Factors affecting formation of methyl nitrite in soils

The formation of CH₃ONO in 11 soils treated with HNO₂ or NaNO₂ in a closed system, was studied by measuring the concentration in the gas space above the soil and by absorbing CH₃ONO in HI. The gaseous concentration of CH₃ONO increased and then decreased following additions of HNO₂ or NaNO₂, and the production of CH₃ONO increased with increasing concentrations of HNO₂ or NaNO₂ added to soils.
The amounts of CH₃ONO trapped in HI were 13.5 to 20.4 times higher than those determined by integrating under the net production curves. The evolved CH₃ONO amounted to 0.4 to 3.5% of added NO₂⁻, and 4.2 to 50% of the gaseous forms of N absorbed by acidic KMnO₄ solution. The CH₃ONO evolved from soils was positively correlated with the methoxy content of the soils, and inversely related to soil pH, with negligible amounts being evolved from alkaline soils. The results show that CH₃ONO is a product of NO₂⁻ decomposition in soils, and indicate that small concentrations of the gas may be produced in N–fertilized soils in which NO₂⁻ accumulates.     

Mechanistic insights into furan formation in Maillard model systems

Furan has recently received considerable attention as a possibly carcinogenic compound occurring in thermally processed foods. Although several food constituents have been identified as furan precursors, multiple formation pathways remain unclear. Therefore, the mechanisms of furan formation in Maillard model systems were studied by means of the carbon module labeling (CAMOLA) technique. Under both roasting and pressure-cooking conditions, furan was formed from glucose via the intact skeleton, and its formation pathways from glucose alone were not amino acid-dependent. However, some amino acids, especially alanine and serine, did influence the furan production by providing an additional formation pathway. Furthermore, most amino acids enhanced the furan production from glucose. Roasting conditions produced 25-100 times higher amounts of furan as compared to pressure-cooking conditions. Surprisingly, in the alanine/glucose model systems, the relative importance of furan production from glucose alone and from the combination of a glucose-derived and an alanine-derived fragment changed completely over a limited time course of 60 min.     

Factors affecting the formation of alkylpyrazines during roasting treatment in natural and alkalinized cocoa powder

The cocoa roasting process at different temperatures (at 125 and 135 degrees C for 3 min, plus 44 and 52 min, respectively, heating-up times) was evaluated by measuring the initial and final free amino acids distribution, flavor index, formol number, browning measurement, and alkylpyrazines content in 15 cocoa bean samples of different origins. These samples were also analyzed in manufactured cocoa powder. The effect of alkalinization of cocoa was studied. Results indicated that the final concentration and ratio of tetramethylpyrazine/trimethylpyrazine (TMP/TrMP) increased rapidly at higher roasting temperatures. The samples roasted with alkalies (pH between 7.20 and 7.92), such as sodium carbonate, or potassium plus air injected in the roaster during thermal treatment, exhibited a greater degree of brown color formation, but the amount of alkylpyrazines generated was adversely affected. The analysis of alpha-free amino acids at the end of the roasting process demonstrated the importance of the thermal treatment conditions and the pH values on nibs (cocoa bean cotyledons), liquor, or cocoa. Higher pH values led to a lower concentration of aroma and a higher presence of brown compounds.     

Factors affecting chlamydospore formation by Fusarium solani f. cucurbitae in pure culture

A study was made of several factors affecting the production of chlamydospores by Fusarium solani f. cucurbitae in pure culture. Lysis of macroconidia and chlamydospore formation is favoured by the absence of glucose in liquid culture media. Both low pH and addition of ammonium chloride to the culture medium reduces lysis of macroconidia and inhibits chlamydospore formation. Chlamydospores formed in media lacking glucose were produced from macroconidia in a manner resembling their formation in soil. They were examined by light and electron microscopy. When placed into natural soil, they acted as survival structures.     

