Si Accumulation Research Articles

Silicon sources for studies of rice plants in nutrient solutions

The objective of this work was to evaluate the effects of various Si sources currently used in studies of Si doses in nutrient solutions on dry matter yield and the accumulation of nutrients and Si in rice plants. Treatments of rice plants with three sources of Si (monossilicic acid, sodium metasilicate, potassium metasilicate) and a treatment without Si were allocated in a randomized block design with ten replications. After 39 days in the nutrient solution, the following traits were evaluated: leaf area, leaf specific mass, dry matter yield of roots and shoots, and levels of K, Na, and Si in leaves and roots. Si increased leaf area, leaf specific mass, and dry matter yield of shoots and roots regardless of the Si source. Levels of Si in leaves and roots were significantly higher in relation to the control treatment but no significant difference among Si sources was identified. It was also observed that K and Na were adequately balanced across the treatments. Thus, a cheaper and easier to obtain Si source, such as sodium metasilicate and potassium metasilicate, may be chosen to carry out studies of Si additions to nutrient solutions.

Silicate fertilization in non-conventional vegetables in the southern region of Minas Gerais in Brazil

ABSTRACT Considering that the beneficial effects of silicon on human health and it´s accumulation in plants are little explored, studies of mineral nutrition in non-conventional vegetables are extremely relevant. Thus, the objective of this work was to identify non-conventional vegetables responsive to silica fertilization and evaluate the effect of fertilization on the content and accumulation of Si and macronutrients in these plants. The experiment followed a 4 x 5 factorial design, with four species of non-conventional vegetables (Rumex acetosa L., Amaranthus retroflexus L., Sonchus oleraceus L. and Stachys byzantina) and five doses of Si (0, 25, 50, 100 and 150 mg dm-3). The relative chlorophyll index, the fresh and dry matter masses, the content and accumulation of Si and macronutrients were evaluated. The species A. retroflexus, S. oleraceus. and S. byzantina showed the highest contents and accumulation of Si. The application of doses above 100 mg dm-3 promoted the highest silicon content estimated for the species. The species A. retroflexus, R. acetosa and S. byzantina are non-silicon accumulators, whereas S. oleraceus is intermediate.

Coupled carbon and silicon cycling and characteristics in a subtropical watershed, China

Abstract Silicon (Si) and carbon (C) can couple at different timescales. Phytolith carbon fixation and silicate weathering are two key processes of this type of coupling. Silicate rock weathering sequesters CO2 and thus generates a net C sink, which is one way that C is removed from ecosystems. This study selected the Xiangxi River watershed as the research object, which is characteristic of typical watersheds found in subtropical regions, and continuously monitored for Si and C transfers in this basin. We were able to ascertain the Si and C coupled cycling relationship in this basin by analyzing the influence of environmental changes on these two elements. The main findings were as follows: (1) The atmospheric chemical CO2 sequestration rate in this subtropical basin was 14.2 kg hm−2 yr−1, wherein carbonates sequestered atmospheric CO2 at a rate of 5.4 kg hm−2 yr−1 and silicate rock sequestered atmospheric CO2 at a rate of 8.8 kg hm−2 yr−1. (2) Both rainfall and vegetation type had significant effects on Si and C migration. Different characteristics of canopy interception of each tree species had obvious dissociation effects on dissolved organic carbon (DOC), while the absorption or dissociation effect on dissolved silicate (DSi) differed among the various tree species. Basin soil was enriched with a large amount of organic C during the dry season, which was subsequently exported during the rainy season. (3) The Si input into the watershed was less than the Si output (the net accumulation of Si was −27 kg hm−2 yr−1), and the C input was greater than the C output (the net accumulation of C was + 2785 kg hm−2 yr−1). This study determined that the Xiangxi River watershed was an Si “source” and a C “sink”. The results of this study can provide a reference for further study of the coupling relationship between Si and C, and provide support for the study of ecosystem material balance.

