Silicic Acid Research Articles

ROLE OF ENVIRONMENTAL SILICA IN BIOLOGICAL AND MICROBIAL STRESS MANAGEMENT FOR CROP PRODUCTION

The most prevalent mineral in the earth's mantle is silicon, which ranks second only to oxygen, but unlike oxygen, it has not been shown to be necessary for plant development. Plants can only absorb silicon in one of two forms: silicic acid (Si (OH) 4) or mono silicic acid (H4 SiO4), neither of which is found in the planet's crust as silicon dioxide (SiO2). Silicon fertilizer has been shown toboost agricultural output and sustainability, and its use has been met with widespread praise. When water is lost via the stomata of a plant, the gel that has been polymerized from the silicon solution in the roots is precipitated out of solution. It has been shown that polymerized gel has no significant part in the physical functions of the plant system. This article reviews the function that silicon in soil, water, and plants plays in protecting ecosystems against abiotic and biotic pressures. The interplay between silicon, plant species, and environments is nuanced.

Ascorbic Acid and Calcium Silicate Improve MorphoPhysiological Characteristics of Cadmium Stressed Mung Bean Crop

A rise in heavy metal contamination especially in the rhizosphere affecting the growth and yield of crops is a major concern. We aimed to study the influence of using calcium silicate (CS) and ascorbic acid (AsA) supplements on lowering the impact of cadmium-induced toxicityin mung bean. Both the supplements alone or in combination improved growth characteristics of cadmium (Cd) stressed mung bean plants like root-shoot length and fresh-dry weight. Leaf pigments like chlorophyll and carotenoids were also restored. A significant improvement in the relative leaf water content (RLWC) and low electrolyte leakage (EL) at the membrane was recorded. Results were more promising when combinations of CS and AsA treatments were used against the lower concentration of cadmium. Hence, both CS and AsA interact synergistically to alleviate Cd induced metal toxicity in mung bean plants.

Structural assessment of OsNIP2;1 highlighted critical residues defining solute specificity and functionality of NIP class aquaporins

IntroductionNodulin-26-like intrinsic proteins (NIPs) are integral membrane proteins belonging to the aquaporin family, that facilitate the transport of neutral solutes across the bilayer. The OsNIP2;1 a member of NIP-III class of aquaporins is permeable to beneficial elements like silicon and hazardous arsenic. However, the atomistic cross-talk of these molecules traversing the OsNIP2;1 channel is not well understood. ObjectiveDue to the lack of genomic variation but the availability of high confidence crystal structure, this study aims to highlight structural determinants of metalloid permeation through OsNIP2;1. MethodsThe molecular simulations, combined with site-directed mutagenesis were used to probe the role of specific residues in the metalloid transport activity of OsNIP2;1. ResultsWe drew energetic landscape of OsNIP2;1, for silicic and arsenous acid transport. Potential Mean Force (PMF) construction illuminate three prominent energetic barriers for metalloid passage through the pore. One corresponds to the extracellular molecular entry in the channel, the second located on ar/R filter, and the third size constriction in the cytoplasmic half. Comparative PMF for silicic acid and arsenous acid elucidate a higher barrier for silicic acid at the cytoplasmic constrict resulting in longer residence time for silicon. Furthermore, our simulation studies explained the importance of conserved residues in loop-C and loop-D with a direct effect on pore dynamics and metalloid transport. Next we assessed contribution of predicted key residues for arsenic uptake, by functional complementation in yeast. With the aim of reducing arsenic uptake while maintaining beneficial elements uptake, we identified novel OsNIP2;1 mutants with substantial reduction in arsenic uptake in yeast. ConclusionWe provide a comprehensive assessment of pore lining residues of OsNIP2;1 with respect to metalloid uptake. The findings will expand mechanistic understanding of aquaporin’s metalloid selectivity and facilitate variant interpretation to develop novel alleles with preference for beneficial metalloid species and reducing hazardous ones.

