竹节参雌配子体发育的研究

本文报道了竹节参(Panax japonicus C.A.Mey)雌配子体(胚囊)的发育过程。竹节参大孢子母细胞减数分裂产生线形排列的大孢子四分体。胚囊发育属蓼型,由合点端大孢子发育而成。游离核胚囊时期,胚囊珠孔端的细胞器种类和数量都较胚囊合点端多;胚囊合点端相邻的珠被细胞中有含淀粉粒的小质体,与胚囊珠孔端相邻的退化中的非功能大孢子中则有含淀粉粒的大质体和大类脂体。成熟胚囊中,反足细胞较早退化;极核融合成次生核;卵细胞高度液泡化,细胞器数量较少;助细胞则有丰富的细胞器和发达的丝状器。PAS反应表明,受精前的成熟胚囊中积累淀粉粒。次生核受精后,很快分裂产生胚乳游离核,到几十至数百个核时形成胚乳细胞。卵细胞受精后则要经过较长的休眠期。     

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。     

Structure of Embryo Sac Before and After Fertilization and Distribution of Transfer Cells in Ovules of Green Gram

The structure of embryo sac before and after fertilization, embryo and endosperm development and transfer cell distribution in Phaseolus radiatus were investigated using light and transmission electron microscopy. The synergids with distinct filiform apparatus have a chalazal vacuole, numerous mitochondria and ribosomes. A cell wall exists only around the micropylar half of the synergids. The egg cell has a chalazally located nucleus, a large micropylar vacuole and several small vacuoles. Mitochondria and plasrids with starch grains are abundant. No cell wall is present at its chalazal end. There are no plasma membranes between the egg and central cell in several places. The zygote has a complete cell wall, abundant mitochondria and plastids containing starch grains. Both degenerated and persistent synergids migh.t serve as a nutrient supplement to proembryo. The wall ingrowths occur in the central cell, basal cell, inner integumentary cells, suspensor cells and endosperm cells. These transfer cells may contribute to embryo nutrition at different developmental stages of embryo.     

天竺葵雌性生殖单位的超微结构

应用透射电镜研究了临近受精时天竺葵(Pelargonium hortorum Bailey)胚囊中的卵细胞、助细胞和中央细胞的结构。证明了卵细胞与助细胞以及助细胞与助细胞之间从合点端至珠孔端有很大的面积以质膜分界,仅珠孔端少部分以壁分隔。卵细胞与中央细胞之间同样缺乏细胞壁。在卵细胞的合点端,两质膜不同程度地分离形成宽窄相间的间隙。在间隙的絮状基质中存在小泡,这些小泡的产生似与卵和中央细胞中周质内质网的活动有关。推测小泡为多糖性质,可能为合子新壁的建造提供物质。卵细胞质中含巨大线粒体,质体和内质网也较丰富。基于超微结构的特征,可认为卵细胞具高度的生理合成活动的潜能。中央细胞极核位于珠孔端与卵器细胞毗邻,有利于在双受精作用中同时发生精细胞与卵细胞和精细胞与中央细胞核的融合。中央细胞的侧壁在珠孔端形成内突,具传递细胞的特点,表明这是雌配子体向孢子体摄取营养的重要部位。助细胞的细胞质含丰富的细胞器,这与多数植物中的相似,但具几个明显的特征,即核中存在微核仁,内质网形成圆球体或脂体,线粒体富集在丝状器的附近。传粉后花粉管进入胚囊之前,两个助细胞中一个退化。     

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。     

东北地区野豌豆属VICIAL．物种生物学研究Ⅷ．幼苗形体结构动态和种间界限

在野外居群调查的启示下,本文以组件观点对柳叶野豌豆复合种和歪头菜幼苗亚单位的时序变化与开花关系进行了分析。结果发现在柳叶野豌豆复合种栽培居群中存在打破物种间形体结构特征的个体,即在复叶由一对小叶组成的植株就已开花而进入生殖时期。另外,在歪头菜的野生居群中发现由三或四枚小叶组成复叶的个体,因此,我们推测这种形体结构的变化可能暗示着柳叶野豌豆复合种和歪头菜有着共同的祖先。     

