Sample records for dictyosomes

  1. Ultrastructure of the partially coated reticulum and dictyosomes during endocytosis by soybean protoplasts.

    Tanchak, M A; Rennie, P J; Fowke, L C


    Individual and serial sections were used to obtain detailed information regarding the morphology and distribution of the partially coated reticulum (PCR) and to determine its relationship with dictyosomes in endocytotically active soybean (Glycine max. (L.) Merr.) protoplasts. The results confirm and extend the description of the PCR provided by T.C. Pesacreta and W.J. Lucas (1985, Protoplasma 125, 173-184) from whole cells of selected angiosperms. The PCR of soybean protoplasts consists of a set of interconnected tubular membranes bearing a clathrin-like coat over part of their cytoplasmic surface. A dilation, sometimes containing small vesicles, is frequently seen in this organelle. The PCR often appears associated with dictyosomes but also occurs independent of other cell organelles. Only one example of a direct connection between the PCR and dictyosomes was observed.Following adsorptive endocytosis of cationized ferritin, the label appears in the PCR within 2 min and accumulates with time. It is never observed in the membrane dilations. Serial sectioning established that dictyosomes are labelled with cationized ferritin around the periphery of several cisternae, including those on both sides of the same dictyosome.

  2. 3-D analysis of dictyosomes and multivesicular bodies in the green alga Micrasterias denticulata by FIB/SEM tomography.

    Wanner, Gerhard; Schäfer, Tillman; Lütz-Meindl, Ursula


    In the present study we employ FIB/SEM tomography for analyzing 3-D architecture of dictyosomes and formation of multivesicular bodies (MVB) in high pressure frozen and cryo-substituted interphase cells of the green algal model system Micrasterias denticulata. The ability of FIB/SEM of milling very thin 'slices' (5-10 nm), viewing the block face and of capturing cytoplasmic volumes of several hundred μm(3) provides new insight into the close spatial connection of the ER-Golgi machinery in an algal cell particularly in z-direction, complementary to informations obtained by TEM serial sectioning or electron tomography. Our FIB/SEM series and 3-D reconstructions show that interphase dictyosomes of Micrasterias are not only closely associated to an ER system at their cis-side which is common in various plant cells, but are surrounded by a huge "trans-ER" sheath leading to an almost complete enwrapping of dictyosomes by the ER. This is particularly interesting as the presence of a trans-dictyosomal ER system is well known from mammalian secretory cells but not from cells of higher plants to which the alga Micrasterias is closely related. In contrast to findings in plant storage tissue indicating that MVBs originate from the trans-Golgi network or its derivatives our investigations show that MVBs in Micrasterias are in direct spatial contact with both, trans-Golgi cisternae and the trans-ER sheath which provides evidence that both endomembrane compartments are involved in their formation.

  3. Acid phosphatase localization in the digestive glands of Dionaea muscipula Ellis flytraps.

    Henry, Y; Steer, M W


    The intracellular localization of acid phosphatases in stimulated digestive glands of Dionaea flytraps has been studied to provide evidence for the route taken by this enzyme during secretion. Previous studies have either included or excluded a role for the dictyosomes in this pathway. Both p-nitrophenyl phosphate and beta-glycerophosphate were used as substrates, and both gave similar localization patterns. Unstimulated glands contained little phosphatase activity in the endomembrane system, whereas 24 and 48 hr after stimulation, heavy deposits of lead were located in the endoplasmic reticulum cisternae, including the nuclear envelope, the dictyosome cisternae, and secretory vesicles. Since dictyosome activation, as judged by the presence of secretory vesicles in the cytoplasm, also coincides with gland stimulation, we conclude that secretion of the hydrolase enzymes occurs via this route and not, as suggested elsewhere, via direct endoplasmic reticulum to plasma membrane connections.

  4. Influence of microgravity on cellular differentiation in root caps of Zea mays

    Moore, R.; Fondren, W. M.; McClelen, C. E.; Wang, C. L.


    We launched imbibed seeds of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on cellular differentiation in root caps. The influence of microgravity varied with different stages of cellular differentiation. Overall, microgravity tended to 1) increase relative volumes of hyaloplasm and lipid bodies, 2) decrease the relative volumes of plastids, mitochondria, dictyosomes, and the vacuome, and 3) exert no influence on the relative volume of nuclei in cells comprising the root cap. The reduced allocation of dictyosomal volume in peripheral cells of flight-grown seedlings correlated positively with their secretion of significantly less mucilage than peripheral cells of Earth-grown seedlings. These results indicate that 1) microgravity alters the patterns of cellular differentiation and structures of all cell types comprising the root cap, and 2) the influence of microgravity on cellular differentiation in root caps of Zea mays is organelle specific.

  5. Influence of lead on the development of lupin seedlings and ultrastructural localization of this metal in the roots

    Adam Woźny


    Full Text Available The effect of lead on the early phases of development of yellow lupin seedlings was investigated. In the presence of this metal the number of germinating seeds was found to diminish distinctly, the hypocotyls and roots were shorter and the fresh weight and anthocyanin content in the cotyledones were markedly decreased. In the root cap cells lead was present in the vacuoles, ER, dictyosomes, the nuclear envelope and cell walls.


    Manton, Irene


    Micrographs of dictyosomes in face view and in profile, together with serial sections representing both these planes, are reproduced from three sample cells at different developmental stages in the meristem of Anthoceros. The stages are: a vegetative cell at anaphase of a mitotic division, a vegetative cell in an early stage of postmitotic extension growth, and a young spore mother cell in the act of rounding up before the onset of meiosis. The observations suggest that proliferation of tubules from the edges of the dictyosomal cisternae into the cytoplasm is occurring with varying intensity and with slightly different morphological expression in all three cells. In all, the tubules are joined into a reticulum which exhibits local swellings at varying distances from the unfenestrated part of the subtending cisterna. A comparison is suggested between the observed reticulum and "smooth" endoplasmic reticulum of animals but it is not claimed that all the cytoplasmic tubules detectable in Anthoceros need have arisen in this way. Morphological differences discernible between tubules near their point of attachment to dictyosomes and others apparently involved in the formation of the new nuclear membrane at the end of a cell division could mean that more than one category of tube may exist in these cells. A plea is registered for restraint in the formulation of far reaching theories until more facts are available on unequivocal evidence. PMID:13766334

  7. Defective secretion of mucilage is the cellular basis for agravitropism in primary roots of Zea mays cv. Ageotropic

    Miller, I.; Moore, R.


    Root caps of primary, secondary, and seminal roots of Z. mays cv. Kys secrete large amounts of mucilage and are in close contact with the root all along the root apex. These roots are strongly graviresponsive. Secondary and seminal roots of Z. mays cv. Ageotropic are also strongly graviresponsive. Similarly, their caps secrete mucilage and closely appress the root all along the root apex. However, primary roots of Z. mays cv. Ageotropic are non-responsive to gravity. Their caps secrete negligible amounts of mucilage and contact the root only at the extreme apex of the root along the calyptrogen. These roots become graviresponsive when their tips are coated with mucilage or mucilage-like materials. Peripheral cells of root caps of roots of Z. mays cv. Kys contain many dictyosomes associated with vesicles that migrate to and fuse with the plasmalemma. Root-cap cells of secondary and seminal (i.e. graviresponsive) roots of Z. mays cv. Ageotropic are similar to those of primary roots of Z. mays cv. Kys. However, root-cap cells of primary (i.e. non-graviresponsive) roots of Z. mays cv. Ageotropic have distended dictyosomal cisternae filled with an electron-dense, granular material. Large vesicles full of this material populate the cells and apparently do not fuse with the plasmalemma. Taken together, these results suggest that non-graviresponsiveness of primary roots of Z. mays cv. Ageotropic results from the lack of apoplastic continuity between the root and the periphery of the root cap. This is a result of negligible secretion of mucilage by cells along the edge of the root cap which, in turn, appears to be due to the malfunctioning of dictyosomes in these cells.

  8. Cellular effects of tributyltin (TBT) on the penis epithelium cells of prosobranchs ( Hinia reticulata and Ocinebrina aciculata)

    Brick, M.; Deutsch, U.; Fioroni, P.


    Cytopathological effects on organelles of penis epithelium cells were investigated in prosobranchs that had been exposed for two weeks to three months to high TBT-concentrations in artificial seawater. TBT exposure damaged cell organelles, such as mitochondria, Golgi dictyosomes, endoplasmatic reticulum, and injured the cell membranes. In addition, atypical intercellular spaces were observed between the cells of the epithelial layer. Further cell alterations included the increase of residual bodies within the cells as well as structural changes of the basal lamina. The ultrastructural changes were compared with cell alterations of specimens which had been collected in a polluted environment on the coast of Brittany (France).

  9. Calcium in pollen-pistil interaction in `Petunia hybrida Hor`. Pt. 1. Localization of Ca{sup 2+} ions in mature pollen grain using pyroantimonate and autoradiographic methods

    Bednarska, E.; Butowt, R. [Uniwersytet Mikolaja Kopernika, Torun (Poland)


    The localization of Ca{sup 2+} in the mature pollen grain and the flow of these ions the somatic tissues of the anther to the pollen grains has been studied using pyroantimonate and autoradiographic methods. In the pollen grain, Ca{sup 2+} ions have been localized in the sporoderm in the cytoplasmic vesicles of probably dictyosomal origin. Calcium ions were transported into the sporoderm together with the compounds of degenerating tapetum. The material of degenerating tapetum forms pollen coat surrounding the mature pollen grains. (author). 18 refs, 9 figs.

