葡萄果实发育过程中果肉细胞超微结构的观察

用透射电镜观察了“巨峰”葡萄(Vitis vinifera×V.labrusca)果实3个发育时期中果肉细胞超微结构的变化。果实第一次快速生长期的果肉细胞超微结构表现出物质和能量代谢旺盛的特点。缓慢生长期的果实虽外部形态平静少变,但果肉细胞超微结构表现出深刻的变化:细胞核形状特化为裂瓣状是最显著的特点;线粒体数目丰富;粗面内质网槽库膨大形成的囊泡富集,出现向液泡汇融和向质膜靠近的现象;质膜内陷;液泡膜完整。另外,原生质也出现一些降解的现象。但总体结构特点表明果肉细胞在此期处于十分活跃的物质周转代谢和信息交换过程中。果实第二次快速生长期果肉细胞超微结构表现出衰老降解的特点,但线粒体结构依然完整,数量仍然丰富,原生质膜也保持了很好的完整性,这似乎与维持第二次快速生长或成熟有关。     

Ultrastructure of post-fertilization development in the red alga Nienburgia andersoniana (Delesseriaceae, Ceramiales, Rhodophyta)

The ultrastructure of post-fertilization development in Nienburgia andersoniana (J. Ag.) Kyl. is described. Above the auxiliary cell there is a group of four sterile cells. The presence of abundant storage products (starch granules, lipid bodies and protein crystals) in these cells indicates that the sterile cells function as nutrient suppliers to the young auxiliary and gonimoblast cells of the carposporophyte during its early steps of development. Following fertilization and transfer of the diploid nucleus to the auxiliary cell, the trichogyne disappears and large multinucleate gonimoblast initials are produced. These subsequently produce generative gonimoblast cells which cleave successively to form young carpospores. Those of the gonimoblast cells which will not differentiate into carpospores are transformed into cells producing mucilage. Both kinds of gonimoblast cells contain plastids, starch granules, cytoplasmic concentric membrane bodies and small vesicles. Dark-staining spherical masses occurring in the cytoplasm of the auxiliary and gonimoblast cells may represent degenerating haploid nuclei. Septal plugs interconnecting the auxiliary cell and gonimoblast cells increase considerably in size during carposporophyte development. The fusion cell at the late stage of carposporophyte development appears degenerative. Young carpospores have plastids and mitochondria, and concentric membrane bodies that will form mucilage sacs. Medium-aged carpospores have fully developed plastids, starch granules and fibrous vacuoles. Mature carpospores possess, in addition, cored vesicles. The inner pericarp cells contribute large amounts of mucilage to the cytostocarpic cavity and eventually are consumed. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 289–299.     

ULTRASTRUCTURE OF THE SECONDARY PHLOEM OF TILIA AMERICANA

Summer and winter (July and January) samples of secondary phloem of Tilia americana were studied with the electron microscope. Parenchyma cells contain: nuclei, endoplasmic reticulum, ribosomes, plastids, mitochondria and occasional dictyosomes. Well-defined tonoplasts separate vacuoles from cytoplasmic ground substance. Vacuoles often contain tannins. Lipid droplets are common in cytoplasm. Endoplasmic reticulum–connected plasmodesmata are aggregated in primary pit fields. Companion cells differ from parenchyma cells in having numerous sieve-element connections, possibly slime, and in lacking plastids. Mature, enucleate sieve elements possess 1–4 extruded nucleoli. Numerous vesicles occupy a mostly parietal position in association with plasmalemma. The mature sieve element lacks endoplasmic reticulum, organelles (except for few mitochondria) and tonoplast. In OsO_4– and glutaraldehyde-fixed elements, slime has a fine, fibrillar appearance. Normally, these fine fibrils are organized into coarser ones which form strands that traverse the cell and the plasmalemma-lined pores of sieve plates and lateral sieve areas.     

