Histogenesis of the transmitting tract in Strelitzia reginae

Organisation and development of the stigmatic, stylar and ovarian parts of the transmitting tract in Strelitzia reginae were evaluated. They were characterised by 1) cell shape, 2) appearance of distal cell wall, 3) type of plastid, 4) and vacuolar system. The long stigmatic trichomes have a secondary irregular wall layer separated from the primary wall. Cell structures include pleomorphic plastids with vesiculated thylakoids and frequently a crystal or a lipidic globule. In early stages of bud development the extensive endoplasmic reticulum (ER) is smooth, whereas it is mainly rough in older buds. Coated vesicles are frequent, as are dictyosomes. Prominent invaginations along the plasma membrane contain floccular deposits in the older flower buds. These deposits are similar in structural appearance to material in the large vacuoles. The basal part of the stigma has wedge-shaped cells with wall ingrowths. Three stages of stigmatic secretion during the development were characterised. The stylar canal is initially narrow but widens subsequently. The cuticle is detached and the apical cell walls show a fringed surface; from this wall inbuddings develop shortly before anthesis. At this stage sheets of rough ER are evident in the cell cortex. The plastids have a few vesiculated thylakoids, proteinaceous crystals and starch grains. The epithelial cells of young buds have numerous vacuoles, the volume of which decreases in more mature cells. The stylar canal is filled with a secretion at all stages of bud development. The face of the ovarian transmitting tract, lining the placenta, is smooth in young buds but lobed in older ones due to the division pattern of the epithelial cells. These cells are large, elongated and culumnar as young but narrow and wedge-shaped when more mature. Cell wall inbuddings are formed late during bud development.     

Calcium snapshots in the stigma and style of medlar (Lycium barbarum L.) during pollen germination and pollen tube growth suggest active calcium oscilations

Abstract

The stigma (tip of the pistil) of medlar is wet and covered with stigmatic exudate at anthesis. The exudate contains many vesicles with abundant calcium precipitates. After deposition on the stigma, the pollen grain undergoes hydration, displaying signs of calcium ion (Ca²⁺) transfer from the exudate vesicles into the pollen grains. Calcium precipitates in the pollen cytoplasm are concentrated into small vacuoles that fuse to form large vacuoles, which provide turgor pressure to push the cytoplasm to the apical region of the growing pollen tube. Many calcium precipitates are present in the stylar transmitting tract, which displays a calcium gradient: fewer precipitates are localised in the distal (upper) transmitting tissue below the stigma, and more precipitates are present in the transmitting tract at the style base. The emporal and spatial distribution of calcium in the stigma and style of medlar suggests that it satisfies the demand for calcium in vivo and played some functional significance.     

山茱萸花柱和柱头的发育解剖学及组织化学

山茱萸成熟雌蕊的柱头为干型,具表皮起源的单细胞乳突。在开花后授粉前乳突细胞的顶部发生凹陷,授粉后乳突细胞迅速萎缩。花柱在发育初期为开放型,发育后期花柱道消失,成为一种具特殊结构的闭合型。成熟花柱由表皮、皮层和特殊的引导组织等部分构成,在皮层中贯穿有3条维管束,引导组织的中央则有二列类似腺质的内表皮细胞,该细胞富含蛋白质、核酸和多糖类物质。     

Developmental Aspects of Ultrastructure, Histochemistry and Receptivity of the Stigma of Nicotiana sylvestris

