DEVELOPMENTAL FEATURES OF THE SPERMATOGENOUS CELL IN GINKGO BILOBA

A “double-blepharoplast” originates de novo in the spermatogenous cell of Ginkgo biloba L. Initially, the double-blepharoplast consists of two opposing hemispherical bodies comprised of densely staining material. The two blepharoplasts seemingly are pushed apart by the formation of densely packed fibrils which are oriented perpendicular to the distal, rounded edges of the two future blepharoplasts. As the latter move apart, each one develops lightly staining channels which are often organized in a hub and spoke configuration (procentrioles). Microtubules extend from the blepharoplasts as the latter move to their final position in the cell, and centrioles (probasal bodies) become organized at the periphery of each blepharoplast. Two large “osmiophilic globules,” conspicuous entities close to the nucleus of the mature spermatogenous cell, arise de novo. A fibrillogranular body in the cytoplasm, always closely associated with the nucleus, also arises de novo.     

银杏精子细胞生毛体及其它细胞器的超微结构

生毛体与嗜锇颗粒是银杏 (Ginkgobiloba)精子细胞中最具有标志性的结构。生毛体是细胞质内一直径为 3～ 4μm的圆球形结构 ,它由一个电子致密的核心和由此向周边发散出的辐射状中心粒组成 ,致密核心上具有微管结构的弱电子染色区域 ,并有微管从生毛体延伸到细胞质。嗜锇颗粒直径为 1 0～ 2 0μm,呈圆球状 ,位于生毛体和细胞核之间 ,其相对的另一侧存在纤维颗粒体。在精子细胞质内 ,特别是嗜锇颗粒和生毛体周围线粒体、质体、内质网、高尔基体等细胞器丰富。银杏精子细胞核较大 ,在细胞核内 ,核仁结构呈球形 ,电子染色致密的颗粒区在周围 ,而纤维组分则在圆球的中间。在核膜表面布满了分布不均匀的核孔复合体。     

DIVISION OF THE GENERATIVE CELL AND LATE DEVELOPMENT IN THE MALE GAMETOPHYTE OF GINKGO BILOBA

Division of the generative cell in the male gametophyte of Ginkgo biloba to yield the sterile cell and spermatogenous cell was examined in vivo and in vitro. Evidence is presented in support of a new interpretation of development in which the sterile cell and spermatogenous cell arise from an unusual anticlinal ringlike division of the generative cell. This type of cell division is only known to occur during antheridial development in leptosporangiate ferns and stomatal development among certain ferns in the Schizaeaceae and Polypodiaceae. The strong similarities in development and cell arrangement within the male gametophytes of cycads and Ginkgo suggest that division of the generative cell in cycads may be the same as in Ginkgo. Although the ringlike (conically annular) divisions in the antheridia of leptosporangiate ferns and the male gametophytes of Ginkgo (and probably cycads) are remarkably similar and result in the production of a central spermatogenous cell, it is conjectural as to whether these patterns represent a striking convergence or evolutionary homology.     

小麦条锈菌吸器母细胞超微结构的研究

本文利唱电镜技术研究了小麦条锈菌吸器母细胞的超微特征。观察发现,小麦条锈菌吸器母细胞大部位于胞间菌丝的顶部,但也可形成于两菌丝细胞间,同一菌丝细胞上可着生多个吸器母细胞,吸器母细胞的多核现象较为普遍。吸器母细胞壁由6层组成,而其隔膜可分辩为4层。细泡化学染色结果表明隔膜突中含有多糖类物质,吸器母细胞隔膜突的出现和消失与吸器的发育密切相关。本文结果表明小麦条锈菌吸器母细胞的一些超微特征明显不同于其它锈菌。     

