Structural Modifications of the Female Gametophyte Induced by Temperature in Nicotiana tabacum

Effect of environmental conditions on formation of Nicotiana tabacum L. megagametophyte was studied. It was established, that unfavorable temperatures can specifically modify the structure of embryo sacs (ES). At low temperature (9/5 °C), ES with a reduced number of cells or with egg-like synergide(s) can be formed; at high variable (40/25 °C) or constant (37 °C) temperatures, ES with excessive numbers of cells or with synergide-like egg cells arise. Total frequencies of the changed ES patterns varied from 8 up to 35 % per plant and depended on the plant genotype and conditions of exposure. This revised version was published online in July 2006 with corrections to the Cover Date.     

水稻胚囊壁的形成与发育观察

通过透射电镜对水稻(Oryza sativa L.)功能大孢子形成开始至胚囊成熟期间胚囊壁的形成与发育进行观察,结果表明:水稻胚囊壁是在原有功能大孢子壁的基础上,通过与其周围退化珠心细胞留下的壁相叠合,使壁加厚。功能大孢子近合点端壁存在胞间连丝,其中个别胞间连丝可保留到八核胚囊。胚囊壁上内突最早于四核胚囊近珠孔端发生。八核胚囊形成后,内突的发育在胚囊不同的细胞中表现不同,其中以中央细胞最具特点,表现为先在中央细胞与珠心相接的近珠孔端和近合点端两个区域的胚囊壁上形成,以后近珠孔端胚囊壁上的内突大量增加,而近合点端的却增加不明显,中部胚囊壁上的内突出现的时间相对较晚。到胚囊成熟时,近珠孔端胚囊壁上内突的分布密度最大,中部次之,近合点端的最小,三个区域上内突的形态各异。反足细胞与珠心相接的胚囊壁上内突的形成时间较早,但以后的发育却相对缓慢,数量增加不明显。2个助细胞交界处胚囊壁上的丝状器在胚囊未明显膨大时已形成。卵细胞除在与助细胞交界处的壁外,其它部位不形成明显的内突结构。     

The uptake of macromolecular materials in the hindgut of viviparous rockfish embryos

Regions of the gut of near-term embryos and new-born larvae of the viviparous rockfish Sebastes taczanowskii were examined histologically and immunohistochemically in order to ascertain whether they possessed the potential to absorb intact macromolecules. Compared with the hindgut of larvae 24 h after parturition, that of near-term embryos (stage 31) was found to be markedly hypertrophied and to react positively when tested for the presence of eosinophilic materials and with antibodies raised against extracts of the rockfish yolk (ab.a-E). In addition, near-term embryos incubated in Ringer solution containing 1% bovine serum albumin appeared to accumulate the protein within the epithelium of the hindgut. Furthermore, as confirmed by immunodiffusion analysis, the ovarian fluid contained materials which reacted positively to ab.a-E. These results suggest that ingestion of intact macromolecules occurs during the late embryonic stages and that the yolk-like substances detected within the hindgut epithelium of such embryos may be derived from the bathing ovarian fluid.     

植物雌配子体发育研究进展

高等植物雌配子体的形成涉及孢原细胞和大孢子母细胞的确立与分化、大孢子发生、功能大孢子以及胚囊的形成和发育等多种复杂调控过程。随着当代生物技术及功能基因组学的发展,近年对雌配子体发育的研究已从细胞学描述逐渐过渡到对基因和发育调控分子机理的探索。以拟南芥、水稻和玉米等模式植物为材料进行的相关研究,丰富了人们对于植物雌配子体和其它有性生殖过程遗传调控机理的认识。本文着重阐述了植物雌配子体发生和发育过程,并综述了这一领域最新研究进展。     

非洲狼尾草未受精无孢子生殖胚囊退化研究

为理解植物无孢子生殖胚囊未受精条件下的退化,对无孢子生殖植物非洲狼尾草未受精成熟胚囊中央细胞退化做了细胞形态学研究。没有受精的中央细胞退化时最显著的特点是细胞核产生核膜囊泡。核膜囊泡有两种类型:单层膜的囊泡和双层膜的囊泡,单层膜囊泡在细胞质中,双层膜囊泡在细胞核内。核膜囊泡有两种发生方式:1)核膜的外膜向细胞质一侧膨胀产生囊泡,囊泡进入细胞质;2)核膜向核内凹陷形成囊泡,囊泡进入细胞核。核膜囊泡类型与产生方式密切关联。核膜囊泡吞噬并消化包括线粒体在内的细胞质和核质。     

几种植物生活胚囊的分离与鉴定

向日葵、金鱼草和烟草的成熟胚囊以及前两种植物受精后具原胚和胚乳的胚囊均已从新鲜胚珠中分离出来。干涉差显微观察与 H33258荧光显微技术表明它们确系保持了细胞结构和含有丰富内含物的完整胚囊。荧光素二醋酸酯的显微鉴定进一步证明它们是有生活力的。     

Endogenous β-d-galactoside binding lectin during the expansion of the yolk sac in the developing chick embryo

Summary A lectin with an affinity for -d-galactoside-containing saccharides is present in the developing yolk sac from the chick embryo at stages from 2 to 7 days of incubation. This activity is present in the area vitellina (less differentiated) and the area vasculosa (more differentiated). In both areas, lectin activity increases significantly during the spreading of the yolk sac up to 5 days of incubation. At all of the stages studied lectin activity was significantly higher in the area vasculosa, as compared to the area vitellina.Lectins were purified by affinity chromatography and examined by SDS-PAGE. Under reducing conditions two components are evident. A more prominent band of subunit molecular weight of 14,200±100 for the area vitellina and 13,700±300 for the area vasculosa and a second band with molecular weight of about 68,000±700 and 68,000±1,200 for the area vitellina and area vasculosa respectively, were observed. The -d-galactoside-binding lectin appears to be similar if not identical to that of the early chick blastoderm.     

