水稻胚囊超微结构的研究

水稻(Oryza sativa L.)胚囊成熟时,卵细胞的合点端无细胞壁,核居细胞中部,细胞器集中在核周围,液泡分散于细胞周边区域。助细胞珠孔端有丝状器,合点端无壁,核位于细胞中部贴壁处,细胞器主要分布在珠孔端,液泡主要分布在合点端。开花前不久,一个助细胞退化。中央细胞为大液泡所占,两个极核靠近卵器而部分融合,细胞器集中在极核周围和靠近卵器处,与珠心相接的胚囊壁上有发达的内突。反足细胞多个形成群体,其增殖主要依靠无丝分裂与壁的自由生长,反足细胞含丰富活跃的细胞器,与珠心相接的壁上有发达的内突。开花后6小时双受精已完成,合子和两个助细胞合点端均形成完整壁。合子中开始形成多聚核糖体、液泡减小。退化助细胞含花粉管释放的物质,其合点端迴抱合子。极核已分裂成数个胚乳游离核,中央细胞中细胞器呈活化状态。反足细胞仍在继续增殖。讨论了卵细胞的极性、助细胞的退化、卵器与中央细胞间界壁的变化、反足细胞的分裂特点等问题。     

水稻胚囊卵器细胞发育期间超微结构变化的观察

通过透射电镜对水稻（ＯｒｙｚａｓａｔｉｖａＬ．）胚囊卵器发育过程中超微结构的变化进行观察,结果表明：卵器刚形成时,３个细胞均有完整的细胞壁,壁上分布着许多胞间连丝,不久各细胞合点极壁出现突起解体。随着卵器细胞进一步发育,合点极壁不断解体。到胚囊成熟时,卵细胞的合点极壁消失,仅留下一层质膜;助细胞由于出现退化,侧边近合点端壁出现断裂破碎解体。此时,３个细胞只在弯钩壁上观察到胞间连丝。卵器细胞不同发育阶段各种细胞器的变化很明显,其中最为明显的是质体和液泡。卵细胞在整个发育过程中大部分的质体都含有淀粉粒,而助细胞的质体在２个极核移向卵器上方时,质体内淀粉粒已消失,直至胚囊成熟也未重新出现;卵细胞液泡的出现时间、大小和位置与助细胞的有所不同,卵细胞液泡出现较迟,但到发育后期,液泡体积却明显比助细胞的大,液泡除了主要位于合点极外,珠孔极也有些液泡,而助细胞的则主要位于合点极。助细胞中脂滴的出现存在一个高峰期,即发生在胚囊近成熟时。助细胞核在发育早期呈椭圆形,位于近中部偏珠孔端,在发育中后期呈不规则形,位于近珠孔端壁旁边。水稻卵器发育过程中各细胞的超微结构变化充分反映其代谢规律。     

鹤顶兰珠心细胞程序性死亡的超微结构研究

应用电子显微镜对鹤顶兰(Phaius tankervilliae(Aiton)Bl.)珠心细胞进行了观察,结果发现,珠心细胞程序死亡(programmed cell death,PCD)过程中伴随着液泡破裂、染色质凝聚、细胞质解体等明显特征。在鹤顶兰功能大孢子形成之前,大孢子母细胞的侧细胞壁存在明显的内突。随着胚囊体积的逐渐增大,衰退珠心细胞残留的细胞壁叠合在一起,从而使胚囊壁不断加厚。胚囊成熟前,合点端珠心细胞与胚囊之间有胞间连丝相连。合点端珠心细胞的细胞质状态,特别是液泡形态与大孢子母细胞、功能大孢子、成熟胚囊时期的细胞状态高度相似。结果表明,衰退的珠心细胞不仅为胚囊的扩大提供空间,同时也为胚囊的发育提供营养,合点端珠心细胞对胚囊发育内环境的稳定性起着重要的屏障作用。     

