倒地铃花的形态分化与花药结构研究

利用体视显微镜、半薄切片和超薄切片法对倒地铃(Cardiospermum halicacabum Linn.)雄花和假两性花开花过程及花药发育过程进行了观察和比较研究。结果显示:(1)花蕾发育早期,倒地铃雄花和假两性花的花蕾形态没有区别;花蕾发育后期,雄花雌蕊退化,假两性花雌蕊继续发育,花蕾外部形态出现差异;开花时雄花花药开裂,假两性花花药不开裂。(2)倒地铃雄花和假两性花均具四室花药,呈蝶形;花药壁细胞从外到内依次是表皮、药室内壁、中层(2层)和绒毡层;花药壁发育为基本型,绒毡层为单核分泌型,四分体为四面体型,花粉粒两核;开花时雄花和假两性花中层都有残留;小孢子液泡化时,绒毡层开始降解,两核花粉粒时,假两性花绒毡层降解较快。(3)雄花药室内壁次生加厚完全,裂口区发育,连接同侧花粉囊的连接组织降解,花药开裂;假两性花药室内壁次生加厚不完全,具唇形细胞,药隔细胞壁未降解,同侧花粉囊未连通,花药四室,不开裂;假两性花成熟花粉粒细胞质稀少,内壁不完整。本研究结果表明,倒地铃的雄花是由两性花在发育早期雌蕊停止发育形成的,假两性花则由两性花在发育晚期雄蕊功能退化造成的。     

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。     

柠条锦鸡儿小孢子发生和雄配子体发育

利用常规石蜡切片技术对柠条锦鸡儿小孢子发生及雄配子体发育的过程进行了观察,为柠条锦鸡儿生殖生物学提供基础资料。结果表明:(1)柠条锦鸡儿雄蕊花药4室,花药壁完全分化时,由外到内依次是表皮、药室内壁、中层和绒毡层,花药壁发育为基本型;表皮细胞1层,发育过程中始终存在;药室内壁在花药成熟时形成带状纤维层加厚;幼小花药壁的中层1～2层细胞,在花药发育成熟时退化消失;绒毡层1层细胞,腺质绒毡层,花药成熟时消失。(2)小孢子母细胞减数分裂过程中的胞质分裂为同时型,产生四面体型和左右对称型小孢子。(3)成熟花粉粒为二细胞型,扫描电镜下观察其成熟花粉粒为圆球形,外壁近光滑。(4)花粉母细胞分裂后形成的四分体小孢子中出现多核仁现象,核仁数在2～6个范围变化,推测这可能和末期Ⅱ核仁融合的不彻底有关。研究发现,柠条锦鸡儿小孢子发生和雄配子发育过程没有发现异常现象。     

光(温)敏核不育水稻花药和小孢子发生的细胞化学

利用细胞化学方法,对光（温）敏核不育水稻农垦585和W6154S的花药和小孢子发生过程的观察结果表明,在可育条件下,其花药组织和小孢子发生过程不论形态结构还是细胞化学变化都基本一致。小孢子母细胞时期的药隔薄壁组织、药壁中层及药室内壁中分布了一些多糖颗粒,但到进入减数分裂时多糖颗粒基本消失。绒毡层在解体前一直富含细胞质,从染色反应看,它表现为小孢子母细胞时期的蛋白质向减数分裂开始后的多糖物质的转变过程。在不育条件下,农垦585在小孢子母细胞时期就出现异常,其败有时间比W6154S要稍早一些。两者最后都表现为典败,但W6154S的花药壁解体较为彻底,只剩下干皱的表皮和药室内壁,而农垦585的花药壁还有多层细胞结构。     

