Mechanism of Pollination in Gladiolus: Roles of the Stigma and Pollen-tube Guide

Gladiolus has a dry type of stigma. Compatible pollen grainsalight and germinate on the receptive surface of the papillae,penetrate the cuticle and grow towards the style through a sub-cuticularpollen-tube guide of mucilage. This is secreted from epidermalcells of the stylodium and style canal. The cuticle, which coversthe pollen tube guide mucilage, is continuous through the stylecanal to the ovary. The wet stigma of Lilium also has cuticulartissue running through the style canal, covering the mucilage.     

Cytochemistry and Ultrastructure of the Mucilage Secreting Trichomes of Nymphoides peltata (Menyanthaceae)

The young developing leaves in the buds of Nymphoides peltataare covered by a hyaline mucilage. The mucilage contains freesugars, polysaccharides and proteins. The most abundant monosaccharidesof the polysaccharide fraction are arabinose and galactose.Therefore, the major component of the mucilage is probably anarabinogalactan or arabinogalactan protein. The mucilage issecreted by glandular trichomes. It is suggested that both thepolysaccharide and the protein fraction of the mucilage aretransported to the plasmamembrane by vesicles of the Golgi apparatus(granulocrine secretion). Secretory proteins are probably synthesizedin the rough endoplasmic reticulum and transported to the Golgiapparatus via transition vesicles. Polysaccharides were localizedin Golgi vesicles by ultracytochemistry. After exocytosis thesecretion is accumulated between the cell wall and the cuticle;this leads to the formation of protrusions on the outer wallsof the glandular cells. Finally, the cuticle is ruptured andthe secretion is released. The biological function of the mucilageis not known. Possibly the mucilage is a lubricant or a protectionfrom desiccation. Nymphoides peltata (S.G. Gmel.) O. Ktz., trichomes, mucilage secretion, cytochemistry, ultrastructure     

Cytochemical and Morphological Evidence for the Involvement of the Plasma Membrane and Plastids in Mucilage Secretion in Aloe arborescens

Most of the volume of Aloe arborescens leaves (volumetric density= 0.68±0.08) is occupied by a mucilage tissue. The mucilagesof Aloe species are glucomannans of great medical and pharmaceuticalimportance. An electron microscopical and histochemical studywas carried out, following the development of the tissue andsecretion processes. In contrast to other reports on polysaccharide secretion inplants, no observable activity was found in the Golgi apparatus.In the young stages of leaf development, positive histochemicalstaining for polysaccharides and structural changes were foundmainly in the plastids. In the mature leaves the mucilage cellsremain alive and intact and secretory activity appears to becentered in the plasma membrane. Aloe arborescens, cytochemistry, mucilage, plasma membrane, plastids, secretion     

The Pollen Tube Pathway in the Pistil of Lycopersicon peruvianum

The pollen tube pathway has been studied in unpollinated andpollinated pistils of Lycopersicon peruvianum using histochemicalstains for detection of proteins, lipids and arabinogalactansby bright-field microscopy, and decolourized aniline blue fordetection of pollen tubes by epifluoresence microscopy. Thepollen tube pathway is a continuous tract of mucilage from thestigma surface to the ovule micropyles, and is associated witha continuous tract of specialized, protein-rich transmittingcells comprising the stigmatic papillae, vertical files of stylartransmitting cells and the placental epithelium within the ovary.The superficial exudate of the stigma is hydrophobic and richin lipids. The mucilage of the style and ovary is hydrophilicand rich in arabinogalactans but low in proteins. Pollen tubesgrow between cells through the mucilage of the stigma and stylartransmitting tract, and across the surface of the placenta inthe ovarian mucilage. The structure of the junction of the stylartransmitting tract with the top of the ovary placenta assistseffective distribution of pollen tubes within the ovary. Lycopersicon, solanaceae, fertilization, pistil, pollen tube, pollination     

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     

Chemical Composition of Viscin Mucilage from Three Mistletoe Species--A comparison

The viscin of mistletoes is a unique tissue which serves toprovide strong adherence of the seed of the parasite to thehost branch. The viscin mucilage of three species, Phoradendroncalifornicum and Arceuthobium americanum (Viscaceae) and Phthirusapyrifolia (Loranthaceae), was analysed. The major componentof the mucilage of Pho. californicum and A. americanum was polysaccharidic;of this, neutral sugars comprised the largest portion, but substantialamounts of uronic acids and proteins were also present. Xyloseand arabinose were the most abundant of the neutral sugars,and analysis showed glycine to be the most abundant amino acidas well as the presence of higher-than-average amounts of histidine.In contrast, in the mucilage of Pht. pyrifolia glucose was themost abundant neutral sugar and the protein content was substantiallyhigher. Based on the differences in composition observed amongthe different species the future use of viscin components astaxonomic markers is suggested. Viscin mucilage, mistletoes, Arceuthobium americanum, Phthirusa pyrifolia, Phoradendron californicum, g.l.c., amino acid analysis     

