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杨柳科植物染色体数目及其进化的研究(英文) 总被引：1，自引：0，他引：1
本文报道了8种3变种2杂交种杨树的染色体数目,结果均为2n=38,其中3种1杂交种为首次报道。统计了277种杨柳科植物的染色体数目,分析了其可能的进化途径,初步结论如下:(1)现代杨柳科植物是一群具有多个染色体基数、处在不同倍性水平的多倍体系列;(2)其次生基数X_2=19,11,12和14,这些次生基数可能是古多倍体起源的;(3)杨柳科植物染色体的原始基数可能是X=6;(4)现代杨属和钻天柳属植物染色体数目的进化处在同一水平上,即古多倍体水平上;而柳属中大约50％的种进化为次生多倍体,最高为16倍体。绘出了杨柳科植物染色体进化谱,讨论了该科植物染色体基数进化的可能途径。 相似文献
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本文报道了8种3变种2杂交种杨树的染色体数目,结果均为2n=38,其中3种1杂交种为首次报道。统计了277种杨柳科植物的染色体数目,分析了其可能的进化途径,初步结论如下:(1)现代杨柳科植物是一群具有多个染色体基数、处在不同倍性水平的多倍体系列;(2)其次生基数X_2=19,11,12和14,这些次生基数可能是古多倍体起源的;(3)杨柳科植物染色体的原始基数可能是X=6;(4)现代杨属和钻天柳属植物染色体数目的进化处在同一水平上,即古多倍体水平上;而柳属中大约50％的种进化为次生多倍体,最高为16倍体。绘出了杨柳科植物染色体进化谱,讨论了该科植物染色体基数进化的可能途径。 相似文献
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人们在人工合成多倍体及基因组研究时发现,在多倍体合成过程中发生了很多遗传和表观遗传现象。了解和弄清这些遗传和表观遗传现象及其背后的机制,将会使我们对植物进化、新种形成以及杂种优势的机制有更深一步的了解。 相似文献
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城市拆迁中失地农民的社会保障问题研究——以柳州市城中区河东村为例 总被引：2，自引：2，他引：0
在对柳州市河东村随机抽取的40户失地农民进行实际调研的基础上,阐述了柳州市城中区河东村征地情况与失地农民的社会保障现状。分析了城市拆迁中失地农民的社会保障问题及失地农民的迫切需要：村民失地后存在的主要问题是拆迁安置标准偏低,难以保持原有的生活水平;生活来源发生改变,但没有建立相应的保障机制;失地农民的迫切需要是更多稳定的工作和稳定的收入来源。针对目前状况,提出了建立失地农民社会保障机制的对策与建议,分别是建立失地农民的最低生活保障机制;建立失地农民的养老保障机制;建立失地农民的医疗保障机制;为失地农民提供就业和培训的机会,千方百计为失地农民广辟就业渠道,构建失地农民就业保障体系。 相似文献
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Immunological approaches to the nervous system 总被引：1，自引：0，他引：1
L F Reichardt 《Science (New York, N.Y.)》1984,225(4668):1294-1299
Immunology has had a major impact on neurobiology, expanding dramatically the number of subjects amenable to investigation. Studies with antibodies to neuropeptides, transmitters, and transmitter enzymes have disclosed a great heterogeneity among neurons and have provided clues for interpreting anatomical connections. Monoclonal antibodies are being used to identify functionally related subpopulations of neurons and cell lineages in development and to study mechanisms by which axons grow along stereotypic pathways to reach their targets. Other antibodies have identified molecules that appear to participate in cell aggregation, cell migration, cell position, and axon growth. Antibodies have revealed that many proteins are concentrated in anatomically distinct regions of the neuron. Moreover, these studies have suggested that individual proteins have different antigenic epitopes shielded or modified in different parts of the same neuron. Antibodies to membrane proteins crucial for neuronal function, such as ion pumps, ion-selective channels, and receptors, have been used to map their distributions and to study their structures at high resolution. 相似文献
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Low temperature wheat genotypes are a group of wheat with a slightly low canopy （plant） temperature, and the research on their biological characters and utilization in wheat breeding has been done at home and abroad for more than 20 years, and has made great progress. The research contents and advances include the following respects： Wheat genotypes with slightly low canopy temperature have been verified to exist in nature; these wheat genotypes, which present cold temperature, are superior to conventional wheat materials in some important biological characters and particularly prominently in metabolic function and cellular structure; when they suffer stresses such as drought, high temperature and overcast and rainy weather, they still retain their superiority in some of their important biological characters and therefore have a wide range of ecological adaptability; slightly low canopy temperatures of these genotypes are closely correlated with low temperatures of their second heat sources and their vigorous plants; since their low canopy temperatures can be inherited, they can exert favorable influence on the temperatures of their offspring while crossing with other wheat materials, and in particular, the discovery of cold-source wheat as a contributor to low temperature, has further formed good conditions for breeding high and stable quality low temperature wheat varieties with a high and stable yield. Thus, low temperature wheat genotypes are of great research importance and have great prospects. 相似文献