The bilobed papillate stigma of Nicotiana sylvestris Speg. andComes, is covered at maturity with a copious exudate containinglipid, protein and carbohydrate. The stigma is receptive fromthe very early stage of development and it also stains positivelyfor esterase activity. The stigma has three distinct zones:an epidermis with papillae; a subepidermal secretory zone; anda parenchymatous ground tissue. The behaviour of the cells ofthese three zones has been followed from 6 d before anthesisto one day after anthesis and pollination. The cells of theepidermis and the secretory zone stain intensively for lipids,proteins and carbohydrates in the initial stages. The secretoryzone develops large intercellular spaces containing heterogenoussecretory products which also stain positively for the aforesaidthree compounds. At maturity the secretory products are releasedto the surface through gaps formed in the epidermis by cellseparation. The main secretion of the stigma is produced bythe cells of the secretory zone. Less secretion is derived fromthe stigmatic papillae. Some amount of secretion is also releasedfrom the stylar transmitting tissue adjoining the stigma. Theglandular cells of the stigma contain numerous plastids, mitochondria,ribosomes, ER, cytoplasmic lipid droplets and some dictyosomes.The plastids and the vacuoles in the secretory cells of thestigma have a lot of electron dense (osmiophilic) inclusionsrespectively in the initial and later stages of development.The former are probably involved in the production of thesematerials. It is suggested that the proteins are directly secretedby rough ER compartments whereas smooth ER is involved in thesynthesis of lipidic materials. The carbohydrate moiety of theexudate is released by the eccrine mode (sugar mono- and dimers)with some addition of polymers by disintegration of the middlelamellae. The means by which the lipidic and osmiophilic materialis extruded remains unclear. Nicotiana sylvestris, stigma receptivity, organization, stigmatic secretory system, stigmatic exudate     

Structure,ultrastructure, and histochemistry of the pollen tube pathway in the milkweed Asclepias exaltata L.

The structure of the gynoecium and pollen tube pathway in unpollinated and pollinated carpels of Asclepias exaltata L. has been characterized. Pollen tubes penetrate a dry-type stigma, grow intercellularly in a core of solid tissue in the upper style, and subsequently traverse a hollow stylar canal to the ovary where they grow across the placental epithelium to the ovule micropyles. The fine structural characteristics of transmitting cells of the solid style, stylar canal, and placental epithelium indicate a secretory function. Extracellular secretions staining positively for proteins, insoluble carbohydrates, and arabinogalactans/arabinogalactan proteins are present in the solid style, hollow stylar canal, ovary, and micropyle. Micropylar exudate is present subtending the extended cuticle of the embryo sac adjacent to the filiform apparatus of the synergids, providing ultrastructural evidence for a secretion arising from the angiosperm embryo sac.     

Pollen-pistil interaction in kiwifruit (Actinidia deliciosa; Actinidiaceae)

The pollen-pistil interaction has been examined in kiwifruit (Actinidia deliciosa). In this species a large number of seeds are produced in each fruit and a great many pollen grains germinate and grow to reach the ovules. This growth is assisted by an abundant secretion that is present all along the pistilar tract. At anthesis, the stigma is covered by a secretion where the pollen grains germinate and grow. The stylar transmitting tissue is initially rich in starch reserves, but the starch gradually disappears and, concomitantly, an abundant secretion that stains for carbohydrates appears in all of the intercellular spaces. Pollen tube growth relies on this secretion since it is depleted after pollen tube passage, while in unpollinated flowers it remains unaltered throughout the flower life-span. In the ovary a similar situation occurs. The placental surface, where the pollen tubes grow before reaching the ovules, is covered by a number of obturators. At anthesis, these obturators are rich in starch reserves and have an abundant secretion on their outer surface. As time passes, starch disappears while the secretion increases. It is in this secretion that the pollen tubes grow on their way toward the ovules. These observations are discussed in terms of the support given by the pistil to pollen tube growth to achieve the highly successful reproductive performance of this species.     

Transmitting Tissae and Pollen Tube Growth in Sweet Pepper

Fine structural events in the mature stylar transmitting tissue ofsweet pepper (Capsicum frutescens L. var. grossum Bally) have been investigated byelectron microscope with regard to pollen tribe grwoth. The transmitting tissue consists of parenchymatous cells with large intercellular spaces filled with an electron densesubstance. The pollen tubes grow through the intercellular spaces in the intercellular substance. Cells of this tissue are rich in organelles, especially the rough and tubular ER, and numerous lomasomes near the plasma membrane. It is demonstrated that they function as secretory cells. On the other hand, the fact that the transmitting tissue contains many large amyloplastids with several starch grains in the cytoplasm and numerous globular protein bodies in vacuoles, indicates that the transmitting tissue mayhave some nutritive value for the growth of pollen tubes. The results obtained from this observation are in agreement with those of mostspecies reported by other authors and support the conclusion that the transmitting tissue is not a collenchyma tissue and the nature of intercellular substances is essentially same as that of the middle lamella.     

