Observations on the development of the foliar secretory cavities of Porophyllum lanceolatum (Asteraceae)

The lipophilic secretory cavities observed in the leaf of Porophyllum lanceolatum (Asteraceae) are scattered throughout the lamina and around its crenate margins. In the young leaf the cavities are initiated, and their development completed, while the surrounding tissues are still at early stages of differentiation. The cavity lumen has a lysigenous origin. Cell lysis, expansion of the developing leaf and, probably, the pressure exerted by the accumulation of secretory products, are believed to account for the gradual enlargement of the lumen. Concomitantly with ctll disintegration, which occurs throughout development, divisions take place in all cells of the gland. A mature cavity has a multilayered epithelium. Histochemical tests for RNA, proteins, phenolics and pectic polysaccharides revealed intense staining of the content of the epithelial cells in the early stages of cavity development, and a decrease in staining towards its maturity. Staining for lipids is intense in all developmental stages. Tests on the material observed in the lumen of mature cavities, show positive results for lipids, pectic polysaccharides and phenolics.     

Programmed cell death during pigment gland formation in Gossypium hirsutum leaves

Ultrastructural studies have shown that the formation of pigment glands in Gossypium hirsutum L. leaves is a lysigenous process, originating from a cluster of cells in the ground meristem. Various techniques were used here to investigate whether programmed cell death (PCD) plays a critical role in this developmental process. Nuclei of internal cells in the pigment gland‐forming tissue were TUNEL‐positive and DAPI‐negative, suggesting that DNA cleavage is an early event and complete DNA degradation is a late event. Smeared bands and a lack of laddering after gel electrophoresis indicate that DNA cleavage is random. Ultrastructurally, secretory cells in the pigment glands become distorted, nuclei are densely stained, and chromosomes become condensed until completely degraded at late stages. Vacuoles with electron‐dense bodies and membrane‐bound autophagosomes are seen in both secretory and sheath cells, suggesting that autophagy plays a key role in PCD during cytoplasm degradation. Buckling of cell walls, seen at early stages, later leads to a complete breakdown of the walls. Together, these results suggest that PCD plays a critical role in the lysigenous development of pigment glands in G. hirsutum leaves.     

Studies on the Structure and Development of Secretory Cavities in Poncirus Trifoliata

Light microscopical observation of thin sections revealed that the initials of secretory cavities in Poncirus trifoliata (L.) Raf. originated from parenchyma cells below the epidermis in early stages of development. The cavity lumen appeared in the center of the initials and gradually enlarged during subsequent development. Concurrently the ceils surrounding the central space differentiated into secretory cells and sheath cells. The developed cavities of fruit ,stem and leaf consisted of 2–5 layers of sheath cells and 2–3 layers of secretory cells surrounding a spherical space. The secretory cells lining the space were observed to remain intact throughout the plantt s life. On the basis of comparative studies with the aid of different kinds of fixatives, embedding media and sectionings,it was suggested that the ,manner of formation of the lacunao of secretory cavities in fruit peels of P. trifoliata, Citrus reticulata and C. sinensis were different. However,as seen in thin sections the secretory cavities of all the 3 species developed schizogenously. Our result with reference to views of other authers concluded the existance of a common schizogenous cavity formation in Rutaceae.     

臭椿茎中分泌道的发育及其组织化学研究

利用植物解剖学方法研究臭椿茎和叶柄中分泌道的结构、分布和发育过程.结果表明:臭椿茎和叶柄中的分泌道分布于髓的周缘,次生木质部中无分泌道.分泌道是由一层分泌细胞围绕分泌腔而构成,分泌细胞外有1～2层鞘细胞.分泌道以裂生方式形成,其发育过程可分为3个阶段:原始细胞阶段、形成阶段和成熟阶段.在原始细胞阶段,一群原始细胞具浓厚细胞质,细胞核清晰可见;形成阶段,原始细胞的中央细胞间细胞壁中层降解,细胞壁分离,形成腔隙,随着分泌细胞数量的增加,分泌腔体积扩大;成熟阶段的分泌道具有12～16个分泌细胞,1～2层鞘细胞,分泌腔直径为30～50μm.组织化学研究表明,分泌细胞及分泌道内含物中含大量的萜类、多糖和脂类物质.机械创伤能够诱导次生木质部中产生创伤分泌道.臭椿茎中的分泌道和创伤性分泌道在抵御生物和非生物胁迫中起重要作用.     

