Anther ontogeny in Campsis radicans (L.) Seem. (Bignoniaceae)

In this study anther ontogeny of Campsis radicans (L.) Seem. was investigated by transmission electron microscopy and light microscopy with special reference to the development of the anther wall. The anther wall formation follows the dicotyledonous type. The differentiation in anther starts with the appearance of archesporial cells which undergo periclinal divisions to give primary parietal layer to the epidermal site and the primary sporogenous cells to the inside. The primary parietal layer also divides to form two secondary parietal layers. Later, the outer secondary parietal layer (spl1) forms the endothecium and the middle layer by periclinal division whereas the inner one (spl2) directly develops into the outer tapetum forming the inner most layer of the anther wall. The sporogenous tissue is generally organized in two rows of cells with a horseshoe-shaped outline. The remainder of the tapetum lining the sporogenous mass is derived from the connective tissue. The tapetum thus has dual origin and dimorphic. Anthers are tetrasporangiate. The wall of the anther consists of an epidermis, endothecium, middle layer, and the secretory type tapetum. Tapetal cells are usually binucleated. Epidermis and Endothecium layers of anther wall remain intact until the end of anther and pollen development; however, middle layer and tapetum disappear during development.     

Anther ontogeny in <Emphasis Type="Italic">Brachypodium distachyon</Emphasis>

Brachypodium distachyon has emerged as a model plant for the improvement of grain crops such as wheat, barley and oats and for understanding basic biological processes to facilitate the development of grasses as superior energy crops. Brachypodium is also the first species of the grass subfamily Pooideae with a sequenced genome. For obtaining a better understanding of the mechanisms controlling male gametophyte development in B. distachyon, here we report the cellular changes during the stages of anther development, with special reference to the development of the anther wall. Brachypodium anthers are tetrasporangiate and follow the typical monocotyledonous-type anther wall formation pattern. Anther differentiation starts with the appearance of archesporial cells, which divide to generate primary parietal and primary sporogenous cells. The primary parietal cells form two secondary parietal layers. Later, the outer secondary parietal layer directly develops into the endothecium and the inner secondary parietal layer forms an outer middle layer and inner tapetum by periclinal division. The anther wall comprises an epidermis, endothecium, middle layer and the secretory-type tapetum. Major documented events of anther development include the degradation of a secretory-type tapetum and middle layer during the course of development and the rapid formation of U-shaped endothecial thickenings in the mature pollen grain stage. The tapetum undergoes degeneration at the tetrad stage and disintegrates completely at the bicellular stage of pollen development. The distribution of insoluble polysaccharides in the anther layers and connective tissue through progressive developmental stages suggests their role in the development of male gametophytes. Until sporogenous cell stage, the amount of insoluble polysaccharides in the anther wall was negligible. However, abundant levels of insoluble polysaccharides were observed during microspore mother cell and tetrad stages and gradually declined during the free microspore and vacuolated microspore stages to undetectable level at the mature stage. Thus, the cellular features in the development of anthers in B. distachyon share similarities with anther and pollen development of other members of Poaceae.     

紫斑牡丹的花药发育和小孢子发生

紫斑牡丹的花药是在花芽发育的第３个年周期中,从雄蕊原厚基发育而来,花药壁按特有方式发生,主要特点是绒毡层与次生造孢细胞同源。花药由４个花粉囊组成,绒毡层属分泌型,中层３－４层,其中１－３层与药室内壁同步发育出纤维素壁加厚,并在花药成熟时宿存。小包子母细胞减数分裂同时开始,但不同时结束,分裂过程高度不同步。胞质分裂为同时型,四分体中小孢子排列呈正四面体形,减数分裂前期Ⅰ通常有Ｂ－染色体和染色体桥形。     

Embryology of Iris mandshurica Maxim. (Iridaceae) and its systematic relationships

Sporogenesis, gametogenesis, fertilization and embryogenesis of Iris mandshurica Maxim. were observed using the normal paraffin method. The results are as follows: the development of the anther wall following the dicotyledonous type consisting of four layers, the epidermis, the endothecium, one middle layer and the secretory tapetum. Fibrous thickenings develop in the endothecium when the anther is shed. Simultaneous cytokinesis during microsporogenesis results in a tetrahedral tetrad of microspores. Mature pollen grains are two-celled. The ovary is inferior and trilocular with axial placenta. The ovule is anatropous, bitegminous and crassinucellate. The archesporial cell below the nucellar epidermis undergoes periclinal division producing the primary parietal cell and the primary sporogenous cell. The primary parietal cell participates in the nucellar formation; the primary sporogenous cell differentiates directly as the megasporocyte. Successive cytokinesis in the megasporocyte usually produces the linear tetrad, and the chalazal megaspore of the tetrad develops into a Polygonum-type embryo sac. The fertilization mode is porogamy. The pollen tube enters into the embryo sac and discharges two sperm 16?C20?h after pollination. The fertilization is the postmitotic type of syngamy. The first division of the zygote is transversal. Endosperm formation is of the nuclear type. The systematic significance of the embryological characters of I. mandshurica is discussed.     

