrated Nutrient Management Based on Silicon to Morpho-Physiological Changes on Maize: Enhancing Light Interception and Radiation use Efficiency

Environmentally sustainable maize cultivation is essential to optimise its growth and yield potential for global food security as a key goal in sustainable agriculture. Integrated Nutrient Management (INM), when coupled with silicon (Si) supplementation, has gained attention for its potential to improve crop productivity. This study investigates the impact of INM practices enriched with silicon on maize morphology and physiology changes, with a particular focus on increasing light interception (f) and Plant solar energy conversion efficiency (P-SECE) or the commons term called RUE. Experiments were conducted during the wet season of December 2022 to March 2023 in Triguna Abadi Grower group's Field Trial Center, Sukorambi Village, Jember, East Java, Indonesia. Two corn varieties which one is hybrid (P5027) and the other open pollinated (Lamuru) were cultivated using conventional chemical fertilizer and combined with the sole of INM and Si as well as INM+Si under a split plot design. The results showed that INM+Si significantly changed the morpho-physiological characteristics of plants so that the canopy architecture was ideal for increasing light interception in the vegetative phase by up to 3,23% compared to conventional fertilisation. In general,the INM, Si, and INM+Si fertilization methods were able to increase interception and photosynthetic efficiency compared to conventional fertilization, which had a positive impact on P-SECE levels till 1,66-2,36% and plant growth which illustrated an increase in dry weight up to 47,45%. Meanwhile, P5027, which has a more ideal canopy architecture than Lamuru, has relatively better interception efficiency, P-SECE, and growth. Significant findings related to sustainable agriculture are that Si fertilisation has a better macro-nutrient balance illustrated by the N/P ratio at 8.75. The increase in interception efficiency, RUE, and macro-nutrient balance due to the INM with Si Based fertilisation method led to increased plant growth and yield that support food security.

Elucidating the underlying mechanisms of silicon to suppress the effects of nitrogen deficiency in pepper plants

In many regions, nitrogen (N) deficiency limits pepper cultivation, presenting significant cultivation challenges. This study investigates the impact of N deficiency and silicon (Si) supplementation on physiological responses and antioxidant modulation in pepper plants, focusing particularly on the homeostasis of carbon (C), nitrogen, and phosphorus (P), and their effects on growth and biomass production. Conducted in a factorial design, the experiment examined pepper plants under conditions of N sufficiency and deficiency, with and without Si supplementation (0.0 mM and 2.0 mM). Results showed that N deficiency sensitizes pepper plants, leading to increased electrolyte leakage (39.59%) and disrupted C, N, and P homeostasis. This disruption manifests as reductions in photosynthetic pigments (−64.53%), photochemical efficiency (−14.92%), and the synthesis of key metabolites such as total free amino acids (−86.97%), sucrose (−53.88%), and soluble sugars (−39.96%), ultimately impairing plant growth. However, Si supplementation was found to alleviate these stresses. It modulated the antioxidant system, enhanced the synthesis of ascorbic acid (+30.23), phenolic compounds (+33.19%), and flavonoids (+7.52%), and reduced cellular electrolyte leakage (−25.02%). Moreover, Si helped establish a new homeostasis of C, N, and P, optimizing photosynthetic and nutritional efficiency by improving the utilization of C (+17.46%) and N (+13.20%). These Si-induced modifications in plant physiology led to increased synthesis of amino acids (+362.20%), soluble sugars (+51.34%), and sucrose (77.42%), thereby supporting enhanced growth of pepper plants. These findings elucidate the multifaceted biological roles of Si in mitigating N deficiency effects, offering valuable insights for more sustainable horticultural practices.

Silicon efficacy for the remediation of metal contaminated soil.

In the course of past two decade anthropogenic activities have reinforced, begetting soil and water defilement. A plethora of heavy metals alters and limits plant growth and yield, with opposing effect on agricultural productivity. Silicon often perceived as plant alimentary 'nonentity'. A suite of determinants associated with silicon have been lately discerned, concerning plant physiology, chemistry, gene regulation/expression and interaction with different organisms. Exogenous supplementation of silicon renders resistance against heavy-metal stress. Predominantly, plants having significant amount of silicon in root and shoot thus are barely prone to pest onset and manifest greater endurance against abiotic stresses including heavy-metal toxicity. Silicon-mediated stress management involves abatement of metal ions within soil, co-precipitation of metal ions, gene modulation associated with metal transport, chelation, activation of antioxidants (enzymatic and non-enzymatic), metal ion compartmentation and structural metamorphosis in plants. Silicon supplementation also stimulates expression of stress-resistant genes under heavy-metal toxicity to provide plant tolerance under stress conditions. Ergo, to boost metal tolerance within crops, immanent genetic potential for silicon assimilation should be enhanced. Current study, addresses the potential role and mechanistic interpretation of silicon induced mitigation of heavy-metal stress in plants.