Odorants generated by thermally induced degradation of phospholipids

The qualitative and quantitative aroma composition of heated aqueous dispersions of egg phosphatidylcholine (PC) and egg phosphatidylethanolamine (PE) were characterized by aroma extract dilution analysis and isotope dilution assay. On the basis of FD-factors and odor activity values, trans-4,5-epoxy-(E)-2-decenal was found to be the most potent odorant followed by (E,E)-2,4-decadienal, 1-octen-3-one, and hexanal. The amount of (E,E)-2,4-decadienal in PC was about 20-fold higher compared to PE, while hexanal was the major odor-active compound in the PE sample. (E,Z,Z)-2,4,7-Tridecatrienal was identified for the first time as an odor-active volatile constituent of heated phospholipids exhibiting a characteristic egg white-like note. Further odorants first reported in thermally treated phospholipids were (Z)-2-decenal, (E)-2-decenal, and (E)-2-undecenal. Differences in the fatty acid composition of PC and PE can only partially explain the quantitative results found in this study, thus suggesting that further parameters may influence the formation of carbonyls from heated aqueous dispersions of phospholipids.     

引起小麦倒伏的因子分析

田间调查和室内测试的结果表明 ,倒伏主要是由于品种、密度、氮肥力及其交互作用造成 .氮肥力过高是倒伏的基础 ,品种、密度、降雨是倒伏的诱因     

Factors affecting sulfate adsorption,organic sulfur formation,and mobilization in forest and grassland spodosols

Forest and grassland soils that contained varying amounts of Fe and Al were collected from England and Wales. Fractionation of free Fe and Al was accomplished to determine which components affected sulfate adsorption. Organic Fe and Al were the dominant fractions in most soil horizons and high amounts of these organically bound metals and, to some extent, crystalline Fe oxide were associated with high sulfate adsorption potentials. These adsorption potentials reflected naturally occurring amounts of absorbed sulfate and ester sulfate. Overall, the C content exhibited a positive relationship with sulfate adsorption potentials. Soils with a high C content also exhibited high rates of organic S formation. The rate of organic S mobilization was greater in soils with higher amounts of soluble sulfate. Organic S was the largest pool and, typically, sulfonate S was the most abundant constituent of the organic pool.     

Factors affecting the formation of dark, thick epipedons beneath forest vegetation, Michigan, USA

Extremely gravelly, coarse-textured soils (frigid Udorthents and Rendolls) with different thicknesses of Oa+A horizon sequences were studied to identify factors that have influenced their genesis. These well-drained, forested soils occur on geomorphic surfaces that range in age from 3200 to 6000 years BP. The soils all have more than 500 g kg^?1 coarse fragments by mass; most contain less than 300 g kg^?1 fine earth. In the lower solum of most pedons, content of cobbles increases and amount of fine earth decreases. Most coarse fragments are dolomite and chert. Thick, gravelly Oa and A horizons are weakly correlated with parent material characteristics such as high pH and carbonate contents. Organic matter concentrations in, and thicknesses of, upper horizons are enhanced by an abundance of coarse clasts, as soils with the most gravel exhibited the thickest and darkest epipedons. Relatively high amounts of crystalline clasts in the fine gravel fraction, as well as feldspathic minerals in the fine sands, also appear to promote the development of mollic epipedons.     

Factors affecting triadimefon degradation in soils

The degradation of triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)butan-2-one] was studied in two soils, mollisol and inseptisol, under varying conditions of moisture and temperature, and the role of cow manure amendment and soil sterilization on fungicide degradation was ascertained. The soil moisture content affected the pathway followed for triadimefon degradation. In nonflooded soils (60% water-holding capacity), triadimefon was reduced to triadimenol, and in flooded soils, it was metabolized to the diol derivative [1-(1H-1,2,4-triazol-1-yl)-3,3-dimethylbutan-2-one-1,4-diol]. In nonflooded soils, triadimefon was more persistent in soil having more organic carbon content (mollisol), and the amendment of cow manure (5%) further enhanced its persistence. On the contrary, in flooded soil systems, the higher the soil organic carbon content was, the less persistent was the fungicide, and amendment of cow manure further enhanced its degradation. Triadimefon degradation was faster at 35 degrees C than at 27 degrees C. Triadimefon degradation in soils was mediated by the microorganisms, and no triadimefon degradation was observed in sterile soils. Triadimefon (1 mg/kg) did not affect soil phosphatase activity in either of the soils; however, soil dehydrogenase activity was significantly reduced, especially in mollisol soil.     