STUDIES IN THE BIGNONIACEAE. II. ONTOGENY OF DIMORPHIC ANTHER TAPETUM IN TECOMA

A developmental study of anther tapetum in Tecoma stans has shown that the hypodermal archesporial layer differentiates in each microsporangium by cutting off a primary parietal layer to the outside (epidermal) and a primary sporogenous layer to the inside (connective). The primary parietal layer divides periclinally, producing the outer secondary parietal layer, which by further divisions, forms the future endothecium and the middle layer. On epidermal side, the inner secondary parietal layer gives rise to tapetum. The remainder of the tapetum on the inside (connective) is contributed by the parenchymatous connective cells lying just outside the sporogenous cells. The tapetum thus follows the dicotyledonous type of ontogeny. It also shows a distinct dual origin and is structurally dimorphic.     

车桑子小孢子发生与雄配子体发育

为了解干热河谷区车桑子(Dodonaea viscosa)胚胎学特征及其结籽率低的原因,采用常规石蜡切片法和电镜扫描技术对车桑子小孢子发生、雄配子体发育和花粉的形态特征进行了观察。结果表明,车桑子花药具有4个花粉囊。完整的花药壁从外到内依次为表皮、药室内壁、2～3层中层细胞和绒毡层;绒毡层类型是腺质绒毡层。花药成熟期,中层、绒毡层均退化消失。小孢子母细胞进行同时型胞质分裂;四分体为四面体型结构。成熟的花粉为二细胞型。花粉近球形,外壁密布颗粒状纹饰,具有3条不构成合沟的萌发沟。雄性生殖发育过程出现的异常现象可能是干热河谷地区车桑子结籽率低的原因之一。     

开口箭大小孢子发生及雌雄配子体发育

利用石蜡切片技术,对百合科植物开口箭(Tupistra chinensis Baker)大小孢子发生及雌雄配子体发育进程进行胚胎学观察分析,以明确开口箭胚胎发育的特征,为百合科植物的研究提供生殖生物学依据。结果表明:(1)开口箭花药具有4个药室,花药壁的发育方式为基本型,由表皮、药室内壁、中层及绒毡层组成;绒毡层发育类型为分泌型,到四分体花药阶段绒毡层细胞开始解体退化,花药成熟时完全消失。(2)花粉母细胞减数分裂为连续型,依次形成二分体、四分体,四分体为左右对称形;成熟花粉为2-细胞花粉,具单萌发沟。(3)子房3室,倒生型胚珠6枚,双珠被,薄珠心;在花部的分化早期,由珠心顶端表皮下方分化出雌性孢原细胞,孢原细胞经过一次平周分裂形成周缘细胞和造孢细胞,造孢细胞发育为大孢子母细胞;大孢子母细胞第一次减数分裂后形成二分体,珠孔端的二分体孢子退化,合点端的二分体孢子继续第二次分裂,形成两个子细胞依次发育为二核胚囊、四核胚囊和八核胚囊;开口箭的胚囊发育类型为葱型。     

一品红雄配子体发育研究

一品红花药来源于雄蕊原基,花药由表皮(1层)、药室内壁(1层)、中层(1层)、绒毡层(1层)及造胞细胞组成,花药四室,药壁发育为双子叶型。小孢子发生和雄配子体发育是经由小孢子母细胞减数分裂形成四分体,该四分体胞质分裂为同时型,四分体排列为四面体型,小孢子再经有丝分裂形成2-核花粉。花药壁层的变化是表皮在花药成熟期消失,中层在四分体时消失,药室内壁在花药成熟期形成柱状纤维层。绒毡层在单核小孢子期径向伸长,有双核或多核,另外有的绒毡层细胞形成横隔或类胎座;进入2-核花粉期,绒毡层细胞分泌颗粒物进入药室,为非典型腺质绒毡层;进入成熟期绒毡层消失。同时观察到花药发育异常现象。     

Characterization and genetic mapping of a mutation (ms35) which prevents anther dehiscence in Arabidopsis thaliana by affecting secondary wall thickening in the endothecium

The male sterile mutant, ms35 , of Arabidopsis thaliana was produced by X-irradiation of seeds. The mutant produces fertile pollen, but is male sterile because the anthers do not dehisce. Anther development in ms35 plants occurs as in wild-type Arabidopsis until shortly after microspores are released from meiotic tetrads. Thereafter, in the wild type, bands of lignified, cellulosic secondary wall thickenings are laid down around the cells of the anther endothecium. In contrast, wall thickenings are not formed in the endothecium of the ms35 mutant. Development of other lignified tissues, for example the vascular tissue of the stamen, occurs normally in ms35 plants. In mutant anthers, as pollen maturation is completed, the stomium is cleaved but the anther wall does not retract to release pollen. The block in anther dehiscence in ms35 plants is specifically correlated with the absence of endothecial wall thickenings. The ms35 mutation represents the first genetic evidence in support of the proposed role of the endothecium in anther dehiscence. The ms35 gene was mapped to the top arm of chromosome 3 ( hy2 -(4.17±2.31 cM)- ms35 -(32.14±5.45 cM)- gl1 ).     

