scholarly journals The Ascus Apex in Lichenized Fungi III. The Pertusaria-Type

1982 ◽  
Vol 14 (3) ◽  
pp. 205-217 ◽  
Author(s):  
Rosmarie Honegger
Keyword(s):  
Fine Structure ◽  
Side Branch ◽  
Functional Type ◽  
Electron Microscopic ◽  
Considerable Heterogeneity ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Elongation Process ◽  
Scanning Electron

AbstractOn the basis of light microscopic (LM), scanning electron microscopic (SEM) and transmission electron microscopic (TEM) investigations the Pertusaria-type of ascus is described as a particular functional type. The functionally unitunicate Pertusaria-type is characterized by its structure, staining properties, and by its particular mode of dehiscence. Tripartite ascus walls were observed in LM and TEM. The non-amyloid ascus wall is surrounded by a thin, amyloid outer layer. Both become amorphous at maturity and partly disintegrate. An apically thickened, amyloid inner layer reaches the base of the ascus. In its fine structure this amyloid inner layer resembles the material of the amyloid dome of Lecanora-type asci. It plays an important role during dehiscence and spore discharge. An elongation process was observed prior to dehiscence, at the end of which the ascus tip is situated above the hymenial surface. Dehiscence occurs by bursting or splitting of the whole ascus tip. The Pertusaria-type might represent a side-branch of evolution from bitunicate to unitunicate forms within the Lecanorales.Pertusaria-type asci are restricted to a small number of genera within the Pertusariaceae. A considerable heterogeneity in ascus structure and staining properties was observed within the Pertusariineae sensu Henssen & Jahns (1973) and Henssen (1976).

A Comparative Study of Fractographic Replicas

1974 ◽  
Vol 32 ◽  
pp. 566-567
Author(s):  
Loren Anderson ◽  
Pat Pizzo ◽  
Glen Haydon
Keyword(s):  
Electron Microscopy ◽  
Electron Microscopic Examination ◽  
Direct Examination ◽  
Electron Microscopic ◽  
Reliable Technique ◽  
Service Failures ◽  
Transmission Electron ◽  
Mode Of Failure ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Transmission electron microscopy of replicas has long been used to study the fracture surfaces of components which fail in service. Recently, the scanning electron microscope (SEM) has gained popularity because it allows direct examination of the fracture surface. However, the somewhat lower resolution of the SEM coupled with a restriction on the sample size has served to limit the use of this instrument in investigating in-service failures. It is the intent of this paper to show that scanning electron microscopic examination of conventional negative replicas can be a convenient and reliable technique for determining mode of failure.

Cellulase activity during the growth of Achlya bisexualis on glucose, cellulose, and selected polysaccharides

1978 ◽  
Vol 56 (16) ◽  
pp. 1974-1981 ◽  
Author(s):  
W. H. Miele ◽  
A. E. Linkins
Keyword(s):  
Carbon Sources ◽  
Cellulase Activity ◽  
Extracellular Enzyme ◽  
Dry Weight ◽  
Soluble Form ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Achlya Bisexualis

The antheridial strain of the dioecious water mold Achlya bisexualis was grown in chemically defined media using glucose, cellobiose, and selected polysaccharides as carbon sources. Growth and cellulase levels were measured with media containing glucose, cellobiose, and cellulose. Evaluation of cellulase activity in the medium by viscometric and reducing sugar generation assays suggests that cellulase plays a significant role in degrading cellulose for uptake and catabolism by A. bisexualis. Cellulase in glucose-grown cultures exists as a soluble extracellular enzyme complex, while in cellulose-grown cultures much of the enzyme is absorbed to the cellulose. Elution of the cellulose substrate after 96 h growth with NaCl-fortified buffer releases absorbed cellulase in a soluble form. The absorption of cellulase to the substrate and possibly the cell walls of A. bisexualis could account for the rapid loss in dry weight of A. bisexualis during culture on cellulose in a closed system. Scanning electron microscopic (SEM) examination of the walls of A. bisexualis shows disruption in cellulose cultures, which is not evident for glucose-or cellobiose-grown hyphae. Transmission electron microscopic (TEM) photomicrographs show a significant reduction in the wall thickness of cellulose-grown hyphae as compared with glucose-grown samples. This evidence suggests that the enzyme(s) produced during growth on cellulose is (are) capable of binding as an active hydrolase to walls of A. bisexualis or to the cellulosic substrate.