Oleoresin glands in copaíba (<Emphasis Type="Italic">Copaifera trapezifolia</Emphasis> Hayne: Leguminosae), a Brazilian rainforest tree

Although studies have addressed the chemical analysis and the biological activity of oleoresin in species of Copaifera, the cellular mechanisms of oleoresin production, storage, and release have rarely been investigated. This study detailed the distribution, ontogeny, and ultrastructure of secretory cavities and canals distributed in leaf and stem, respectively, of Copaifera trapezifolia, a Brazilian species included in a plant group of great economic interest. Axillary vegetative buds, leaflets, and portions of stem in primary and secondary growth were collected and processed in order to study the anatomy, histolocalization of substances, and ultrastructure. Secretory cavities are observed in the foliar blade and secretory canals in the petiolule and stem. They are made up of a uniseriate epithelium delimiting an isodiametric or elongated lumen. Biseriate epithelium is rarely observed and is a novelty for Leguminosae. Cavities and canals originate from ground meristem cells and the lumen is formed by schizogenesis. The content of the cavities and canals of both stem and leaf is oily and resinous, which suggests that the oleoresin could be extracted from the leaf instead of the stem. Phenolic compounds are also detected in the epithelial cell cytoplasm. Cavities and canals in the beginning of developmental stages have polarized epithelial cells. The cytoplasm is rich in smooth and rough endoplasmic reticula connected to vesicles or plastids. Smooth and rough endoplasmic reticulum and plastids were found to be predominant in the epithelial cells of the secretory cavities and canals of C. trapezifolia. Such features testify the quantities of oleoresin found in the lumen and phenolic compounds in the epithelial cell cytoplasm of these glands. Other studies employing techniques such as correlative light electron microscopy could show the vesicle traffic and the compartmentalization of the produced substances in such glands.     

Resin secretory canals in <Emphasis Type="Italic">Protium heptaphyllum</Emphasis> (Aubl.) Marchand. (Burseraceae): a tridimensional branched and anastomosed system

Protium heptaphyllum is a Burseraceae species known by the production of aromatic resin with medicinal, economic, and ecological values. Information on the development, architecture, and lifetime of the secretory system are crucial to understand the resin production and contribute to a more sustainable tapping regime. We investigated the histology and ultrastructure of the secretory canals under a developmental point of view. Stem samples were analyzed under light and transmission electron microscopy by conventional and cytochemical methods. Secretory canals, originated from procambium and cambium, occurred immersed in the primary and secondary phloem. Mature canals have a secretory epithelium and a wide lumen where the exudate is accumulated. A sheath of parenchyma cells with meristematic features surrounds the epithelium. The canals originate by schizogenesis and develop by schyzolysigenesis. Canals active in secretion occurred since the shoot apex and near the cambium. In the dilation zone of the secondary phloem, secretory canals exhibit sclerified epithelial and sheath cells and are inactive in secretion. Secreting epithelial cells have subcellular apparatus consistent with oleoresin, polysaccharides, and enzymes secretion. Pectinase and cellulase were cytochemically detected in developing canals and are involved in cell wall changes associated to canal growth and release of exudate. In P. heptaphyllum, the secretory system has a complex structure resultant from longitudinal growth, lateral ramification, and fusion of the adjacent canals, in addition to intrusive growth of both epithelial and sheath cells. Although some anatomical results are already known, ultrastructural data represent the novelty of this work. Our findings can contribute to the establishment of more efficient and sustainable techniques for resin extraction in this species.     