A REVIEW ON COMPREHENSION AND ACCRETION OF ARSENIC IN RICE (ORYZA SATIVA L.) PLANT

Consuming rice exposes you to arsenic (As), which is dangerous for your health. The buildup of As in rice was investigated in this study. According to research, Bangladesh and Taiwan have higher levels of As buildup in their rice than other nations. Furthermore, the key elements affecting the uptake of As into rice crops are described. Additionally, it was investigated if it would be possible to use efficient methods to lessen the buildup of As in rice. Arsenic is a hazardous element that has the ability to harm peoples health. In addition to being a source of both amino acids (AAs) and mineral elements, rice is an unwelcome supply of As for the billions of people who eat it as their main source of nutrition. A necessary metalloid called selenium (Se) has the ability to reduce As toxicity by enhancing antioxidant capacity. Through phosphate transporters and intrinsic channels that resemble nodulin 26, As(V) and As(III) are delivered to the root. The entry of methylated As, dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA), into the root may be significantly influenced by the silicic acid transporter. DMA(V) is very mobile in plants and is quickly translocated from root to shoot among As species. The use of microalgae and bacteria is the most effective agronomic strategy for reducing the uptake and accumulation of As in rice.

Arsenic Uptake, Transport, Accumulation in Rice and Prospective Abatement Strategies - A Review

Recent reports claim that arsenic (As) toxicity affects millions of individuals worldwide. A significant problem for rice output and quality as well as for human health is the high content of arsenic (As), a non-essential poisonous metalloid, in rice grains. Therefore, substantial research has been done on the interactions between rice and As in recent years. As rice plants uptake at the root surface is impacted by factors like radical oxygen loss and iron plaque. The absorption and movement of various As species as well as the transfer to sub cellular compartments include a multitude of transporters, including phosphate transporters and aquaglyceroporins. As III and AsV are transported into the root by phosphate transporters and intrinsic channels that mimic nodulin 26. The silicic acid transporter may have a substantial impact on how methylated As, dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA), enter the root. The issue of As contamination in rice is being addressed by researchers and practitioners to the best of their abilities. Making better plans may be aided by recent research on rice that explains the processes of arsenic ingestion, transportation, and metabolism at the rhizosphere. Common agronomic techniques, such as collecting rainwater for agricultural irrigation, using natural substances that aid in the methylation of arsenic, and biotechnology methods, may be investigated in an effort to lessen the uptake of arsenic by food crops. Innovative agronomic techniques and recent research findings on arsenic contamination in rice crops will be included in this review.

A cross-regional examination of patterns and environmental drivers of Pseudo-nitzschia harmful algal blooms along the California coast

Pseudo-nitzschia species with the ability to produce the neurotoxin domoic acid (DA) are the main cause of harmful algal blooms (HABs) along the U.S. West Coast, with major impacts on ecosystems, fisheries, and human health. While most Pseudo-nitzschia (PN) HAB studies to date have focused on their characteristics at specific sites, few cross-regional comparisons exist, and mechanistic understanding of large-scale HAB drivers remains incomplete. To close these gaps, we compiled a nearly 20-year time series of in situ particulate DA and environmental observations to characterize similarities and differences in PN HAB drivers along the California coast. We focus on three DA hotspots with the greatest data density: Monterey Bay, the Santa Barbara Channel, and the San Pedro Channel. Coastwise, DA outbreaks are strongly correlated with upwelling, chlorophyll-a, and silicic acid limitation relative to other nutrients. Clear differences also exist across the three regions, with contrasting responses to climate regimes across a north to south gradient. In Monterey Bay, PN HAB frequency and intensity increase under relatively nutrient-poor conditions during anomalously low upwelling intensities. In contrast, in the Santa Barbara and San Pedro Channels, PN HABs are favored under cold, nitrogen-rich conditions during more intense upwelling. These emerging patterns provide insights on ecological drivers of PN HABs that are consistent across regions and support the development of predictive capabilities for DA outbreaks along the California coast and beyond.

Removal of Silicic Acid from Feed Water Using a Tiron Combined Anion Exchange Resin Column

Thorough removal of silicic acid from treated water, as a water pretreatment procedure, is essential for the prevention of silica deposits on anion exchange resins and reverse osmosis membranes. In this study, thorough removal of silicic acid was achieved using a Tiron (1,2-dihydroxy-3,5-benzendisulfonate) combined resin. In the column experiment, it was confirmed that silicic acid could be removed below the detection limit of the molybdenum-blue methods. Tiron, which can form a stable 1:3 Si-Tiron complex in aqueous solutions, merges anion exchange resins (Tiron resin) and exhibits a strong silicic acid removal ability over a wide pH range (pH 2–10). In the regeneration process, silicic acid could be easily removed from the Tiron resin through acid treatment (pH 2, HCl), and a mild alkaline treatment (pH 8, NaOH solution) was used to restore the silicic acid removal ability. Following the acid and alkaline treatments, the removal ability of the regenerated Tiron resin was maintained, suggesting that the resin could be reused in water treatment systems. Excess inorganic anion species did not affect silicic acid removal.

