Ultrastructural studies on germinating ascospores of Daldinia concentrica

1976 ◽  
Vol 54 (8) ◽  
pp. 698-705 ◽  
Author(s):  
A. Beckett
Keyword(s):  
Electron Microscope ◽  
Germ Tube ◽  
Tube Wall ◽  
Spore Wall ◽  
Wall Layer ◽  
Ultrastructural Studies ◽  
Early Stages ◽  
Ascospore Germination ◽  
Daldinia Concentrica

Ascospore germination in Daldinia concentrica has been studied using light and electron microscope techniques. Preliminary observations indicated that lipid globules were utilized during early stages of germination. Apical wall vesicles were localized during germ tube initiation and were involved in the differentiation of a filamentous germ tube. Wall synthesis occurred during germination and resulted in a new wall layer, which was different in ultratexture to the spore wall and which formed the germ tube wall. Possible implications of the concept of spore wall and vegetative wall types during germination are discussed.

Fine structure of sporangiole development in Choanephora cucurbitarum (Mucorales)

1982 ◽  
Vol 60 (11) ◽  
pp. 2313-2324 ◽  
Author(s):  
Michael T. Higham ◽  
Kathleen M. Cole
Keyword(s):  
Electron Microscopy ◽  
Germ Tube ◽  
Tube Wall ◽  
Outer Wall ◽  
Spore Wall ◽  
Wall Layer ◽  
Choanephora Cucurbitarum ◽  
Dark Staining ◽  
Granular Vesicles ◽  
Scanning Electron

Spore development was studied in Choanephora cucurbitarum by using transmission and scanning electron microscopy. Sporangioles are produced by expansion of the ampulla wall. A two-layered spore wall is then constructed within the spine-covered sporangiole wall. The outer spore wall layer is longitudinally grooved and is devoid of spines or appendages. The inner wall layer is thinner and electron transparent. During wall production, dark-staining granular vesicles were observed in the spore cytoplasm. Their contents stained similarly to the material of the outer wall layer. Mature spores possessed a third, innermost wall layer. This was identified as a new wall layer, which was continuous with the germ-tube wall of germinated spores. Released spores were observed to be contained within the sporangiole during dispersal and germination.

Ultrastructural studies of primary spores of Conidiobolus, Erynia, and related Entomophthorales

1989 ◽  
Vol 67 (9) ◽  
pp. 2576-2589 ◽  
Author(s):  
J. P. Latgé ◽  
D. F. Perry ◽  
M. C. Prévost ◽  
R. A. Samson
Keyword(s):  
Outer Layer ◽  
Germ Tube ◽  
Spore Wall ◽  
Wall Layer ◽  
Spore Formation ◽  
Dense Layer ◽  
Nuclear Ultrastructure ◽  
Ultrastructural Studies ◽  
Thin Electron ◽  
Definition Of

Wall development during primary spore formation, discharge, and germination of Entomophthorales is emphasized in ultrastructural studies of Conidiobolus, Entomophaga, Neozygites, and Erynia. In the fungi examined, spore and sporophore walls consist of a thick, electron-translucent inner layer and a thin, electron-dense outer layer. During spore formation, cytoplasm of the supporting sporophore cell migrates into the spore initial. As the former cell empties, a septum develops. Discharge is caused by inversion of the papillum, which lacks the electron-dense layer. Only in Erynia did the two spore wall layers separate upon impact. Intracytoplasmic organization of the primary spore is typical of the Zygomycotina; the morphology of organelles was characteristic of species, whereas nuclear ultrastructure was consistent within genera. Conidiobolus nuclei have a prominent nucleolus that lacks heterochromatin, in contrast with the other genera where large patches of heterochromatin were observed. Upon germination, no rupture of the spore outer layer was observed other than at points of germ tube emergence. The germ tube wall was continuous with the inner spore wall layer. The results are discussed in reference to Entomophthorales taxonomy and definition of the terms conidium and monosporous sporangiolum.