Cotton embryogenesis: The tissues of the stigma and style and their relation to the pollen tube

Summary The stigma of cotton (Gossypium hirsutum) is covered by unicellular hairs. The cytoplasm of these hairs degenerates before the stigma becomes receptive. The vacuole remains intact, but the hair cytoplasm becomes a mass of dark, amorphous material with only a few organelles still being visible. The rest of the stigma consists of thin-walled parenchyma cells with large vacuoles and large amounts of starch. The cells of the style are differentiated into a uniseriate epidermis, vascular tissue, a cortex of thin-walled, vacuolate parenchyma cells, and the transmitting tissue. This latter tissue occupies the center of the style and consists of thick-walled cells with few vacuoles. The cells are rich in starch, ribosomes, endoplasmic reticulum and dictyosomes. They also contain deposits of calcium salts in the form of druses. The pollen germinates on the stigmatic hairs, grows down the outside of the hair and between the cells of the stigma to the transmitting tissue of the style. There the tubes grow between the walls of the cells but do not enter the cells themselves. Some transmitting cells adjacent to the pollen tube degenerate after the tip of the pollen tube has grown past them. However, not all degenerate, and those that do show no fixed spatial relationship to one another. The cells which do degenerate follow a characteristic pattern of breakdown. No ultrastructural evidence was found for the secretion of hydrolytic enzymes by the pollen tube.     

Structure of the style and wet non-papillate stigma of Colophospermum mopane, Caesalpinioideae: Detarieae

The capitate stigma of Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Leonard is an intensely folded bilobed structure. The epidermal layer of the stigma consists of non-papillate cells. Before anthesis the epidermis is covered with a cuticle and thin proteinaceous layer. Elongated subepidermal cells constitute the secretory zone. Cell disintegration in the central region of each stigma lobe leads to cavities that become connected to the central cavity in the style. During early anthesis it appears as if the receptive surface of the stigma is confined to the depressions of the stigma surface and to the cleft between the two stigma lobes as the secretory product and pollen grains are mainly confined to these areas. The secretory products of the stigma and style are released during five different stages from prior to anthesis to late anthesis. The stigmatic exudate appears complex and consists of carbohydrates, proteins and lipids. The style has a hollow, lysigenous, fluid-filled canal that is not lined with an epidermal layer or cuticle. The stylar canal is continuous with the opening between the two stigma lobes and provides an open route for the passage of exudate. The stylar exudate is PAS-positive. The dorsal and ventral bundles that supply the style branch in such a way as to almost form a cylinder around the central transmitting tissue and stylar canal. New sieve elements proliferate before anthesis.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 295–304.     

The transmitting tract in Trimezia fosteriana (Iridaceae). 1. Ultrastructure in the stigma, style and ovary

An ultrastructural investigation of the entire transmitting tract in Trimezia fosteriana (Iridaceae) was undertaken. The transmitting tissue is secretory but transfer cells do not occur at any level. With exception for the stigma papillae, the cells are covered with large amounts of secretory products. The papillae have a thick and ridged cuticle. The cuticle in the rest of the transmitting tract is thin and detached from the cell wall by the secretory products. It is more or less ruptured in the secretory parts of the stigma and ovary. In the stylar canal the major part of the cuticle is continuous and covers the secretory products. The occurence of a large amount of vesicles in the stigma transmitting tissue cells is interpreted as a result of high dictyosome activity. An electron opaque material is produced in the dictyosomes and appears in vesicles and vacuoles but also between the plasma membrane and the cell walls in the stigma. A small amount of such material is present in the cell walls. Corresponding material is also present in the style and the ovary but declines basipetally. Plastids with strongly electron opaque plastoglobules are present at all levels in the transmitting tract.     

The transmitting tract in Trimezia fosteriana (Iridaceae).

