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Rapid, micro-methods to estimate plant silicon content by dilute hydrofluoric acid extraction and spectrometric molybdenum method I. Silicon in rice plants and molybdenum yellow method
Abstract
By treating 0.5 g DW of a plant sample directly with 10 ml of a dilute hydrofluoric acid solution (HF solution, 1.5 M HF-0.6 M HCl), all the silica in plant (as much as 150 mg SiO2) was dissolved within 1 h. After dilution of the extract with 40 mL of distilled water, the silica in the extract was measured by the spectrometric molybdenum yellow method. The molybdenum yellow method, in which silica in 0.1 mL of the diluted extract can be determined in 8 min, is well suited to rapid, micro-estimations of the silica content in plants. In the micromodification, the size of the plant sample was reduced to 100 mg DW. The analytical procedure was simple, and the analytical time was less than 2 h. The method can save much labor and time, compared with the gravimetric analysis. The dissolution with HF solution and the molybdenum yellow method were also applied to the measurement of the content of silica separated by acid digestion of rice plants. Excellent agreement in the silica measurement of rice plants was confirmed among the direct extraction method, the gravimetric method and the digestion-separation-dissolution method. In the molybdenum yellow method, the addition of boric acid enabled to mask the interference of hydrofluoric acid, and the least amount of citric acid required for the elimination of phosphorus interference was proposed. In conclusion in this report, recommended methods for the rapid estimation of the silica content in rice plants were presented.
... Silica was determined using the molybdenum yellow method described by Saito et al. (2005). Dried hulls (section ''Materials (Mini-Core)'') or grains (section ''Materials (silica concentration in the rice grain)'') (0.2 g) were placed in 15 ml polypropylene tubes and 10 ml of hydrofluoric acid (HF) solution (1.5 M hydrofluoric acid-0.6 ...
... After vortexing and allowing to sit at room temperature for 3 min., 1 ml of 0.5 M citric acid and 900 ll of water was added to each sample (total = 10 ml), vortexed and allowed to sit at room temperature for 10 min. The developed color was read at 400 nm using a Cary 50 spectrophotometer (Varian Australia Pty. Ltd., Mulgrave, Victoria, Australia) and converted to silica concentration according to Saito et al. (2005). Silica concentrations were expressed on a dry weight basis. ...
... Since the extraction process will remove components other than silica, the increase in the 2h = 22.0°p eak may be due to the difference in the relative concentration of the remaining silica to the undissolved material. Saito et al. (2005) found that the aforementioned method had a high correlation to the gravimetric method. They speculated that the slight increase in silica concentration seen in the gravimetric method may be due to incomplete dehydration or impurities. ...
An association analysis on the genetic variability for silica concentration in rice hulls was performed using a "Mini-Core" set of 174 accessions representative of the germplasm diversity found in the USDA world collection of rice. Hull silica concentration was determined in replicated trials conducted in two southern states in the USA and was analyzed for its association with 164 genome-wide DNA markers. Among the accessions, the average silica concentration ranged from 120 to 251 mg g(-1). Ample variation was seen within each of the five sub-populations of rice, as well as the 14 geographic regions that the accessions originated from. There was also an effect due to location and accession × location (G × E) interaction demonstrating the importance of assessing silica concentration across multiple environments. Twelve markers on ten chromosomes were significantly associated with hull silica concentration. Six markers (RM5644, RM5371, RM1335, RM283, RM263, and RM178) corroborated quantitative trait locus for silica concentration identified in other mapping studies. Our results provide germplasm and genetic markers that will assist breeding efforts to develop cultivars that have either high or low hull silica concentration. High silica hulls are good raw material for silica based industrial compounds, while low silica hulls are more biodegradable.
... Rapid, micro-methods to estimate plant silicon content by dilute hydrofluoric acid extraction and spectrometric molybdenum method. The method is with slight modifications to Saito [66] and silicon content in xylem sap is determined by molybdenum yellow method. The powdered straw and grain samples were dried in an oven at 65°C for two days prior to analysis. ...
... The powdered straw and grain samples were dried in an oven at 65°C for two days prior to analysis. The sample (0.5 g) was digested in a mixture of 50 mL each of 10 mL of HF (46 %) + 40 ml of double distilled water and allowed for cold digestion overnight [66]. The Si concentration in the digested solution was determined as described below: 0.1 ml of digested aliquot was transferred to a plastic centrifuge tube. ...
Rice is an important cereal crop, is mostly grown as a staple food in developing nations. One of the main causes restricting rice productivity is drought, which has a detrimental effect on global food security. Silicon increases antioxidant activity and lessens plant oxidative damage. In the current study, eight rice cultivars were subjected to foliar silicon spray to evaluate its effectiveness in reducing water stress. The plants were foliar sprayed with silicon under well-watered and drought-stressed circumstances. The collected data showed that drought stress significantly reduced physiological parameters, growth, and yield. In comparison with control, silicon application (T2) has increased LAI by 50.13%, RWC by 0.24%, total dry matter by 18.86%, productive tiller number by 30%, number of panicles m-2 by 26.10%, number of grains panicle-1 by 24.60%, test weight by 29.26% and grain yield by 10.60%; water stress alone (T3) reduced LAI by 38.06%, RWC by 21.02%, total dry matter by 38.88%, productive tiller number by 30%, number of panicles m-2 by 33.45%, number of grains panicle-1 by 42.85%, test weight by 34.87% and grain yield by 40.88%; while silicon + water stress (T4) reduced LAI by 3.41%, RWC by 16.89%, total dry matter by 8.45%, productive tiller number 0.00%, number of panicles m-2 by 13.97%, number of grains panicle-1 by 18.25%, test weight by 24.50% and grain yield by 19.24% only. Overall, silicon application has ameliorated the negative impacts of drought stress on rice and improved the growth, physiological traits and yield under both well-watered and water stress conditions. To increase the quality of the yield and to generate rice cultivars that can withstand drought stress, silicon should be incorporated into breeding programmes.
... Grayish black colored ash was collected and used for all the studies. The quantification of Si present in RHA was carried out by molybdenum yellow method (Saito et al., 2005). ...
... Stem tissues (length of 10 cm from the base of the plant) were sampled from each treatment one day before application of Si (1DBA), seven days after application of treatment (7DAA) and one week after imposition of second dose of imidazole in T4 treatment at booting stage (7DAB). The samples were oven dried at 60°C for 48 h, powdered and used for estimation of biochemical parameters viz., total Si (Saito et al., 2005), total sugars content (Dubois et al., 1956) and total phenol content (Malick and Singh, 1980). ...
... Effect of external application of silicon solubilizers was studied quantitatively by determining silicon content in the xylem sap by the molybdenum yellow method (Satio et al., 2005). Qualitative analysis of silicon or localization of silicon deposition in rice plants was done by transmission electron microscopy (TEM). ...
... (Yoshida, 1965;Ma et al., 2004). These organo-silicon compounds in epidermal cell walls help the rice plants to overcome multiple biotic and abiotic stresses (Luu and Maurel, 2005;Satio et al., 2005). This is evident from the present study where the Si treated plants were able to maintain the chlorophyll content in the aerobic condition. ...