毛钩藤的小孢子发生和雄配子体发育

在光学显微镜和透射电镜下观察了毛钩藤(Uncaria hirsuta Havil.)的小孢子发生和雄配子体发育过程.结果表明,毛钩藤花两性,具5枚雄蕊,花药4室,花药壁由表皮、药室内壁、中层和绒毡层组成,花药开裂时,药室内壁高度纤维化带状加厚.花药壁的发育方式属于双子叶型,小孢子母细胞减数分裂的胞质分裂为同时型.小孢子在四分体时期开始沉积花粉外壁,小孢子大液泡化时期开始沉积花粉内壁.成熟花粉为2-细胞型.毛钩藤的花粉发育特征和茜草科植物基本一致.毛钩藤绒毡层属于分泌型,双重起源,分别起源于次生周缘层和药隔细胞.小孢子发育早期绒毡层开始降解并分泌形成大量乌氏体,花药开裂时绒毡层完全消失,剩下少量乌氏体.小孢子早期内壁加厚突出形成,小孢子细胞核分裂以后内壁加厚开始脱落,花药开裂时,只剩下少量的内壁加厚突出.初步推测,内壁加厚突出与乌氏体共同作用为雄配子体的发育提供营养物质.     

长花柱型滇丁香小孢子发生及雄配子体发育

利用常规石蜡切片法和细胞学压片法,对异型花柱植物滇丁香的长花柱型植株的小孢子发生、雄配子体发育及花粉萌发进行观察。结果表明:(1)长花柱型滇丁香具5枚花药,花药4室。(2)花药壁由1层表皮、1层花药内壁、2层中层和1~3层绒毡层组成;花药壁发育方式为基本型,绒毡层类型为腺质绒毡层。(3)小孢子母细胞减数分裂的胞质分裂为同时型,四分体排列方式为四面体型,偶有左右对称型;不同药室间小孢子母细胞减数分裂不同步。(4)成熟花粉粒为二细胞型。(5)小孢子发生和雄配子体发育过程正常,表明长花柱型滇丁香属于发育正常的两性花。(6)授粉4h后,长花柱型滇丁香的花粉在长、短两种花柱柱头上的萌发率分别达(91.8±1.6)%和(93.2±1.1)%,且两者间无显著性差异(t=1.585,df=8,p=0.152),表明长花柱型滇丁香的成熟花粉粒在长、短两种花柱柱头上的萌发均正常。     

凤仙花花药发育特征

凤仙花花药发育比较特殊: 在造孢细胞时期,花药横切面中央是体积较大、细胞内含物较多的细胞团、包括造孢细胞和绒毡层细胞。花药药壁细胞的细胞质较稀少,与中部细胞界限明晰。花粉母细胞时期的花药药壁由约6层细胞组成,但细胞的界限不明显;绒毡层细胞显示变形流入药室中。到四分体时期,绒毡层细胞进一步退化。开花时,成熟花药的药壁细胞由一层表皮细胞、两层药室内壁细胞和一层中层细胞组成。对凤仙花花药绒毡层的特殊性质进行了讨论。     

木兰属几种药用植物花粉粒形态扫描电镜观察

用扫描电镜方法观察木兰属（Ｍａｇｎｏｌｉａ）几种药用植物的花粉粒及花药,其共同形态特征是：花粉粒近球形或长球形,具单沟或不具沟;外壁光滑或较粗糙。花药表皮细胞纺锤形或柱形,排列紧密,具条状纹饰。     

小蓬草的胚胎学研究

对小蓬草（Conyzacanadensis）大小孢子发生、雌雄配子体形成、受精、胚及胚乳发育过程进行了研究,主要结果如下：花药四室,药壁由表皮、药室内壁、中层和绒毡层组成。表皮退化;药室内壁宿存,细胞柱状伸长,纤维状加厚;中层细胞退化较早,在小孢子母细胞减数分裂开始时仅存残迹;绒毡层于小孢子母细胞减数第一次分裂前期开始原位变形退化,属于腺质型绒毡层;小孢子母细胞减数分裂为同时型,四分体的排列方式主要为四面体形和左右对称形;成熟花粉粒多为3-细胞花粉粒,偶见2-细胞花粉粒。子房下位,2心皮,1室,单胚珠,基生胎座;单珠被,薄珠心,倒生胚珠,具发达的珠被绒毡层。珠心表皮下分化出大孢子孢原细胞,孢原细胞直接发育为大孢子母细胞,大孢子母细胞减数分裂形成4个大孢子直线形排列,仅合点端的大孢子发育成功能大孢子母细胞,胚囊发育为蓼型。两个极核在受精前融合为次生核,珠孔受精。胚乳发育属于核型,胚胎发育为紫菀型;具胚乳吸器。     