Silicon: A Powerful Aid for Medicinal and Aromatic Plants against Abiotic and Biotic Stresses for Sustainable Agriculture

Silicon plays a crucial role in enhancing plant tolerance to various abiotic and biotic stresses, including drought, salinity, heavy metals, and pathogen/pest attacks. Its application has shown promising results in improving stress tolerance and productivity in medicinal plants. This review synthesizes findings from numerous studies investigating the mechanisms by which silicon confers stress tolerance, including the regulation of antioxidant systems, water relations, nutrient homeostasis, phytohormone signaling, and stress-responsive gene expression. Additionally, it examines the effects of silicon supplementation on the production of valuable secondary metabolites and essential oils in medicinal plants. Silicon application can significantly mitigate stress-induced damage in plants, including medicinally important species such as borage, honeysuckle, licorice, Damask rose, savory, basil, and eucalyptus. The deposition of silicon in cell walls provides physical reinforcement and acts as a barrier against pathogen invasion and insect herbivory. Furthermore, silicon fertilization can enhance the production of valuable secondary metabolites in medicinal crops under stress conditions. The findings underscore the potential of silicon fertilization as a sustainable strategy for improving the productivity and quality of medicinal crops under changing environmental conditions, highlighting the need for further research to elucidate the molecular mechanisms underlying silicon-mediated stress tolerance and practical applications in medicinal plant cultivation.

Synergistic Effects of Silicon and Aspartic Acid on the Alleviation of Salt Stress in Celery (Apium graveliens L.) "Si Ji Xiao Xiang Qin".

Salinity is one of the primary abiotic stresses that seriously hampers plant quality and productivity. It is feasible to reduce or reverse the negative effects of salt through the supplementation of silicon (Si) and aspartic acid (Asp). However, the question of how exogenous Si and Asp induce salt tolerance in celery remains incipient. Thus, this study was performed to determine the synergistic effects of Si and Asp on the alleviation of salt stress in celery. To this end, the celery plants were cultivated in a controlled regime (light for 14 h at 22 °C; darkness for 10 h at 16 °C) and treated with one of five treatments (CK, 100 mM NaCl, 100 mM NaCl + 75 mg/L Si, 100 mM NaCl + 100 mg/L Asp, and 100 mM NaCl + 75 mg/L Si + 100 mg/L Asp). Results showed that solely NaCl-treated celery plants developed salt toxicity, as characterized by decreased growth, declined photosynthetic ability, disturbed nutritious status and internal ion balance, and a boosted antioxidant defense system (Improved antioxidant enzymes and reduced ROS accumulation). In contrast, these adverse effects of NaCl were ameliorated by the additions of Si and Asp, regardless of Si, Asp, or both. Moreover, the mitigatory impacts of the co-application of Si and Asp on salt stress were more pronounced compared to when one of them was solely applied. Collectively, exogenous Si and Asp alleviate the degree of salt stress and thereby improve the salt tolerance of celery.

Silicon supplementation can reduce infestation by azalea lace bug-(Hemiptera: Tingidae).