鹤顶兰胚囊发育过程中Ca~（2＋）分布的超微细胞化学定位（英文）

用焦锑酸盐沉淀法对鹤顶兰（Phaius tankervilliae）胚囊发育过程中的Ca2＋状态进行超微细胞化学定位。观察结果发现：功能大孢子时期,珠孔端的胚囊壁上开始出现小颗粒的Ca2＋沉淀,但功能大孢子细胞内未见明显的Ca2＋标记;四核胚囊时期胚囊壁上的Ca2＋沉淀明显增多,液泡膜上有Ca2＋沉淀出现,珠孔处的Ca2＋沉淀颗粒较大;成熟胚囊时期,胚囊壁上的Ca2＋沉淀进一步增多,且胚囊内Ca2＋分布明显增多,且极性明显,珠孔端助细胞、卵细胞比合点端反足细胞有更多的Ca2＋沉淀。鹤顶兰成熟胚囊内Ca2＋积累的来源有：（1）在胚囊成熟前主要由珠被细胞、珠细胞通过胞间连丝向胚囊运输;（2）以沉淀有大量Ca2＋的小泡形式跨过胚囊壁进入胚囊。     

水稻多卵卵器的起源

被子植物的卵器中通常只有１ 个卵细胞。在水稻（Ｏｒｙｚａ ｓａｔｉｖａ）多胚品系胚囊中观察到二卵卵器和三卵卵器。对其大孢子和胚囊发生进行了观察,首次揭示了被子植物多卵卵器的起源。该品系大孢子发生正常。大孢子母细胞进行正常的减数分裂形成４ 个大孢子。靠近合点端的大孢子发育,其它３ 个退化。功能大孢子第一次有丝分裂后,两个子核被一中央大液泡分隔在胚囊珠孔端和合点端。紧接着发生第二次有丝分裂,合点端核分裂时纺锤丝与胚囊纵轴平行,而珠孔端核分裂时纺锤丝与胚囊纵轴成４５°夹角。由此产生的四核胚囊中,合点端１核向胚囊中部或中上部（胚囊珠孔端）迁移。四核胚囊再经１ 次有丝分裂形成两种类型的核分布偏离蓼型的八核胚囊。一种类型是珠孔端４个核,中部与合点各２ 个核,在胚囊细胞化过程中,珠孔端４ 核分化成四细胞卵器,其中卵细胞和助细胞各２ 个,中部的２ 核分化成２ 极核中央细胞,合点端的２ 核形成反足细胞。另一种类型是珠孔端６ 个核,合点端２ 个核,在胚囊细胞化过程中,两端各１ 核向中部迁移分化成２ 极核中央细胞,珠孔端剩余的５ 核分化成５ 细胞卵器,其中卵细胞３ 个,助细胞２ 个,合点端的１ 核迅速分裂形成反足细胞     

延龄草(Trillium tschonoskii Maxim.)的胚胎学研究初报Ⅰ.——大孢子的发生及雌配子体的形成

本文描述延龄草(Trillium tschonoskii Maxim.)的大孢子发生,雌配子体的形成和雄配子体的形态。胚珠为倒生型,双珠被,厚珠心型。胎座为侧膜胎座向中轴胎座的过渡类型,胶囊发育为葱型的变异型。孢原细胞直接发生于幼胚珠的珠心表皮细胞之下,孢原细胞平周分裂,形成初生周缘细胞及初生造孢细胞。初生周缘细胞分裂先于初生造孢细胞,分裂结果与珠心表皮细胞共同形成了珠心组织。初生造孢细胞进一步发育,形成大孢子母细胞。大孢子母细胞经减数第一次分裂后,即出现壁,形成二分体。一般是珠孔端二分体细胞小于合点端二分体细胞,但偶尔也见到前者大于后者的情况。在二分体形成后珠孔端二分体细胞立即退化、或经减数第二次分裂后再退化(该次分裂多为斜向的)。合点端二分体细胞发育,经二核胚囊,四核胚囊,六核胚囊阶段至成熟胚囊。一般在珠孔端的周围淀粉粒丰富,并先于合点端的核进行分裂。珠孔端由二个助细胞,一个卵细胞构成卵器,助细胞具钩突,并具丝状器,两个极核。合点端常见多核仁的大核,成熟胚囊未见八核。成熟花粉粒为二细胞的,花药壁具变形绒毡层,花粉中充满淀粉粒。沼生目型胚乳。     

