被子植物生殖细胞的细胞壁

本文综述了国内外有关被子植物生殖细胞壁的资料,概述了它的形成、发育、性质和功能;在这些方面,生殖细胞壁的特征因植物种类而异。     

油松成熟花粉的细胞化学及超微结构研究

油松（ＰｉｎｕｓｔａｂｕｌａｅｆｏｒｍｉｓＣａｒｒ．）花粉由两个原叶细胞、一个生殖细胞和一个管细胞组成,其中两个原叶细胞在花粉成熟时已退化。生殖细胞具自己完整的壁。它与花粉贴近一面的壁与花粉内壁分开,仅侧面的壁与内壁连结。生殖细胞向管细胞一面的壁上有胞质通道。生殖细胞与管细胞有明显的分化,主要的差异表现在以下几个方面：（１）生殖细胞核的染色质凝集,而管细胞核的染色质分散,并具发达的核膜孔;（２）生殖细胞内不具微体,而管细胞的细胞质有较多的微体;（３）管细胞比生殖细胞有更丰富的内含物。虽然这两个细胞都含脂体和造粉质体,但前者的造粉质体极为丰富,而后者的造粉质体数量少。管细胞还含有少量的蛋白体,而生殖细胞则缺少这种贮藏物质。生殖细胞与管细胞内均含丰富的线粒体、多聚核糖体和少量的内质网及高尔基体。ＤＡＰＩ染色结果表明,生殖细胞及管细胞内均含丰富的细胞质ＤＮＡ。对油松细胞质遗传的方式及花粉壁的组成、结构和性质进行了讨论。     

中国鹅掌楸雄配子体发育的超微结构研究

中国鹅掌楸（ＬｉｒｉｏｄｅｎｄｒｏｎＣｈｉｎｅｓｅ（Ｈｅｓｍｌ．）Ｓａｒｇ．）雄配子体发育的超微结构观察结果表明,中国鹅掌楸雄配子体的发育符合大多数被子植物的发育特征,表现在：１．小孢子核在萌发孔的相对侧靠近小孢子壁处进行有丝分裂,分裂末期形成细胞板,而后进一步发育形成分隔营养细胞和生殖细胞的纤维素的壁。２．胞质分裂极不均等,营养细胞与生殖细胞大小悬殊,而且生殖细胞内不含质体。３．生殖细胞在发育过程中发生一系列位移和形态变化,生殖细胞向营养核移动,与营养核贴合时,细胞核内染色质高度凝缩;与营养核分离后,生殖细胞纤维素的壁才完全解体消失,同时质膜凹陷,细胞呈不规则形态。４．营养细胞内脂质小泡极性分布,形成生殖细胞的脂体冠。５,营养核在与生殖细胞贴合过程中形状由近圆球形变为近弯月形,但核仁、核膜界限清晰,染色质始终保持均一状态。对生殖细胞分裂前的位置变化及其与营养细胞间的关系进行了初步的探讨。     

玉竹生殖细胞壁在发育中的变化

应用光镜细胞化学和电镜方法,研究了玉竹生殖细胞发育过程中壁的结构和性质,证明了生殖细胞在刚形成时分隔它与营养细胞的壁是含胼胝质和纤维素的,从生殖细胞行将与内壁脱离开始,直至完全游离在花粉粒的营养细胞质中的发育时期,壁变薄和不显示苯胺蓝和荧光增白剂的荧光,但对ＰＡＳ是正反应的,当生殖细胞进入花粉管后和在有丝分裂前,细胞具有弱的ＰＡＳ正反应的包被,在结构形态上与曾在精细胞中描周质相似。研究结果证明玉竹     

小麦雄配子体的超微结构 Ⅰ.营养细胞和生殖细胞的形成

小孢子分裂的末期产生的成膜体,经离心的扩展后形成一个与内壁连结的细胞板,而后形成分隔营养细胞和生殖细胞的壁。由于胞质分裂高度的不均等性,形成大小悬殊的营养细胞和生殖细胞。在初期的生殖细胞和营养细胞的细胞质中,细胞器是没有差异的,包括线粒体、质体、内质网、高尔基体和核糖体。只有在胞质分裂初期看到微管。生殖细胞形成后,进一步的发育是逐渐脱离花粉粒的壁而成为游离的细胞,浸没在营养细胞的细胞质中。与此同时壁物质消失,变为一个被二层质膜所包围的裸细胞。当生殖细胞发育至游离的裸细胞时期,与营养细胞比较,显示明显的异质性,表现为生殖细胞中的质体不发育或退化,其它细胞器没有什么变化。相反,营养细胞中的质体和线粒体在数量上和大小上显著增长,在质体中迅速积累淀粉。对小麦生殖细胞暂时出现细胞壁的意义以及和营养细胞的异质性进行了讨论。     