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VAN Slyke DD 《Science (New York, N.Y.)》1942,95(2463):259-263
We have followed the amino acids from their entrance into the alimentary tract in the form of food proteins through the successive steps of digestion, absorption into the blood stream and passage from the blood stream into the tissues, where they are concentrated by some unknown mechanism to many times their concentration in the blood plasma. We have seen something of the way in which certain of the amino acids can be transformed into one another in the body or synthesized from ammonia and keto acids. However, we have had to admit that our bodies can form in such ways only about half of the different amino acids that are required, and that the other half must be made for us by plants, bacteria or other organisms which have greater synthetic powers than we. And finally we have seen something of the manifold fates of the amino acids after they have entered our tissues; how they may be destroyed and their nitrogenous parts turned into urea in the liver before it is possible to put them to their more specialized uses, how their carbon fractions can be used to form glucose, how they may sacrifice themselves to protect us from toxic products, how they can serve as source material for certain vitamins, hormones and other compounds with physiological functions still to be identified, and how finally those amino acids which are not deflected to these various fates may enter into the proteins of the tissues and become for a time parts of our living structures. 相似文献
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化解金融危机下企业财务风险的路径 总被引：1，自引：0，他引：1
在全球金融危机的背景下,企业正面临着严重的财务困境。面对这一困境,分析金融危机下企业财务风险的主要表现,探索化解企业金融危机的财务路径,制定符合自身长远目标的财务战略,为我国企业化解金融危机下的财务风险提供参考。 相似文献
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本文利用古兜山阔叶林的标准地调查资料,对其进行主要群落类型的划分和结构特征的分析。古兜山阔叶林是属于半热带沿海湿润季风区域的热带雨林性常绿季雨林,正处于旺盛生长的中幼龄阶段,植物种类繁多和森林资源丰富,但次生性较强,结构复杂,群落类型较多,共有八个主要群落类型。 相似文献
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李强 《安徽农业大学学报》2023,32(1):86-95
创新型中小企业具有更高的获得融资的概率,但在融资额度上并没有体现出明显的差异性。中小企业的创新产出越多,创新质量越高,获得融资的概率和融资额度就越高。从不同行业的样本来看,技术密集型的行业中创新型中小企业更容易获得融资,非技术密集型行业中没有显著的证据表明创新型中小企业更容易获得融资。从不同地区的样本来看,处在创新集聚区内的创新型中小企业并没有体现出明显的更容易获得融资的现象。 相似文献
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基于对4所高校学生进行的问卷调查分析,采用二元Logit模型,研究大学生的返乡下乡创业意愿因素,提出促进大学生返乡下乡创业的相关建议。实证研究结果表明,37.7%的大学生有进行返乡下乡创业的意愿,其中:大学生的性别、是否为独生子女以及文化程度对大学生返乡下乡创业具有显著影响,而文化程度较低的大学生返乡下乡创业意愿更强。家庭特征对大学生返乡下乡创业意愿有显著正向影响,父母有过创业经历的和家庭经济条件较好的大学生返乡下乡创业意愿会更强。创业环境对大学生返乡下乡创业意愿具有显著性影响,创业政策越优惠、创业设施越便利,大学生返乡下乡创业意愿越强。愿意放弃舒适的环境、愿意承担创业过程中遇到的风险以及具备强烈责任感的大学生对返乡下乡创业的意愿更强,大学生创业自我认知对返乡下乡创业意愿具有显著性影响。 相似文献
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食用菌病毒作为真菌病毒的一部分,有多种形态,多数为分段的dsRNA基因组形式,也有正义单链RNA,其中主要编码衣壳蛋白和依赖于RNA的RNA聚合酶。目前,已有食用菌病毒基因组序列被测定,并分析了其基因组的结构与功能。dsRNA技术和酶学方法使dsRNA食用菌病毒的研究很容易的深入到分子水平,特别是dsRNA技术,已在平菇得到应用。食用菌病毒有其特有的复制模式,分两个阶段进行,其原始的起源可能是自我复制的细胞内mRNA,因为细胞内mRNA明显的原始性。综述了上述内容,并对食用菌病毒与其寄主在共进化这方面做了进一步展望,对食用菌病毒的进一步研究,以及选育脱毒菌株,都有重要的意义。 相似文献
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殷峻巍 《安徽农业大学学报》2001,(4):107-108
婚姻、爱情一直是新时期女性文学极力彰显的主题。从执着追求爱情到毅然放弃神圣情感，从为了维持生活现状懒得离婚到为了寻觅人间真爱摒弃婚姻，女作家们以细腻的笔触描摹了处于情爱漩涡中的男女主人公们的婚恋心态及由此表现出的行为方式、价值观念，从而构成了新时期文学创作中一个独特的景观。 相似文献