Cyst and germ tube wall structure in Aphanomyces astaci, Oomycetes

1978 ◽  
Vol 24 (11) ◽  
pp. 1296-1299 ◽  
Author(s):  
Lars Nyhlén ◽  
Torgny Unestam
Keyword(s):  
Alkaline Hydrolysis ◽  
Cyst Wall ◽  
Germ Tube ◽  
Tube Wall ◽  
Amorphous Layer ◽  
Wall Structure ◽  
Wall Surface ◽  
Aphanomyces Astaci ◽  
Shadow Casting ◽  
Staining Techniques

Aphanomyces astaci secondary cyst walls and walls of germinating spores were prepared by alkaline hydrolysis, autolysis, sonication, and enzymic degradation and were examined by shadow-casting and negative-staining techniques. The cyst wall consists of randomly oriented fibrils, about 3 nm in diameter. The fibrils are embedded in, or covered by, amorphous β-1,3-glucans which can easily be removed by alkaline hydrolysis. The germ tube wall surface has the same structure, but the amorphous layer is less easily removed.

scholarly journals THE FINE STRUCTURE OF ACANTHAMOEBA CASTELLANII (NEFF STRAIN)

1969 ◽  
Vol 41 (3) ◽  
pp. 786-805 ◽  
Author(s):  
Blair Bowers ◽  
Edward D. Korn
Keyword(s):  
Golgi Complex ◽  
Cyst Wall ◽  
Matrix Material ◽  
Acanthamoeba Castellanii ◽  
Dry Weight ◽  
Amorphous Layer ◽  
Wall Structure ◽  
Weight Protein ◽  
Granular Matrix ◽  
Mature Cyst

Encysting cells of Acanthamoeba castellanii, Neff strain, have been examined with the electron microscope. The wall structure and cytoplasmic changes during encystment are described. The cyst wall is composed of two major layers: a laminar, fibrous exocyst with a variable amount of matrix material, and an endocyst of fine fibrils in a granular matrix. The two layers are normally separated by a space except where they form opercula in the center of ostioles (exits for excysting amebae). An additional amorphous layer is probably present between the wall and the protoplast in the mature cyst. Early in encystment the Golgi complex is enlarged and contains a densely staining material that appears to contribute to wall formation. Vacuoles containing cytoplasmic debris (autolysosomes) are present in encysting cells and the contents of some of the vacuoles are deposited in the developing cyst wall. Lamellate bodies develop in the mitochondria and appear in the cytoplasm. Several changes are associated with the mitochondrial intracristate granule. The nucleus releases small buds into the cytoplasm, and the nucleolus decreases to less than half its original volume. The cytoplasm increases in electron density and its volume is reduced by about 80%. The water expulsion vesicle is the only cellular compartment without dense content in the mature cyst. The volume fractions of lipid droplets, Golgi complex, mitochondria, digestive vacuoles, and autolysosomes have been determined at different stages of encystment by stereological analysis of electron micrographs. By chemical analyses, dry weight, protein, phospholipid, and glycogen are lower and neutral lipid is higher in the mature cyst than in the trophozoite.

Encystment and germination of the parasitic chytrid Rozella allomycis on host hyphae

1973 ◽  
Vol 51 (10) ◽  
pp. 1825-1835 ◽  
Author(s):  
Abraham A. Held
Keyword(s):  
Cyst Wall ◽  
Germ Tube ◽  
Light And Electron Microscopy ◽  
Multivesicular Bodies ◽  
Cell Periphery ◽  
General Sequence ◽  
Obligate Intracellular ◽  
Host Cytoplasm ◽  
Intracellular Parasites ◽  
Three Stages