... The powdered ash was used for all the studies. The quantification of silicon present in RHA was carried out by the molybdenum yellow method (Saito et al. 2005). Imidazole (chemical formula: C 3 H 4 N 2 , Mol. ...
... The total amount of Si present in the stems in all the test varieties where treatments were given was estimated by the Molybdenum yellow method (Saito et al. 2005). Silicon was estimated in the stem tissues 1 day before application (1DBA), 7DAA and seven days after booting (7DAB) stage of crop growth. ...
The effect of soil application of rice husk ash (RHA), a cheap renewable source of silicon, and imidazole (a silicon solubilizer and carrier) on yellow stem borer (YSB), Scirpophaga incertulas (Walker), and its damage to rice plants were investigated. Treatments included soil application of RHA (T1), imidazole (T2), RHA + imidazole (applied once at vegetative stage, T3) and RHA + imidazole (applied twice at both vegetative and booting stages of crop growth, T4) with an untreated control (T5). The effect was tested in five varieties, viz., BPT 5204, KRH2, Pusa Basmati 1, MTU1010 and Vandana. All the soil treatments reduced damage by YSB at vegetative and reproductive phases across five varieties as compared to untreated control. Scanning electron micrograph and electron-dispersive X-ray spectrum analysis of stem tissue of rice variety BPT 5204 treated with silicon revealed the enhanced deposition of silicon in cell walls and 2.1- to 5.3-fold increase in silicon content across treatments. Larvae collected from the silicon-treated plants had worn mandibles, and the histological studies showed rupture of the peritrophic membrane, increased vacuolation, disintegration of columnar cells and discharge of cellular contents into the gut lumen due to abrasion of midgut epithelium, as compared to untreated control where the columnar cells and midgut lining were intact. Although all the treatments were effective, T4-imidazole applied twice along with RHA was more effective in reducing YSB damage followed by T3-imidazole applied once with RHA at tillering stage, T2-imidazole alone and T1-RHA in the descending order of efficacy.
... The term covers a range of technologies including pyrolysis, gasification, and combustion which can be configured to produce outputs of heat, electricity, or gaseous or liquid precursors for upgrading to liquid fuels or chemical feedstocks (Figure 1 and Butler et al., 2011; Wang et al., 2011; Brar et al., 2012; Bridgwater, 2012; Solantausta et al., 2012). Thermochemical technologies show great promise for the production of renewable electricity, both in the context of biomass co-firing in existing coal powerplants (Demirba¸sDemirba¸s, 2003b; Baxter, 2005), and for decentralized electrification projects in developing countries (Yin et al., 2002; Hiloidhari and Baruah, 2011; Shackley et al., 2012). Thermochemical produced electricity could help fulfill standards enacted in many US states that require a certain percentage of electricity be produced from renewable sources (Carley, 2009; DOE DSIRE, 2012; EIA, 2012). ...
... Quantitative trait loci (QTL) have been mapped for silica concentration in various tissues (Wu et al., 2006; Dai et al., 2008) and there are hints that some disease resistance genes may actively modify silica levels (Li et al., 2012) and different types of silica deposition may have different roles (Isa et al., 2010). Silica content is estimated in plant tissue by hydrofluoric acid extraction and a molybdenum blue assay (Saito et al., 2005) or by gravimetric techniques (Datnoff et al., 2001). Measurement is also possible with ICP-OES (El-Nashaar et al., 2009 ) and distribution within a tissue can be assessed by X-ray fluorescence spectroscopy (Datnoff et al., 2001). ...
Bioenergy will be one component of a suite of alternatives to fossil fuels. Effective conversion of biomass to energy will require the careful pairing of advanced conversion technologies with biomass feedstocks optimized for the purpose. Lignocellulosic biomass can be converted to useful energy products via two distinct pathways: enzymatic or thermochemical conversion. The thermochemical pathways are reviewed and potential biotechnology or breeding targets to improve feedstocks for pyrolysis, gasification, and combustion are identified. Biomass traits influencing the effectiveness of the thermochemical process (cell wall composition, mineral and moisture content) differ from those important for enzymatic conversion and so properties are discussed in the language of biologists (biochemical analysis) as well as that of engineers (proximate and ultimate analysis). We discuss the genetic control, potential environmental influence, and consequences of modification of these traits. Improving feedstocks for thermochemical conversion can be accomplished by the optimization of lignin levels, and the reduction of ash and moisture content. We suggest that ultimate analysis and associated properties such as H:C, O:C, and heating value might be more amenable than traditional biochemical analysis to the high-throughput necessary for the phenotyping of large plant populations. Expanding our knowledge of these biomass traits will play a critical role in the utilization of biomass for energy production globally, and add to our understanding of how plants tailor their composition with their environment.
... A manual, hand-held rice dehusker was used to dehusk the flled rice grains. Te silicon content from the rice plant parts (root, fag leaf, and husk) was extracted by a diluted hydrogen fuoride solution as described by Saito et al. [31] after grinding into a fne powder with a mill ball grinder (MM 200, Retsch GmbH, Haan, Germany). Te Si in the extract was measured by the molybdenum yellow method at a wavelength of 400 nm [32]. ...
Rice husk biochar (RHB) is a potential source of available silicon in paddy soil and an ecologically responsive soil amendment for sustainable rice production. The study tested the influence of RHB application methods on rice growth, rice yield, and silicon dynamics in sandy loam soil in a pot experiment. RHB was applied at 5 tons ha⁻¹ as a localized-spot-application (LSA) or top-mixed-application (TMA) with the soil at the upper 7 cm or whole-mixed-application (WMA) within 20 cm of the soil column and at 10 tons ha⁻¹ in the TMA and WMA methods and was compared with a control (CTRL) without biochar. Seedlings of the Koshihikari rice variety were transplanted in each pot, and all treatments were replicated thrice. Compared to the CTRL, the LSA and TMA methods did not influence the mean porewater silicon concentration at the vegetative and reproductive stages. However, the WMA method applied at 5 tons ha⁻¹ increased (p<0.05) the mean porewater silicon concentration by 12.3 and 39.5% at the vegetative and reproductive stages, respectively, while at 10 tons ha⁻¹, the respective increase was by 26.1 and 32.7%. All biochar application methods at the 5 tons ha⁻¹ rate increased the rice grain yield (p<0.05) by 21.2% (LSA), 11.3% (TMA), and 47.2% (WMA) compared to the CTRL. Conversely, at 10 tons ha⁻¹, the yield was reduced by 18% in the TMA method, attributable to the immobilization of nitrogen and adsorption of nutrients to biochar surfaces. Our results proved that the choice of biochar application method and rate of application significantly influenced the dissolution of silicon in the porewater, leading to a higher silicon uptake and consequently a higher grain yield. This study provides valuable insights for agricultural practices aiming to enhance silicon dynamics in paddy soil and sustainable rice yield using RHB.
... Eliott et al., 1988;Carnelli et al., 2001). This method has recently been compared with diges- tion in hydrofluoric acid (Saito et al., 2005), and there was excellent agreement between the two methods (R 2 = 0.98). Samples were dried in an oven at 80°C, weighed, and ashed in a muffle furnace at 450°C overnight. ...