Dual Origin and Dimorphism of the Anther Tapetum in Alectra thomsoni Hook

The ontogeny of the dimorphic tapetal cells of Alectra thomsonihas been investigated. A layer of hypodermal cells first developsin each lobe of the anther and, from this, the primary parietallayer is cut off towards the outside of the lobe. Towards theinside, the primary sporogenous cells are formed. The primaryparietal layer undergoes a second periclinal division givingrise to two layers of cells; the outer of these develops intothe endothecium and the upper middle layer, while the inward-facinglayer forms the lower middle layer and part of the tapetum.The remainder of the tapetum is formed from the cells of theconnective tissue closest to the inner side of the sporogenousmass. No sterilization of the sporocytes has been observed.     

An Arabidopsis F-box protein regulates tapetum degeneration and pollen maturation during anther development

The Arabidopsis anther has a bilateral symmetry with four lobes, each consisting of four distinct layers of somatic cells from the outer to inner side: epidermis, endothecium, middle layer and tapetum. The tapetum is a layer of cells comprising the inner surface of the pollen wall. It plays an important role in anther development by providing enzymes, materials and nutrients required for pollen maturation. Genes and molecular mechanisms underlying tapetum formation and pollen wall biosynthesis have been studied in Arabidopsis. However, tapetum degeneration and anther dehiscence have not been well characterized at the molecular level. Here, we report that an Arabidopsis gene, designated reduced male fertility (RMF), regulates degeneration of tapetum and middle layer during anther development. The Arabidopsis dominant mutant rmf-1D overexpressing the RMF gene exhibited pleiotropic phenotypes, including dwarfed growth with small, dark-green leaves and low male fertility. Tapetum development and subsequent degeneration were impaired in the mutant. Accordingly, pollen maturation was disturbed, reducing the male fertility. In contrast, tapetum degeneration was somewhat accelerated in the RMF RNAi plants. The RMF gene was expressed predominantly in the anther, particularly in the pollen grains. Notably, the RMF protein contains an F-box motif and is localized to the nucleus. It physically interacts with the Arabidopsis-Skp1-like1 protein via the F-box motif. These observations indicate that the RMF gene encodes an F-box protein functioning in tapetum degeneration during anther development.     

华木莲花药的发生发育

报道华木莲花药的结构和小孢子的形成与发育。华木莲雄蕊多数、离生;每一花药具4个花粉囊。花粉囊由1层表皮、1层纤维层、2层中层和2层绒毡层细胞组成。腺质绒毡层在小孢子发生发育过程中,呈现出解体-恢复-解体直至消失的现象。减数分裂为同时型,四分体主要为左右对称和四面体形。撒粉时的成熟花粉为二细胞结构。     

垂花悬铃花雌雄配子体发育研究

对垂花悬铃花雄配子体发育观察表明,其花药由表皮(1层)、药室内层(1层)、中层(2层)、绒毡层(1层)及造孢细胞组成,花药四室,药壁发育为双子叶型。雄配子体发育经由花粉母细胞减数分裂形成四分体,该四分体胞质分裂为同时型,四分体排列方式为四面体型,十字交叉型及左右对称型;小孢子再经有丝分裂形成营养核和生殖核,生殖核再经有丝分裂形成3-核花粉。花药壁层的变化,在单核小孢子期,表皮细胞解体,仅留下痕迹;中层在花粉母细胞期逐渐消失;药室内壁在单核小孢子期开始纤维化;绒毡层在单核小孢子期消失,属变形绒毡层。雌配子体发育观察表明,其子房上位,5室,每室1个胚珠,胚珠弯生,中轴胎座,大多数胚珠发育停留在珠心形成阶段,极少数珠心形成一群孢原细胞及单核、双核胚囊。     

Localization of ubiquitin in anthers and pistils of Nicotiana

Ubiquitin-conjugated compounds were localized in anthers and pistils of Nicotiana alata by immuno-cytochemistry. In young anthers, antibodies to ubiquitin bound to callose cell walls surrounding pollen mother cells and to organelles in the endothecium. At the freespore stage, antibodies bound to circular-cell cluster cells subtending the stomium and to organelles and cell walls of endothecial cells. Near anther dehiscence, locular material was labeled. In pistils, cell walls of stylar transmitting tissue were labeled in a beaded pattern. Antibodies bound to a thin layer surrounding ovules, to the lining of embryo sacs, to cytoplasm of eggs and synergids, and to starch grains in central cells. Sites of localization were tissue- and time-specific, suggesting a regulatory role for ubiquitin in development of reproductive structures in flowering plants.     