  10. The paraveinal mesophyll of soybean leaves in relation to assimilate transfer and compartmentation : I. Ultrastructure and histochemistry during vegetative development.

    Franceschi, V R; Giaquinta, R T


    The paraveinal mesophyll (PVM) is a unique and specialized, one-cell-thick tissue spanning the vascular bundles at the level of the phloem in soybean (Glycine max) (L.) Merr.) leaves. Its position within the leaf dictates that all photosynthate produced in the palisade and spongy mesophyll must pass through this specialized layer enroute to the phloem. Symplastic continuity, via plasmodesmata, exists between the PVM and bundle sheath, palisade parenchyma and spongy mesophyll. During leaf ontogeny the PVM is the first tissue to differentiate and at maturity these cells are six to eight times larger than other mesophyll cells, are highly vacuolate, and are interconnected by tubular arms. The PVM undergoes several unique structural and metabolic modifications during leaf development. The PVM cytoplasm, in vegetative plants, is dense, enriched in rough endoplasmic reticulum and dictyosomes, but contains few, small starch-free chloroplasts and few microbodies. Unlike the tonoplast of mesophyll cells, the tonoplast of the PVM is unusually thick and dense-staining. During leaf development the vacuoles of PVM cells accumulate a glycoprotein derived from the dictyosomes which reacts with the protein staining reagents, mercuric bromophenol blue and sulfaflavine, and is degraded by Pronase. Both the vacuolar material and tonoplast are also stained by phosphotungstic acid, which at low pH is relatively selective for glycoprotein. A unique role of the PVM in the transport and compartmentation of nitrogen reserves in soybeans is discussed.

  11. The pollen tube clear zone:Clues to the mechanism of polarized growth

    Peter K Hepler; Lawrence J Winship


    Pollen tubes usually exhibit a prominent region at their apex called the “clear zone” because it lacks light refracting amyloplasts. A robust, long clear zone often associates with fast growing pollen tubes, and thus serves as an indicator of pollen tube health. Nevertheless we do not understand how it arises or how it is maintained. Here we review the structure of the clear zone, and attempt to explain the factors that contribute to its formation. While amyloplasts and vacuolar elements are excluded from the clear zone, virtually all other organelles are present including secretory vesicles, mitochondria, Golgi dictyosomes, and the endoplas-mic reticulum (ER). Secretory vesicles aggregate into an inverted cone appressed against the apical plasma membrane. ER elements move nearly to the extreme apex, whereas mitochondria and Golgi dictyosomes move less far forward. The cortical actin fringe assumes a central position in the control of clear zone formation and maintenance, given its role in generating cytoplasmic streaming. Other likely factors include the tip-focused calcium gradient, the apical pH gradient, the influx of water, and a host of signaling factors (small G-proteins). We think that the clear zone is an emergent property that depends on the interaction of several factors crucial for polarized growth.

  12. Quantitative analysis of organelle distribution and dynamics in Physcomitrella patens protonemal cells

    Furt Fabienne


    Full Text Available Abstract Background In the last decade, the moss Physcomitrella patens has emerged as a powerful plant model system, amenable for genetic manipulations not possible in any other plant. This moss is particularly well suited for plant polarized cell growth studies, as in its protonemal phase, expansion is restricted to the tip of its cells. Based on pollen tube and root hair studies, it is well known that tip growth requires active secretion and high polarization of the cellular components. However, such information is still missing in Physcomitrella patens. To gain insight into the mechanisms underlying the participation of organelle organization in tip growth, it is essential to determine the distribution and the dynamics of the organelles in moss cells. Results We used fluorescent protein fusions to visualize and track Golgi dictyosomes, mitochondria, and peroxisomes in live protonemal cells. We also visualized and tracked chloroplasts based on chlorophyll auto-fluorescence. We showed that in protonemata all four organelles are distributed in a gradient from the tip of the apical cell to the base of the sub-apical cell. For example, the density of Golgi dictyosomes is 4.7 and 3.4 times higher at the tip than at the base in caulonemata and chloronemata respectively. While Golgi stacks are concentrated at the extreme tip of the caulonemata, chloroplasts and peroxisomes are totally excluded. Interestingly, caulonemata, which grow faster than chloronemata, also contain significantly more Golgi dictyosomes and fewer chloroplasts than chloronemata. Moreover, the motility analysis revealed that organelles in protonemata move with low persistency and average instantaneous speeds ranging from 29 to 75 nm/s, which are at least three orders of magnitude slower than those of pollen tube or root hair organelles. Conclusions To our knowledge, this study reports the first quantitative analysis of organelles in Physcomitrella patens and will make possible

  13. Integument cell differentiation in dandelions (Taraxacum, Asteraceae, Lactuceae) with special attention paid to plasmodesmata.

    Płachno, Bartosz J; Kurczyńska, Ewa; Świątek, Piotr


    The aim of the paper is to determine what happens with plasmodesmata when mucilage is secreted into the periplasmic space in plant cells. Ultrastructural analysis of the periendothelial zone mucilage cells was performed on examples of the ovule tissues of several sexual and apomictic Taraxacum species. The cytoplasm of the periendothelial zone cells was dense, filled by numerous organelles and profiles of rough endoplasmic reticulum and active Golgi dictyosomes with vesicles that contained fibrillar material. At the beginning of the differentiation process of the periendothelial zone, the cells were connected by primary plasmodesmata. However, during the differentiation and the thickening of the cell walls (mucilage deposition), the plasmodesmata become elongated and associated with cytoplasmic bridges. The cytoplasmic bridges may connect the protoplast to the plasmodesmata through the mucilage layers in order to maintain cell-to-cell communication during the differentiation of the periendothelial zone cells.

  14. The structure of the endodermis during the development of wheat (Triticum aestivum L. roots

    Grażyna Grymaszewska


    Full Text Available Four stages of development in the process of differentiation of the root endodermis of wheat (Triticum aestivum L. var. Grana are described. The proendodermis cells have a meristematic nature. Their vacuoles accumulated an osmophilic material. In the next stage, Casparian strips arose in the walls of the endodermis. Dictyosomes and ER cisterns were numerous in the protoplasts of these cells. In the following stage, a suberin lamella was deposited over the entire internal surface of the primary cell wall. In the final stage, a secondary cell wall, thickened in the form of a letter U, was formed. In secondary wall simple pits arose. The endodermis of the wheat root developed asynchronously, more quickly over the phloem bundles.

  15. Endocytosis of cationized ferritin by coated vesicles of soybean protoplasts.

    Tanchak, M A; Griffing, L R; Mersey, B G; Fowke, L C


    Soybean (Glycine max (L.) Merr.) protoplasts have been surface-labelled with cationized ferritin, and the fate of the label has been followed ultrastructurally. Endocytosis of the label occurs via the coated-membrane system. The pathway followed by the label, once it has been taken into the interior of the protoplast, appears to be similar to that found during receptor-mediated endocytosis in animal cells. Cationized ferritin is first seen in coated vesicles but rapidly appears in smooth vesicles. Labelled, partially coated vesicles are occasionally observed, indicating that the smooth vesicles may have arisen by the uncoating of coated vesicles. Structures which eventually become labelled with cationized ferritin include multivesicular bodies, dictyosomes, large smooth vesicles, and a system of partially coated reticula.

  16. Ultrastructure of cells after reversible dark-induced blocking of mitotic divisions in antheridial filaments of Chara vulgaris L.

    Maria Kwiatkowska


    Full Text Available As compared with the control plants cultured under photoperiodic L : D = =14 : 10 conditions (K w i a t k o w s k a, M a s z e w s k i, 1978, the ultrastructure of nuclei -in cells blocked by a 5 day exposure to continuous darkness is characterized by homogenous arrangement. This homogeneity is maintained in all generations of antheridial filaments irrespective of cell length, which in the controls, being directly correlated with particular type of nuclear structure, may serve as a precise indicator of a given stage of interphase. From similarities in both the spatial distribution and content of condensed chromatin in is concluded that the block of the cell cycle is imposed at the beginning of the G2 phase. On comparing these cells with the early G2 period (stage VII in the control plants, marked changes in the structure of nucleoli were found. They decrease in size by half owing to the complete decline of granular component. The area occupied by endoplasmic reticulum undergoes a 50% reduction. The decrease in the activity of Golgi apparatus expressed by a drop in number of smooth vesicles surrounding a single dictyosome is found to parallel the limited rate of cell growth. The number of coated vesicles and cisterns of dictyosome slightly increases. Mitochondria show typical condensed configuration with dense matrices and swollen cristae, while in the control orthodox forms are prevailing. The mean size of mitochondria is smaller, but their number exceeds that of the control plants. The surface area of mitochondrial profiles is found to remain constant proportion of the cytoplasm section, e.g., about 3%. Dark-cultured antheridial filaments show absolute decline of lipid droplets. No differences were found in structure of plastids and vacuols, as well as in number of ribosomes in cytoplasm surface unit.

