峨眉凤丫蕨配子体发育及卵发生的研究

用显微观察及透射电镜技术对峨眉凤丫蕨的配子体发育及卵发生过程进行了观察研究,以探讨其卵发生细胞学机制及蕨类植物演化关系。结果表明:(1)峨眉凤丫蕨孢子接种7～9d萌发,经丝状体和片状体阶段发育为心形原叶体,成熟原叶体雌雄同株,在原叶体基部产生精子器,在原叶体生长点下方产生颈卵器。(2)卵发生研究表明,峨眉凤丫蕨颈卵器产生于生长点下方的表面细胞,该细胞经2次分裂形成3层细胞,中间者为初生细胞,它经2次不等分裂产生卵细胞、腹沟细胞和颈沟细胞;新产生的卵与腹沟细胞间连接紧密,有发达的胞间连丝,随着发育,卵细胞与腹沟细胞之间产生分离腔,而腹沟细胞与卵细胞始终通过孔区相连;发育中期,卵核形成大量核外突;发育后期,在卵细胞外侧形成卵膜,孔区演变为受精孔,核外突数量减少。     

华东安蕨卵发生的超微结构观察

核心薄囊蕨是蕨类植物中的进化类群,但对受精作用具有显著影响的卵发生研究仍较少,该文利用超微技术对其中蹄盖蕨科的华东安蕨卵发生过程进行了研究,以进一步完善薄囊蕨植物卵发生的科学资料,为理解蕨类植物的有性生殖及演化机制奠定基础。超微结构观察显示:华东安蕨的幼卵和沟细胞在颈卵器中紧密联接;随后,在卵细胞上方出现了分离腔和临时细胞壁,但在卵细胞中间孔区处卵细胞和腹沟细胞始终联接在一起;分离腔中的无定形物质沉积在卵细胞的质膜外形成了1层加厚的卵膜,而在孔区处没有形成卵膜,该位置最后形成了受精孔。在进一步的卵发生过程中,卵细胞核变得高度不规则,形成了大量的核外突和核褶皱。     

阔叶鳞盖蕨配子体发育及卵发生的研究

采用显微镜和透射电镜对阔叶鳞盖蕨(Microlepia platyphylla)的配子体发育和卵发生过程进行了观察,以阐明其卵发生的细胞学机制,探讨其演化地位。阔叶鳞盖蕨孢子褐色,四面体形,具三裂缝,接种5~10d后孢子萌发,经丝状体和片状体阶段发育为心形原叶体,原叶体发育是铁线蕨型,通常为雌雄异株,精子器产生于不规则配子体的表面,颈卵器产生于心形原叶体生长点的下方,性器官是薄囊蕨型。卵发生研究表明,阔叶鳞盖蕨颈卵器产生于生长点下方表面细胞,经两次分裂形成了顶细胞、初生细胞和基细胞。其中初生细胞再经两次不等分裂产生卵细胞、腹沟细胞和颈沟细胞,此3个细胞通过胞间连丝紧密相连,随发育,腹沟细胞与卵细胞间形成了分离腔,但在孔区处始终通过胞间连丝相连,成熟卵细胞上形成了卵膜和受精孔,卵核表面产生了核外突,通过比较表明阔叶鳞盖蕨卵发生与蕨（Pteridium aquilinum）卵发生相似。     

乌蕨配子体发育及卵发生的显微观察

采用光学显微镜对乌蕨的配子体发育及卵发生的过程进行了研究,以阐明蕨类植物颈卵器发育特征,为揭示蕨类植物有性生殖机制以及鳞始蕨科的演化提供依据。结果表明:(1)乌蕨孢子黄褐色,具单裂缝,表面平滑或呈疣状纹饰;孢子接种12d萌发,萌发类型为书带蕨型,原叶体发育类型为铁线蕨型。(2)半薄切片观察表明,乌蕨颈卵器产生于原叶体生长点下方的表面细胞,即颈卵器原始细胞,该细胞经过两次分裂形成纵向3层细胞,最上层细胞发育为颈卵器的颈部壁细胞,中间层细胞即初生细胞再经过两次不等分裂产生颈沟细胞、腹沟细胞和卵细胞,此三细胞最初紧密贴合,随着颈卵器的发育,卵细胞与腹沟细胞间从两侧向中间产生分离腔,且腹沟细胞与颈沟细胞开始退化;分离腔逐渐向中间扩大,直至出现孔状结构,即受精孔;颈卵器发育后期,在卵细胞上表面形成染色较深的卵膜,颈沟细胞与腹沟细胞退化成絮状物。     