西瓜生殖细胞向圆球形变化的超微结构研究

从超微结构水平上研究了西瓜生殖细胞从凸透镜形到圆球形的变化。细胞变圆过程中发生细胞器重新分布：刚产生的细胞中细胞器随机分布,变圆的细胞中细胞器分布呈现极性,与花粉壁相邻区域内质网堆叠而线粒体稀少,相反,向着花粉中心区域线粒体大量聚集而内质网稀少;细胞器重新分布表明生殖细胞在结构上建立了极性。细胞变圆有助于脱离花粉壁。细胞核对着花粉壁的一面有凹陷,凹陷中有内质网和核糖体。     

芍药雄配子体发育的超微结构研究

用透射电镜对芍药（Paeonia lactiflora Pall)雄配子体发育进行了研究。结果表明,芍药的小孢子母细胞在减数分裂末期Ⅰ时不形成细胞板,在减数分裂前期Ⅱ形成细胞器带,胞质分裂为同时型,生殖细胞刚形成时有呈PAS正反应的拱形壁,当生殖细胞还未完全脱离花粉内壁时,质膜间的壁物质消失,营养细胞中的脂体沿双质膜规律分布形成一单行的脂体带,在二胞花粉晚期,脂体带包围生殖细胞,形成脂体冠,花粉成熟时,包围生殖细胞的脂体消失,生殖细胞与营养核贴近,构成雄性生殖单位,成熟花粉为二细胞型。     

糜子的小孢子发育和雄配子体形成

1.小孢子四分体的排列方式为左右对称形、直列式和T形。2.花粉第一次右丝分裂前夕,部分细胞质定向集中并形成细胞质索。3.有丝分裂末期出现成膜体,而后形成分开营养细胞和生殖细胞的拱形壁。4.营养核移至萌发孔,拱形壁开始消失,生殖细胞经过变形变化并进入营养细胞的细胞质。当生殖细胞完成位移并和营养核紧密贴近后,它开始分裂。5.在生殖细胞的有丝分裂过程中,其纺锤体轴的方向不止一个;细胞质分裂是产生缢缩沟。6.由     

花粉生殖细胞的大量分离与纯化

被子植物的花粉生殖细胞是精子的前体,在生殖过程中占有重要地位。由于它被营养细胞与花粉壁包围,一般只能以花粉粒为单位进行研究。1986年以来,我们用压片法分离出花粉生殖细胞,作了有关细胞生物学研究,同时指出分离的生殖细胞用于离体培养与遗传操作的意义。作者参考了 Russell 分离精子的一步“渗透压冲击法”,建立了适于大量分离与纯化生殖细胞的“二步渗透压冲击法”(以下简称“二步法”)。此外,还作     

长豇豆花药和花粉的发育

长豇豆花药壁的发育为基本型。绒毡层周原质团型,小孢子母细胞减数分裂粗线期至末期Ⅱ,相邻小孢子母细胞间存在胞质通道。四分体多为四面体型,少数为左右对称型。生殖细胞刚形成时,壁呈ＰＡＳ负反应,以后为ＰＡＳ正反应。生殖细胞游离在营养细胞质内后,壁消失。成熟花粉为２细胞型。在小孢子早期,首次观察到在周原质团型绒毡层细胞外切向壁的外方,有很多直径约２－４μｍ,含不溶性多糖、蛋白质和抗乙酰解物质的球形颗粒,以后这些颗粒沿绒毡层细胞的径向壁进入药室,同时在小孢子壁和原生质体之间也出现了同样的颗粒。小孢子外壁增厚的同时,颗粒消失。关于这些颗粒的作用,有待进一步深入探讨。     

The formation of the generative cell in Polystachia pubescens (Orchidaceae)

Summary The formation and nature of the generative cell wall and the detachment mode of the generative cell from the intine in Polystachia pubescens were observed by LM and TEM. Vesicles evenly positioned within the phragmoplast fuse to form a cell plate that divides the microspore into the generative and vegetative cell. This cell plate consists of callose. Before the generative cell leaves the intine, however, the callose is completely resorbed and is not replaced by any other substance. The generative cell becomes detached from the intine by moving towards the centre of the pollen grain. A constriction formed thereby gives the generative cell a bulb-like appearance and leads ultimately to the generative cell being pinched off. Plasma-filled vesicles originating from the generative cell remain between the intine and the plasma membrane of the vegetative cell.     

