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1.
We investigate the effect of Al on K+ uptake by rice roots. Potassium-38 (38K), a positron emitting nuclide (the half-life: 7.61 min), was used to trace K+ behavior. When a rice root was treated with 10μM Al for 24 h, the uptake of 38K in the root was increased in the range of 1 to 2 cm from the root tip compared with that of the control sample. Because the root continued to grow without showing any damage of plasma membrane during the Al treatment, it was suggested that the 38K uptake was not occurred through diffusion into the cells. The uptake of 38K in both treatments, with/without Al, was decreased by VO43- (inhibitor of H+-ATPase on plasma membrane) and DNP (H+ ionophore) treatment, which suggested that the K+ uptake was performed through an active transport, such as H+:K+ transport or H+ gradient promoted by an Al treatment.  相似文献   

2.
Seventeen soybean cultivars were screened to discern differences in aluminum (Al) sensitivity. The Sowon (Al-tolerant) and Poongsan (Al-sensitive) cultivars were selected for further study by simple growth measurement. Aluminum-induced root growth inhibition was significantly higher in the Poongsan cultivar than in the Sowon cultivar, although the differences depended on the Al concentration (0, 25, 50, 75 or 100 μmol L–1) and the amount of exposure (0, 3, 6, 12 or 24 h). Damage occurred preferentially in the root apex. High-sensitivity growth measurements using India ink implicated the central elongation zone located 2–3 mm from the root apex. The Al content was lower 0–5 mm from the root apices in the Sowon cultivar than in the apices of the Poongsan cultivar when exposed to 50 μmol L–1 Al for 12 h. Furthermore, the citric acid exudation rate was more than twofold higher in the Sowon cultivar. Protein production of plasma membrane (PM) H+-ATPase from the root apices (0–5 mm) was upregulated in the presence of Al for 24 h in both cultivars. This activity, however, decreased in both cultivars treated with Al and the Poongsan cultivar was more severely affected. We propose that Al-induced growth inhibition is correlated with changes in PM H+-ATPase activity, which is linked to the exudation of citric acid in the root apex.  相似文献   

3.
Radiocaesium fixation in soils is reported to occur on frayed edge sites of micaceous minerals. The weathering of mica in acid soils may therefore influence the Cs+ fixation process and thereby the mobility of the radiopollutant. We produced a laboratory weathering model biotite → trioctahedral vermiculite → oxidized vermiculite → hydroxy interlayered vermiculite (HIV) and quantified the Cs+ fixation of each mineral both in a fixed K+–Ca2+ background and in acid conditions. The transformation process was achieved through K depletion by Na-tetraphenylboron, oxidation with Br2 and Al-intercalation using NaOH and AlCl3. In a constant K+–Ca2+ background, vermiculite fixed 92–95% of the initial 137Cs+ contamination while biotite and HIV fixed only 18–33%. In acid conditions, the interlayer occupancy by either potassium (biotite) or hydroxy-Al groups (HIV) strongly limited Cs+ fixation to 1–4% of the initial 137Cs+ contamination. Cs+ fixation occurred on vermiculitic sites associated with micaceous wedge zones. Though both oxidized and trioctahedral vermiculites fixed similar Cs+ amounts in a constant K+–Ca2+ background (92–95%), the oxidized vermiculite retained much more radiocaesium in acid conditions (78–84% against 54–59%), because of its dioctahedral character.  相似文献   

4.
Aluminium speciation and pH of an acid soil in the presence of fluoride   总被引：2，自引：0，他引：2  
The aim was to determine whether the addition of F to an acid soil reduces the concentration of free Al3+ and other forms that have been shown to be toxic to plants. The ability of two different extracts to reflect Al speciation in the soil solution was also investigated. Addition of F (0-5.2μmolg−1) to an acid soil (pH 4.15, soil solution) increased the pH and total concentrations of Al and F in the soil solution whereas Al3+ remained constant or decreased. Soil solution pH, total soluble Al and Al extracted by 0.01 m CaCl2 are not good predictors of the likelihood of aluminium toxicity in soils containing soluble fluoride.  相似文献   

