Ultrastructure of the Resin Ducts of Mangifera indica L. (Anacardiaceae). 3. Secretion of the Protein-polysaccharide Mucilage in the Fruit

Mango fruit ducts secrete a protein-carbohydrate mucilage inaddition to lipophilic material. This mucilage is secreted inspecial duct regions. Loops of ER elements seem to delimit cytoplasmicportions rich in ribosomes forming pseudo-vacuoles which eventuallybecome bound by a single membrane of ER origin. It is suggestedthat the protein is produced and accumulates in the pseudo-vacuoleswhich become storage bodies. Carbohydrates are added to thecontent of these bodies by Golgi vesicles. The cytoplasm becomesosmiophilic and contracts before disintegration, and the mucilagepasses into the space between plasmalemma and cell wall. Afterthe cell breaks down the mucilage is released into the ductcavity. Mangifera indica L., mango, Anacardiaceae, resin ducts, secretion, mucilage, ultrastructure     

Ultrastructure of Resin Ducts in Pinus halepensis Development, Possible Sites of Resin Synthesis, and Mode of its Elimination from the Protoplast

Development of the resin duct cavity, sites of resin synthesisin the epithelial cells and elimination of resin from the protoplastwere studied in roots of young Pinus halepensis seedlings. Itis suggested that the Golgi bodies are involved in dissolutionof the middle lamella in the region of the future duct cavityby secretion of lytic enzymes into the cell walls. In earlystages of duct development osmiophilic droplets were observedin plastids, periplastidal and cytoplasmic ER, Golgi vesicles,mitochondria, nuclear envelope and in the cytoplasm. In thelatter they were often observed to be surrounded by a membrane.Electron micrographs suggested that elimination of resin dropletsfrom the protoplast occurs by their becoming surrounded by plasmalemmainvaginations.     

Resin Ducts in the Mango Fruit: A Defence System

The fruit of the mango (Mangifera indica L.) is characterizedby resin ducts in its exocarp. There is a significant correlationbetween various characters of these resin ducts and the resistanceof the fruit to the Mediterranean fruit fly (Ceratitis capitataL.). The mean number of ducts which are crossed by a randomline in a transverse section of the exocarp is greater thanone in the resistant varieties and less than one in the sensitivevarieties. The hypothesis that the duct system renders protectionto the fruit is consistent with these observations.     

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     

Ultrastructure of Gum-resin Ducts in Cashew (Anacardium occidentale)

In Anacardium occidentale L., the gum-resin ducts in the primaryphloem of the stem develop schizogenously. Appearance of anintercellular space amongst the densely stained cells signalsthe initiation of a duct. During this process, the middle lamella,appears in places, as an electron-opaque area. The epitheialcells bordering the duct are oval and have convex inner tangentialwalls which are without any plasmodesmata, although they areabundant on radial and outer tangential walls. The cytoplasmof the epitheial cells is rich in rough endoplasmic reticulum(ER), free ribosomes, polysomes, mitochondria with swollen cristae,plastids with occasional osmiophilic inclusions, dictyosomesand vesicles. Osmiophilic material has been observed in thedilation of the cisternae of dictyosomes and also in vesicles.Sometimes, the osmiophilic material aggregates and forms largemembrane-bound globules. The globules fuse with the plasmalemmaat the inner tangential wall, and presumably the contents aredeposited in the space between the protoplast and the wall.This material passes through the loose matrix of the wall intothe duct. Some of the epitheial cells of the mature duct show‘dark’ cytoplasm, degraded organelles and occasionallyhigh vacuolation; ultimately they are lysed and their remainscollect in the duct. Anacardium occidentale L., cashew, gum-resin ducts, epithlial cell, dictyosome, osmiophilic material, ultrastructure     

Development and Structure of Primary Secretory Ducts in the Stem of Commiphora wightii (Burseraceae)