  17. Lead stress effects on physiobiochemical activities of higher plants.

    Sengar, Rakesh Singh; Gautam, Madhu; Sengar, Rajesh Singh; Garg, Sanjay Kumar; Sengar, Kalpana; Chaudhary, Reshu


    Lead is a metallic pollutant emanating from various environmental sources including industrial wastes, combustion of fossil fuels, and use of agrochemicals. Lead may exist in the atmosphere as dusts, fumes, mists, and vapors, and in soil as a mineral. Soils along roadsides are rich in lead because vehicles burn leaded gasoline, which contributes to environmental lead pollution. Other important sources of lead pollution are geological weathering, industrial processing of ores and minerals, leaching of lead from solid wastes, and animal and human excreta. Lead is nondegradable, readily enters the food chain, and can subsequently endanger human and animal health. Lead is one of the most important environment pollutants and deserves the increasing attention it has received in recent decades. The present effort was undertaken to review lead stress effects on the physiobiochemical activity of higher plants. Lead has gained considerable attention as a potent heavy metal pollutant because of growing anthropogenic pressure on the environment. Lead-contaminated soils show a sharp decline in crop productivity. Lead is absorbed by plants mainly through the root system and in minor amounts through the leaves. Within the plants, lead accumulates primarily in roots, but some is translocated to aerial plant parts. Soil pH, soil particle size, cation-exchange capacity, as well as root surface area, root exudation, and mycorrhizal transpiration rate affect the availability and uptake of lead by plants. Only a limited amount of lead is translocated from roots to other organs because there are natural plant barriers in the root endodermis. At lethal concentrations, this barrier is broken and lead may enter vascular tissues. Lead in plants may form deposits of various sizes, present mainly in intercellular spaces, cell walls, and vacuoles. Small deposits of this metal are also seen in the endoplasmic reticulum, dictyosome, and dictyosome-derived vesicles. After entering the cells, lead

  18. The ultrastructure of the mature embryo sac in the natural tetraploid of red clover (Trifolium pratense L.: that has a very low rate of seed formation

    Gönül Algan


    Full Text Available In this study, ultrastructural organization of cells in the mature embryo sac of natural tetraploid Trifolium pratense L. was investigated. The mature embryo sac of this plant contains an egg cell with two synergids at the micropylar end, and a central cell with two polar nuclei. The ultrastructure of these cells agrees with what is known for most angiosperms studied with the electron microscope. The egg cell is a large and highly vacuolate cell, partially surrounded by a wall. Much of the cytoplasm is located around the nucleus at the chalazal end and there are few numbers of channel-shaped endoplasmic reticulum, mitochondria, plastids and numerous ribosomes distributed throughout the cytoplasm. Unlike the egg cell, much of the cytoplasm in synergid cells is located at micropylar part of the cell and the synergid cytoplasm contains especially, large numbers of rough endoplasmic reticulum, free ribosomes, mitochondria and plastids. The central cell of T. pratense L. contains two large polar nuclei which lie close to the egg apparatus. Each polar nucleus has a single, large, dense nucleolus that contains several nucleolar vacuoles. Much of the central cell cytoplasm consisting of granular and agranular endoplasmic reticulum, mitochondria, plastids, ribosomes, dictyosomes and lipid bodies are placed around polar nuclei.

  19. Light and electron microscopic studies on the excretory system of Macrobiotus richtersi Murray, 1911 (Eutardigrada).

    Weglarska, B


    The excretory system of Macrobiotus richtersi consists of one dorsal and two lateral components and shows a high degree of structural complexity. In each of these a tricellular external lobe and a column can be distinguished, the two parts being connected distally. The surface of the lobe cells is increased by deep basal infoldings and fingerlike processes which form a labyrinth next to the basal lamina. Their cytoplasm contains numerous mitochondria, a well developed rough endoplasmic reticulum, dictyosomes, and granules in amounts depending on the physiological state of the animal. Excretory crystals occur in caveolae located in the lobe: between the fingershaped processes of the cell and in the space enclosed by the basal lamina on one side and the column on the other. The column faces an extracellular channel meandering along its whole length which is surrounded on the outside by a basal lamina. Morphologically the column is similar to the protonephridial channel of Rotifera. At the ultrastructural level, the cytoplasm of the column shows numerous mitochondria, rough endoplasmic reticulum, lysosomes, and a well developed Golgi apparatus. The lumen of the channel is coated by glycocalyx. At the base of the column several small cells form the proximal part of a duct that communicates with the gut. The morphology and ultrastructure of the excretory system of M. richtersi have been compared with similar a system in Isohypsibius megalonyx (Greven, 1979), and on these grounds a proposal is put forward to call the excretory organs of Tardigrada "nephridia" instead of "Malpighian tubules" .

  20. Are obligatory apomicts invested in the pollen tube transmitting tissue? Comparison of the micropyle ultrastructure between sexual and apomictic dandelions (Asteraceae, Lactuceae).

    Płachno, Bartosz J; Świątek, Piotr; Kozieradzka-Kiszkurno, Małgorzata; Majeský, Ľuboš; Marciniuk, Jolanta; Stolarczyk, Piotr


    With the exception of the sunflower, little information concerning the micropyle ultrastructure of the family Asteraceae is available. The aim of our study was to compare the micropyle structure in amphimictic and apomictic dandelions. Ultrastructural studies using buds and flowers during anthesis have been done on the micropyle of the sexual and apomictic Taraxacum. In all of the species that were examined, the micropylar canal was completely filled with ovule transmitting tissue and the matrix that was produced by these cells. The ovule transmitting tissue was connected to the ovarian transmitting tissue. The micropyle was asymmetrical because the integument epidermis that forms the transmitting tissue was only on the funicular side. There was a cuticle between the obturator cells and epidermal cells on the other side of integument. The micropylar transmitting tissue cells and theirs matrix reached the synergid apex. The cytoplasm of the transmitting tissue cells was especially rich in rough endoplasmic reticulum (ER), dictyosomes, and mitochondria. No major differences were detected between the micropyle structure of the amphimictic and apomictic species; thus, a structural reduction of obturator does not exist. The ovule transmitting tissue is still active in apomictic dandelions despite the presence of the embryo and endosperm. Differences and similarities between the micropyle structure in the Asteraceae that have been studied to date are discussed.

  1. Nuclear DNA content and ultrastructure of secretory cells of Vicia faba L. stigma

    Bogdan Wróbel


    Full Text Available The object of study was the level of nuclear DNA and the ultrastructural transformations in the secretory cells of the stigma in Vicia faba L. It has been found that the stigmal cells which are active in biogenesis and exudate secretion are diploid cells whose differentiation starts from 2C DNA level. The presence of a population of nuclei with an amount DNA of about 2.5 C suggests that the metabolic activity of those cells may be regulated through supplementary incomplete replication. The ultrastructural transformations of secretory cells point to three stages of biogenesis and secretion of exudate. Stage I, before the start of the cell's secretory functions, is characterized by the development of the protein synthesizing apparatus and the activity of dictyosomes. In development stage II vesicular electron-transparent exudate is secreted. Stage III of exudate biogenesis is production of lipids. They form mainly in the plastids and are secreted with the involvement of the cell's vacuolar system.

  2. Micrasterias as a Model System in Plant Cell Biology

    Lütz-Meindl, Ursula


    The unicellular freshwater alga Micrasterias denticulata is an exceptional organism due to its complex star-shaped, highly symmetric morphology and has thus attracted the interest of researchers for many decades. As a member of the Streptophyta, Micrasterias is not only genetically closely related to higher land plants but shares common features with them in many physiological and cell biological aspects. These facts, together with its considerable cell size of about 200 μm, its modest cultivation conditions and the uncomplicated accessibility particularly to any microscopic techniques, make Micrasterias a very well suited cell biological plant model system. The review focuses particularly on cell wall formation and composition, dictyosomal structure and function, cytoskeleton control of growth and morphogenesis as well as on ionic regulation and signal transduction. It has been also shown in the recent years that Micrasterias is a highly sensitive indicator for environmental stress impact such as heavy metals, high salinity, oxidative stress or starvation. Stress induced organelle degradation, autophagy, adaption and detoxification mechanisms have moved in the center of interest and have been investigated with modern microscopic techniques such as 3-D- and analytical electron microscopy as well as with biochemical, physiological and molecular approaches. This review is intended to summarize and discuss the most important results obtained in Micrasterias in the last 20 years and to compare the results to similar processes in higher plant cells. PMID:27462330

  3. Modification by Ethylene of the Cell Growth Pattern in Different Tissues of Etiolated Lupine Hypocotyls 1

    Sánchez-Bravo, José; Ortuño, Ana M.; Pérez-Gilabert, Manuela; Acosta, Manuel; Sabater, Francisco


