含笑花药发育的超微结构研究

对含笑花药发育中的超微结构变化进行观察,结果显示:(1)花粉发育中有三次液泡变化过程——第一次是小孢子母细胞在形成时内部出现了液泡,这可能与胼胝质壁的形成有关;第二次是在小孢子母细胞减数分裂之前,细胞内壁纤维素降解区域形成液泡,它的功能可能是消化原有的纤维素细胞壁;第三次是在小孢子液泡化时期,形成的大液泡将细胞核挤到边缘,产生极性。(2)含笑花粉在小孢子早期形成花粉外壁外层,花粉外壁内层在小孢子晚期形成,而花粉内壁是在二胞花粉早期形成;花粉成熟时,表面上沉积了绒毡层细胞的降解物而形成了花粉覆盖物。研究认为,含笑花粉原外壁的形成可能与母细胞胼胝质壁有关,而由绒毡层细胞提供的孢粉素物质按一定结构建成了花粉覆盖物。     

水稻雄性不育系珍汕97A小孢子发育过程中的微管骨架

水稻（Oryza sativaL.)雄性不育系珍汕97A,保持系珍汕97B和恢复系测64三系小孢子发生过程的研究表明;恢复系测64小孢子母细胞细胞质浓,有明显的微管荧光围绕着细胞核。小孢子母细胞经两次减数分裂形成四分体。四分体和小孢子的微管从细胞核表面向胞质周缘延伸,形成放射性排列格局,花粉发育正常。细胞质中有少量点状微管荧光,保持系珍汕97B小孢子发生过程的细胞形态和微管结构与恢复系测64相似。但细胞质中的点状微管荧光多一些。雄性不育系珍汕97A小孢子发生早期,小孢子母细胞内出现液泡,核中染色质凝集,微管荧光很弱,没有清晰的微管丝结构。细胞质中有许多点状微管荧光等不正常现象。小孢子母细胞经过减数分裂形成的四分体也没有清晰的丝状微管结构。随后,所有的小孢子迅速败育,雄性不育系珍汕97A在小孢子母细胞发生的很早时期,微管结构就明显不正常。     

The Microsporogenesis and Megasporogenesis of Soybean

This article deals with the morphological aspects of the process of megasporogenesis and microsporogenesis in soybean. The tempos of microsporogenesis in different anthers of the same flowers were compared, and it has been found that at the leptone- ma, zygonema, pachynema and diplonema of the first meiotic division there appeared a certain degree of synchrony, while at the uninuclear stage of the microspore a perfect synchrony was observed. The development of different pollen mother cells within the same anther was in most cases highly synchronized. The anther in which the PMCs were found to be in the'near stages of the meiotic divisions accounts for 7% only. The megasporocyte develops later than the mierosporoeyte. It enters into the leptotene stage or diplotene stage of the first meiotic division while the mierosporocyte has already finished the process of the meiotic division. Explantation of plates 1. A section of a partieal mierosporangium, mierospore mother cells and the cells of the anther wall. × 600 2. Mierospore mother cells in zygotene stage (bouquet stage). × 600 3. Pa- chytene stage of first meiotic division. ×530 4. Diakinesis of meiosis Ⅰ, the tapetal cells begin- ning to degenerate. ×900 5. Metaphase Ⅰ. ×630 6. Anaphase Ⅰ. ×630 7. Anaphase Ⅰ. ×370 8 Interphase, two-nucleated dyad condition with no intervening cell walls formed. ×630 9. Me- taphase Ⅱ. ×630 10. Beginning of telophase Ⅱ×370 11, Telophase Ⅱ, four microspore nuclei contained within the original microspore mother cell wall. ×630 12. Uninuclear microspore, ×630     

凹叶厚朴大、小孢子发生和雌、雄配子体发育的研究

凹叶厚朴花药四囊型,腺质绒毡层有1-2层细胞,小孢子形成时胞质分裂方式为修饰性同时型．小孢子四分体排列方式为左右对称型,成熟花粉粒为二细胞型。四分体和小孢子在发生时有不规则变形。子房单心皮。心皮腹面壁上着生2个胚珠,胚珠倒生型,厚珠心,双珠被;抱原细胞一个,并且自表皮下第2层细胞处分化。胚囊发育为单孢蓼型。凹叶厚朴的胚胎学特征与木兰科其它植物的胚胎学特征基本相同,属于较原始的被子植物胚胎类型。在凹叶厚朴大、小孢子发生和雌、雄配子体发育过程中存在部分败育现象。本文初步探讨了凹叶厚朴濒危的生殖生物学原因。     