scholarly journals Scanning Electron Microscopic Study of Modified Chloroplasts in Senescing Broccoli Florets

HortScience ◽  
2000 ◽  
Vol 35 (1) ◽  
pp. 99-103 ◽  
Author(s):  
Hirofumi Terai ◽  
Alley E. Watada ◽  
Charles A. Murphy ◽  
William P. Wergin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Structural Changes ◽  
Freeze Fracture ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Structural changes in chloroplasts of broccoli (Brassica oleracea L., Italica group) florets during senescence were examined using light microscopy, scanning electron microscopy (SEM) with freeze-fracture technique, and transmission electron microscopy (TEM) to better understand the process of chloroplast degradation, particularly at the advanced stage of senescence. Light microscopy revealed that chloroplasts, which initially were intact and green, became obscure in shape, and their color faded during senescence. Small, colored particles appeared in cells as the florets approached the final stage of senescence and became full- to dark-yellow in color. Scanning electron microscopy showed that stroma thylakoids in the chloroplast initially were parallel to each other and grana thylakoids were tightly stacked. As senescence advanced, the grana thylakoids degenerated and formed globules. The globules became larger by aggregation as senescence progressed, and the large globules, called “thylakoid plexus,” formed numerous vesicles. The vesicles ultimately were expelled into the cytosol, and the light microscope revealed many colored particles in the senescent cells. These results indicate that the degradation of chloroplasts in broccoli florets progresses systematically, with the final product being colored particles, which are visible in yellow broccoli sepal cells.

A scanning electron microscopic method for assessing surface topography of bladders

1984 ◽  
Vol 42 ◽  
pp. 40-41
Author(s):  
Betty I. Tarnowski ◽  
Gregory R. Schonbaum
Keyword(s):  
Electron Microscopy ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Step Procedure ◽  
Critical Point Drying ◽  
Scanning Electron Microscopic ◽  
Sampling Procedures ◽  
Electron Microscopic Method ◽  
Scanning Electron ◽  
Sem Analyses

Neither light microscopy nor transmission electron microscopy lend themselves to an accurate assessment of focal changes of epithelium: both techniques are limited by sampling procedures. The same limitation, however, does not apply to scanning electron microscopy (SEM) (1,2) which permits statistically meaningful analyses on a larger number of samples. The usefulness of such an approach was explored in our studies on the induction of damage to rat urothelium by cyclophosphamide (3,4) and its prevention by adjunct therapy with 2,3-dimercaptopropane sulfonate (DMPS). Portions of the bladder were sampled from the dome, central region and trigone and the tissue was prepared for SEM by dehydration in acetone, followed by critical point drying and gold coating. SEM analyses were performed in a two-step procedure using a Novascan scanning electron microscope at low (20X) and high (100X) magnifications.

A scanning electron microscopic study of the external features of perithecium development in Sordaria humana

1983 ◽  
Vol 61 (12) ◽  
pp. 3217-3229 ◽  
Author(s):  
N. D. Read
Keyword(s):  
Pore Formation ◽  
Fruit Body ◽  
Side Branch ◽  
Developmental Sequence ◽  
Differential Growth ◽  
Electron Microscopic ◽  
Neck Extension ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

The external features of perithecium development in Sordaria humana have been examined with the scanning electron microscope. Variations in specimen preservation were evident after using different preparative procedures. Different stages of perithecium development were correlated with culture age. The developmental sequence was as follows. An ascogonial coil was initiated as a side branch of a vegetative hypha and became enclosed by enveloping hyphae originating from one or more locations. The enveloping hyphae of the resultant spherical protoperithecium gave rise to fringe hyphae and, after cohesion, to the protoperithecium peridium. The neck was first evident as a bulge on the fruit body surface. Ostiolar pore formation soon followed. Neck extension primarily involved the differentiation of periphyses, lining the ostiolar canal, into the coherent cells of the neck peridium. A positive neck phototropism resulted from the differential growth of periphyses. Neck hyphae often grew from the base of the neck peridium. Neck development was sometimes terminated by ostiolar pore occlusion. The different cellular elements observed have been classified into two basic types: (i) discrete hyphae and hyphallike elements which exhibit a pronounced longitudinal type of growth pattern; and (ii) coherent elements which arise by the cohesion of adjacent hyphae or hyphallike elements.

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