Fusion Experiments of Isolated Generative Cells in Several Angiosperm Species

The generative cells used for fusion experiments were isolated from pollen grains of Zephyranthes candida and Lycoris radiata by “2-step osmotic shock” and from those of Hippeastrum vittata, Hemerocallis minor and Iris tectorum by “weak enzyme treatment” as reported previously. Using PEG method, fusions have been successfully induced between generative cells of the same species mentioned above, between generative cells of Z. candida and L. radiata, between generative cells and petal protoplasts in L. radiata, and between generative cells of L. radiata and hypocotyl protoplasts of Brassica napus. In all cases either homokaryons or heterokaryons could be obtained. Fusion of nuclei was observed sometimes in homokaryons of generative cells in L. radiata. The generative nuclei in fusion products could be well identified by labelling the generative cells before fusion with DAPI. FDA test demonstrated that most of the fusion products were viable. Factors affecting fusion efficiency including cell density, PEG concentration, duration of PEG treatment and effect of calcium ions were studied in fusion of generative cells in Z. candida. Our experiments indicate that isolated generative cells are likely to be deprived of cell wails and may be regarded as a special kind of protoplasts for direct fusion experiments.     

Male germ line development in Arabidopsis. duo pollen mutants reveal gametophytic regulators of generative cell cycle progression

Male germ line development in flowering plants is initiated with the formation of the generative cell that is the progenitor of the two sperm cells. While structural features of the generative cell are well documented, genetic programs required for generative cell cycle progression are unknown. We describe two novel Arabidopsis (Arabidopsis thaliana) mutants, duo pollen1 (duo1) and duo pollen2 (duo2), in which generative cell division is blocked, resulting in the formation of bicellular pollen grains at anthesis. duo1 and duo2 map to different chromosomes and act gametophytically in a male-specific manner. Both duo mutants progress normally through the first haploid division at pollen mitosis I (PMI) but fail at distinct stages of the generative cell cycle. Mutant generative cells in duo1 pollen fail to enter mitosis at G2-M transition, whereas mutant generative cells in duo2 enter PMII but arrest at prometaphase. In wild-type plants, generative and sperm nuclei enter S phase soon after inception, implying that male gametic cells follow a simple S to M cycle. Mutant generative nuclei in duo1 complete DNA synthesis but bypass PMII and enter an endocycle during pollen maturation. However, mutant generative nuclei in duo2 arrest in prometaphase of PMII with a 2C DNA content. Our results identify two essential gametophytic loci required for progression through different phases of the generative cell cycle, providing the first evidence to our knowledge for genetic regulators of male germ line development in flowering plants.     

Ultrastructural and Cytochemical Study on Mature Pollen of Pinus tabulaeformis

The pollen of Pinus tabulaeformis Cart. comprised two prothallial cells, a generative cell and a tube cell which degenerated at pollen maturation. The generative cell had its own cell wall, seperating from the intine of pollen, but with its side wall attached to the infine. Cytoplasmic channels were present on the side of the generative cell wall, which faced to the tube cell cytoplasm. The generative cell differed conspicuously from the tube cell. The main differences include: ( 1 ) The chromatin in the generative cell nucleus was condensed, but was dispersed and had numerous nueleare pores in the tube cell nucleus; (2)There was no microbody in the generative cell but many microbodies were present in the tube cell cytoplasm; (3)More inclusions were present in the tube cell than in the generative cell. Both the generative cell and the tube cells contained lipid bodies and amyloplasts in the cytoplasm, but there were more amyloplasts in the former. The tube cell also contained a few proteins which was absent in the generative cell. In addition, there were numerous mitochondria, polyribosomes, and a few endoplasmic reticulums and dictyosomes in the generative and tube cells. DAPI staining demonstrated numerous cytoplasmic DNA in both generative cell and tube cell. The mode of cytoplasmic inheritance, and the composition, structure and the nature of the pollen wall of P. tabulaefonnis are also discussed in this paper.     

The Development and Structure of the Generative Cell Wall in Polygonatum simizui

The developmental structure and components of the generative cell wall in Polygonatum sirnizui Kitag were studied by means of cytochemical and electron microscope observation. The early generative cell wall separating the generative and vegetative cytoplasm contains callose and cellulose. From the time when the generative cell detaches from the intine untill it is freely suspended in the cytoplasm of the vegetative cell, the wall becomes progressively thinner and does not show the specific fluorescence when stained with aniline blue and cai- cofluor white although it remains PAS positive. At later developmental stage when the generative cell moves into the pollen tube but before its initiation of mitosis, an envelope with weak PAS positive reaction appears on the surface of the cell. Its morphological nature is similar to that of the sperm cell discribed as the "periplasm”. This study proves that a cell wall is present in the generative cell of Polygonatum simizui throughout the developmental process, althrough changes in structure and components of the wall may occur. The properties of the generative cell wall at different stages, its significance in differentiation between generative and vegetative cytoplasm and translocation of nutrient materials, and the possible mechanism of the detachment of the generative cell from the intine are the subjects to discussion.     

