接种沙门氏菌苗可使新生雏鸡和强制换羽母鸡得到免疫保护

过去人们常认为,由于刚出壳雏鸡的免疫系统尚未发育成熟,同时肠道内缺乏有益的微生物,因而处于高度的敏感期,此时接种沙门氏菌苗产生的保护作用很有限。然而,最新的研究表明,在这些敏感期接种疫苗,可诱发产生保护作用。     

Microbial remediation of a pentachloronitrobenzene-contaminated soil under Panax notoginseng: A field experiment

Pentachloronitrobenzene (PCNB) is an organochlorine fungicide that is mainly used in the prevention and control of diseases in crop seedlings. Microbial removal is used as a promising method for in-situ removal of many organic pesticides and pesticide residues. A short-term field experiment (1 year) was conducted to explore the potential role of a PCNB-degrading bacterial isolate, Cupriavidus sp. YNS-85, in the remediation of a PCNB-contaminated soil on which Panax notoginseng was grown. The following three treatments were used:i) control soil amended with wheat bran but without YNS-85, ii) soil with 0.15 kg m^-2 of solid bacterial inoculum (A), and iii) soil with 0.30 kg m^-2 of solid bacterial inoculum (B). The removal of soil PCNB during the microbial remediation was monitored using gas chromatography. Soil catalase and fluorescein diacetate (FDA) esterase activities were determined using spectrophotometry. In addition, cultivable bacteria, fungi, and actinomycetes were counted by plating serial dilutions, and the microbial biodiversity of the soil was analyzed using BIOLOG. After 1 year of in-situ remediation, the soil PCNB concentrations decreased significantly by 50.3% and 74.2% in treatments A and B, respectively, when compared with the uninoculated control. The soil catalase activity decreased in the presence of the bacterial isolate, the FDA esterase activity decreased in treatment A, but increased in treatment B. No significant changes in plant biomass, diversity of the soil microbial community, or physicochemical properties of the soil were observed between the control and inoculated groups (P<0.05). The results indicate that Cupriavidus sp. YNS-85 is a potential candidate for the remediation of PCNB-contaminated soils under P. notoginseng.     

Comparative proteomic analysis of mushroom cell wall proteins among the different developmental stages of Pleurotus tuber-regium

Cell wall proteins (CWPs) play a vital role in the development of the different morphological stages including mycelium, fruiting body, and sclerotium in mushrooms which are important human food sources. Using fractionation by detergents and reducing agents, mushroom cell wall fractions from the different developmental stages of Pleurotus tuber-regium (PTR) were prepared. Using one-dimensional gel electrophoresis coupled with LC-MS, there were 103, 91, and 48 noncovalently linked CWPs identified in the cell wall fractions of the PTR mycelium, fruiting body, and sclerotium, respectively. Comparing the CWPs in these cell wall fractions, 19 of them were in common, among which 17 belonged to the functional categories of translation, ribosomal structure, and biogenesis. This is the first study to provide important biochemical insights into the different developmental stages of PTR mediated by CWPs, and the identified CWPs helped to explain the morphological changes of PTR mushrooms during cultivation.     

Fertilizer ammonium : nitrate ratios determine phosphorus uptake by young maize plants

We investigated the interacting effects of inorganic nitrogen and the main inorganic phosphorus form in dairy manure (dicalcium phosphate, CaHPO₄) on growth, nutrient uptake, and rhizosphere pH of young maize plants. In a pot experiment, three levels of CaHPO₄ (0, 167, and 500 mg P pot^?1) were combined with nitrogen (637 mg N pot^?1) applied at five NH₄‐N : NO₃‐N ratios (0 : 100, 25 : 75, 50 : 50, 75 : 25, and 100 : 0) and a nitrification inhibitor in a concentrated layer of a typical acid sandy soil from Denmark. ¹⁵N‐labeled NH₄‐N was applied to differentiate the role of nitrification and to partition nitrogen uptake derived from NH₄‐N. Among treatments including nitrogen, shoot biomass, rooting and phosphorus uptake were significantly higher at the five‐leaf stage when CaHPO₄ was applied with NH₄‐N : NO₃‐N ratios of 50 : 50 and 75 : 25. In these treatments, rhizosphere pH dropped significantly in direct proportion with NH₄‐N uptake. The fertilizers in the concentrated layer had a root‐inhibiting effect in treatments without phosphorus supply and in treatments with pure NO₃‐N or NH₄‐N supply. Increased nitrogen uptake as NH₄‐N instead of NO₃‐N reduced rhizosphere pH and enhanced acquisition of applied CaHPO₄ by young maize plants, which may have positive implications for the enhanced utilization of manure phosphorus.     

Production of mutants with high cold tolerance in spring canola (<Emphasis Type="Italic">Brassica napus</Emphasis>)

A major factor affecting spring canola (Brassica napus) production in Canada is killing frosts during seedling development in the spring and seed maturation in the fall. The objective of this study was to explore the possibility of producing spring canola lines with mutations that have altered biochemical pathways that increase cold tolerance. The approach was to generate UV point mutations in cultured microspores followed by chemical in vitro selection of individual mutant microspores or embryos resulting in measurable alterations to various biochemical pathways with elevated levels of key defense signaling molecules such as, salicylic acid (SA), p-Fluoro-d,l-Phenyl Alanine (FPA), and jasmonic acid (JA). In addition, since proline (Pro) is known to protect plant tissues in the cold-induced osmotic stress pathway, mutants that overproduce Pro were selected in vitro by using three Pro analogues: hydroxyproline (HP), azetidine-2-carboxylate (A2C); and, 3,4-dehydro-d,l-proline (DP). Of the 329 in vitro selected mutant embryos produced, 74 were identified with significant cold tolerance compared to their donor parents through indoor freezer tests at −6°C, and 19 had better winter field survival than winter canola checks. All chemically selected mutant doubled haploids with increased cold tolerance compared well with parent lines for all seed quality and agronomic parameters. Development of increased frost tolerant cultivars should allow for spring canola to be produced in western Canada without compromising seed quality.     

