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51.
病毒及其亚单位蛋白的三维结构 (3 D)解析是认识病毒蛋白功能的有力手段。对病毒结构的认识正经历着病毒粒子电镜结构、纳米水平的精细结构及病毒组成蛋白原子水平 3 D结构的变化。晶体的 X射线衍射技术可在原子水平上认识病毒蛋白的结构。这为从结构生物学的角度认识病毒复制、病毒粒子的装配、病毒的致病与免疫机理及抗病毒药物设计提供了技术平台 相似文献
52.
在分析国家和新疆自治区重点扶持的贫困县———墨玉县农业生态系统的水土资源结构、农业种群结构和产业结构的基础上,对其绿洲农业生态经济系统进行了能量流、物质流和价值流的分析。结果显示其水土资源结构不平衡、种群结构单一、产业结构不甚合理,决定了绿洲功能较差,产投比低下的特点,并据此从可持续发展的角度提出了以发展生态农业为中心,改善绿洲农业生态经济系统结构并提高其功能的对策与建议。 相似文献
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54.
播期和种植密度对泛麦8号产量的影响 总被引:3,自引:0,他引:3
泛麦8号是河南黄泛区地神种业有限公司选育的高产矮秆小麦新品种。以泛麦8号为试材,研究了不同播期和密度对泛麦8号产量的影响。结果表明:10月5~19日播种,密度为75万~495万株/hm2时产量差别不大;10月26日以后播种,应适当加大播种密度(390万株/hm2以上)。 相似文献
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56.
为分析抗菌肽粗提物对肉鸡生长性能、粪便微生物菌群结构及经济效益的影响,试验选择体重相近的21日龄白羽肉鸡600只,随机分成4组,每组15个重复,每个重复10只,1组为空白对照组饲喂基础日粮,试验2、3、4组在基础日粮中分别添加1.0%、1.5%、2.0%的抗菌肽粗提物,试验期为21 d.结果表明:(1)试验2、3、4组... 相似文献
57.
为探讨近三十年来我国皱纹盘鲍养殖模式对群体遗传结构产生的影响,利用线粒体细胞色素C氧化酶亚基 (
58.
草坪作为园林绿化的基础造景,进行科学、细致的草坪养护管理工作必不可少,通过对马尼拉草坪的种植、浇水、施肥、修剪、除草除虫几方面加以论述,对小区域优质草坪的建植流程作了客观分析。 相似文献
59.
Low genetic variability in Sclerotinia sclerotiorum populations from common bean fields in Minas Gerais State,Brazil, at regional,local and micro‐scales 下载免费PDF全文
M. S. Lehner T. J. Paula Júnior B. T. Hora Júnior H. Teixeira R. F. Vieira J. E. S. Carneiro E. S. G. Mizubuti 《Plant pathology》2015,64(4):921-931
Sclerotinia sclerotiorum, causal agent of white mould, is the most destructive and widely distributed soilborne pathogen of common bean during the autumn–winter season in Brazil. Nevertheless, little is known about the genetic structure of the pathogen population. Microsatellite (SSR) markers and mycelial compatibility groups (MCGs) were used to characterize 118 isolates collected from 20 bean fields located in the most important growing regions of Minas Gerais State (MG). Additionally, the genetic variability among 10 isolates obtained from a single sclerotium was investigated in 10 different sclerotia. Seventy SSR haplotypes and 14 MCGs were identified among the 118 isolates. The genetic differences within bean growing areas accounted for most of the genetic variation (72%). Despite the relatively high genotypic diversity, the SSR loci were at linkage disequilibrium. Moreover, 70% of the isolates were assigned to only two MCGs, and haplotypes of a given MCG were closely related. The discriminant analysis of principal components revealed five groups. There was strong genetic differentiation between isolates collected in one municipality in southern MG when compared to other regions. Common bean resistance to white mould should be assessed with representative isolates of the five genetic groups and, if possible, of the different MCGs detected in the present study. One to five haplotypes were detected among the 10 isolates obtained from a single sclerotium. Therefore, in order to ensure genetic identity of an isolate, hyphal tip or monoascosporic isolates should be used. 相似文献
60.
Naugle David E. Higgins Kenneth F. Nusser Sarah M. Johnson W. Carter 《Landscape Ecology》1999,14(3):267-276
We evaluated the influence of scale on habitat use for three wetland-obligate bird species with divergent life history characteristics and possible scale-dependent criteria for nesting and foraging in South Dakota, USA. A stratified, two-stage cluster sample was used to randomly select survey wetlands within strata defined by region, wetland density, and wetland surface area. We used 18-m (0.1 ha) fixed radius circular-plots to survey birds in 412 semipermanent wetlands during the summers of 1995 and 1996. Variation in habitat use by pied-billed grebes (Podilymbus podiceps) and yellow-headed blackbirds (Xanthocephalus xanthocephalus), two sedentary species that rarely exploit resources outside the vicinity of nest wetlands, was explained solely by within-patch variation. Yellow-headed blackbirds were a cosmopolitan species that commonly nested in small wetlands, whereas pied-billed grebes were an area-sensitive species that used larger wetlands regardless of landscape pattern. Area requirements for black terns (Chlidonias niger), a vagile species that typically forages up to 4 km away from the nest wetland, fluctuated in response to landscape structure. Black tern area requirements were small (6.5 ha) in heterogeneous landscapes compared to those in homogeneous landscapes (15.4–32.6 ha). Low wetland density landscapes composed of small wetlands, where few nesting wetlands occurred and potential food sources were spread over large distances, were not widely used by black terns. Landscape-level measurements related to black tern occurrence extended past relationships between wetlands into the surrounding matrix. Black terns were more likely to occur in landscapes where grasslands had not been tilled for agricultural production. Our findings represent empirical evidence that characteristics of entire landscapes, rather than individual patches, must be quantified to assess habitat suitability for wide-ranging species that use resources over large areas. 相似文献