小麦受精过程中酸性磷酸酶的超微细胞化学定位

小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ ）受精前成熟胚囊,除胚囊中央细胞的合点端细胞质中有酸性磷酸酶外,其余部位均未发现酸性磷酸酶。受精时期,以下部位存在酸性磷酸酶活性：卵细胞的细胞核内一部分染色质和细胞质中大部分线粒体;精、卵核融合时两核的核周腔内;退化助细胞合点端细胞质和一些液泡内;进入雌性细胞中的两个精核;胚囊各成员细胞的细胞壁及胚囊周围珠心细胞的细胞壁。二细胞原胚中未见有酸性磷酸酶。早期胚乳游离核染色质上有酸性磷酸酶。小麦受精过程酸性磷酸酶的分布特点可能与卵细胞生理状态的变化和细胞质中线粒体的改组、助细胞的退化、精核的生理状态以及精核与卵核的核膜融合等有关。     

番茄受精作用及其间隔期的研究

利用常规石蜡切片法研究了番茄受精作用的全过程,具体研究结果为:(1)授粉后2 h,花粉粒在柱头上萌发;约2~4 h,花粉管长入柱头,且末端膨大;约8 h后,生殖细胞进入分裂期;并于约两小时后,分裂为两个精细胞。(2)约14 h,花粉管进入子房腔;约18~24 h,花粉管进入胚囊,破坏一个助细胞,并在其珠孔端释放两个精子;随后被释放的精子移到卵细胞与次生核附近。(3)授粉后约30 h精核进入卵细胞;约34 h,精核与卵核融合,并在卵核内出现分散的雄性染色质,进而出现雄性核仁;44~50 h,雌、雄性核仁融合,形成合子;合子的休眠期为10 h左右。60 h之后,合子分裂形成二细胞原胚。(4)约26 h,另一个精子的精核与次生核核膜相贴伏,随后与之融合;约30~34 h,次生核内出现分散的雄性染色质,随之出现雄性核仁;约38~42 h,雌、雄性核仁融合,形成初生胚乳核。约44 h后,初生胚乳核进行有丝分裂,形成两个胚乳细胞。番茄胚乳发育属于细胞型。初生胚乳核无休眠期。(5)精子与次生核的融合比与卵核的融合快。(6)番茄的受精作用属于有丝分裂前配子融合类型。     

甜叶菊的受精作用及胚和胚乳的早期发育

成熟胚囊被珠被绒毡县包围,由卵器、具次生核的中央细胞以及数目为1至6个反足细胞组成。传粉后6小时左右,雌、雄性核融合。配子融合同精核与次生核的融合几乎同时发生;精核与次生核融合速度快于配子融合。甜叶菊受精作用属于有丝分裂前类型。传粉后8小时左右,初生胚乳核分裂,其分裂方向可与胚囊长轴平行或垂直,从而形成最初的两个胚乳细胞。胚乳细胞前5次分裂是同步的。心形胚阶段,胚乳细胞呈现被消化吸收的迹象。胚乳发育属细胞型。传粉后10小时左右,合子第一次分裂,为横分裂。胚胎发育属紫菀型。     

春小麦早期胚胎发育进程及细胞融合(cytomixis)的观察

观察了小麦胚和胚乳初期的发育进程,得到如下结果:授粉后2小时,二个精子已分别进入卵核和极核;6小时,极核已经完成受精,卵核与另一精子的融合正在进行。授粉后24小时为二细胞原胚,6天时部分胚胎开始分化。授粉后3天,胚乳核开始形成细胞,至6天时,胚乳细胞充满胚囊。开花前充分发育的反足细胞授粉后开始解体,第4天已失去细胞结构,仅留下核仁和染色质团块,第8天几乎完全消失。在珠心、胚乳、子房壁和原胚以及分化胚的胚柄中都观察到细胞融合现象,而且在原胚附近出现较多。     