    The influence of ethylene on growth in etiolated lupine (Lupinus albus L.) hypocotyls was studied in ethephon-treated plants. Ethephon reduced the length and increased the diameter of hypocotyls. At the end of the hypocotyl growth period (14 days), the fresh weight was reduced by 53%, and the dry weight was reduced by 16%. Thus, ethylene reduced water uptake in the tissues to a greater extent than the incorporation of new materials. Light microscopic measurements showed that the thickness of tissues was stimulated by ethylene, the vascular cylinder and cortex exhibiting greater increases (55 and 45%, respectively) than pith (26%) or epidermis (12%). Ethephon modified the cell growth pattern, stimulating lateral cell expansion and cell wall thickness, while reducing cell elongation. The response to ethylene varied in the different tissues and was higher in cortex and pith cells than in the epidermis cells. The ethylene-induced cell expansion in the cortex varied according to the localization of cells in the tissue: the central and subepidermal layers showed little change, whereas the innermost layers exhibited the greatest increase. Electron microscopy revealed that ethylene increased both the rough endoplasmic reticulum and dictyosomes, suggesting that ethylene stimulated the secretion of cell wall materials. In untreated seedlings, the pattern of cell growth was similar in cells from the epidermis, cortex, and pith. The final cell size varied along the hypocotyl, the cells becoming shorter and broader the closer to the basal zones of the organ. ImagesFigure 1Figure 5 PMID:16668735

  4. Micrasterias as a model system in plant cell biology

    Ursula Luetz-Meindl


    Full Text Available The unicellular freshwater alga Micrasterias denticulata is an exceptional organism due to its extraordinary star-shaped, highly symmetric morphology and has thus attracted the interest of researchers for many decades. As a member of the Streptophyta, Micrasterias is not only genetically closely related to higher land plants but shares common features with them in many physiological and cell biological aspects. These facts, together with its considerable cell size of about 200 µm, its modest cultivation conditions and the uncomplicated accessibility particularly to any microscopic techniques, make Micrasterias a very well suited cell biological plant model system. The review focuses particularly on cell wall formation and composition, dictyosomal structure and function, cytoskeleton control of growth and morphogenesis as well as on ionic regulation and signal transduction. It has been also shown in the recent years that Micrasterias is a highly sensitive indicator for environmental stress impact such as heavy metals, high salinity, oxidative stress or starvation. Stress induced organelle degradation, autophagy, adaption and detoxification mechanisms have moved in the center of interest and have been investigated with modern microscopic techniques such as 3-D- and analytical electron microscopy as well as with biochemical, physiological and molecular approaches. This review is intended to summarize and discuss the most important results obtained in Micrasterias in the last 20 years and to compare the results to similar processes in higher plant cells.

  5. Ultrastructure of Trimastix pyriformis (Klebs) Bernard et al.: similarities of Trimastix species with retortamonad and jakobid flagellates.

    O'Kelly, C J; Farmer, M A; Nerad, T A


    Trimastix pyriformis (Klebs 1893) Bernard et al. 1999, is a quadriflagellate, free-living, bacterivorous heterotrophic nanoflagellate from anoxic freshwaters that lacks mitochondria. Monoprotist cultures of this species contained naked trophic cells with anterior flagellar insertion and a conspicuous ventral groove. Bacteria were ingested at the posterior end of the ventral groove, but there was no persistent cytopharyngeal complex. The posterior flagellum resided in this groove, and bore two prominent vanes. A Golgi body (dictyosome) was present adjacent to the flagellar insertion. The kinetid consisted of four basal bodies, four microtubular roots, and associated fibers and bands. Duplicated kinetids, each with four basal bodies and microtubular root templates, appeared at the poles of the open mitotic spindle. Trimastix pyriformis is distinguishable from other Trimastix species on the basis of external morphology, kinetid architecture and the distribution of endomembranes. Trimastix species are most similar to jakobid flagellates, especially Malawimonas jakobiformis, and to species of the retortamonad genus Chilomastix. Retortamonads may have evolved from a Trimastix-like ancestor through loss of "canonical" (easily seen with electron microscopy) endomembrane systems and elaboration of cytoskeletal elements associated with the cytostome/cytopharynx complex.

  6. Characterization of Selenaion koniopes n. gen., n. sp., an amoeba that represents a new major lineage within heterolobosea, isolated from the Wieliczka salt mine.

    Park, Jong Soo; De Jonckheere, Johan F; Simpson, Alastair G B


    A new heterolobosean amoeba, Selenaion koniopes n. gen., n. sp., was isolated from 73‰ saline water in the Wieliczka salt mine, Poland. The amoeba had eruptive pseudopodia, a prominent uroid, and a nucleus without central nucleolus. Cysts had multiple crater-like pore plugs. No flagellates were observed. Transmission electron microscopy revealed several typical heterolobosean features: flattened mitochondrial cristae, mitochondria associated with endoplasmic reticulum, and an absence of obvious Golgi dictyosomes. Two types of larger and smaller granules were sometimes abundant in the cytoplasm--these may be involved in cyst formation. Mature cysts had a fibrous endocyst that could be thick, plus an ectocyst that was covered with small granules. Pore plugs had a flattened dome shape, were bipartite, and penetrated only the endocyst. Phylogenies based on the 18S rRNA gene and the presence of 18S rRNA helix 17_1 strongly confirmed assignment to Heterolobosea. The organism was not closely related to any described genus, and instead formed the deepest branch within the Heterolobosea clade after Pharyngomonas, with support for this deep-branching position being moderate (i.e. maximum likelihood bootstrap support--67%; posterior probability--0.98). Cells grew at 15-150‰ salinity. Thus, S. koniopes is a halotolerant, probably moderately halophilic heterolobosean, with a potentially pivotal evolutionary position within this large eukaryote group.

  7. Activation of rape (Brassica napus L. embryo during seed germination. V. The first zones of ultrastructural changes and their expansion

    Mieczysław Karaś


    Full Text Available In the germinating rape embryo the columella and basal part of hypocotyl undergo earliest activation. Its first ultrastructural symptom is the appearance of numerous ER vesicles after 3-6 h of seed swelling. Their number is the highest in the external layers of the columella and decreases in basipetal direction. Dermatogen cells in the basal zone of the hypocotyl contain the greatest amount of ER structures, whereas decreasing amounts are found in both directions along the embryo axis and centripetally. Further changes in the ER spread in a similar order. The vesicles merge and form a tubular and plate-like ER. Then, they disappear and are replaced by tubular and vesicular forms. The changes in the ER are gradually followed by ultrastructural symptoms of activation of mitochondria, plastids and dictyosomes. The highest number of ER structures and other organelles accumulate in root cells shortly before piercing of the seed coat. After germination their amount decreases and remains almost stable.

  8. Flowering biology and structure of floral nectaries in Galanthus nivalis L.

    Elżbieta Weryszko-Chmielewska


    Full Text Available In Poland Galanthus nivalis L. is partially protected. The flowers of this species are one of the first sources of nectar and pollen for insects from February to April. The aim of this study was to present the flowering biology as well as the topography, anatomical, and ultrastructural features of the floral nectary. The flower lifespan, the breeding system, and the mass of pollen and nectar produced by the flowers were determined. Examination of the nectary structure was performed using light, fluorescence, scanning and transmission electron microscopy. The flower of G. nivalis lives for about 30 days. The stamens and pistils mature simultaneously and during this time nectar is secreted. The anthers of one flower produced the large amount of pollen (4 mg. The breeding system of G. nivalis was found to be characterized by partial self-compatibility, outcrossing, and xenogamy. The nectary is located at the top of the inferior ovary. The nectary epidermal cells are characterized by striated cuticular ornamentation. Initially, the secreted nectar formed vesicle-like protuberances under the cuticle. The epidermal and parenchymal cells contain numerous plastids, mitochondria, dictyosomes, ER cisterns, and vesicles fused with the plasmalemma, which indicates granulocrine nectar secretion.

  9. Ultrastructure of the digestive system and the fate of midgut during embryonic development in Porcellio scaber (Crustacea: Isopoda).

    Strus, Jasna; Klepal, Waltraud; Repina, Janja; Tusek-Znidaric, Magda; Milatovic, Masa; Pipan, Ziva


    Microscopic anatomy of the digestive system in embryos and larvae of the terrestrial isopod crustacean Porcellio scaber was investigated by light bright field, fluorescence and electron microscopy. During marsupial ontogenetic development the event-dependent staging was used to discriminate the various embryonic stages. At the late embryo stage the differentiation of the ectodermal part of the gut into the complex filtering foregut and the hindgut with absorptive and transporting functions is accomplished. The gut of the marsupial manca larva is fully developed and similar to that of the adult. In early embryos the endodermal midgut gland primordia are filled with yolk and lipid globules. In late embryos the epithelium of paired midgut gland tubes is composed of two cell types; one of them exhibits orange autofluorescence. The endodermal cells located between the foregut and the midgut glands of late embryos form the prospective midgut. The cells have electron dense cytoplasm, abundant glycogen fields, endoplasmic reticulum, dictyosomes and numerous vesicles. In the adults the endodermal cells of the midgut remain only in the midgut gland ducts which connect the midgut glands and the foregut. Details of the cellular ultrastructure and morphogenesis of the ectodermal and endodermal parts of the digestive system during embryonic development of Porcellio scaber provide data for further phylogenetic and comparative studies in peracaridan crustaceans and other arthropods.

  10. Helkesimastix marina n. sp. (Cercozoa: Sainouroidea superfam. n.) a gliding zooflagellate of novel ultrastructure and unusual ciliary behaviour.