Defective Secretion of Mucilage is the Cellular Basis for Agravitropism in Primary Roots of Zea mays cv. Ageotropic

Root caps of primary, secondary, and seminal roots of Z. mayscv. Kys secrete large amounts of mucilage and are in close contactwith the root all along the root apex. These roots are stronglygraviresponsive. Secondary and seminal roots of Z. mays cv.Ageotropic are also strongly graviresponsive. Similarly, theircaps secrete mucilage and closely appress the root all alongthe root apex. However, primary roots of Z. mays cv. Ageotropicare non-responsive to gravity. Their caps secrete negligibleamounts of mucilage and contact the root only at the extremeapex of the root along the calyptrogen. These roots become graviresponsivewhen their tips are coated with mucilage or mucilage-like materials.Peripheral cells of root caps of roots of Z. mays cv. Kys containmany dictyosomes associated with vesicles that migrate to andfuse with the plasmalemma. Root-cap cells of secondary and seminal(i.e. graviresponsive) roots of Z. mays cv. Ageotropic are similarto those of primary roots of Z. mays cv. Kys. However, root-capcells of primary (i.e. non-graviresponsive) roots of Z. mayscv. Ageotropic have distended dictyosomal cisternae filled withan electron-dense, granular material. Large vesicles full ofthis material populate the cells and apparently do not fusewith the plasmalemma. Taken together, these results suggestthat non-graviresponsiveness of primary roots of Z. mays cv.Ageotropic results from the lack of apoplastic continuity betweenthe root and the periphery of the root cap. This is a resultof negligible secretion of mucilage by cells along the edgeof the root cap which, in turn, appears to be due to the malfunctioningof dictyosomes in these cells. Corn, dictyosomes, mucilage, root gravitropism, Zea mays cv. Ageotropic, Zea mays cv. Kys     

The Involvement of Glucose-6-Phosphatase in Mucilage Secretion by Root Cap Cells of Zea mays

In order to determine the involvement of glucose-6-phosphatasein mucilage secretion by root cap cells, we have cytochemicallylocalized the enzyme in columella and peripheral cells of rootcaps of Zea mays. Glucose-6-phosphatase is associated with theplasmalemma and cell wall of columella cells. As columella cellsdifferentiate into peripheral cells and begin to produce andsecrete mucilage, glucose-6-phosphatase staining intensifiesand becomes associated with the mucilage and, to a lesser extent,the cell wall. Cells being sloughed from the cap are characterizedby glucose-6-phosphatase staining being associated with thevacuole and plasmalemma. These changes in enzyme localizationduring cellular differentiation in root caps suggest that glucose-6-phosphataseis involved in the production and/or secretion of mucilage byperipheral cells of Z. mays. Zea mays, corn, glucose-6-phosphatase, columella cell, peripheral cell, mucilage, secretion, cytochemistry     

MUCILAGE PROCESSING AND SECRETION IN THE GREEN ALGA CLOSTERIUM. II. ULTRASTRUCTURE AND IMMUNOCYTOCHEMISTRY1

We conducted an ultrastructural and immunocytochemical analysis of the subcellular components involved in mucilage secretion in Closterium. In conventionally fixed cells, the mucilage vesicle appears dense-cored with an electron-dense center surrounded by radiating fibrils. In freeze-substituted cells, the vesicles are highly osmiophilic. These mucilage vesicles are produced from peripheral swellings of the trans face cisternae of the Golgi apparatus (GA). The vesicles apparently move from the GA, found in cytoplasmic depressions between lobes of the plastid, to the sub-plasma membrane peripheral cytoplasm. Here, they become associated with components of the peripheral cytoskeletal network. The mucilage is ultimately released through flask-shaped pores in the cell wall.     