Les travaux présentés pour cette HDR s'intéressent à l’identification et à la modélisation des mécanismes et processus contrôlant la composition chimique de l’eau du sol. Les situations étudiées ont été celles de sols forestiers acides sous climat tempéré, situés en moyenne montagne (Rhône, Nièvre). Les éléments chimiques qui ont été particulièrement étudiés de ce fait sont l’aluminium (Al) et le silicium (Si). Le carbone organique dissout (COD) a également été l’objet de travaux, en particulier sa fonction de complexation des cations (Al3+) et dans une moindre mesure son influence sur la cinétique d’altération (Si). Les originalités de ces travaux de recherche se situent dans :
• l’utilisation d’une démarche de modélisation « mono-processus », qui s’est manifestée par l’utilisation de modèles géochimiques et d’une modélisation de la dynamique de l’eau et a notamment abouti à préciser les mécanismes et processus contrôlant les dynamiques de Al, Si et de l’eau dans le sol ;
• l’amélioration et/ou le développement de techniques expérimentales permettant une étude plus fine du fonctionnement du système, en particulier concernant les interactions entre Al et la matière organique du sol (via les extractions CuCl2), les effets du temps de résidence de l’eau (i.e. taille des pores) sur les processus contrôlant Al (via les mesures de spéciation aluminique) et la qualité et la quantité du COD (via la spectrophotométrie d’absorbance) ;
• la réalisation de développements numériques pour la mise à niveau d’un modèle de transport-réactif (MIN3P). Leur priorité a été dictée par les résultats des modélisations « mono-processus » et ceux de premières modélisations couplées de la concentration de Si dans les eaux capillaires du sol.
Ce travail a fourni un premier modèle permettant la résolution couplée des processus de transfert (eau, solutés, gaz), des processus géochimiques (spéciation, adsorption, dissolution/précipitation etc.) et d’un certain nombre de processus biologiques (absorption racinaire, transpiration, transformation microbiologiques) dans le temps et l’espace (1-D à 3-D).
Pour les années à venir, mes travaux d’encadrement et de recherche auront pour objectifs: (i) d’améliorer la manière dont les processus biologiques sont pris en compte dans le modèle, en se focalisant sur l’étude des interactions sol-plante dans la rhizosphère en relation avec les cycle du phosphore, de l’azote et du carbone ; (ii) de rendre disponible cet outil au plus grand nombre, par la réalisation de formations, de cours, appuyés par le développement d’une interface homme-machine voire d’une véritable plate-forme de modélisation.
... Nitrogen, P, and K concentrations in the straw were measured by standard methods as described by Coung et al. 44 . The Si concentrations in rice straw were measured by the dilute hydrofluoric acid extraction and spectrometric molybdenum method 45 . ...
With the increase in iron/steel production, the higher volume of by-products (slag) generated necessitates its efficient recycling. Because the Linz-Donawitz (LD) slag is rich in silicon (Si) and other fertilizer components, we aim to evaluate the impact of the LD slag amendment on soil quality (by measuring soil physicochemical and biological properties), plant nutrient uptake, and strengthens correlations between nutrient uptake and soil bacterial communities. We used 16 S rRNA illumine sequencing to study soil bacterial community and APIZYM assay to study soil enzymes involved in C, N, and P cycling. The LD slag was applied at 2 Mg ha⁻¹ to Japonica and Indica rice cultivated under flooded conditions. The LD slag amendment significantly improved soil pH, plant photosynthesis, soil nutrient availability, and the crop yield, irrespective of cultivars. It significantly increased N, P, and Si uptake of rice straw. The slag amendment enhanced soil microbial biomass, soil enzyme activities and enriched certain bacterial taxa featuring copiotrophic lifestyles and having the potential role for ecosystem services provided to the benefit of the plant. The study evidenced that the short-term LD slag amendment in rice cropping systems is useful to improve soil physicochemical and biological status, and the crop yield.
... Si concentration in the rice samples and the CRH used were determined using gravimetric analysis after wet ashing as described by Saito et al. (2005). Data on temperatures and rainfall during rice cultivation were collected from a meteorological station of the Japan Metrological Agency located within the same city as the experimental site. ...
Silicon (Si) application is considered one means of cultural management having beneficial effects on the control of rice diseases. Carbonized rice husk (CRH)—a cost-effective biochar derived from a by-product of rice production—has been proposed as Si fertilizer as well as for promoting carbon sequestration in soil. This experiment was conducted in an irrigated paddy field in Tsukuba, Japan, to evaluate the potential effects of CRH application on sheath blight among four treatments (two levels of CRH application at 1.5 and 3.0 t ha－1, a spray of fungicide with flutolanil, and the control without any application). The results demonstrated that CRH at 3.0 t ha－1 increased rice Si content by 9% and regulated sheath blight development in the plant community to some extent after inoculation, whereas CRH at 1.5 t ha－1 showed no clear impacts on rice plants and fungal pathogen development. The fungicide application with flutolanil had the lowest rate of sheath blight development, but did not affect rice Si content. The results suggest that CRH application at 3.0 t ha－1 or more could be an option for integrated management of sheath blight without negative effects on rice yield.
... Total silicon (TSi) in RS and CDC was extracted in 1.5 M hydrofluoric acid-0.6 M hydrochloric acid solution, and the Si concentration was measured by using the molybdenum yellow method ( Saito et al. 2005). ...
After the rice harvest in Japan, rice straw (RS) is usually cut by combine harvester and incorporated into the soil to improve its fertility. In mixed crop–livestock systems, however, RS is collected and used as livestock feed, and cow dung compost (CDC) is then applied to the soil. This system utilizes the residual organic matter from both rice production and livestock husbandry to make each product. CDC application is also considered to improve the fertility of paddy soil. However, the nutrient input from CDC and the effect of CDC application on soil fertility vary among regions and/or soil types. We compared soil fertility between RS application (RS treatment, avg. 32 years) and RS removal plus CDC application (CDC treatment, avg. 21 years) in 79 paddy fields in Mamurogawa town, Yamagata Prefecture, a cold temperate region of Japan, and measured the nutrient contents in the applied RS and CDC. The total C content of RS was significantly higher than that of CDC, whereas the N, P, K, and Si contents of CDC were significantly higher than those of RS. However, there was no significant difference in paddy soil fertility – as measured by soil organic C, total N, CEC, available N, P, and Si, exchangeable K, Ca, and Mg, base saturation percentage, pH, and bulk density – between the treatments. The soil fertility of most fields was adequate by RS or CDC treatment. Thus, leaving RS in paddy fields or removing it and then adding CDC to the paddy fields has a similar effect in maintaining adequate soil fertility for single rice production or rice–livestock production systems.
... The total N concentration of the rice straw was determined using the same method as that used for soil analysis. The Si concentration of the straw, RC, and RH was determined using gravimetric analysis, as described by Saito et al. (2005). The rice straw from the 2nd year's harvest, RC, and RH were digested in a mixture of sulfuric acid (H 2 SO 4 ) and hydrogen peroxide (H 2 O 2 ) in order to measure potassium (K), calcium (Ca), and magnesium (Mg) concentrations using an atomic absorption photometer (Z-2300; Hitachi High-Technologies Corp., Tokyo, Japan). ...