西瓜不同发育时期的助细胞超微结构的变化（简报）

The ultrastructure of synergids of watermelon (Citrullus Lanatus L.) was investigated using transmission electron microscopy at following stages of embryo sacs: 1. Unpollination, on the first flowering day. 2. Unpollination, on 2nd day after anthesis (DAA). 3. Fertilization, on DAA 2. The synergids with distinct filiform apparatus at the micropylar end have abundant organelle, such as mitochondria, endoplasmic reticulum, and plastids in cytoplasm, which indicate that they are active on the first flowering day. No wall is present at the chalazal part of synergid, and there are some flocculent materials and vesicles in the spaces of cytoplasma membranes among synergid, egg cell and central cell in embryo sacs at the first and the second stages. On DAA 2, in unpollinated embryo sacs, the central large vacuole of synergid is divided into several smaller ones and the starch grains decrease in cytoplasm. There is no newly synthesized wall at the chalazal end of persistent synergid in fertilized embryo sacs. The contents of degenerated synergid, in the form of electron dense granules, are located in the wide space among central cell, zygote and persistent synergid, and some of them migrate into central cell through cytoplasma membrane. Therefore, it is deduced that the contents of synergid might serve as a nutrient supplement to the development of endosperm, but not embryo.     

西瓜不同发育时期的助细胞超微结构的变化

被子植物胚囊的“雌性生殖单位”,已在多种植物上进行了超微结构的观察,但大多都以卵细胞受精前后的结构变化为主要研究内容。对于“雌性生殖单位”中的另一重要成员——助细胞,在不同发育状态下其结构变化的详细资料不多,尤其是助细胞退化后的物质去向,少见报道。本研究主要观察了西瓜不同发育时期(受精前后)、不同发育状态(柱头授粉和未授粉)的助细胞超微结构,以期为研究助细胞在双受精中所起作用提供新的资     

FERTILIZATION IN BARLEY

The mature embryo sac of barley consists of an egg, two synergids, a central cell, and up to 100 antipodal cells. At shedding the male gametophyte is 3-celled, consisting of a vegetative cell with a large amount of starch and two sperms having PAS+ boundaries. Before pollination the nucleus and cytoplasm of each synergid appear normal. After pollination the nucleus and cytoplasm of one synergid undergo degeneration. The pollen tube grows along the surface of the integument of the ovule, passes through the micropyle, and enters the degenerate synergid through the filiform apparatus. The pollen tube discharges the vegetative nucleus, two cellular sperms, and a variable amount of starch into the degenerate synergid. Soon after deposition the sperms migrate by an unknown mechanism to the chalazal end of the degenerate synergid. Sperm nuclei then enter the cytoplasm of the egg and central cell, ultimately resulting in the formation of the zygote and primary endosperm nucleus, respectively. Sperm boundaries do not enter egg or central cell, but it was not possible to determine the fate of other sperm components. Degenerate vegetative and synergid nuclei remain in the synergid after fertilization, constituting what are considered to be X-bodies in barley. The second synergid degenerates during early embryogeny.     

Embryo and Endosperm Development in Isatis Tinctoria L. and the Histochemical Study of Its Storage Reserve

The ovule is anatropous and bitegmic. The nuceIlar cells have disorganized except the chalazal proliferating tissue. The curved embryo sac comprises an egg apparatus and a central cell with two palar nuclei and wall ingrowths on its micropylar lateral wall. The antipodal cells disappear. Embryo development is of the Onagrad type. The filament suspensor grows to a length of 785 μm and degenerats at tarpedo embryo stage. The basal cell produces wall ingrowths on the micropylar end wall and lateral wall. The cells of mature embryo contain many globular protein bodies, 2.5–7.5 μm in diameter, composed of high concentration of protein and phytin, insoluble polysaccharide and lipid. The cells, except procambium, also contain many small starch grains. Some secretory cavities scattered in the ground tissue have liquidlike granules composed of protein, ploysacchaide and lipid. Endosperm development follows the nuclear pattern. At the late heart embryo stage, the endosperm around the embryo and the upper suspensor and the peripheral endosperm of the basal region of the U-shaped embryo sac becomes cellular. The endosperm at micropylar and chalazal ends remains free nuclear phase until the late bended cotyledon stage. Wall ingrowths at both micropylar and chalazal end wall and lateral wall of the embryo sac become more massive during endosperm development. Wall ingrowths also occur on the outer walls of the outer layer endosperm cells at both ends and lateral region of the embryo sac. When the embryo matures, many layers of chalazal endosperm ceils including 2–4 layers of transfer cells, a few of micropylar endosperm cells and 1–5 layers of peripheral endosperm cells are present. The nutrients of the embryo and endosperm at different stages of development are also discussed.     