Factors affecting l-asparaginase activity in soils

Summary Studies on the distribution of l-asparaginase in soil profile samples revealed that its activity generally decreases with sample depth and is accompanied by a decrease in organic C content. Statistical analyses indicated that l-asparaginase activity was significantly correlated (^** P<0.01) with organic C (r=0.86^**) and total N (r=0.78^**) in the 26 surface soil samples examined. There was no significant relationship between l-asparaginase activity and the percentage of clay or sand. There was, however, a significant correlation between l-asparaginase activity and amidase (r=0.82^**) and urease (r=0.79^**) activities in the surface samples studied. The effects of 21 trace elements, 12 herbicides, 2 fungicides, and 2 insecticides on l-asparaginase activity in soils showed that most of the trace elements and pesticides, at the concentrations used, inhibited the reaction catalyzed by this enzyme. The degree of inhibition varied among soils. When the trace elements were compared, at the rate of 5 mol g^-1 soil, the average inhibition of l-asparaginase in three soils showed that Ag(I), Cd(II), Hg(II), Ni(II), Pb(II), and V(IV) were the most effective inhibitors (average inhibition 20%). The least effective inhibitors (average 10%) included Cu(I), Ba(II), Co(II), Sn(II), Zn(II), Al(III), Se(IV), As(V), and Mo(VI). Other trace elements that inhibited l-asparaginase activity in soils were Cu(II), Mn(II), As(III), B(III), Cr(III), Fe(III), Ti(IV), and W(VI). When the pesticides were compared, at the rate of 10 g active ingredient g^-1 soil, the average inhibition of l-asparaginase activity in three soils ranged from 4% with Merpan to 46% with Malaspray. Other pesticides that inhibited l-asparaginase activity in soils (average inhibition in parentheses) were Aatrex (17%), Alanap (21%), Amiben (18%), Banvel (12%), Bladex (24%), 2,4-D (17%), Dinitramine (19%), Eradicane (16%), Lasso (40%), Paraquat (33%), Sutan (39%), treflan (7%), Menesan (18%), and Diazinon (33%).     

植物提取影响因素研究进展

Hyperaccumulators concentrate trace metals and heavy metals in their shoots when grown in metal-contaminated soils and these trace metal-loaded plants may be removed by harvesting the fields. Studies exploring the beneficial role of these hyperaccumulators to clean up the environment have led to the development of phytoextraction. The success of phytoextraction depends upon the high biomass of plant species and bioavailability of metals for plant uptake. The phytoavailability of metals is influenced by soil-associated factors, such as pH, redox potential, cation exchange capacity, soil type, and soil texture, and by plant-associated factors, such as root exudates and root rhizosphere processes (microorganisms). Efficiency of phytoextraction can be improved by advanced agronomic practices including soil and crop management by application of genetic engineering to enhance the metal tolerance, shoot translocation, accumulation, and sequestration and by application of chelate treatments to enhance metal bioavailability. Application of microorganisms including bacteria and mycorrhiza may facilitate the phytoextraction application at commercially large scale.     

Review: Factors affecting rhizosphere priming effects

Living plants change the local environment in the rhizosphere and consequently affect the rate of soil organic matter (SOM) decomposition. The rate may increase for 3‐ to 5‐folds, or decrease by 10 % to 30 % by plant cultivation. Such short‐term changes of rate (intensity) of SOM decomposition are due to the priming effect. In the presence of plants, a priming effect occurs in the direct vicinity of the living roots, and it is called rhizosphere priming effect (RPE). Plant‐mediated and environmental factors, such as, plant species, development stage, soil organic matter content, photosynthesis intensity, and N fertilization which affect RPE are reviewed and discussed in this paper. It was concluded that root growth dynamics and photosynthesis intensity are the most important plant‐mediated factors affecting RPE. Environmental factors such as amount of decomposable C in soil and N_min content are responsible for the switch between following mechanisms of RPE: concurrence for N_min between roots and microorganisms, microbial activation or preferential substrate utilization. Succession of mechanisms of RPE along the growing root in accordance with the rhizodeposition types is suggested. Different hypotheses for mechanisms of filling up the C amount loss by RPE are suggested. The ecosystematic relevance of priming effects by rhizodeposition relates to the connection between exudation of organic substances by roots, the increase of microbial activity in the rhizosphere through utilization of additional easily available C sources, and the subsequent intensive microbial mobilization of nutrients from the soil organic matter.     