莴苣花药发育过程中钙的分布特征

减数分裂前,莴苣花药中的钙颗粒很少。减数分裂后,花药绒毡层细胞中的钙颗粒明显增加。同时在花药药室基质中也出现许多细小的钙颗粒。刚从四分体中释放出的小孢子内钙颗粒很少。伴随着花粉外壁物质在小孢子表面的沉积,钙颗粒开始积累在花粉壁部位。随后。小孢子中开始出现钙颗粒。当小孢子开始形成液泡后,钙颗粒向其中聚集,伴随着小液泡融合成大液泡。体积较大的钙颗粒主要集中在液泡中,而细胞质基质中的钙颗粒很少。随着二胞花粉中的大液泡消失,花粉细胞质中的钙颗粒变得很少。在以后的发育中,只有花粉壁中积累较多的钙颗粒。在莴苣花药发育过程中,钙与绒毡层细胞的退化和小孢子液泡形成以及二胞花粉中大液泡的消失有关。而花粉外壁表面积累丰富的钙与以后花粉的萌发有关。     

金线莲花药发育中的钙离子分布特征

该研究以金线莲不同发育时期的花药为材料,采用电子显微镜观察花粉块中的钙离子分布,以揭示钙离子在金线莲花药发育中的相关生理功能。结果发现:(1)在造孢细胞时期,较多的钙沉淀颗粒出现在花药表皮和药室内壁细胞的液泡中,暗示钙离子与植物细胞的液泡发生和形成有关。(2)在减数分裂前期,小孢子母细胞核中聚集了较多的钙沉淀颗粒,当小孢子母细胞分裂时,在二组染色体之间有大量的钙沉淀颗粒,显示钙离子与细胞分裂有关。(3)在合成淀粉的质体表面覆盖了较多的钙沉淀颗粒,显示钙离子与质体中的糖代谢有关。研究表明,开花时在花粉块表面的花粉外壁上和成熟花粉中仍保持有大量的钙沉淀颗粒,为花粉萌发所需钙离子做好了储备。     

凹叶厚朴大、小孢子发生和雌、雄配子体发育的研究

凹叶厚朴花药四囊型,腺质绒毡层有1-2层细胞,小孢子形成时胞质分裂方式为修饰性同时型,小孢子四分体排列方式为左右对称型．成熟花粉粒为二细胞型。四分体和小孢子在发生时有不规则变形。子房单心皮,心皮腹面壁上着生2个胚珠,胚珠倒生型,厚珠心,双珠被;孢原细胞一个,并且自表皮下第2层细胞处分化。胚囊发育为单孢蓼型。凹叶厚朴的胚胎学特征与木兰科其它植物的胚胎学特征基本相同,属于较原始的被子植物胚胎类型。在凹叶厚朴大、小孢子发生和雌、雄配子体发育过程中存在部分败育现象。本文初步探讨了凹叶厚朴濒危的生殖生物学原因。     

萝卜CMS不育系与保持系小孢子发生的细胞学研究

研究了萝卜胞质雄性不育系A2、A4及其相应保持系B2、B4的小孢子发生与花药壁发育的细胞学特征.结果表明,不育系A2的绒毡层细胞在四分体时期出现异常,小液泡增多,至单核期汇合形成大液泡,绒毡层细胞异常膨大;小孢子外壁染色浅,细胞壁受到破坏,最后与绒毡层一同降解.不育系A4在减数分裂期即表现出异常,绒毡层异常肥大;花药发育后期,小孢子外壁亦染色较浅;绒毡层细胞融合形成细胞团块侵入药室挤压小孢子,两者一同降解.     

凤仙花花药发育中多糖和脂滴组织化学研究

以不同发育时期的凤仙花花药为实验材料,采用组织化学方法,对花药发育中的结构变化及多糖和脂滴物质分布进行观察。结果表明:(1)凤仙花的花药壁由6层细胞组成,包括1层表皮细胞,2层药室内壁细胞,2层中层细胞和1层绒毡层细胞。其中绒毡层细胞的形态不明显,很难与造孢细胞区分,且在小孢子母细胞时期退化。(2)在小孢子母细胞中出现了一些淀粉粒,但减数分裂后,早期小孢子中的淀粉粒消失,又出现了一些小的脂滴;随着花粉的发育,小孢子形成大液泡,晚期小孢子中的脂滴也消失;小孢子分裂形成二胞花粉后,营养细胞中的大液泡降解、消失,二胞花粉中又开始积累淀粉;接近开花时,成熟花粉中充满细胞质,其中包含了较多的淀粉粒和脂滴。(3)在凤仙花的花药发育中,绒毡层细胞很早退化,为小孢子母细胞和四分体小孢子提供了营养物质;其后的中层细胞退化则为后期花粉发育提供了营养物质。     

