烟草花粉萌发和花粉管生长期间柱头和花柱中的钙分布

烟草柱头表面有两层覆盖物,其中含有少量细小的钙颗粒.花粉落到柱头上后,储存在花粉外壁中的钙被释放到覆盖层中.当花粉管穿过覆盖层长入柱头细胞之间时,花粉管顶端的细胞壁中出现了大量的细小钙颗粒.开花后22 h观察时,在花柱引导组织中形成了钙的梯度分布:花柱上部引导组织中的钙较少,而下部连接子房处的花柱引导组织中含有较多的钙颗粒.去雄花开花后1 d时,花柱上部引导组织中的钙明显增多;3 d时,连柱头细胞中也出现了较多的钙颗粒.讨论了烟草花柱引导组织中钙梯度分布和花粉管生长的关系.     

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.     

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.     

Distribution of calcium in the stigma and style of tobacco during pollen germination and tube elongation

Potassium antimonate was used to locate loosely bound calcium in the stigma and style of tobacco. The tobacco stigma is wet and covered by a thick layer of glycoprotein exudate at anthesis. The exudate contains abundant vesicles, which are densely labeled with calcium precipitates. When pollen grains arrive at the stigma, become hydrated, and as the pollen swells, Ca²⁺ precipitates accumulate at the aperture. Calcium precipitates that accumulate in pollen cytoplasm are initially concentrated within small vacuoles, but as germination proceeds these appear to fuse, forming prominent, densely labeled vesicles that preferentially accumulate near the proximal region of the growing tube. Although the stigma has abundant particles, few calcium precipitates are observed in the transmitting tissue from anthesis to 11 h after pollination. However, at 22 h after pollination, accumulation of calcium increases distally from the stigmatic interface with the transmitting tissue through the length of the style to the ovary. An examination of flowering plants with differing floral biology will be needed to understand the role of loosely bound calcium accumulation and its relationship to tissue-level changes in calcium uptake, maintenance of other calcium pools, including [Ca²⁺]_cyt, and in pollen and style maturation during the progamic phase.     

莴苣授粉前后柱头与花柱中钙的分布变化

莴苣柱头呈两裂片状,有接受花粉的接受面和非接受面之分。授粉前后,柱头接受面乳突细胞的细胞壁中贮存丰富的细小钙颗粒,而非接受面的表皮细胞壁中的钙颗粒很少。在花柱组织中钙的分布具有明显特征,在同一水平上,钙主要分布在引导组织的质外体中,如细胞壁和细胞间隙中,而在引导组织外的薄壁组织中钙主要分布在的细胞内液炮和细胞壁中以及维管束导管内。在花柱不同水平上,花柱中的钙呈现出梯度分布,顶端各组织中的钙颗粒较少,基部各组织中的钙颗粒较多。授粉后1h花柱基部组织的钙颗粒增多,钙梯度分布现象增强。花柱引导组织中的钙梯度分布很可能是吸引花粉管向下生长的原因。讨论了莴苣花柱引导组织中钙梯度分布特征和花粉管在其体内生长的关系。     

莴苣授粉前后柱头与花柱中钙的分布变化

莴苣柱头呈两裂片状,有接受花粉的接受面和非接受面之分。授粉前后,柱头接受面乳突细胞的细胞壁中贮存丰富的细小钙颗粒,而非接受面的表皮细胞壁中的钙颗：粒很少。在花柱组织中钙的分布具有明显特征,在同一水平上,钙主要分布在引导组织的质外体中,如细胞壁和细胞间隙中,而在引导组织外的薄壁组织中钙主要分布在的细胞内液泡和细胞壁中以及维管束导管内。在花柱不同水平上,花柱中的钙呈现出梯度分布,顶端各组织中的钙颗粒较少,基部各组织中的钙颗粒较多。授粉后1h花柱基部组织的钙颗粒增多,钙梯度分布现象增强。花柱引导组织中的钙梯度分布很可能是吸引花粉管向下生长的原因。讨论了莴苣花柱引导组织中钙梯度分布特征和花粉管在其体内生长的关系。     

The structure and cytochemistry of the pistil of Hypericum calycinum: the style

Summary A typical style of Hypericum calycinum is solid with a core of transmitting tissue traversing the whole length of the style. This transmitting tissue consists of loosely arranged cells and large intercellular spaces filled with a secretion product. The secretion product is rich in lipids, but poor in proteins and polysaccharides. The intercellular spaces of the transmitting tissue originate partly by a separation of cells as a result of the decomposition of the middle lamella and partly by degeneration of some of the cells of the transmitting tissue. H. calycinum is self-compatible. Both self- and cross-pollinations result in profuse pollen germination on the stigma and pollen tube growth through the style. The data on Hypericum is discussed in relation to information available on other solidstyled systems.     