Ultrastructure of the early stages of carposporophyte development in the red algaChondria tenuissima (Rhodomelaceae,Ceramiales)

The ultrastructure of the early stages of carposporophyte development in the marine red algaChondria tenuissima has been studied. The diploid carposporophyte grows on the gametophyte. Apical gonimoblast cells develop into diploid carpospores. The basal gonimoblast cells cease to divide and undergo considerable cytoplasmic changes before they become incorporated into the expanding fusion cell. Nucleus and plastids degenerate gradually, while mitochondria remain intact. The smooth endoplasmic reticulum becomes prominent, it seems to produce small vesicles with electron dense contents. Simultaneously, numerous mucilage sacs are formed, presumably from dilating ER cisternae. The contents of the mucilage sacs are secreted by exocytosis. The pit connections between gonimoblast cells flare out. They remain as isolated bodies without connection to a wall after fusion. Secondary pit connections occur between vegetative gametophyte cells and sterile carposporophyte cells. There are three different morphological types of pit connections.     

ULTRASTRUCTURAL OBSERVATIONS ON THE TRICHOBLASTS OF EQUISETUM

Equisetum trichoblasts are densely cytoplasmic, containing numerous starch-containing plastids, mitochondria, and concentrations of rough endoplasmic reticulum with attached polysomes. Numerous vesicles of Golgi origin are present, containing a lightly staining fibrillar material; these vesicles appear to fuse with the wall. The outer tangential and radial walls become thickened while the inner tangential wall remains thin with numerous plasmodesmata. As the trichoblasts develop into root hairs, vacuolation occurs, resulting in large vacuoles. This may represent autolytic vacuolation. The cytoplasm of the root hairs is similar to that of the trichoblasts.     

ULTRASTRUCTURE OF TETRASPOROGENESIS IN THE PARASITIC RED ALGA LEVRINGIELLA GARDNERI (SETCHELL) KYLIN12

Ultrastructural studies on tetraspore formation in Levringiella gardneri revealed that 3 stages may be recognized during their formation. The youngest stage consists of a uninucleate tetraspore mother cell with synaptonemal complexes present during early prophase of meiosis I. Mitochondria are aggregated around the nucleus, dictyosome activity is low, and chloroplasts occur in the peripheral cytoplasm. A 4-nucleate tetraspore mother cell is formed prior to tetrahedral cell cleavage, and an increase in the number of chloroplasts and mitochondria occurs. Small straight-profiled dictyosomes secrete vesicles into larger fibrous vesicles or contribute material to the developing tetraspore wall. During the second stage of tetraspore formation, striated vesicles form within endoplasmic reticulum, semicircular profiled dictyosomes secrete vesicles for fibrous vesicles or wall material, and starch formation increases. The final stage is characterized by the disappearance of striated vesicles, presence of straight, large dictyosomes which secrete cored vesicles, and an abundance of starch grains. Cleavage is usually complete at this stage and the tetraspore wall consists of a narrow outer layer of fibrillar material and an inner, electron transparent layer. These spores are surrounded by a tetrasporangial wall which was the original wall surrounding the tetraspore mother cell.     

ULTRASTRUCTURE OF CARPOSPOROPHYTE DEVELOPMENT IN THE RED ALGA GLOIOSIPHONIA VERTICILLARIS (CRYPTONEMIALES,GLOIOSIPHONIACEAE)

