龙须草无融合生殖的胚胎学证据

采用石蜡切片技术对龙须草(Eulaliopsis binata(Rotz)C.E.Hubb)进行了系统的胚胎学研究,证明龙须草为禾本科植物中一种新的无融合生殖材料.龙须草无融合生殖方式为无孢子生殖,在胚珠发育早期,多个珠心细胞特化为无孢子生殖原始细胞,由原始细胞发育为单核胚囊,经两次有丝分裂形成4核胚囊,进一步分化形成两种类型的成熟胚囊:(1)具1个卵细胞,1个助细胞和2个极核,占观察总数的67.6%;(2)具1个卵细胞,2个助细胞和1个极核,占观察总数的32.4%.胚囊发育属大黍型.多个无孢子生殖原始细胞可以同时发育,最后形成2个或多个胚囊,其比例为17.7%.胚珠内没有有性胚囊的发育.胚的发生有两种类型:(1)早发生胚(74%),开花前1～2 d,极核未分裂前卵细胞分裂形成胚;(2)迟发生胚(26%),开花后2～3 d,极核分裂形成多个胚乳游离核后,卵细胞启动分裂形成胚.存在多胚现象,多胚来自不同胚囊内卵细胞的孤雌生殖,多胚发生率为13%.胚乳由极核不经受精自发分裂产生.     

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。     

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。     

赤苎无融合生殖细胞胚胎学研究

对赤苎(Boehmeria silvestrii (Pamp.)W.T.Wang)细胞胚胎学研究表明,其生殖模式属无融合生殖的二倍体孢子生殖(diplospory),但其未减数胚囊的发育途径不同于已报道的类型。大孢子母细胞的减数分裂I在到达终变期时停滞,染色体呈单价体状态并维持较长的时间。在尚未到达以核膜、核仁消失,纺锤体出现为特征的中期I前,大孢子母细胞由终变期直接“跳”入间期,从而始终保持了二倍体水平。减数分裂Ⅱ正常进行并产生二倍体二分孢子。珠孔端孢子退化,合点端孢子经3次分裂形成包括1个卵细胞、2个助细胞、2个极核和3个反足细胞的八核胚囊。胚和胚乳分别起源于卵和次生核未受精的自发分裂。胚乳属核型,其发育早于胚。     

水蔗草兼性无融合生殖胚胎学研究

对水蔗草 (ApludamuticaL .)的生殖方式进行研究 ,结果表明水蔗草进行兼性无融合生殖。胚囊发育分为两种类型 ,即有性生殖的蓼型和无孢子生殖的大黍型。无融合生殖胚囊频率为 6 0 .74%。在大孢子母细胞发育至四分体后 ,珠孔端的 3个大孢子解体。合点端的大孢子未解体时 ,邻近大孢子的 1个珠心细胞开始特化 ,形成无融合生殖的原始细胞 ,由该原始细胞发育形成有 1个卵细胞、1个助细胞和 2个极核的四核胚囊。     

水蔗草兼性无融合生殖胚胎学研究

对水蔗草(Apluda mutica L.)的生殖方式进行研究,结果表明水蔗草进行兼性无融合生殖.胚囊发育分为两种类型,即有性生殖的蓼型和无孢子生殖的大黍型.无融合生殖胚囊频率为60.74%.在大孢子母细胞发育至四分体后,珠孔端的3个大孢子解体.合点端的大孢子未解体时,邻近大孢子的1个珠心细胞开始特化,形成无融合生殖的原始细胞,由该原始细胞发育形成有1个卵细胞、1个助细胞和2个极核的四核胚囊.     