土麦冬离体萌发花粉管中生殖细胞与营养核的动态变化

主要报道了土麦冬人工培养萌发花粉管中生殖细胞与营养核的动态变化。多数花粉管中,生殖细胞与营养核贴合后,开始进行有丝分裂,贴合时,营养核略呈弥散状态。在分裂早中期,生殖细胞与营养核分开,从贴合到分开大约经历３－５ｈ,精子形成后,不与营养核连接。ＤＡＰＩ对生殖细胞的有丝分裂有抑制作用。少数花粉管中,生殖细胞核进行无丝分裂,有缢裂和劈裂两种方式。生殖细胞核发生缢裂的花粉管中,未观察到生殖细胞与营养核的贴     

几种植物生殖细胞质膜表面的凝集素受体荧光标记

为进一步探讨从生殖细胞到精子的发育过程中细胞质膜表面凝集素受体的可能变化,及其与两类对凝集素标记有不同结果的精子的关系,用异硫氰酸荧光素标记的伴刀豆凝集素(Con A)、麦芽凝集素(WGA)和大豆凝集素(SBA)对蚕豆(Vicia faba L.)、鸢尾(Iris tectorium Maxim.)和朱顶红(Hippeastrum vittatum Herb.)的生殖细胞质膜表面的凝集素受体进行标记.结果显示:在不同植物中均有部分生殖细胞不能被凝集素探针标记,且在保持尾状形态的生殖细胞的表面发现有凝集素受体的极性分布.这可能是导致部分精子表面不能被同种凝集素标记的重要原因.此外,同一种凝集素受体在不同物种的生殖细胞上分布不一致,不同的凝集素受体在同一种植物的生殖细胞上的分布模式亦有不同.在蚕豆和鸢尾的生殖细胞表面均有这三种凝集素的受体.在朱顶红生殖细胞的表面有前两种凝集素的受体,分布比较均一,但是没有大豆凝集素的受体.此外,在具尾生殖细胞表面发现有凝集素受体极性分布的现象,为探讨精细胞功能及其表面糖蛋白分布的可能差异提供了重要启示.     

几种植物生殖细胞质膜表面的凝集素受体荧光标记

为进一步探讨从生殖细胞到精子的发育过程中细胞质膜表面凝集素受体的可能变化,及其与两类对凝集素标记有不同结果的精子的关系,用异硫氰酸荧光素标记的伴刀豆凝集素(Con A)、麦芽凝集素(WGA)和大豆凝集素(SBA)对蚕豆(Vicia faba L．)、鸢尾(Iris tectorium Maxim．)和朱顶红(Hippeastrum vittatum Herb．)的生殖细胞质膜表面的凝集素受体进行标记。结果显示：在不同植物中均有部分生殖细胞不能被凝集素探针标记,且在保持尾状形态的生殖细胞的表面发现有凝集素受体的极性分布。这可能是导致部分精子表面不能被同种凝集素标记的重要原因。此外,同一种凝集素受体在不同物种的生殖细胞上分布不一致,不同的凝集素受体在同一种植物的生殖细胞上的分布模式亦有不同。在蚕豆和鸢尾的生殖细胞表面均有这三种凝集素的受体。在朱顶红生殖细胞的表面有前两种凝集素的受体,分布比较均一,但是没有大豆凝集素的受体。此外,在具尾生殖细胞表面发现有凝集素受体极性分布的现象,为探讨精细胞功能及其表面糖蛋白分布的可能差异提供了重要启示。     

Structural features of isolated generative cells and their protoplasts from pollen of some liliaceous plants

Large quantities of intact generative cells and their protoplasts were isolated from pollen protoplasts of four liliaceous plants, and their structural features were investigated. The generative cells, liberated from the vegetative cell cytoplasm of the pollen protoplasts, were initially spindle-shaped with two long, oppositely oriented extensions, and were surrounded by two cell membranes, one on each side of a wall of uniform thickness. The generative nuclei, stained with 4′,6-diamidino-2-phenylindole (DAPI), showed ellipsoidal and highly condensed chromatin, whereas the generative cell cytoplasm, whose quantity was widely different from species to species, showed no fluorescence, suggesting the absence of plastid and mitochondria! DNA, although many mitochondria were present. The isolated generative cells, which were spindle-shaped at first, became spherical in shape in vitro. Immunocytochemistry and transmission electron microscopy revealed that this change was associated with the depolymerization of an axial array of microtubules present in generative cells in situ. These results are discussed in relation to the function of the generative cell within the bicellular pollen of angiosperms.