    Cavalier-Smith, Thomas; Lewis, Rhodri; Chao, Ema E; Oates, Brian; Bass, David


    Unlike Helkesimastix faecicola and H. major, Helkesimastix marina is marine, ingests bacteria, is probably also a cannibal, and differs in cell cycle ciliary behaviour. Daughter kinetids have mirror symmetry; pre-division cilia beat asymmetrically. We sequenced its 18S rDNA and studied its ultrastructure to clarify its taxonomy. Helkesimastix (Helkesimastigidae fam. n.) differs unexpectedly radically from cercomonads, lacking their complex microtubular ciliary roots, grouping not with them but with Sainouridae within Pansomonadida. Longitudinal cortical microtubules emanate from a dense apical centrosomal plate, where a striated rhizoplast attaches the nucleus, and two very short subparallel centrioles attach by dense fibres. The marginally more posterior centriole, attached to the centrosomal plate by a dense forked fibre, bears the long 9+2 gliding posterior cilium and a microtubular root; the left-side, nucleus-attached, left centriole bears an immotile ciliary stump with abnormal axoneme of nine disorganized mainly singlet microtubules, unlike the sainourid anterior papilla. Both transitional regions have a proximal lattice, the posterior centriole with slender hub. Sainouroidea superfam. n. (Sainouridae; Helkesimastigidae) have homologous cytoskeletal geometry. Dorsal Golgi dictyosome and posterior microbody are attached to the nuclear envelope, which has slender micro-invaginations and probably a cortical lattice. Bacteria are digested posteriorly in association with numerous mitochondria with flat cristae.

  11. Planomonadida ord. nov. (Apusozoa): ultrastructural affinity with Micronuclearia podoventralis and deep divergences within Planomonas gen. nov.

    Cavalier-Smith, Thomas; Chao, Ema E; Stechmann, Alexandra; Oates, Brian; Nikolaev, Sergei


    Gliding zooflagellates previously misidentified as Ancyromonas sigmoides, Metopion or Heteromita constitute a new genus Planomonas. Three new Planomonas species (marine P. micra and P. mylnikovi: freshwater P. limna) have extremely divergent 18S rRNA and subtly but consistently different light microscopic morphology, distinguishable from P. (=Ancyromonas) melba comb. nov. and P. (=Bodo) cephalopora comb. nov. Ultrastructurally, P. micra and P. mylnikovi have a sub-plasma membrane dense pellicular layer (except in the ventral feeding pocket whose rim is supported by microtubules), kinetocysts, and flat mitochondrial cristae. Centrioles, connected at approximately 80 degrees by short fibres, have a dense amorphous distal plate below a double axosome and four microtubular roots. Microbody, mitochondrion, and dictyosomes associate with the nucleus. Longitudinal cytokinesis is slow and peculiar; ciliary transformation is from anterior to posterior as in other bikonts. Planomonads, like the non-flagellate Micronuclearia (here grouped with planomonads as Hilomonadea cl. nov.), have an indistinguishable single dense pellicular layer, not a double layer like apusomonads (comprising emended class Thecomonadea, phylum Apusozoa). We also sequenced 18S rDNA for Planomonas howeae sp. nov. and Micronuclearia podoventralis, plus actin genes of P. micra, Micronuclearia, Amastigmonas marina. All were analysed phylogenetically; the Planomonas clade is ancient, diverse and robust: it sometimes groups weakly as sister to Micronuclearia.

  12. Enantioselectivity in the phytotoxicity of herbicide imazethapyr.

    Zhou, Qingyan; Xu, Chao; Zhang, Yongsong; Liu, Weiping


    Chiral compounds usually behave enantioselectively in phyto-biochemical processes. With the increasing application of chiral herbicides, their enantioselective phytotoxicity to plants merits further study, and little information is available in this area. The purpose of this study was to examine the enantioselective phytotoxicity of the herbicide imazethapyr (IM) on the roots of maize (Zea mays L.) seedlings. Enantiomers of IM were separated by HPLC, and their absolute configurations were confirmed as S-(+)-IM and R-(-)-IM by the octant rule. Plant growth measurements and morphological, microscopic, and ultrastructural observations were conducted after treatment with individual IM enantiomers and the racemate. Observations of root morphology showed that the root diameter significantly increased, whereas the root volume, surface area, and number of root tips decreased significantly. IM enantiomers selectively damaged root hair growth and significantly reduced the sloughing of border cells from the tips. IM also had adverse effects on cell organelles, such as statocytes, mitochondria, dictyosomes, and endoplasmic reticulum in maize roots. Moreover, cell membranes and cell walls were thicker than usual after IM treatment. All of the results showed the same trend that the R-(-)-IM affected the root growth of maize seedlings more severely than the S-(+)-IM. The inhibition abilities of (+/-)-IM was between S-(+)- and R-(-)-IM. The behavior of the active enantiomer, instead of just the racemate, may have more relevance to the herbicidal effects and ecological safety of IM. Therefore, enantiomeric differences should be considered when evaluating the bioavailability of the herbicide IM.

  13. Ultrastructural transformations in the cytoplasm of differentiating Hyacinthus orientalis L. pollen cells

    Elżbieta Bednarska


    Full Text Available The sequence of ultrastructural changes in the cytoplasm during the successive stages of pollen grain development in Hyacinthus orientulis pollen cells was studied. The cytoplasmic transformations of the generative cell included the elimination of plastids, increase in the number of mitochondria, assumption of a spindle shape with the aid of microtubules and the characteristic development of the vacuole system with the formation of so-called colored bodies. The cytoplasmic transformations of the generative cell encompassed changes in the plastids, which began to accumulate starch soon after the cell was formed, then released it shortly before anthesis, an increase in the number of mitochondria and an increase in the number of highly active dictyosomes just before anthesis. Changes in the structure of the border region between the differentiating pollen cells were associated mainly with the periodical appearance of a callose wall and the presence of lysosome-like bodies in the cytoplasm of the vegetative cell surrounding the generative cell. They arose soon after the disappearance of the callose wall and disappeared shortly before anthesis.

  14. Morphological characterization of the hemocytes of the pulmonate snail Biomphalaria tenagophila

    Margherita Anna Barracco


    Full Text Available The blood cells of the pulmonate snail Biomphalaria tenagophila, an important transmiter of the trematode Schistosoma mansoni in Brazil, were examined by ligth and transmission electron microscopy (TEM. Two hemocyte types were identified: hyalinocytes and granulocytes. Hyalinocytes are small young (immature, poorly spreading cells, which have a high nucleocytoplasmic ratio and are especially rich in free ribosomes. They do not appear to contain lysosome-like bodies and represent less than 10% of the circulating hemocytes. Granulocytes are larger hemocytes which readily spread on glass surface and which strongly react to the Gomori substrate, indicating the enzyme acid phosphatase usually found in lysosomes. Ultra-structurally, they contain a well-developed rough endoplasmic reticulum, dictyosomes and some some lysosome-like dense bodies. Granulocytes do not exhibit a characteristic granular aspect and the few granules observed in the cytoplasm should correspond to a lysosome system. They were named granulocytes instead of amoebocytes to use the same terminology adopted for Biomphalaria glabrata in order to make easier comparative studies. This is a preface study for more specific investigations on the functional activities of the blood cells of B. tenagophila and their interactions with the trematode parasite.

  15. A morphometric analysis of the redistribution of organelles in columella cells of horizontally-oriented roots of Zea mays

    Moore, R.


    In order to determine what structural changes in graviperceptive cells are associated with onset of root gravicurvature, the redistribution of organelles in columella cells of horizontally-oriented, graviresponding roots of Zea mays has been quantified. Root gravicurvature began by 15 min after reorientation, and did not involve significant changes in the (i) volume of individual columella cells or amyloplasts, (ii) relative volume of any cellular organelle, (iii) number of amyloplasts per columella cell, or (iv) surface area of cellular location of endoplasmic reticulum. Sedimentation of amyloplasts began within 1 to 2 min after reorientation, and was characterized by an intensely staining area of cytoplasm adjacent to the sedimenting amyloplasts. By 5 min after reorientation, amyloplasts were located in the lower distal corner of columella cells, and, by 15 min after reorientation, overlaid the entire length of the lower cell wall. No consistent contact between amyloplasts and any cellular structure was detected at any stage of gravicurvature. Centrally-located nuclei initially migrated upward in columella cells of horizontally-oriented roots, after which they moved to the proximal ends of the cells by 15 min after reorientation. No significant pattern of redistribution of vacuoles, mitochondria, dictyosomes, or hyaloplasm was detected that correlated with the onset of gravicurvature. These results indicate that amyloplasts and nuclei are the only organelles whose movements correlate positively with the onset of gravicurvature by primary roots of this cultivar of Zea mays.

  16. Morphometric analysis of epidermal differentiation in primary roots of Zea mays

    Moore, R.; Smith, H. S.


    Epidermal differentiation in primary roots of Zea mays was divided into six cell types based on cellular shape and cytoplasmic appearance. These six cell types are: 1) apical protoderm, located at the tip of the root pole and characterized by periclinally flattened cells; 2) cuboidal protoderm, located approximately 230 microns from the root pole and characterized by cuboidal cells; 3) tabular epidermis, located approximately 450 microns from the root pole and characterized by anticlinally flattened cells; 4) cuboidal epidermis, located approximately 900 microns from the root pole and characterized by cuboidal cells having numerous small vacuoles; 5) vacuolate cuboidal epidermis, located approximately 1,500 microns from the root pole and characterized by cuboidal cells containing several large vacuoles; and 6) columnar epidermis, located approximately 2,200 microns from the root pole (i.e., at the beginning of the zone of elongation) and characterized by elongated cells. We also used stereology to quantify the cellular changes associated with epidermal differentiation. The quiescent center and the apical protoderm have significantly different ultrastructures. The relative volume of dictyosomes increases dramatically during the early stages of epidermal differentiation. This increase correlates inversely with the amount of coverage provided by the root cap and mucilage.