Rice husk charcoal (RC) produced from the pyrolysis of rice husk (RH) can be one of the cost-effective biochars for use in rice-based farming systems. This study investigated changes in rice yield and soil carbon sequestration over three years of RC application to an Andosol paddy field. The treatments were RC application at 0.02, 0.2, and 2 kg m⁻² (RC0.02, RC0.2, and RC2, respectively), RH application at 0.2 kg m⁻² (RH0.2), and a control with no RC or RH application (CONT). The results showed that RC2 increased culm length by 4% and straw weight by 14% on average over the three years. These increases in plant growth coincided with a higher level of silicon uptake by the rice plants, although they did not significantly affect grain yield. The soil carbon content was progressively increased by RC2 over the three years, whereas it was not significantly affected by RC0.02 or RC0.2. A considerable amount (>72%) of the applied carbon with RC2 remained in the soil by taking account of its downward movement below the 10 cm layer of the paddy field after three consecutive years of RC application. We conclude that rice husk charcoal application to Andosol paddy fields is an effective option for increasing carbon sequestration. Furthermore, the increase in silicon uptake by rice plants suggests that rice husk charcoal can also be functioning as a silicon fertilizer.
... Determination of the Si content in rice plants was accord- ing to Saito et al. (2005). At harvest, the number of tillers for 30 plants chosen randomly was counted, and rice shoots and ears from six plants that had an average number of tillers and were > 5 m apart from each other were collected. ...
To evaluate the influence of reducible iron (Fe) on the availability of silicon (Si) by rice (Oryza sativa L.), (1) relationships between the available Si content in soil (successive water elution method), the Si content in rice shoots and ears, and the levels of oxalate-extractable Si (Sio), Fe (Feo), and aluminum (Alo) in 13 paddy soils were analyzed; and (2) the Si concentration in soil solution following sequential flooding/drainage was traced in soil microcosm experiments. Both the available Si and Feo contents in soil were positively correlated with the Si content in rice shoots, while a similar correlation was not observed between the available Si, Sio and Feo. These results suggest that the Sio adsorbed to Feo is not necessary to determine the pool size of the Si available to plants. In microcosm experiments, intermittent drainages decreased Fe concentration in soil solutions by 83–96% compared to that in the continuous flooding treatment. The oxidation of Fe²⁺ resulted in the co-precipitation of Si with Fe. However, the decrease of Si in a soil solution following drainage was 22% or less, which were smaller than the values observed when solutions containing various ratios of metasilicic acid and Fe²⁺ were mixed under oxic conditions (24–97%). In addition, as the Si concentrations in soil solutions in the intermittent flooding treatment increased to the levels similar to those in the continuous flooding treatment after re-flooding before Fe was re-reduced, the effect of reduction/oxidation of Fe on the dissolved Si concentrations was small. Thus, the reducible Fe is not a major factor in rice-available Si in paddy soil.
... The total N and C contents of the rice plant were determined using the same method as that used for soil analysis. The Si content in the straw sample, as well as RC and RH, was determined using gravimetric analysis as described by Saito et al. (2005). The N and Si uptakes and C assimilation by the rice plants were calculated by multiplying the nutrient concentrations and the rice panicle or straw weight for each plant. ...
Biochar application is an effective option for promoting soil carbon sequestration. Rice husk charcoal (RC) produced from pyrolysis of rice husk (RH) is characterized by a higher silicon content as compared to wood-derived biochar. A study was conducted using pots to evaluate the short-term effects of RC application at 0, 0.4, 2.0, 4.0, 20.0, and 40.0 g pot⁻¹ (CONT, RC0.4, RC2, RC4, RC20, and RC40, respectively), or RH application at 4.0 g pot⁻¹ (RH4) on rice yield, methane (CH4) emission, and soil carbon sequestration in an Andosol paddy soil. The results showed that the significant increase in brown rice yield with RC40 was attributed to increases in the grain number and percentage of ripened grains. Plants treated with RC20 or RC40 absorbed greater amounts of silicon than those treated with lower RC rates. RC application did not significantly increase CH4 emission. The soil carbon content after rice cultivation increased in proportion to the RC application rate. The balance between cumulative CH4 emission and soil carbon sequestration, based on the 100-year global warming potential, suggested that RC40 served as CO2-equivalent sink. No differences were observed in the measured parameters between RH4 and RC4. These findings suggest that the higher rates of RC application in the RC20 and RC40 treatments function as a silicon fertilizer while promoting soil carbon sequestration.
... The silicate content was analyzed by colorimetric method after being decomposed by HCl and HF. 17) For the statistical analysis, the software called "The R Project for Statistical Computing" was used and a multivariate analysis for the average value of each plot was conducted by Tukey method. 18) In each result, standard error is shown and the significant difference was determined by the statistically significant at the 5 percent level. ...
The great earthquake of 2011 triggered a tsunami that damaged large areas of paddy fields in northeastern Japan. In an effort to address the salt damage, supplementation of Ca-containing materials to exchange Na adsorbed on soil surface has been recommended. In addition, Si has also been shown to enhance paddy growth. Steelmaking slag, which contains a water-soluble solid solution phase of 2CaO center dot SiO2, can supply Ca and Si for soil remediation. In this study, the dissolution behaviors of nutrient elements from fertilizer made of steelmaking slag were investigated using the column test. In addition, crop cultivation experiments were also conducted using tsunami-damaged paddy fields. In column test, Ca content in soil solution increased by the application of fertilizer made of slag, but the Na content did not change significantly. These trends were also observed in the pore water of the actual paddy in crop cultivation experiments. In addition, the incremental trend of silicate content in the pore water by the application of fertilizer made of slag was more apparent than that in the column test. Paddy growth was enhanced and the yield of brown rice was increased by the application of fertilizer made of slag. In conclusion, the fertilizer made of steelmaking slag has the following three effects: (1) mitigating the damage caused by the Na ion through the supplementation of Ca, (2) enhancing the mineralization of soil N by increasing the pH, and (3) accelerating photosynthesis by the supplementation of silicate.
... (22 o C) until analyzed. Silica was determined using the molybdenum yellow method described by Saito et al. (2005) and Bryant et al. (2011). ...
... Procedures for sample preparation (e) Tiron extraction method (Guntzer et al. 2010 ) 1. Weigh 0.5 g of plant sample milled to pass a 20-mesh screen into a polypropylene tube 2. Add 30 mL of a 0.1 M Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt, C 6 H 4 Na 2 O 8 S 2 ) solution buffered at pH 10.5 to the plant sample in the tube 3. Place the tube in a water bath at 85 °C and horizontally shake for 1 h with the cap loosely closed to prevent evaporation 4. Cool the tube 5. Take 10 mL of the extraction solution and add 10 mL of 30 % H 2 O 2 to destroy Tiron to reduce the matrix effect during ICP-OES analysis 6. Shake the new solution at 85 °C in the water bath for one more hour until it was colourless 7. Cool and fi lter the solution at a 0.2-μm cellulose nitrate membrane before ICP-OES analysis (f) Hydrofl uoric acid extraction method (Saito et al. 2005 ) 1. Weigh 500 mg of dried and milled plant samples into a 50-mL polypropylene or polyethylene bottle 2. Add 10 mL of the extraction solution (1.5 M HF + 0.6 M HCl) 3. Stopper the bottle, stir the content of the bottle to immerse the plant tissues in the HF solution, and let it stand for 30 min at 30 °C (1 h at 18 °C) with occasional stirring (roughly every 10 min) 4. Add 40 mL of distilled water, stir to homogenize the content, and let plant materials settle for 20 min 5. Take the aliquot (0.1 mL) of the clear supernatant for determination of the dissolved Si ...
