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.     

Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower

Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration.     

Structure and Development of Stigmatic Branches and Style and Their Relation to Pollen Tube Growth in Wheat

The style of wheat divides into 2 branches, separated from its base and covered with a large number of slender stigmatic branches. The stigma is of dry type. The style is solid. There is no transmitting tissue differentiated in the style. Young stylar cells appear polygonal in transverse sections and elongated in longitudinal sections with an increase in length of the cells from periphery towards center. In transverse sections, mature stylar cells look extremely irregular. They are contorted and mosaicked with one another. During their development, stylar cells elongated vigorously with intrusive growth. The wall of stylar cells is thin, except at the corners where cells connect, that slight thickening of the cell wall occurs. Stylar cells start vacuolation at the earlier stages and gradually become highly vacuolated, but still remain rich in organelles, such as mitochondria, endoplasmic reticulum, dictyosomes and chloroplasts, the amount of which varied with the development stages of the style. Stigmatic branches are differentiated from the stylar epidermal cells, composed of 4 files of cells which link end to end with one another. Not long before anthesis, wall material in the intercellular corners becomes loose and porous. After pollination, pollen tubes grow along the intercellular spaces among the 4 files of cells in the stigmatic branches and then enter the style. Pollen tubes may pass through any intercellular corner throughout the 2 branches of the style, except for the lateral-outer portion which is composed of larger stylar cells. Eventually, pollen tubes enter the ovary.     

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     

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。     

Heterostyly inPrimula. 1. Fine-structural and cytochemical features of the stigma and style inPrimula vulgaris huds

Summary The stigmas of the heterostylous genusPrimula are of the dry type without a free-flowing surface secretion. The papillae of the stigma surface cells of the two morphs, in pin (stigma exserted) and thrum (stamens exserted), bear a thin proteinaceous surface pellicle, overlying a discontinuous cuticle. The vacuoles of the papillate cells contain tannins, and tannin cells extend in files through the stigma heads and form a loose sheath surrounding the pollen-tube transmitting tract in the styles. The cells of the transmitting tissue in the stigma heads have a normal complement of organelles, and abundant ribosomal endoplasmic reticulum. The intercellular spaces contain an internal secretion which reacts cytochemically for both carbohydrate and protein. The transmitting tract in the styles forms a central core surrounded by several vascular strands. The cells are elongated, and the intercellular spaces here also have a carbohydrate-protein content. In a compatible pollination, thrum pollen tubes enter the stigma by penetrating the cuticle at the tip or on the flank of the pin papilla. Pin tubes on the thrum stigma enter between adjacent papillae, penetrating the thin cuticle at the base. The tubes grow through the transmitting tracts in the intercellular material.     

Reproductive biology of Nymphaea capensis Thunb. var. zanxibariensis (Casp.) Verdc. (Nymphaeaceae)

Anthesis in Nymphaea capensis var. zanzibariensis is diurnal with flowers opening and closing for three consecutive days. On the first day of anthesis, the stigmatic papillae secrete fluid and the outermost anthers are dehiscent. On the second day of anthesis the stamens form a cone above the dry stigmatic cup. The middle stamens open and turn outward. On the third day of flowering, all the stamens open and the dry stigmatic cup is exposed. The flowers are homogamous and not protogynous as the other Nymphaea. The gynoecium of the self-compatible N. capensis var. zanzibariensis , is characterized by a wet papillate stigma, a short hollow style, and secretory cells on the ventral surface of the ovary. The pollen is released on the receptive stigma. Following initial growth in intercellular spaces in the transmitting tract of the stigma, pollen tubes travel through the stylar canal and into the ovary.     