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。     

Cotton embryogenesis: The pollen tube in the stigma and style

Summary The ultrastructure and composition of the pollen tube of cotton (Gossypium hirsutum) growing in the tissues of the stigma and style of the flower were examined. The distal portion of the tube is densely cytoplasmic and contains the vegetative nucleus and the two sperms. The vegetative nucleus is highly convoluted and the membrane contains many pores and connections with the ER. No organized nucleolus is present but 4–6 membrane-bound, protein containing bodies are found in the nucleus. Mitochondria containing numerous cristae are abundant in the cytoplasm. Dictyosomes are also plentiful and are engaged in the production of many large vesicles. Rough ER is conspicuous and polysomes are found in the cytoplasm. Plastids are few in number, poorly developed, and contain little starch. Many uniform, small vesicles are found throughout the cytoplasm. Lipid bodies frequently with small vesicles associated with them are found in the tube. In the proximal region vacuoles form and the cytoplasm becomes pressed against the wall. In the transition zone the ER frequently becomes distended and filled with protein. The wall has two distinct layers: one strongly PAS positive, the other faintly PAS positive. The inner wall is apparently formed by the deposition of large dictyosome vesicles. Plug structure and development were studied.     

STIGMA,STYLE, AND OBTURATOR OF SOYBEAN,GLYCINE MAX (L.) MERR. (LEGUMINOSAE) AND THEIR FUNCTION IN THE REPRODUCTIVE PROCESS

Soybeans have a wet stigma overtopped by a pellicle that originates from the cuticle. There are numerous exudate-filled, axially oriented channels between cells of the transmitting tissue in the stigma and style. Pollen tubes grow in these channels and receive nutrition and mechanical guidance. Transmitting-tissue cells of the obturator are secretory also, but the obturator in soybean does not appear to control direction of pollen tube growth mechanically. The significant function of transmitting tissue in soybeans is to provide nutrition and to control direction of pollen tube growth.     

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.     

Heterostyly inPrimula. 2. Sites of pollen inhibition,and effects of pistil constituents on compatible and incompatible pollen-tube growth

Summary In incompatible (intramorph) pollinations of the heterostylousPrimula vulgaris, pollen germination or tube growth may be partially inhibited in several sites associated with the stigma or style. Blockage may occur, a) on the stigma surface through the failure of germination or of pollen tube penetration after germination, b) in the stigma head during the passage of the tube through the specialized transmitting tissue of the head, or c) in the transmitting tract of the style. None of the barriers is complete, and the prohibition of selfing or intramorph crossing depends upon the cumulative screening effect of one following upon the other. In both morphs, the germination of incompatible pollen on the stigma is enhanced in high ambient relative humidity, but many tubes still fail to penetrate the stigma. Those that do are retarded or blocked in their growth in the transmitting tissues of the stigma head and style. Crude extracts from the tissues of the stigma head and style show some differential effect on the growth of pollen tubesin vitro, and dialysates of extracts containing high molecular weight fractions show a consistent differential effect, those from thrum tissues retarding thrum tubes while having a lesser effect on pin tubes, and those from pin tissues retarding pin tubes while having lesser effect on thrum. It is suggested that the factors influencing tube growth are present in the intercellular secretions of the transmitting tract.     

Pollen-pistil Interaction in a Non-pseudogamous Apomict,Commiphora wightii

Structural and cytochemical details of the pistil and the interactionof pollen and pistil were studied in a non-pseudogamous apomict,Commiphorawightii.The anthers in the male and bisexual flowers producefunctional pollen grains. The stigma is of the wet and papillatetype. The style is typically solid with two strands of transmittingtissue that traverse the entire length of the style. There isa marked reduction in the area occupied by the transmittingtissue from the stigma to the base of the style. The cells ofthe transmitting tissue are isodiametric in transverse as wellas longitudinal section and do not form longitudinal files ofelongated cells as reported for other taxa. Proteins could notbe localized in the intercellular matrix. Although pollen grainsgerminate on the stigma, pollen tubes do not grow beyond theproximal one third of the style. Changed orientation of thecells of the transmitting tissue and absence of proteins inthe intercellular matrix could account for the failure of thepistil to support pollen growth.Copyright 1998 Annals of BotanyCompany Guggul, pollen-pistil interaction, non-pseudogamous apomict,Commiphora wightii, transmitting tissue     

The transmitting tissue of Nicotiana tabacum is not essential to pollen tube growth, and its ablation can reverse prezygotic interspecific barriers

The Nicotiana tabacum transmitting tissue is a highly specialized file of metabolically active cells that is the pathway for pollen tubes from the stigma to the ovules where fertilization occurs. It is thought to be essential to pollen tube growth because of the nutrients and guidance it provides to the pollen tubes. It also regulates gametophytic self-incompatibility in the style. To test the function of the transmitting tissue in pollen tube growth and to determine its role in regulating prezygotic interspecific incompatibility, genetic ablation was used to eliminate the mature transmitting tissue, producing a hollow style. Despite the absence of the mature transmitting tissue and greatly reduced transmitting-tissue-specific gene expression, self-pollen tubes had growth to the end of the style. Pollen tubes grew at a slower rate in the transmitting-tissue-ablated line during the first 24 h post-pollination. However, pollen tubes grew to a similar length 40 h post-pollination with and without a transmitting tissue. Ablation of the N. tabacum transmitting tissue significantly altered interspecific pollen tube growth. These results implicate the N. tabacum transmitting tissue in facilitating or inhibiting interspecific pollen tube growth in a species-dependent manner and in controlling prezygotic reproductive barriers.     