大葱卵器及受精后助细胞的超微结构

章丘大葱（Ａllium fistulosum L.cv.Zhangqiu)的卵器由１个卵细胞及２个助细胞组成,观察到不少卵器没有卵细胞,只有２个助细胞。卵细胞的核及大部分细胞质位于细胞的合点端,１个大液泡占据了细胞其他部位。卵细胞含有很多的核糖体及多聚核糖体、嵴明显的线粒体、粗面内质网、高尔基体具小泡,卵细胞似是一个活跃的细胞。细胞外被细胞壁,其合点端及侧方与助细胞共同壁不连续,助细胞有一较大的核,位于细胞膨大的部位,众多的小液泡遍布细胞中。核糖体及聚合核糖体、线粒体,粗面内质网及风心圆环状粗面内质丰富,高尔基体及小泡常见,反映了其活跃的代谢作用。助细胞合点端及侧方与卵细胞、中央细胞的共同壁不连续,与卵细胞共同壁含胞间连丝,壁不连续处,有不状多层膜结构伸入卵细胞质,显示助细胞可能对卵细胞提供营养,伟粉后,一个助细胞退化,宿存助细胞至随胚胚期尚存在,它经历了一个缓慢的退化过程,出现质壁分离,细胞质变稀,液泡扩大,细胞器逐渐减少,在椭形胚期,宿存助细胞核内的染色质及核仁消失,有细胞质侵入核内,因宿存助细胞壁变厚,细胞质出现现脂滴,宿存助细胞可能仍有合成功能,宿存助细胞壁出现若干无壁部位,细胞内的营养物质可能通过无壁部位向胚乳转运,供游离核胚乳及胚乳细胞化初期的发育。     

Embryological Studies on Apomixis in Pennisetum squamulatum

Studies on the formation and development of the embryo sac of the apomictic material of Pennisetum squamulatum Fresen indicated that normal archesporial cell did form with consequent development of a megaspore mother cell and later meiotic division to give rise to a triad. But invariably the megaspore mother cell and the triad underwent degeneration after formation. During the period of formation or degeneration of the megaspore or the triad a number of nucellar cells around the degenerated sexual cell became much enlarged. Frequently, one of the enlarging nucellar cells near the micropylar end became vacuolated and then developed into an aposporous uninucleate embryo sac, which underwent two further mitotic divisions to form an aposporous four-nucleate embryo sac, where the four nuclei remained in the micropylar end. Thus in the mature aposporous embryo sac there were one egg cell, one synergid and one central cell (containing two polar nuclei). Antipodal cells were completely lacking. The pattern of development of the aposporous embryo sac resembles the panicum type. There were two types of embryo formed during apomictic development namely ( 1 ) The pre-genesis embryo--embryo formed without fertilization, 1 to 2 days before anthesis, and (2) The late-genesis embryo--derived from the unfertilized egg cells, 3 to 4 days after anthesis. In the late-genesis embryo type, the egg cell divided after the secondary nucleus has undergone division to form the endosperm nuclei. All egg cells developed vacuoles before they differentiated into embryos. The development of the aposporous embryo followed the sequence of the formation of globular, pearshaped embryo and full stages of differentiation. The unfertilized secondary nucleus divides to form free endosperm nuclei after being stimulated by pollination. The development of the endosperm belongs to the nuclear-type.     

Studies of Ultrastructure and ATPase Localization of Mature Embryo Sac in Vicia faba L.

Studies of ultrastructure and ATPase localization of the mature embryo sac in Vicia faba L. show that the egg cell has no cell wall at thechalazal end, it has a chalazally located nucleus and a large micropylar vacuole. There are many nuclear pores in the nuclear membrane. The cytoplasm is restricted around the nucleus. Dictyosome and mitochondria are few. There are some starch grains and lipid grains in the egg cytoplasm. There are no obvious differences between two synergids. No cell wall is seen at the chalazal end either, but there are some vesicles which project to vacuole of the central cell and fuse with its vacuolar membrane. Plasmodesmata connections occur within the synergid wall where it is adjacent to the central cell. The synergid has a micropylarly located nucleus and a chalazal vacuole, the nucleus is irregularly shaped. The synergid cytoplasm is rich in organelles. The filiform aparatus is of relatively heterogeneous structure. The central cell is occupied by a large vacuole and its cytoplasm is confined to a thin layer along the empryo sac wall, but is rich in various organelles, starch grains and lipid bodies. Nucleolar vacuoles are often present two polar nuclei. The nuclear membranes of two polar nuclei have partly fused. ATPase reactive product was located obviously at the endoplasmic reticulum in cytoplasm of the egg cell and central cell. The embryo sac wall consists of different density of osmiophilic layer. There are some wall ingrowths in chalazal region of the embryo sac. The long-shaped and cuneate cells of chalazal region are peculiar. Special tracks of ATPase reactive products are visible at their intercellular space which may be related to transportation of nutrients.     