Fertilization in Torenia fournieri: Actin organization and nuclear behavior in the central cell and primary endosperm

Studies of the living embryo sacs of Torenia fournieri reveal that the actin cytoskeleton undergoes dramatic changes that correlate with nuclear migration within the central cell and the primary endosperm. Before pollination, actin filaments appear as short bundles randomly distributed in the cortex of the central cell. Two days after anthesis, they become organized into a distinct actin network. At this stage the secondary nucleus, which is located in the central region of the central cell, possesses an associated array of short actin filaments. Soon after pollination, the actin filaments become fragmented in the micropylar end and the secondary nucleus is located next to the egg apparatus. After fertilization, the primary endosperm nucleus moves away from the egg cell and actin filaments reorganize into a prominent network in the cytoplasm of the primary endosperm. Disruption of the actin cytoskeleton with latrunculin A and cytochalasin B indicates that actin is involved in the migration of the nucleus in the central cell. Our data also suggest that the dynamics of actin cytoskeleton may be responsible for the reorganization of the central cell and primary endosperm cytoplasm during fertilization.     

Ultrastructure of the pre-implantation shark yolk sac placenta

During ontogeny, the yolk sac of viviparous sharks differentiates into a yolk sac placenta which functions in gas exchange and hematrophic nutrient transport. The pre-implantation yolk sac functions in respiration and yolk absorption. In a 10.0 cm embryo, the yolk sac consists of six layers, viz. (1) somatic ectoderm; (2) somatic mesoderm; (3) extraembryonic coelom; (4) capillaries; (5) endoderm; and (6) yolk syncytium. The epithelial ectoderm is a simple cuboidal epithelium possessing the normal complement of cytoplasmic organelles. The endoplasmic cisternae are dilated and vesicular. The epithelium rests upon a basal lamina below which is a collagenous stroma that contains dense bodies of varying diameter. They have a dense marginal zone, a less dense core, and a dense center. The squamous mesoderm has many pinocytotic caveolae. The capillary endothelium is adjacent to the mesoderm and is delimited by a basal lamina. The endoderm contains yolk degradation vesicles whose contents range from pale to dense. The yolk syncytium contains many morphologically diverse yolk granules in all phases of degradation. Concentric membrane lamellae form around yolk bodies as the main yolk granules begin to be degraded. During degradation, yolk platelets exhibit a vesicular configuration.     

水稻雌配子体发生过程中胚囊内微管骨架变化的进一步研究(英文)

用PEG包埋切片法及荧光抗体标记技术对水稻 (OryzasativaL .)雌配子体发生过程中微管骨架的变化进一步研究。经PEG包埋切片技术处理的胚囊内的微管结构能够保持得比较完整 ,特别是在一些较大和成熟的胚囊内 ,效果更佳 ,微管清晰度高。对雌配子体发生过程中的一些主要时期的微管结构变化作了详尽描述和分析 (包括 :单核、二核、四核、八核和成熟胚囊时期 )。发现了一些新的微管结构 ,如在中央细胞中有纵向微管 ,这些微管在两个极核移至中央部位时存在 ,之后当极核移至靠近卵细胞时便消失 ,显示中央细胞纵向微管与极核的移动和定位可能有关。     

无籽八月桔胚囊及胚胎发育细胞学观察

运用酶解振荡压片技术和常规石蜡切片技术分别研究了无籽八月桔的胚囊育性及无籽八月桔自交和异交(无籽八月桔×台湾椪柑,无籽八月桔×有籽八月桔)的胚胎发育.结果表明:无籽八月桔胚囊可育,成熟胚囊具一个卵细胞、两个助细胞、三个反足细胞以及一个大的含二个极核的中央细胞;其自交和异交的胚胎发育均正常,授粉后2周出现球形胚和少量心形...     

Embryology of Plagiopteron suaveolens Griffith (Plagiopteraceae) and its systematic implications

A study of the embryology of Plagiopteron suaveolens Griffith is presented in order to evaluate the affinities of the genus. Anther wall formation is of the dicotyledonous type. The anther tapetum is glandular and its cells become two to four nucleate. Cytokinesis in the microspore mother cell is simultaneous and the resultant tetrad is tetrahedral. The mature pollen grains are two-celled. The anther has 4-locules at anthesis. The ovule is anatropous, bitegmic and weakly crassinucellate with only one cell-layered parietal tissue. The micropyle is zig-zag in section and formed by both inner and outer integuments which are three and three to four cell layers thick respectively. The megaspore archesporium is one-celled and the embryo sac development is of the Polygonum type. An endothelium is formed with early disintegration of nucellar tissue. The antipodals multiply to 15 to 20 cells. Embryological evidence supports the placement of Plagiopteron in its own family, Plagiopteraceae, with closest relationship with Celastraceae and close relationship with Elaeocarpaceae, Rhizophoraceae and some families of the Geraniales.