阔鳞瘤蕨(水龙骨科)卵细胞发育超微结构观察

水龙骨科是蕨类植物中最进化的类群,该文采用超微技术对水龙骨科的阔鳞瘤蕨(Phymatosorus hainanensis)卵发育过程进行观察,以完善薄囊蕨植物卵发生的资料,为揭示蕨类植物的有性生殖及演化机制奠定基础。结果表明:(1)幼卵、颈沟细胞、腹沟细胞通过胞间连丝紧密连接。(2)发育过程中,卵与腹沟细胞之间细胞壁显著加厚,将卵细胞与腹沟细胞隔离。(3)在壁的下方产生分离腔,内含大量不定形物质,但卵细胞与腹沟细胞在中间处始终相连。(4)分离腔中的不定形物质沉积在卵细胞质膜外形成了一层加厚的卵膜,而在连接区(孔区)处不形成卵膜,该位置最终形成了受精孔。(5)卵细胞核变得高度不规则,近成熟时卵核产生了大量的核外突。     

阔鳞瘤蕨颈卵器形成与卵发生的初步研究

运用光学显微镜与透射电镜对阔鳞瘤蕨（Phymatosorus hainanensis(Noot.) S.G.Lu）颈卵器形成和卵发生进行了研究。阔鳞瘤蕨颈卵器产生于雌配子体生长点下方分枝毛状体内侧。切片观察表明颈卵器起源于配子体表面的原始细胞,该细胞经两次不等分裂形成3个细胞,上下两个细胞分别发育为颈卵器的颈部与底部壁细胞,中间的细胞为初生细胞,含有较丰富的细胞器。初生细胞进行两次不等分裂产生颈沟细胞、腹沟细胞与卵细胞。成熟颈卵器内颈沟细胞和腹沟细胞退化,卵细胞上表面产生受精孔。本研究阐述了阔鳞瘤蕨颈卵器形成和卵发生的细胞学过程,对阐明蕨类植物雌性生殖器官的发育特征有一定的科学意义。     

Cytological features of oogenesis and their evolutionary significance in the fern Osmunda japonica

The development of the egg and canal cells in the fern Osmunda japonica Thunb. was studied during oogenesis by transmission electron microscopy. The mature egg possesses no fertilization pore and no typical egg envelope. In addition, an extra wall formed around the canal cells during oogenesis and apparently blocked protoplasmic connections between the egg and the canal cells. The periodic acid Schiff (PAS) reaction revealed that the extra wall was most likely composed of polysaccharides. Maturation of the egg was accompanied by the formation of a separation cavity above the egg and by some changes in the morphology of the nucleus and cytoplasmic organelles. The chromatin of the nucleus becomes condensed and the upper surface of the nucleus becomes closely associated with the plasmalemma. Amyloplasts in the egg cytoplasm were numerous and conspicuous, with most in close proximity to the nucleus. Finally, the cytoplasm on one side of the egg became vesiculated and the overlying plasmalemma was easily disrupted. These cytological features of the egg and the canal cells during oogenesis in O. japonica are markedly different from those of the leptosporangiate ferns and suggest a significant evolutionary divergence in reproductive cellular features between Osmundaceae and leptosporangiate ferns.     