福建柏受精作用的研究

福建柏精原细胞分裂后,产生两个形态和大小都相同的雄配子——精子;精子形成时,犹如两个相连的半球体,各具细胞壁。中央细胞分裂产生腹沟核和卵核,腹沟核形成后逐渐退化;卵核却迅速增大。6月下旬,精核在颈卵器中部或中上部与卵核相遇,进行受精作用。在精卵融合过程中,进入卵细胞的雄细胞质,逐渐包围受精卵,并与部分卵细胞质结合形成新细胞质。受精后,在新细胞质中,又呈现大量淀粉粒。当受精卵移到颈卵器底部时,合子开始进行第一次有丝分裂。在原胚和幼胚发育阶段,多余精核还可进入卵细胞,并进行有丝分裂,以致形成7—8个游离核。     

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。     

四倍体双穗雀稗兼性无孢子生殖的研究

研究了四倍体双穗雀稗(Paspalum distichum L)无孢子生殖胚囊、胚胎发育以及假受精特点。当其大孢子母细胞发育至四分体阶段时,大多数情况下会发生四分体退化,同时有多个特化珠心细胞发育为1—3个无孢子生殖胚囊的现象。成熟无孢子生殖胚囊一般3核,包括1个卵细胞和2个极核。卵细胞在抽穗前就能自发分裂形成原胚团,而极核则在抽穗和传粉后参与假受精形成胚乳。当胚珠内存在多个无孢子生殖胚囊时,只是靠近珠孔端的1个无孢子生殖胚囊内的极核与精核结合,而其它的并不参与。种子成熟后出现很低频率的二胚苗。此外,还能观察到少量的有性生殖胚囊的发育以及有性生殖胚囊和无孢子生殖胚囊在同一胚珠中的发育现象,因此判断该类群为兼性无孢子生殖体。     

云南油杉受精过程中新细胞质及蛋白泡的动态观察

云南油杉(Keteleeria evelyniana Mast)在受精前,精核与卵核周围的细胞质鞘不明显。受精后,合子核周围出现细密的新细胞质。应用孚尔根核染色法,可以较清晰地将新细胞质染出,呈现较弱的正反应,而合子的核质及受精前的精核与卵核染色极弱。卵细胞质及其中的蛋白泡均为负反应。原胚形成后,除上层外,其余几层细胞质内开始积累淀粉粒。此时胚原细胞核的孚尔根染色深度有所增加。幼胚形成后,在顶端的胚原细胞群中核的孚尔根染色反应已恢复正常。在原胚及幼胚胚原细胞质中也呈现很弱的正反应。在电镜下,胚原层细胞质及新细胞质中均含有核样电子致密小体或称作染色质小体,而原胚莲座层细胞质及四周套细胞质中的线粒体则不含这种核样小体。因此,大蛋白泡在卵核形成的早期数量不多,当合子形成时含量最高,而随着游离核的分裂进程,蛋白泡以及原卵质均逐渐地解体,在原胚形成后全部消解。     

糜子双受精过程的细胞学观察

糜子(Panicum miliaceum L.)受精的全过程在开花后3小时内完成。开花后20分钟,花粉管到达珠孔,30分钟进入胚囊并释放精子;雌、雄性核融合发生在开花后30分钟至3小时。精核与卵核和极核融合的过程基本相同,但总是先完成与极核的融合。开花后2小时,初生胚乳核形成,随后立即分裂。开花后3小时,合子形成,此时胚乳含两个游离核。开花后8—10小时,合子进入分裂期。合子的休眠期约5—7小时。受精作用属于有丝分裂前配子融合的类型。     