Observations of the transmitting tract cells in Trimezia fosteriana were made from the pre-secretory stage until anthesis. Secretory products appear about 14 days before anthesis in all parts of the pistil. Simultaneously starch disappears from the plastids and the dictyosomes are surrounded by more and larger vesicles than before. In the beginning of the secretory stage multivesicular bodies may be in contact with ER profiles and an ER origin is therefore presumed. Later during the secretory stage the multivesicular bodies are larger and more abundant. Their envelope is often partly fused with the plasma membrane and vesicle swarms are common on the outside of it. Close to flower opening many organelles change in appearence. RER becomes more abundant and the mitochondrial matrix highly electron dense and the cristae expanded. Starch grains reappear and large ones are common in the stigma and ovary plastids. The dictyosomes are numerous and surrounded by the largest vesicles observed during the secretory stage. Osmiophilic granules are common in the dictyo-some vesicles and under the cell walls abutting the transmitting tract. In the ovary they are present one week before anthesis. In the stigma and style corresponding granules of high electron density appears at the day of flower opening. The extracellular secretory product contains fibrillar and granular substances consisting of carbohydrates, including pectic substances, and proteins.     

GYNOECIAL DEVELOPMENT,POLLINATION, AND THE PATH OF POLLEN TUBE GROWTH IN THE TEPARY BEAN,PHASEOLUS ACUTIFOLIUS

The gynoecium of Phaseolus acutifolius var. latifolius, a self-compatible legume, is characterized by a wet non-papillate stigma, an intermeditae hollow/solid style type, and secretory cells on the ventral surface of the ovary which direct pollen tube growth. The stigma is initially receptive 5–6 days prior to anthesis. Production of stigmatic secretions, composed primarily of carbohydrates and lipids, fragment the cuticle covering epidermal cells of the stigma early in ontogeny; the lipidic aspect of the copious secretions apparently serves to inhibit desiccation after the cuticle is ruptured. Stylar canal development occurs as a combination of elongation of a basal canal present early in development, and dissolution of part of a solid transmitting tract tissue just below the stigma. Anthers dehisce and the tricolporate pollen is released onto the receptive stigma one day before anthesis. Following initial growth in intercellular spaces in the transmitting tract of the stigma, pollen tubes adhere to epidermal secretory cells along the ventral side of the stylar canal and upper ovary; here the transmitting tract is apparently limited in the number of tubes it can accommodate, providing a possible site of selection of male gametes.     

STIGMA,STYLE, AND OBTURATOR OF ORNITHOGALUM CAUDATUM (LILIACEAE) AND THEIR FUNCTION IN THE REPRODUCTIVE PROCESS

Transmitting tissue in Ornithogalum is divided into three regions corresponding to classical divisions of the gynoecium: stigma, style, and ovary. The stigma differentiates from epidermal cells of the stylar apex. These cells form the stigmal papillae and have dense cytoplasm with abundant ER and lipid bodies. Papillae have walls with small transfer-ingrowths. At floral receptivity, papillae secrete a small amount of surface exudate. Epidermal cells of the style contain numerous spherosomes and have thin filaments of cytoplasm traversing the central vacuole. The stylar cortex is composed of 3-6 layers of parenchyma cells which contain numerous spherosomes and often have secondary vacuoles. Vascular tissue in the style consists of one collateral bundle in each lobe. Cells of the epidermal layer lining the stylar canal are secretory. They are initially vacuolate but fill progressively with dense cytoplasm as their secretory activity increases. Secretory activity occurs in three phases, each characterized by a particular organelle population and secretory product. At anthesis, the canal is filled with an exudate consisting of carbohydrate, protein, and lipid. In the ovary, the obturator differentiates from cells at the base of the funiculus and the tip of the carpel margins. It forms a pad of tissue which covers most of the former placenta. The obturator is secretory and produces a surface exudate. We believe our observations on Ornithogalum support the hypothesis that all transmitting tissue is of the same morphological origin and that it provides nutritive and chemotropic factors for pollen tube growth.     