The azalea lace bug (ALB), Stephanitis pyrioides (Scott) (Hemiptera: Tingidae), is a pest of azaleas and rhododendrons. The application of silicon (Si) to plants has been shown to accumulate in other plants and enhance defense to other plant pests. We evaluated whether Si applications decreased ALB infestation on rhododendron leaves and increased Si accumulation in leaves. Potted plants were treated with 4 or 8 weekly applications of calcium silicate and calcium carbonate (calcium control, Ca) via foliar or soil application. In 3 out of 4 choice studies, plants treated with calcium silicate or calcium carbonate had less frass deposition and oviposition by ALB compared to controls, but treated plants did not consistently have fewer ALB adults. Leaf damage was quantified in one study and leaves with more frass as an indicator of feeding had more visible damage. In no-choice studies, there were no differences between treatments in one study, but oviposition was greater on foliar/soil Si-treated plants than controls in another study. Since rhododendron aphids (Illinoia lambersi) appeared in the greenhouse during or after studies, we compared their colonization on previously treated rhododendrons. Infestation of new leaf rosettes or random leaves by I. lambersi was lower on plants sprayed with foliar silicon or calcium applied via soil in 2 studies. Treated rhododendrons did not accumulate extra Si or Ca in leaves compared to controls. In general, silicon or calcium application protected rhododendrons from ALB oviposition and aphid colonization in free-choice conditions, and may be part of an integrated pest management program.

Influence of Silicon Supplementation and Farmyard Manure on Yield Attributes of Tomato (Solanum lycopersicum Mill.) Var. SL-12: A Comparative Study

Influence of Silicon Supplementation and Farmyard Manure on Yield Attributes of Tomato (Solanum lycopersicum Mill.) Var. SL-12: A Comparative Study

Silicon improves the drought tolerance in pepper plants through the induction of secondary metabolites, GA biosynthesis pathway, and suppression of chlorophyll degradation

Drought stress caused by the global climate considerably disturbs plant yield and growth. Here, we explored the putative roles of silicon in repressing drought mechanisms in pepper and the prominent involvement of secondary metabolites, GA pathway, and photosystem II. Our research revealed that the transcript level of the flavonoid biosynthesis-associated genes, including the PAL, 4-CL, CHS, FLS-1, F3H and DFR, progressively induced in the pepper leaves treated with silicon during the drought stress duration. Moreover, the phenolic and flavonoid compounds extensively induced in the pepper plants. Furthermore, the pepper plants markedly inhibited chlorophyll catabolic-allied genes, senescence-related marker gene, and the Rbohs gene. Silicon application also sustained the membrane stability, supported via fewer electrolyte leakage processes and minor, O2– H2O2 and MDA levels during drought. Apart from this, the pepper plants significantly induced the expression level of the photosystem II-related genes, osmoprotectants pathway-associated genes, and antioxidant defense genes. Moreover, the GA biosynthesis genes were prompted, while the ABA signaling and biosynthesis genes were suppressed in the silicon-supplemented plants. These consequences infer that the role of Si supplementation on enhancing drought tolerance could be elucidated through the activation of secondary metabolites, flavonoid biosynthesis, osmoprotectants, GA pathway, the efficiency of PSII, and the suppression of chlorophyll degradation. Our research outcomes unveil new and remarkable characteristics of silicon supplementation and offer a series of candidate targets for improving the tolerance of pepper plants to drought stress.

Heavy metal toxicity induced by sewage water treatment in three different vegetables (lettuce, spinach and cabbage) was alleviated by brassinosteroid and silicon supplementation

Purpose: Heavy metal stress due to the application of sewage water is considered a leading factor for constrained plant growth. Therefore, Current study was performed in the field to investigate the interactive influence of two irrigation sources (canal and sewage) and exogenous application of brassinosteroid (BRs) and silicon (Si) at different rates on growth, photosynthetic and physiological attributes of three leafy vegetables (lettuce, cabbage, and spinach). Methods: Three treatments were applied such as control, BRs and Si with three replications under split plot factorial design. Results: The results indicated that all the growth parameters including fresh biomass of plants and roots, dry biomass of plant and root, leaf area (LA), photosynthetic traits, chlorophyll contents, water use efficiency (WUE), activity of antioxidant enzymes; superoxide dismutase (SOD), peroxidase (POD), Catalase (CAT), ascorbate peroxidase (APX) and uptake of silicon except Cd and Pb contents were improved significantly with the foliar spray of BRs and Si over control treatment under both types of irrigation sources. However maximum improvement in leafy vegetables was recorded when the foliar spray of BRs and Si were applied under canal water irrigation. Conclusions: The foliar application of BRs and Si was proved as an ameliorating strategy for improving tolerance mechanisms associated with heavy metal stress. The major restoring mechanism was the restricted translocation of Cd and Pb leading to better growth and physiology under sewage water. Thus the application of BRs and Si reduced the detrimental effect of Cd and Pb led to improve the growth and physiological traits of leafy vegetables under irrigation with sewage water.