非洲狼尾草无融合生殖胚胎学研究

报道非洲狼尾草（ＰｅｎｎｉｓｅｔｕｍｓｑｕａｍｕｌａｔｕｍＦｒｅｓｅｎ）的胚囊形成、胚胎发生与发育过程。非洲狼尾草的孢原细胞直接发育成大孢子母细胞,并由它分裂产生三分体。从大孢子母细胞发育至三分体的不同阶段,均会出现败育。性细胞退化期间,其周围的珠心组织中,常出现一至多个体积较大的无孢子生殖原始细胞。通常只有靠近珠孔端的１个无孢子生殖原始细胞体积进一步增大,并出现大液泡,发育成无孢子生殖单核胚囊。随后,其核经连续两次有丝分裂,形成无孢子生殖四核胚囊,胚囊内的４个核常聚积在珠孔端,４个核进一步分化形成１个卵细胞、１个助细胞和具两个极核的中央细胞,没有反足细胞。胚囊发育属于大黍型。其它的无孢子生殖原始细胞能发育到单核或二核胚囊阶段,而后核解体导致胚囊败育。胚的发生有两种类型：（１）早发生胚。大多数胚囊在开花前一、二天,次生核未分裂,卵细胞不经受精,自发分裂形成胚。（２）迟发生胚。少数胚囊的卵细胞不经过受精,但需要在开花后三、四天次生核分裂为多个胚乳核时才开始分裂。无论是早发生胚或迟发生胚,卵细胞在分裂前具有极性,珠孔端有大液泡,细胞质稀薄,合点端细胞质较浓。胚的发育经历球形胚、梨形胚和胚分化阶段。     

Embryological Studies on Sagittaria guayanensis H. B. K. Subsp. lappula (D. Don) Bojin (Alismataceae)

This paper deals with the embryological characteristics of Sagittaria guayanensis H. B.K. subsp. lappula (D. Don) Bojin. The anther wall development follows the Monocotyledonous type. The cytokinesis of microspore mother cell in meiosis is of the Successive type. The tetrads of microspores show an isobilateral arrangement, and the mature pollen grains are 3-celled. The ovule is bitegminous, pseudo-crassinucellate and anatropous. The megaspore mother cell originates directly from a single archesporial cell. The mature embryo sac consists of 7 cells including 8 nuclei and conforms to the Allium type. The two polar nuclei do not fuse into a secondary nucleus before fertilization. Instead, one sperm fuses with the micropylar end polar nucleus first , and the fertilized polar nucleus then migrates to the chalazal end, where it fuses with the second polar nucleus, forming the primary endosperm nucleus. The embryo development conforms to the Caryophyllad type. The mature embryo is U-shaped and forms the embryonic shoot apex accompanied by two leaves. The endosperm development corresponds to the Helobial type. The primary endosperm nucleus (invariably lying in the chalazal part of the embryo sac) divides and forms two chambers:large micropylar one and small chalazal one. The chalazal endosperm chamber remains binucleate, while, in the micropylar chamber free nuclear divisions occur and then cellnlarization takes place. During the embryo formation the endosperm gradually degrades and can not be found in the mature seed. The subgenus Lophotocarpus is different from the subgenus Sagittaria in some embryological aspects, especially in the structure of mature embryo sac and the double fertilization process.     

冠果草的胚胎学研究

冠果草花药壁的发育为单子口十型,绒毡层为周原质团型。小孢子母细胞减数分裂为连续型,四分体呈左右对称式排列,成熟花粉为三细胞型。双珠被,假厚珠心,倒生胚珠。胚囊发育为葱型,成熟胚囊的特点是两个极核分别位于中央细胞两端,不融合成次生核。受精过程中,一个精于与卵核融合形成合子,另一精子先与珠孔端极核融合,之后受精极核再移动到合点端与另一极核融合,形成初生胚乳核。胚的发育为石竹型。成熟胚呈马蹄形,具有2片真叶。胚乳发育为沼生目型。随着胚的发育,胚乳细胞逐渐解体,成熟种子中无胚乳。     

Ovule,Female and Male Gametophyte and Fertilization of Kingdonia uniflora Balfour F. et W. W. Smith

