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1.
Frankia 《European Journal of Soil Biology》2000,36(3)
The capacity of different soils of New Caledonia to induce nodulation in Gymnostoma poissonianum was studied. The soils were sampled under five Gymnostoma species, Alphitonia neocaledonica (a non-nodulated endemic Rhamnaceae) and Pinus caribea (an introduced species) growing in various ecological conditions. Using G. poissonianum as trap-host, we observed a higher abundance of Frankia from Gymnostoma spp. in the rhizosphere of A. neocaledonica as compared with bare soils and P. caribea rhizosphere. The nodulating capacity of A. neocaledonica rhizosphere was almost similar to that of the five Gymnostoma species (symbiotic host) studied in the same stations. In comparison, bare soils or rhizosphere of P. caribea had poor nodulating capacities. We isolated fourteen Frankia strains from nodules of G. poissonianum after baiting with the rhizospheric soils of five Gymnostoma and A. neocaledonica. Using the PCR/RFLP method, we confirmed the similarity with those already described. Frankia was abundant in the rhizosphere of A. neocaledonica in all the sites studied. One explanation could be a positive tropism of Frankia towards species belonging to families having nodulated species, which is the case of A. neocaledonica endemic in New Caledonia. We can suppose that the non-nodulated plants belonging to these families can excrete some chemical substances able to attract Frankia and to induce its proliferation. 相似文献
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The mineralization of native soil organic matter and the simultaneous diffusion of zero NH+4 and NO?3 to a solution sink of zero N concentration was analysed experimentally and theoretically for a fine sandy loam soil. Experimentally, the NH4 and NO3 ions produced in an incubated unsaturated soil column were allowed to diffuse through a sintered glass plate into a stirred solution sink. The distribution of NH+4 and NO?3 in the soil column was measured after various incubation times. The rate of ammonification was measured directly during incubation and the rate of nitrification modelled from nitrifier growth kinetics. A Freundlich equation was used to describe the equilibrium between soluble and exchangeable NH+4 in the soil. Terms for the microbial transformation of N and the adsorption-desorption of NH+4 were combined with diffusion equations which were solved numerically using finite difference methods. The model constructed was used to predict the NH+4 and NO?3 con-centration distributions in the soil column, and good agreement was obtained between the experimental and predicted concentration profiles. The use of the model for predicting the diffusive flux of mineral N to the outer surfaces of soil peds, where it is vulnerable to leaching, was demonstrated. 相似文献
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Concentrations of dialysable silica in equilibrium with Al2O3-SiO2-H2O sols at pH 4.5–5.0 confirm the formation of a poorly ordered non-dialysable proto-imogolite species with an Al : Si ratio near 2, close to that of imogolite. Sols with Al : Si>2 give nearly constant levels of free silica in solution in the range 2–6 μg/cm3, indicating equilibrium between proto-imogolite and aluminium hydroxide species. These findings indicate that imogolite-like precipitates in acid soils will buffer silica in solution to within this range during leaching episodes. Imogolite is more stable than a previous estimate suggested, and a revised value for its free energy of formation is proposed: ΔG0f(298.15) = -2929.7 kJ/mol. In Fe2O3-SiO2-H2O sols, the Fe : Si ratio of the non-dialysable species varies smoothly from 11 to 3 as free silica in solution ranges from 4 to 35 μg/cm3. Such sols are much less colloidally stable than hydroxyaluminium silicate sols, but mixed Al2O3—Fe2O3—SiO2—H2O sols are almost as stable as iron-free sols up to a Fe : Al ratio of 1.5. Thus migration of Al and Fe as mixed hydroxide sols can account for the almost constant ratio of Al to Fe with depth in oxalate extracts from Bs horizons of podzols. 相似文献