Effects of Silicon and Zinc Nanoparticles on Growth, Yield, and Biochemical Characteristics of Rice

Silicon (Si) and Zn are beneficial for improving plant growth and human health. Fortifying rice (Oryza sativa L.) with Si and Zn can correct deficiencies of these elements in humans who consume rice. The present study evaluated the effects of different Si and Zn application forms as nanoparticles (NPs) foliar application and soil application (traditional fertilizers) on agronomic performance, grain yield (GY), Si and Zn accumulation, and protein content in rice tissue. The experiment was performed as a randomized complete block design with a factorial set of treatments that included three Si treatments (0, soil‐Si, nano‐Si) and three Zn treatments (0, soil‐Zn, nano‐Zn) with three replicates in two experimental farms (Mazandaran, Iran). The results indicated that Si and Zn applications by both NPs (300 g ha−1) and soil application (9 kg Zn ha−1 and 392 kg Si ha−1) ameliorated the yield components, yield, and nutrient accumulation in rice plant tissue. Application of nano‐Zn, nano‐Si, soil‐Zn, and soil‐Si significantly increased GY by 12.6, 9.5, 9.2, and 6.9%, respectively, above the control. Application of Si and Zn through NPs had greater effects than soil form for some experimental parameters, such as fortification of rice grains. Overall, our results suggest that Si and Zn applications as NPs could increase GY, reduce fertilizer costs and environmental pollution, and enrich rice grains with Si and Zn through improving agronomic and physiological traits, leading to higher GY and nutrients accumulation in grain.Core Ideas Application of Si and Zn increased the agronomic parameters and grain yield. There was no significant interaction among Si and Zn on grain yield. The nano‐Zn foliar spray had better effects than soil‐Zn application for grain Zn accumulation.

Luminescent and hydrophobic textile coatings with recyclability and self-healing capability against both chemical and physical damage

Luminescent and hydrophobic textile coatings with recyclability and self-healing capability against both chemical and physical damage were prepared, which present multi-functions and long service life cycles. The applications in self-cleaning, oil-water separation, and anti-counterfeit technology were successfully demonstrated. The coatings can be easily created onto different fabrics including cotton cloth, filter paper, and chemical fabric. A rare earth organic complex of SmTTAPhen(NO3)3 (STPN), silane modified epoxy oligomer, and bis(4-maleimidophenyl)methane (BMI) provide luminescence, hydrophobicity, as well as recyclability and self-healing capability, respectively, to the coatings. More specifically, high transparency but high luminescence were achieved due to the good dispersion of STPN in coating matrix, resulting from the hydron bonding between nitrate groups from STPN and hydroxyl groups from epoxy oligomer. Silane modification facilitated the accumulation of Si–O bonds on the free-surface of the coating, which offers hydrophobic features. The introduction of reversible Diels-Alder reactions provided the self-healing capability and recyclability. Upon heating using an electronic iron, the hydrophobicity can be recovered from physical or chemical damage to the coatings. Besides, the coatings on abandoned fabrics can be recycled and reused to a new bare fabric. We believe that the concept and coating materials are useful to further expand the areas of smart and multi-functional coatings with long service life.

Silicon and Plant Natural Defenses against Insect Pests: Impact on Plant Volatile Organic Compounds and Cascade Effects on Multitrophic Interactions.

Environmental factors controlling silicon (Si) accumulation in terrestrial plant are key drivers to alleviate plant biotic stresses, including insect herbivory. While there is a general agreement on the ability of Si-enriched plant to better resist insect feeding, recent studies suggest that Si also primes biochemical defense pathways in various plant families. In this review, we first summarize how soil parameters and climate variables influence Si assimilation in plants. Then, we describe recent evidences on the ability of Si to modulate plant volatile emissions, with potential cascade effects on phytophagous insects and higher trophic levels. Even though the mechanisms still need to be elucidated, Si accumulation in plants leads to contrasting effects on the levels of the three major phytohormones, namely jasmonic acid, salicylic acid and ethylene, resulting in modified emissions of plant volatile organic compounds. Herbivore-induced plant volatiles would be particularly impacted by Si concentration in plant tissues, resulting in a cascade effect on the attraction of natural enemies of pests, known to locate their prey or hosts based on plant volatile cues. Since seven of the top 10 most important crops in the world are Si-accumulating Poaceae species, it is important to discuss the potential of Si mobility in soil-plant systems as a novel component of an integrated pest management.