Silicic acid electrolyte additive reduces charge transfer impedance at sub-ambient temperature for lithium-ion rechargeable batteries

Vehicle electrification is a critical application of lithium-ion batteries (LIBs), and it is essential to develop LIBs that can operate at sub-ambient temperatures with satisfying performance. Conventional LIBs have performance deficits at low temperatures which hinder their use in extreme environments. One approach to address this problem is to rationally engineer the electrode/electrolyte interface with electrolyte additives to improve the electrochemical kinetics at sub-ambient temperatures. In this work, silicic acid (SiAc) is incorporated into standard LIB electrolyte as an additive to enhance the capacity and energy density of LIBs at temperatures down to −20 °C. Full-cell impedance analysis and X-ray photoelectron spectroscopy of cycled electrodes point towards an additive-induced change in surface chemistry which alters the charge transfer process. It is proposed that the SiAc additive participated in the formation of solid electrolyte interphase (SEI) and lowered the activation energy of the interface impedance, assisting lithium ion transport across the interface at lower temperatures.

Distribution and dissolution kinetics of biogenic silica in sediments of the northern South China Sea

The dissolution efficiency of sedssimentary biogenic silica (bSiO2) dramatically affects the regeneration of dissolved silicic acid (dSi) at the sediment-water interface, which is a crucial pathway to maintain Si balance and silicic productivity growth in marine environments. We conducted wet alkaline leach and flow-through experiments to explore the dissolution behaviors of sedimentary bSiO2 in the northern South China Sea (NSCS), one of the largest marginal sea continental shelves. The bSiO2 contents of surface sediments were 0.64 - 2.06%, with an average of 1.04 ± 0.35%, varying with isobath water depth. The solubility of bSiO2 in surface sediments ranged from 227 μmol L-1 to 519 μmol L-1, and the dissolution rate constants varied from 0.67 to 1.53 yr-1 under specific conditions in lab incubation. The correlation between the biogenic materials (bSiO2, OC, and TN) revealed a different preservation pattern of bSiO2 in finer (Φ > ~ 5.5) and coarser (Φ< ~ 5.5) sediments. The high concentration of Al in sea water and “Al – detrital – bSiO2” interactions in sediments significantly interfered with the apparent solubility and dissolution dynamics of bSiO2. We combined the regional characteristics (primary production, bottom current, and resuspension-deposition) and the reconstructed dissolution kinetics of bSiO2 explained the mismatch between the surface (diatom biomass)/(total phytoplankton biomass) ratio and the sedimentary bSiO2/OC ratio, and the mismatch between the surface bSiO2 primary productivity and the bSiO2 sediment records in the NSCS. The resuspension-deposition, the higher reconstructed rate constants (0.94 ± 0.13 yr-1), and the dissolution rate (0.20 ± 0.01 yr-1) were responsible for the lower bSiO2/OC ratio (0.45 ± 0.28) at the inner shelf, and the winnowing process at the outer shelf with the lower reconstructed reactivity (0.30 yr-1) and dissolution rate (0.001 yr-1) led to the good preservation of bSiO2 in the upper slope. Furthermore, through the comparison with other sea areas, the relatively lower reactivity (1.12 ± 0.3 yr-1) of bSiO2 in sediments supported the notion that the NSCS sediments may serve as an important silica sink in the world ocean silica cycle.

Silica In Silico: A Molecular Dynamics Characterization of the Early Stages of Protein Embedding for Atom Probe Tomography

A novel procedure for the application of atom probe tomography (APT) to the structural analysis of biological systems, has been recently proposed, whereby the specimen is embedded by a silica matrix and ablated by a pulsed laser source. Such a technique, requires that the silica primer be properly inert and bio-compatible, keeping the native structural features of the system at hand, while condensing into an amorphous, glass-like coating. In this work, we propose a molecular dynamics protocol, aimed at depicting and characterizing the earliest stages of the embedding process of small biomolecules in a solution of water and orthosilicic acid, here, taken as a precursor of the silica matrix. Overall, we observe a negligible influence of orthosilicic acid on the behavior of stable folded systems (such as ubiquitin). Conversely, intrinsically disordered and unstable peptides are affected by the coating, the latter seemingly inhibiting the fluctuations of flexible moieties. While further scrutiny is in order, our assessment offers a first mechanistic insight of the effects of orthosilicic acid, thereby validating its use in the proposed innovative application of APT to the structural resolution of protein molecules.