长梗苦草雄花结构的环境扫描电镜观察

用环境扫描电子显微镜对沉水植物长梗苦草(Vallisneria longipedunculata)的雄花结构进行了观察研究。结果显示,长梗苦草雄花具3枚花被,2枚雄蕊是由3枚雄蕊中的1枚退化而来的,退化雄蕊清晰可见;花药4室,发育过程中通过药室顶端开裂,以及花药室基部的细胞收缩,将花粉粒都推到花药室的裂口处进行发育,成熟花粉粒直接外露;长梗苦草的花粉粒直径约50μm,壁薄,表面几乎没有纹饰,未发现萌发孔或萌发沟,这些是对特殊生境和传粉方式的适应。     

Features related to anther opening in Solanum species (Solanaceae)

The mode of anther opening and the morphological and histological variability of the stomium are described in 30 Solanum species. Poricidal, poricidal‐longitudinally dehiscing and longitudinally dehiscing anthers are observed. In the three types, the stomium may be diverse with regard to shape and histological characteristics before opening, but is always composed of small epidermal cells as the sole anther wall layer; the stomial cells may be differentiated only in part of the anther length. Particular crescent‐shaped structures in the epidermis, called ‘ridges’, are observed to line the stomium in most species. These ridges may be related to the stomium opening, working together with the cells with thickened walls of the anther. Cells with thickened walls are developed in the endothecium, middle layers and/or connective tissue at the apical end of the anther, surrounding the pore; only in the longitudinally dehiscing anthers of S. nitidum does an endothecium with thickened cell walls develop along its entire length. At least two histological features (the differentiation of small stomial epidermal cells as a unique layer, and the distribution of cells with thickened walls) seem to constrain the form of the open stomium. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 344–354.     

Secretory tapetum of Brassica oleracea L.: polarity and ultrastructural features

Summary The ultrastructure of the secretory, binucleate tapetum of Brassica oleracea in the micro spore mother cell (MMC) stage through to the mature pollen stage is reported. The tapetal cells differentiate as highly specialized cells whose development is involved in lipid accumulation in their final stage. They start breaking down just before anther dehiscence. Nuclei with dispersed chromatin, large nucleoli and many ribosomes in the cytoplasm characterize the tapetal cells. The wall-bearing tapetum phase ends at the tetrade stage. The dissolution of tapetal walls begins from the inner tangential wall oriented towards the loculus and proceeds gradually along the radial walls to the outer tangential one. The plasmodesmata transversing the radial walls between tapetal cells persist until the mature microspore, long after loss of the inner tangential wall. After wall dissolution, the tapetal protoplasts retain their integrity and position within the anther locule. The tapetal cell membrane is in direct contact with the exine of the microspores/pollen grains and forms tubular evaginations that increase its surface area and appear to be involved in the translocation of solutes from the tapetal cells to the microspores/ pollen grains. The tapetal cells exhibit a polarity expressed by spatial differentiation in the radial direction.     

