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关键词： 大叶榉   光叶榉   大果榉(小叶榉)   生物学特性  

摘要： 比较研究了分布于我国的3个榉属种:大叶榉、光叶榉和大果榉(小叶榉)的生物学特性,发现它们虽然在许多性状上都表现出了较大的相似性,但是在形态特征和生物学特性等方面存在较大的差异。主要表现在树干颜色、叶质、冬芽的形状以及果实的形态和大小等方面。

关键词： 农业可持续发展   现代化进程   植物生物学   第二届   论坛   三角   专题   科技   科学技术协会   论文摘要  

关键词： 科技论坛   优秀论文   植物生物学   农业   青年  

关键词： 姜科   闭鞘姜科   繁育系统   传粉生物学   进展  

摘要： 综述了姜科Zingiberaceae植物繁育系统和传粉生物学方面的研究及其进展。姜科有50余属1500多种,是一个泛热带分布的、动物传粉的单子叶植物大科。姜科植物中存在着雌花两性花异株、雄花两性花同株、花柱卷曲性、雄性先熟、自交不亲和等多种性表达方式和花部机制。姜科植物重要的传粉动物包括各种蜂类、天蛾、蝴蝶、鸟类等,不同的传粉动物对应不同的花部特征。在相对有限的研究中,姜科植物展现出了一些独特的传粉和繁育机制,在豆蔻属Amomum、山姜属Alpinia等植物中发现的花柱卷曲性被认为是植物界中一种独特的促进异交的行为机制,在对黄花大苞姜Caulokaempferiacoenobialis的研究中发现了植物界中一种全新的花粉滑动自花传粉机制,这些新的研究和发现丰富了我们对姜科植物传粉和繁育系统多样性的认识。本文提出了今后姜科植物繁殖生物学研究的建议:对更多未知姜科植物类群的传粉和繁育系统进行研究;从系统发育的角度开展姜科不同类群植物的传粉和繁育系统的演化研究;对花柱卷曲性这一独特的性多态现象开展全面深入的研究。

关键词： germination   pollination   reproductive investment   seed dispersal   sex ratio  

摘要： Fourteen wild species of shrubs and trees in the dioecious genus Ilex occur in Hong Kong (22 degrees N, 114 degrees E). All species flowered and formed fruits once each year. Sex ratios at flowering were male biased in all but one large population studied and, in most cases, this bias could not be explained by earlier flowering in males or higher female mortality. Apis cerana accounted for > 87% of flower visits in all species and there was a significant positive relationship across species between the number of visits per flower per hour and the estimated mean number of flowers on a plant. The large green fruits of Ilexachapaensis Merr. were consumed only by masked palm civets, Paguma larvata, while the red or black fruits of other species were consumed by birds. The rate of fruit removal across species was positively related to sugar content and negatively related to phenolic and saponin contents. The mean number of pyrenes per fruit was 4.0-6.2 and the mean percentage of pyrenes containing seeds was 49%-90%. Most embryos were immature (heart shaped) at fruit maturity, but < 50% of embryos developed further in some species. Floral investment was 0.93-5.84 times higher in male plants, but total reproductive investment was 0.62-8.3 higher in females.

关键词： epigenetics   DNA methylation   histones   chromatin   RNA   paramutation   transgenes   silencing   gene expression  

摘要： Background Epigenetics has rapidly evolved in the past decade to form an exciting new branch of biology. In modern terms, 'epigenetics' studies molecular pathways regulating how the genes are packaged in the chromosome and expressed, with effects that are heritable between cell divisions and even across generations. Context Epigenetic mechanisms often conflict with Mendelian models of genetics, and many components of the epigenetic systems in plants appeared anomalous. However, it is now clear that these systems govern how the entire genome operates and evolves. Scope In the first part of a two-part review, how epigenetic systems in plants were elucidated is addressed. Also there is a discussion on how the different components of the epigenetic system-regulating DNA methylation, histones and their post-translational modification, and pathways recognizing aberrant transcripts-may work together.

关键词： soil aggregate stability   glomalin-related soil protein   grasslands   invasion ecology   Aegilops triuncialis   Centaurea solstitialis  

摘要： Plant invasions alter soil microbial community composition;this study examined whether invasion-induced changes in the soil microbial community were reflected in soil aggregation, an ecosystem property strongly influenced by microorganisms. Soil aggregation is regulated by many biological factors including roots, arbuscular mycorrhizal fungal hyphae, and microbially-derived carbon compounds. We measured root biomass, fungal-derived glomalin-related soil protein (GRSP), and aggregate mean weight diameter in serpentine soils dominated by an invasive plant (Aegilops triuncialis (goatgrass) or Centaurea solstitialis (yellow starthistle)), or by native plants (Lasthenia californica and Plantago erecta, or Hemizonia congesta). Root biomass tended to increase in invaded soils. GRSP concentrations were lower in goatgrass-dominated soils than native soils. In contrast, starthistle dominated soil contained a higher amount of one fraction of GRSP, easily extractable immunoreactive soil protein (EE-IRSP) and a lower amount of another GRSP fraction, easily extractible Bradford reactive soil protein (EE-BRSP). Soil aggregation increased with goatgrass invasion, but did not increase with starthistle invasion. In highly aggregated serpentine soils, small increases in soil aggregation accompanying plant invasion were not related to changes in GRSP and likely have limited ecological significance. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： PLANT diseases   NONFICTION  

摘要： The article reviews the book 'Fungal Disease Resistance in Plants: Biochemistry, Molecular Biology and Genetic Engineering,' Zamir K. Punja.

关键词： .plant species   Medical Sciences   DGGE   Bacterial Communities   rhizosphere soil   community composition   Grassland Soils   Links between Plant   rhizoplane communities  

摘要： Molecular analysis of grassland rhizosphere soil has demonstrated complex and diverse bacterial communities, with resultant difficulties in detecting links between plant and bacterial communities. These studies have, however, analyzed "bulk" rhizosphere soil, rather than rhizoplane communities, which interact most closely with plants through utilization of root exudates. The aim of this study was to test the hypothesis that plant species was a major driver for bacterial rhizoplane community composition on individual plant roots. DNA extracted from individual roots was used to determine plant identity, by analysis of the plastid tRNA leucine (trnL) UAA gene intron, and plant-related bacterial communities. Bacterial communities were characterized by analysis of PCR-amplified 16S rRNA genes using two fingerprinting methods: terminal restriction fragment length polymorphisms (T-RFLP) and denaturing gradient gel electrophoresis (DGGE). Links between plant and bacterial rhizoplane communities could not be detected by visual examination of T-RFLP patterns or DGGE banding profiles. Statistical analysis of fingerprint patterns did not reveal a relationship between bacterial community composition and plant species but did demonstrate an influence of plant community composition. The data also indicated that topography and other, uncharacterized, environmental factors are important in driving bacterial community composition in grassland soils. T-RFLP had greater potential resolving power than DGGE, but findings from the two methods were not significantly different.