扁豆成熟胚囊的超微结构

本文对扁豆（Dolichos lablab)成熟胚囊的超微结构进行了研究,在成熟胚囊中,卵细胞和助细胞仅在珠孔端1／3有细胞壁,靠近合点端,卵细胞一助细胞,卵细胞－中央细胞,助细胞－中央细胞之间没有细胞壁存在,相邻细胞的质膜靠在一起,在卵细胞和中央细胞的质膜间,有些地方存在中等电子密度的物质,卵细胞的细胞质中含有很多的线粒体和质体,内质网和高尔基体较少,助细胞的珠孔端有一复杂的丝状器,靠近珠孔端的细胞质中有很多管状的内质网,表明助细胞可能具有分泌功能,在助细胞的合点端,含有丰富的粗糙内质网,助细胞和卵细胞的质膜之间有很多囊泡状的结构,中央细胞内含有丰富的线粒体,高尔基体和内质网,中央细胞的壁向内形成突起,在周缘细胞质中含有丰富的脂滴。     

扁豆成熟胚囊的超微结构

本文对扁豆（Dolichos lablab)成熟胚囊的超微结构进行了研究,在成熟胚囊中,卵细胞和助细胞仅在珠孔端1／3有细胞壁,靠近合点端,卵细胞一助细胞,卵细胞－中央细胞,助细胞－中央细胞之间没有细胞壁存在,相邻细胞的质膜靠在一起,在卵细胞和中央细胞的质膜间,有些地方存在中等电子密度的物质,卵细胞的细胞质中含有很多的线粒体和质体,内质网和高尔基体较少,助细胞的珠孔端有一复杂的丝状器,靠近珠孔端的细胞质中有很多管状的内质网,表明助细胞可能具有分泌功能,在助细胞的合点端,含有丰富的粗糙内质网,助细胞和卵细胞的质膜之间有很多囊泡状的结构,中央细胞内含有丰富的线粒体,高尔基体和内质网,中央细胞的壁向内形成突起,在周缘细胞质中含有丰富的脂滴。     

助细胞

被子植物的雌配子体,又称胚囊,通常由七个细胞组成,包括在珠孔端的一个卵细胞,二个助细胞和在合点端的三个反足细胞,以及在这两群之间的一个大的含有两核的中央细胞。胚囊通常是由大孢子母细胞衍生的四个大孢子中近合点端的一个发育而     

宁夏枸杞大孢子发生和雌配子体发育的细胞学研究

采用半薄切片技术和组织化学染色法对宁夏枸杞大孢子发生和雌配子体发育过程中的细胞结构变化及营养物质积累特征进行了观察。结果表明,(1)宁夏枸杞为中轴胎座,多室子房,倒生胚珠,单珠被,薄珠心类型。(2)位于珠心表皮下的孢原细胞可直接发育为大孢子母细胞,减数分裂后形成直线型大孢子四分体,合点端第一个大孢子发育为功能大孢子,胚囊发育类型为蓼型,具有珠被绒毡层。(3)初形成的胚囊外周组织中没有营养物质积累,成熟胚囊时期出现了大量的淀粉粒且呈珠孔端明显多于合点端的极性分布特征。(4)助细胞的珠孔端具有明显的丝状器结构,呈PAS正反应表现出多糖性质,成熟胚囊具有承珠盘结构。     

Some aspects of organization and histochemistry of the embryo sac ofScilla sibirica sato

Summary The present investigation deals with some of the organizational and histochemical aspects of the embryo sac ofScilla sibirica. Both the synergids and egg cell are invested by PAS-positive complete walls. The filiform apparatus comprises an elaborate system of fibrillar projections, showing extensive ramifications. The micropylar region of the embryo sac wall from where the filiform apparatus originates is composed of three distinct layers. On a histochemical basis it may be surmised that, unlike the egg cell, the synergids are metabolically very active. Two kinds of wall ingrowths (i) massive and highly branched very much akin to the filiform apparatus, and (ii) small tuberculate wall projections, are unique to the antipodal cells of S.sibirica. Small tuberculate projections have also been observed along the wall of the central cell adjacent to the nutrient-rich nucellar cells. The antipodals and the central cell show the presence of starch grains and abundant total proteins. All the cell types in the embryo sac ofS. sibirica are structurally so organized as to meet the requirements of its nutrition during pre- and postfertilization development. The presence of abundant PAS-positive granular substance in the cells of nucellar epidermis probably establishes a gradient which assists in the pollen tube growth.     