Synergic role of frontal migration and silicic acid concentration in driving diatom productivity in the Indian sector of the Southern Ocean over the past 350 ka

The glacial-interglacial siliceous productivity in the Sub-Antarctic Zone (SAZ) of the Southern Ocean (SO) has been proposed to respond to higher dust-bearing iron fluxes and/or basin-wide increased nutrient supply to surface waters. However, long records of diatom productivity are mainly obtained from the Atlantic and Pacific sectors of the SO. We present a new diatom productivity record from the SAZ of the western Indian sector of the SO, where the Antarctic Circumpolar Current strongly interacts with bottom topography to create a productivity hotspot, during the last four glacial-interglacial cycles. Our results show that regional changes in diatom productivity did not follow a glacial-interglacial pattern. It was highest during the Marine Isotope stage (MIS) 6 and MIS4, lowest during MIS10-MIS8 and MIS3-MIS1, whereas intermediate diatom productivity was found during MIS7 and MIS5. Multi-millennial events of high diatom productivity were scattered throughout both the glacial and interglacial periods. Both long-term and rapid diatom productivity changes in the region were disconnected from dust flux changes, but might relate to frontal migrations and SO upwelling intensity changes which have both mediated the silica and iron availability for diatoms. Importantly, our data suggest that front migrations were not homogenous in the SO, especially where these fronts interact with bottom topography. The peculiarity of these productivity hotspots must be considered when drawing SO-wide carbon balance in the past.

Silicic and Ascorbic Acid Induced Modulations in Photosynthetic, Mineral Uptake, and Yield Attributes of Mung Bean (Vigna radiata L. Wilczek) under Ozone Stress.

Most of the world's crop production and plant growth are anticipated to be seriously threatened by the increasing tropospheric ozone (O3) levels. The current study demonstrates how different mung bean genotypes reacted to the elevated level of O3 in the presence of exogenous ascorbic and silicic acid treatments. It is the first report to outline the potential protective effects of ascorbic and silicic acid applications against O3 toxicity in 12 mung bean {Vigna radiata (L.) Wilken} varieties. Under controlled circumstances, the present investigation was conducted in a glass house. There were four different treatments used: control (ambient O3 concentration of 40-45 ppb), elevated O3 (120 ppb), elevated O3 with silicic acid (0.1 mM), and elevated O3 with ascorbic acid (10 mM). Three varieties, viz. NM 20-21, NM 2006, and NM 2016, showcased tolerance to O3 toxicity. Our findings showed that ascorbic and silicic acid applications gradually increased yield characteristics such as seed yield, harvest index, days to maturity, and characteristics related to gas exchange such as transpiration rate, stomatal conductance, net photosynthetic activity, and water-use efficiency. Compared to the control, applying both growth regulators enhanced the mineral uptake across all treatments. Based on the findings of the current study, it is concluded that the subject mung bean genotypes responded to silicic acid treatment more efficiently than ascorbic acid to mitigate the harmful effects of O3 stress.

Efficient separation and comprehensive extraction of aluminum, silicon, and iron from coal fly ash by a cascade extraction method

A cascade extraction method was constructed by combining alkali desilication with carbonation and acid leaching to achieve efficient separation and comprehensive recovery of aluminum, silicon, and iron products in coal fly ash (CFA). Alkaline desilication obtained the maximum SiO2 extraction efficiency of 65.7% after response surface methodology optimization, transformed mullite phase to hydroxysodalite [Na8Al6Si6O24(OH)2(H2O)2], and generated fiber-formed nanostructures, which were beneficial for resource extraction. After being treated by dosing Ca(OH)2 to recover CaSiO3 crystal, the supernatant of desilication was recycled to reduce alkali consumption and waste liquid discharge. The desilicated CFA was activated by carbonate calcination to convert mullite into the nepheline phase, thereby elevating the dissolution efficiency of Al2O3 and Fe2O3 to 90.4% and 92.3% by acid leaching. Acid leaching also converted silicious compounds in activated CFA to silicic acid with a purity of 93.9%. Stepwise precipitation obtained Fe(OH)3 and Al(OH)3 products with purities of 70.6% and 90.8%. The generated CaSiO3, silica gel, Fe(OH)3, and Al(OH)3 can be recycled as flame retardants, and the recovered Al(OH)3 could be converted to NaAlO2 for chloride removal from saline wastewater. The cascade extraction is economically beneficial and environmentally friendly without solid waste production for utilization of CFA.