慈菇匍匐茎中分泌道的初步研究

慈茹匍蔔茎的分泌道是裂生的胞间道,分布于匍匐茎的基本组织中。单个分泌道原始细胞起始于离茎端约1毫米处的基本分生组织中,原始细胞经分裂形成5—7个上皮细胞包围着中央的裂生腔隙,成为管道系统。上皮细胞无鞘细胞包围。上皮细胞中高尔基体和内质网发达,并溢出小囊泡向着分泌道腔隙面壁的质膜附近迁移,乳汁中亦存在大量完整的小囊泡。上皮细胞和外围薄壁细胞之间的壁层具有大量胞间连丝,小囊泡和内质网的膜结构与胞间连丝末端相接,同时可见上皮细胞的质膜在数处反折内陷,形成袋状结构,在与上皮细胞相对的薄壁细胞内也有同样现象出现,袋状结构内含小形颗粒或囊泡,并在结构上显示出上皮细胞与相邻薄壁细胞间存在着活跃的物质交流。由此认为。代谢物质以整体小囊泡的形式经胞间连丝或内陷的质膜向分泌道迁移是物质运输和分泌的可能方式之一。在电镜下观察,液泡中的积聚物与乳汁十分相似,液泡可能是乳汁的贮存场所之一。     

中国芸香科植物叶分泌囊比较解剖学研究

利用整体透明、石腊和薄切片方法对芸香科22属,40种和2变种植物叶分泌囊的形态结构和分 布进行了比较研究。成熟分泌囊都由鞘细胞和一层上皮细胞围绕圆形腔隙构成,上皮细胞扁平,细胞壁 薄、完整,故分泌囊属裂生方式发生。鞘细胞1～5层,不同种类的层数有变化,个别种缺乏。内层鞘细 胞为扁平的薄壁细胞,外层的细胞壁较厚。分泌囊的形态结构、着生位置和分布密度等在不同属或不同 种间存在一定差异。根据分泌囊在叶中的分布位置和形态结构特点,可将其划分为:叶缘齿缝分泌囊, 叶肉分泌囊和两者混合型。叶肉分泌囊又可分海绵组织分泌囊和栅栏组织分泌囊。在此基础上对该科各类型分泌囊的形态演化关系以及各亚科或各属间的亲缘关系进行了探讨。     

Ultrastructure of the Resin Ducts of Mangifera indica L. (Anacardiaceae). 1. Differentiation and Senescence of the Shoot Ducts

A detailed electron microscope study has led to the conclusionthat the resin ducts of the shoot of Mangifera indica L. developlysigenously. This study has also established several characteristicswhich can serve as criteria for a clear distinction betweenschizogenous and lysigenous cavities. The main characteristicsof lysigenous cavities are: (1) The presence of disorganized cytoplasm in the duct cavity. (2) The presence of wall remains attached to the wall of livingepithelial cells facing the cavity. (3) The presence of specific intercellular spaces at the cellcorners facing the duct lumen. Duct development starts with the disintegration of a file ofcells forming an initial cavity. Later the cells lining thiscavity differentiate into cells secreting lipophilic compounds.As a result of growth and differentiation of the tissues aroundthe duct, its lumen becomes compressed and comes to resemblea branched narrow slit. Such a slit may wrongly be regardedas an initial stage of a schizogenous duct. Disintegration ofepithelial cells occurs throughout all stages of development.Neighbouring cells partly fill the space which is released bydisintegrating cells. At the end of the stage of secretion thecytoplasm of all epithelial cells darkens, preceding their disintegration.This darkening is a gradual process which begins in the vicinityof ribosomes. When all dark epithelial cells disintegrate thecavity widens and the neighbouring parenchyma cells substitutefor the secretory epithelium without undergoing any significantchange in their cytoplasm. Mangifera indica L., mango, resin ducts, ultrastructure     

New insights into the functional morphology of the male copulatory apparatus of bullid gastropods