  17. Light and electron microscopic observations in connection with the developing pistil and seed-appendix (caruncle of Ricinus communis L.

    Katherine Liszt


    Full Text Available The development of the particularly organized stigma and obturator, their fine structure, their function as well as the histological differentiation and the role of the seed-appendix i.e. the caruncle of Ricinus communis L. have been investigated in several developmental phases from the so called "gynoecial primordium" state to the ripe state, 'using the terminology introduced by S a t t 1 e r (1974. The stigma cells are characterized by dens cytoplasm, numerous vesicles mostly of ER origin, ribosomes and negatively stained mitochondria. Dilatation of ER, the appearance of electron opaque substances in it and between the plasmamembran and cell wall are frequent. The degenerating process of some stigma cells will start before the pollination because of autolysis. In the cells of the obturator and young caruncle however dictyosomes can be found more frequently than in stigma cells and the starch content of the ;plastids is remarkable. The thickening of the cell wall is connected with the function of these tissues.

  18. Morphological and Genetic Diversity of Opisthosporidia: New Aphelid Paraphelidium tribonemae gen. et sp. nov.

    Karpov, Sergey A; Tcvetkova, Victoria S; Mamkaeva, Maria A; Torruella, Guifré; Timpano, Hélène; Moreira, David; Mamanazarova, Karomat S; López-García, Purificación


    Aphelids are a poorly known group of parasitoids of algae that have raised considerable interest due to their pivotal phylogenetic position. Together with Cryptomycota and the highly derived Microsporidia, they have been recently re-classified as the Opisthosporidia, which constitute the sister group to the fungi within the Holomycota. Despite their huge diversity, as revealed by molecular environmental studies, and their phylogenetic interest, only three genera have been described (Aphelidium, Amoeboaphelidium, and Pseudaphelidium), from which 18S rRNA gene sequences exist only for Amoeboaphelidium and Aphelidium species. Here, we describe the life cycle and ultrastructure of a new representative of Aphelida, Paraphelidium tribonemae gen. et sp. nov., and provide the first 18S rRNA gene sequence obtained for this genus. Molecular phylogenetic analysis indicates that Paraphelidium is distantly related to both Aphelidium and Amoebaphelidium, highlighting the wide genetic diversity of aphelids. Paraphelidium tribonemae has amoeboflagellate zoospores containing a lipid-microbody complex, dictyosomes, and mitochondria with rhomboid cristae, which are also present in trophonts and plasmodia. The amoeboid trophont uses pseudopodia to feed from the host cytoplasm. Although genetically distinct, the genus Paraphelidium is morphologically indistinguishable from other aphelid genera and has zoospores able to produce lamellipodia with subfilopodia like those of Amoeboaphelidium. © 2016 The Author(s) Journal of Eukaryotic Microbiology © 2016 International Society of Protistologists.

  19. Subcellular compartmentation of glutathione in dicotyledonous plants

    Müller, Maria


    This study describes the subcellular distribution of glutathione in roots and leaves of different plant species (Arabidopsis, Cucurbita, and Nicotiana). Glutathione is an important antioxidant and redox buffer which is involved in many metabolic processes including plant defense. Thus information on the subcellular distribution in these model plants especially during stress situations provides a deeper insight into compartment specific defense reactions and reflects the occurrence of compartment specific oxidative stress. With immunogold cytochemistry and computer-supported transmission electron microscopy glutathione could be localized in highest contents in mitochondria, followed by nuclei, peroxisomes, the cytosol, and plastids. Within chloroplasts and mitochondria, glutathione was restricted to the stroma and matrix, respectively, and did not occur in the lumen of cristae and thylakoids. Glutathione was also found at the membrane and in the lumen of the endoplasmic reticulum. It was also associated with the trans and cis side of dictyosomes. None or only very little glutathione was detected in vacuoles and the apoplast of mesophyll and root cells. Additionally, glutathione was found in all cell compartments of phloem vessels, vascular parenchyma cells (including vacuoles) but was absent in xylem vessels. The specificity of this method was supported by the reduction of glutathione labeling in all cell compartments (up to 98%) of the glutathione-deficient Arabidopsis thaliana rml1 mutant. Additionally, we found a similar distribution of glutathione in samples after conventional fixation and rapid microwave-supported fixation. Thus, indicating that a redistribution of glutathione does not occur during sample preparation. Summing up, this study gives a detailed insight into the subcellular distribution of glutathione in plants and presents solid evidence for the accuracy and specificity of the applied method. PMID:20186447

  20. Activation of rape (Brassica napus L. embryo during seed germination. III. Ultrastructure of dry embryo axis

    Mieczysław Kuraś


    Full Text Available Mature dry winter rape (Brassica napus L., var. oleifera, cv. Górczański embryos were studied in the light and the electron microscope. Considerable modifications and regression of the cell ultrastructure were noted in the resting embryo as compared with the metabolically active cells. The degree of regression of the ultrastructure differed in the particular organs and tissues of the embryo. Of most regressed character are the cells of the storage organs - the hypocotyl and cotyledones. They are almost completely filled with protein and lipid bodies. The small spaces between them are filled with dense cytoplasm with a lobular nucleus and not numerous, difficult to identify, plastids and mitochondria. The cells of the shoot primordium and radicle, particularly of the protoderm at the boundary of the hypocotyl and root and columella of root cap have a less regressed ultrastructure. They contain less storage material, a less dense cytoplasm and nearly all cell organelles with a normal appearance. The mitochondria are quite numerous with rather large cristae. Plastids are large with characteristic infolds filled with cytoplasm and some lamellae and a few agglomerations of plastoglobules. The nucleus is lobular with distinctly double and porous nuclear envelope and uniformly dense nucleolus. These cells do not contain dictyosomes and the ER is reduced to short, mostly rough cisternae and vesicles. Cells within the columella itself are also differentiated. The least regression of ultrastructure is seen in the cells of external layers containing the most numerous and most active looking mitochondria and more ER structures. The promeristem cells are similar to those of the deeper columella layers but their mitochondria are more regressed. The cells of the lateral parts of the cap and radicle cells, distant from the promeristem are more similar to the hypocotyl cells.

  1. Ameloblastic secretion and calcification of the enamel layer in shark teeth.

    Kemp, N E


    Tooth primordia at early stages of mineralization in the sharks Negaprion brevirostris and Triaenodon obesus were examined electron microscopically for evidence of ameloblastic secretion and its relation to calcification of the enamel (enameloid) layer. Ameloblasts are polarized with most of the mitochondria and all of the Golgi dictyosomes localized in the infranuclear end of the cell toward the squamous outer cells of the enamel organ. Endoplasmic reticular membranes and ribosomes are also abundant in this region. Ameloblastic vesicles bud from the Golgi membranes and evidently move through perinuclear and supranuclear zones to accumulate at the apical end of the cell. The vesicles secrete their contents through the apical cell membrane in merocrine fashion and appear to contribute precursor material both for the basal lamina and the enameline matrix. The enamel layer consists of four zones: a juxta-laminar zone containing newly polymerized mineralizing fibrils (tubules); a pre-enamel zone of assembly of matrix constituents; palisadal zones of mineralizing fibrils (tubules); and interpalisadal zones containing granular amorphous matrix, fine unit fibrils, and giant cross-banded fibers with a periodicity of 17.9 nm. It seems probable that amorphous, non-mineralizing fibrillar and mineralizing fibrillar constituents of the matrix are all products of ameloblastic secretion. Odontoblastic processes are tightly embedded in the matrix of the palisadal zones and do not appear to be secretory at the stages investigated. The shark tooth enamel layer is considered homologous with that of other vertebrates with respect to origin of its mineralizing fibrils from the innerental epithelium. The term enameloid is appropriate to connote the histological distinction that the enamel layer contains odontoblastic processes but should not signify that shark tooth enamel is a modified type of dentine. How amelogenins and/or enamelins secreted by amelo- blasts in the shark and other

  2. A xylem sap retrieval pathway in rice leaf blades: evidence of a role for endocytosis?

    Botha, C E J; Aoki, N; Scofield, G N; Liu, L; Furbank, R T; White, R G


    The structure and transport properties of pit membranes at the interface between the metaxylem and xylem parenchyma cells and the possible role of these pit membranes in solute transfer to the phloem were investigated. Electron microscopy revealed a fibrillar, almost tubular matrix within the pit membrane structure between the xylem vessels and xylem parenchyma of leaf blade bundles in rice (Oryza sativa). These pits are involved primarily with regulating water flux to the surrounding xylem parenchyma cells. Vascular parenchyma cells contain large mitochondrial populations, numerous dictyosomes, endomembrane complexes, and vesicles in close proximity to the pit membrane. Taken collectively, this suggests that endocytosis may occur at this interface. A weak solution of 5,6-carboxyfluorescein diacetate (5,6-CFDA) was applied to cut ends of leaves and, after a minimum of 30 min, the distribution of the fluorescent cleavage product, 5,6-carboxyfluorescein (5,6-CF), was observed using confocal microscopy. Cleavage of 5,6-CFDA occurred within the xylem parenchyma cells, and the non-polar 5,6-CF was then symplasmically transported to other parenchyma elements and ultimately, via numerous pore plasmodesmata, to adjacent thick-walled sieve tubes. Application of Lucifer Yellow, and, separately, Texas Red-labelled dextran (10 kDa) to the transpiration stream, confirmed that these membrane-impermeant probes could only have been offloaded from the xylem via the xylem vessel-xylem parenchyma pit membranes, suggesting endocytotic transmembrane transfer of these membrane-impermeant fluorophores. Accumulation within the thick-walled sieve tubes, but not in thin-walled sieve tubes, confirms the presence of a symplasmic phloem loading pathway, via pore plasmodesmata between xylem parenchyma and thick-walled sieve tubes, but not thin-walled sieve tubes.