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R. J. Laughlin R. J. Stevens C. Müller & C. J. Watson 《European Journal of Soil Science》2008,59(2):285-291
The contribution of bacteria and fungi to NH4+ and organic N (Norg) oxidation was determined in a grassland soil (pH 6.3) by using the general bacterial inhibitor streptomycin or the fungal inhibitor cycloheximide in a laboratory incubation study at 20°C. Each inhibitor was applied at a rate of 3 mg g?1 oven‐dry soil. The size and enrichment of the mineral N pools from differentially (NH415NO3 and 15NH4NO3) and doubly labelled (15NH415NO3) NH4NO3 were measured at 3, 6, 12, 24, 48, 72, 96 and 120 hours after N addition. Labelled N was applied to each treatment, to supply NH4+‐N and NO3?‐N at 3.15 μmol N g?1 oven‐dry soil. The N treatments were enriched to 60 atom % excess in 15N and acetate was added at 100 μmol C g?1 oven‐dry soil, to provide a readily available carbon source. The oxidation rates of NH4+ and Norg were analysed separately for each inhibitor treatment with a 15N tracing model. In the absence of inhibitors, the rates of NH4+ oxidation and organic N oxidation were 0.0045 μmol N g?1 hour?1 and 0.0023 μmol N g?1 hour?1, respectively. Streptomycin had no effect on nitrification but cycloheximide inhibited the oxidation of NH4+ by 89% and the oxidation of organic N by more than 30%. The current study provides evidence to suggest that nitrification in grassland soil is carried out by fungi and that they can simultaneously oxidize NH4+ and organic N. 相似文献
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Thermal generation of volatiles in nine model reactions was studied and compared. Each of the model systems contained one amino acid and one monosaccharide. The amino acid was serine, threonine, or glutamine, and the monosaccharide was ribose, glucose, or fructose. More unsubstituted pyrazine was generated in serine-sugar systems than threonine-sugar systems. The formation of several furfuryl-substituted pyrazines and pyrroles was observed in some of the studied systems. Total pyrazines were generated more in glutamine-containing systems than in serine- and threonine-containing systems, and the reverse was true for generation of furfuryl-substituted compounds. Acetylpyrazine was generated in serine/threonine/glutamine-glucose and serine/glutamine-fructose systems. 相似文献
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Cu/Pb/Zn/Cd在石英砂中的迁移实验及模拟 总被引：4，自引：0，他引：4
通过稳定流混合置换实验,研究了孔隙水流速和pH变化对Cu/Pb/Zn/Cd在石英砂中迁移行为的影响,获得了示踪剂Br-和Cu/Pb/Zn/Cd的穿透曲线(BTCs);并通过室内批量平衡实验获得吸附系数,进而计算出阻滞因子Rd。基于这些实验结果,借助CXTFIT2.1软件,用平衡CDE模型拟合了Br-的BTCs,得到了弥散系数D;在此基础上应用CDE非平衡模型拟合Cu/Pb/Zn/Cd在不同流速和pH条件下的BTCs,并预测了平行实验和不同埋深处Cu/Pb/Zn/Cd浓度的动态变化。结果表明,Cu/Pb/Zn/Cd的迁移能力随流速的增大而增强,而随pH的增大而降低;化学非平衡的两点模型能较好地模拟本文实验条件下Cu/Pb/Zn/Cd的迁移过程。 相似文献
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14C-labelled glucose and 15N-labelled KNO3 were added to soil and the microbial biomass during 42 days' incubation was estimated using the chloroform fumigation-incubation method (CFIM). By day 1, most of the glucose (1577 μgCg?1 soil) was metabolized and 110 μg NO?3-Ng?1 soil were immobilized. In situ values for the proportions of biomass C (kC) and biomass N (kN) mineralized during the 10 days after CHCl3 fumigation were determined on the basis that the immobilized labelled C and N remaining in the soil at this time were present as living microbial cells and their associated metabolites. The tracer data indicated that biomass C could be calculated by applying a kc value of 0.41 to the CO2-C evolved from the fumigated sample without subtraction of an unfumigated “control”. Biomass N was estimated from the net NH4?-N accumulation during the fumigation-incubation. The problem of reimmobilization of NH+4-N where organisms of wide C:N ratio occur was overcome by adjusting the value of kN according to the ratio of CO2-C evolved: net NH4+-N accumulated during the fumigation-incubation (CF:NF).A CF:NF ratio of 6:1 resulted in a kN of 0.30 whereas a ratio of 13:1 indicated a kN of 0.20. 相似文献