5.
Thirty-one soil solutions were extracted by immiscible displacement with CCl4 under high speed centrifugation from sub-horizons of three podzolic soils from north-eastern Ontario, Canada. The solutions were analysed for major cations and anions and a speciation of dissolved Fe and Al was attempted to distinguish 'free', 'organically bound' and 'inorganically bound' species. Results indicated that the Ae (E) horizon solutions were of low pH and contained mainly organically bound Fe and Al. With depth, pHs increased, ionic strengths decreased and the relative proportion of inorganically bound Fe and Al increased. Although application of phase diagrams permitted only a semi-quantitative interpretation of the data, all horizon solutions, with the exception of some Ae solutions, appeared supersaturated with respect to likely occurring crystalline and amorphous aluminosilicates [kaolinite, halloysite, allophane (Al:Si=l) and imogolite]. Of the phases considered, reactions involving imogolite-allophane, gibbsite-halloysite, gibbsite-allophane and gibbsite-imogolite all appeared reasonable in controlling the content of Al3+ and H4SiO4 in solution, although the presence of gibbsite and imogolite could not be definitely confirmed in these soils.  相似文献   

6.
From acidic tea soils of Kagoshima Prefecture in Japan, some soil properties were determined and 38 strains of acid tolerant microorganisms were isolated. Different Al3+ concentrations were applied to YG media to estimate Al resistance. Selected microbial strains could grow strongly in the liquid media in the presence of 100 mM Al3+ and survive even in 300 mM Al3+ at pH 3.0. Their base sequences of 28S rDNA-D1/D2 were determined and sequence data were searched using the Basic Local Alignment Search Tool (BLAST) system. The results of sequencing revealed that the isolates belong to two different species, Cryptococcus sp. and Candida palmioleophila. When cultivated with various Al3+ concentrations, the yeast growth was inhibited at a concentration of 200 mM. Pre-cultivation of these strains with 0–30 mM Al3+ did not promote the growth response caused by Al3+. Inductively-Coupled Plasma-Mass Spectrometry (ICP-MS) was used to assess the elimination of Al. The amount of Al remaining in culture media was decreased considerably after cultivation. Due to a capacity for resistance to significant Al concentrations as well as high Al elimination, these acid tolerant and Al resistant yeasts may have potential applications in the bio- and phyto-remediation of Al and acid-contaminated soils.  相似文献   

7.
The shear moduli of the < 2 μm size fraction of three soils have been measured for samples of 10–35% w/w solid. Samples were thixotropic, the shear modulus increasing with time. This increase can be described by simple models and visualized in terms of the formation of links between particles. For a given soil the shear modulus increases with ionic form in the order Ca2+∼Mg2+ + + < Li+ and varies in a complex manner with electrolyte concentration.  相似文献   

8.
Abstract. The success of organic cropping systems depends on symbiotic N2 fixation by leguminous crops, and it is important to explore new management systems to improve the nitrogen input through N2 fixation. During two growing seasons the possible advantage of growing fababean ( Vicia faba L.) in ridges was studied in comparison to the traditional method on flat soil. Differences in soil physical parameters resulted in a significantly greater microbial activity and a deeper root system at the flowering stage when grown in the ridge than on the flat. Consequently, the amount of fixed N at flowering was significantly greater in ridges than in flat soil. However, during the period from flowering until harvest, when the major part of the N uptake and N2 fixation took place, the differences between the treatments disappeared. Average values for the growing season of fluorescein diacetate hydrolysis, arylamidase activity and arylsulphatase activity were significantly greater in the ridge than on the flat, and the microbial biomass-C, derived from substrate induced respiration (SIR), was on average 232 and 223 μg C g−1 soil in the ridge and on the flat, respectively. Measured total-N uptake, including root N (0–30 cm depth), ranged from 206 to 247 kg N ha−1, of which 182–201 kg N ha−1 was fixed N. From 154 to 173 kg N ha−1 was removed in grain resulting in a soil-N balance of +28 kg N ha−1 in both years. However, by including estimates of total root N and rhizodeposition-N the soil-N balance ranged from +52 to +62 kg N ha−1.  相似文献   

9.
Abstract. The recommended method of reducing the emission of NH3 while spreading manure is to plough or harrow the manure into the soil. This in turn increases the possibility of N2O emission. At two sites in southern Sweden emissions of NH3 and N2O were measured after spreading pig slurry by broadcasting and band spreading. The band spreading technique can be used in growing crops i.e. when nitrogen is most needed, and it is thought that the NH3 emission is smaller with this technique compared to broadcasting. The average NH3 loss was 50% of applied NH4+ during warm/dry conditions and 10% during cold/wet conditions. The N2O emission was always less than 1% of applied NH4+. When the NH3 emission decreased, the direct N2O emission increased. However, when taking into account the indirect N2O emission due to deposition of NH3 outside the field, the spreading techniques all produced similar total N2O emissions. The ammonia emission was not much lower for the band spreading technique compared to broadcasting, when compared on seven occasions.  相似文献   