The beneficial effects of silicon (Si) at preventing plant diseases have been known for many decades, and the list of plant–pathogen interactions influenced by Si keeps expanding. However, it is quite evident that the prophylactic properties of Si will vary greatly depending on the plant and the pathogen. The recent discovery of Si-specific transporters in rice roots has been instrumental in identifying plants that possessed such transporters and were thus genetically disposed to accumulate Si in their tissues and benefit more from Si amendments. For the same reason, soil applications of Si lead to significantly more Si accumulation in plant tissues than foliar applications and are likely to yield better results. An issue that has received less attention is the specificity of Si with respect to plant pathogens. Based on the literature, there is an overwhelming abundance of reports describing the positive effects of Si against fungal pathogens compared to bacteria, virus or nematodes. Among fungal pathogens, those described as biotrophic or hemibiotrophic, such as powdery mildews and Magnaporthe grisea, appear to be better controlled by Si. The reasons behind this apparent specificity are still unknown but recent data suggest that Si would interfere with effector proteins released by those pathogens, thus allowing the plant to mount better defence reactions. Our recent progress at understanding Si properties will contribute to optimizing its use in the context of sustainable agriculture.
... Procedures for sample preparation (e) Tiron extraction method (Guntzer et al. 2010 ) 1. Weigh 0.5 g of plant sample milled to pass a 20-mesh screen into a polypropylene tube 2. Add 30 mL of a 0.1 M Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt, C 6 H 4 Na 2 O 8 S 2 ) solution buffered at pH 10.5 to the plant sample in the tube 3. Place the tube in a water bath at 85 °C and horizontally shake for 1 h with the cap loosely closed to prevent evaporation 4. Cool the tube 5. Take 10 mL of the extraction solution and add 10 mL of 30 % H 2 O 2 to destroy Tiron to reduce the matrix effect during ICP-OES analysis 6. Shake the new solution at 85 °C in the water bath for one more hour until it was colourless 7. Cool and fi lter the solution at a 0.2-μm cellulose nitrate membrane before ICP-OES analysis (f) Hydrofl uoric acid extraction method (Saito et al. 2005 ) 1. Weigh 500 mg of dried and milled plant samples into a 50-mL polypropylene or polyethylene bottle 2. Add 10 mL of the extraction solution (1.5 M HF + 0.6 M HCl) 3. Stopper the bottle, stir the content of the bottle to immerse the plant tissues in the HF solution, and let it stand for 30 min at 30 °C (1 h at 18 °C) with occasional stirring (roughly every 10 min) 4. Add 40 mL of distilled water, stir to homogenize the content, and let plant materials settle for 20 min 5. Take the aliquot (0.1 mL) of the clear supernatant for determination of the dissolved Si ...
The first soil testing of plant-available silicon (Si) was not conducted until 1898 on Hawaiian soils. However, numerous procedures have since been developed for determination of Si content in a wide variety of materials including soils, plants and fertilizers. This chapter reviews current analytical procedures that are widely used for analysis of both total Si in soils, plants and fertilizers and plant-available Si in soils and fertilizers.
... Eliott et al., 1988;Carnelli et al., 2001). This method has recently been compared with diges-tion in hydrofluoric acid (Saito et al., 2005), and there was excellent agreement between the two methods (R 2 = 0.98). Samples were dried in an oven at 80°C, weighed, and ashed in a muffle furnace at 450°C overnight. ...
We investigated the biogeochemical cycling of Si in an acidic brown soil covered by a coniferous forest (Douglas fir) based on a comprehensive data set and reactive transport modelling. Both published and original data enable us to make up a conceptual model on which the development of a numerical model is based. We modified the reactive transport code MIN3P, which solves thermodynamic and kinetic reactions coupled with vadose zone flow and solute transport. Simulations were performed for a one-dimensional heterogeneous soil profile and were constrained by observed data including daily soil temperature, plant transpiration, throughfall, and dissolved Si in solutions collected beneath the organic layer. Reactive transport modelling was first used to test the validity of the hypothesis that a dynamic balance between Si uptake by plants and release by weathering controls aqueous Si-concentrations. We were able to calibrate the model quite accurately by stepwise adjustment of the relevant parameters. The capability of the model to predict Si-concentrations was good. Mass balance calculations indicate that only 40% of the biogeochemical cycle of Si is controlled by weathering and that about 60% of Si-cycling is related to biological processes (i.e. Si uptake by plants and dissolution of biogenic Si). Such a large contribution of biological processes was not anticipated considering the temperate climate regime, but may be explained by the high biomass productivity of the planted coniferous species. The large contribution of passive Si-uptake by vegetation permits the conservation of seasonal concentration variations caused by temperature-induced weathering, although the modelling suggests that the latter process was of lesser importance relative to biological Si-cycling.
... Eliott et al., 1988;Carnelli et al., 2001). This method has recently been compared with diges-tion in hydrofluoric acid (Saito et al., 2005), and there was excellent agreement between the two methods (R 2 = 0.98). Samples were dried in an oven at 80°C, weighed, and ashed in a muffle furnace at 450°C overnight. ...
We investigated the biogeochemical cycling of silicon (Si) in an acidic brown soil covered by a coniferous forest (Douglas fir). Based on published and original data, we constructed a conceptual model and used a modified version of the reactive transport code MIN3P for model testing and quantification purposes. The model was first calibrated and further validated with respect to biomass data and Si-concentrations in capillary solutions, which were collected monthly over several years by means of suction-cup lysimeters placed at different soil depths.
Following sensitivity tests, the model was calibrated quite accurately (limited to a 10% concentration error) by the adjustment of kinetic constants, longitudinal dispersion, and apparent activation energy for K-feldspar dissolution. Calibrated parameter values were constrained by ranges reported in the literature, when available. Mass balance calculations indicate that an average of 60% of the biogeochemical cycle of Si was controlled by biological processes (i.e. Si-uptake and dissolution of phytoliths). Sensitivity analyses suggest that no more than 55% of the Si-cycle is controlled by weathering of primary silicates. Such a large contribution of biological turnover to Si-cycling may be explained by the combined effects of a relatively large Si-content in the litter fall (i.e. specifically in the needles) and high biomass productivity of the coniferous species considered. In addition to potential implications for the global Si cycle, this investigation raises several fundamental questions concerning the nature of Si-uptake mechanisms and physiological use of Si by trees in natural systems.