Effect of silicon on protein and lignin contents of two annual flower species

Abstract The beneficial effect of silicon on plants is known, but there are no studies demonstrating the effect of this element on protein and lignin production in ornamental plants. This study aimed to assess the effects of monosilicic acid fertigation at 0, 2, 4, and 8 mmol L-1 of Si on protein and lignin production of two ornamental species: Viola x wittrockiana Gams ex Nauenb. & Buttler ‘Majestic Giants II Fire’ e Tagetes erecta L. ‘Hero’ (color mix). The experiment was installed in a 4 × 2 factorial arrangement using a completely randomized design with five replications. After 90 days of the sowing, we assessed N and Si contents in shoot system, Si accumulation in shoot system, root, and total, and lignin and protein production. An increase in lignin followed by its reduction was observed from the concentration of 2.0 (4.29) and 4.3 (5.72) mmol L-1 of Si for Viola and Tagetes species, respectively. Silicon application promoted higher lignin content in T. erecta and V. x wittrockiana.

Effects of Silicon Fertilization on Soil Chemical Properties and Phytolith Formation of Phyllostachys pubescens

Silicon is benefit to Gramineae plants in growth and resistance to various stresses. However, the effect of silicon fertilizer application on Phyllostachys pubescens is still not investigated yet. Phyllostachys pubescens Mazel ex J. Houz is one kind of Gramineae plants which distributes in a large area. In this study, a field experiment with five Si fertilizer application rates (0, 125, 250, 375, and 500 kg ha-1) was setup in a Phyllostachys pubescens forest in China to examine the effects of Si fertilizer on bamboo Si and phytolith accumulation in fresh leaf and leaf litter. Results showed that Si application increased soil available Si content in deep layers. Si content of leaf-litter increased with the increasing level of Si fertilizer application rate, with the value ranging from 114.3 g kg−1 to 172.7 g kg−1, however, no significant difference was observed in fresh leaf, with the value ranging from 84.0 g kg−1 to 115.0 g kg−1. The phytolith contents of leaf-litter and fresh leaf were consistent with the Si contents, the phytolith content in leaf-litter of T4 (500 kg ha-1) was 48.4% higher than the control, suggesting Phyllostachys pubescens exhibited an increasing carbon sink in phytolith when Si fertilizer applied, which is an effective way to increase long-term soil organic carbon storage in Phyllostachys pubescens forests with a suitable Si fertilization.

Silicon Uptake and Localisation in Date Palm (Phoenix dactylifera) - A Unique Association With Sclerenchyma.

Date palm (Phoenix dactylifera) can accumulate as much as 1% silicon (Si), but not much is known about the mechanisms inherent to this process. Here, we investigated in detail the uptake, accumulation and distribution of Si in date palms, and the phylogeny of Si transporter genes in plants. We characterized the PdNIP2 transporter following heterologous expression in Xenopus oocytes and used qPCR to determine the relative expression of Si transporter genes. Silicon accumulation and distribution was investigated by light microscopy, scanning electron microscopy coupled with X-ray microanalysis and Raman microspectroscopy. We proved that PdNIP2-1 codes for a functional Si-permeable protein and demonstrated that PdNIP2 transporter genes were constitutively expressed in date palm. Silicon aggregates/phytoliths were found in specific stegmata cells present in roots, stems and leaves and their surfaces were composed of pure silica. Stegmata were organized on the outer surface of the sclerenchyma bundles or associated with the sclerenchyma of the vascular bundles. Phylogenetic analysis clustered NIP2 transporters of the Arecaceae in a sister position to those of the Poaceae. It is suggested, that Si uptake in date palm is mediated by a constitutively expressed Si influx transporter and accumulated as Si aggregates in stegmata cells abundant in the outer surface of the sclerenchyma bundles (fibers).