Vanadium toxicity was alleviated by supplementation of silicon in tomato seedlings: Upregulating antioxidative enzymes and glyoxalase system

The primary goal of this research is to investigate the mitigating effect of silicon (Si; 2 mM) on the growth of tomato seedlings under vanadium (V; 40 mg) stress. V stress caused higher V uptake in leaf, and enhanced concentration of leaf anthocyanin, H2O2, O2•−, and MDA, but a decreased in plant biomass, root architecture system, leaf pigments content, mineral elements, and Fv/Fm (PSII maximum efficiency). Si application increased the concentrations of crucial antioxidant molecules such as AsA and GSH, as well as the action of key antioxidant enzymes comprising APX, GR, DHAR, and MDHAR. Importantly, oxidative damage was remarkably alleviated by upregulation of these antioxidant enzymes genes. Moreover, Si application enhanced the accumulation of secondary metabolites as well as the expression their related-genes, and these secondary metabolites may restricted the excessive accumulation of H2O2. In addition, Si rescued tomato plants against the damaging effects of MG by boosting the Gly enzymes activity. The results confirmed that spraying Si to plants might diminish the V accessibility to plants, along with promotion of V stress resistance.

Enhanced arsenic stress tolerance in landrace and improved rice cultivars through modulation of gibberellic acid (GA3) synthesis and antioxidant metabolism via phosphorus and silicon supplementation

Arsenic (As), an environmental pollutant, imposes toxic impacts on plant health. In recent years, researchers have focused on comprehending the As-induced intrusion in growth and metabolic components. However, the interactions between phosphorus (P) and silicon (Si) remain elusive, specifically in rice (Oryza sativa) cultivars. Therefore, the present study investigated the effects of P and Si on the defense mechanisms, nutrients accumulation, carbohydrate metabolism, gibberellic acid (GA3) synthesis, and growth responses in Indica rice cultivars (landrace and improved) under As stress. With this focus, our study potentially indicated that As stress (150 µM) negatively impacted the underlying physiological and growth traits, with more pronounced effects on the improved cultivar compared to the landrace. However, P (30 mg kg−1 soil) and/ or Si (1 mM) treatments have prominently reduced oxidative stress with improved defense mechanisms and GA synthesis. Modulation of enzymatic defense system increased in both cultivars but more pronounced in landrace, including superoxide dismutase (+36.47%, +24.43%), ascorbate peroxidase (+95.11%, +78.26%), along with non-enzymatic antioxidants such as ascorbate (+29.43%, +21.48%), and reduced glutathione (+75.45%, +62.34%) concentrations, respectively. Notably, GA concentration (+23.78%, +16.48%) was substantially increased by the cumulative application of P and Si under As stress in both cultivars but more conspicuous in the landrace, respectively. Further, employing GA biosynthesis inhibitor, paclobutrazol (PBZ; 10 µM), substantiated the input of GA-mediated As tolerance, wherein, PBZ reversed the impacts of P and Si on the endogenous GA concentration and defense metabolism. In summation, landrace outperformed improved cultivar leading to As tolerance. This implies that the landrace could be used for future breeding programs permitting in-depth considerations of P and Si-mediated GA3 synthesis under As stress conditions.

Silicon supplementation stabilizes the effect of copper stress, the use of copper chaperones and genes involved: a review.

Heavy metal stress is a major problem in present scenario and the consequences are well known. The agroecosystems are heavily affected by the heavy metal stress and the question arises on the sustainability of the agricultural products. Heavy metals inhibit the process to influence the reactive oxygen species production. When abundantly present copper metal ion has toxic effects which is mitigated by the exogenous application of Si. The role of silicon is to enhance physical parameters as well as gas exchange parameters. Si is likely to increase antioxidant enzymes in response to copper stress which can relocate toxic metals at subcellular level and remove heavy metals from the cell. Silicon regulates phytohormones when excess copper is present. Rate of photosynthesis and mineral absorption is increased in response to metal stress. Silicon manages enzymatic and non-enzymatic activities to balance metal stress condition. Cu transport by the plasma membrane is controlled by a family of proteins called copper transporter present at cell surface. Plants maintain balance in absorption, use and storage for proper copper ion homeostasis. Copper chaperones play vital role in copper ion movement within cells. Prior to that metallochaperones control Cu levels. The genes responsible in copper stress mitigation are discovered in various plant species and their function are decoded. However, detailed molecular mechanism is yet to be studied. This review discusses about the crucial mechanisms of Si-mediated alleviation of copper stress, the role of copper binding proteins in copper homeostasis. Moreover, it also provides a brief information on the genes, their function and regulation of their expression in relevance to Cu abundance in different plant species which will be beneficial for further understanding of the role of silicon in stabilization of copper stress.