In this study, semi-thin sections stained with histochemical techniques and transmission electron microscopy were used to obtain new data about the morphology and function of the male copulatory apparatus of the cephalaspidean gastropod Bulla striata. The apparatus comprises a vestibule, a penial papilla and a prostate consisting of a coiled unbranched tube ending in a blind caecum. The penial papilla and the coiled tubular prostate are enclosed by a muscular sheath, which is continuous with the muscular tissue of the vestibule. The epithelium lining the lumen of the vestibule is formed by ciliated and mucus-secreting cells. Two new types of subepithelial secretory cells were discovered in this region. The penial papilla is a muscular structure without secretory cells in the epithelium lining the narrow lumen. The tubule that constitutes the prostate possesses a muscular wall and can be divided in three distinct regions: a non-secretory duct connected to the penial papilla, a glandular region rich in large secretory cells and the terminal caecum containing just a few small secretory cells. In the terminal blind caecum, the muscular sheath is fused with the muscular wall of the tubular prostate. Large numbers of spermatozoa were found in the glandular region and in the terminal caecum of the prostate. A new functional mechanism is proposed to explain penial eversion during copulation. This differs from a previous hypothesis in two main aspects: (1) existence of a permanent penial papilla in mature animals acting as a functional penis and (2) functional role of vestibule during copulation, which everts and surrounds the penial papilla, while the latter protrudes outwards.     

Male-sterility of thermosensitive genic male-sterile rice is associated with premature programmed cell death of the tapetum

The tapetum plays a crucial role in pollen development. This secretory tissue produces numerous nutritive proteins necessary for pollen maturation. The tapetum, whose cells undergo programmed cell death (PCD), is completely diminished by the time the pollen is fully mature. Our previous studies on a thermosensitive genic male-sterile (TGMS) rice (Oryza sativa L.) suggested that male-sterility was due to failure in pollen development. In this paper we describe how further analysis of the TGMS rice revealed that male-sterility is associated with premature PCD of the tapetum. Cytological observations of TGMS rice anthers at various developmental stages indicated that PCD initiates at an early stage of pollen development and continues until the tapetal cells are completely degraded, resulting in pollen collapse. Transmission electron microscopy showed the morphologically distinct hallmarks of apoptosis, including cytoplasmic shrinkage, membrane blebbing, and vacuolation. Identification of DNA fragmentation using the TUNEL assay supports the hypothesis that premature PCD is associated with male-sterility in the rice. The tissue-specific feature of the thermosensitive genic male-sterile phenotype is discussed with regard to PCD during anther development.     

Structural and ultrastructural aspects of ontogenesis and differentiation of resin secretory cavities in Hymenaea stigonocarpa (Fabaceae‐Caesalpinioideae) leaves

Cell lysis in the formation of secretory cavities in plants has been questioned by some authors and considered as result of technical artifacts. To describe the formation of secretory resin cavities in Hymenaea stigonocarpa leaves, leaflet samples at different stages of differentiation were collected, fixed, and processed for light and electron microscopy as per usual methods. The initial cells of secretory resin cavities are protodermal and grow towards the mesophyll ground meristem; these cells then divide producing cell groups that are distinguished by the shape and arrangement of cytoplasm, and density. At the initial stages of differentiation of the secretory cavities, some central cells in these groups show dark cytoplasm and condensed nuclear chromatin. Later, there is cell wall loosening, tonoplast and plasmalemma rupture resulting in cell death. These cells, however, maintain organelle integrity until lysis, when the cell wall degrades and the plasmalemma ruptures, releasing protoplast residues, marked characteristics of programmed cell death. The secretory epithelium remains active until complete leaf expansion when the cavity is filled with resin and the secretory activity ceases. There are no wall residues between central cells in adult cavities. Our results demonstrate lysigeny and the importance of ontogenetic studies in determining the origin of secretory cavities.     