LIGHT MICROSCOPE AND ULTRASTRUCTURAL STUDIES OF THE MALE GAMETOPHYTE IN GINKGO BILOBA: THE SPERMATOGENOUS CELL

A light microscope and ultrastructural study was made of the pollen tube of Ginkgo biloba, with special emphasis given to the spermatogenous cell that gives rise to two motile sperms. Just prior to the mitotic division that results in the formation of two sperms, the spermatogenous cell consists of a large nucleus, two blepharoplasts, two large osmiophilic globules, and a conspicuous lipo-protein body. Other organelles in the cytoplasm include numerous electron-dense proplastids (with some lamellar development), mitochondria, small vacuoles, and lipid bodies. Ribosomes are present in abundance, but endoplasmic reticulum and dictyosomes are sparse. The nucleus, prior to mitosis, is relatively Feulgen-negative, due undoubtedly to the diffuse distribution of DNA. Each blepharoplast, the main organelle of interest, is nearly spherical, measures 3.5–4.5 μm in diam, and supports about 1,000 probasal bodies. The interior of a blepharoplast consists of an electron-dense matrix and of less dense regions which appear to be infiltrated by a network of microtubules. Each probasal body is composed of a cylinder of nine separate tubules (singlets) at the basal or proximal end. The cylinder becomes elaborated distally into nine pairs of subtubules (doublets) and then into nine sets of subtubules (triplets). A central tubule is present the entire length of the probasal body. Some of the subtubules, as well as microtubules from the interior of the blepharoplast, extend into the cytoplasm and probably constitute the “astral rays” as seen with the light microscope. Comparisons are made with other published accounts of the organization of blepharoplasts in plants and of centrosomes and centrioles in animals.     

ANASTOMOSES IN THE VENATION OF GINKGO BILOBA

Arnott , Howard J. (Northwestern U., Evanston, Ill.) Anastomoses in the venation of Ginkgo biloba. Amer. Jour. Bot. 46(6): 405–411. Illus. 1959.—Although the vasculature of the lamina of Ginkgo biloba has been described as open dichotomous and devoid of anastomoses, vein unions were found in a survey of 1065 leaves collected from both long and short shoots of 11 trees. When studied by directing a strong light through the lamina and by clearings, 9.9% of the leaves possessed 1 or more anastomoses. Long shoot-leaves showed 13.4% anastomoses while short shoot-leaves showed 8.2% anastomoses. Multiple anastomoses were found in almost half of the leaves bearing anastomoses. In the 105 leaves having vein unions, 163 anastomoses were counted. These anastomoses could be grouped into 4 types which are easily distinguished by the number of dichotomies involved and by the presence or absence of dichotomies above the point of vein union. Other deviations were found from the “normal” venation pattern; these consisted of unconnected veins, veins anastomosed marginally but unconnected basally, and veins ending a considerable distance from the margin. It was speculated that the anastomoses found in Ginkgo biloba are of a simple, archaic type and are apparently analogous to the anastomoses in the leaves of certain ferns and in the leaflets of various cycads. The evolutionary significance of these anastomoses must be assessed by a broad study of venation patterns in the seed-plants.     

杉木花粉母细胞减数分裂前期联会复合体的超微结构

应用透射电子显微镜观察了杉木花粉母细胞减数分裂前期的联会复合体。发现杉木花粉母细胞减数分裂的联会复合体中央结构是由两条暗带及一条明带组成,而不是一般描述的一条暗带。     

PHOTOSYNTHESIS IN THE FEMALE GAMETOPHYTE OF GINKGO BILOBA

The female gametophyte of Ginkgo biloba is the only seed plant gametophyte known to contain chlorophyll. Measurements of photosynthetically active radiation (PAR) indicate that a gametophyte growing within an ovule can receive significant quantities of light (70 μmol photons m^–2 s^–1). Under the conditions of our experiments, whole gametophytes dissected free from ovules were capable of gross photosynthesis, but not net photosynthesis. On a dry wt basis, the maximum rate of carbon fixation under near saturating light intensities was 3.64 × 10^–3 μmol CO₂g^–1 s^–1. The unique ability of the female gametophyte of Ginkgo biloba to produce chlorophyll and engage in photosynthesis appears to result from its exposure to sufficient levels of light and a predisposition to react to this stimulus by the development of a functional photosynthetic apparatus.     