杉木小孢子核内双膜包绕的内含体(简报)

杉木小孢子的发育已进行了系统的电子显微镜研究。在研究中我们发现小孢子发育到一定阶段,细胞核内出现一种双膜包绕的内含体。这种有膜内含体无论在结构上,发生的普遍性和阶段性上都与已有的报道不同,是首次发现。研究材料为杉木(Cunninghamia lanceola-     

莴苣花药发育过程中钙的分布特征

减数分裂前,莴苣花药中的钙颗粒很少。减数分裂后,花药绒毡层细胞中的钙颗粒明显增加, 同时在花药药室基质中也出现许多细小的钙颗粒。刚从四分体中释放出的小孢子内钙颗粒很少,伴随着花粉外壁物质在小孢子表面的沉积,钙颗粒开始积累在花粉壁部位。随后,小孢子中开始出现钙颗粒。当小孢子开始形成液泡后,钙颗粒向其中聚集,伴随着小液泡融合成大液泡,体积较大的钙颗粒主要集中在液泡中,而细胞质基质中的钙颗粒很少。随着二胞花粉中的大液泡消失,花粉细胞质中的钙颗粒变得很少。在以后的发育中,只有花粉壁中积累较多的钙颗粒。在莴苣花药发育过程中,钙与绒毡层细胞的退化和小孢子液泡形成以及二胞花粉中大波泡的消失有关。而花粉外壁表面积累丰富的钙与以后花粉的萌发有关。     

A COMPARATIVE LIGHT- AND ELECTRON-MICROSCOPIC STUDY OF MICROSPOROGENESIS IN MALE STERILE (MS,) AND MALE FERTILE SOYBEANS (GLYCINE MAX (L.) MERR.)

A comparative study of microsporogenesis in fertile and in male sterile (ms₁) soybean plants (Glycine max (L.) Merr.) was conducted by using various microscopic techniques. Once the developmental pattern for fertile microsporogenesis was established, it was compared with the developmental pattern in sterile plants to determine the time of microsporogenesis breakdown. Sterility of the ms₁ mutant is caused by failure of cytokinesis after telophase II. The four nuclei resulting from meiosis become enclosed in a single-celled structure, termed a coenocytic microspore. These microspores develop a pollen-like wall and become engorged with lipid and starch reserves. Coenocytic microspores usually degenerate after engorgement. This study of fertile and sterile (ms₁) microsporogenesis has shown that nuclear and cytoplasmic events must occur at precise times for the successful development of 1n pollen grains from 2n sporogenous cells. Any disruption during this process leads to sterility.     

Structure and function of the microtubular cytoskeleton during pollen development in Gasteria verrucosa (Mill.) H. Duval

In a study of pollen development in Gasteria verrucosa, the changes in the spatial organization of microtubules were related to the processes of cell division, nuclear movement and cytomorphogenesis. Sections of polyethylene-glycol-embedded anthers of G. verrucosa were processed immunocytochemically to record the structure and succession of fluorescently labeled microtubular configurations. Using microspectrophotometric measurements the relative quantity of tubulin in microtubules per unit of cytoplasm was determined. Cell dimensions and nuclear positions were measured to relate changes in cell shape and nuclear movements to microtubular configurations. Microtubules were detected in the different cells during microsporogenesis and microgametogenesis. In microspore mother cells which are approximately isodiametric at interphase, microtubules were predominantly arranged in a criss-cross pattern. The microtubules probably function as a flexible cytoskeleton which sustains the integrity of the cytoplasm. Bundles of microtubules were observed in the microspores, in the generative cells and during nuclear division, where they functioned in establishing and maintaining cell and spindle shapes. Microtubules radiating from nuclear membranes appeared to fix the nucleus in position. In prophase of meiosis and after microspore mitosis, periods a high fluorescence intensity were distinguished indicating a variation in the quantity of microtubules.Abbreviation MT microtubule     

Ultrastructural aspects and programmed cell death in the tapetal cells of Lathyrus undulatus Boiss

