多羽实蕨胚胎发育的研究

利用人工培养和石蜡切片法研究了多羽实蕨(Bolbitis angustipinna(Hayata)H.Ito)胚胎发育过程。合子第一次分裂面垂直于原叶体纵轴且平行于颈卵器颈部;第二次分裂面平行于原叶体纵轴且垂直于颈卵器颈部;第三次分裂面同时平行于原叶体纵轴和颈卵器颈部。经多次分裂形成球形胚胎,球形胚胎的外上和外下区域几乎同时分别发育出第一叶顶端细胞和第一根顶端细胞,继而分别斜向分裂产生第一叶原基和第一根原基。随后,第一叶原基迅速分裂,最早突破帽状体形成第一幼叶;第一根原基的分裂速度稍慢,晚于第一叶突破帽状体形成第一根。并讨论了胚胎发育的系统学问题。     

薄囊蕨胚胎发育模式——以华北鳞毛蕨为例

以鳞毛蕨科的华北鳞毛蕨为材料,在模拟自然条件下人工培养配子体世代,用石蜡切片详细观察记录了胚胎发育全过程,以建立更详细的薄囊蕨胚胎发育模式,为探讨薄囊蕨与其它类群的系统演化关系及生殖生物学提供依据。结果表明:(1)华北鳞毛蕨的胚胎发育垂直于配子体平面和背腹轴,符合俯卧型发育模式,合子第一次分裂平行于颈卵器的长轴方向;胚胎在16细胞时期才能够确定器官发生的原始细胞,且第一叶原基的产生先于第一根原基;海马胚时期第一叶原基和第一根原基突破帽状体形成具有明显维管束结构的第一叶和第一根;胚胎发育过程中有游离核的存在。(2)该文绘制了从合子到第一叶和第一根成熟的发育过程,包括胚胎早期细胞的分裂方式、细胞核及其核仁的特征、器官的发生顺序及其相互关系等14个点线图,总结出薄囊蕨胚胎发育的详细模式;该模式支持Nayar的"根叶学说",并主张薄囊蕨和种子植物的茎在本质上是不同的,二者是平行发展的两个类群。     

荚果蕨胚胎发育的研究

利用石蜡切片法研究了荚果蕨（Matteuccia struthiopteris(L.) Todaro）胚胎发育过程。合子第一次分裂,分裂面垂直于原叶体纵轴且平行于颈卵器颈部;第二次分裂面平行于原叶体纵轴且垂直于颈卵器颈部;第三次分裂面同时平行于原叶体纵轴和颈卵器颈部。经多次分裂的球形胚胎,胚胎的外上和外下区域几乎同时分别发育出第一叶顶端细胞和第一根顶端细胞。随着发育的进行,它们分别斜向分裂产生第一叶原基和第一根原基。随后,第一叶原基迅速分裂,突破帽状体形成第一幼叶;而第一根原基的分裂速度稍慢,第一根发育速度稍慢于第一叶。     

海金沙胚胎发育的研究

利用石蜡切片法研究了海金沙胚胎发育过程。合子的第一次分裂面垂直于颈卵器的长轴,产生两个相等的子细胞,靠近颈卵器颈部的营养器官原始细胞和远离颈部的基足原始细胞。前者发育成子代孢子体的营养器官,后者发育成基足。胚胎在32细胞阶段后,第一叶顶端细胞与第一根顶端细胞几乎同时发生。第一叶突出帽状体之后,由第一叶基部保留下来的茎干顶端细胞产生第二叶。据营养器官的形态结构判断,在海金沙胚胎发育中最早出现的营养器官是叶和根。     

濒危孑遗蕨类植物云贵水韭的胚胎发育

云贵水韭(Isoetes yunguiensis)是云贵高原特产的孑遗蕨类植物,是研究云贵地区古生态和植物演化的活化石,是国家一级保护物种,生殖过程及其濒危原因尚未查明。本文在实现人工繁殖、获得足量研究材料的条件下,用常规半薄切片法,连续观察了云贵水韭胚胎发育的全过程。其结果表明:(1)合子没有休眠期;(2)合子分裂面与颈卵器长轴呈约30°夹角;(3)首先发育出第一叶原基和第一根原基,且前者早于后者;(4)叶舌原始细胞在叶片发育初期就开始了细胞分裂;(5)颈卵器开口端细胞常出现坏死溃败现象并直接影响胚胎发育;(6)容易出现畸形胚胎;(7)片状结构发育迅速,对第二叶原基和第三叶原基有很好的保护作用;(8)早期维管分化顺序等。探讨了云贵水韭胚胎阶段的生殖生物学规律及其生殖濒危机制,分析了原始维管植物营养器官演化的溯祖形态,为云贵水韭的有效保护积累了技术资料。     