Influence of Silicon Supplementation on Growth, Immunity, Antioxidant, Hormonal Profile and Bone Health Biomarkers in Pre-ruminant Crossbred Calves.

Silicon (Si), a newer trace element, is believed to be important for healthy bone formation and to decrease bone resorption, improving the quality of bone by manipulating several hormones and enzymes. Therefore, the current investigation was conducted to determine the impact of Si supplementation on growth, immunity, antioxidant, hormonal profile and biomarkers of bone health in pre-ruminant crossbred calves. Twenty-four crossbred calves (5-7 days) were selected on the basis of their body weight (BW 31.65 ± 0.46 kg) and divided into 4 groups (n = 6) and fed as per ICAR (2013) feeding standards except that these were additionally supplemented with 0 (Si0), 50 (Si50), 100 (Si100) and 150 (Si150) mg of Si/kg dry matter (DM) in four respective groups for 90 days. Every month, peripheral blood samples were drawn (0, 30, 60 and 90 days post supplementing with Si) and analysed for antioxidant status, hormonal profile and bone health biomarkers. It is reported that dietary Si supplementation improved (P < 0.05) net body weight gain (kg), average daily gain (g) and average dry matter intake (kg), whereas feed intake (kg/100 kg BW), was not altered due to Si supplementation. Structural growth measurements were significantly higher (P < 0.05) in Si100 and Si150 groups as compared to Si50 and control groups. However, immune response (humoral as well as cell-mediated immunity), erythrocytic antioxidant enzymes (superoxide dismutase, SOD, glutathione peroxidase, GPx and catalase), plasma ferric reducing total antioxidant power (FRAP) activity and the plasma concentration of total immunoglobulins (TIg) remained unaffected by Si supplementation. Silicon increased (P < 0.05) the concentration of plasma growth hormone (GH), vitamin D3, bone alkaline phosphatase (BALP) and osteocalcin (OCN) in Si100 and Si150 groups, but the levels of calcitonin, parathyroid hormone (PTH) and hydroxyproline (HYP) remained similar among all the groups. As a result of the current investigation, it can be inferred that the inclusion of 100 and 150 mg of Si/kg DM was effective in improving the growth performance, growth hormone, vitamin D3 and bone health status in pre-ruminant calves. However, supplementation of 150 mg of Si/kg DM had no additional benefit; therefore 100 mg of Si/kg DM is the optimum level of Si supplementation in pre-ruminant calves.

Silicon's Influence on Polyphenol and Flavonoid Profiles in Pea (Pisum sativum L.) under Cadmium Exposure in Hydroponics: A Study of Metabolomics, Extraction Efficacy, and Antimicrobial Properties of Extracts.

The current study aimed to investigate the impact of silicon (Si) supplementation in the form of Na2SiO3 on the metabolome of peas under normal conditions and following exposure to cadmium (Cd) stress. Si is known for its ability to enhance stress tolerance in various plant species, including the mitigation of heavy metal toxicity. Cd, a significant contaminant, poses risks to both human health and the environment. The study focused on analyzing the levels of bioactive compounds in different plant parts, including the shoot, root, and pod, to understand the influence of Si supplementation on their biosynthesis. Metabolomic analysis of pea samples was conducted using a targeted HPLC/MS approach, enabling the identification of 15 metabolites comprising 9 flavonoids and 6 phenolic acids. Among the detected compounds, flavonoids, such as flavon and quercetin, along with phenolic acids, including chlorogenic acid and salicylic acid, were found in significant quantities. The study compared Si supplementation at concentrations of 1 and 2 mM, as well as Cd stress conditions, to evaluate their effects on the metabolomic profile. Additionally, the study explored the extraction efficiency of three different methods: accelerated solvent extraction (ASE), supercritical fluid extraction (SFE), and maceration (MAC). The results revealed that SFE was the most efficient method for extracting polyphenolic compounds from the pea samples. Moreover, the study investigated the stability of polyphenolic compounds under different pH conditions, ranging from 4.0 to 6.0, providing insights into the influence of the pH on the extraction and stability of bioactive compounds.