Diverse scale deposition in response to the change in chemical properties of geothermal water at the Dieng geothermal power plant, Indonesia

The geothermal water discharged from the production well at the Dieng geothermal power plant experiences various drastic changes depending on the specific structure. As a result, various siliceous scales were found along the movement of the geothermal water at the Dieng geothermal power plant. To elucidate the geochemical property relationship between siliceous scales and geothermal waters at different locations, both the scale and the geothermal water samples were collected from (1) the inside of the two-phase pipeline, (2) the inside of the brine pipeline, and (3) at the open canal. The saturation index of the minerals was calculated based on the properties of the geothermal waters at each location to predict minerals that are possible to form. By comparing the properties of the scale and the mineral saturation index, quantitative mineral assemblage at each location was calculated, and the scale formation can be explained as follows. (1) Scale in the two-phase pipeline was composed of (Al, K)- and Fe-rich silicate, amorphous silica, and sulfide minerals formed at high temperature and near-neutral pH. The (Al, K)-rich and the Fe2+-rich silicates were controlled by the oversaturation of clinoptilolite and minnesotaite, and the amorphous silica was formed. The sulfide minerals were formed due to the high sulfur fugacity (fs2). (2) Scale in the brine pipeline was mainly composed of amorphous silica containing a small amount of (Al, K)-rich silicate formed under low pH (4∼5) and high-temperature conditions. (Al, K)-rich silicates were still precipitated even after acidification, likely due to the oversaturation of clinoptilolite above pH ∼4, and then the amorphous silica was formed. (3) Scale at the open canal was mainly composed of amorphous silica with small particles of hydrous ferric oxide (HFO), formed under an oxidizing condition at low temperature and low pH (4∼5). HFO reacted with silicic acid in geothermal water to form Fe3+-rich silicate that chemically resembles nontronite. The mineral with the highest proportion was amorphous silica in all three siliceous scales. Although the saturation index of amorphous silica was small, precipitation of amorphous silica may be induced and accelerated due to the adsorption of silicic acid on the (Al, K)-rich silicate and the Fe2+-rich silicate at high temperature and on the Fe3+-rich silicate at low temperature because of high surface area. The adsorbed silicic acid polymerizes on the silicate minerals.

Metal organic frameworks (MOFs) for the removal of dissolved silica before reverse osmosis desalination

Freshwater scarcity in many arid regions necessitates brackish water desalination via reverse osmosis (RO). One of the key obstacles to lowering the cost of RO freshwater is scaling or fouling on the RO membrane caused by dissolved silica in the brackish water. Herein, a robust metal organic framework (MOF) material was produced with green production methods. During column tests, the MOF demonstrates a high and selective affinity toward silicic acid from the dominant species in brackish water (e.g., Cl-, SO42-, HCO3-, Ca2+, Mg2+). Further lab-scale desalination tests showed over 80% of the 10–15 µm sized stone-like scales on the membrane were reduced while a 28.1% increase in the permeate flux was observed compared to the RO membrane without MOF treatment. Plus, two regeneration methods based on the properties of the selected MOFs were developed and evaluated.

Selection of precursors of safe silica-based fireproof coatings for textile materials

The selection of the inorganic precursor SiO2 as the main component of the simplified safe technology for obtaining flame-retardant coatings on textile materials was carried out. By thermo-graphic research of organic and inorganic SiO2 precursors, performed on an OD-102 deri-vatograph under conditions of heating at a rate of 10ºС/min in an air environment, the processes of decomposition of the coating that occur during the action of fire were investigated. Gels based on inorganic precursors produced by industry (silica sol, silica gel) and silicic acid, which was obtained by the exchange reaction of an aqueous solution of sodium silicate of liquid glass and acetic acid, were studied for the comparative characteristics of thermal destruction of coatings. As organic precursors of SiO2, gels of ethyl silicate-32 and methyltriethoxysilane were studied, which were obtained by hydrolysis of organosilicon compounds in an acidic water-alcohol medi-um with subsequent polycondensation of the hydrolysis products. The effect of temperature on the nature of thermal destruction of silica gel, silica sol, silicic acid and organosilicon gels of ethyl silicate and methylotriethoxysilane was investigated. It is shown that inorganic precursors differ favorably from organosilicon precursors in terms of the overall thermal effect during their de-composition, mass loss during heat treatment, and the rate of change of this parameter. Consider-ing that, in addition to total mass loss, the increase in mass loss during heating is less than 1 % in compositions based on inorganic precursors, it is possible to use all three types of inorganic pre-cursors, but from the point of view of acidity and safety of impregnation compositions, prefer-ence is given to silicic acid obtained by the exchange reaction of silicate sodium liquid glass with acetic acid.