10.
Abstract. Soil samples from a 32-year grassland field experiment were taken from 0–5, 5–10, and 10–15 cm soil depths in February 2002. Plots received annual treatments of unamended control, mineral fertilizer, three rates of pig slurry and three rates of cow slurry, each with six replicates. Samples were analysed for cation exchange capacity (CEC), exchangeable cations (Na+, K+, Ca2+, Mg2+), pH and Olsen P. Exchangeable sodium percentage (ESP) was calculated as a sodicity indicator. Mean ESP was generally greater for slurry treatments than the control, with a trend of increasing ESP with application rate. This was particularly marked for cow slurry. At 0–5 cm depth ESP increased from 1.18 in the control to 1.75 at the highest rate of pig slurry and 5.60 at the highest rate of cow slurry. Similar trends were shown for CEC, exchangeable Na+, K+ and Mg2+, Ca2+ and Olsen P. The build-up of soil P due to slurry applications, together with this combination of physical and chemical factors, may increase the risk of P loss to surface waters, particularly from soils receiving high rates of cow slurry.  相似文献   

11.
Significant increases in extractable ions resulted from air-drying and grinding samples of two infertile Aquults. Effects of the sample preparation differed markedly between ions and between the two soils. Regression equations were calculated to predict extractable ions in dried, ground samples from extractable ions in fresh, unground samples and the relationships were compared between the two soil series. Regressions were significantly different between soils for extractable PO34, Mg++, and K+, but not for Ca++ and Na+. Extractable NH +4 and NO-3 in fresh, unground samples were not correlated with those in air-dry, ground samples of either soil. Differences in response to preparation between soil types appeared to be related to the oxidative status of these soils in the field, wherein constituents of more poorly-drained soils may be less stable to the oxidizing conditions of air-drying and grinding. Such complexities suggest that effects of sample preparation should be considered when interpreting soil nutrient data for studies of forest nutrient cycling and forest soil fertility.  相似文献   

12.
To study the mechanisms of Al tolerance in rice, we focused on the change of rhizosphere pH. The 4-d seedlings were treated with Al solution (0, 10, 50 mM) for 24 h. Then each sample was put on an agarose gel including bromocresol green, so that the color of the gel indicated pH change. During 2-h contact, the pH of rhizosphere was decreased gradually, especially for Al-treated samples, showing the specific pH profiles along the root axis. Pretreatment of sample plants with a decoupling reagent 2,4-dinitrophenol (DNP) or a plasma membrane H+-ATPase inhibitor Na3VO4 did not decrease rhizosphere pH. Therefore, it was suggested that the H+ secretion activity was involved with Al-tolerant mechanisms of rice.  相似文献   

13.
We examined the aluminium solubility in the upper B horizon of podzols and its relation to the solid phase of the soil in 60 samples covering a pH range from 3.8 to 5.1. Solid phases were characterized by extractions with acid oxalate and pyrophosphate (pH 10). The solubility of Al was studied in a batch experiment in which samples were equilibrated with 1 m m NaCl at 8°C for 5 days. We also monitored the dissolution kinetics of Al and Si, in some samples. The oxalate and pyrophosphate extractions suggested that secondary Al was mainly organically bound in most soils, and imogolite-type materials seemed to constitute much of inorganic secondary Al. No single gibbsite or imogolite equilibrium could explain Al3+ activities. In all samples Al solubility, defined as log{Al3+} + 1.65pH, was closely related to the molar ratio of aluminium to carbon in the pyrophosphate extracts (Alp/Cp). Solubility increased with the Alp/Cp ratio until the latter reached ≈ 0.1. This indicated that solubility was controlled by organic complexation, at least when Alp/Cp was small. Silica dissolved slowly in most soils used in the kinetic experiments. We conclude that imogolite-type materials in the upper B horizon dissolved slowly because of coating with humic substances or ageing or both.  相似文献   