Secretory Cavity Development and Its Relationship with the Accumulation of Essential Oil in Fruits of Citrus medica L. var. sarcodactylis （Noot.） Swingle

The developmental types of secretory cavities in Citrus remain controversial. The relationship between secretory cavity development and the accumulation of essential oil in fruits of Citrus species is also unknown. In order to develop better insights into these problems, histological, histochemical, and cytochemical methods were used to investigate secretory cavity development and the accumulation of essential oll at different developmental stages of fruits of Citrus medica L. var. sarcodactylis （Noot.） Swingle. The results indicate that the secretory cavity of the variety seemed to originate from an epidermal cell and a subepldermal cell. These two cells underwent successive divisions, resulting In the formation of two parts： （Ⅰ） a conical cap; and （Ⅱ） a globular gland. The formation of the lumen was schlzolysigenous. Regular changes in the size of vacuoles and the accumulation of essential oil were revealed during the process of secretory cavity development. In addition, when fruits were a light yellow or golden color, the structure of secretory cavities was well developed and the content of essential oil in a single fruit reached a maximum. It would be most appropriate to collect the fruit as a medicinal material at this time.     

Early neural cell death: dying to become neurons

The importance of programmed cell death (PCD) during vertebrate development has been well established. During the development of the nervous system in particular, neurotrophic cell death in innervating neurons matches the number of neurons to the size of their target field. However, PCD also occurs during earlier stages of neural development, within populations of proliferating neural precursors and newly postmitotic neuroblasts, all of which are not yet fully differentiated. This review addresses early neural PCD, which is distinct from neurotrophic death in differentiated neurons. Although early neural PCD is observed in a range of organisms, from Caenorhabditis elegans to mouse, the role and the regulation of early neural PCD are not well understood. The regulation of early neural PCD can be inferred from the function of factors such as bone morphogenetic proteins (BMPs), Wnts, fibroblast growth factors (FGFs), and Sonic Hedgehog (Shh), which regulate both early neural development and PCD occurring in other developmental processes. Cell number control, removal of damaged or misspecified cells (spatially or temporally), and selection are the proposed roles early neural PCDs play during neural development. Data from developmental PCD in C. elegans and Drosophila provide insights into the possible signaling pathways integrating PCD with other processes during early neural development and the roles they might play.     

Lepidopteran larval midgut during prepupal instar: digestion or self-digestion?

Programmed cell death (PCD) is crucial in body restructuring during metamorphosis of holometabolous insects (those that have a pupal stage between the final larval and adult stages). Besides apoptosis, an increasing body of evidence indicates that in several insect species programmed autophagy also plays a key role in these developmental processes. We have recently characterized the midgut replacement process in Heliothis virescens larva, during the prepupal phase, responsible for the formation of a new pupal midgut. We found that the elimination of the old larval midgut epithelium is obtained by a combination of apoptotic and autophagic events. In particular, autophagic PCD completely digests decaying tissues, and provides nutrients that are rapidly absorbed by the newly formed epithelium, which is apparently functional at this early stage. The presence of both apoptosis and autophagy in the replacement of midgut cells in Lepidoptera offers the opportunity to investigate the functional peculiarities of these PCD modalities and if they share any molecular mechanism, which may account for possible cross-talk between them.     

