scholarly journals Cytological Aspects of the Mycobiont–Phycobiont Relationship in Lichens

1984 ◽  
Vol 16 (2) ◽  
pp. 111-127 ◽  
Author(s):  
Rosmarie Honegger
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Wall Layer ◽  
Distinct Pattern ◽  
Homogeneous Material ◽  
Wall Surface ◽  
Surface Layers ◽  
Thin Sectioning ◽  
Cytological Features ◽  
Mother Cell Wall

AbstractCytological aspects of the mycobiont-phycobiont contact were investigated in the lichen species Peltigera aphthosa, Cladonia macrophylla, Cladonia caespiticia and Parmelia tiliacea by means of freeze-etch and thin sectioning techniques, and by replication of isolated fragments of myco- and phycobiont cell walls.In the symbiotic state of the mycobionts investigated a thin outermost wall layer with a distinct pattern was observed mainly in the hyphae contacting phycobiont cells and in the upper medullary layer. No comparable structures were noted on the hyphal surface of the cultured mycobionts of the Cladonia and Parmelia species investigated. A distinct rodlet layer was found on the hyphal surface of the mycobiont of Peltigera aphthosa, while mycobionts of Cladonia macrophylla, C. caespiticia and Parmelia tiliacea had a mosaic of small, irregular ridges, each corresponding in its size to a bundle of rodlets on the outermost wall layer. Comparable surface layers have been described in aerial hyphae of a great number of non-lichenized fungi.The rodlet layer of the mycobiont wall surface of Peltigera aphthosa adheres tightly to the outermost layer of the sporopollenin-containing cell wall of the Coccomyxa phycobiont. Mature trebouxioid phycobiont cells of the Cladonia and Parmelia species investigated in the symbiotic state had an outermost wall layer which was structurally indistinguishable from the tessellated surface layer of the mycobiont cells. A rodlet pattern was detected in the outermost wall layer of Trebouxia autospores still surrounded by the cellulosic mother cell wall. In mature Trebouxia cells the bundles of rodlets became increasingly covered by a homogeneous material, and thus attained the same tessellated pattern which was observed on the mycobiont wall surface. No comparable structures were found on the wall surface after culturing the Trebouxia phycobionts axenically in liquid media. Confluence of the tessellated surface layers of fungal and algal origin was noted at the contact sites of growing hyphal tips and young Trebouxia cells.The possible correlations between these cytological features and published immunological data on the cell surface of cultured and symbiotic lichen myco- and phycobionts are discussed.

scholarly journals Changes in cell ultrastructure and morphology of Arabidopsis thaliana roots after coumarins treatment

2014 ◽  
Vol 70 (3) ◽  
pp. 187-198
Author(s):  
Ewa Kupidłowska
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Root Elongation ◽  
Inhibitory Effect ◽  
Cell Ultrastructure ◽  
Radial Expansion ◽  
Elongation Zone ◽  
Cortical Cells ◽  
Mother Cell Wall

The ultrastructure and morphology of roots treated with coumarin and umbelliferone as well as the reversibility of the coumarins effects caused by exogenous GA, were studied in <em>Arabidopsis thaliana</em>. Both coumarins suppressed root elongation and appreciably stimulated radial expansion of epidermal and cortical cells in the upper part of the meristem and in the elongation zone. The gibberellic acid applied simultaneously with coumarins decreased their inhibitory effect on root elongation and reduced cells swelling.Microscopic observation showed intensive vacuolization of cells and abnormalities in the structure of the Golgi stacks and the nuclear envelope. The detection of active acid phosphatase in the cytosol of swollen cells indicated increased membrane permeability. Significant abnormalities of newly formed cell walls, e.g. the discontinuity of cellulose layer, uncorrect position of walls and the lack of their bonds with the mother cell wall suggest that coumarins affected the cytoskeleton.