Programmed cell death (PCD) in the tapetum of Lathyrus undulatus L. was analyzed based on light, fluorescence and electron microscopy to characterize its spatial and temporal occurrence. Development and processes of PCD in secretory tapetal cells of Lathyrus undulatus L. were correlated with the sporogenous cells and pollen grains. At early stages of development the tapetal cells appeared similar to pollen mother cells, structurally. Concurrent with meiosis, tapetum expanded both tangentially and radially as vacuoles increased in size. Tapetal cells most fully developed at young microspore stage. However, tapetum underwent substantial changes in cell organization including nucleus morphology monitored by DAPI. The TUNEL staining confirmed the occurrence of intra-nucleosomal DNA cleavage. In addition to nuclear degeneration which is the first hallmark of PCD other diagnostic features were observed at vacuolated microspore stage intensely; such as chromatin condensation at the periphery of the nucleus, nuclear membrane degeneration, chromatin release to the cytoplasm, vacuole collapse according to tonoplast rupture, shrinkage of the cytoplasm, the increase and enlargement of the endoplasmic reticulum cisternae and disruption of the plasma membrane. After vacuole collapse due to possible release of hydrolytic enzymes the cell components degraded. Tapetal cells completely degenerated at bicellular pollen stage.     

Microsporogenesis and tapetal development in fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.)

Summary The development of sporogenous and tapetal cells in the anthers of male-fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) plants was studied using light and transmission electron microscopy. In general, male-sterile anthers showed a much greater variability in developmental pattern than male-fertile anthers. The earliest deviation from normal anther development was observed to occur in sterile anthers at meiotic early prophase: there was a degeneration or irregular proliferation of the tapetal cells. Other early aberrant events were the occurrence of numerous small vesicles in the microspore mother cells (MMC) and a disorganized chromatin condensation. Deviations that occurred in sterile anthers at later developmental stages included: (1) less distinct inner structures in the mitochondria of both MMC and tapetal cells from middle prophase onwards. (2) dilated ER and nuclear membranes at MMC prophase, in some cases associated with the formation of protein bodies. (3) breakdown of cell walls in MMCs and tapetal cells at late meiotic prophase. (4) no massive increase in tapetal ER at the tetrad stage. (5) a general dissolution of membranes, first in the MMC, then in the tapetum. (6) abortion of microspores and the occurrence of a plasmodial tapetum in anthers reaching the microspore stage. (7) no distinct degeneration of tapetal cells after microspore formation. Thus, it seems that the factors that lead to abortive microsporogenesis are structurally expressed at widely different times during anther development. Aberrant patterns are not restricted to the tetrad stage but occur at early prophase.     

Ricerche Embriologiche su Senecio Vulgaris L. var. Thyrrenus Fiori

Abstract

Embryological researches on SENECIO VULGARIS L. var. THYRRENUS Fiori. — Male gametophyte, development of tapetal cells and female gametophyte have been studied in Senecio vulgaris L. var thyrrenus Fiori.

1) The development of male gametophyte is normal. Divisions of the microspore mother cells are of the simultaneous type. The division of the generative nucleus has never been observed till the pollen grain was in the anther.

2) The tapetal cells follow a very simple development. The nucleus of each cell divides only twice starting at the same time with the meiotic divisions of pollen mother cells but ending much earlier; subsequently, as usually happens with the Asteraceae, the ameboid involution of the tapetum begins. Endomitosis or any other process which leads to a polyploidy not due to nuclear fusion, has never been observed.

3) The female gametophyte is eight nucleate of the normal type (Polygonum). At maturity it shows only three antipodal cells whose nucleus undergoes at first, two or three divisions. Only later these new nuclei, always within the antipodal cell, may fuse in a polyvalent one.     

Tracking individual wheat microspores in vitro: identification of embryogenic microspores and body axis formation in the embryo