The ultrastructure of carposporophyte development is described for the red alga Gloiosiphonia verticillaris Farl. The auxiliary cell produces gonimoblast initials, which divide to produce two types of gonimoblast cells—the nondividing vacuolate cells and terminal generative gonimoblast cells. The generative gonimoblast cells form clusters of carpospore initials, which eventually differentiate into carpospores. After gonimoblast filaments are formed, the auxiliary cell undergoes autolysis, causing degeneration of septal plugs between the auxiliary cell and adjacent cells, thus forming a fusion cell. Since this cell lacks starch and appears degenerate throughout carposporophyte development, a nutritive function cannot be ascribed to the fusion cell. Carpospore differentiation is simple and proceeds through three developmental stages. Young carpospores structurally resemble gonimoblast cells, because they contain undeveloped plastids, large quantities of floridean starch, and are surrounded by extensive mucilage instead of a distinct wall. In addition, dictyosomes form and begin to produce vesicles with fibrous contents representing carpospore wall material. During the intermediate stage, dictyosomes continue to produce vesicles that contribute additional carpospore wall material, thereby compressing the mucilage and creating a darker-staining layer outside the carpospore wall. Plastids form internal thylakoids by invaginations of the inner membrane of the peripheral thylakoid. The endoplasmic reticulum forms large granular vacuoles that appear to be degraded during subsequent stages of development. Mature carpospores form cored vesicles. They also contain mature chloroplasts, large amounts of floridean starch, and occasionally granular vacuoles. During this stage, interconnecting carpospore-carpospore and carpospore-gonimoblast cell septal plugs begin to undergo degeneration. This process may be mediated by tubular structures.     

THE ULTRASTRUCTURE OF CARPOSPOROGENESIS IN CALOGLOSSA LEPRIEURII (DELESSERIACEAE,CERAMIALES)

Carposporogenesis in Caloglossa leprieurii is divided into three cytological stages. At stage I, the young spores have few plastids and little starch. Abundant dictyosomes secrete a gelatinous wall layer in scale-like units. At stage II, dictyosomes produce a second fibrillar wall component in addition to the gelatinous constituent. Large fibrillar vesicles accumulate in the cytoplasm. Production of gelatinous material decreases in this stage. By stage III, starch grains and fully developed plastids are abundant. Rough endoplasmic reticulum occupies much of the peripheral cytoplasm. A dense, granular proteinaceous component appears in the wall in association with the fibrillar layer. Arrays of randomly oriented tubules are scattered in the cytoplasm. The mature carpospore is surrounded by an outer gelatinous wall layer and an inner fibrillar layer. Few dictyosomes persist in the mature spore. Carposporogenesis in Caloglossa is compared with that in other red algae.     

Aspects of sieve element ultrastructure in Primula obconica

Summary At maturity, the enucleate sieve element of Primula obconica is lined with a parietal layer of cytoplasm consisting of plasmalemma, one or more cisterna-like layers of endoplasmic reticulum, numerous mitochondria and plastids, and a membrane which apparently separates these cytoplasmic components from a large central cavity. The central cavity contains numerous longitudinally oriented slime tubules. We believe these tubules normally form strands which run the length of the cell and traverse consecutive cells through the sieve-plate pores. Developmental aspects are discussed.This research has been supported by NSF Grant GB 3193.     

Developmental Aspects of Ultrastructure and Histochemistry of the Stylar Transmitting Tissue of Nicotiana sylvestris

The structure and histochemistry of the solid style of Nicotiana sylvestris Speg. and Comes have been studied by light and electron microscopy. The transmitting tissue develops large intercellular spaces filled with secretions rich in proteins and carbohydrates during maturation. The cells possess large nuclei, numerous plastids with starch grains, mitochondria, ribosomes and well developed endoplasmic reticulum and golgi apparatus. The plastids in the stylar region immediately below the stigma produce electron-dense osmiophilic substances which are probably transferred into the cytoplasm by a process resembling budding-off of vesicles. The Golgi apparatus may use the starch grains as a source of sugars for the synthesis and secretion of extracellular polysaccharides. The structural and cytochemical differences between the glandular cells of the stigma and the stylar transmitting tissue are discussed.     

STUDIES ON THE ULTRASTRUCTURE OF THE GUARD CELLS OF OPUNTIA

The guard cells of Opuntia contain numerous mitochondria, elements of endoplasmic reticulum, dictyosomes, and microbodies. A complex array of small to large vacuoles which contain small, membrane-bounded vesicles occur in each guard cell. The variety of cytoplasmic constituents and vacuoles suggest that the guard cells are complex in function. A highly reduced grana-fretwork system within the plastids indicates that the photosynthetic capacity of the guard cells is probably rather low. No plasmodesmata occur in the walls between the guard cells and the subsidiary cells while there are numerous invaginations of the guard cell plasmalemmas. Many of the variations in the plasmalemma probably indicate that the plasmalemma is a highly active interface.     