小麦种子根的发育解剖

小麦胚胎发育过程中通常形成5条幼根(少数可形成6条),这些根统称为种子根,中间最先发生的为初生根.初生根的原基在胚胎发育的早期就在胚轴的一侧发生,原基细胞由不规则到规则排列。侧生种子根的原基在胚胎发育后期才出现,通常成对发生,并且是由胚轴上的节(盾片节和胚芽鞘节)维管束外方的细胞形成。侧生种子根的发育明显较初生根的快,分化能力也较强,后生木质部导管母细胞出现早,数目较多.因此,小麦胚胎发育过程中从胚轴上形成的这些侧生的种子根,形态上,仍应看作是一些不定根,其结构特征与后来形成须根系的不定根的比较近似。     

福建柏后期胚的发育

福建柏幼胚于7月中旬进入多细胞的幼胚阶段,其外形呈圆柱状。8月初,根原始细胞开始分化;9月底胚基本成熟。后期胚发育主要是胚各种组织和器官的分化:首先是胚游离端及其相对部分的形成;其次是在离游离端约10个细胞的深处,出现弧形排列的细胞,弧底正中出现几个根原始细胞,然后再由这些根原始细胞相继向上分化原形成层和皮层,向下分化根冠组织。最后是子叶原基及苗端的分化。成熟胚的下胚轴及子叶发达,约各占胚全长的40%。根冠较不发达,只占10%,其余部分是退化的胚柄。本文并就福建柏后期胚胎发育过程中的淀粉动态,作了扼要报道。     

心外膜的起源与发育

长期以来,心外膜被认为是起源于胚胎发育早期心管的最外层原始心肌.然而近来的研究表明,心外膜并非起源于原始心肌,而是起源于一个叫做前心外膜浆膜的原始心外原基.进一步研究表明,前心外膜浆膜和新形成的心外膜为心外膜下、心肌之中的相关组织以及冠状血管提供了几乎所有的细胞原基.最近的信息甚至表明心外膜及其它前心外膜起源的细胞在胚胎心肌和心传导系统的分化中起着重要的调节作用.     

胡杨不定根原基发生的分生细胞结构特征及内源激素变化分析

以胡杨实生苗去根插穗为试材,采用显微技术、气质(GC/MS)联用技术和同工酶分析技术观察和研究了外源3-吲哚丁酸(IBA)对其不定根原基(干细胞)形成的影响.结果表明:(1)胡杨插穗培养在无IBA的培养基上,36 h时有大核细胞发生,60 h时大核细胞聚集成团形成根原基,72 h时生成不定根;而添加了IBA的培养基上插穗培养60 h时大核细胞分散,出现许多薄壁细胞,72 h时薄壁细胞变大,没有根原基的形成和根的发生,表现出细胞组织愈伤化,不再分化出干细胞.添加外源IBA抑制了胡杨插穗不定根形成.(2)组织化学观察显示,在无IBA的培养基上的插穗,60 h时具双环状核仁的干细胞细胞质浓,富含蛋白质;而此时添加了IBA的插穗,具双环状核仁的细胞细胞质很少,蛋白质含量也少.(3)整个胡杨不定根形成的过程中,内源激素IAA和ABA可能作为诱导根原基发生的重要信号分子;内源激素IAA和GA3处于一个较稳定状态,有利于不定根的形成.(4)过氧化物酶(POD)2b酶带的持续表达有利于根原基的诱导;淀粉酶在60 h时表达增强,是根原基发育的标志;根原基诱导时不需要酯酶,而根原基发育时需要酯酶.     