Comparative ultrastructure of selected oral streptococci: thin-sectioning and freeze-etching studies

1976 ◽  
Vol 22 (4) ◽  
pp. 475-485 ◽  
Author(s):  
Stanley C. Holt ◽  
E. R. Leadbetter
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Cytoplasmic Membrane ◽  
Close Association ◽  
Oral Streptococci ◽  
Outermost Layer ◽  
Thin Sectioning ◽  
Freeze Etching ◽  
Comparative Ultrastructure ◽  
Crystalline Array

The ultrastructure of Streptococcus mutans, serotypes a–e, S. sanguis, S. mitis, and S. salivarius HHT, were examined by the techniques of thin-sectioning and freeze-etching. The cell walls varied in width between 15 and 46 nm and were covered with an electron-dense fibrillar or fuzz layer. The cytoplasmic membrane was in close association with numerous mesosomes which were, in turn, either closely associated or in contact with the bacterial chromosome. In freeze-etch replicas, the outermost layer of the cell wall was fibrous, and the cytoplasmic membrane was covered with particles composed of several subunits. Both particle-clusters and particle-free areas occurred on the surfaces of the cytoplasmic membrane, as well as a crystalline array in the ground plasm of the cell.

Surface charge and morphogenesis of regular arrays of macromolecules on bacterial cell walls

1978 ◽  
Vol 36 (2) ◽  
pp. 346-347 ◽  
Author(s):  
U. B. Sleytr ◽  
G. P. Friers
Keyword(s):  
Cell Wall ◽  
Surface Charge ◽  
Bacterial Cell ◽  
Cell Walls ◽  
Surface Layers ◽  
Regular Surface ◽  
Wide Range ◽  
Freeze Etching ◽  
Regular Arrays ◽  
Peptidoglycan Layer

Regular arrays of macromolecules can be demonstrated on the surface of a wide range of bacteria by negative staining and freeze-etching techniques. The isolated subunits of the regular surface layers (S-layers) examined in this study have shown to consist of protein or glycoprotein and to possess the ability to assemble spontaneously under certain conditions to form regular arrays with the same dimensions as those seen on intact bacteria. In appropriate conditions the isolated subunits reattach to the cell wall from which they have been removed. Analysis of the orientation of the reconstituted S-layers have shown that the pattern of the regular arrays seem to be determined only by the directional bonds between the subunits and not by any order in the underlying (peptidoglycan) layer.

scholarly journals On a Malay Form of Chlorococcum humicola (Näg.), Rabenh

1919 ◽  
Vol 44 (299) ◽  
pp. 473-482 ◽  
Author(s):  
B. Muriel Bristol
Keyword(s):  
Cell Wall ◽  
Mother Cell ◽  
Cell Walls ◽  
Starch Granules ◽  
Red Pigment ◽  
Vegetative Cells ◽  
Daughter Cells ◽  
Set Up ◽  
Mother Cell Wall ◽  
Adult Cells

Summary The material described has been obtained from cultures of a sample of dried soil, which was sent from the Malay States about two years before the cultures were set up. The vegetative cells are spherical or subspherical, solitary or collected together into mucilaginous strata, very variable in size, being from 20–80 μ in diameter, each with a thin cellulose cell-wall and a single parietal chloroplast containing from one to several pyrenoids and numerous starch granules. In adult cells a quantity of yellow oil is stored, in which a bright red pigment is often dissolved. The cytoplasm is reticulate. The young cells contain a single minute nucleus and one pyrenoid, both of which multiply by repeated division so that the adult cells are cœnocytic with many pyrenoids. Propagation takes place, by successive bipartition of the contents of the mother-cell, into 8–16 or numerous biciliate zoogonidia which may develop asexually or may act as facultative gametes. In both cases direct development into vegetative cells takes place. Aplanospore-formation may also take place, preceded by the multiplication by constriction of the nuclei of the mother-cell. The aplanospores remain imbedded in a mucous stratum, and enter into a palmelloid state in which further bipartitions may take place. Eventually, the palmelloid cells either acquire cilia and behave as normal zoogonidia or they develop directly into vegetative cells. True vegetative division does not take place, but the cell-contents may divide into two daughter-cells which immediately acquire new cell-walls and are set free as vegetative cells by the dissolution of the mother-cell-wall. Chloroaoccum humicola, differing in no essential particulars from that in the Malay soil, has been found to occur almost universally in English soils. The limit of its resistance against desiccation and of its retention of vitality has been shown, by investigations on long-dried English soils, to lie somewhere between seventy and eighty years. In conclusion, I wish to express my thanks to Professor G. S. West for his valuable help throughout this work.