  3. 水稻受精前后胚囊内钙调素分布的变化:免疫金电镜观察%Changes of Calmodulin Distribution in the Embryo Sac of Oryza sativa Before and After Fertilization: an Immunogold Electron Microscope Study

    杨军; 赵洁; 梁世平; 杨弘远


    Changes of calmodulin (CaM) distribution in the embryo sac of rice (Oryza sativa subsp. japonica) at various stages before and after fertilization have been investigated by using immunogold electron microscopy. Before pollination, both cytoplasm and vacuoles of the egg cell, synergids and central cell were labeled by gold particles. A small amount of gold particles were localized in the nucleus, endoplasmic reticulum, mitochondria and dictyosomes. From pollination to fertilization, CaM amount increased in these cells, especially rich in the starch of amyloplasts. Increase of gold particles in the central cell began about 2 h earlier than that in the egg cell. There was no distinct difference of CaM amount between the degenerated and the persistent synergids. It is interesting to observe an obvious change of CaM distribution form during pollination and fertilization from scattered single particles to clustered particles, and back again to single particles after the fertilization finished. CaM was also localized extracellularly in the embryo sac wall as well as in the wall and intercellular space of nucellus cells. The extracellular CaM also changes in its amount and form after pollination. These results suggest that CaM, either intra- or extra-cellular, may play important roles in fertilization and zygote formation.%用胶体金免疫电镜技术观察了水稻(Oryza sativa subsp. japonica)受精前后胚囊内钙调素的分布变化.授粉后,卵细胞、助细胞和中央细胞内的钙调素较授粉前均有所增加.中央细胞内钙调素的增加要比卵细胞中约早2 h,退化助细胞与宿存助细胞之间的钙调素含量无明显差异.授粉到受精期间,钙调素的主要分布形式由分散的单颗粒转变为聚集颗粒,受精完成后再变为分散的单颗粒形式.胚囊壁及珠心细胞的细胞壁和胞间隙中也观察到钙调素的分布和数量变化.初步讨论了胞内和胞外钙调素在水稻受精与合子形成中的作用.

  4. Changes in root gravitropism, ultrastructure, and calcium balance of pea root statocytes induced by A23187

    Belyavskaya, N.

    The role for calcium in the regulation of a wide variety of cellular events in plants is well known. Calcium signaling has been implicated in plant gravitropism. A carboxylic acid antibiotic A23187 (calcimycin) has been widely used in biological studies since it can translocate calcium across membranes. Seedlings of Pisum sativum L. cv. Uladovsky germinated in a vertically oriented cylinder of moist filter paper soaked in water during 4.5 day had been treated with 10-5 M A23187 for 12 hr. Tips of primary roots of control and A23187-treated pea seedlings were fixed for electron microscopy and electron cytochemistry. Experiments with Pisum sativum 5- day seedlings placed horizontally for 4 h after treatment with 10 μM A23187 during 12 h found that the graviresponsiveness of their primary roots was lost completely (91 % of roots) or inhibited (24 +/- 6° in comparison with 88 +/- 8° in control). At ultrastructural level, there were observed distribution of amyloplasts around the nucleus, remarkable lengthening of statocytes, advanced vacuolization, changes in dictyosome structure, ER fragmentation, cell wall thinning in A23187-treated statocytes. Cytochemical study has indicated that statocytes exposed to calcimycin have contained a number of Ca-pyroantimonate granules detected Ca 2 + ions in organelles and hyaloplasm (unlike the control ones). The deposits were mainly associated with the plasma membrane. Among organelles, mitochondria were notable for their ability to accumulate Ca 2 +. In amyloplasts, a fine precipitate was predominately located in their stroma and envelope lumens. In cell walls, deposits of the reaction product were observed along the periphery and in the median zone. Localization of electron-dense granules of lead phosphate, which indicated Ca 2 +- ATPase activities in pea statocytes exposed to A23187, was generally consistent with that in untreated roots. Apart from plasma membrane, chromatin, and nucleolus components, the cytochemical reaction

  5. The excavate protozoan phyla Metamonada Grassé emend. (Anaeromonadea, Parabasalia, Carpediemonas, Eopharyngia) and Loukozoa emend. (Jakobea, Malawimonas): their evolutionary affinities and new higher taxa.

    Cavalier-Smith, T


    It is argued here that the anaerobic protozoan zooflagellate Parabasalia, Carpediemonas and Eopharyngia (diplomonads, enteromonads, retortamonads) constitute a holophyletic group, for which the existing name Trichozoa is adopted as a new subphylum. Ancestrally, Trichozoa probably had hydrogenosomes, stacked Golgi dictyosomes, three anterior centrioles and one posterior centriole: the typical tetrakont pattern. It is also argued that the closest relatives of Trichozoa are Anaeromonada (Trimastix, oxymonads), and the two groups are classified as subphyla of a revised phylum Metamonada. Returning Parabasalia and Anaeromonadea to Metamonada, as in Grassé's original classification, simplifies classification of the kingdom Protozoa by reducing the number of phyla within infrakingdom Excavata from five to four. Percolozoa (Heterolobosea plus Percolatea classis nov.) and Metamonada are probably both ancestrally quadriciliate with a kinetid of four centrioles attached to the nucleus; the few biciliates among them are probably secondarily derived. Metamonada ancestrally probably had two divergent centriole pairs, whereas, in Percolozoa, all four centrioles are parallel. It is suggested that Discicristata (Percolozoa, Euglenozoa) are holophyletic, ancestrally with two parallel centrioles. In the phylum Loukozoa, Malawimonadea classis nov. is established for Malawimonas (with a new family and order also) and Diphyllatea classis nov., for Diphylleida (Diphylleia, Collodictyon), is transferred back to Apusozoa. A new class, order and family are established for the anaerobic, biciliate, tricentriolar Carpediemonas, transferring it from Loukozoa to Trichozoa because of its triply flanged cilia; like Retortamonas, it may be secondarily biciliate--its unique combination of putative hydrogenosomes and flanged cilia agree with molecular evidence that Carpediemonas is sister to Eopharyngia, diverging before their ancestor lost hydrogenosomes and acquired a cytopharynx. Removal of

  6. 银杏小孢子囊壁发育的超微结构观察%Ultrastructural observation of the microsporangial wall in Ginkgo biloba L.

    陆彦; 郝敬超; 陈义芳; 周卫东; 程芳梅; 王莉


    本文利用透射电镜、半薄切片等技术,对银杏小孢子囊壁的发育进行了观察和研究。银杏小孢子囊壁分为表皮、内壁、中层和绒毡层。(1)对小孢子囊壁的表皮、内壁和中层细胞的观察表明,小孢子母细胞时期,这些细胞均处于活跃的代谢和合成阶段,含有大量的细胞器如线粒体、高尔基体、内质网和核糖体等;减数分裂时期细胞的细胞质浓度逐渐降低,细胞内分布有大液泡,其中表皮细胞的液泡膜上形成大量贮藏蛋白,内壁细胞的细胞壁逐渐皱缩,中层细胞纵向拉伸;有丝分裂时期,细胞的细胞质逐渐降解,内壁细胞切向壁和径向壁均出现大量乳突状纤维加厚,中层细胞解体,最后仅剩残余。(2)绒毡层细胞属于分泌型,在小孢子母细胞时期细胞内的细胞器丰富,其中质体在减数分裂过程中达到高峰;游离小孢子时期,粗糙内质网达到最大,绒毡层开始形成乌氏体,最终结合到花粉外壁,参与花粉外壁的形成;有丝分裂后期,绒毡层通过自溶的形式解体。以上结果显示,银杏的小孢子囊壁在为花粉发育提供营养和保护作用方面起着重要作用。%In this investigation, the developmental processes of microsporangial wall in Ginkgo biloba L. was studied by using transmission electron microscopy and semi-thin sections ways. The microsporangial wall of G. biloba consists of epidermis, endothecium, middle layers and tapetum. (1) At the stage of microspore mother cells, the abundant organelles, including endoplasmic reticulum, mitochondria, dictyosome, golgi vesicles and ribosome, distribute in the cells of epidermis, endothecium and middle layers. During the meiotic phase, these cells changed obviously. The cytoplasmic inclusions decreased gradually while some large vacuole appeared. In the epidermal cells, large amounts of storage protein gathered on the surface of

  7. ``Rhizogenesis in vitro'' - as a model to study microgravity biological effects

    Bulavin, Iliya

    type. Statocytes preserved their polarity in control but it was disturbed under clinorotation due to amyloplast distribution in the cytoplasm whole volume and/or their localization in the cell center. Structural rearrangements occurred similarly in statocytes under their transformation in secretory cells in control and under clinorotation. A characteristic features of the root proper meristematic cells in the control and in the experiment are central nucleus location, the great diversity of a size and a shape of mitochondria and plastids, poorly ER development, the presence of some small ER-bodies. As cells passed in the DEZ, their size enlarged but a nucleus can preserve the central location. A quantity of ER-cistern, vacuoles, and ER-bodies increased also. Dictyosomes acquired polarity and produced many Golgi vesicles. In CEZ cells, a large vacuole occupied the cell center, and the cytoplasm with organelles was on the cell periphery. So, we can conclude that under clinorotation: 1) the structure of a cap and growth zones of A. thaliana wild type and scr mutant roots formed de novo in vitro as similar to that in control; 2) a gaviperceptive apparatus formed in both objects but did not function. The obtained data allow to propose the model “Rhizogenesis in vitro” for using in spaceflight experiments to study the influence of real microgravity on the cellular differentiation and basic processes.