高粱SSA-1无融合生殖胚胎学研究

经常规石蜡切片法,在光学水平观察了高粱（Ｓｏｒｇｈｕｍ ｂｉｃｏｌｏｒ （Ｌ．） Ｍｏｅｎｃｈ） ＳＳＡ－１ 无融合生殖的胚胎发生。高粱ＳＳＡ－１ 的无融合生殖为无孢子生殖和二倍体孢子生殖两种类型。两种生殖类型的单核胚囊经３ 次有丝分裂形成７ 细胞（８ 核）的成熟胚囊,由卵细胞、２ 个助细胞、２ 个极核和３ 个反足细胞组成。反足细胞迅速分裂增殖,形成由２０—３０ 个细胞组成的细胞团。此外,还具有一定频率的无孢子生殖多孢原和多胚囊现象。在未授粉情况下,卵细胞自发分裂形成典型的禾本科类型单子叶胚。经切片统计表明,ＳＳＡ－１ 的无融合生殖频率为４２％ ,证明该系为一兼性无融合生殖系。文中还讨论了ＳＳＡ－１ 无融合生殖过程的特点。     

高梁SSA—1无融合生殖胚胎学研究

经常规石蜡切片法,在光学水平观察了高染（Ｓｏｒｇｈｕｍｂｉｃｏｌｏｒｂｉｃｏｌｏｒ．）Ｍｏｅｎｃｈ）ＳＳＡ－１无融合生殖的胚胎发生。高染ＳＳＡ－１的无融合生殖为无孢子生殖和二倍体孢子生殖两种类型。两种生殖类型的单核胚囊经３次有丝分裂成７细胞（８核）的成熟胚囊,由卵细胞、２个助细胞、２个极核和３个足细胞组成,反足细胞迅速分裂增殖,形成由２０－３０个细胞组成的细胞团。此外,还具有一定频率的无孢子生殖多     

甜菜单体附加系M14无融合生殖的细胞胚胎学研究

利用常规研究方法,对甜菜单体附加系M 14品系(B eta vu lg aris L.,VV 1C、2n=18 1)的生殖方式进行细胞学与胚胎学研究.结果表明:(1)甜菜单体附加系M 14的4代细胞学检查表明:染色体组分别为VV 1C、2n=18 1;VV 0、2n=18 0;VV 2C、2n=18 2;VVV 0、2n=27 0;VVV 1C、2n=27 1;VVV 2C、2n=27 2等,其中VV 1C、2n=18 1的植株传递率平均为96.7%,表现为稳定传递,具有二倍体孢子无融合生殖特性;其余各种分离植株的传递率总计为3.25%,有性生殖发生率较低.(2)胚胎学研究表明,二倍体孢子无融合生殖的胚珠中,珠孔处看不到花粉管,胚囊没有发生受精作用.2个助细胞提前退化,半数卵细胞的极性与正常卵细胞相反;卵与次生核不经受精而自发分裂,卵细胞自发分裂产生无性胚,次生核自发分裂产生核型胚乳,而且次生核自发分裂早于卵细胞分裂;有性生殖胚珠中,珠孔处可见多条花粉管,胚囊里见到精卵融合的图像.表明甜菜单体附加系M 14是以二倍体孢子无融合生殖为主要繁殖方式,有性生殖为次要敏殖方式的兼性无融合生殖体.     

韭菜胚囊发育与胚胎发生

韭菜胚囊发育为葱型,胚胎发生属柳叶菜型。成熟胚囊中,三个反足细胞形态上常类似卵器,其中二个呈助细胞状,一个呈卵细胞状。卵状反足细胞可分裂成多细胞原胚,但随着胚乳的发育而退化。在未受精胚囊中,卵细胞和卵状反足细胞均可分裂,它们的发生过程与合子胚相似,但因无胚乳哺育,均不能继续发育。论证了反足细胞胚的性质,初步探讨了胚乳与反足细胞无配子生殖的关系。     

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.     

Embryological Study on Apomixis in a Sorghum Line SSA-1

The Developmental process of apomictic embryo sac and embryo in a sorghum (Sorghum bicolor (L.) Moench. ) line SSA-1 was observed under light microscope, using the method of conventional paraffin sectioning. The result showed that the apomictic development conforms apospory and diplospory. The uninucleate embryo sac underwent mitotic divisions for three times to form a seven-celled or eight-nuclei mature embryo sac including an egg, two synergids, two polar nuclei and three antipodals. The antipodals divided and multiplicated to form an antipodal mass. Moreover, aposporous multiarchesporial cells and multiple embryo sacs were infrequently observed. Without pollination, the egg divided autonomously to form a typical graminaceous mature embryo. The authors counted the apomictic sections in the whole sections and the result showed that the frequency of apomixis was 42%, indicating the facultative apomictic property in the line SSA-1. The characteristics of apomictic process in the line SSA-1 is also discussed.     