Le colza (Brassica napus L.) est une plante de grande culture nécessitant de forts intrants azotés et présentant une faible Efficience d’Utilisation de l’Azote (EUA) principalement due à une faible efficience de remobilisation cet élément durant la sénescence foliaire. Actuellement, une amélioration du bilan agroenvironnemental de la culture du colza, nécessite la mise au point de nouvelles pratiques culturales permettant de maintenir (voire d’améliorer) son rendement tout en limitant les doses d’intrants azotés. Dans ce contexte, l’utilisation d’éléments bénéfiques tels que le silicium (Si) dont les effets ont déjà été démontrés dans la tolérance à certains stress nutritionnels (phosphore et potassium) constitue une alternative intéressante. Les objectifs de cette étude visent à étudier l’effet du Si (i) sur la progression de la sénescence foliaire, l’absorption et la remobilisation de l’azote et les performances agronomiques du colza cultivé en hydroponie ou en conditions de plein champ et soumis ou non à une limitation ou une privation en azote. Nos travaux montrent, qu’en dépit de son caractère faiblement accumulateur en Si, le colza absorbe le Si puis le stocke essentiellement au niveau racinaire. Par ailleurs, un apport de Si de courte durée (7 jours ; 1,7 mM) à des jeunes plantes privées en azote provoque un retard de sénescence des feuilles matures associé un maintien de leur teneur en chlorophylles et de leur activité photosynthétique. De plus, au champ, un apport de Si (12 kg ha-1) à des plantes cultivées avec 160 kg N ha-1 s’accompagne d’une augmentation du rendement grainier (+4,2 quintaux ha-1). L'utilisation de l’indice agronomique «Agronomic Nitrogen Recovery (ANR)» combinée à l’étude de l’expression de gènes codant des transporteurs d’azote (BnaNRT1.1, BnaNRT2.1, BnaAMT1.1) montrent que le Si agit notamment en stimulant l’absorption de l’azote chez le colza. Enfin, une analyse différentielle par RNAseq des transcriptomes racinaires de jeunes plantes traitées ou non avec du Si pendant une courte durée (7 jours ; 1,7 mM), montre que le Si module l’expression de 1079 gènes, 334 étant induits et 745 réprimés. Ce résultat indique qu’en plus de son rôle mécanique, le Si exerce également un rôle signalétique.
In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus. Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca.
A very limited number of methods for the determination of silicon are used. The classic analytical methods (gravimetric, photometric) and modern methods ICP-MS and ICP-AES are applied for the determination of silicon in plants, whereas the latter has an advantage because the sample preparation is not necessary. However, the reliability of the results obtained by ICP-AES is disputable. Conventional methods of sample preparation for silicon determination are time-consuming and difficult to perform; therefore, there is a critical need for development of more effective sample preparation procedures. Herein, we report the improved method of sample preparation for determining of silicon in plant materials. The method includes dry ashing, followed by oxidative degradation in HClO4 and dissolution of formed silica in a mixture solution of potassium hydroxide and NaEDTA. Proposed method of sample preparation is more reliable and rapid (40 min). We employ the capillary electrophoresis (CE) for determination of silicon in plants, which to the best of our knowledge has not been done before. The dynamic concentration range of determination is 0.05–2 mg/l, detection limit - 0.02 mg/l. Analysis of different plant samples showed that the method is suitable for determination of silicon in plant materials down to trace amounts (0.1 mg/g) with satisfactory validity. Overall analysis time is 50–52 min.
We have developed acidified porous hydrate calcium silicates (APS) with the final pH of 3.0, 3.9 or 5.3 by adding of sulfuric acid to porous hydrate calcium silicate material. In this study, the effects of APS at various pHs applied to nursery bed soil on the growth of rice seedlings were investigated to determine the optimal pH of APS as an ameliorant for raising healthy rice seedlings. APS at pH 3.0 decreased the plant length of the seedlings by 10 to 15% compared to that at other pHs. Treatment with the APS at pH 3.0 decreased both shoot dry weight, and the ratio of shoot dry weight to the plant length of the seedlings. The root dry weight was the lightest in the seedlings treated with APS at pH 3.0; these root tissues, especially exodermis, sclerenchyma and endodermis, were intensively stained with hematoxylin and evans blue, showing the symptom of Al toxicity.
We conducted a 12-year field experiment to study the combined effects of rice straw compost and chemical fertilizer application on a double rice cropping system in the Mekong Delta, Vietnam and established 7 treatments using a randomized block design with 3 replications. We calculated the yields of treatments relative to those of conventionally fertilized plots (i.e. with no added rice straw compost), and analyzed their annual trends. In the plots with rice straw compost, we observed a positive trend over 12 continuous wet cropping seasons. In comparison with conventional fertilization, the application of rice straw compost with reduced chemical fertilizer can maintain rice productivity over a longer period. We analyzed the nutrient status of the rice straw at harvest over 4 cropping seasons and observed that the Si concentration of the rice straw in conventionally fertilized plots was significantly lower than that in the plots where rice straw compost was applied. The N, P and Mg concentrations of the rice straw increased with the fertilizer application rate, while the concentrations of K, Ca, Mn, Fe, Zn, and Cu did not differ significantly among treatments. Our results suggest that continuous removal of rice straw may reduce the Si availability in soil, thereby decreasing rice productivity. In addition, we verified that rice straw compost can be an effective source of silicon for paddy rice.
Purpose
For conserving irrigation water for rice (Oryza sativa L.) cultivation, the repeated draining/flooding with minimal amounts of water (water conservative irrigation (WCI)) is recommended. WCI changes the reductive/oxidative state of iron (Fe), which may, in turn, change the dissolved silicon (Si) concentration in a soil solution. The purpose of the present study was to confirm the influence of WCI on the availability of Si by rice.
Materials and methods
Seasonal variations in the soil solution Si concentration and the amount of Si absorbed by rice were compared between WCI and control plots in two fields. A microcosm experiment was also conducted to examine the effect of reduction/oxidation of Fe on the soil solution Si concentration.
Results and discussion
In the field, the seasonal variation pattern of Fe in a soil solution differed between WCI and control plots, but the Si level did not, which was maintained at low levels during the WCI period probably due to active uptake by rice. The amount of Si absorbed by rice was similar between the two treatments. In the microcosm experiment, the soil solution concentration of Si decreased by 47 % along with the oxidation of Fe2+ in the first drainage. However, only the Fe2+ concentration was changed with further repetition of drainage and flooding, and total loss of Si from the soil solution due to intermittent flooding corresponded to 1 % of the Si absorbed by the rice in the field.
Conclusions
Although WCI can change the seasonal variation in the soil solution Si concentration, its effect on the Si uptake by rice was insignificant.