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This study focuses on the processes occurring during incorporation of inorganic nitrogen into humic substances. Therefore rye grass, wheat straw, beech saw dust, sulphonated lignin and organosolve lignin were incubated together with highly 15N-enriched ammonium sulphate in the laboratory for 600 days. Samples from the incubates were periodically analysed for weight loss, and carbon and nitrogen contents. The samples were also analysed by solid-state 13C- and 15N-CPMAS-NMR-spectroscopy to follow the turnover of the materials during incubation. Most of the detectable N-signals was assigned to amide - peptide structures. The remaining intensities could be ascribed to free and alkylated amino groups, and those on the low field side of the broad amide-peptide signal to indole, pyrrole and nucleotide derivatives. Abiotic reactions of ammonia with suitable precursors and the formation of pyridine, pyrazine or phenyloxazone derivatives were not observed. Signals from ammonia and nitrate occurred only at the end of the incubation. 相似文献
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W. R. FISCHER T. PFANNEBERG E.-A. NIEDERBUDDE R. MEDINA 《European Journal of Soil Science》1981,32(3):409-418
Two soils differing in ammonium fixation capacity were incubated for 127 days with 15N-ammonium sulphate. In a gley soil with high NH+4-fixing capacity caused by smectites with a charge up to 0.8 per formula unit, the major part of the added ammonium was first fixed by minerals and then released slowly during incubation. The proportion of labelled N in the nitrate fraction increased during the first weeks and then decreased permanently. In contrast, in a histosol with low NH+4-fixing capacity, the exchangeable fraction contained most of the labelled NH+4, this being highly available to microorganisms and therefore subject to nitrification. About 50% of the added 15NH4 was lost from the histosol in 127 days, but only about 20 per cent was lost from the gley soil. 相似文献
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Olga Babourina Konstantin Voltchanskii Ian Newman Zed Rengel 《Soil Science and Plant Nutrition》2005,51(5):733-736
Potassium transport was investigated in the root elongation zone of Arabidopsis seedlings during the first minutes of Al3+ exposure, using the non-invasive MIFE microelectrode technique. To prevent pH changes during Al3+ application, and to separate aluminium from acidic stress, plants were pre-treated with 5 mM homoPIPES before addition of AlCl3 (pH 4.2). The 30-min treatment with 50 or 500 μM AlCl3 led to a significant increase in K+ efflux in solutions containing 100 μM CaCl2 . This efflux was suppressed by high concentrations of Ca2+ (10 mM) in the bathing solution. Our results suggest that elevated external Ca2+ activities can sustain K+ influx in the root elongation zone during Al3+ exposure either by maintaining [Ca2+ ]cyt or by affecting Al3+ uptake across the plasma membrane. 相似文献
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P. I. A. Kinnell 《Soil & Tillage Research》1998,45(3-4):349-357
Changing the basis of the R factor in the Universal Soil Loss Equation (USLE) to one based on the QREI30 index results in the need to calculate new soil erodibilities for use in the modified version (MUSLE-II). This paper provides a formula for calculating first approximations for the new soil erodibilities from known USLE soil erodibilities when data from runoff and soil loss plots associated with the determination of these USLE soil erodibilities are available. 相似文献
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Rong YANG Chaopu TI Feiyue LI Meihua DENG Xiaoyuan YAN 《Soil Science and Plant Nutrition》2010,56(1):86-94