  8. Ontogênese, anatomia e ultra-estrutura dos nectários extraflorais de Hymenaea stigonocarpa Mart. ex Hayne (Fabaceae - Caesalpinioideae Ontogenesis, anatomy, and ultrastructure of Hymenaea stigonocarpa Mart. ex Hayne (Fabaceae - Caesalpinioideae extrafloral nectaries

    Élder Antônio Sousa Paiva


    leaf blade, more concentrated on the basal and medial thirds of each leaflet. These nectaries are embedded in the mesophyll, show secretory tissue surrounded by an endodermis, and are vascularized by xylem and phloem. EFN secretory activity was exclusively observed in young leaves. The protoderm origins the EFN secretory tissue, the ground meristem originates the endodermis and the procambium originates the vascular tissues. Secretory cells of functional EFNs showed dense cytoplasm, large nucleus, mitochondria, plastids with a poorly developed membrane system, oil drops scattered in the cytosol, dictyosome, and smooth endoplasmic reticulum segments. Secretion was released by cuticle rupture and contains polysaccharides and lipids.

  9. Aspectos ultra-estruturais dos canais secretores em órgãos vegetativos e reprodutivos de Anacardiaceae Ultra-structural aspects of secretory canals in vegetative and reproductive organs of Anacardiaceae

    Ana Paula Stechhahn Lacchia


    os canais secretores das espécies estudadas é o modo écrino de liberação da secreção.The study assessed phloem canal development and ultra-structure in shoot apices of Spondias dulcis G. Forst., phloematic canal ultra-structure in shoot apices of Tapirira guianensis Aubl., and floral canal ultra-structure and development and fruit canal ultra-structure of the latter specie. The flower and fruit canals of Anacardium humile St.Hil. were also studied ultra-structurally. The canals in shoot apices of S. dulcis show schizo-lysigenous formation and the floral canals of T. guianensis show schizogenous development. Epithelial cells of S. dulcis and T. guianensis canals have rough endoplasmic reticulum, free ribosomes, elongated plastids of several shapes with osmiophilic inclusions and dictyosomes with production of vesicles. Such organelles participate in the secretion of a heterogeneous exudate, which is comprised of hydrophilic and lipophilic substances. The epithelial cells of the fruit of A. humile present elongated plastids with circular membrane system, which are involved in the synthesis of lipophilic substances. The results of the ultra-structural analyses of the epithelial cells corroborate the results previously obtained in a histochemical study. In the histochemical study, lipophilic and hydrophilic substances were identified in the canals of T. guinanensis and S. dulcis and only lipophilic substances were identified in the canals of A. humile. Based on the ultrastructural aspects of the secretory canals of T. guianensis and S. dulcis we concluded that the plastids of the epithelial cells of the two species are different although they produce secretion of similar composition. A new record for the family is the presence of a great number of circular plastids in epithelial cells of the fruit of Anacardium humile. The pattern found in the secretory canals of the studied species is the ecrine type of secretion release.

  10. Glandular trichomes in Connarus suberosus (Connaraceae: distribution, structural organization and probable functions

    João Donizete Denardi


    Full Text Available Connarus suberosus is a typical species of the Brazilian Cerrado biome, and its inflorescences and young vegetative branches are densely covered by dendritic trichomes. The objective of this study was to report the occurrence of a previously undescribed glandular trichome of this species. The localization, origin and structure of these trichomes were investigated under light, transmission and scanning electron microscopy. Collections were made throughout the year, from five adult specimens of Connarus suberosus near Botucatu, São Paulo, Brazil, including vegetative and reproductive apices, leaves and fruits in different developmental stages, as well as floral buds and flowers at anthesis. Glandular trichomes (GTs occurred on vegetative and reproductive organs during their juvenile stages. The GTs consisted of a uniseriate, multicellular peduncle, whose cells contain phenolic compounds, as well as a multicellular glandular portion that accumulates lipids. The glandular cell has thin wall, dense cytoplasm (with many mitochondria, plastids and dictyosomes, and a large nucleus with a visible nucleolus. The starch present in the plastids was hydrolyzed during the synthesis phase, reducing the density of the plastid stroma. Some plastids were fused to vacuoles, and some evidence suggested the conversion of plastids into vacuoles. During the final activity stages of the GTs, a darkening of the protoplasm was observed in some of the glandular cells, as a programmed cell death; afterwards, became caducous. The GTs in C. suberosus had a temporal restriction, being limited to the juvenile phase of the organs. Their presence on the exposed surfaces of developing organs and the chemical nature of the reserve products, suggest that these structures are food bodies. Field observations and detailed studies of plant-environment interactions, as well as chemical analysis of the reserve compounds, are still necessary to confirm the role of these GTs as feeding

  11. Observation of ultrastructure and absorption function of colon mucosa in rats with ultra-short bowel syndrome%超短肠大鼠结肠代偿的细胞超微结构变化

    姜海平; 郭庆丰; 张海伟; 袁璐; 陈丹


    changes of intestinal epithelial cells. The absorption of colon to water, carbohydrates, and amino acid determined after 3 hours of closed perfusion of the colon with D-xylose solution and 15N-glycine on the continuous cycle of colon. Results As shown by the transmission electron microscopy, compared with the normal control group, rats in the ultra-short bowel group showed significantly decreased goblet cells on colonic mucosl surface, increased epithelial cells, longer and denser microvillus, increased area of membrane surface, increased number of cell-cell junctions, increased number of desmosome, tight junction, and gap junctions, higher development of endoplasmic reticulum and dictyosome, and increased number of mitochondria. As shown in the screening electron microscopy, compared with the normal rats, rats in the ultra-short bowl group had significantly deeper colon folds, thicker mucous membrane, increased number of bay openings, and longer and denser microvillus-like structures inside bays. The capability of water absorption was signicatnly higher in the ultra-short bowl group than in the sham group and normal control group (P = 0. 000) . The absorption rates of xylose and 15 N-glycine were also significantly higher in the ultra-short bowl group than in the control group (P < 0. 01). Conclusions The absorption capability can be compensatively increased in rats with ultra-short bowel syndrome. Decreased apoptosis of colon mucosa cells, increased absorption cells, hyperplasia of microvilli, increased area of the membrane surface,and increased number of mitochondria may constitute its material and energy bases.

  12. Structure and Development of Endosperm Transfer Cells in Wheat%小麦胚乳传递细胞发育的结构观察

    王慧慧; 王峰; 刘大同; 顾蕴洁; 王忠


    In developing wheat caryopsis,grain filling nutrients transport into the endosperm via endosperm transfer cells(ETCs).The developmental extent of ETCs is in close relation to yield and qualities of wheat.In this paper we investigated the developmental process and structural features of ETCs in wheat systematically by the combination of light microscopy and transmission electron microscopy.Main results were as follows:(1) ETCs occured in the endosperm epidermis bordering the endosperm cavity and were the first cell type histologically differentiated during endosperm development.ETCs could be divided into two subtypes: outer 1~2 layer of aleurone transfer cells and inner 1~2 layer of starchy endosperm transfer cells.(2) As caryopsis matured,the nuclei of starchy endosperm transfer cells disappeared,while the nuclei of aleurone transfer cells remained intact.(3) The development of ETCs showed obvious polarity and the pattern of temporal and spatial gradient.(4) Aleurone transfer cells had dense cytoplasm rich in rough endoplasmic reticulum,mitochondria,dictyosomes and lipid bodies;their plasma membrane wrinkled and in some region evaginated to form numerous plasmatubules.(5) Starchy endosperm transfer cells had sparse cytoplasm rich in amyloplasts and were highly vacuolated.(6) Lots of plasmodesmata penetrated into adjoining primary walls of ETCs where thickening and wall ingrowths didn't occur.(7) Mitochondria in ETCs showed polarized distribution,and most of them lied in the proximity of plasma membrane.The structural features of ETCs suggested that they may play a role in nutrients transportation into the endosperm both via apoplastic and symplastic pathway.%为从细胞学方面了解小麦产量和品质的形成机制,以扬麦5号为材料,利用光镜和透射电镜观察了小麦颖果发育过程中胚乳传递细胞的结构变化,并探讨了胚乳传递细胞的生理功能。结果表明:(1)胚乳传递细胞