ADVENTIVE EMBRYOGENESIS IN CITRUS AND ITS RELATION TO POLLINATION AND FERTILIZATION

Cytological and histological studies of seeds from three facultative apomictic Citrus cultivars show that adventive embryos develop, as a rule, from the first few cell layers of the nucellus adjacent to the embryo sac in the micropylar half and occasionally from the chalazal end. The adventive embryos initiated in nucellar tissue away from the embryo sac and most of those initiated from the chalazal end of the nucellus do not develop beyond the one-celled stage. When two or more embryos are developing in the same seed, the successful development of a given embryo depends on its location in relation to access to nutrients from the endosperm. The presence of a zygote and triploid endosperm in seeds with adventive embryos, the abortion of seed when endosperm degenerates, and the lack of seed set without pollination indicate that pollination and fertilization are essential for in vivo adventive embryogenesis.     

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。     

莴苣助细胞发育过程中钙的分布研究

用焦锑酸盐沉淀法对莴苣助细胞中的钙分布进行了观察。结果表明,开花前3天刚形成的助细胞中的钙颗粒很少:开花前2天助细胞壁中的钙颗粒增加;开花前1天助细胞珠孔端细胞壁加厚,其中积累了许多钙颗粒:开花当天助细胞珠孔端的丝状器中聚集了大量的钙颗粒。授粉后1h时两个助细胞的结构和钙分布发生差异,一个呈退化状,其中的钙颗粒明显增多,另一宿存助细胞中的钙分布与授粉前相似。去雄不授粉1天后两个助细胞均保持完好,且两助细胞中的钙分布没有明显差异,表明由花粉管引起一个助细胞中钙含量增加进而导致了助细胞退化。退化助细胞在卵细胞与中央细胞之间形成一薄层。助细胞退化后不同部位的钙颗粒呈现出与受精作用密切有关的变化:授粉后1h时,钙主要聚集在近合点端部位;授粉后2.5h卵细胞即将受精,这时许多细小的钙颗粒主要聚集在卵细胞与中央细胞之间的薄层中;授粉后4h精、卵细胞已融合,这时退化助细胞合点端的钙颗粒明显减少,而在其珠孔端又聚集了较多的钙。上述助细胞中的钙含量变化与吸引花粉管进入胚囊和促使精卵细胞融合密切有关。     

Three-dimensional organization and dynamic changes of the actin cytoskeleton in embryo sacs ofZea mays andTorenia fournieri

Summary Actin organization was observed inm-maleimidobenzoic acid N-hydroxysuccinimide ester(MBS)-treated maize embryo sacs by confocal laser scanning microscopy. The results revealed that dynamic changes of actin occur not only in the degenerating synergid, but also in the egg during fertilization. The actin filaments distribute randomly in the chalazal part of the synergid before fertilization; they later become organized into numerous aggregates in the chalazal end after pollination. The accumulation of actin at this region is intensified after the pollen tube discharges its contents. Concurrently, actin patches have also been found in the cytoplasm of the egg cell and later they accumulate in the cortical region. To compare with MBS-treated maize embryo sacs, we have performed phalloidin microinjection to label the actin cytoskeleton in living embryo sacs ofTorenia fournieri. The results have extended the previous observations on the three-dimensional organization of the actin arrays in the cells of the female germ unit and confirm the occurrence of the actin coronas in the embryo sac during fertilization. We have found that there is an actin cap occurring near the filiform apparatus after anthesis. In addition, phalloidin microinjection into the Torenia embryo sac has proved the presence of intercellular actin between the cells of the female germ unit and thus confirms the occurrence of the actin coronas in the embryo sac during fertilization. Moreover, actin dynamic changes also take place in the egg and the central cell, accomplished with the interaction between the male and female gametes. The actin filaments initially organize into a distinct actin network in the cortex of the central cell after anthesis; they become fragmented in the micropylar end of the cell after pollination. Similar to maize, actin patches have also been observed in the egg cortex after pollination. This is the first report of actin dynamics in the living embryo sac. The results suggest that the actin cytoskeleton may play an essential role in the reception of the pollen tube, migration of the male gametes, and even gametic fusion.     