The structure of ovule, female and male gametophyte, double fertilization and the distrubution of starch grains during the fertilization have been studied. The main results are as follows: ( 1 ) Ovule The ovule is anatropous, unitegmic and tenuinucellate. The nucetlus appears cylindric, since megaspores and embryo sac development, its internal cells of nucellus become disorganized, so that only a single layer of epidermal cells remains toward the side of the micropyle, On the other hand, the integument is not as long as nucellus, as a result micropyle is not formed. And no vascular bundle is found in the integument. (2) Female gametophyte The mature embryo sac is slender and is composed of an egg cell, two synergids, a central cell and three antipodal cells. The egg cell is situated slightly away from the tip of embryo sac. Some of them contain starch grains. Synergids occupy the tip of embryo sac. Its wall at micropylar region appears irregular in thickenes and irregular in ingrowths to form the filiform apparatus. The centrateell is very large, and strongly vacuolated Two polar nuclei come to contact closely with each other, but not fuse, or to fuse into a large secondary nucleus before fertilization. The polar nuclei or the secondary nucleus are usually situated at the middle-lower position of the central cell or nearer to the chalazal end above the antipodal cell. It is different from egg cell, no starch grains are found here. In most embryo sacs three antipodal cells are found. They are not as large as those in other plants of Ranunculaceae. But six antipodal cells or the antipodal cell with two nuclei may rarely be found. Like synergid, the wall of them appears not only irregularly thickened, but clearly with irregular ingrowths. In a few antipodal cells the starch garins are usually found near the nucleus. By the end of fertilization, antipodal cells become disintegrated. (3) Male gametophyte Most pollen grains are two-celled when shedding, and rich in starch grains. A few of them contain single nucleus or three-celled. (4) The double fertilization The fertilization of Kingdonia unifiora Balfour f. et W, W. Smith is wholly similar to some plants of Ranunculaceae studied. First, the pollen tube penetrates a degenerating synergid. And the pollen tube discharges its contents with two sperm nuclei into the degenerating synergid cell. One of the two sperms fuses with the nucleus of the egg, and the other fuses with two polar nuclei or the secondary nucleus of the central cell. If one sperm nucleus at first fuses with one of the polar nuclei, and then the fertilized polar nuclei again fuses with other polar nucleus. Secondly, the fertilization of the polar nuclei or the secondary nuclei completes earlier than that of the egg. The primary endosperm nucleus begins to divide earlier than the zygote. It seems that one of the sperm nuclei come to contact with egg nucleus, the other has already fused with polar nuclei or the secondary nucleus. The zygote with a single nucleolus appears until the endosperm with 16–20 cell. Thirdly, before and after fertilization there are one to some small nucleoli in egg nucleus and polar nuclei or secondary nucleus. However they increase in quantity from the beginning of the fusion of male nucleis. These nucleoli quite differ from male nucleoli by their small size, and most of them disappear at the end of fertilization. It may be concluded that the small nucleoli increase in quantity is related to the fusion of male and female nuclei. In the duration of fertilization, in ovule starch distribution is in the basal region of integument. But in embryo sac, onlysome egg cells, or zygotes contain starch grains, a part of which was brought in by pollen tube. Sometimes the starch grains are found in some synergids and antipodal cells. No starch grains are found in the central cell.     

Invvestigations on Early Embryogenesis of Actinidia chinensis Planch var. chinensis

This paper deals with early embryogenesis of Actinidia chinensis var. chinensis. 1. Ovary superior consists of 34—45 carpels. Each carpel contains 11–45 ovules. The ovule is uni-integument and tenuinucellar. The ovule is anatropous. The archesporium is formed by a single cell, and directly develops into megaspore mother cell. Sometimes the archesporium consists of 2–3 cells, but only one of them develops into megaspore mother cell and the others are degenerated. 2. The mature pollen grain is two-celled and the embryo sac belongs to olygonum type. In most embryo sacs two polar nuclei are fused before fertilization. One of the synergids was destroyed as the pollen tube penetrated into embryo sac the other one disappeared after fertilization. In most cases the antipodal cells became degenerated in fertilization process, only some remained until the first division of primary endosperm nucleus. 3. In Beijing area the double fertilization of Actinidia chinensis occurred 30–72 hours after pollination. In the fertilization one sperm fused with egg nucleus and the other sperm fused with the secondary nucleus as usual. The fusion of the secondary nucleus with sperm was in advance of the fusion of the egg nudeus. 4. The endosperm is cellular type.     