A morphologic study of the ductus of the epididymis of Sus domesticus

The head, body, and tail regions of the epididymal duct (or caput, corpus, and cauda epididymis) in two healthy and sexually mature Sus domesticus males were examined by light microscopy and by scanning or transmission electron microscopy. The epididymal duct is lined with a pseudostratified epithelium with stereocilia and covered by a muscular-connective tissue sheath that is thickest in the tail region. Diameter of the epididymal duct and height of epididymal epithelium are maximal in the head region. Length of the sterocilia and spermatic density are higher in the head and body regions. Somatic cells are abundant in the tail region. The epididymal epithelium is made up of five cell types: basal cells, principal cells, clear cells, narrow cells, and basophilic cells. Abundant secretory units are observed in the supranuclear cytoplasm of columnar principal cells. Each mature secretory unit is constituted by electron-dense secretion granules covered by more than eight layers of cisternae of reticulum between which the mitochondria are intercalated. In the apical cytoplasm the isolated secretion granules become larger and less electron dense. The apical surface is covered by numerous sterocilia. Basal cells are pyramidal and less high than principal cells. The clear cells, arranged between the principal cells, are characterized by the presence of abundant vesicular elements and electron-lucid secretion granules, and by an apocrine secretory process. The narrow cells are characterized by their highly vacuolized cytoplasm. Intermediate cell typologies can be found among basal, principal, clear, and narrow cells, which could be four developmental stages of the same cell type. The basophilic cells are spheroidal and are found at different levels between the epithelial cells and in the connective tissue underlying the epithelium. © 1993 Wiley-Liss, Inc.     

Structure and development of the secretory cavities of Myrtus communis leaves

The structure and development of Myrtus communis L. secretory cavities has been studied in young and expanded leaves, using light and scanning electron microscope. Secretory cavities are continuously formed during leaf development, but in mature leaves the rhythm of their appearance shows steep decrease. Each secretory cavity is developed from a single epidermal cell, which undergoes a periclinal division followed by anticlinal and several oblique cell divisions. The lumen of the secretory cavity is initiated by cell wall separation, i.e., schizogenously. The secretory cells line the cavity, where the secreted material is collected. Secretory cavities are covered by modified epidermal cells, which do not seem to form any special aperture. Essential oils seem to be discharged after mechanical treatment of the leaf.     

Ultrastructural changes in the oviductal epithelium of Merino ewes during the estrous cycle

Isthmic and ampullary oviductal epithelia sampled from Merino ewes at days -1, 1, 3, and 10 of the estrous cycle (estrus = day 0) were studied by scanning and transmission electron microscopy after fixation by vascular perfusion. Secretory cells, ciliated cells, and lymphocytelike basal cells were observed in both isthmic and ampullary epithelium at all stages of the estrous cycle studied and their ultrastructural features were analyzed. Synthesis of lamellated secretory granules occurred in the ampullary secretory cells during the follicular and early luteal phases, and their contents were released by exocytosis into the oviductal lumen during the luteal phase. Granule release was associated with nucleated apical protrusion of these cells into the oviductal lumen. No such secretory activity was displayed by isthmic secretory cells even though a few cells contained nonlamellated granules. Apocrine release of apical vesicles and accompanying cytoplasmic material from apical protrusions of ciliated cells occurred in the isthmus around estrus but not in the ampulla. This unexpected feature has not previously been reported in any other mammal. Dendritic basal cells were distinguished in the lower part of the epithelium by their heterochromatic nuclei, electron-lucent cytoplasm, and lack of attachment zones. No migration of basal cells was observed, and their ultrastructural features were similar in the ampulla and isthmus and at all stages of the estrous cycle examined. The function of these lymphocytelike cells in the epithelium is uncertain, but the presence of phagocytic bodies and lysosomes in 20% of them may indicate a phagocytic role.     

生姜根茎的发育过程及分泌腔的超微结构

为了解生姜(Zingiber officinale Roscoe)根茎的发育过程,在光学显微镜和电子显微镜下对不同发育时期的生姜进行显微和超微结构观察,并对分泌腔的发生发育过程进行了研究。结果表明,幼嫩期的生姜,表皮以内的基本组织可大致分为皮层、拟内皮层和中柱。次生加厚分生组织起源于中柱外侧一些细胞,细胞分裂和体积增大促使生姜发育。薄壁细胞内有大量的淀粉粒且其数量、形状和大小因发育时期而不同。分泌腔广布于生姜中,其发育过程可分为3个阶段:分泌腔原始细胞团形成、分泌腔的发生和成熟分泌腔形成。生姜精油主要在线粒体、质体和细胞质中合成。本研究为生姜药用资源的开发利用提供了理论依据。