An understanding of the spatial variation in soil fertility is fundamental for extending rice cultivation and developing appropriate management practices in currently under-utilized floodplain ecosystem of West Africa. The spatial patterns in the soil total carbon (TC) contents were analyzed using a Quickbird imagery, a global digital elevation model (ASTER-GDEM) and ArcView GIS functions for a White Volta floodplain of northern Ghana. An irrigated pot experiment was then conducted to relate rice biomass production to the spatial TC distribution and to identify deficient nutrients using different fertilizer treatments.
an improved analytical procedure has been described for the spectrophotometric determination of colloidal silica in leaching solution by means of adding fluoride to convert colloidal silica into reactive silica. The method is a variation of the classical molybdenum blue method, and has determination of optimal wavelength, temperature, ratio of H3BO3/ NH4F, pH and ammonium molybdate in the colorimetric process, and pH need to be fairly strictly controlled especially. The linear equation is established as: C=3.15956A-0.51912, R is more than 0.9992. Its feasibility and reproducibility has been confirmed by ICP-OES, the average relative error is 1.5%. The detection scope of silicon concentration extends almost 1000 times higher in leaching solution, so method in this paper can be used to detect the leaching samples of high silica concentration.
The noctuid stem borer Busseola fusca is an important pest of maize and sorghum in Sub-Saharan Africa. The presence of this species occurred mostly on cultivated than on wild habitats. Busseola fusca is oligophagous having a narrow range of a wild grass species. This might be due, in part, to differences in silicon (Si) content in plant tissues between cultivated and wild grasses. In the present study, we have tested this hypothesis by studying the survival and the relative growth rate (RGR) expressed as daily weight gains of B. fusca larvae on maize and six wild host plants, mostly present in the natural habitat where B. fusca occurred, and correlated with their Si contents. Survival and RGR of B. fusca larvae were considerably higher on maize and wild sorghum than on the other grass species, and they were negatively related to plant Si content. This was corroborated with results on RGR from artificial diets amended with increasing levels of Si. In addition, if Si was added to maize growing substrate B. fusca larval growth was significantly reduced confirming the involvement of Si in B. fusca larvae - Poaceae interactions. The results provide insight into the possible mechanisms of oligophagy of B. fusca and provide a correlative support for a physical role of plant endogenous Si in impeding feeding of B. fusca larvae.
Rice (Oryza sativa) seedlings were grown in the presence of 5 mM orthosilicic acid (H 4SiO 4, IUPAC name: tetrahydroxyl silane). More than 80% of silicon absorbed in the rice was localized in the alcohol-insoluble residues (AIR) fractions. AIR refers to cell wall materials in the text. Driselase (commercial cell wall hydrolyzing enzyme preparation) released 3% of silicon present in the rice AIR into water-soluble fractions. Size-exclusion high performance liquid chromatography/inductively coupled plasma atomic emission spectroscopy (HPLC/ICP-AES) showed that an aqueous silicon-containing substance with high molecular weight was present in the water-soluble fractions. The compounds were stable at pH 6.5, while commercial silica sols which were stable at pH 9.0 were insoluble at the neutral pH. The stability in neutral pH may be due to the presence of a complex of polysaccharide and protein in the molecule. These results imply that silica-containing macromolecules exist in rice cell walls.
The effects of silicon (Si) supply (0, 0.1, 0.5, 1.5, 3.0, and 5.0 mM Si) on maize seedling growth, Si and Cd accumulation, and thiol peptide synthesis under Cd stress conditions were studied. The addition of Si to the growth medium resulted in the significantly higher Si accumulation in plant tissues. The average values of growth parameters (root and shoot fresh weights and root net elongation rates) showed a beneficial role of Si on growth of non-Cd-treated plants, while there was no evidence that silicon mitigated Cd toxicity in maize seedlings. Cadmium exposure depressed plant growth and induced phytochelatin (PC) synthesis. The accumulation of Cd and PCs in roots significantly decreased with increasing Si concentrations in the nutrient solution; however, their accumulation in shoots was not changed in the presence of Si.
Slag silicate fertilizer (SSF) is applied to paddy fields with different soil chemical properties to increase silicon (Si) concentration in rice (Oryza sativa L.) plants. However, the effects of soil chemical properties on Si availability of SSF to rice Si uptake is poorly understood. To investigate the relationships between chemical properties of soils and the effects of SSF application on the Si concentration in rice plants, a field experiment was conducted in 2007 and 2008 at 18 paddy fields on the Shounai Plain, Yamagata, Japan. Two treatments were implemented: SSF applied at 1.5 t ha−1 and a no-SSF control. The Si concentrations of rice tissues were measured at the tillering and ripening stages. The difference in the Si concentrations of rice tissues between treatments (ΔSi concentration) was used to evaluate the effect of SSF. The Si concentrations in the shoots and aboveground parts of the rice plants were significantly increased by the SSF application in six or more of the fields at the two growth stages, whereas the Si concentrations in the panicles of the rice plants at the ripening stage were not increased significantly in most fields. Results of two-way analysis of variance evidenced a significant effect of field on the ΔSi concentrations in the shoots and aboveground parts at both growth stages. Furthermore, the ΔSi concentrations in the same rice plant tissues and at the same growth stages in the first year and in the second year were found to be positively correlated. These results indicate that the effect of SSF on the Si concentration in shoots and aboveground parts of rice plants varies from field to field. The ΔSi concentrations in shoots and aboveground plant parts at both growth stages were also found to be negatively correlated with soil chemical properties, i.e., available Si, Si adsorption capacity, contents of Si adsorbents (acid oxalate-extractable iron and manganese) and the pH under flooded soil conditions. These findings imply that those soil chemical properties of paddy fields should be taken into account for better prediction of ΔSi concentration of rice plants.
Silicon (Si)-mediated alleviation of Cr(VI) toxicity was examined in wheat seedlings using an
in vivo approach that involves chlorophyll fluorescence, induced breakdown spectroscopy (LIBS) and
anatomical changes. Exposure to Cr(VI) significantly reduced the growth and photosynthetic activities
(chlorophyll fluorescence) in wheat which was accompanied by remarkable accumulation of this
element in tissues. However, addition of Si to the growth medium alleviated the effects of Cr(VI). The
LIBS spectra were used as a fingerprint of the elemental compositions in wheat seedlings, which
showed a reduction in Cr accumulation following Si addition. Nutrient element levels (Ca, Mg, K and
Na) declined in wheat following the addition of Cr (VI), as recorded by LIBS and inductively coupled
plasma atomic emission spectroscopy (ICAP-AES). However, addition of Si along with Cr(VI) increased
the contents of nutrient elements in wheat. LIBS, ICAP-AES and AAS showed a similar distribution
pattern of elements measured in wheat. Anatomical observations of leaf and root revealed that Cr(VI)
affected internal structures while Si played a role in protection from toxic effects. The results showed
the suitability of chlorophyll fluorescence as a parameter and appropriateness of LIBS technique and
anatomical procedures to elucidate Si-mediated alleviation of Cr(VI) toxicity. Furthermore, our results
suggest that the measured parameters and techniques can be used non-invasively for monitoring the
growth of crops under different environmental conditions.