EMBRYO SAC LACKING ANTIPODAL CELLS IN ARABIDOPSIS THALIANA (BRASSICACEAE)

Ultrastructure of the embryo sac lacking antipodals in prefertilization stages in Arabidopsis thaliana has been examined 2 hr before and 5 hr after manual cross pollination. The cytoplasm of both synergids before fertilization is rich in ribosomes, mitochondria, and rough endoplasmic reticulum, and also contains several microbodies and spherosomes. The filiform apparatus includes electron-dense material and a fibrous part. Many cortical microtubules appear in the filiform apparatus area. One of the two synergids degenerates before fertilization. The synergids, the egg cell, and central cell have a rich cytoskeleton of microtubules; only the synergids appear to contain microfilaments. At the chalazal end, the antipodals are initially present but degenerate by the time of pollination in most embryo sacs in the starchless line studied. The embryo sac is completely surrounded by a wall containing an electron-dense layer, separating it from the nucellus, including the chalazal end. When the antipodals have degenerated, the electron-dense layer disappears at the chalazal end only, and the wall between the central cell and the nucellus is homogeneous. Between the central cell and nucellar cells no plasmodesmata are found. The membranes of both antipodal cells at the chalazal end of the embryo sac appear sinuous, like those of transfer cells. The central cell has plastids preferentially distributed around the nucleus, but the other organelles are randomly distributed. The central cell in the embryo sac and the adjacent chalazal nucellar cells show a transfer-cell function in the embryo sac after the antipodals degenerate.     

A CYTOCHEMICAL STUDY OF EMBRYO SAC DEVELOPMENT IN STELLARIA MEDIA

Megasporogenesis and embryo sac development in Stellaria media were investigated using cytochemical methods for the demonstration of nucleic acids, proteins, and polysaccharides. RNA concentrations were high in the archesporial cells, low in the megaspore mother cell, and increased again to high concentrations with the formation of the megaspore and 2-, 4-, and early 8-nucleate embryo sac. RNA levels were also high in the egg and primary endosperm nucleus but low in the synergid and antipodal cells. Nucleolar size and vacuolation were indicative of RNA synthetic activity. Protein concentrations were parallel in concentration and distribution to those observed for RNA. Polysaccharides were conspicuously absent from all stages except the synergids and nucellar cells. Feulgen-stained DNA was demonstrable in the antipodal cells, megaspore mother cell, and megaspore cell, but was not visible in the 2-, 4-, or early 8-nucleate embryo sac. Feulgen staining was also absent from the egg and primary endosperm nucleus but was visible in the synergids and antipodals. Histones were difficult to visualize anywhere except in the egg cytoplasm and the nuclei of the antipodals.     

黄顶菊的大孢子发生、雌配子体与胚胎发育

用常规石蜡制片对黄顶菊(Flaveria bidentis(L.) Kuntze)大孢子发生、雌配子体和胚胎的发育过程进行了观察.黄顶菊雌蕊柱头二裂,2心皮,1室,单胚珠,基生胎座,单珠被,薄珠心,倒生胚珠,具发达的珠被绒毡层.珠心表皮下分化出孢原细胞,孢原细胞直接发育为大孢子母细胞,大孢子母细胞减数分裂形成直列四分体...     