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。     

Pollen tube growth and the pollen‐tube pathway of Nymphaea odorata (Nymphaeaceae)

An important aspect of the evolution of carpel closure, or angiospermy, is the relationship between pollen tube growth patterns and internalization of the pollen‐tube pathway. True carpel closure, involving postgenital fusion of inner carpel margins, is inferred to have arisen once within the ancient order Nymphaeales, in the common ancestor of Nymphaeaceae. We studied pollen tube development, from pollination to fertilization, in a natural population of Nymphaea odorata, using hand pollinations and timed flower collections. Pollen germinates in stigmatic secretions within 15 min and pollen tubes enter subdermal transmitting tissue within an hour, following wide intercellular spaces towards the zone of postgenital fusion. At the zone of fusion they turn downwards to grow in narrow spaces between interlocked cells and then wander freely to ovules within ovarian secretions. The pollen‐tube pathway is 2–6 mm long and upper ovules are first penetrated 2.5 h after pollination. Pollen tubes grow at rates of approximately 1 mm/h whether in stigmatic fluid, transmitting tissues or ovarian secretions. Pollen‐tube pathways are structurally diverse across Nymphaeales, yet their pollen tubes have similar morphologies and rapid growth rates. This pattern suggests pollen tube growth innovations preceded and were essential for the evolution of complete carpel closure. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 581–593.     

Sexual reproduction in the cork oak (Quercus suber L.). I. The progamic phase

 Cork oak (Quercus suber L.) is a monoecious wind-pollinated species with a protandrous system to ensure cross-pollination. To the best of our knowledge, this report provides the first insight into the sexual reproduction cycle in this species. The cork oak flowering season extends from April until the end of May. Our results show that, at anthesis, the pistillate flower is not completely formed and ovules are just starting to develop. Pollen reaching the dry stigmatic surface adheres to the receptive cells, germinates and penetrates the epidermis in aproximately 24 h, and grows through the intercellular spaces of a solid transmitting tissue. In cross-pollination, a sequential arrest of pollen tubes was observed along the style, providing preliminary evidence for a pollen tube competition mechanism. As a consequence, few pollen tubes reach the basal portion of the style. Furthermore, pollen tube growth is a discontinuous process since tubes are arrested in the basal portion of the style about 10–12 days after pollination. While tubes are latent, the ovarian loculus starts to develop from an emerging mass of sporogeneous cells which later will differentiate into the placenta and ovules. One and a half months after pollination ovules complete their differentiation, tubes resume growth and fertilisation occurs. Ovular abortion is frequent at this stage, and only one ovule will successfully mature during autumn into a monospermic seed. Received: 23 July 1998 / Revision accepted: 2 November 1998     

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 and style anatomy and ultrastructure in Italian Oxalis pes-caprae L. and their possible connection with self-incompatibility

The South-African Oxalis pes-caprae with trimorphic flowers is naturalised in many Mediterranean countries. In Italy only short-styled (S) populations are known for certain and the plant is believed to reproduce only asexually, due to self- and intramorph-incompatibility. This study aims to clarify anatomical, biochemical and ultrastructural features of the stigma and style of an Italian S population, also to define their possible role in incompatibility. Additional observations were also carried out on other Italian population and on short-, long- (L) and mid-styled (M) flowers from plants of South African origin. Morphological and biochemical features of flowers collected in different phenological stages during the whole flowering season were observed both under LM and TEM. In S flowers, three different zones could be distinguished in each stigma-style complex: zone I (stigmatic), zone II (substigmatic), zone III (stylar). The main differences concern the transmitting tissue: in zones I and III this is composed of loosely arranged cells with thick walls, with an abundant soft matrix which at anthesis is rich in mucopolysaccharides and lacks pectins. In zone II, it is more compact, with a less abundant wall matrix, at anthesis containing both mucopolysaccharides and pectins. In S flowers, subjected to illegitimate pollination, many pollen tubes penetrate the stigmatic papillae but apparently are arrested in zone II; only few—and mostly at the end of flowering period—succeed reaching zone III, where they encounter no further resistance to growth. Differently, after legitimate pollinations, pollen tubes succeed in crossing transmitting tissue of zone II, where cell walls of cells lying close to pollen tubes show a considerably reduced pectin content. In L and M flowers of South African origin, no peculiar transmitting tissue could be noticed in the substigmatic zone. In such flowers, pollen tubes seemingly grow easily from stigma to style both after legitimate and illegitimate pollinations. Results suggest that in S flowers the rigid transmitting tissue in zone II acts as a mechanical barrier for illegitimate pollen tubes, as the spaces between cells are narrower than the tube diameter and pectins maintain the rigidity of the cell walls, preventing cells from separating from one another. This obstacle can be overcome by legitimate pollen tubes, which make their way between cells, possibly releasing or activating specific pectinases. However, the blocking of illegitimate tubes is not absolute: a few of such tubes grow beyond zone II and reach the ovules, so that occasional fertilisation and embryo formation can be observed. In M and L flowers, different self-incompatibility mechanisms can be hypothesised.     

