The mechanical properties of wheat bran and the contribution of each constitutive tissue on overall bran properties were determined on a hard wheat (cv. Baroudeur) and a soft wheat (cv. Scipion). Manual dissection allowed three different layers to be separated from wheat bran, according to radial and longitudinal grain orientations, which were identified by confocal laser scanning microscopy as outer pericarp, an intermediate strip (comprising inner pericarp, testa, and nucellar tissue), and aleurone layer, respectively. Tissue microstructure and cell wall composition were determined. Submitted to traction tests, whole bran, intermediate, and aleurone layers demonstrated elastoplastic behavior, whereas pericarp exhibited elastic behavior. By longitudinal orientation, pericarp governed 50% bran elasticity (elastic strength and rigidity), whereas, in the opposite orientation, bran elastic properties were mostly influenced by the other tissues. Regardless of test orientation, the linear force required to bran rupture corresponded to the sum of intermediate and aleurone layer strengths. According to radial orientation, the intermediate strip governed bran extensibility, but according to longitudinal orientation, all tissues contributed until bran disruption. Tissues from both wheat cultivars behaved similarly. A structural model of wheat bran layers illustrated the detachment of pericarp from intermediate layer within radial bran strips. 相似文献
Background, Aims, and Scope The genetic structure and the functionality of soil microbes are both important when studying the role of soil in the C cycle
in elevated CO2 scenarios. The aim of this work was to investigate the genetic composition of the fungal community by means of PCR-DGGE and
the functional diversity of soil micro-organisms in general with MicroResp-based community level physiological profiling (CLPP)
in a poplar plantation (POPFACE) grown under elevated [CO2] with and without nitrogen fertilization.
Materials and Methods The POPFACE experimental plantation and FACE facility are located in central Italy, Tuscania (VT). Clones of Populus alba, Populus nigra and Populus x euramericana were grown, from 1999 to 2004, in six 314 m2 plots treated either with atmospheric (control) or enriched (550 μmol mol−1) CO2 with FACE (Free Air CO2 Enrichment) technology in each growing season. Each plot is divided into six triangular sectors, with two sectors per poplar
genotype: three species × two nitrogen levels. After removal of the litter layer one soil core per genotype (10 cm wide, 20
cm depth) was taken inside each of the three sectors in each plot, for a total of 36 soil cores (3 replicates × 2 [CO2] × 2 fertilization × 3 species) in October 2004 and in July 2005. DNA was extracted with a bead beating procedure. 18S rDNA
gene fragments were amplified with PCR using fungal primers (FR1 GC and FF390). Analysis of CLPP was performed using the MicroResp
method. Carbon substrates were selected depending on their ecological relevance to soil and their solubility in water. In
particular rhizospheric C sources (carboxylic acids and carbohydrates) were chosen considering the importance of root inputs
for microbial metabolism.
Results The fertilization treatment differentiated the fungal community composition regardless of elevated [CO2] or the poplar species; moreover the number of fungal species was lower in fertilized soil. The effect of elevated [CO2] on the fungal community composition was evident only as interaction with the fertilization treatment as, in N-sufficient
soils, the elevated [CO2] selected a different microbial community. For CLPP, the differ ent poplar species were the main factors of variation. The
FACE treatment, on average, resulted in lower C utilization rates in un-fertilized soils and higher in fertilized soils.
Discussion Fungal biomass and fungal composition depend on different factors: from previous studies we know that the greater quantity
and the higher C/N ratio of organic inputs under elevated [CO2] influenced positively the fungal biomass both in fertilized and in un-fertilized soil, whereas nitrogen availability resulted
to be the main determinant of fungal community composition in this work. Whole active microbial community was directly influenced
by the soil nutrient availability and the poplar species. Under elevated CO2 the competition for N with plants strongly affected the microbial communities, which were not able to benefit from added
rhizospheric substrates. Under Nsufficient conditions, the increase of microbial activity due to [CO2] enrichment was related to a more active microbial community, favoured by the current availability of C and N.