The role of the diatom Cylindrotheca closterium in a mucilage event in the northern Adriatic Sea: coupling with high salinity water intrusions

The temporal and spatial distribution of mucilaginous aggregates,during the mucilage event of 2002 in the northern Adriatic,was studied in relation to waters of different salinity consideringthe aggregate’s age and proportion of Cylindrotheca closteriumin its microphytoplankton community. The results showed thatthis epipelic diatom is a dominating species in the microphytoplanktoncommunity of freshly formed aggregates, in spite of its negligibleabundance in the water column. The appearance and distributionof these aggregates in the water column was associated withwater of higher salinity. The same pattern was observed in thesummer of 2001, when a shorter and limited mucilage event occurred.These results suggest the importance of oligotrophic high salinitywater intrusions from the central Adriatic for a selective accumulationof C. closterium cells. Coupling between the increased numberand minimum growth state of C. closterium-accumulated cellsmight result in a hyperproduction of its own mucilage in theseaccumulation zones formed under the influence of high salinitywater intrusions. In contrast, in the upper lower salinity waterlayers, under the influence of a freshwater input, the phytoplanktoncommunity of the freshly formed aggregates was similar to thatof the surrounding water.     

Ultrastructure of the Resin Ducts of Mangifera indica L. (Anacardiaceae). 2. Resin Secretion in the Primary Stem Ducts

The resin of the mango stem consists mainly of terpenes. Theterpenes seem to be produced primarily by plastids, termed heresecretoplasts. At the beginning of the process of secretion,osmiophilic droplets are seen at the envelope of the secretoplastsand at elemints of periplastidal ER. In addition, such dropletsoccur also at Golgi bodies and occasionally in association withmitochondria. Later osmiophilic material fills the well-developbdER, which at this stage is mainly tubular. It appears that theER is involved in the transport of the sareted material towardsthe plasmalemma. Mangifera indica L., mango, Anacardiaceae, resin, resin ducts, secretion, secretoplasts, ultrastructure     

Studies of the Surfaces of Desert Plant Seeds: II. Ecological Adaptations of the Seeds of Blepharis persica

A study was made of the role of the hydrated mucilage whicharises from the integumentary hairs of Blepharis seeds and inhibitsgermination where there is an excess of water, and of the anatomicaland physiological basis for this phenomenon. It was found thatthis inhibition was not due to bacterial respiration. The appearanceof the dry mucilage in the unimbibed seeds is described fromscanning electron micrographs. The basic helical framework ofthe secondary wall thickenings and the very unusual second-orderframework of trabeculae in the integumentary hair cells aredescribed.     

水蕨卵膜的形成及其超微结构的观察

蕨类植物成熟卵的周围有一层卵膜,但其细微结构和形成过程仍不清楚,本研究应用透射电镜技术对水蕨(Ceratopteris thailictroides)卵细胞发育过程中卵膜的形成及超微结构进行了观察.结果表明水蕨卵细胞在发育中期开始形成卵膜,卵上方的卵膜十分显著,是由多层嗜锇性内质网片层附着于质膜内表面形成的,成熟时卵上方的卵膜中心部分厚,向边缘逐渐变薄,在嗜锇性片层之间填充有嗜锇性物质.比较而言,卵下方及侧面的卵膜薄,由两层紧密连接的嗜锇性膜构成.首次阐明了蕨类植物卵膜形成的超微结构,并对卵膜的一些功能进行了探讨.     

A Stereological Analysis of the Succulent Tissue 5Opuntia ficus-indica (L.) Mill.: I. DEVELOPMENT OF MUCILAGE CELLS

A correlated stereological and developmental analysis of thesucculent tissue of Opuntia ficus-indica was carried out. Thestereological parameters related to mucilage cells were describedas a function of their distance from the apical meristem. Polynomesof the second and third degree were found to describe the developmentalprocess. Three zones of development could be distinguished.The relation of the structure of the tissue to its physiologicalfunction and mucilage secretion is discussed.     

Mucilage Cells, Calcium Oxalate Crystals and Soluble Calcium in Opuntia ficus-indica

The subcellular location of soluble calcium in parenchymatousand mucilage cells of Opuntia ficus-indica was determined histochemically.Soluble calcium was observed in crystal chambers containingcalcium oxalate on the membrane of the vesicles. Calcium wasalso present in the plasmalemma, in plasmodesmata, in cell walls,in mitochondria and in the vacuoles. Especially marked was thepresence of soluble calcium in vesicles free or fused with theplasmalemma. Little free calcium was observed in other cellcompartments. In the calcium economy of tissues the location of soluble calciumand the transport of calcium to and from mucilage cells to parenchymatouscells and calcium oxalate idioblasts will play a role. Chelationof calcium by mucilage or oxalate, which depends on pH, ionicstrength, etc., will be important in this respect. Opuntia ficus-indica, calcium oxalate, mucilage cells, transport of calcium     