Zoospores of the obligately parasitic chytrid Rozella allomycis which settle upon hyphae of the water mold host, Allomyces arbuscula, encyst and germinate before their protoplasts penetrate into the host cytoplasm. This process has been examined by light and electron microscopy. Three stages which follow the attachment to the host and the retraction of the zoospore's flagellum are described: (1) the early cyst lacks a wall; it is discoid, and its shape is maintained by the coil of the retracted axoneme which forms its rim; (2) a cyst wall is formed while multivesicular bodies occur at the cell periphery and eventually disappear; a germ tube starts to grow at the point of attachment; and (3) the firm-walled cyst is spheroidal; it has a fully developed germ tube with a specialized class of vesicles; it also forms a distal, flattened vacuole whose swelling eventually injects the Rozella protoplast into the host; at this stage the retracted axoneme has disappeared and the cell's organelles have undergone extensive changes. Electron-dense, "gamma-like" granules enclosed in vacuoles may play a major role in the formation of both the cyst wall and the distal vacuole. These granules appear to give rise to small vesicles, and thus to multivesicular bodies; the distal vacuole appears to form by coalescense of gamma-like vacuoles.The general sequence of encystment and germination resembles that found in other Chytridiomycetes, both saprophytic and parasitic. However, the distal vacuole and the vesicles in the germ tube appear to be parasitic adaptations and are shared by obligate intracellular parasites from several unrelated groups of zoosporic fungi.

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 Aspects of Encystation and Cyst-Germination in Phytophthora Parasitica

1971 ◽  
Vol 9 (1) ◽  
pp. 175-191
Author(s):  
D. E. HEMMES ◽  
H. R. HOHL
Keyword(s):  
Cyst Wall ◽  
Germ Tube ◽  
Average Length ◽  
Cell Periphery ◽  
Phytophthora Parasitica ◽  
Cell Organelles ◽  
Wall Formation ◽  
Third Stage ◽  
Germ Tubes ◽  
Mature Cyst

Encystation in Phytophthora parasitica can be divided into 3 stages. In the first, the zoospores line their peripheries with flattened vesicles and fibrillar vacuoles in preparation for encystation. In the second stage, as the zoospores round up and shed their flagella, an initial wall is produced which takes the form of the mature cyst wall in thickness, but not in density. The participation of the flattened vesicles and fibrillar vacuoles in the formation of this initial wall is suggested by the disappearance of these organelles concomitant with wall formation. The third stage involves the maturation of the cyst wall and occurs only after dictyosomes produce vesicles which move to the cyst periphery and fuse to the plasmalemma. Germ tubes are formed in direct and indirect germination and involve the evagination of the plasmalemma and cyst wall proximal to an accumulation of dictyosome-derived vesicles. These vesicles remain at the germ-tube tip as it extends. In indirect germination the germ tube stops after having attained an average length of 6 µm and the vesicles appear to fuse at the hyphal apex, thus forming a cap. Lomasomes do not appear to be cell organelles with a specific function such as well synthesis, but rather seem to represent aggregations of excess membranous material that have formed as a result of the discharge of vesicles at the cell periphery during wall formation. When dictyosome vesicles are inhibited from forming and moving toward the cell periphery, lomasomes are not formed.

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.

Ultrastructure of the Host-Parasite Relationships of Pseudoperonospora humuli on Hops

1977 ◽  
Vol 25 (6) ◽  
pp. 585 ◽  
Author(s):  
RD Pares ◽  
AD Greenwood
Keyword(s):  
Leaf Tissue ◽  
Host Cells ◽  
Wall Structure ◽  
Infected Leaf ◽  
Cell Penetration ◽  
Pseudoperonospora Humuli ◽  
Host Cell Wall ◽  
Staining Techniques ◽  
Host Parasite ◽  
Infected Leaf Tissue

Infected leaf tissue was examined at 3, 4, 5 and 6 days after inoculation, after different fixing and staining techniques. One example of stomata1 penetration was seen. Examples of cell penetration and haustorium development were examined in detail. Haustoria penetrate host cells by altering host cell wall structure, and lomasomes are frequently present in the haustorium neck. Haustoria do not have nuclei and in early stages have abundant mitochondria that gradually decrease in number as infection advances.