草地早熟禾胚胎学研究 Ⅲ．多胚囊及多胚现象

报道了草地早熟禾中多胚囊的起源、发育和结构。在１个胚珠中,大孢子母细胞周围可以有一到多个起源于珠心细胞的胚囊原始细胞,并可以发育成为多胚囊,其中具有两个胚囊的可以发育成为成熟胚囊。起源于珠心的体细胞无孢子生殖胚囊的发育属于山柳菊型。两个成熟胚囊中,都可以形成胚和胚乳,因而形成了具假多胚的种子。位于中部的胚来源于珠心还囊,属于无融合生殖形成的胚。两个以上的多胚囊不能形成成熟胚囊。     

Cytological and embryological studies on apospory in Bothriochloa ischaemum L

Cytological and embryological studies on apomictic species Bothriochloa ischaemum L. were carried out. Our studies revealed that the chromosome number of its root apical cells was 40, indicating that it was a tetraploid cytotype. During the stage of microsporogenesis, meiosis seemed irregular, as the pairing chromosome number of microspore mother cell was more than 20. It was often found that some chromosomes did not assemble in the equatorial plane or moved to the two poles of the cell, a few laggards were seen. Multiporate pollens (22.3%) were often observed. The studies showed that a high frequency (87.8%) of 1-3 or more aposporous embryo sacs developed in one ovule of the species. The mature aposporous sac was usually characterized by an egg cell and one polar nucleus. The egg cell could develop spontaneously into a large proembryo (100-200 microm) mass prior to anthesis. When several aposporous sacs occurred in the same ovule, usually 2 aposporous sacs were involved in pseudogamy and developed into separate endosperm masses in the same ovary. In the low frequency of mature seed, 13.5% twin-embryo seedlings could be obtained after mature seeds germinated.     

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.     

芒苞草形态学和胚胎学研究：Ⅱ.花药和胚珠发育的研究

芒苞草成熟胚珠为倒生型,薄珠心,双珠被。胎座为侧膜胎座向中轴胎座的过渡类型。胚囊发育为单孢蓼型。 成熟胚囊由印器,具二极核的中央细胞及三个反足细胞组成。助细胞呈倒梨形,极性不明显,珠孔端壁有角状的丝状器。中央细胞的二极核在受精前融合为次生核。 花药具二个小孢子囊,花药壁层为单子叶型,具分泌型绒毡层,小孢子母细胞减数分裂时,胞质分裂为连续型,四分体是左右对称式排列,成熟花粉粒为二细胞的。 在花药与胚珠发育过程中,多糖物质的消长是有规律的变化。     

甜菜无融合生殖单体附加系M14成熟胚囊的超微结构特征

以甜菜无融合生殖单体附加系M14（Betavulgaris,2n=18＋1）为实验材料,利用电子显微镜技术对成熟胚囊及其超微结构进行研究。结果表明：M14成熟胚囊包括1个卵细胞、2个退化的助细胞、1个具有次生核的中央细胞和3-6个反足细胞。其卵细胞具有3种不同的形态：（1）极性正常的卵细胞,细胞核位于合点端,细胞质含有大量核糖体、线粒体、内质网等细胞器;（2）细胞核位于细胞中央;（3）细胞核位于珠孔端,且后2种形态细胞器的种类与数量少。大多数胚囊中的2个助细胞在开花前已退化。中央细胞的次生核位于反足细胞附近;未经受精自发分裂前的卵细胞与中央细胞的细胞核大、核仁明显,细胞器的种类与数量多,呈现旺盛代谢活动特征,成为二倍体孢子无融合生殖过程中,卵细胞与次生核自发分裂的细胞学标志。