Silicic acid and glutathione application improves elevated ozone toxicity tolerance by modulating biomass, senescence, seed quality attributes and oxidative stress indicators in sesame (Sesamum indicum L.)

Silicic acid and glutathione application improves elevated ozone toxicity tolerance by modulating biomass, senescence, seed quality attributes and oxidative stress indicators in sesame (Sesamum indicum L.)

Southern coastal system of the San Jorge Gulf during spring

The San Jorge Gulf was declared an area of national economic, commercial, conservation and diversity interest. To contribute to its study, the southern coastal sector of the gulf was characterised in physical and chemical parameters in spring campaigns (November 2016 and 2017). Samples were taken on board the oceanographic vessel Puerto Deseado in three perpendicular to the coast transects and another one to the southeast of the gulf, which crosses a thermohaline front. The perpendicular to the coast transects showed a similar pattern of distribution of physical and chemical properties in the water column. At nearshore stations, the water column was homogeneous and the nutrient concentrations between the surface and bottom layers were similar. At offshore stations, the water column was stratified and the nutrient concentrations were higher near the bottom than at surface. In 2016, a wind induced upwelling front was observed in the southwest of the gulf. Both sides of the thermohaline front did not show significant chemical differences. Throughout the study area, silicic acid and nitrate limited primary production. Satellite chlorophyll-a data and fluorescence profiles showed that the southern sector of the gulf has a high biomass of phytoplankton during November. We conclude that the southern sector of the SJG has different features depending on the external forcing caused by the front. The presence of fronts stimulates the growth of phytoplankton biomass through the injection of nutrients from the homogeneous part to the stratified sector. This would affect phytoplankton community and, thus, the productivity of the system.

Regulation of thermodynamics and kinetics of silica nucleation during the silicification process in higher plants

The formation mechanism of SiO2 aggregates is controversial because two contrasting hypotheses are often proposed to explain plant silicification. In this review, we summarize the physicochemical fundamentals of amorphous silica nucleation and discuss how plants regulate the process of silicification by influencing the thermodynamics and kinetics of silica nucleation. At silicification positions, plants overcome the thermodynamic barrier by establishing the supersaturation of the H4SiO4 solution and reducing the interfacial free energy. Among the thermodynamic-drivers, the establishment of supersaturation of H4SiO4 solution mainly depends on the expression of Si transporters for H4SiO4 supply, evapotranspiration for concentrating Si, and the other solutes in H4SiO4 solution for influencing the dissolution equilibrium of SiO2; while the interfacial free energy was reduced seemingly by the overexpression Na+/H+ antiporter SOS1 in high NaCl-stressed rice. Moreover, some kinetic-drivers, such as silicification-related proteins (Slp1 and PRP1) and new cell wall components, are actively expressed or synthesized by plants to interact with silicic acid, thereby reducing the kinetic barrier. According to classical nucleation theory, when the thermodynamic barrier is overcome, the super-saturated silicic acid solution (such as H4SiO4 in xylem sap) does not necessarily have to precipitate, just has the potential ability to precipitation. Thus, based on the mediators of SiO2 deposition at the thermodynamic-driven stage, it is difficult to evaluate whether the process of plant silicification is active or passive. We conclude that the characteristics of kinetic-drivers determine the mechanism of plant silicification.

Biogenic silica accumulation in picoeukaryotes: Novel players in the marine silica cycle.

It is well known that the biological control of oceanic silica cycling is dominated by diatoms, with sponges and radiolarians playing additional roles. Recent studies have revealed that some smaller marine organisms (e.g. the picocyanobacterium Synechococcus) also take up silicic acid (dissolved silica, dSi) and accumulate silica, despite not exhibiting silicon dependent cellular structures. Here, we show biogenic silica (bSi) accumulation in five strains of picoeukaryotes (<2-3μm), including three novel isolates from the Baltic Sea, and two marine species (Ostreococcus tauri and Micromonas commoda), in cultures grown with added dSi (100 μM). Average bSi accumulation in these novel biosilicifiers was between 30 and 92 amol Si cell-1 . Growth rate and cell size of the picoeukaryotes were not affected by dSi addition. Still, the purpose of bSi accumulation in these smaller eukaryotic organisms lacking silicon dependent structures remains unclear. In line with the increasing recognition of picoeukaryotes in biogeochemical cycling, our findings suggest that they can also play a significant role in silica cycling.