Differences in biomass and silica content in typical plant communities with ecotones in the Min River estuary of southeast China.

Silica (Si) is a basic nutrient requirement for many aquatic organisms and its biogeochemical cycle plays an important role in estuarine coastal ecosystems. However, little is known about the role Si plays during plant–plant interactive processes in the marsh ecosystems. Here, variations in biomass, biogenic silica (BSi) content, and available Si content of Cyperus malaccensis-dominated marshes, Phragmites australis-dominated marshes, and their ecotonal marshes were studied in the Shanyutan marsh in the Min River estuary, China. Results showed that C. malaccensis and P. australis biomass in ecotones was lower than those in typical communities by 46.4% and 46.3%, respectively. BSi content in aboveground organs of C. malaccensis and culms and roots of P. australis was lower in ecotones than in typical communities, whereas BSi content in other organs showed the opposite trend. Biomass allocation in C. malaccensis and P. australis roots in ecotones was higher by 56.9% and 19.5%, respectively, and BSi stock in C. malaccensis and P. australis roots was higher than that in typical communities by 120.9% and 18.9%, respectively. Available Si content in ecotonal marsh soils was 12.6% greater than that in typical communities. Thus, the two plant species may use different strategies for Si accumulation and allocation in ecotones to adapt to the competitive environment. P. australis may expand primarily via occupation of wider aboveground space, thereby increasing the Si accumulation capacity in aboveground organs. Meanwhile, C. malaccensis may increase the Si allocation capacity of its roots to withstand the pressure from P. australis. This study will provide new insights into marsh plant competition from the perspective of Si, which can also benefit plant management in marsh ecosystems.

Silicon attenuates sodium toxicity by improving nutritional efficiency in sorghum and sunflower plants

Salt stress is known to negatively affect the fundamental processes in plants, reducing their growth and yield. The role of Silicon (Si) to protect the sorghum and sunflower plants against salinity stress was assessed. The objective of this study was to evaluate the effects of different forms of Si application on the uptake and use efficiency of macronutrients and micronutrients in sorghum and sunflower plants under salinity stress under greenhouse conditions. Two experiments were conducted using sorghum and sunflower under greenhouse conditions. Four Si levels were applied to plants: no Si application; foliar application of 28.6 mmol.L−1; root application of 2.0 mmol.L−1; and combined Si application with both via nutrient solution and foliar spraying. Each Si treatment was applied in the absence and presence of NaCl (100 mM). Thirty days after treatments, sodium (Na+) and Si accumulation, nutrient uptake and use efficiency, and the roots and total plant dry weight were measured. Salinity stress induced nutritional imbalance and decreased dry weight production in both plant species. Our results showed that Si application alleviated the salinity stress by decreased Na+ uptake and increased nutritional efficiency, thereby favoring the total plant dry weight in sorghum by 27% and sunflower by 41%. This occurred when Si was applied either via root or in combination via root and foliar application, respectively. Collectively, our findings indicate that Si application can attenuate the deleterious effects of salt stress and increase yield in sorghum and sunflower plants in a sustainable manner.

The Investigation of Silicon Localization and Accumulation in Citrus.

Several studies have demonstrated Si absorption in monocotyledon and dicotyledon species. Regarding Si accumulation, studies in monocotyledons have identified Si deposition around the cell wall, cuticle layer bulliform cells, silica cells and endodermal cells. In previous studies with different citrus species there were evidence of Si accumulation, however no information on Si deposition can be found. Therefore, in this study, Si was applied (0 and 1000 mg L−1) to the roots of two citrus species, ‘Delta’ Valencia (Citrus sinensis) and ‘Nules’ Clementine (Citrus reticulata). Si accumulation were investigated in new, and old leaves and roots. Si deposition was investigated through scanning electron microscopy using energy dispersive analysis X-ray, environmental scanning electron microscopy and light microscopy. Si accumulation was significantly higher in Si treated leaves comparatively to the control in both young and mature leaves. Meanwhile, Si accumulation increased with leaf age. Additionally, Si accumulation was significantly higher in roots than in leaves. With respect to Si deposition, granules were identified in the epidermal cells through SEM and ESEM studies. The light microscopy identified the presence of Si granules in the surface and around the outer cell surface forming the cuticle-silica double layer of the lower epidermis in Si treated plants. Silica deposit were not found on the abaxial leaf surface. The findings suggest a passive uptake in citrus species.