Combining agent-based and stock-flow modelling approaches in a participative analysis of the integrated land system in Reichraming, Austria

The integrated modelling of coupled socio-ecological systems in land-change science requires innovative model concepts capable of grasping the interrelations between socioeconomic and natural components. Here, we discuss the integrated socio-ecological model SERD (Simulation of Ecological Compatibility of Regional Development) that was developed for the municipality of Reichraming in Upper Austria in a participative 2-year process involving local stakeholders. SERD includes three main components: (1) an agent-based actors module that simulates decisions of farmsteads, the municipal administration and other important actors; (2) a spatially explicit (GIS based) land-use module that simulates land-use change at the level of individual parcels of land and (3) an integrated socio-ecological stock-flow module that simulates carbon and nitrogen flows through both socioeconomic and ecological system compartments. We report on outcomes of a scenario analysis that outlines possible future trajectories depending on both external (e.g. agricultural subsidies and prices) and internal (e.g. innovation, willingness to co-operate) factors. We find that both external and internal factors can affect the behaviour of the integrated system considerably. Local and regional policies are found to be able to counteract adverse global socioeconomic conditions to some extent, but not to reverse the trend altogether. We also find strong interdependencies between socioeconomic and ecological components of the system. Fully evaluating these interdependencies is, however, not possible at the local scale alone and will require explicit consideration of higher-level effects in future research.     

Combining top-down and bottom-up dynamics in land use modeling: exploring the future of abandoned farmlands in Europe with the Dyna-CLUE model

Land use change is the result of interactions between processes operating at different scales. Simulation models at regional to global scales are often incapable of including locally determined processes of land use change. This paper introduces a modeling approach that integrates demand-driven changes in land area with locally determined conversion processes. The model is illustrated with an application for European land use. Interactions between changing demands for agricultural land and vegetation processes leading to the re-growth of (semi-) natural vegetation on abandoned farmland are explicitly addressed. Succession of natural vegetation is simulated based on the spatial variation in biophysical and management related conditions, while the dynamics of the agricultural area are determined by a global multi-sector model. The results allow an exploration of the future dynamics of European land use and landscapes. The model approach is similarly suitable for other regions and processes where large scale processes interact with local dynamics.     

A discussion on and alternative to the Penman-Monteith equation

The Penman-Monteith (PMe) equation that estimates evaporation from leaf/canopy surfaces is based on a few approximations. Several authors discussed ensuing errors and suggested improvements. This paper reminds those discussions which ended in the early nineties. It compares linearized PMe− with non-linear iterative solutions and illustrates resulting deviations. It differentiates between deviations for daily and hourly evaporation rate estimates. The latter are found to be higher. It also demonstrates deviations obtained at two different altitudes above sea level. Considering present tendencies to refine evaporation estimates for practical purposes and making use of easily available methods for solving non-linear equations this paper offers a new method to estimate evaporation.In a first step, a simple algebraic term, the surface temperature control sum, is introduced to find approximate differences between air and evaporating surface (leaf, canopy) temperatures. It suggests to concentrate research on the r_s/r_a ratio. A new formula is derived for estimating leaf/canopy surface temperatures for non-water stressed plants.In a second step, the estimates of temperature differences are used to calculate evaporation estimates. This two-step approximation leads to appreciably smaller errors as compared to the PMe-solution over the full range of input parameters of agro-meteorological relevance. It is, however, less accurate than some of methods proposed in literature. The method is meant for practical application in agricultural water management.     

Can giant clam (Tridacna squamosa) populations be restored on Singapore's heavily impacted coral reefs?

• 1. Giant clams have been a sustainable resource for millennia, but unregulated harvesting has led to local extinctions within the Indo‐Pacific region. Giant clam mariculture can produce large numbers of juveniles for restocking wild populations where natural recruitment is low or absent.
• 2. Singapore is surrounded by more than 60 small islands, many with fringing reefs. These reefs, however, experience increased turbidity and sedimentation resulting from massive coastal development projects and regular dredging of shipping lanes.
• 3. Seven reefs off Singapore's southern islands were surveyed (9670 m²) for giant clams. Also, an experiment was conducted to determine the growth of Tridacna squamosa reared in aquaria under three light treatments: ～50% ambient photosynthetically active radiation (PAR); ～25% ambient PAR; and ～12% ambient PAR. Finally, 144 clams (T. squamosa) were transplanted to four reefs around Singapore to study survival and growth in a heavily impacted environment.
• 4. A total of 23 adult clams from three species were found during the survey, representing a mean density of 0.24 per 100 m². Most clams were found at Raffles Lighthouse, Singapore's ‘best’ reef. No juvenile clams were encountered. In the aquarium experiment, clam growth was significantly different among the three light treatments, with growth greatest in the ～50% ambient PAR treatment. Of the 144 transplanted clams, 116 (80.6%) were recovered after 7 months. All specimens had increased in size, with growth rates among reefs ranging from 3.3 mm month^?1 (SD=1.3 mm) to 4.8 mm month^?1 (SD=1.6 mm).
• 5. Results suggest that, despite high levels of sedimentation and turbidity on Singapore's reefs, giant clams can survive and grow well. Restocking efforts using maricultured clams may be effective in enhancing the dwindling local populations. It is not clear, however, whether a self‐sustaining community can be established as high sedimentation may hinder larval settlement and survival.

Copyright © 2007 John Wiley & Sons, Ltd.