Anther structure and pollen development in Melicoccus lepidopetalus (Sapindaceae): An evolutionary approach to dioecy in the family

Anther and pollen development in staminate and pistillate flowers of dioecious Melicoccus lepidopetalus (Sapindaceae) were examined by light and electron microscopy. Young anthers are similar in both types of flowers; they consist of epidermis, endothecium, two to four middle layers and a secretory tapetum. The microspore tetrads are tetrahedral. The mature anther in staminate flowers presents compressed epidermal cells and endothecium cells with fibrillar thickenings. A single locule is formed in the theca by dissolution of the septum and pollen grains are shed at two-celled stage. The mature anthers of pistillate flowers differ anatomically from those of staminate flowers. The epidermis is not compressed, the endothecium does not develop fibrillar thickenings, middle layers and tapetum are generally persisting, and the stomium is nonfunctional. Microspore degeneration begins after meiosis of microspore mother cells. At anthesis, uninucleate microspores and pollen grains with vegetative and generative nuclei with no cytokinesis are observed. Some pollen walls display an abnormal exine deposition, whereas others show a well formed exine, although both are devoid of intine. These results suggest that in the evolution towards unisexuality, the developmental differences of anther wall tissues and pollen grains between pistillate and staminate flowers might become more pronounced in a derived condition, such as dioecy.     

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.     

The Mechanics of the Grass Flower: Anther Dehiscence and Pollen Shedding in Maize

In this paper on the flower mechanics of the grasses, the openingmechanism of the maize anther is studied. Both the septum betweeneach two locules and the stomium of these porate-dehiscing anthersappear to be opened due to lysis of the middle lamellae of theircells. Additional mechanical force of the expanding pollen mightbe necessary to completely dissociate the parenchyma cells ofthe septum. A number of hours before anthesis the anther isstructurally able to dehisce. At anthesis the dehydrating endotheciumcells bend the locule walls bordering the pore in outward direction.Presumably evaporation is not the only cause for this dehydration. Poaceae; Zea mays ; flower; anther; dehiscence; endothecium; pollen     

Mechanism of Anther Dehiscence in Rice (Oryza sativa L.)

This paper presents a new explanation of the mechanism of antherdehiscence in rice during the period from floret opening topollen dispersal. The theca dehisced on the stomium in the apicalpart and the anther wall in the basal part of the large locule.Comparison of the anther dehiscence process under various airhumidity conditions showed that the process, until the splittingat the apical and basal parts, was a moisture-requiring processwhereas the widening of the splits in both parts was a desiccatoryprocess. Observation of the anther transverse section, revealedthe marked development of the U-shaped thick cell wall in theendothecium adjacent to these two splits. From these observations,the anther dehiscence mechanism may be explained as follows.At the time of anthesis, pollen grains swell rapidly in responseto the floret opening and cause the theca to bulge, rupturingthe septum. The pollen pressure combined with the inward bendingof the locule walls adjacent to the stomium causes splittingof the stomium in the apical part of the theca. At the sametime, the septum rupture extends to the bottom of the largelocule supported by the pollen pressure. After these processes,the locule walls adjacent to both splits straighten probablydue to their water loss. This straightening widens the splitsand the swollen pollen grains overflow from the widened splits.Copyright1999 Annals of Botany Company Anther dehiscence, Oryza sativa L., pollen grain swelling, rice, septum, stomium, theca.     

Pollen and Tapetum Development in Male Fertile Rosmarinus Officinalis L. (Lamiaceae)

The development of microspores/pollen grains and tapetum was studied in fertile Rosmarinus officinalis L. (Lamiaceae). Most parts of the cell walls of the secretory anther tapetum undergo modifications before and during meiosis: the inner tangential and radial cell walls, and often also the outer tangential and radial wall, acquire a fibrous appearance; these walls become later transformed into a thin poly-saccharidic film, which is finally dissolved after microspore mitosis. Electron opaque granules found within the fibrous/lamellated tapetal walls consist of sporopollenin-like material, but cannot be interpreted as Ubisch bodies. The middle lamella and the primary wall of the outer tangential and radial tapetal walls remain unmodified, but get covered by an electron opaque, sporopollenin-like layer. Pollenkitt is formed only by lipid droplets from the ground plasma and/or ER profiles, the plastids do not form pollenkitt precursor lipids. Tapetum maturation (“degeneration”) does not take place before late vacuolate stage.