 The development of isolated, defined wheat microspores undergoing in vitro embryogenesis has been followed by cell tracking. Isolated wheat (Triticum aestivum L.). microspores were immobilized in Sea Plaque agarose supported by a polypropylene mesh at a low cell density and cultured in a hormone-free, maltose-containing medium in the presence of ovaries serving as a conditioning factor. Embryogenesis was followed in microspores isolated from immature anthers of freshly cut tillers or from heat- and starvation-treated, excised anthers. Three types of microspore were identified on the basis of their cytological features at the start of culture. Type-1 microspores had a big central vacuole and a nucleus close to the microspore wall, usually opposite to the germ pore. This type was identical to the late microspore stage in anthers developing in vivo. Microspores with a fragmented vacuole and a peripheral cytoplasmic pocket containing the nucleus were defined as type 2. In type-3 microspores the nucleus was positioned in a cytoplasmic pocket in the centre of the microspore. Tracking revealed that, irrespective of origin, type-1 microspores first developed into type 2 and then into type-3 microspores. After a few more days, type-3 microspores absorbed their vacuoles and differentiated into cytoplasm-rich and starch-accumulating cells, which then divided to form multicellular structures. Apparently the three types of microspore represent stages in a continuous process and not, as previously assumed, distinct classes of responding and non-responding microspores. The first cell division of the embryogenic microspores was always symmetric. Cell tracking also revealed that the original microspore wall opened opposite to a region in the multicellular microspore which consisted of cells containing starch grains while the remaining cells were starch grain-free. The starch-containing cells were located close to the germ pore of the microspore. In more advanced embryos the broken microspore wall was detected at the root pole of the embryo. Received: 27 December 1999 / Accepted: 11 May 2000     

短命植物条叶车前小孢子发生与雄配子体发育研究

条叶车前小孢子发生与雄配子体形成过程如下：花药具４个花粉囊;药壁由表皮、药室内壁、中层、绒毡层等４层细胞组成,发育方式为双子叶型,绒毡层细胞为腺质;小孢子母细胞减数分裂过程中胞质分裂为同时型;小孢子四分体多为四面体型,少数为十字交叉型或两侧对称型;成熟花粉粒为３－细胞,两个精子由原生质丝与营养核联系起来,因此可能存在着“雄性生殖单位”。     

Ontogenesis of Tannin Coenocytes in Sambucus racemosa L. II. Mother Tannin Cells

Tannin coenocytes develop from mononucleate tannin mother cells.The process occurs within the whole of the first (youngest)internode and its development can be divided into three stages.In stage I the MTC is isodiametric and similar to the surroundingcells of the flank meristem, being present in the ninth celllayer from the apex surface. The nucleus becomes lanceolateand elongates, and large cytoplasmic vacuoles appear. A twofoldelongation of both the cell and nucleus continues in the secondstage, the cell-nucleus ratio indicating that it is due to theenlarged vacuole, which pushes a thin layer of cytoplasm closeto the cell wall. In this layer of cytoplasm dilated ER cisternaoccur together with small and large vacuoles, a fusion of thevacuoles increasing their volume. Such cells are diploid inspite of larger nuclear volume and rough structure of its chromatin. Sambucus racemosa L., tannin cells, development, ontogenesis     

The mechanics of budding and copulation in saccharomyces

The yeast cell contains a nucleus whose rigid centrosome carries a band of Feulgen-positive chromatin (centrochromatin) on its surface. The first step in budding is the formation of the bud by an extension of the centrosome over which the cell wall persists. Next the nuclear vacuole extends a process into the bud which contains the chromosomes. Finally the centrochromatin divides directly and the cells separate; a plug either of centrosome or cytoplasm sealing the bud pore. The cytoplasm, the centrosome, the centrochromatin and the nuclear wall are autonomous non genic organelles which never originate de novo.Copulation is the reverse of budding. The centrosomes fuse first; the cytoplasms mix; the nuclear vacuoles fuse by processes which travel along the fused centrosomes; and finally the centrochromatins fuse to form a single band.Figures 1–12. Drawings of budding yeast cells fixed in Schaudinn's fluid and stained with iron alum hemotoxylin, mounted in balsam. The cell wall is not visible due to the clearing action of the balsam. Except for Figure 5, the chromosomes and the nucleolus in the nuclear vacuole have been completely destained. The bud scar described by Barton is shown clearly at the end of the cell distal from the centrosome. The nuclear vacuole is usually forced into the extrusion formed by the bud scar. Since the cell wall is not visible, the plug of material connecting bud and mother cell as shown in Figure 12, fits into the cell wall and probably corresponds to the plug in the bud scar described by Barton. The details of the budding process are described in the text.Figures 13–18. Copulating yeast cells stained with Barrett's hemotoxylin and aceto-orcein and mounted in the stain. Chromosomes are visible in the nuclear vacuoles. The centrosome is usually visible and often appears to have a core which stains differentially. Except in Figure 16, the centrochromatin is visible as darkly stained material; in some cases surrounded by a clear zone. The “thick waisted” form of the cells identifies them as derived from recent copulations and distinguishes them from budding cells. The process of copulation is discussed in the text.