Silicon improves root functioning and water management as well as alleviates oxidative stress in oilseed rape under drought conditions.

The aim of our study was to examine how silicon regulates water uptake by oilseed rape roots under drought conditions and which components of the antioxidant system take part in alleviating stress-induced ROS generation in the roots. The study analyzed mainly the changes in the roots and also some changes in the leaves of oilseed rape plants, including total silicon content, relative water content, osmotic potential, stomatal conductance, abscisic acid level, the accumulation of BnPIP1, BnPIP2-1-7 and BnTIP1 aquaporins, and the activity of antioxidant enzymes. It was shown that plants growing in well-watered conditions and supplemented with silicon accumulate smaller amounts of this element in the roots and also have higher relative water content in the leaves compared to the control plants. It was demonstrated for the first time that BnTIP1 accumulation in oilseed rape roots is reduced under drought compared to wellwatered plants, and that this effect is intensified in plants supplemented with silicon. In addition, it was shown that silicon supplementation of oilseed rape increases catalase activity in the roots, which correlates with their high metabolic activity under drought and ultimately stimulates their growth. It was shown that silicon improves water balance in oilseed rape plants subjected to drought stress, and that an important role in these processes is played by tonoplast aquaporins. In addition, it was demonstrated that silicon reduces oxidative stress in roots under drought conditions by increasing the activity of catalase.

The Physiological and Molecular Mechanisms of Silicon Action in Salt Stress Amelioration.

Salinity is one of the most common abiotic stress factors affecting different biochemical and physiological processes in plants, inhibiting plant growth, and greatly reducing productivity. During the last decade, silicon (Si) supplementation was intensively studied and now is proposed as one of the most convincing methods to improve plant tolerance to salt stress. In this review, we discuss recent papers investigating the role of Si in modulating molecular, biochemical, and physiological processes that are negatively affected by high salinity. Although multiple reports have demonstrated the beneficial effects of Si application in mitigating salt stress, the exact molecular mechanism underlying these effects is not yet well understood. In this review, we focus on the localisation of Si transporters and the mechanism of Si uptake, accumulation, and deposition to understand the role of Si in various relevant physiological processes. Further, we discuss the role of Si supplementation in antioxidant response, maintenance of photosynthesis efficiency, and production of osmoprotectants. Additionally, we highlight crosstalk of Si with other ions, lignin, and phytohormones. Finally, we suggest some directions for future work, which could improve our understanding of the role of Si in plants under salt stress.

Silicon Supplementation for Bone Health: An Umbrella Review Attempting to Translate from Animals to Humans.

Studies have attempted to demonstrate the benefits of silicon on bone health using a wide range of Si amounts-provided in the diet or through supplementation-and several different animal species. Previous studies in humans have also demonstrated a positive correlation between Si intake and bone health measures. The aim of the current review is to determine the effective levels of Si intake or supplementation that influence bone health to better inform future study designs and guidelines. Articles were identified using one of two search terms: "silicon AND bone" or "sodium zeolite A AND bone". Articles were included if the article was a controlled research study on the effect of Si on bone health and/or mineral metabolism and was in English. Articles were excluded if the article included human subjects, was in vitro, or studied silica grafts for bone injuries. Silicon type, group name, Si intake from diet, Si supplementation amount, animal, and age at the start were extracted when available. Dietary Si intake, Si supplementation amount, and the amount of Si standardized on a kg BW basis were calculated and presented as overall mean ± standard deviations, medians, minimums, and maximums. Studies that left out animal weights, amount of food or water consumed, or nutrient profiles of the basal diet were excluded from these calculations. Standardized Si intakes ranged from 0.003 to 863 mg/kg BW, at times vastly exceeding current human Si intake recommendations (25 mg/d). The lack of data provided by the literature made definitively determining an effective threshold of supplementation for skeletal health difficult. However, it appears that Si consistently positively influences bone and mineral metabolism by around 139 mg Si/kg BW/d, which is likely unfeasible to attain in humans and large animal species. Future studies should examine this proposed threshold more directly and standardize supplemental or dietary Si intakes to kg BW for better study replication and translation.