The Possible Involvement of Root-cap Mucilage in Gravitropism and Calcium Movement Across Root Tips of Allium cepa L

Roots of Allium cepa L. grown in aerated water elongate rapidly,but are not graviresponsive. These roots (1) possess extensivecolumella tissues comprised of cells containing numerous sedimentedamyloplasts, (2) lack mucilage on their tips, and (3) are characterizedby a weakly polar movement of calcium (Ca) across their tips.Placing roots in humid air correlates positively with the (1)onset of gravicurvature, (2) appearance of mucilage on tipsof the roots, and (3) onset of the ability to transport Ca polarlyto the lower side of the root tip. Gravicurvature of roots previouslysubmerged in aerated water is more rapid when roots are orientedvertically for 1–2 h in humid air prior to being orientedhorizontally. The more rapid gravicurvature of these roots correlatespositively with the accumulation of mucilage at the tips ofroots during the time the roots are oriented vertically. Therefore,the onset of gravicurvature and the ability of roots to transportCa to the lower sides of their tips correlate positively withthe presence of mucilage at their tips. These results suggestthat mucilage may be important for the transport of Ca acrossroot caps. Allium cepa, root gravitropism, root mucilage, calcium, onion     

A Further Study on Parasitism of the Diatom Fragilaria crotonensis Kitton by Chytridiaceous Fungi in Culture

Further detailed experiments under laboratory conditions havebeen carried out using clones of Fragilaria crotonensis Kitton.Two morphologically distinct types (rod- and flared-cell forms)were investigated in relation to their infection by a chytridreferred to as species 3. The pathogenicity of the chytrid Rhizophydiumfragilariae Canter towards four newly isolated clones of F.crotonensis was also studied. The results in general confirmedthat clones of the diatom composed of flared-type cells werecompatible with the development and increase of species 3 butremained more or less resistant to R. fragilariae. In contrast,rod-celled type clones showed exactly the opposite host parasiterelationships. Further study has shown that slight differencesin susceptibility towards a particular chytrid can occur withindiatom clones of similar morphological type. The presence ofhypersensitive algal cells was noted in relation to parasitismby both fungi. Some observations are recorded on the developmentof mucilage around filaments of the Fragilaria clones. Fragilaria crotonensis Kitton, Rhizophydium fragilariae Canter, chytrid, diatom, culture, parasitism, hypersensitivity, mucilage envelope     

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     

Observations on the Formation and Ultrastructure of the Egg Membrane in the fern Ceratopteris thalictroides (Parkeriaceae)

The mature egg of ferns possesses a layer of egg membrane in the periphery. However, the fine trastructure and the formation of the egg membrane in the egg of ferns are still unclear. The present paper described the formation and the ultrastructure of the egg membrane in the egg of the fern Ceratopteris thalictroides using transmission electron microscopy (TEM). The results show that the egg membrane begins to form at the stage of the maturing egg. The egg membrane in the upper side of the egg is prominent. It is formed by attaching of osmiophilic sheets of endoplasmic reticulum to the inner surface of the plasmalemma . When mature the egg membrane in the upper side of the egg is much thick in the central region and it becomes thinner gradually towards the margin. Some osmiophilic materials are filled in the spaces between the sheets of endoplasmic reticulum . On the contrary, the egg membrane in the lower side of the egg is thin . It is composed of twoosmiophilic membranes which are associated with each other closely. The formation and the ultrastructure of the egg membrane are described for the first time . Some functions of the egg membrane are also discussed .     

Characterizing Pathways by Which Gravitropic Effectors Could Move from the Root Cap to the Root of Primary Roots of Zea mays

Plasmodesmata linking the root cap and root in primary rootsZea mays are restricted to approx. 400 protodermal cells borderingapprox. 110000 µm² of the calyptrogen of the root cap.This area is less than 10% of the cross-sectional area of theroot-tip at the cap junction. Therefore, gravitropic effectorsmoving from the root cap to the root can move symplasticallyonly through a relatively small area in the centre of the root.Decapped roots are non-responsive to gravity. However, decappedroots whose caps are replaced immediately after decapping arestrongly graviresponsive. Thus, gravicurvature occurs only whenthe root cap contacts the root, and symplastic continuity betweenthe cap and root is not required for gravicurvature. Completelyremoving mucilage from the root tip renders the root non-responsiveto gravity. Taken together, these data suggest that gravitropiceffectors move apoplastically through mucilage from the capto the root. Calyptrogen, open meristem, protoderm, root cap, root gravitropism, Zea mays