Observations on Fertilization in Sugar Beet

The whole process of double fertilization in sugar beet has been observed, the main results are as follows: About 2 hours after pollination, the pollen grains germinate, the sperms in the pollen tube are long-oval. 15 hours after pollination, the pollen tube destroys a synergid and releases two sperms on one side or at the chalazal end of the egg cell. The sperms are spherical each having a cytoplasmic sheath. 17 hours after pollination, one sperm enters the egg cell, and the sperm nucleus fuses with the egg nucleus rapidly. 21 hours after pollination, the zygote is formed. In the meantime, the primary endosperm nucleus has divided into two free endosperm nuclei. 25 hours after pollination, the zygote begins to divide, forming a two-celled proembryo. The dormancy stage of the zygote is about 4 hours. In the meantime the endosperm is at the stage of four free nuclei. 17 hours after pollination, the sperm nucleus comes into contact and fuses with the secondary nucleus. The sperm nucleus fuses with the secondary nucleus, faster than the sperm with the egg. he first division of the primary endosperm nucleus is earlier than that of the zygote, it takes place about 20 hours after pollination, the dormancy stage of the primary endosperm is about 2 hours. The endosperm is free nuclear. The fertilization of sugar beet belongs to premitotic type of syngamy. From the stage of zygote to the two-celled proembryo, it can be seen that addition- al sperms enter the embryo sac, but polyspermy has not been observed yet.     

被子植物受精机制的研究进展

被子植物的受精是一个复杂而精巧的过程。花粉管到达子房,通过退化助细胞进入胚囊,释放出两个精细胞。原来在花粉管中相互联结的两个精细胞在退化助细胞中分开,一个与卵细胞融合,另一个与中央细胞融合,完成双受精。目前对双受精过程中有关雌、雄配子识别的机制还知之甚少。本文介绍了目前被子植物精、卵细胞融合前后的细胞周期变化、退化助细胞的功能、精细胞在退化助细胞中迁移的研究动态、精细胞的倾向受精和卵细胞的激活等被子植物受精生物学领域中的一些新的研究成果和发展趋势。     

向日葵胚囊的超微结构和雌性生殖单位问题

本文对向日葵胚囊中卵细胞、助细胞与中央细胞开花前和传粉后的超微结构变化进行了研究。着重报道了不同发育时期这三种细胞之间特定区域的界壁的消长动态。在此基础上结合现有文献资料探讨了由三者共同组成“雌性生殖单位”以适应受精作用的问题。     

SEXUAL REPRODUCTION IN EPHEDRA NEVADENSIS (EPHEDRACEAE): FURTHER EVIDENCE OF DOUBLE FERTILIZATION IN A NONFLOWERING SEED PLANT

Since the initial discovery of double fertilization in angiosperms in 1898, a number of reports of double fertilization-like events in the genus Ephedra have appeared. Until recently, convincing documentation of double fertilization in Ephedra had not been presented. In Ephedra nevadensis, following entry of a single binucleate sperm cell into the egg cell, one sperm nucleus migrates in a chalazal direction to fuse with the egg nucleus. Contemporaneous with this first fertilization event, the ventral canal nucleus regularly migrates from its initially apical position within the egg cell to a more central position within the egg cytoplasm, where it fuses with a second sperm nucleus. Based on quantitative microspectrofluorometric analysis, occasional supernumerary nuclei within the egg cell (derived by migration through pores in the cell walls between jacket cells and the central cell or egg cell) can be ruled out as participating in the second fertilization event. The evolutionary establishment of double fertilization in Ephedra (or its ancestors) was dependent on a number of specific developmental preconditions: 1) persistence of the ventral canal nucleus (which is degenerate in many groups of nonflowering seed plants) through the time of normal fertilization; 2) regular displacement of the ventral canal nucleus from its initially apical position within the egg cell to a position within the egg cytoplasm where fusion of the egg nucleus with the first sperm nucleus earlier occurred; 3) acquisition of egg-like features by the ventral canal nucleus that allow it to attract and fuse with a sperm nucleus; and 4) consistent entry of a second sperm nucleus into the archegonial cavity to participate in a second fertilization event. Although it cannot be determined definitively whether double fertilization in Ephedra is evolutionarily homologous with double fertilization in flowering plants, comparative evidence is consistent with the hypothesis that double fertilization arose in a common ancestor of the Gnetales and angiosperms.