Ascospore germination, growth in culture, and imperfect spore formation in Cookeina sulcipes and Phillipsia crispata

1975 ◽  
Vol 53 (1) ◽  
pp. 56-61 ◽  
Author(s):  
J. W. Paden
Keyword(s):  
Germ Tube ◽  
Outer Wall ◽  
Wall Layer ◽  
Spore Formation ◽  
Spore Surface ◽  
No Formation ◽  
Ascospore Germination ◽  
Germ Tubes

Ascospores of Cookeina sulcipes germinate by one of two modes: (1) by the production of blastoconidia on sympodially proliferating conidiogenous cells which may arise from any point on the spore surface, and (2) by a thick polar germ tube. No ascospores were seen to germinate both ways. The conidiogenous cells are occasionally modified into narrow hyphae. The blastoconidia germinate readily but are evidently very short-lived. Ascospores of Phillipsia crispata germinate by two polar germ tubes; there is no formation of blastoconidia. In both species the inner ascospore wall separated from an outer wall layer during germination. In culture both C. sulcipes and P. crispata form arthroconidia. The arthroconidia are uninucleate; they germinate readily and reproduce the species when transferred to fresh plates.

Ultrastructural studies on exogenously dormant ascospores of Daldinia concentrica

1976 ◽  
Vol 54 (8) ◽  
pp. 689-697 ◽  
Author(s):  
A. Beckett
Keyword(s):  
Electron Microscope ◽  
Thin Sections ◽  
Enzymic Digestion ◽  
Ultrastructural Studies ◽  
Daldinia Concentrica

Exogenously dormant ascospores of Daldinia concentrica have been studied using light and electron microscope techniques. Tests have shown that ascospores are rendered non-viable after 10 min treatment with fixative. Thin sections and shadowed, chemically cleaned preparations revealed a multilayered ascospore wall, parts of which are differentiated to form a longitudinal germ fissure. A microfibrillar component is associated with the germ fissure, and enzymic digestion indicates that these fibrils could be chitin. It is also suggested that sporopollenin may be present in certain wall layers.

Unusual ascospore germination in Hypoxylon fragiforme: first seps in the establishment of an endophytic symbiosis

1990 ◽  
Vol 68 (12) ◽  
pp. 2571-2575 ◽  
Author(s):  
I. H. Chapela ◽  
O. Petrini ◽  
L. E. Petrini
Keyword(s):  
Germ Tube ◽  
Initial Step ◽  
Wall Layer ◽  
Flexible Structure ◽  
Specific Factor ◽  
Recognition Mechanism ◽  
Ascospore Germination ◽  
Host Fungus ◽  
High Degree ◽  
Rigid Shell

An unusual germination mechanism in ascospores of Hypoxylon fragiforme is described and illustrated. In this xylariaceous, endophytic fungus, germination always involved the emergence of a bivalved, flexible structure from an outer rigid shell, formed by a differentiated transparent wall layer, and resulted in the exposure of the cell body. The series of fast movements leading to the emergence of activated ascospores from their shells was termed spore eclosion. Eclosion was a necessary initial step of germination, but eclosion without germ-tube production could be obtained by cycloheximide treatment. Major changes involved in eclosion occurred within a few seconds, some minutes after discharge of ascospores onto the host material (Fagus sylvatica). We postulate the existence of a host-derived, diffusible, specific factor eliciting those changes. This sophisticated recognition mechanism indicates a high degree of specialization of H. fragiforme to its endophytic symbiosis with beech trees. Key words: eclosion, tree, Fagus, Hypoxylon, host–fungus recognition.