To evaluate the atmospheric load of reactive gaseous nitrogen in the fast-developing Eastern China region, we compiled inventories of nitrous oxide (N2 O), 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 N2 O, 16% was NOx and 77% was NH3 . Synthetic N fertilizer application was the dominant source of N2 O 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−1 year−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
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不同铵硝比例对杭白菊次生代谢及抗病性的影响 总被引：1，自引：0，他引：1
【目的】 氮素形态与寄主营养和病害严重度的关系一直是人们关注的热点,氮素营养对植物次生代谢产物的影响也多有研究。斑枯病为杭白菊常见病害,黄酮和酚酸类物质是杭白菊主要的资源性化学成分。针对杭白菊生产中存在的问题,本文对不同铵硝比例处理下杭白菊的次生代谢及斑枯病发病情况进行调查和研究,以期为杭白菊生产过程中的氮素配施、 病害防治和次生代谢调控提供一定的技术借鉴。【方法】 采用盆栽试验,在总施氮水平相同的前提下,设置5个NH+4和NO-3比例,采用随机区组设计,管理措施一致,4次重复。采取对角线定点定株定期调查杭白菊斑枯病发病情况,采用描叶法和LI-3000C叶面积仪来确定植株病害状况,统计病情指数和病害发生率;测定苯丙氨酸解氨酶(PAL)、 木质素、 纤维素、 可溶性总糖、 可溶性蛋白、 超氧阴离子(O-2)、 丙二醛(MDA)等相关生理指标,超氧化物歧化酶(SOD)和过氧化物酶(POD)等抗氧化酶;测定不同处理下杭白菊花中次生代谢产物绿原酸、 木犀草苷、 3,5-O-双咖啡酰基奎宁酸以及根、 茎、 叶等不同部位总黄酮含量。对相关生理指标与发病率和病情指数进行相关性分析。【结果】 当铵硝比为25:75时木质素、 纤维素、 可溶性总糖、 POD、 苯丙氨酸和O-2含量达到最大值,MDA含量和SOD活性相对较低;杭白菊根、 茎、 叶及花中总黄酮的含量在铵硝比为25:75和0:100时均表现出较高的含量,绿原酸、 3,5-O-双咖啡酰基奎宁酸两者的含量在铵硝比为25:75时达到最大值,分别为0.67%和1.84%。随着硝态氮比例的增加杭白菊斑枯病的发病率和病情指数均有所下降。相关性分析显示木质素、 可溶性总糖、 PAL活性、 POD活性、 超氧阴离子、 绿原酸、 3,5-O-双咖啡酰基奎宁酸、 花中总黄酮的含量与杭白菊斑枯病的发病率和病情指数呈负相关,且达到极显著水平;SOD活性、 MDA含量与杭白菊斑枯病的发病率和病情指数呈正相关,且均达到显著水平。【结论】 杭白菊斑枯病的发病率和病情指数与相关生理指标和次生代谢密切相关,不同铵硝比例对药用菊花次生代谢产物及斑枯病的发生有一定的影响,当铵硝比为25:75时菊花斑枯病的发病率最低。 相似文献
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3 种挺水植物吸收水体NH4+、NO3-、H2PO4- 的动力学特征比较 总被引：2，自引：1，他引：2
本文用动力学试验研究了具有景观价值的3 种挺水植物—— 水生美人蕉(Canna generalis)、细叶莎草(Cyperus papyrus)、紫芋(Colocasia tonoimo)对H2PO4-、NH4+、NO3- 的吸收特征及差异。试验结果表明: 3 种挺水植物吸收H2PO4- 时, 美人蕉的吸收速率最快, 且在较低离子浓度条件下也可以吸收该离子, 说明其具有嗜磷特性, 能够适应广范围浓度H2PO4- 环境; 吸收NO3- 时, 细叶莎草的速率最快, 但对低浓度NO3- 环境的适应能力较差, 美人蕉吸收NO3- 的特性与细叶莎草刚好相反; 吸收NH4+ 时, 细叶莎草的吸收速率最快, 且在低浓度NH4+ 环境下仍能吸收该离子, 而美人蕉的吸收速率最慢, 但能在低浓度NH4+ 环境下吸收该离子。说明不同植物对养分的吸收特性存在较大差异, 各自的污染水体修复适用范围也不同。美人蕉可用于各种浓度H2PO4- 污染的水体修复; 而NO3- 污染严重的水体最适宜用细叶莎草作先锋植物, 修复到一定程度后再种植美人蕉来维持水质; 细叶莎草在各种浓度NH4+ 污染的水体中均适用, NH4+ 污染较轻的水体也可用美人蕉修复。 相似文献
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It has been established that arbuscular mycorrhizal (AM) fungi are involved in the conservation of soil structure. However, the effect of ectomycorrhizal (EM) fungi alone or in interaction with AM fungi in soil structure has been much less studied. This experiment evaluated EM and AM fungi effects on soil aggregation and plant growth. Ash plants (Fraxinus uhdei) were grown in pots, and were inoculated with Glomus intraradices and Pisolithus tinctorius separately but also in combination. Our results showed that F. uhdei established a symbiotic association with EM and AM fungi, and that these organisms, when interacting, showed synergistic and additive effects on plant growth compared to singly inoculated treatments. EM and AM fungi prompted changes in root morphology and increased water-stable aggregates. AM fungi affect mainly small-sized macroaggregates, while EM and EM-AM fungi interaction mainly affected aggregates bigger than 0.5 mm diameter. These results suggest that ectomyccorrhizal as well as arbuscular mycorrhizal fungi should be considered in restoration programs with Fraxinus plants. 相似文献
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D. G. KINNIBURGH 《European Journal of Soil Science》1983,34(4):759-768
The specific adsorption of Ca2+ and Zn2+ by ferrihydrite results in the net release of H+. The rate and H+/M2+ exchange stoichiometry of this reaction were monitored with a pH-stat. A rapid reaction of less than 6 min was followed by a slower reaction which continued at a diminishing rate for at least 2 days. Adsorption of Ca2+ at pH 7.8 and Zn2+ at pH 5.4 resulted in the net release of 0.92 and 1.70 mol H+/mol M2+ adsorbed, respectively. For Zn2+ adsorption, this stoichiometry was shown to be independent of pH. These estimates agree well with independent estimates based on the pH dependence of adsorption. The difference between the Ca2+ and Zn2+ stoichiometries was related to the differing acidity of the –OH2 ligands attached to the adsorbed ions. 相似文献