Spatial variations of soil silicon availability and biogenic silicon flux in a lowland tropical forest in Malaysia

AbstractTropical tree species differ widely in their silicon (Si) accumulation patterns, but the implications of such species differences for ecosystem Si flux remain unexplored. We analyzed how biogenic Si flux via leaf litter and soil Si availability in the upper soil vary spatially within a 2 ha area in a lowland Dipterocarp forest in Peninsular Malaysia. Silicon concentration per unit leaf dry mass of 86 dominant tree species in this plot ranged from 0.4 to 126 mg/g. Soil Si availability at 100 sampling points and Si flux via leaf litter at 66 litter traps showed large variations up to 3.3‐ and 17.9‐folds, respectively. However, they correlated neither with each other nor with the expected Si flux from tree species composition in the neighborhood. When we classified tree species to four groups by their leaf Si concentrations (negligible, low, moderate and high), tree species with moderate leaf Si concentrations were significantly more abundant on Si‐rich soils. In contrast, the other three groups did not show any significant spatial relationships with soil Si availability. These results indicate that soil Si availability, Si accumulation by vegetation and Si flux via leaf litter show wide spatial variations in a lowland tropical forest, without a simple relationship with each other.

Silicon Affects Root Development, Tissue Mineral Content, and Expression of Silicon Transporter Genes in Poinsettia (Euphorbia pulcherrima Willd.) Cultivars.

The effects of silicon (Si) on root development, mineral content, and expression of Si transporter genes in Euphorbia pulcherrima Willd. ‘Flame’, ‘Mable Bell’, ‘Green Star’, ‘Pink Bell’, and ‘Peach Bowl’ cultivars were investigated in this study. Stem cuttings in a propagation bench were drenched regularly with a solution containing either 0 (control) or 50 ppm of silicon (Si treatment) from potassium silicate (K2SiO3), with a 25 °C mean air temperature and 80% relative humidity (RH) under 70% shading. The results showed that the ‘Flame’ treated with Si had a significantly higher survival ratio as compared with that of the control (P ≤ 0.05) and that the Si treatment improved number of roots, length of longest root, fresh root weight, and dry root weight in all cultivars except ‘Mable Bell’. Supplementary Si increased the content of magnesium (Mg) and decreased the content of boron (B) and zinc (Zn) in the roots. The content of sulfur (S) in the shoots was increased by supplementary Si. The relative expression of Lsi1 and Lsi2 was higher in ‘Peach Bowl’, while it was lower in ‘Mable Bell’ and ‘Green Star’, which may be caused by the differing accumulation of Si in the shoot. Overall, supplementary Si had beneficial effects during cutting propagation of poinsettia cultivars, although these effects were cultivar-dependent.

Influence of Silicon Fertilization on Nutrient Accumulation, Yield and Fruit Quality of Melon Grown in Northeastern Brazil

The northeast region is the main producer of melons in Brazil. Soils under melon cultivation in this region are mainly pH-neutral and sandy, and hence prone to respond to Si fertilization, but there are no studies investigating Si application and melon responses in such an important producing area. To address this, here we carried out a field experiment to evaluate the effects of applying a diatomaceous earth-based fertilizer to melon grown on a Si-depleted soil from northeastern Brazil. The yield, weight, number, and quality of fruits, as well as the accumulation of Si and nutrients in melon leaves were evaluated. We found that Si fertilizer application increased the number, weight, and tonnage of melon fruits. This improvement in yield was related to an enhanced Si and nutrient uptake (N, P, K, Ca, Mg, Fe, Mn and Zn) by melon plants with the addition of silicon. Applying Si to soil did not significantly improve the pulp thickness, pulp firmness or soluble solids of melon fruits, despite a trend towards increased pulp thickness and soluble solids. The benefits of Si application were clearly observed to melon grown in sandy soils of northeast Brazil, but careful dose recommendation must be observed to make the practice cost-efficient and sustainable.