An Ultrastructural Study on the Development of Egg- apparatus in Rice Embryo Sac

The development of the egg-apparatus (consisted of an egg cell and two synergids) of rice ( Oryza sativa L. ) was studied at the uhrastructural level. The walls of the egg cell and synergids, immediately after their formation, possessed numerous plasmodesmata. Plasmodesmata were also present on walls between the egg cell and synergids. During the enlargement phase of the egg cell and synergids, the walls at the tip region began to loosen and vesiculate. By the time the embryo sac became mature, the part of the wall of the egg cell and synergids, facing the chalaza, disappeared. Consequently, the tip regions of the egg cell and synergids were only protected by a plasma membrane. When the embryo sac reached full maturity, the upper and middle region of the wall of the synergids broke up into pieces. At that time one synergid began to degenerate. Plasmodesmata persisted at the hook region of the wall of both the egg cell and synergids. Most plastids in the egg cell contained starch grains that persisted throughout the period of the embryo sac development. Starch grains in the plastids of the synergids appeared only before the time when the two polar-nuclei moved into the region above the egg-apparatus. They then disappeared and did not appear again until the embryo sac had reached full maturity. The size and location of the vacuoles in the egg cell were different from those in the synergids. The time of formation was also different. Vacuoles in the egg cell formed late in comparison with the synergids. Vacuoles in the chalazal region of the egg cell (especially at the early stage of the embryo sac development) were much larger than those in the micropylar region. Vacuoles in the synergids tended to concentrate mainly in the chalazal region. There was a peak period of lipid formation in the two synergids. The peak appeared when the embryo sac neared maturity. At the early stage of development, the nuclei of the synergids were elliptical in shape and were situated at the central region near the micropyle. The shape of the nuclei at the late stage of development became less regular and tended to move more towards the micropylar region. Changes in the uhrastructure of the egg cell and synergids of rice appeared to be closely related to the metabolic processes controlling the embryo sac formation and development.     

水稻胚囊发育过程中微管的变化

对水稻(Oryza sativa L.)胚囊发育过程中微管变化的研究表明,微管在胚囊发育的不同阶段变化多样。在大孢子母细胞阶段微管分布主要呈辐射状,部分纵向排列。二分体和功能大孢子具类似的微管分布,而在单核胚囊微管主要是随机分布,部分呈辐射状。两核和四核胚囊的微管组成和分布非常相似,主要分布于细胞核周围。而八核胚囊的微管分布较为复杂,胚囊中的细胞做管分布各异,在卵细胞中呈随机分布,在助细胞中大多数呈纵向分布,而在中央细胞中呈横向分布,微管在反足细胞中非常分散,细胞质中有少量纵向排列的微管。     

Ultrastructural characterization of apospory in Panicum maximum

The nucellar ultrastructure of apomictic Panicum maximum was analyzed during the meiocytic stage and during aposporous embryo sac formation. At pachytene the megameiocyte shows a random cell organelle distribution and sometimes only an incomplete micropylar callose wall. The chalazal nucellar cells are meristematic until the tetrad stage. They can turn into initial cells of aposporous embryo sacs. The aposporous initials can be recognized by their increased cell size, large nucleus, and the presence of many vesicles. The cell wall is thin with few plasmodesmata. If only a sexual embryo sac is formed, the nucellar cells retain their meristematic character. The aposporous initial cell is somewhat comparable to a vacuolated functional megaspore. It shows large vacuoles around the central nucleus and is surrounded by a thick cell wall without plasmodesmata. In the mature aposporous embryo sac the structure of the cells of the egg apparatus is similar to each other. In the chalazal part of the egg apparatus the cell walls are thin and do not hamper the transfer of sperm cells. Structural and functional aspects of nucellar cell differentiation and aposporous and sexual embryo sac development are discussed.     

鹤顶兰胚囊发育的超微结构观察

运用电子显微镜技术对鹤顶兰(Phaius tankervilliae(Aiton)BI.)胚囊发育过程中功能大孢子、二核胚囊、四核胚囊、成熟胚囊的超微结构进行观察,捕捉到了功能大孢子的三个阶段、成熟胚囊的两个阶段,进一步积累了鹤顶兰生殖生物学研究的基础资料.在功能大孢子、四核胚囊时期的合点端壁上可观察到胞间连丝,与体细胞间有物质及信息的交换,胚囊发育并非处于完全“隔离”状态.功能大孢子早期可见明显大液泡,随后进入第一次有丝分裂时大液泡消失,移向两极的染色体之间可见大量体积较小的液泡,成熟胚囊前期助细胞及卵细胞内也可见明显液泡,但当助细胞解体时,卵细胞内的大液泡也消失,液泡形态的变化可能是细胞生理状态发生改变的结果.