14.
Real-time images of nitrogen fixation in an intact nodule of hydroponically cultured soybean ( Glycine max [L] Merr.) were obtained. In the present study, we developed a rapid method to produce and purify 13N-labeled radioactive nitrogen gas (half life: 9.97 min). 13N was produced from a 16O (p, α) 13N nuclear reaction. The target chamber was filled with CO2 and irradiated for 10 min with protons at an energy of 18.3 MeV and an electric current of 5 μA, which was delivered from a cyclotron. All CO2 in the collected gas was absorbed and removed with powdered soda-lime in a syringe and replaced with helium gas. The resulting gas was injected into gas chromatography and separated and a 35 mL fraction, including the peak of [13N]-nitrogen gas, was collected by monitoring the chromatogram. The obtained gas was mixed with 10 mL of O2 and 5 mL of N2 and used in the tracer experiment. The tracer gas was fed into the underground part of intact nodulated soybean plants and serial images of the distribution of 13N were obtained non-invasively using a positron-emitting tracer imaging system (PETIS). The rates of nitrogen fixation of the six test plants were estimated to be 0.17 ± 0.10 μmol N2 h−1 from the PETIS image data. The decreasing rates of assimilated nitrogen were also estimated to be 0.012 ± 0.011 μmol N2 h−1. In conclusion, we successfully observed nitrogen fixation in soybean plants with nodules non-invasively and quantitatively using [13N]N2 and PETIS.  相似文献   

15.
To investigate the effects of plant species in grassland on methane (CH4) and nitrous oxide (N2O) fluxes from soil, fluxes from an orchardgrass ( Dactylis glomerata L.) grassland, white clover ( Trifolium repens L.) grassland and orchardgrass/white clover mixed grassland were measured weekly from April 2001 to March 2002 using a vented closed chamber method. Related environmental parameters (soil inorganic N content, soil pH (H2O) value, soil moisture content, soil temperature, grass yield, and the number of soil microorganisms) were also regularly monitored. On an annual basis, CH4 consumption in the soil of the orchardgrass grassland, white clover grassland and orchardgrass/white clover mixed grassland was 1.8, 2.4, and 1.8 kg C ha−1 year−1, respectively. The soil bulk density of the white clover grassland was lower than that of the other grasslands. Fluxes of CH4 were positively correlated with the soil moisture content. White clover increased the CH4 consumption by improving soil aeration. Nitrogen supply to the soil by white clover did not decrease the CH4 consumption in the soil of our grasslands. On the other hand, annual N2O emissions from the orchardgrass grassland, white clover grassland, and orchardgrass/white clover mixed grassland were 0.39, 1.59, and 0.67 kg N ha−1 year−1, respectively. Fluxes of N2O were correlated with the NO3− content in soil and soil temperature. White clover increased the N2O emissions by increasing the inorganic N content derived from degrading white clover in soil in summer.  相似文献   

16.
To evaluate the atmospheric load of reactive gaseous nitrogen in the fast-developing Eastern China region, we compiled inventories of nitrous oxide (N2O), nitrogen oxide (NOx) and ammonia (NH3) emissions from a typical rural catchment in Jiangsu province, China, situated at the lower reach of the Yangtze River. We considered emissions from synthetic N fertilizer, human and livestock excreta, decomposition of crop residue returned to cropland and residue burning, soil background and household energy consumption. The results showed that, for the 45.5 km2 catchment, the annual reactive gaseous emission was 279 ton N, of which 7% was N2O, 16% was NOx and 77% was NH3. Synthetic N fertilizer application was the dominant source of N2O and NH3 emissions and crop residue burning was the dominant source of NOx emission. Sixty-seven percent of the total reactive gaseous N was emitted from croplands, but on a per unit area basis, NOx and NH3 emissions in residential areas were higher than in croplands, probably as a result of household crop residue burning and extensive human and livestock excreta management systems. Emission per capita was estimated to be 18.2 kg N year−1 in the rural catchment, and emission per unit area was 56.9 kg N ha−1year−1 for NH3 + NOx, which supports the observed high atmospheric N deposition in the catchment. Apparently, efficient use of N fertilizer and biological utilization of crop straw are important measures to reduce reactive gases emissions in this rural catchment.  相似文献   