Efforts to minimize water use in rice cultivation and stress tolerance are important in the present climate change scenario. Silica solubilizers might help in understanding the tolerance of plants to water deficit conditions or aerobic conditions. Rice cultivation in combination with silica was applied in the form of fertilizers (sodium silicate) and solubilizers (Imidazole and glycine) was studied in experimental farm and also in farmer's field. The varieties used were ‘KrishnaHamsa' (KH), ‘Rasi', ‘Jaya', hybrids ‘PA-6201' and ‘PHB-71' under aerobic conditions both in wet (Kharif) and dry (rabi) seasons. Transmission electron microscopy in this study provided evidence that silicon was deposited in the epidermal cell wall and the intercellular space of the silicon-treated rice leaves. The epidermal cell wall accumulation was absent in the control plants. Genotypic variation and treatment influences were observed for relative water content and cell membrane stability. Among the different rice cultivars ‘Rasi' followed by ‘PHB-71' and PA- 6201, were able to maintain cell membrane stability and chlorophyll content. Leaf rolling, chlorophyll, relative water contents, and dark adapted chlorophyll fluorescence were superior under aerobic conditions with application of solubilizers. However, significant differences in stomatal conductance were seen between seasons and genotypes. The silicon treated plants were able to maintain similar yields under aerobic conditions also as that of irrigated controls.
Rice is a specific silica-accumulator among higher plants. The Si in rice enhances resistance to biotic and abiotic stresses. The booming demand for rice in Sub-Saharan Africa (SSA) requires rapid increases in rice production, and hence more Si supply will be needed from soils, irrigation water, and external inputs. However, the current Si-nutrient status of rice plants and relevant factors has been so far paid little attention in the region. Therefore, an extensive survey was conducted for evaluating variability of Si concentration in rice straw in relation to soil properties, fertilizer management practices, and rice-growing environments across a wide range of local farmers’ fields in SSA. Plant and soil samples were collected at harvesting time from 99 fields in Benin, Ghana, Guinea, Kenya, Madagascar, Mozambique, and Nigeria, and then chemically analyzed. The Si concentration in straw ranged 1.7–8.4%, and the values in 68% of the fields were below the critical deficiency level of 5%. The Si concentration in straw was most significantly correlated with the amounts of water-soluble Si in soils after 1-week anaerobic incubation at 40 °C (hereafter, plant-available Si). The plant-available Si was particularly low in the acidic soils of Highland and Humid Agro-ecological zones, mainly consisting of weathered Oxisols and Ultisols. The mean Si values were greatest in the order of irrigated lowland (5.3%) > rainfed lowland (4.3%) > upland (3.4%) among different rice-growing environments. Multiple regression analysis revealed that 59% of the variation in Si concentration in straw was explained by the plant-available Si in soils, rice-growing environments, N application rates, and mineralizable N in soils. The regression model indicated that improvement of plant-available Si in soils could increase the Si concentration in straw at a rate of 0.043% per mg kg−1, while external N application lowered the Si concentration in straw at a rate of 0.0068% per kg N ha−1 input. This extensive survey revealed that low Si nutrient status was widely observed for rice as associated with limited plant-available Si in the SSA soils. The probability of Si deficiency can be increased with abundant N application and non-submerged field conditions. By focusing on these Si-deficient field conditions, further studies should quantify the relationship between Si-nutrient status and occurrence of environmental stresses such as blast infection so as to develop appropriate Si-management practices for rice production in SSA.
The effect of the application of acidified porous hydrate calcium silicate (APS) in nursery bed soil and porous hydrate calcium silicate (PS) in paddy fields on the growth of rice plants (Oryza sativa L. cv. Hitomebore) was examined in 2002 and 2003. The results revealed the following: 1) Shoot dry weight of rice seedlings increased by APS treatment in nursery bed soil. The tiller number of rice plants after transplanting in both years also increased by APS treatment in nursery bed soil, and in 2003, the tiller number in the treatment with a combination of APS in nursery bed soil and PS in paddy fields was significantly higher than that in the other treatments until the maximum tiller number stage. Furthermore, the root length of rice plants 14 d after transplanting increased by APS treatment in nursery bed soil. 2) Silicon concentration in the soil solution significantly increased by PS treatment in paddy fields, and the concentration of dissolved carbon oxide increased by APS treatment in nursery bed soil. 3) Only in the APS treatment the rice yield was 341 g m−2, while 400 and 450 g m−2 in the PS and both APS and PS treatments, respectively, in 2003. Percentages of ripened grains in the plots without PS treatment ranged from 57 to 63%, respectively, while, those in the PS treated plots were 82%. The numbers of panicles and ripened grains in both APS and PS treatments were the highest among the treatments. Based on the above results, we concluded that both APS in nursery bed soil and PS in paddy field treatments were effective in improving the silicon nutrition and growth of rice plants, and that this effect was enhanced by a combination of treatments with the two.
• The quantification of silicon (Si) in plants generally requires a digestion procedure before the determination of the dissolved Si concentration by spectrometric analysis. Recent procedures produce rapid and accurate measurements, but are based on either hazardous chemicals or sophisticated instrumentation. • Here, we describe a simpler procedure using Tiron. Tiron [4,5-dihydroxy-1,3-benzene-disulfonic acid disodium salt, (HO)(2)C(6)H(2)(SO(3)Na)(2)] is currently used as a selective extractant for amorphous silica in soils. Because Si in the shoots is mostly composed of amorphous opaline silica particles (i.e. phytoliths), we tested the Tiron extraction procedure for plants. • Our results are critically discussed in relation to two other standard procedures: electrothermal vaporization determination and high-temperature lithium-metaborate digestion. • We demonstrate that Tiron extraction is an alternative method which allows the rapid, safe and accurate quantification of Si in shoots of various plants covering a wide range of Si concentrations.
A procedure was developed for the determination of Si directly in citrate‐dithionite extracts of soils. The procedure, which provides for noninterference by citrate, dithionite, Fe, and P was developed for measurement of the absorbance of the reduced β‐molybdosilicic acid in the working range of 5 to 25 µg of Si in 50 ml. Interference by unoxidized dithionite was eliminated by bubbling air through the extract. The interference by citrate was prevented by an excess of molybdate; that by Fe and P by tartaric acid addition.
The citrate‐dithionite treatment released, per gram of soil, 3 to 174 mg of Fe 2 O 3 , 0.8 to 42 mg of Al 2 O 3 , and 0.1 to 3.8 mg Si(OH) 4 . The water‐soluble silica ranged from 0 to 26 µg of Si(OH) 4 per ml of solution before removal of reductantsoluble Fe 2 O 3 and Al 2 O 3 ; it increased into the range of 5 to 58 after removal. At any given pH of Henry soil (in the pH range of 4 to 7), the water‐soluble silica increased markedly as a result of previous citrate‐bicarbonate‐dithionite extraction. The release of Fe, Al, and Si that occurred with the various soils on reduction indicates a possible mechanism by which these constituents may increase sufficiently to support the well‐known formation of montmorillonite from soluble and alluviated materials moved into positions of slow drainage. These constituents in solution would also favor preservation of any montmorillonite present in soil parent materials.
A direct method of estimation of silica in rice plant tissues is reported. This involves the digestion of finely ground plant
samples with concentrated nitric acid in corning-glass conical flasks followed by dissolution in Na2CO3 in stainless-steel beakers; the plant silica is thereby converted into molybdenum reactive form which is estimated colorimetrically.
This method represents an improvement over the time consuming fusion procedure followed ordinarily and also dispenses with
use of platinumware. re]19740501