Development of gum-resin ducts, sites of resin synthesis inthe epithelial cells and elimination of resin from the protoplasthave been studied in the stem of Commiphora wightii. Formationof an intercellular space amongst a group of densely stainedprocambial cells signals the initiation of a duct. It widensby anticlinal divisions of the epithelial cells and also bytheir further separation along the radial walls. The numerousplastids with varying morphological shapes have an electrondense matrix. Starch granules present in the amyloplasts showevidences of exocorrosion. Mitochondria in the epithelial cellsof developing and mature ducts have well developed, swollencristae. Osmiophilic material originates in association withthe golgi-derived vesicles at its maturing face. It is alsoobserved in close association with plastids, mitochondria andvacuoles, thereby plausibly involving them in the process ofresin formation. The resinous material is eliminated from thecytoplasm by vesicles enveloped by plasmalemma prior to theirdischarge into the apoplast. Myelin-like multilamellate structuresobserved along the inner tangential wall may aid in the secretionof resin across the wall. Commiphora wightii, primary secretory ducts, epithelial cells, ultrastructure, gum-resin secretion     

Studies on the Resin Glands of Azadirachta indica A. Juss. (Meliaceae)

The leafy shoots of Azadirachta indica have numerous, yellowresin glands, composed of a short stalk and sub-glandular tissuebeneath an epithelium-like 1-2-layered secretory tissue. Thefoot arises from the epidermis. The resin glands are derivedfrom a single papillate epidermal cell which functions as aresin gland initial. Histochemical localization using fluorescencemicroscopy confirmed the resinous nature of the secretion. Thegeneral structure of the glands shows similarity to extra-floralnectaries. Reports in the literature on the occurrence of extrafloralnectaries in Meliaceae should be confirmed by analysis of thesecretions if they are to be accepted. Azadirachta indica, resin glands, ontogeny, structure, secretion     

Intracellular Transport and Elimination of Resin from Epithelial Duct-cells of Pinus halepensis

The ultrastructure of the resin secreting cells of root ductsof young Pinus halepensis seedlings was studied. It is suggestedthat the endoplasmic reticulum (ER) in addition to taking partin resin synthesis also plays a role in transporting the resinfrom the plastids, mitochondria and nuclear envelope to theplasmalemma. By fusing with the plasmalemma the ER releasesthe resin to the outside of the protoplast. The resin producedin the ground cytoplasm and by the Golgi apparatus seems tobe eliminated by plasmalemma invaginations. Pinus halepensis, resin secretion, root ducts, endoplasmic reticulum     

Distribution, Development and Structure of Resin Ducts in Guayule (Parthenium argentatum Gray)

The distribution, development and structure of resin ducts inguayule (Parthenium argentatum Gray), the second best sourceof natural rubber, have been studied. Resin ducts are widelydistributed in stem, root, leaf, petiole and peduncle. The ductsin the primary tissues are initiated schizogenously and theirfurther development is schizolysigenous. The ducts in the cortexof the root do not have a well-defined epithelium. Ducts developedfrom the vascular cambium are initiated and develop schizogenously.Both resin and rubber are produced in the epithelial cells ofresin ducts. While resin is secreted into the duct lumen, rubberis stored within these cells. Epithelial cells store more thanneighbouring parenchyma cells. Guayule, rubber, resin, ducts, epithelial cells     

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     

Biosynthesis of Resin Terpenes in Leaves and Glandular Hairs of Newcastelia viscida

Label from ¹⁴CO₂ and [2-¹⁴C]mevalonic acid was incorporatedinto resin components of Newcastelia viscida. About 25% of thelabel from [2-¹⁴C]MVA was incorporated into resin componentsafter 4 h. Approximately 80% of the label in the resin was ina TLC band coinciding with the major terpenoid components, with60% associated with the major tricyclic diterpene, a pimaradienewhich contributes 15% to the leaf resin dry weight. Experimentswith detached trichomes showed about 0?01% incorporation oflabel from [2-¹⁴C]MVA into pimaradiene, with most of the [abelbeing associated with ß-sitosterol. It is proposedthat the glandular hairs are the sites of terpene resin synthesis,as well as secretion, in this species.     