The apertures are determined during meiosis by vesicles or membrane stacks on the surface of the plasma membrane. The procolumellae are conical, but at maturity the columellae are more cylindrical in shape. The columellar bases often fuse, but a genuine foot layer is lacking. The formation of the endexine starts with sporopollenin-accumulating white lines adjacent to the columellar bases. Later, the endexine grows more irregularly by the accumulation of sporopollenin globules. In mature pollen the intine is clearly bilayered.

Generative cells (GCs) and sperm cells contain a comparatively large amount of cytoplasm, and organelles like mitochondria, dictyosomes, ER, and multi-vesicular bodies, but no plastids; GCs and sperms are separated from the vegetative cell only by two plasma membranes.     

Ultrastructure of microsporogenesis and microgametogenesis inArabidopsis thaliana (L.) Heynh. ecotype Wassilewskija (Brassicaceae)

Summary The process of microsporogenesis and microgametogenesis was studied at the ultrastructural level in wild-typeArabidopsis thaliana ecotype Wassilewskija to provide a basis for comparison with nuclear male-sterile mutants of the same ecotype. From the earliest stage studied to mature pollen just prior to anther dehiscence, microsporocyte/microspore/pollen development follows the general pattern seen in most angiosperms. The tapetum is of the secretory type with loss of the tapetal cell walls beginning at about the time of microsporocyte meiosis. Wall loss exhibits polarity with the tapetal protoplasts becoming located at a distance from the inner tangential walls first, followed by an increase in distance from the radial walls beginning at the interior edge and progressing outward. The inner tangential and radial tapetal walls are completely degenerated by the microspore tetrad stage. Unlike other members of the Brassicaceae that have been studied, the tapetal cells ofA. thaliana Wassilewskija also lose their outer tangential walls, and secretion occurs from all sides of the cells. Exine wall precursors are secreted from the tapetal cells in a process that appears to involve dilation of individual endoplasmic reticulum cisternae that fuse with the tapetal cell membrane and release their contents into the locule. Following completion of the exine, the tapetal cell plastids develop membranebound inclusions with osmiophilic and electron-transparent regions. The plastids undergo ultrastructural changes that suggest breakdown of the inclusion membranes followed by release of their contents into the locule prior to the complete degeneration of the tapetal cells.     

Electron-translucent angular areas in developing tapetum cell walls and pollen grains ofTilia platyphyllos

Summary InTilia platyphyllos, the anther tapetal cell walls undergo significant modifications from the tetrad stage onwards. During the tetrad stage the inner tangential and radial parts of the tapetal walls begin to dissolve, while the distal parts swell. After the tetrad stage, the distal and outer radial tapetal cell walls become covered by a thick, irregular, highly electron-dense, polysaccharide layer. Striking features of the maturing tapetal walls (microspore stage and later) are electron-translucent, structureless, unstainable angular areas of variable dimensions. Similar electron-translucent areas occur in the exine arcades and apertures, but also isolated in the locular fluid ofT. platyphyllos. Electron-translucent areas, that are also found in the exine arcades and tapetal cells of other angiosperms, can be interpreted as the products of poorly understood metabolic processes.     

Cytochemical study of developing anthers of Amomum villosum Lour.

We analyzed anther development in Amomum villosum Lour. (Zingiberaceae) using the periodic acid-Schiff's technique and Sudan black staining to test for the presence of starch and lipids, respectively. Our analyses showed that microspore mother cells of A. villosum lack typical callose walls, and numerous lipid granules appear in the cells early in development. Some starch granules are present in anther wall cells, but not in tapetal cells. After meiosis, numerous lipid granules remain unchanged in the microspores. During microspore development, some small starch granules first appear in the central cell region, and then the starch granules increase in size. After microspore division, the bicellular pollen grains become filled with starch and lipids, and remain in this state until the pollen grains reach maturity. At anthesis, the anther wall of A. villosum consists of several layers of endothecium cells with an evidently thickened radial wall, and some layers of parenchyma cells containing numerous starch granules.