大叶补血草的大、小孢子发生与雌、雄配子体的发育

系统地报道了大叶补血草(Limonium gmelinii (Willd.) Kuntze)的大、小孢子发生和雌、雄配子体的形成发育过程。主要结果如下：(1)小孢子母细胞减数分裂过程中的胞质分裂为同时型,四分孢子多为正四面体形, 也有少数为左右对称形;(2)成熟花粉为三细胞型,具3个萌发孔;(3)花药壁由5层细胞组成,最外层为表皮,其内分别为药室内壁、中层、绒毡层,绒毡层为变形型,花药壁的发育属于基本型;(4)大叶补血草的雌蕊由5心皮合生,子房1室,基生胎座,胚珠1个,拳卷型,双珠被,厚珠心;(5)孢原细胞发生于珠心表皮下,经一次平周分裂,形成造孢细胞,由造孢细胞直接发育成大孢子母细胞,大孢子母细胞减数分裂形成4个大孢子呈直线排列,合点端大孢子具功能,属于典型的蓼型胚囊发育。     

珍稀濒危植物大花万代兰的花粉团发育及其分类学意义

万代兰属的属间界限划定及其亲缘关系重建是兰科分类系统中的难解之谜。该研究采用常规石蜡切片技术观察了珍稀濒危植物大花万代兰的一对深裂花粉团的形成机制、花药壁发育模式、小孢子发生及雄配子体发育等的胚胎学特征。结果表明：(1)大花万代兰早期的花药原基分化出一对侧生药室,每个药室的小孢子囊中央分化出一条在花药成熟时会降解的不育隔膜组织,形成两个不等深裂的花粉团。(2)发育完整的花药壁有5~9层,包括2~6层药室内壁,符合多层型花药壁发育类型;绒毡层细胞为单核,腺质型,在花药成熟时,表皮、中层和绒毡层皆降解,仅留下2~6层纤维性加厚的药室内壁。(3)小孢子母细胞经过连续型胞质分裂形成正四面体和左右对称的小孢子四分体,小孢子四分体继续保持在同一个胼胝质内,完成有丝分裂形成了2 细胞型的四合花粉;四合花粉两两紧密排列,且由于隔膜组织的降解,最终发育为一对深裂的花粉团。根据现有兰花花药发育资料,分析了大花万代兰花粉团发育的胚胎学特征的分类学意义,为万代兰属错综复杂的系统分类提供了新资料。     

大百合小孢子发生和雄配子体发育研究

用常规石蜡切片技术和压片法对大百合小孢子发生和雄配子体发育进行观察。结果表明：花药4室,花药壁由表皮、药室内壁、中层和腺质绒毡层组成,花药壁发育方式为单子叶型,药室内壁部分细胞发育后期发生纤维状加厚。小孢子母细胞减数分裂过程的胞质分裂为连续型,四分体多数为左右对称型,偶有四面体型。成熟花粉为2细胞型,具1个萌发沟。经TTC法检验,成熟花粉生活力为86.3%。从小孢子的发生及雄配子体发育的整个过程看,未见异常现象,能形成大量正常的成熟花粉。     

毛竹的花药发育研究

竹类植物因有着较长的开花周期,其生殖生物学研究的报道相对较少。该研究采用石蜡切片与野外观察的方法,对毛竹花药的发育以及花药发育与花序的关系进行了研究。结果表明:毛竹的花药壁结构包括4层细胞:表皮细胞、药室内壁细胞、中层细胞和绒毡层细胞。药室内壁和中层都只有一层细胞,而且细胞形状较扁,花药发育后期药室内壁会逐渐降解,而中层则会完全解体消失。花药壁的发育为单子叶型,绒毡层为腺质型,而且只有一层,细胞径向较长,最后也会消失。小孢子母细胞减数分裂时,胞质分裂方式为连续型。形成的小孢子经一次有丝分裂后逐渐形成成熟花粉粒,大多为二细胞型,很少产生三细胞型。此外,还发现毛竹花药的发育与花序形态变化存在着相对应的关系。野外连续观察和切片发现,随着花序形态的不断发育变化,首先花药开始形成并不断分化,药壁备层也逐渐形成;接着小孢子逐渐成熟,备层也慢慢随之解体、消失;最后花药逐渐开裂并开始散粉。该研究结果不仅丰富了毛竹和竹类生殖生物学的研究内容,而且对毛竹种质的研究也具有重要意义。