Development, Histochemistry and Ultrastructure of Gum-resin Ducts in Commiphora mukul Engl.

Gum-resin ducts are present in the primary and secondary phloemof Commiphora mukul Engl. The important gum-resin, known commerciallyas ‘guggul’, is secreted and collected in ductswhich develop schizogenously. The duct initials have dense cytoplasm,large nuclei, increased cytoplasmic RNA and proteins. The lumenof newly-formed ducts widens accompanied by anticlinal divisionsand subsequent tangential elongation of epithelial cells. Histochemicaltests reveal that the epithelial cells have apparently largeamounts of proteins, cytoplasmic RNA, and DNA in the nucleus.Lipid globules are also present in these cells. Epithelial cellwalls in contact with the duct are thin and of a loose fibrillarmesh. Microtubules, randomly oriented in the epithelial cellsare always parallel and adjacent to the wall. The cytoplasmis rich in ribosomes, endoplasmic reticulum, mitochondria, plastidsand vacuoles containing osmiophilic substances. At the peripheralregion of the duct, electron-transparent bodies containing densely-stainedmaterial are present close to the tangential wall.     

Resin and the Resistance of Conifers to Fomes annosus

Roots of young trees of different conifer species, Scots pine,Corsican pine, Sitka spruce, and Douglas fir were inoculatedwith Fomes annosus. In the pines, infection was negligible butin the other genera the central wood was extensively invaded.The process of infection was studied further in Sitka spruceby means of a root-severing technique in which an inoculum blockwas forced between the cut ends of a root. In most trees a centralrot developed which in some extended up into the butt: the meanextent of growth recorded was 30 cm in 14 months. In the severedroot portions infection also occurred but F. annosus was subsequentlyreplaced to a considerable extent by other micro-organisms,particularly in trees growing on a peat soil. A similar centralrot developed after inoculations of Norway spruce. The resistance of pine sapwood and the outer wood of spruceand Douglas fir can be explained at least partially by the structureand viability of the resin duct system. Larch, Douglas fir,spruce, and pine form a series showing increasing complexityand activity of the resin system. In addition, studies carriedout on the resin yields of pines growing under different conditionsshowed that the resistance of a tree to F. annosus is correlatedwith its ability to mobilize resin. Site factors, forest management,host age vigour, genetic constitution, and past history mayall influence resin mobilization.     

欧洲赤松树脂道上皮细胞树脂分泌方式研究(英)

利用高压冷冻和冷冻替代技术对欧洲赤松（PinussylvestrisCarr．）茎皮层成熟树脂道上皮细胞的超微结构进行研究,揭示出一种全新的树脂分泌方式。其分泌过程为：一些含有水解酶的高尔基小泡,转移至质膜周围并释放水解酶,从而将质膜溶解形成分泌通道,树脂由此迅速转移至质膜外,然后,通过高尔基小泡相互融合形成新膜片段的方式来修补破损的质膜。     

An Alternative Mode of Elimination of Resin from Epithelial Cells of Resin Ducts in Pinus sylvestris

The fine structure of resin secreting cells of the cortical resin ducts in stem of Pinus sylvestris Carr. was studied with the help of high pressure freezing and freeze-substitution techniques. An unprecedented mode of resin elimination was observed. It seems that the hydrolase-contained Golgi vesicles take part in the dissolution of plasmalemma, and a passage is formed, through which resin material may quickly pass outside of the protoplast. Then, the ruptured plasmalemma was repaired by some vesicles, possibly derived from Golgi bodies.     