Deficiency in Silicon Transporter Lsi1 Compromises Inducibility of Anti-herbivore Defense in Rice Plants.

Silicon (Si) application can significantly enhance rice resistance against herbivorous insects. However, the underlying mechanism is elusive. In this study, silicon transporter mutant OsLsi1 and corresponding wild-type rice (WT) were treated with and without Si to determine Si effects on rice resistance to leaffolder (LF), Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae). Si application on WT plants significantly promoted rice plant growth, upregulated expression level of OsLsi1 and increased Si accumulation in the leaves and roots, as well as effectively reduced LF weight gain, while it showed only marginal or no effect on the mutant plants. Furthermore, upon LF infestation, transcript levels of OsLOX, OsAOS2, OsCOI1a, OsCOI1b, and OsBBPI, and activity of catalase, superoxide dismutase, peroxidase, and polyphenol oxidase were significantly higher in Si-treated than untreated WT plants. However, OsLsi1 mutant plants displayed higher susceptibility to LF, and minimal response of defense-related enzymes and jasmonate dependent genes to Si application. These results suggest that induced defense plays a vital role in Si-enhanced resistance and deficiency in silicon transporter Lsi1 compromises inducibility of anti-herbivore defense in rice plants.

Silicon Supplementation Alleviates Ammonium Toxicity in Sugar Beet (Beta vulgaris L.)

The purpose of this study is to evaluate the relationship between Si and NH4+ toxicity in the context of the nutrition, physiology, and production of sugar beet grown using hydroponics. We hypothesized that NH4+ affects the physiology of the plant, accumulation of nutrients, and dry matter, with the possibility for Si to mitigate this toxicity. The experimental design used was completely randomized, in a factorial scheme of 2 × 5, corresponding with the absence and presence of Si (2 mmol L−1) and five concentrations of NH4+ with four replicates. The following series of physiological evaluations were carried out: photosynthesis, stomatal conductance, transpiration, with the use of an infrared gas analyzer (LICOR, Inc., LI-6400), the dry biomass, N and Si accumulation, and Si use efficiency in the roots. Accumulation of N and photosynthesis in the leaves was higher in the presence of Si. An increase of NH4+ increased transpiration, especially in the plants cultivated without the incorporation of Si. Stomatal conductance was lower in the presence of Si. Dry matter was reduced when plants were exposed to higher concentrations of NH4+, showing a greater reduction in the root than in the aerial part. The use of NH4+ equal to or higher than 15 mmol L−1 damaged the photosynthesis. Transpiration and stomatal conductance were less affected in the presence of Si and in the accumulation of N and Si in the roots. Dry matter was reduced when plants were exposed to higher concentrations of NH4+, and this effect was mitigated in the presence of Si.

Electron spin and momentum lifetimes in two-dimensional Si accumulation channels: Demonstration of Schottky-barrier spin metal-oxide-semiconductor field-effect transistors at room temperature

