966 resultados para pollen pattern


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作者通过实地调查,栽培观察,大量查阅标本,对国产贝母属(Fritillaria L.)的形态性状作了深入的分析,认为贝母属中植株大小,茎生叶先端卷曲与否,花的数目、花梗的长短、花被片颜色等性状易受生境的影响;而鳞茎所具鳞片的数目,植株最下一轮叶的形状及排列,花部蜜腺的形状,花柱柱头的分裂程度,雄蕊花丝在发育完后的长短,蒴果的形状等性状受生境的影响较小,但在栽培情况下,这些性状有时也会发生变化.此外,作者首次报道了部分国产贝母属种类的核型和花粉形态.在此基础上对我国贝母属进行了系统整理,将正式发表的138个分类名称(包括80个种、52个变种、5个变型、1个栽培变型)归并成24种l变种,并对国产贝母组(Seclion Fritillaria)的种间关系作了初步探讨;同时,对该属的次级分类也作了修订.根据有关,F.karelinii花粉学和细胞学资料,以及邻近4个种的形态特征及分布特点,我们支持J.G..Baker(1874)的观点将该类群保留在贝母属内而不同意A.S.Lozin-Lozinskaya(1935),A.Takhtajan(1987)将其单立成属也不同意W.B.Turrill &J.R.Sealy(1980)将其并入贝母组(Sect.Fritillaria),而将该类群做为贝母属中的一个新组——砂贝母组(Sect.Rhinopetalum (Fish. ex Alex.) Y.B.Luo).并认为该组与贝母组关系较近.作者通过上述工作及查阅世界各地有关贝母属的文献,认为贝母属内最原始的类群是Sect. Fritillaria,而Sect.Petillium,Sect.Rhinopetalum和Sect.Theresia是演化水平中等的类群.Sect.Liliorhiza则是演化水平最高的一类.通过对该属组(Section)级及种级分布式样的分析,认为伊朗一土兰区不仅是组的多度中心,并且也是多样化中心;在种级水平上,地中海区是分布的多度中心,而种级多样化中心则在伊朗一土兰区;此外,在伊朗一土兰区还保留着一些较原始的类群,因而,该区可能是贝母属的起源中心,最后,作者对贝母属的起源时间、散布途径及现代分布格局形成的原因进行了初步探讨.

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EXTRACT (SEE PDF FOR FULL ABSTRACT): Pollen from the upper 2.75 m of a core taken 200 km west of the Golfo de Guayaquil, Ecuador (Trident 163-13, 3° S, 84° W, 3,000 m water depth) documents changes in Andean vegetation and climate of the Cordillera Occidental for ~17,000 years before and after the last glacial maximum.

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作者用扫描电镜、透射电镜和组织化学方法研究了甘蓝型油菜(Brassica napus L.)花粉和柱头的发育及相互作用,得到了如下结果: 一.甘蓝型油菜具有典型的同型孢子体自交不亲和性(Homomorphic and sporophytic self-incompatibility)。自花授粉后,部分花粉粘住在乳突细胞表面,随后萌发出花粉管,花粉管生长受阻于乳突细胞,花粉管表现出各种异常形态,缠绕卷曲(Coiled pattern),顶端膨大成基足状(pad-Like swelling),花粉管二叉分枝(dichotomous branching Pollen tubes),花粉管相互连接(connections of pollen tubes),有的花粉粒还形成两个花粉管。 二.不同时期的乳突细胞的扫描电镜观察表明: 开花前6—7天 乳突细胞壁内陷,柱头中央有一沟槽; 开花前4—5天 乳突细胞被有孔的块状物覆盖; 开花前2—3天 覆盖物消失,壁表面只剩下波状纹或小凹; 开花前l - 2天 乳突细胞充分吸水膨胀,呈指状,排列疏松,细胞壁上有一些小颗粒。此时的乳突细胞已发育成熟。 三.不亲和授粉时,花粉和乳突细胞均有强烈的胼胝质荧光。 四.乳突细胞的组织化学特点:缺乏淀粉积累,细胞壁和细胞质中有过氧化物酶活性。 五.乳突细胞的超微结构特点:细胞壁分为三层,蜡质层、角质层和纤维素层。粗面内质网成群分布在细胞壁附近,并以及泡形式向细胞壁分泌物质。缺乏质体,细胞核位于乳突细胞基部,细胞中央为大液泡占据。 六.花粉的超微结构发育特点:单核花粉已发育出内壁和外壁,外壁内层不明显。细胞核位于中央。细胞质浓厚,缺乏层膜结构而积累大量淀粉粒的质体存在于细胞质中。其他细胞器不发达。两细胞花粉时期,花粉壁接受乌氏体转运的孢粉素和含油体转运的脂类物质。生殖细胞没有壁,悬浮在营养细胞的细胞质中。细胞核大,细胞质稀薄,只有一些嵴不明显的线粒体。营养细胞的核显著,细胞质浓厚,线粒体发达,质体内部的淀粉消失,转变成嗜饿小体。内质网短而粗,遍布于细胞质中,高尔基体缺乏。 七.绒毡层积极参与了花粉外壁的建成。首先,它通过分泌作用把物质(可能是蛋白质)转移到单核花粉的腔隙中或在它后期滚解后,由分布在二细胞花粉间的粗面内质网合成蛋白质,转移到花粉壁内。其次,绒毡层细胞的质体层膜形成许多造油小体,至二胞花粉时,造油小体进入壁的柱状层,参与花粉鞘形成。第三,绒毡层细胞形成许多乌氏体,花粉发育后期,乌氏体与花粉外壁接触,将孢粉素转移到花粉外壁上。

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Spatial pattern metrics have routinely been applied to characterize and quantify structural features of terrestrial landscapes and have demonstrated great utility in landscape ecology and conservation planning. The important role of spatial structure in ecology and management is now commonly recognized, and recent advances in marine remote sensing technology have facilitated the application of spatial pattern metrics to the marine environment. However, it is not yet clear whether concepts, metrics, and statistical techniques developed for terrestrial ecosystems are relevant for marine species and seascapes. To address this gap in our knowledge, we reviewed, synthesized, and evaluated the utility and application of spatial pattern metrics in the marine science literature over the past 30 yr (1980 to 2010). In total, 23 studies characterized seascape structure, of which 17 quantified spatial patterns using a 2-dimensional patch-mosaic model and 5 used a continuously varying 3-dimensional surface model. Most seascape studies followed terrestrial-based studies in their search for ecological patterns and applied or modified existing metrics. Only 1 truly unique metric was found (hydrodynamic aperture applied to Pacific atolls). While there are still relatively few studies using spatial pattern metrics in the marine environment, they have suffered from similar misuse as reported for terrestrial studies, such as the lack of a priori considerations or the problem of collinearity between metrics. Spatial pattern metrics offer great potential for ecological research and environmental management in marine systems, and future studies should focus on (1) the dynamic boundary between the land and sea; (2) quantifying 3-dimensional spatial patterns; and (3) assessing and monitoring seascape change.