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     

Gland Cells in Resin Canal Epithelia in Guayule (Parthenium argentatum) in Relation to Resin and Rubber Production

Schizogenous resin canals develop in the pith and cortex ofthe primary stem tissue in guayule (Parthenium argentatum Gray).In secondary tissue concentric rings of resin canals are producedfrom derivatives of the vascular cambium. Both resin and rubberaccumulate in the epithelial cells of the canals. These havethe characteristics of gland cells. Resin is secreted into thecanals and rubber accumulates in the surrounding parenchymacells as well as the gland cells, especially in winter. Younggland cells contain modified plastids and smooth tubular endoplasmicreticulum. These organelles probably accommodate the compartmentalizedsteps of the isoprenoid biosynthetic pathway leading to theproduction of isopentenyl pyrophosphate. As these ultrastructuralcharacteristics only exist in young gland cells of the currentseason's growth they seem to be the sole source of the precursorsfor both resin and rubber formation. Parthenium argentatum, guayule, resin canals, gland cells, plastids, smooth endoplasmic reticulum, rubber, resin, epithelial cells, ultrastructure     

Intracellular localization of capsaicin and its analogues, capsaicinoid, in Capsicum fruit 1. Microscopic investigation of the structure of the placenta of Capsicum annuum var. annuum cv. Karayatsubusa

Transverse sections of the placenta of hot pepper, Capsicumannuum var. annuum cv. Karayatsubusa, at different stages afterflowering were examined microscopically. Examination of thecellular structure of the placenta using a light microscoperevealed that some morphological changes took place mainly inthe epidermal tissue of the placenta during maturation. Elongationof the epidermal cells and many osmiophilic granules were recognizedin the epidermal cells of the placenta in which capsaicinoidwas being formed and actively accumulated. Moreover, a granule-likestructure having an absorption at 280 nm was also recognizedby ultraviolet microscopy around the same region where the osmiophilicgranules were observed. By electron microscopy, many electron-densegranules stained with glutaraldehyde and osmium tetroxide wereobserved both in the small vesicles and vacuoles of epidermalcells of the placenta. The electron-dense granules varied insize from smaller than 1 µm to larger than 2 µmin diameter. They were thought to be capsaicinoid and were observedonly in the epidermal cells. Therefore, the epidermal tissueappeared to be the site of capsaicinoid accumulation. ¹Formation and metabolism of pungent principle of Capsicum fruits.Part V. (Received December 27, 1979; )     

Development, Ultrastructure and Secretion of Gum Ducts in Lannea coromandelica (Houtt.) Merrill (Anacardiaceae)

In Lannea coromandelica (Houtt.) Merrill, the gum ducts in theprimary phloem of the stem initiate and develop schizogenously.Formation of an intercellular space amongst a group of denselystained phloem procambial cells signals the initiation of aduct. Initiation of a duct starts by dissolution of the middlelamella of the walls. It widens by separation of cells alongthe radial walls by swelling and dissolution of the middle lamella.During separation of radial walls dictyosomes and paramuralbodies are observed in the peripheral cytoplasm at the siteof dissolution. Plasmodesmata occur in the radial and innertangential walls of epithelial cells of developing gum ducts.The epithelial cells have a dense cytoplasm and contain roughendoplasmic reticulum, ribosomes, polysomes, mitochondria withswollen cristae, plastids with poorly developed membranes, dictyosomesand vesicles. Dictyosomes and rough endoplasmic reticulum seemto be involved in the secretion of the gum. The polysaccharidegum constituents apparently originate from the outer wall layersof the epithelial cells. Following gum secretion, the epithelialcells degenerate. Lannea coromandelica (Houtt.) Merrill, Anacardiaceae, gum ducts, ultrastructure, gum secretion     

Aspects of the Differentiation of the Egg of the Moss Physcomitrium coorgense Broth

Oogenesis in Physcomitrium coorgense follows the course seenin lower archegoniates generally. However no evidence was foundof cytoplasmic autophagy, or, during maturation of the egg,of nucleo-cytoplasmic interaction of the kind reported in liverwortsand ferns. The internal lamellar system of the plastids dedifferentiatesalmost entirely, and there is a corresponding increase in thefrequency of osmiophilic droplets. Starch also disappears, andsimultaneously large quantities of mucilage appear in the cytoplasm.The mucilage is secreted into the venter of the archegoniumand envelopes the egg. The egg lacks a special osmiophilic membrane.