海金沙配子体发育及卵发生的显微观察

用光镜观察海金沙(Lygodium japonicum)配子体发育和卵发生。海金沙孢子为四面体形,具三裂缝,孢子萌发方式为密穗蕨型(Anemia-type);配子体的发育形态多样,通常丝状体长至3~5个细胞时通过顶细胞纵分裂发育为片状体,进而发育为心形原叶体,在心形原叶体上可产生精子器和颈卵器。但在培养过程中也可产生10个细胞以上的丝状体,这种丝状体发育成的片状体和原叶体形态通常不规则,只产生精子器,不产生颈卵器。原叶体发育是铁线蕨型(Adiantum-type),性器官是薄囊蕨型(Leptosporangiate-type)。切片观察海金沙颈卵器产生于生长点下方表面细胞,经两次分裂形成了顶细胞、初生细胞和基细胞。其中初生细胞再经两次不等分裂产生卵细胞、腹沟细胞和颈沟细胞,此时三个细胞紧密相连,随发育,颈沟细胞和和腹沟细胞退化,卵周围形成了分离腔,光镜观察显示成熟卵细胞上无典型卵膜形成,未观察到受精孔的结构。     

水蕨颈卵器的形成与发育

主要运用电子透射显微镜技术对水蕨（Ceratopteris thalictroides（L．）Brongn）颈卵器形成与发育进行了研究。结果表明：水蕨颈卵器是由原叶体分生组织内颈卵器原始细胞形成的。该原始细胞经2次分裂形成3层细胞,上下两层发育成颈卵器颈部与底部的壁细胞,中层为初生细胞。初生细胞是颈卵器内雌配子发生的第一个细胞,该细胞经2次不等分裂形成1个卵细胞,1个腹沟细胞、1个双核的颈沟细胞。本研究首次阐明了水蕨颈卵器内细胞的发育顺序和特征。     

水蕨颈卵器的形成与发育

主要运用电子透射显微镜技术对水蕨(Ceratopteris thalictroides(L.)Brongn)颈卵器形成与发育进行了研究。结果表明:水蕨颈卵器是由原叶体分生组织内颈卵器原始细胞形成的。该原始细胞经2次分裂形成3层细胞,上下两层发育成颈卵器颈部与底部的壁细胞,中层为初生细胞。初生细胞是颈卵器内雌配子发生的第一个细胞,该细胞经2次不等分裂形成1个卵细胞,1个腹沟细胞、1个双核的颈沟细胞。本研究首次阐明了水蕨颈卵器内细胞的发育顺序和特征。     

地钱卵发育超微结构和细胞化学的研究

采用电镜和细胞化学技术对地钱(Marchantia polymorpha)卵发生过程进行了研究,根据卵发生过程中细胞化学和超微结构特征可将卵发育过程分为幼卵、中期卵和成熟卵3个阶段.幼卵阶段,卵细胞、腹沟细胞及颈沟细胞间有发达的胞间连丝,但卵与腹沟细胞间的胞间连丝很快退化,幼卵细胞内具大量透明的囊泡,均匀分布于细胞质中;卵发育中期,突出特征是卵细胞质内产生嗜锇性的脂滴,位于囊泡中,与此同时,腹沟细胞退化,其细胞质内产生大型囊泡,囊泡内分泌物与卵细胞外的物质类似,呈PAS反应阳性,表明该物质应为多糖类;卵成熟时,腹沟细胞和颈沟细胞完全退化,卵细胞外包被大量粘性多糖类物质,卵细胞核表面不规则,产生明显的核外突,众多的小泡围绕着细胞核,脂滴聚集成簇,卵细胞内其他细胞器不易区分.卵发育过程中,质体不含淀粉粒,线粒体退化,高尔基体相对发达.地钱卵发育的这些特征显著区分于蕨类植物.     

海金沙卵发生的组织化学研究

采用组织化学方法对海金沙（Lygodium japonicum （Thunb.） Sw.）卵发生进行了研究。高碘酸-锡夫反应（PAS反应）结果显示：颈沟和腹沟细胞外产生的黏性物质为多糖类物质;在卵细胞发生早期颈卵器细胞内均含有质体,且淀粉粒含量丰富,随着颈卵器的发育,卵细胞以及颈沟和腹沟细胞内淀粉粒数量和体积均逐渐减少,最后退化消失。苏丹黑B反应结果显示：海金沙颈沟和腹沟细胞外产生的黏性物质也含有脂类物质,而卵细胞内并未有明显脂类物质产生;卵细胞质膜处也并没有糖类或脂类物质的积累。本研究从组织化学角度佐证了海金沙的特殊性,即既有原始蕨类的特征,又有进化蕨类的特征。     