Pistil Structure and Pollen Tube Pathways in Leptospermum myrsinoides and L. continentale (Myrtaceae)

Pistil structure and pollen tube growth were investigated inLeptospermum myrsinoides and L. continentale (Myrtaceae). BothL. myrsinoides and L. continentale pistils consist of an ovarywith five locules, a style and a five-lobed dry, papillate stigma.A centrally located stigmatic cleft is present but extends onlyto the base of the stigma. Pollen germinates and grows intercellularlythrough the stigma into the central transmitting tissue of thestyle. Pollen tubes do not grow down the stigmatic cleft. Atthe base of the style the transmitting tissue separates intofive, each tract leading through the placenta to one of thefive locules. The pollen tubes continue to grow intercellularlythrough these five tracts entering the locules between the lobesof the placenta. Pollen tubes are smooth-walled and straightwhilst in the transmitting tissue of the style but produce shortlateral branches at regular intervals when in the locules. Branchingcontinues until pollen tubes enter ovules. It is suggested thatthe observed branching in the locules is a result of pollentubes following a chemotropic or thigmotropic pathway to theovules. This behaviour was consistent in all pistils examinedand no difference was observed in the behaviour of self- orcross-pollen tubes in the style or ovary.Copyright 1994, 1999Academic Press Leptospermum myrsinoides Schldl., Leptospermum continentale J. Thompson, pistil structure, pollen tube pathway, pollen tube branching     

花柱和花粉胞外钙调素对花粉萌发和花粉管伸长的影响

以烟草为材料,通过半体内实验,就花柱和花粉胞外钙调素对花粉萌发和花粉管伸长的影响进行了观察。发现用EGTA及钙调素抗血清处理柱头或花粉均可抑制花粉在柱头上的萌发;向花柱引导组织中显微注射纯化钙调素可促进花粉管束伸长,而注射钙调素抗血清可抑制花粉管束伸长;同时证实玉米花柱和花粉细胞壁中均存在钙调素及钙调素结合蛋白,而且花粉和花柱细胞壁中钙调素结合蛋白的种类有差异。结果表明存在于花粉和花柱细胞外的钙调素对花粉萌发和花粉管伸长均有促进作用。     

Structure and development of the stigma, style and ovary of Caesalpinia pulcherrima (L.) Sw., post-anthesis, pre- and post-pollination

The stigma of Caesalpinia pulcherrima is crateriform. The crater continues as a slit-like canal through the style and into the ovary. Both crater and canal are lined by several layers of fusiform and thin-walled cells which are continuous in two narrow regions in the ovary. Postanthesis and before pollination, the middle lamella of cells lining the stigmatic crater and stylar transmitting tissue undergoes dissolution. This occurs in a progression down the style with cells separating partially or wholly from neighbours. Dissolution is initiated at intercellular junctions where wall fibrils loosen and variously-sized and -shaped holes appear. Cytoplasmic changes include increased dictyosome activity, increased rough and smooth endoplasmic reticulum at the periphery of cells and accumulation of electron opaque deposits at the plasma membrane. The crater fills with stigmatic fluid and the diameter of the stylar canal increases. Pollen germinates in the secretion-filled crater, and pollen tubes grow down the style between the cells of the transmitting tissue but do not enter the canal. They emerge at the entrance to the ovary cavity and grow over one or two narrow strips of ovarian transmitting tissue cells which are present throughout the length of the ovary close to the ovules. This ensures that tubes grow in close proximity to the micropyles.     

VANGUARD1 encodes a pectin methylesterase that enhances pollen tube growth in the Arabidopsis style and transmitting tract

In flowering plants, penetration of the pollen tube through stigma, style, and transmitting tract is essential for delivery of sperm nuclei to the egg cells embedded deeply within female tissues. Despite its importance in plant reproduction, little is known about the underlying molecular mechanisms that regulate the navigation of the pollen tube through the stigma, style, and transmitting tract. Here, we report the identification and characterization of an Arabidopsis thaliana gene, VANGUARD1 (VGD1) that encodes a pectin methylesterase (PME)-homologous protein of 595 amino acids and is required for enhancing the growth of pollen tubes in the style and transmitting tract tissues. VGD1 was expressed specifically in pollen grain and the pollen tube. The VGD1 protein was distributed throughout the pollen grain and pollen tube, including the plasma membrane and cell wall. Functional interruption of VGD1 reduced PME activity in the pollen to 82% of the wild type and greatly retarded the growth of the pollen tube in the style and transmitting tract, resulting in a significant reduction of male fertility. In addition, the vgd1 pollen tubes were unstable and burst more frequently when germinated and grown on in vitro culture medium, compared with wild-type pollen tubes. Our study suggests that the VGD1 product is required for growth of the pollen tube, possibly via modifying the cell wall and enhancing the interaction of the pollen tube with the female style and transmitting tract tissues.     

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.