The Development of Green Onion (Allium Fistulosum L. )Embryo and Endosperm

Embryo development of Zhangqiu green onion conforms to the Asterad type and goes through the following stages: proembryo, globular, ellipsoidal, laterally concave, stick-shaped, and curved and mature. The persistent synergid is present until the late globular stage of embryogenesis. Endosperm development of Zhangqiu green onion follows the nuclear pattern. Endosperm cell formation begins at both the micropylar end and the chalazai end of the embryo sac when the embryo is in the late globular stage. Due to the anticlinal wall formation, a layer of free nuclei becomes a layer of “open cells” which lack the inner periclinat wall. The open cells undergo cell division periclinally, and a layer of complete cells is cut off outside and a new layer of open cells inside. The subsequent cell divisions give rise to the endosperm cells centripetally until those from the opposite of the embryo sac meet. The first anticlinal walls arise from the cell plates without phragmoplasts between the free nuclei in interphase. The first periclinal walls are formed by normal cytokinesis. When a few layers of endosperm cells are formed at the micropylar end and the chalazal end of the embryo sac, free cells are present in the central vacuole.     

Three-dimensional organization and dynamic changes of the actin cytoskeleton in embryo sacs ofZea mays andTorenia fournieri

Actin organization was observed in m-maleimidobenzoic acid N-hydroxysuccinimide ester(MBS)-treated maize embryo sacs by confocal laser scanning microscopy. The results revealed that dynamic changes of actin occur not only in the degenerating synergid, but also in the egg during fertilization. The actin filaments distribute randomly in the chalazal part of the synergid before fertilization; they later become organized into numerous aggregates in the chalazal end after pollination. The accumulation of actin at this region is intensified after the pollen tube discharges its contents. Concurrently, actin patches have also been found in the cytoplasm of the egg cell and later they accumulate in the cortical region. To compare with MBS-treated maize embryo sacs, we have performed phalloidin microinjection to label the actin cytoskeleton in living embryo sacs of Torenia fournieri. The results have extended the previous observations on the three-dimensional organization of the actin arrays in the cells of the female germ unit and confirm the occurrence of the actin coronas in the embryo sac during fertilization. We have found that there is an actin cap occurring near the filiform apparatus after anthesis. In addition, phalloidin microinjection into the Torenia embryo sac has proved the presence of intercellular actin between the cells of the female germ unit and thus confirms the occurrence of the actin coronas in the embryo sac during fertilization. Moreover, actin dynamic changes also take place in the egg and the central cell, accomplished with the interaction between the male and female gametes. The actin filaments initially organize into a distinct actin network in the cortex of the central cell after anthesis; they become fragmented in the micropylar end of the cell after pollination. Similar to maize, actin patches have also been observed in the egg cortex after pollination. This is the first report of actin dynamics in the living embryo sac. The results suggest that the actin cytoskeleton may play an essential role in the reception of the pollen tube, migration of the male gametes, and even gametic fusion.     

CAPSELLA EMBRYOGENESIS: THE SYNERGIDS BEFORE AND AFTER FERTILIZATION

The ultrastructure and composition of the synergids of Capsella bursa-pastoris were studied before and after fertilization. The synergids in the mature embryo sac contain numerous plastids, mitochondria, dictyosomes and masses of ER and associated ribosomes. Each synergid contains a large chalazal vacuole, a nucleus with a single nucleolus and is surrounded by a wall. This wall is thickest at the micropyle end of the cell where it proliferates into the filiform apparatus. At the chalazal end of the cell the wall thins and may be absent for small distances. The pollen tube grows into one of the two synergids through the filiform apparatus and extends one-third the length of the cell before it discharges. Following discharge of the pollen tube, mitochondria and plastids of the tube can be identified in the synergid as can hundreds of 0.5 μ polysaccharide spheres liberated by the tube. The method by which the sperm or sperm nuclei enter the egg or central cell is not known although an apparent rupture was found in the wall of the egg near the tip of the pollen tube. The second synergid changes at the time the pollen tube enters the first synergid. These changes result in the disorganization of the nucleus and loss of the chalazal wall and plasma membrane. Eventually this synergid loses its identity as its cytoplasm merges with that of the central cell.