布雷菲德菌素A对蕨类植物卵发育的影响

以蕨类模式植物水蕨（Ceratopteris thalictroides L. Brongn.）为供试材料,设置不同质量浓度布雷菲德菌素A（BFA）分别处理10、20、30 h,采用光学显微镜和电镜对其树脂切片进行了观察;在此基础上,进行高碘-酸锡夫反应（PAS）和苏丹黑B反应。结果显示：对照组（未经BFA处理）发育卵中期的水蕨卵细胞较大,核仁呈圆形,细胞内高尔基体、内质网等细胞器完整;卵细胞和腹沟细胞间的受精孔清晰可见,二者间的分离腔内仅有极少量的泡状分泌物;卵膜较厚,有明显的层次。而处理组卵细胞的受精孔和卵膜不典型,由数量较多、大小不一的囊泡组成;受精孔下方有较多的线粒体和少量的高尔基体分布;高尔基体、内质网等膜性细胞器已断裂;细胞核上方和卵膜下方均分布着大量的嗜锇性囊泡,分离腔中充满了絮状物质。组织定位显示：对照组的分离腔较空,而处理组分离腔内充满着多糖类物质。综上所述,BFA会对卵细胞中的内质网和高尔基体等膜性细胞器造成破坏,影响分泌系统的正常功能,进而影响卵膜及受精孔的形成。本研究结果为进一步探索受精孔形成的机制以及蕨类植物生殖生物学的研究奠定了基础。     

地钱颈卵器发育和卵发生的显微观察及细胞化学研究

对地钱（Marchantia polymorpha）颈卵器发育和卵发生过程进行了显微观察和细胞化学的研究,颈卵器起始于原始细胞,该细胞呈乳突状,经横分裂产生基细胞和顶细胞,顶细胞经3次纵斜向分裂和1次横分裂产生初生细胞,初生细胞是颈卵器内的第一个细胞,经横分裂产生中央细胞和颈沟母细胞,前者产生1个腹沟细胞和1个卵细胞,后者最终产生4个颈沟细胞。颈卵器的成熟表现为颈部显著伸长和腹部膨大,卵细胞成熟时具有不规则的核,细胞质内含有丰富的囊泡和颗粒物,卵细胞周围充满粘性物质,细胞化学研究表明,该粘性物质为多糖,卵细胞质中深染色的颗粒可能为脂类物质,腹沟细胞自产生后就逐渐退化,颈沟细胞的退化迟于腹沟细胞,其数量通常为4个,偶尔可见5个颈沟细胞或具有双核的现象。     

Ultrastructure of Oogenesis in Dryopteris crassirhizoma Nakai

The ultrastructure ofoogenesis in Dryopteris crassirhizoma Nakai has been investigated using transmission electron microscopy. The nucleus in the young egg is rounded with an uneven outline. As it develops, it becomes amoeboid and extends nuclear protrusions that are not only sac-like nuclear evaginations like those often seen in the oogenesis of other ferns, but also mushroom-like and finger-like, with an opening at their end allowing the nucleolus material to flow out from the openings. This has not been observed previously. The nuclear protrusions differ from Dryopterisfilix-mas (L.) Schott. in the absence of sheets of nuclear membrane in the form of a closed ring. As the egg matures, the nucleus transforms into a tuber-like structure with a smooth surface, lying transversely in the egg cell. In the immature egg, vesicles almost encircle the nucleus twice and are most remarkable. In the maturing egg, the vesicles are distributed at the periphery, except for at the top of the egg, and affect the formation of the separation cavity and extra egg membrane. Simultaneously, vesicles from the venter canal cell move to the egg and take part in the formation of separation cavity and extra egg membrane. In the mature egg, a large number of small vesicles containing fragments of lamellae or osmiophilic material emerge from the cytoplasm. The origin of these vesicles is obscure. Irregular plastids containing a cylindrical starch grain dedifferentiated progressively.Mitochondria seem to have been undeveloped during the process, but return to normal at later stages of oogenesis. There is a high frequency of ribosomes in the mature egg. Microtubules, rarely seen in the eggs of D.filix-mas (L.) Schott. and Pteridium aquilinum (L.) Kuhn, have been observed inside the plasmalemma of the maturing egg in D. crassirhizoma.     