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.     

The Structure and Cytochemistry of the Pistil of Hypericum calycinum: The Stigma

The pistil of Hypericum calycinum has a pentacarpellary, syncarpousovary with five slender styles, each terminating in a smallstigma. The stigma is dry and papillate with a thin lining ofpellicle. The cuticle is thin and continuous around the papillae.A large vacuole filled with tannins occupies the major partof the papillae and the cytoplasm forms a thin lining aroundthe vacuole. The cell wall of the mature papillae show two distinctlayers - an outer layer of loosely woven fibrils and an innerdenser layer with compact fibrils. A large number of small lipoidalbodies accumulate just below the cuticle. The papillae havefewer organelles than those typical of glandular cells. Dictyosomesobserved occasionally are without associated vesicles. The cytoplasmis rich in ribosomes. The basal portions of the papillae mergeinto the transmitting tissue made up of loosely arranged cells.The intercellular matrix of the transmitting tissue is richin lipids. Pollen grains are deposited between the papillae.Upon pollen germination, pollen tubes enter the stigma throughthe interstices between the papillae Hypericum calycinum, cytochemistry, pistil, pollen-pistil interaction, stigma, ultrastructure     

Pollen and pistil in the progamic phase

The progamic phase, the period of pollen tube growth through the pistil, is a period of specific interactions between the male gametophyte and the pistil. Understanding of pollen germination and pollen tube growth are relevant for the study of pollen-pistil interactions and for understanding the function of components specifically accumulated in the transmitting tissue cell walls and intercellular matrix that may interact with pollen tubes. Received: 18 January 2001 / Accepted: 19 June 2001     

陆地棉雌蕊的花粉管生长途径中钙分布的超微细胞化学定位

用焦锑酸盐沉淀法对陆地棉(Gossypium hirsutum L.)授粉前后的柱头、花柱、珠孔与珠心组织中的钙进行了超微细胞化学定位。X射线波谱与能谱分析证明所定位的沉淀确系焦锑酸钙。观察结果表明:在整个花粉管生长途径中的雌蕊组织,钙分布均较其它相邻组织密集;钙主要分布在细胞壁与胞间基质等质外体系统中。在雌蕊中生长的花粉管,其尖端细胞器区也有丰富的钙。     

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.     

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.     

Structural and Cytochemical Characteristics of the Stigma and Style in Vitis vinifera L. var. Sangiovese (Vitaceae)

Studies were carried out on structural and cytochemical aspectsof the stigma and style ofVitis vinifera . The stigma is ofthe wet papillate type with a continuous cuticle and pellicle.During the development of the papillae, the cell walls increasein thickness and produce a secretion product constituted oflipids that pass through the wall forming the exudate. The styleis solid with a central core of transmitting tissue which hasconspicuous intercellular spaces that increase remarkably fromthe periphery to the centre where the cuticle is present. Theintercellular spaces, where the pollen tubes grow, contain amatrix that includes polysaccharides, pectic substances andscattered areas of lipidic nature. Cytochemistry; stigma; style; ultrastructure; Vitis vinifera     

Stigmatic and stylar incompatibility in Prunus avium L.: Morphological and ultrastructural aspects

Abstract

Stigmatic and stylar structures of-sweet cherry (Prunus avium L.) «Malizia» were examined with light and electron microscopes (S.E.M. and T.E.M.).

It was demonstrated that the transmitting tissue, situated in the central portion of the style, extends below the stigmatic papillae and secretes an electrondense material accumulating in the intercellular spaces. Pollen tubes which germinated on the stigma, reached the ovules passing through this substance which facilitates their passage while trophic relations are established.

Some ultrastructural aspects of the pollen tubes observed inside the style were examined and discussed in relation to the phenomenon of self-incompatibility.