Evaluation of surface processes in the PALM model system 6.0 for a real urban environment: a case study in Dejvice, Prague

2021 ◽  
Author(s):  
Matthias Sühring ◽  
Jaroslav Resler ◽  
Pavel Krc
Keyword(s):  
Surface Temperature ◽  
Urban Environment ◽  
Hot Spot ◽  
Radiative Transfer Model ◽  
Wall Structure ◽  
Transfer Model ◽  
Wall Surface ◽  
Physical Processes ◽  
Radiative Processes ◽  
Synoptic Conditions

<p>In recent years, the the Large-eddy simulation (LES) model PALM has been rapidly developed its capability to simulate physical processes within urban environments. For example, this includes energy-balance solvers for building and land surfaces, a radiative transfer model to account for multiple reflections and shading, a plant-canopy model to consider the effects of plants on flow (thermo-)dynamics, and a chemistry transport model, as well as nesting capabilities that enable “hot-spot” analysis, to name a few.</p> <p>This contribution provides an evaluation of modeled meteorological as well as ground and wall-surface quantities against dedicated in-situ measurements taken in an urban environment in Dejvice, Prague. Measurements included monitoring of surface temperature and wall heat fluxes. Simulations were performed for multiple days during several summer and winter episodes, characterized by different atmospheric conditions. To consider time-evolving synoptic conditions, boundary conditions were obtained from mesoscale WRF simulations.</p> <p>For the simulated episodes, the resulting temperature and wind speed within street canyons show a realistic representation of the observed state, except that the LES did not adequately capture night-time cooling near the surface in some scenarios. At most of the evaluation points, the simulated surface temperature reproduces the observed surface temperature reasonably well, for both, absolute and daily amplitude values. However, especially for the winter episodes and for modern buildings with multi-layer wall structure, the heat transfer through the walls is not well captured in some cases, leading to discrepancies between the modeled and observed wall-surface temperature. Moreover, we also show that the model performance with respect to the observations strongly depends on the accuracy of the input data. To name a few, this includes e.g. the prescribed initial soil moisture, the given leaf-area densities to account for correct shading, or if a facade is insulated or not. Additionally, we will point out current model limitations, particularly implications accompanied by the step-like topography on the Cartesian grid, or wide glass facades that are not fully represented in terms of radiative processes.</p> <p>With our findings we are able to evaluate the representation of physical processes in PALM, while also pointing out specific shortcomings.</p>

The nature of reaction wood. VII. Lignification in reaction wood

1963 ◽  
Vol 11 (2) ◽  
pp. 107 ◽  
Author(s):  
G Scurfield ◽  
. Wardrop.A.B
Keyword(s):  
Direct Methods ◽  
Growing Season ◽  
Liquidambar Styraciflua ◽  
Wall Structure ◽  
Reaction Wood ◽  
Grevillea Robusta ◽  
Gelatinous Layer ◽  
Wood Fibres ◽  
Staining Techniques ◽  
Maximum Expression

Lignification of reaction wood, caused to form in the stems of seedlings of Trisrania conferta K.Br., Grevillea robusta A.Cunn., Eucalyptus botryoides Sm., E. Melliodora A.Cunn. ex Schau., Hakea laurina R.Br., and Liquidambar styraciflua L., has been investigated with the use of ultraviolet microscopy and staining techniques. The polarizing microscope was used in a supplementary study of cell wall structure. The "gelatinous" layer of reaction wood fibres undergoes lignification, the extent depending on whether the fibres are located in the middle or on the edges of areas of reaction wood. There is evidence for the diffusion outwards into the "gelatinous" layer of breakdown products of cell protoplasts. As the growing season advances, there is a progressive reduction in the number of cambium cells dividing to form reaction wood fibres. This process reaches its maximum expression in the deciduous species Liquidambar styraciflua, where there is a complete change-over to the production of normal cells at the end of the growing season. The anatomical features of three areas of reaction wood caused to form in stems of Tristania conferta and Eucalyptus melliodora by orientating horizontally growing plants twice through 180° are described. They further emphasize the importance of the location of individual reaction wood cells in the stem in determining the structure of their walls and the pattern of wall lignification. The results of staining sections for the enzyme peroxidase with benzidinehydrogen peroxide are described. They point to the need for closer investigation by direct methods of enzyme isolation and estimation.

Sign in / Sign up

Export Citation Format

Share Document