Ultrastructure of Oogenesis in Dryopteris crassirhizoma Nakai

The ultrastructure of oogenesis in Dryopteris crassirhizoma Nakai has been investigated using transmission electron microscopy. The nucleus in the young egg is rounded with an uneven outline. As it develops, it becomes amoeboid and extends nuclear protrusions that are not only sac-like nuclear evaginations like those often seen in the oogenesis of other ferns, but also mushroom-like and finger-like, with an opening at their end allowing the nucleolus material to flow out from the openings. This has not been observed previously. The nuclear protrusions differ from Dryopteris filix-mas (L.) Schott. in the absence of sheets of nuclear membrane in the form of a closed ring. As the egg matures, the nucleus transforms into a tuber-like structure with a smooth surface, lying transversely in the egg cell. In the immature egg, vesicles almost encircle the nucleus twice and are most remarkable. In the maturing egg, the vesicles are distributed at the periphery, except for at the top of the egg, and affect the formation of the separation cavity and extra egg membrane. Simultaneously, vesicles from the venter canal cell move to the egg and take part in the formation of separation cavity and extra egg membrane. In the mature egg, a large number of small vesicles containing fragments of lamellae or osmiophilic material emerge from the cytoplasm. The origin of these vesicles is obscure. Irregular plastids containing a cylindrical starch grain dedifferentiated progressively.Mitochondria seem to have been undeveloped during the process, but return to normal at later stages of oogenesis. There is a high frequency of ribosomes in the mature egg. Microtubules, rarely seen in the eggs ofD. filix-mas (L.) Schott. and Pteridium aquilinum (L.) Kuhn, have been observed inside the plasmalemma of the maturing egg in D. crassirhizoma.     

普通针毛蕨颈卵器和卵的发育

蕨类植物卵发生是有性生殖研究的重要内容。真水龙骨类II的卵发生尚无人研究, 本文对该类群中的普通针毛蕨(Macrothelypteris torresiana)卵发生过程进行了光镜和透射电镜研究。结果显示: 卵细胞刚形成时, 与腹沟细胞紧密相连, 随着卵进一步发育, 卵细胞和腹沟细胞之间逐渐形成分离腔, 但孔区处卵细胞和腹沟细胞始终相连。随后, 卵细胞上表面有不定型物质堆积在质膜外, 形成一层加厚的卵膜, 孔区处没有卵膜覆盖的位置最后形成受精孔。在卵发育后期, 卵细胞核变得不规则, 近成熟时卵核产生大量核外突。卵发育过程中卵膜的出现、受精孔的产生以及核外突等特征, 与进化的真水龙骨类中其他蕨类植物的卵发生研究结果相似, 与薄囊蕨类中原始基部类群的卵发生现象有显著差别。由此可见, 普通针毛蕨属于进化类型。依据卵发生中卵膜和受精孔等特征推测原始薄囊蕨类经过里白类、桫椤类, 最终演化为水龙骨类。     

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.     

Ultrastructure of the Mature Egg and Fertilization in the Fern Ceratopteris thalictroides

The ultrastructure of the mature egg and fertilization in the fern Ceratopteris thalictroides (L.) Brongn. were observed by transmission electron microscopy. The results revealed that the mature egg possesses an obvious egg membrane at the periphery of the egg. Furthermore, a fertilization pore was identified in the upper egg membrane of the mature egg. The structure of the pore is described for the first time. The fertilization experiment indicated that spermatozoids crowd into the cavity above the egg through the neck canal of the archegonium; however, only one of these can penetrate into the egg through the fertilization pore. Immediately on penetration of the spermatozoid, the egg begins to shrink. The volume of the fertilized egg decreases to almost one-half that of the unfertilized egg. As a result, the protoplasm of the fertilized egg becomes dense and opaque, which may lead to a situation where the organelles of both the egg and the fertilizing spermatozoid become indistinguishable. Simultaneously, abundant vesicles containing concentric membranes or opaque materials appear near the fertilization pore in the cytoplasm of the fertilized egg. These vesicles are considered to act as a barrier that prevents polyspermy. The present study provides a new insight into the ultrastructure of the mature egg and the cytological mechanism of fertilization in ferns.