CYTOLOGY OF DIFFERENTIATING TRACHEARY ELEMENTS I. ORGANELLES AND MEMBRANE SYSTEMS

The distribution of organelles, membrane systems, and ribosomes is not at any time obviously related to the pattern of secondary wall in helically thickened tracheary elements in leaves of Beta vulgaris L. (sugar beet) and Cucurbita maxima Duchesne, fixed with potassium permanganate and osmium tetroxide. During the differentiation of the secondary wall, cisternae of the endoplasmic reticulum and dictyosomes are particularly conspicuous, and the dictyosomes are associated with numerous vesicles. Similar vesicles appear to be in various stages of fusion with the secondary wall thickenings. The tracheary elements contain plastids which may include starch granules. Ribosomes occur free in the cytoplasm and in association with endoplasmic membranes.     

锦橙汁囊的超微结构

用常规电镜方法观察了锦橙［Ｃｉｔｒｕｓｓｉｎｅｎｓｉｓ （Ｌ．） Ｏｓｂ．］汁囊从原始细胞到发育为一个具柄的成熟汁囊的过程中,汁囊构成细胞超微结构的变化。锦橙汁囊原始细胞及发育为球状体时的构成细胞以及柱状结构顶端的细胞都是一种典型的分生组织细胞。在细胞质中有包括线粒体、质体、内质网、核糖体等丰富的细胞器,但没有观察到高尔基体。这些分生细胞分裂一段时期后就停止活动,逐渐分化为适应贮藏功能的液泡化薄壁细胞。分生细胞开始分化时,在细胞中出现许多小液泡和高尔基体。这些小液泡逐渐地融合,同时细胞质变少,最后形成一个有中央大液泡的薄壁细胞,在紧贴细胞膜的薄薄的一层细胞质中有线粒体、质体、高尔基体以及含有许多脂滴的杂色体。但成熟果实中汁囊的薄壁细胞中几乎没有任何细胞器。     

Ultrastructural Aspects of the Glandular Cells from the Secretory Trichomes and from the Cell Suspension Cultures of Achillea millefolium L. ssp. millefolium

The ultrastructure of the glandular cells of the floret secretorytrichomes from Achillea millefolium L. ssp. millefolium (yarrow)was examined before and after anthesis and compared with theultrastructure of the cells from the cell suspension culturesobtained from the same plant. The profuse tubular structuresobserved in the plastids of the glandular cells of the trichomesduring the pre-secretory stage were much reduced in the secretorystage and showed an osmiophilic content. Some endoplasmic reticulumprofiles could be seen adjacent to the plastids. Later in thesecretory stage, the secretion appeared in the periplasmic spacebetween the cells of the upper tiers and in the sub-cuticularspace. Finally the secretion was released by rupture of thecuticle. At the lag phase, the cells from the cell suspensioncultures of yarrow were characterized by the presence or plastidswith tubular structures, similar to those observed in the plastidsof the trichomes in the pre-secretory stage. By the end of thelag phase accumulations of starch were observed inside the plastids.At the beginning of the exponential phase, the tubular structuresof the plastids started to show an osmiophilic content and theaccumulations of starch were still present. At the end of thisphase starch disappeared from the plastids and only osmiophilictubular structures were observed. Rough endoplasmic reticulumas well as smooth endoplasmic reticulum profiles were frequentlyin close association with plastids and mitochondria. At thestationary phase a very large vacuole filled the cells, andin the remaining cytoplasm some endoplasmic reticulum profilesand osmiophilic droplets were observed.Copyright 1994, 1999Academic Press Achillea millefolium L. spp. millefolium, yarrow, ultrastructure, trichomes, glandular cells, plant cell suspension cultures     