银杏外种皮研究进展

银杏(GinkgobilobaL.)为银杏科银杏属多年生落叶乔木,又名白果,是我国特有树种,也是世界上珍贵的药用植物资源。对银杏叶和果的研究,尤其是对银杏叶黄酮的研究,已取得了多项成果〔1,2〕,但对银杏外种皮的研究还不多。银杏外种皮是种子硬壳外面的肉质部分,长期以来,被视为废物丢弃,既浪费资源又污染环境。国内自90年代末,扬州大学、中国药科大学等单位开展了银杏外种皮研究工作,但目前还没有规模生产的产品投向市场〔3〕。笔者在综合检索的基础上对银杏外种皮研究工作作一综述,希望引起对银杏外种皮开发利用工作的广泛重视。1　资源状况目前…     

银杏叶精油的化学成分

采集３－５年银杏苗叶,经常压水蒸汽蒸馏制得浅黄色精油,通过ＧＣ和ＧＣ／ＭＳ鉴定出４４个化学成分,主要由３１．１４％烃类、５．６１％醇类、１．７８％醛类、４６．１７％酮类、５．４１％酸类和１．１％酯类组成。在酮类中以六氢法呢酮含量最高,占１１．１５％,其次为橙花基酮（８．６８％）和β－紫罗兰酮（５．２４％）。     

银杏叶不同生长期总黄酮的含量测定(简报)

木文研究了银杏(Ginkgo biloba L.)不同生长期叶的总黄酮含量,研究结果表明,秋季叶含黄酮量较高,结果株叶总黄酮含量比不结果株高。     

银杏叶的研究开发概况

本文对银杏叶的化学、药理、临床和制剂等进行了综述。     

银杏幼苗死亡原因的探究

造成银杏幼苗死亡的主要原因是日灼、根腐、茎腐以及虫害等。日灼不仅直接导致银杏的幼苗死亡,还可间接诱导茎窝病的发生甚至流行。     

银杏雄株GinNdly全长基因的分离克隆

以银杏栽培品种大佛手(Ginkgo biloba L.cv.Dafushou)雄株为材料,用四月中旬幼嫩的叶片基因组DNA为模板,通过PCR扩增,获得银杏雄株LEAFY(LFY)同源基因GinNdly全长基因。结果分析表明,该全长基因含1493个核苷酸。与文献报道的银杏雌株GinNdly基因相比,碱基数少了三个,对应地氨基酸少一个,核苷酸同源性为99.7％,氨基酸同源性为99.3％。该基因的克隆为在分子水平上研究银杏开花调控机理奠定了良好的基础。     

MEGASPORE WALL ULTRASTRUCTURE IN ISOETES

In Selaginella, megaspore wall ultrastructure (unit morphology and arrangement) is correlated with taxonomic position. In some Pennsylvanian lycopods there is a correlation with dispersal strategy. This study was designed to assess any correlation between habitat preference and wall ultrastructure in Isoetes. Except for a few minor structural correlations, wall ultrastructure appears to be constant in terrestrial, amphibious, and aquatic species of Isoetes. Several distinct sizes of megaspores occur in some megasporangia and correspond to 1) full-size megaspores with siliceous coatings, 2) small megaspores with siliceous coatings, and 3) full-size megaspores without siliceous coatings. The uniformity in wall ultrastructure within modem Isoetes together with the lack of uniformity of fossil isoetalean megaspore wall ultrastructure suggest that the modem species of Isoetes are closely related.     

银杏外种皮中银杏酸的分离方法

本文简单介绍了一种从银杏外种皮中分离银杏酸的方法,使用了皂化和酯化反应为后的两次柱层析分离提供便利条件。