17.
【目的】明确贵州烟田土壤pH、交换性钙(Ca2+)、交换性镁(Mg2+)和碳酸钙(CaCO3)的含量分布特征及其相互关系,指导土壤酸碱调节及钙镁肥料施用。【方法】采集贵州全省烟区500个典型烟田耕层(0～20 cm)土样,采用经典方法测定土壤p H、Ca2+、Mg2+和CaCO3含量,利用SPSS比较不同成土母质、土壤类型和区域之间pH、Ca2+、Mg2+和CaCO3的含量差异,定量分析pH与Ca2+、Mg2+和CaCO3之间的关系。【结果】土壤pH、Ca2+和Mg2+含量偏低的烟田分别占20.0%、18.2%和56.4%,偏高的烟田分别占37.0%、55.8%和29.6%。CaCO3低于10 g kg-1 烟田占88.4%。不同成土母质、...  相似文献   

18.
Low molecular weight organic acids exist widely in soils and have been implicated in many soil processes. The results in the present paper showed that the presence of organic anions led to a decrease in the adsorption of NO3−. The effect of citrate was much larger than that of oxalate and malate. Among different soils, the effect for Hyper-Rhodic Ferralsol and Rhodic Ferralsol was larger than that for Haplic Acrisol, which was related to the content of iron oxides in these soils. The effect of organic anions decreased with the increases in pH value and the amount of organic anions added. The organic anions depressed the adsorption of NO3− through two mechanisms, the competition of the organic anions for adsorption sites with NO3− and the change of soil surface charge caused by the specific adsorption of organic anions.  相似文献   

19.
Abstract. Leaching of calcium (Ca), potassium (K) and magnesium (Mg) from urine patches in grazed grassland represents a significant loss of valuable nutrients. We studied the effect on cation loss of treating the soil with a nitrification inhibitor, dicyandiamide (DCD), which was used to reduce nitrate loss by leaching. The soil was a free-draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass ( Lolium perenne ) and white clover ( Trifolium repens ). The treatment of the soil with DCD reduced Ca2+ leaching by the equivalent of 50%, from 213 to 107 kg Ca ha−1 yr−1 on a field scale. Potassium leaching was reduced by 65%, from 48 to 17 kg K ha−1 yr−1. Magnesium leaching was reduced by 52%, from 17 to 8 kg Mg ha−1 yr−1. We postulate that the reduced leaching loss of these cations was due to the decreased leaching loss of nitrate under the urine patches, and follows from their reduced requirement as counter ions in the drainage water. The treatment of grazed grassland with DCD thus not only decreases nitrate leaching and nitrous oxide emissions as reported previously, but also decreases the leaching loss of cation nutrients such as Ca2+, K+ and Mg2+.  相似文献   

20.
The effects of B and Ca treatments on root growth, nutrient localization and cell wall properties in wheat ( Triticum aestivum L.) plants with and without Al stress were investigated. Seedlings were grown hydroponically in a complete nutrient solution for 7 d and then treated with B (0, 40 μM), Ca (0, 2,500 μM), and Al (0, 100 μM) in a 500 μM CaCl2 solution for 8 d. The cell wall materials (CWM) were extracted with a phenol: acetic acid: water (2:1:1 w/v/v) solution and used for subsequent pectin extraction with trans -1,2-diami-nocyclohexane- N,N,N,N -tetraacetic acid (CDTA) and Na2CO3 solutions. Boron, Ca, and B + Ca treatments enhanced root growth by 19.5, 15.2, and 27.2%, respectively, compared to the control (pH 4.5). Calcium and B+Ca treatments enhanced root growth with Al stress by 43 and 54%, respectively, while B did not exert any effect. The amounts of CWM and pectin per unit of root fresh weight increased by Al treatment, whereas the Ca and B+Ca treatments slightly reduced the contents of these components. Seventy-four percent of total B, 69% of total Ca, and 85% of total Al were located in the cell wall in the B, Ca, and Al treatments, respectively and 32% of total B, 33% of total Ca, and 33% of total Al were located in the CDTA-soluble and Na2CO3-soluble pectin fractions. A more conspicuous localization of B was observed in the presence of Al. Aluminum treatment markedly decreased the Ca content in the cell wall as well as pectin fractions, mainly in the case of the CDTA-soluble pectin fraction. Boron + Ca treatment decreased the Al content in the cell wall and pectin fractions compared to the Ca treatment alone in the presence of Al. It is concluded that the B+Ca treatment enhanced root growth and, B and Ca uptake, and helped to maintain a normal B and Ca metabolism in the cell walls even in the presence of Al.  相似文献   

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