麻疯树小孢子发育的研究

用透射电镜观察了麻疯树(Jatropha curcas L.)小孢子发育的超微结构。小孢子母细胞时期内质网和质体较多;减数分裂和四分体时期,细胞处于明显的代谢活跃状态,细胞器丰富,主要有内质网、线粒体、质体、高尔基体和球状体;在小孢子发育早期和晚期,线粒体和内质网仍较丰富;小孢子经过高度的不对称分裂后,形成较大的营养细胞和较小的生殖细胞,营养细胞中细胞器数量明显减少,含大量的淀粉和脂类物质,生殖细胞中脂类物质丰富;表皮、药室内壁和中层细胞在小孢子母细胞和四分体时期淀粉粒丰富,小孢子时期明显减少,绒毡层从小孢子母细胞至小孢子发育晚期的细胞器都很丰富,主要为内质网、质体和线粒体,为二胞花粉发育奠定基础。     

Cotton embryogenesis: The pollen cytoplasm

Summary The ultrastructure and composition of cotton (Gossypium hirsutum) pollen, exclusive of the wall, was examined immediately before and after germination. The pollen grain before germination consists of two parts: the outer layer and a central core. The outer layer contains large numbers of mitochondria and dictyosomes as well as endoplasmic reticulum (ER). The core contains units made of spherical pockets of ER which are lined with lipid droplets and filled with small vesicles; the ER is rich in protein and may contain carbohydrate while the vesicles are filled with carbohydrate. Starch-containing plastids are also present in the core as are small vacuoles. The cytoplasm of the pore regions contains many 0.5 spherical bodies containing carbohydrate. After germination the ER pockets open and the lipid droplets and small vesicles mix with the other portions of the cytoplasm. With germination the pore region becomes filled with mitochondria and small vesicles. The vegetative nucleus is large, extremely dense and contains invaginations filled with coils of ER. A greatly reduced nucleolus is present in the generative cell which is surrounded by a carbohydrate wall. The cytoplasm of the generative cell is dense and contains many ribosomes, a few dictyosomes and mitochondria, many vesicles of several sizes, and some ER. No plastids were identified. The generative nucleus is also dense with masses of DNA clumped near the nuclear membrane. An unusual tubular structure of unknown origin or function was observed in the generative cell.     

COTTON EMBRYOGENESIS: THE EARLY DEVELOPMENT OF THE FREE NUCLEAR ENDOSPERM

An electron microscope study was made of the central cell and the development of the free nuclear endosperm surrounding the zygote and synergids during the first three days after pollination. The cytoplasm of the central cell, concentrated around the partially-fused polar nuclei, contains many ribosomes, mitochondria and large, dense, starch-containing plastids, some dictyosomes and lipid bodies, and long, single cisternae of rough endoplasmic reticulum (RER) that frequently terminate in whorls. Dense, core-containing microbodies are closely associated with the RER. After fertilization the cytoplasm of the 2-and 4-nucleate endosperm shows an increase in number of dictyosomes, and in amount of RER which becomes stacked in arrays of parallel cisternae. Cup-shaped plastids are associated with many long, helical polysomes. Perinuclear aggregates of dense, granular material also appear after fertilization. Granular aggregates and helical polysomes disappear after the first few divisions of the primary endosperm nucleus. During the second and third days of development there is an increase in dictyosome number and RER proliferation, and endosperm nuclei become deeply lobed. Concurrently, there is a sharp decline in the starch and lipid reserves of the central cell and elaborate transfer walls are formed at the micropylar end of the embryo sac and on the outer surface of the degenerating synergid. The transfer walls contain groups of small, membrane-bound vesicles, and are associated with large numbers of mitochondria and with the smooth endoplasmic reticulum.     