The fine structure of mature and germinating chlamydospores of Fusarium oxysporum

1979 ◽  
Vol 25 (7) ◽  
pp. 808-817 ◽  
Author(s):  
I. L. Stevenson ◽  
S. A. W. E. Becker
Keyword(s):  
Fusarium Oxysporum ◽  
Germ Tube ◽  
Spore Wall ◽  
Wall Layer ◽  
Close Apposition ◽  
Exterior Surface ◽  
Thin Sections ◽  
Subcellular Organelles ◽  
Innermost Layer ◽  
Rapid Appearance

A number of features not described previously has been revealed in electron-microscope studies of mature chlamydospores of Fusarium oxysporum. On the maturation of one isolate, many spores formed a thick matrix-like layer containing electron-dense particles on the exterior surface of the spore wall. In thin sections of mature chlamydospores of the same isolate, cisternae of endoplasmic reticulum surrounding, and in close apposition to, the limiting boundary of the lipid bodies were revealed.The germination of chlamydospores was accompanied by (a) the rapid appearance of polysaccharide deposits and changes in the configuration of some subcellular organelles, (b) the formation of a new wall layer between the plasma membrane and the innermost layer of the spore Wall, (c) the rupture of the outermost coats of the spore wall, and (d) the emergence of the germ tube as an extension of the new wall layer.

Ultrastructural changes during germination of Geotrichum candidum arthrospores

1973 ◽  
Vol 19 (8) ◽  
pp. 1031-1034 ◽  
Author(s):  
S. D. Steele ◽  
T. W. Fraser
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Germ Tube ◽  
Tube Wall ◽  
Geotrichum Candidum ◽  
Spore Wall ◽  
Ultrastructural Changes ◽  
Wall Material ◽  
Apparent Increase ◽  
Tube Emergence

The dormant arthrospore in Geotrichum candidum has three, possibly four, layers making up the spore wall. Nuclei, mitochondria, free ribosomes, fragments of endoplasmic reticulum, various small vacuoles, and particles of glycogen were observed within the protoplasm. During germination a new layer of wall material forms between the original spore wall and the cytoplasm. This new layer is confined to the region where germ-tube emergence occurs and is continuous with the germ-tube wall. After germ-tube emergence vesicles were seen at the apices of germlings. Another feature of germination was an apparent increase in the amount of endoplasmic reticulum, some of which appears to assume the function of the Golgi apparatus.

Surface structure of germinating Uromyces dianthi urediospores as observed by scanning electron microscope

1971 ◽  
Vol 49 (12) ◽  
pp. 2243-2244 ◽  
Author(s):  
D. R. Jones
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Structure ◽  
Germ Tube ◽  
Spore Wall ◽  
Spore Surface ◽  
Germ Pore ◽  
Tube Emergence ◽  
Scanning Electron

Germ pore regions could not be located on the surface of Uromyces dianthi urediospores before germination. Germ tube emergence did not split the spore wall. Double spine features were observed on the spore surface.

Spore wall ontogeny in Pseudoplectania nigrella and Plectania nannfeldtii (Ascomycotina, Pezizales)

1995 ◽  
Vol 73 (11) ◽  
pp. 1761-1767 ◽  
Author(s):  
Li-Tzu Li ◽  
James W. Kimbrough
Keyword(s):  
Key Words ◽  
Light Microscope ◽  
Secondary Wall ◽  
Spore Wall ◽  
Wall Layer ◽  
Ultrastructural Studies ◽  
Blue Stain ◽  
Spore Wall Ornamentation

Pseudoplectania and Plectania currently belong to the Sarcosomataceae, tribe Sarcosomateae, a group with members lacking cyanophilic spore markings (absorbing a blue stain). The two genera are morphologically similar in having blackish discoid-shaped apothecia but differ in having globose and ellipsoid spores, respectively. Ultrastructural studies show that ascospores of Pseudoplectania nigrella (Pers. ex Fr.) Fuckel lack a secondary wall layer. On the contrary, Plectania nannfeldtii Korf has secondary spore wall ornamentation that is cyanophilic under a light microscope. The data suggest retention of Pseudoplectania nigrella in the Sarcosomateae; however, the position of certain species of Plectania needs to be reevaluated. Key words: Pezizales, Plectania, Pseudoplectania, Sarcosomataceae, spore ontogeny, ultrastructure.

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