Chemical and ultrastructural studies on the distribution of sporopolleninlike biopolymers in six genera of lichen phycobionts

1985 ◽  
Vol 63 (12) ◽  
pp. 2221-2230 ◽  
Author(s):  
Ueli Brunner ◽  
Rosmarie Honegger
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Resistant Cell ◽  
Wall Layer ◽  
Conclusive Evidence ◽  
The Other ◽  
Chemical Methods ◽  
Ultrastructural Studies ◽  
Cell Wall Polymer ◽  
Infrared Absorption Spectra

Cell walls of cultured lichen phycobionts of the genera Coccomyxa, Elliptochloris, Myrmecia, Pseudochlorella, Trebouxia, and Trentepohlia were investigated with cytological and chemical methods with regard to the presence or absence of trilaminar sheaths and (or) resistant biopolymers. Trilaminar cell wall layers occurred in Coccomyxa, Elliptochloris, Myrmecia, and (less distinctly) Pseudochlorella species. A biopolymer highly resistant to nonoxidative degradation by phosphoric acid occurred only in the isolated and vigorously extracted cell walls of Coccomyxa and Elliptochloris species. The walls of all the other phycobionts, including Myrmecia and Pseudochlorella, were totally degraded, showing that a trilaminar wall layer is not conclusive evidence for the presence of a resistant cell wall polymer. The infrared absorption spectra of the degradation-resistant cell wall polymer of Coccomyxa and Elliptochloris species were not fully identical with those of natural sporopollenins. When the widely used, but chemically less appropriate acetolysis method was applied to either entire cells or isolated but not fully extracted cell walls of Coccomyxa, Elliptochloris, Myrmecia, Pseudochlorella, Trebouxia, and Trentepohlia species, they all yielded acetolysis-resistant residues whose infrared spectra resembled natural sporopollenin.

Ontogeny and fine structure of effective root nodules of the autumn olive (Elaeagnus umbellata)

1987 ◽  
Vol 65 (1) ◽  
pp. 80-94 ◽  
Author(s):  
William Newcomb ◽  
Dwight Baker ◽  
John G. Torrey
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Root Nodules ◽  
Freeze Fracture ◽  
Wall Layer ◽  
Void Space ◽  
Elaeagnus Umbellata ◽  
Autumn Olive ◽  
Clear Area ◽  
Glycogen Particles

An ultrastructural study of effective root nodules of the autumn olive (Elaeagnus umbellata Thunb.) demonstrated the presence of hyphal and vesicular forms of the actinomycete endophyte. No sporangial forms of the endophyte were observed within these nodules. The hyphae contained septa, prominent nucleoid regions, and many ribosomes. The endophytic vesicles were initially nonseptate and then became multichambered as a result of the inward growth of complete and incomplete septa. Glycogen particles were numerous in nonseptate and early stages of septate endophytic vesicle formation and in adjacent hyphae but were absent in more developed stages of septate endophytic vesicles. The endophytic vesicles also contained prominent nucleoid areas, vesicular mesosomes, and crystalline-like striated bodies. A capsule, probably derived from host Golgi cisternae and profiles of dilated rough endoplasmic reticulum, surrounded both forms of the endophyte. The endophytic vesicle cell walls consisted of an outer layer continuous with the hyphal cell wall, a middle clear area or “void space,” and an electron-dense inner layer. The “void space” of the endophyte cell wall was resolved into many thin laminae by freeze–fracture microscopy. The laminae were presumed to be different from the outermost cell wall layer because they were washed out in the solvents used in preparing specimens for the TEM.

scholarly journals The cell wall of the pollen mother cell at the tetrad stage in Convallaria majalis L.

2014 ◽  
Vol 56 (1) ◽  
pp. 73-76
Author(s):  
Maria Charzyńska ◽  
Iwona Pannenko
Keyword(s):  
Cell Wall ◽  
Pollen Mother Cell ◽  
Light Microscope ◽  
Mother Cell ◽  
Cell Walls ◽  
Fluorescence Technique ◽  
Tetrad Stage ◽  
Pas Reaction ◽  
Convallaria Majalis ◽  
Mother Cell Wall

The cell wall at the tetrad stage in <em>Convallaria majalis</em> L. has been studied by light microscope histochemical techniques. The standard PAS reaction has shown the persistence of the primary pecto-cellulosic pollen mother cell wall localized around the callosic special wall (determined both by Bauer's reaction and the fluorescence technique with aniline blue) of individual tetrcds. A PAS-positive spore precursor wall (primexime) is formed while the tetrad of microspores is still enclosed by intact callose and pollen mother cell walls. The pecto-cellulosic wall and callose layer dissolve simultaneously to release the microspores into another loculi.

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