Differentiation of stomatal meristemoids and guard cell mother cells into guard-like cells in Vigna sinensis leaves after colchicine treatment

The temporary development of Vigna sinensis seedlings in the presence of colchicine results in the inhibition of stomata generation and the formation of numerous persistent stomatal meristemoids (P-SM) and guard cell mother cells (P-GMC). Before dividing differentially or becoming GMC, the untreated meristemoiidsundergo a preparatory differentiation, during which a synthesis of new densely ribosomal cytoplasm, an increase of nuclear size, and a detectable proliferation of all the organelles are observed. The same process appears depressed and delayed in treated meristemoids; the cells have usually undergone only part of it when they reach the C mitosis. After the inhibition of their division, the bulged meristemoids II and GMC increase further in size, synthesize new nonribosomal cytoplasm, and start vacuolating slowly. The plastids also increase in size, change in shape, and become able to synthesize large quantities of starch. The cells retain a ribosomal cytoplasm, rough ER membranes, and active dictyosomes for a long time. At the advanced stages of differentiation, the microtubules reappear in the cells even when the plant remains under colchicine treatment. When mature, the P-GMC and P-SM are quite similar to the guard cells and possess considerably thickened periclinal walls, numerous mitochondria, and small vacuoles, while the nucleus, the plastids, and the cytoplasm occupy significant parts of the cell volume. In the epidermis displaying open stomata in light, significant K⁺ quantities are detectable in guard cells and P-GMC or P-SM, while they are almost absent from their surrounding cells. When the stomata close in darkness, K⁺ is accumulated primarily in the subsidiary or typical epidermal cells surrounding these idioblasts and only minimally inside them. Besides, the P-GMC and P-SM, like the guard cells, retain the starch for a long time and build up considerable starch quantities from exogenously supplied sugars.Abbreviations P-GMC persistent guard cell mother cell - PSM persistent stomatal meristemoid - ER endoplasmic reticulum     

Quantitative analysis of ultrastructural changes during zygotic and somatic embryogenesis in pearl millet (Pennisetum glaucum [L.] R. Br.)

Ultrastructural changes during zygotic and somatic embryogenesis in pearl millet (Pennisetum glaucum [L.] R. Br.) were quantified using morphometric techniques. The total area per cell profile and the cell volume percentage of the whole cell, endoplasmic reticulum (ER), Golgi bodies, mitochondria, nuclei, lipids, plastids, starch grains and vacuoles were measured and comparisons made between three zygotic and three somatic embryo developmental stages. All measurements were taken from scutellar or scutellar-derived cells. Zygotic embryogenesis was characterized by increases in cell size, lipids, plastids, starch, Golgi bodies, mitochondria and ER. Somatic embryogenesis was characterized by two phases of cell development: (1) the dedifferentiation of scutellar cells involving a reduction in cell and vacuole size and an increase in cell activity during somatic proembryoid formation and (2) the development of somatic embryos in which most cell organelle quantities returned to values found in late coleoptile or mature predesiccation zygotic stages. In summary, although their developmental pathways differed, the scutella of somatic embryos displayed cellular variations which were within the ranges observed for later stages of zygotic embryogenesis.     

Ultrastructure of Jincheng Juice Sac of Citrus sinensis

Ultrastructure of Jincheng juice sac of Citrus sinensis (L.) Osb. was continuously investigated from the initial cell to the stalk-bearing sac. The initial cell and cells formed globularstructure, as well as the uper cells of the column-structure were typical meristem cells with mitochondria, plastids, rough endoplasmic reticulum, rich ribosome without Golgi body in their dense cytoplasm. These meristem cells would differentiate into parenchyma ceils pro2 viding storage function. At the beginning of differentiation of the meristem cells, the number of small vacuoles increased and some Golgi bodies appeared. Small vacuoles gradually fused into a central vacuole. During the fusion of small vacuoles, the cytoplasm became thinned, but still contained mitochondria, plastids, Golgi bodies, end0plasmic reticulum and some chromplasts with lipid drops. Almost no organelle were ever observed in the parenchyma cells of juice sac from mature fruit.