We have investigated the electron spin lifetime ${\ensuremath{\tau}}_{\mathrm{S}}$ and momentum lifetime $\ensuremath{\tau}$ in a two-dimensional (2D) accumulation channel of Schottky-barrier spin metal-oxide-semiconductor field-effect transistors (spin MOSFETs). The spin MOSFETs examined in this study have Fe/Mg/MgO/Si Schottky-tunnel junctions at the source/drain and a 15-nm-thick nondegenerated Si channel with a phosphorus donor doping concentration ${N}_{\mathrm{D}}$ of $1\ifmmode\times\else\texttimes\fi{}{10}^{17}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$. We estimated $\ensuremath{\tau}$ and the electron diffusion coefficient ${D}_{e}$ in the 2D accumulation channel from experimental results of a Hall-bar-type MOSFET device and self-consistent calculations using Poisson's and Schr\odinger's equations. The spin MOSFETs with various channel lengths ${L}_{\mathrm{ch}}\phantom{\rule{0.28em}{0ex}}(=0.3\ensuremath{-}10\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m})$ exhibited transistor characteristics with a high on/off ratio of $\ensuremath{\sim}{10}^{6}$ as well as clear spin-valve signals at 295 K. From the spin-valve signals measured with various gate electric fields $(2\ensuremath{-}5\phantom{\rule{0.16em}{0ex}}\mathrm{MV}/\mathrm{cm}), {\ensuremath{\tau}}_{\mathrm{S}}$ and the electron spin diffusion length ${\ensuremath{\lambda}}_{\mathrm{S}}$ were estimated. We found that the spin-flip rate per one momentum scattering event $\ensuremath{\tau}/{\ensuremath{\tau}}_{\mathrm{S}}$ is $\ensuremath{\sim}1/14\phantom{\rule{0.16em}{0ex}}000$, which is almost unchanged by the gate electric field. The proportionality between ${\ensuremath{\tau}}_{\mathrm{S}}$ and $\ensuremath{\tau}$ indicates that the Elliott-Yafet mechanism is dominant in the Si 2D electron accumulation channel, and that the spin-flip rate per one phonon scattering event and that per one surface roughness scattering event are the same. Based on the Elliott-Yafet theory, there is a possibility that the spin-orbit coupling in the Si 2D accumulation channel is almost twice as strong as that in bulk Si materials.

A Review on Si Uptake and Transport System.

Silicon (Si) was long listed as a non-essential component for plant growth and development because of its universal availability. However, there has been a resurgence of interest in studying the underlying uptake and transport mechanism of silicon in plants because of the reported dynamic role of silicon in plants under stressed environmental conditions. This uptake and transport mechanism is greatly dependent upon the uptake ability of the plant’s roots. Plant roots absorb Si in the form of silicic acid from the soil solution, and it is moved through different parts of the plant using various influx and efflux transporters. Both these influx and efflux transporters are mostly found in the plasma membrane; however, their location and pattern of expression varies among different plants. The assessment of these features provides a new understanding of different species-dependent Si accumulations, which have been studied in monocots but are poorly understood in other plant groups. Therefore, the present review provides insight into the most recent research exploring the use of Si transporters in angiosperms and cryptogams. This paper presents an extensive representation of data from different families of angiosperms, including monocots and eudicots. Eudicots (previously referred to as dicots) have often been neglected in the literature, because they are categorized as low/intermediate Si accumulators. However, in this review, we attempt to highlight the accumulating species of different plant groups in which Si uptake is mediated through transporters.

Silicon alleviates long-term copper toxicity and influences gene expression in Nicotiana tabacum

Silicon (Si) is beneficial for plant growth and aids in stress tolerance. In this study, the effects of Si on long-term copper (Cu) toxicity in the low Si accumulator Nicotiana tabacum were evaluated. Silicon supplementation alleviated growth inhibition in roots and shoots of N. tabacum exposed to Cu toxicity. Alleviation of Cu toxicity correlated with increased Si accumulation in roots and leaves, suggesting N. tabacum contains a stress-regulated mechanism for Si transport. Root Cu concentration decreased in Si-supplemented plants exposed to Cu toxicity. Interestingly, Copper Transporter 1 (COPT1) expression decreased in roots of Si-supplemented plants exposed to Cu toxicity, which may contribute to Cu uptake reduction. Decreases in ethylene (ET) biosynthetic gene expression were previously implicated in Si-mediated stress alleviation. In the present study, Si-mediated alleviation of Cu toxicity corresponded with increased ET biosynthetic gene expression.