黄瓜花原基的形成及与Ca~(2+)的关系

以黄瓜为试验材料研究了肉眼可见的花原基突起之前 ,花原基早期的分化过程。结果显示花原基分化和开花的起始节位是第一真叶节 ;肉眼可见花原基突起前早期的分化是在叶腋亚表皮部位形成一个球形的花原基起始细胞团 ,此细胞团进一步分裂、扩大形成肉眼可见的花原基突起 ;第一真叶节的花原基起始细胞团分化集中发生于 6～ 7d苗龄时期 ;Ca2 + 在花原基起始细胞团细胞中主要分布在细胞壁和细胞间隙 ,而在非起始细胞团的叶腋亚表皮细胞则主要分布在液泡中 ,并对Ca2 + 在花原基起始细胞团分化中的作用进行了讨论。     

THE DEVELOPMENT OF THE ACHENE OF POLYGONUM PENSYLVANICUM: EMBRYO,ENDOSPERM, AND PERICARP

A study was made of the ontogeny of the achene of Polygonum pensylvanicum L. from fertilization to maturity. The proembryo is classified as the Polygonum Variation, Asterad Type. Cotyledons are initiated three days after anthesis, and by the fifth day procambium is present in the embryo axis. At approximately seven days after anthesis, the embryo begins to curve and occupy a marginal position in the ovary. By ten days the first foliage leaf primordium is initiated at the stem apex of the embryo. At maturity the embryo consists of two cotyledons, a plumule composed of the stem apex and one leaf primordium, and a hypocotyl with a well-developed radicle. Endosperm nuclei begin to divide before the first division of the zygote. Cell wall formation begins in the endosperm at the micropylar end of the embryo sac and proceeds toward the chalazal region. By the fifth day the endosperm is completely cellular, except for a basal projection; and a peripheral meristem has been established. At approximately ten days the peripheral meristem ceases periclinal cell division and becomes the aleurone. At the time of fertilization the ovary wall has its full complement of cell layers. The walls of the outermost cells elongate and become convoluted. Subsequent thickening and lignification of these cell walls produce the hard epicarp of the mature achene.     

The Embryonic Development Study on Isoetes yunguiensis,an Endangered and Relict Pteridophyta

Isoetes yunguiensis is a specialty relict fern of Yunnan Guizhou Plateau,which is a national level protected species called living fossil of the study on paleoecology and plant evolutionary in Yunnan and Guizhou area, but its reproduction and endangered mechanism is unclear. On the basis of implementation of artificial breeding and acquisition of adequate research materials, the authors observe the embryonic development of Iyunguiensis using thin sectioning. The main results of observation of the embryonic development are as follows: (1) The zygote doesn’t have the period of dormancy; (2) The angle between the division planes of zygote and the long axis of archegonium is about 30°; (3) The first leaf primordium and the first root primordium develop first. However, the first leaf primordium develop earlier than the first root primordium; (4) The initial cells of ligule begin to divide since the initial stage of the development of leaf; (5) The cells of the open end of archegonium often appear necrosis and affect the embryonic development; (6) The embryo malformation is easy to happen; (7) The sheet structure develop fast, and it provide good protect for the second and third leaf primordium; (8) The order of early vascular development. The article explore the reproductive biology regular and reproductive endangered mechanism of Iyunguiensis. The coalescent form of the original evolution of vegetative organs of vascular plants is analyzed. This article also accumulate technical data for protection of Iyunguiensis.     

ON THE EMBRYOGENY OF SCHIZAEA DICHOTOMA

The zygote of Schizaea dichotoma divides transversely and the outer cell thus produced divides longitudinally. The three cells probably establish the organs: root, stem, and foot. The first leaf is not embryonic in origin but forms on the relatively old sporeling. Some general comments on gametophyte and embryo phylogeny are presented.     

The ultrastructure of zygotic embryo development in pearl millet (Pennisetum glaucum; Poaceae)

The ultrastructure, morphology, and histology of zygotic embryogenesis in pearl millet (Pennisetum glaucum) were examined using light and electron microscopic techniques. Embryogenesis was initially characterized by the presence of a vacuolated egg cell and zygote. The increased presence of Golgi bodies in the zygote suggested it was metabolically more active than the egg cell. The first zygotic division resulted in a densely cytoplasmic apical cell and a highly vacuolated basal cell. The club-shaped proembryo displayed a large amount of endoplasmic reticulum (ER) and ribosomes, very few lipids, and a continuous gradient of vacuoles from the highly vacuolated basal suspensor cells to the densely cytoplasmic apical cells. The embryo had well-defined parts by 8 days after pollination, including shoot and root meristems, coleoptile, scutellum, provascular system, and the first leaf primordium. Large increases in ER, lipids, starch, and vacuoles occurred in the scutellum during the maturation of the embryo, except in the provascular cells. Throughout zygotic embryogenesis, embryo cells were connected by plasmodesmata except where intercellular spaces occurred. Ultrastructural, morphological, and histological observations of zygotic embryogenesis in pearl millet are in agreement with previous reports for other grass species.     