植物生殖系统中传递细胞的研究进展

 本文介绍了植物传递细胞的基本概念。记录了高等植物生殖系统中所发现的传递细胞不同的分布位置,并以苔藓植物的胎座、小孢子及花粉、花柱道和柱头的引导组织、胚襄、胚柄和胚乳、种皮和子叶中的传递细胞为例,说明了这些传递细胞与溶解物质短途运输的关系。最后提出了植物传递细胞研究的进展,包括实验方法,新概念和有关质膜运输的基因表达等方面。     

A lipid transfer-like protein is necessary for lily pollen tube adhesion to an in vitro stylar matrix

Flowering plants possess specialized extracellular matrices in the female organs of the flower that support pollen tube growth and sperm cell transfer along the transmitting tract of the gynoecium. Transport of the pollen tube cell and the sperm cells involves a cell adhesion and migration event in species such as lily that possess a transmitting tract epidermis in the stigma, style, and ovary. A bioassay for adhesion was used to isolate from the lily stigma/stylar exudate the components that are responsible for in vivo pollen tube adhesion. At least two stylar components are necessary for adhesion: a large molecule and a small (9 kD) protein. In combination, the two molecules induced adhesion of pollen tubes to an artificial stylar matrix in vitro. The 9-kD protein was purified, and its corresponding cDNA was cloned. This molecule shares some similarity with plant lipid transfer proteins. Immunolocalization data support its role in facilitating adhesion of pollen tubes to the stylar transmitting tract epidermis.     

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.     

鹅掌楸属植物引导组织和花粉管生长

应用光学显微镜和常规石蜡切片技术研究了鹅掌楸属（ＬｉｒｉｏｄｅｎｄｒｏｎＬ．）两种植物雌蕊引导组织的分布和个体发育,引导组织是由心皮边缘或内表面的表皮细胞层或亚细胞层发育形成,是由一层细胞组成的连续层,覆盖干柱头、花柱道和珠柄的表面,引导组织的细胞形态学因其所在部位不同而有差异。在电境水平上研究了柱头和花柱引导组织的超微结构,引导组织细胞是分泌型的传递细胞,其分泌面发育了明显的壁内突,细胞质中富含内质网、多聚核糖体、各种小泡、高尔基体和线粒体,大液泡通常远离分泌面。文中还探讨了花粉管生长后引导组织的变化。     

竹节参雌配子体发育的研究

本文报道了竹节参(Panax japonicus C.A.Mey)雌配子体(胚囊)的发育过程。竹节参大孢子母细胞减数分裂产生线形排列的大孢子四分体。胚囊发育属蓼型,由合点端大孢子发育而成。游离核胚囊时期,胚囊珠孔端的细胞器种类和数量都较胚囊合点端多;胚囊合点端相邻的珠被细胞中有含淀粉粒的小质体,与胚囊珠孔端相邻的退化中的非功能大孢子中则有含淀粉粒的大质体和大类脂体。成熟胚囊中,反足细胞较早退化;极核融合成次生核;卵细胞高度液泡化,细胞器数量较少;助细胞则有丰富的细胞器和发达的丝状器。PAS反应表明,受精前的成熟胚囊中积累淀粉粒。次生核受精后,很快分裂产生胚乳游离核,到几十至数百个核时形成胚乳细胞。卵细胞受精后则要经过较长的休眠期。     

Structural studies of pollen tube growth in the pistil ofStrelitzia reginae

Summary For this work we have used various microscopical methods (LM, SEM, and TEM) to study pollen tube growth and interaction with the transmitting tisse inStrelitzia reginae, which has an open style. By the use of SEM it was possible to trace the exact route of the pollen tubes in the ovary of this plant and demonstrate that they exclusively follow the outlines of the transmitting tissue. The average rate of pollen tube growth through the style was 1.8 mm h^–1. The most significant effect of the pollination was a thickening of the distal wall of the subepithelial cells in the style. A secretion covers the stigma and the ovarian transmitting tissue and fills the stylar canal. This exudate contains lipids, polysaccharides, and proteins.     

蝇子草腺毛的形态发生及超微结构的研究

蝇子草茎叶上着生粘液毛,它是由３个细胞构成的单列腺毛。电镜观察表明,在刚形成的腺毛柄细胞中,质体最发达,而且大多数质体内含有淀粉粒。在柄细胞中,有些质体和液泡膜融合产生小泡,可能以胞饮方式将质体内的淀粉粒降解后的产物转以液泡内。有些质体则可能直接突入液泡并在液泡内降解其淀粉粒。在头细胞发育中,含淀粉粒的质体增多。后期大多数质体消失,同时出现了大量的充满纤丝状物质的小不包和大泡。最后,小泡和大泡相琵