Conclusions Different factors influenced the microbial community at different levels: poplar species and root exudates affected the functional
properties of the microbial community, while the fungal specific composition (as seen with DGGE) remained unaffected. On the
other hand, factors such as N and C availability had a strong impact on the community functionality and composition. Fungal
community structure reflected the availability of N in soils and the effect of elevated [CO2] on community structure and function was evident only in N-sufficient soils. The simultaneous availability of C and N was
therefore the main driving force for microbial structure and function in this plantation.
Recommendations and Perspectives Using the soil instead of soil extracts for CLPP determination provides a direct measurement of substrate catabolism by microbial
communities and reflects activity rather than growth because more immediate responses to substrates are measured. Further
applications of this approach could include selective inhibition of different microbial functional groups to investigate specific
CLPPs. To combine the structural analysis and the catabolic responses of specific microbial communities (i.e. fungi or bacteria)
could provide new outlooks on the role of microbes on SOM decomposition.
ESS-Submission Editor: Dr. Kirk Semple (k.semple@lancaster.ac.uk) 相似文献
The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption of hexadecyltrimethylammonium (HDTMA) and octadecyltrimethylammonium (ODTMA) on montmorillonite was studied above and below their critical micelle concentrations (CMC). At concentrations above the CMC, the loading exceeded the clay's cation exchange capacity (CEC) and indicated higher affinity of the cation with the longer alkyl chain. An adsorption model could adequately simulate adsorption at concentrations below the CMC, and yield fair predictions for the effect of ionic strength. The model indicated that above the CMC adsorbed micelles contributed significantly to the amount of ODTMA adsorbed. Evidence for adsorption of ODTMA micelles on montmorillonite was provided by X-ray diffraction, freeze-fracture electron microscopy, and dialysis bag measurements. SFM was not adsorbed directly on the clay mineral, and adsorbed at low levels, when the organic cation was adsorbed as monomers. In contrast, a large fraction of SFM adsorbed on the clay mineral when incorporated in micelles that adsorbed on the clay. 相似文献
Composts are increasingly used as environmentally safe biofertilizers in sustainable agriculture all over the world. Although it is well known that composts may contribute to soil vitality and sustainability, and in the enhancement of various soil microbiological processes, little is known about their direct or indirect effects on a microbial-community or population level. Ammonia oxidation by autotrophic ammonia-oxidizing bacteria (AOB) is a key process in agricultural and natural ecosystems and plays an important role in the global nitrogen cycle. Here, we studied the diversity and community composition of ammonia oxidizers in a long-term crop rotation field experiment (>10 years) where four major types of compost (from organic waste, cattle manure, green waste and sewage sludge) had been applied annually. The methods used ranged from PCR-DGGE (denaturing gradient gel electrophoresis) and cloning of 16S rDNA fragments to quantitative real-time PCR. Cluster analysis of DGGE profiles differentiated between the microbial communities of composts, compost-treated soils and mineral-fertilized soils. The community composition of the composts was not reflected in the community composition of the compost-treated soils. Sequencing of screened clones revealed a characteristic AOB community structure for the representative soil sample and the four composts. All AOB-like sequences grouped within the Nitrosospira cluster 3 and 4 and within the Nitrosomonas cluster 6 and 7. The average AOB abundance in compost-treated soils was two times higher than in mineral-fertilized soils (4.3×107 and 1.9×107, respectively). Our data suggest that composts do not leave direct microbial imprints in soils after long-term amendment, but an indirect effect on the AOB community was evident. 相似文献