Factors affecting potassium leaching in different soils

Abstract. A set of lysimeter based experiments was carried out during 2000/01 to evaluate the impact of soil type and grassland management on potassium (K) leaching. The effects of (1) four soil textures (sand, loam, loam over chalk and clay), (2) grazing and cutting (with farmyard manure application), and (3) K applied as inorganic fertilizer, dairy slurry or a mixture of both sources were tested. Total K losses in the clay soil were more than twice those in the sand soil (13 and 6 kg K ha⁻¹, respectively) because of the development of preferential flow in the clay soil. They were also greater in the cut treatment than in the grazed treatment (82 and 51 kg K ha⁻¹, respectively; P 0.01), associated with a 63% increase of K concentration in the leachates from the former (6.7 ± 0.28 and 4.1 ± 0.22 mg K L⁻¹ for cut and grazed, respectively; P 0.01) because of the K input from the farmyard manure. The source of fertilizer did not affect total K losses or the average K concentration in the leachates ( P > 0.05), but it changed the pattern of these over time.     

Factors affecting lycopene oxidation in oil-in-water emulsions

Evidence that dietary lycopene decreases the risk for a number of health conditions has generated new opportunities for the addition of lycopene to functional foods. This work examined the potential of oil-in-water emulsions as a lycopene delivery system for foods. Oil-in-water emulsions containing lycopene were prepared using different kinds of surfactant (cationic, anionic, and nonionic) and oil types (corn oil, stripped corn oil, and hexadecane). The formation of fatty acid oxidation products and the degradation of lycopene and tocopherol were then monitored. Fatty acids and lycopene had greater stability in oil-in-water emulsions stabilized by cationic dodecyltrimethylammonium bromide (DTAB) or nonionic polyoxyethylene (23) lauryl ether than by anionic sodium dodecyl sulfate (SDS). Oxidative stability in the corn oil-in-water emulsions stabilized by SDS was in the following order: tocopherolhexadecane>tocopherol-stripped corn oil. Lycopene degradation rates were similar in emulsions with and without fatty acids, suggesting that lycopene loss was independent of the presence of fatty acids. These results suggest that the stability of lycopene in oil-in-water emulsions could be inhibited by altering the emulsion droplet interface and by the presence of tocopherols.     

精原细胞分化与凋亡的影响因素

人们对哺乳动物精子发生过程已经有了相当多的了解，但对精子发生过程的调控机制仍然了解甚少。生殖激素及原癌基因和肿瘤抑制基因的表达产物对维持正常精子发生中各类细胞的存活、增殖和凋亡，以及各类细胞受损伤后的清除均具有十分重要的作用。本文论述了促卵泡激素、雌激素、雄激素、干细胞因子、Bcl-2家族蛋白及p53蛋白在原细胞的分化和凋亡中的作用，以便人们进一步了解精子发生的调控机制。     

Factors affecting the soil sorption of iodine

Iodine-129 is an important radionuclide released from nuclear facilities because of its long radioactive half-life and its environmental mobility. Its retention in surface soils has been linked to pH, organic matter, and Fe and Al oxides. Its inorganic solution chemistry indicates I will most likely exist as an anion. Three investigations were carried out to provide information on the role of the inorganic and organic chemistry during sorption of I by soil. Anion competition using Cl^? showed that anion exchange plays a role in I sorption in both mineral and organic soils. The presence of Cl decreased the loss of I^? from solution by 30 and 50% for an organic and a carbonated sandy soil respectively. The I remaining in solution was associated primarily with dissolved organic carbon (DOC). The loss rate from solution appears to depend on two reactions of I with the soil solids (both mineral and organic) creating both a release to and a loss from solution, and the reaction of I with the DOC (from very low to high molecular weight). Composition analyses of the pore water and the geochemical modelling indicate that I sorption affects the double-charged anion species in solution the most, particularly SO₄ ^?. Iodide introduced to natural bog groundwater at three concentrations (10^?3, 10^?1 and 10 meq L^?1) remained as I^? and was not lost from solution quickly, indicating that the association of I with DOC is slow and does not depend on the DOC or I concentration. If sorption of I to soil solids or DOC is not sensitive to concentration, then stable I studies, which by necessity must be carried out at high environmental concentrations, can be linearly extrapolated to radioactive I at much lower molar concentrations.     