Organ identity of the thalloid plant body of Griffithella hookeriana and Polypleurum stylosum – Podostemoideae (Podostemaceae)

The morphological nature of the thalloid plant body of podostemads has remained controversial for long. The present investigation was carried out on two members of the Podostemoideae i.e. Griffithella hookeriana and Polypleurum stylosum to understand their organ identity. The origin of the plant body was traced from the embryo by germinating the seeds under aseptic conditions. Mature embryo of both species does not show an identifiable shoot apical meristem (SAM) and root apical meristem (RAM). Upon germination, the radicular pole does not form a primary root but differentiates adhesive hairs. At the cotyledonary junction, SAM is initiated that differentiates 6–9 leaves apically (primary axis) and a primordium laterally. This primordium subsequently emerges from the hypocotyl and develops into a thalloid plant. The latter has been interpreted as a flattened stem because it not only shows tunica-corpus like organization at the tip but also originates endogenously from the same SAM that forms the `primary axis'.     

The asymmetric division of the Arabidopsis zygote: from cell polarity to an embryo axis

During plant embryogenesis, a simple body plan consisting of shoot and root meristem that are connected by the embryo axis is set up by the first few rounds of cell divisions after fertilization. Postembryonically, the elaborate architecture of plants is created from stem cell populations of both meristems. Here, we address how the main axis (apical-basal) of the plant embryo is established from the single-celled zygote and the role that the asymmetric division of the zygote plays in this process. We will mainly draw on examples from the model plant Arabidopsis, for which several key regulators have been identified during the last years.     

Embryogenesis in Najas marina L.: Structural and histochemical approach

In Najas marina L. few polysaccharide grains are observed in zygote, basal cell and embryonal cells until the initiation of embryonic shoot-apex. With the formation of the shoot-apex, numerous polysaccharide grains engorge in the embryonal cells. The basal cell wall, subjacent to the nucellus, stains intensely with PAS (Peiodic Schiff's)-reaction. The concentration of proteins and RNA increases in the basal cell.Interestingly, the embryo shows intraseminal germination. The cells of embryonic shoot-apex, embryonic leaves, root primordium and procambial cells show a few polysaccharide grains while the cells of hypocotyledonary and cotyledonary regions are engorged with polysaccharide (starch) grains. Uniform distribution of proteins and RNA is observed in the embryonic shoot-apex, embryonic-leaves, root primordium and procambium, but the cells of hypocotyledonary and cotyledonary zones exhibit a low profile for these metabolites. The initial root-primordium remains quiescent. Three or 4 epidermal cells, subjacent to this quiescent primordium, differentiate; show densely stained, polarised, protein bands; and act as the future root primordium.The nucleus of the basal cell becomes polyploid and densely stains for proteins, RNA and DNA. At the globular proembryo stage, numerous nucleolar bodies migrate towards the periphery of the nucleus and at the 3-leaf embryo stage, these nucleolar bodies, rich in proteins and RNA, are located in the cytoplasm revealing nucleo-cytoplasmic interaction. The basal cell that never divides, but only enlarges, is persistent in the mature seed.     

Embryology of Ceratopteris richardii (Pteridaceae, tribe Ceratopterideae), with emphasis on placental development

This comprehensive study of early embryology in Ceratopteris richardii combines light microscopy with the first ultrastructural evaluation of any pteridophyte embryo. Emphasis is placed on ontogeny of the foot and placental transfer cells. The embryology of C. richardii shares many similarities with that of other polypodiacious ferns while exhibiting distinctive division patterns. Formative embryonic stages have been reconstructed into three-dimensional models for ease of interpretation. The zygote divides perpendicular to the gametophyte plane and anterioposterior axis. This division establishes a prone embryological habit that maximizes rapid independent establishment of a leaf-root axis in a cordate gametophyte. After the formation of a globular eight-celled stage, initials of the first leaf, and root and shoot apical meristems are defined early by discrete formative divisions. Concomitantly, the foot expands and differentiates to transport nutrients from the gametophyte for the developing embryonic organs. Transfer cell wall ingrowth deposition begins in the gametophyte placental cells before the adjacent sporophyte cells just after the eight-celled stage. These observations provide an anatomical framework for future comparative developmental genetic studies of embryogenesis in free-sporing plants.