An arable soil with organic matter formed from C3-vegetation was amended initially with maize cellulose (C4-cellulose) and sugarcane sucrose (C4-sucrose) in a 67-day laboratory incubation experiment with microcosms at 25 °C. The amount and isotopic composition (13C/12C) of soil organic C, CO2 evolved, microbial biomass C, and microbial residue C were determined to prove whether the formation of microbial residues depends on the quality of the added C source adjusted with NH4NO3 to the same C/N ratio of 15. In a subsequent step, C3-cellulose (3 mg C g−1 soil) was added without N to soil to determine whether the microbial residues formed initially from C4-substrate are preferentially decomposed to maintain the N-demand of the soil microbial community. At the end of the experiment, 23% of the two C4-substrates added was left in the soil, while 3% and 4% of the added C4-cellulose and C4-sucrose, respectively, were found in the microbial biomass. The addition of the two C4-substrates caused a significant 100% increase in C3-derived CO2 evolution during the 5-33 day incubation period. The addition of C3-cellulose caused a significant 50% increase in C4-derived CO2 evolution during the 38-67 day incubation period. The decrease in microbial biomass C4-C accounted for roughly 60% of this increase. Cellulose addition promoted microorganisms strongly able to recycle N immediately from their own tissue by “cryptic growth” instead of incorporating NO3− from the soil solution. The differences in quality of the microbial residues produced by C4-cellulose and C4-sucrose decomposing microorganisms are also reflected by the difference in the rates of CO2 evolution, but not in the rates of net N mineralization. 相似文献
The rhizomes of Peucedanum ostruthium (L.) Koch (masterwort) are traditionally used in the alpine region as ingredient of liqueurs and bitters, and as a herbal drug. A sensitive and specific high-performance liquid chromatography-diode-array detection-mass spectrometry (HPLC-DAD-MS) method has been developed for the simultaneous identification and quantification of its main coumarins, oxypeucedanin hydrate, oxypeucedanin, ostruthol, imperatorin, osthole, isoimperatorin, and ostruthin. Fast HPLC separation could be achieved on an Acclaim C18 column (150 mm × 2.1 mm i.d., 3 μm) using a mobile phase gradient of acetonitrile-water modified with 0.01% acetic acid. The quantification by HPLC-DAD was performed with imperatorin as external standard and validated to demonstrate selectivity, linearity, precision, and accuracy. The content of the main coumarins was quantitated in various batches of commercial and field-collected rhizomes of Peucedanum ostruthium, as well as in beverages prepared thereof. 相似文献
Inhibitor of apoptosis (IAP) proteins are negative regulators of cell death. IAP family members contain RING domains that impart E3 ubiquitin ligase activity. Binding of endogenous or small-molecule antagonists to select baculovirus IAP repeat (BIR) domains within cellular IAP (cIAP) proteins promotes autoubiquitination and proteasomal degradation and so releases inhibition of apoptosis mediated by cIAP. Although the molecular details of antagonist-BIR domain interactions are well understood, it is not clear how this binding event influences the activity of the RING domain. Here biochemical and structural studies reveal that the unliganded, multidomain cIAP1 sequesters the RING domain within a compact, monomeric structure that prevents RING dimerization. Antagonist binding induces conformational rearrangements that enable RING dimerization and formation of the active E3 ligase. 相似文献
Poultry are important for many poor households in developing countries, but there are many constraints to poultry production, including disease. One of the most important diseases of chickens is Newcastle disease (ND). Even though there are effective vaccines against this disease available in most countries, uptake by small-scale poultry keepers is often low. In this study, two areas in Kenya and Tanzania were studied, where some villages had received additional support to get vaccination and other villages had not. In Kenya, 320 households from 10 villages were interviewed, of which half of the villages had active promotion of vaccination through village-based advisors. In Tanzania, 457 households were interviewed, of which 241 came from villages that have had active support through either a project or government extension services. Knowledge about vaccines and the attitudes towards vaccinating against ND was evaluated using mixed multivariable logistic models. Results indicate that in Kenya, the most important determinants for understanding the function of a vaccine were having had support in the village and to have knowledge about ND signs, while in Tanzania gender and previous vaccine use were important in addition to having had support. Attitudes towards vaccination were mainly determined by knowledge, where more knowledge about how vaccines work in general or about ND contributed to more positive attitudes. Among Kenyan farmers that had never used the vaccine before, the amount of birds they lost to disease and predators also influenced attitudes. In conclusion, this study supports the notion that knowledge is a very important component of extension support and that simply making vaccines available may not be sufficient for high levels of uptake.