Factors affecting aggregate instability of Greek agricultural soils

Abstract

The aggregate stability of several surface soils from Thessaly plain, Central Greece, was studied using an instability index which classified the soils according to the stability of their aggregates to water. This index was correlated to the basic soil properties influencing aggregate stability. It was found that soil aggregate stability was positively correlated with clay content, total specific surface area, cation exchange capacity, base saturation, and free silicon oxides content. Silt, very fine and fine sand, and the ratio (sand+silt)/clay influenced negatively the aggregate stability. Organic matter content and sesquioxides have no effect on aggregate stability. It was also observed that the fraction of carbonates with silt dimension influenced negatively the aggregate stability. From the results of this study it was concluded that the factors affecting water aggregate stability were specific surface area and cation exchange capacity of the soils.     

典型龟裂碱土土壤光谱特征影响因素研究

为了提高基于土壤光谱特征预测土壤盐渍化程度的准确性,需要研究土壤光谱特征的因素影响。该文通过对野外、室内预处理、不同含水率、粒径和粗糙度条件下龟裂碱土表层土壤光谱的测定,系统研究了不同因素对龟裂碱土光谱特征的影响。结果表明:土壤碱化程度越强表层土壤光谱反射率越高,在450~925 nm范围内,碱土表层野外光谱反射率比重度、中度、轻度碱化土壤和非碱化土壤野外光谱反射率高7.36%、23.18%、32.10%和39.97%;765、945和974 nm附近是龟裂碱土盐渍化信息的敏感波段;相同土壤经过室内预处理后反射率明显低于野外土壤,且预处理后不同碱化程度土壤间光谱反射率差异也小于野外光谱。土壤含水率较低时,随着土壤含水率的增加土壤光谱反射率逐渐降低,但当含水率高于田间持水率时土壤反射率随土壤含水率的增加而增加,在整个研究波段含水率为26.45%时土壤反射率较含水率为22.33%和25.39%的反射率平均分别升高39.68%和19.79%。土壤粒径越小反射率越高,较大粒径土壤在760~768 nm形成独特的"双峰"现象。土壤粒径越大反射率受表面粗糙度的影响越小,且土壤表面越粗糙光谱吸收率越大。整体来讲,在450~1000 nm波段范围内,不同碱化程度的龟裂碱土野外表层土壤光谱特征差异显著;室内经过预处理后的龟裂碱土土壤光谱特征差异主要取决于土壤含水率,而碱化程度和土壤表面粗糙度的变化对其影响较小。该研究可以为龟裂碱土盐渍化信息的准确预测提供科学依据。     

Factors affecting the cropping potential of reinstated soils

Abstract. Comparisons of crop production on recently reinstated soil in Northumberland have shown that the reduced yield potential of such soil may not be inevitable. Storage of soil in bunds did not greatly reduce subsequent crop yields, but failure to drain the land did. Provided an effective drainage scheme was installed, arable and grass crops could be grown successfully, responding very well to additions of nitrogen fertilizer and other normal good husbandry practices. To date it seems that neither deep cultivation nor the use of grass leys were as effective in the restoration process as had been expected.     

Factors affecting diurnal stem contraction in young Douglas-fir

Diurnal fluctuation in a tree's stem diameter is a function of daily growth and of the tree's water balance, as water is temporarily stored in the relatively elastic outer cambial and phloem tissues. On a very productive site in southwestern Washington, U.S.A., we used recording dendrometers to monitor stem diameter fluctuations of Douglas-fir at plantation ages 7 and 8 and related the fluctuations to environmental variables measured on-site. Growing-season diurnal stem contraction (DSC) averaged 0.21% of stem diameter, while dormant-season DSC averaged 0.03% of stem diameter. Maximum daily stem diameter generally occurred between 7:00 and 9:00 Pacific Standard Time (PST) and minimum stem diameter occurred between 17:00 and 20:00 PST. Diurnal stem contraction during the growing season was predicted by a model that included vapor pressure deficit and solar radiation (adjusted R² = 0.84). A similar model predicted DSC during the dormant season with an adjusted R² = 0.26. Soil water availability was high, and soil water content was not correlated with DSC. On four of the coldest winter days (mean daytime air temperature <0 °C), large decreases in stem diameter were observed. Recording dendrometers, used for continuous diameter measurements throughout the growing season, have the potential to provide important information not only on tree growth but also on a tree's water balance.