The pattern of colony development and the formation of the uredinium of Uromyces viciae-fabae on Vicia faba

1987 ◽  
Vol 65 (10) ◽  
pp. 1998-2006 ◽  
Author(s):  
A. Beckett ◽  
A. M. Woods
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Extracellular Matrix ◽  
Low Temperature ◽  
Host Cells ◽  
Colony Development ◽  
Colloidal Iron ◽  
Thin Sections ◽  
Temperature Scanning ◽  
Scanning Electron

Low-temperature scanning electron microscopy of frozen-hydrated specimens and transmission electron microscopy of cytochemically stained thin sections and enzymically digested samples have been used to study the pattern of colony development from the initial infection in the substomatal chamber of the leaf to the production of urediniospores within uredinia. Rapid immobilization of leaf samples by freezing enables them to be fractured, revealing information on internal structural relationships between intercellular hyphae and host cells. Extracellular matrix substances, which are well preserved by low-temperature scanning electron microscopy, play an important role in the cohesion of hyphae during the early stages of uredinium formation. Cytochemical staining indicates the presence of two such matrix materials: (i) colloidal iron-negative matrix surrounding intercellular hyphae, forming a pad between adjacent hyphal cells and (ii) a colloidal iron-positive matrix between hyphal and host cell walls. A positive reaction with colloidal iron indicates acidic mucopolysaccharides. Enzymic digestion with pronase and the staining reaction with silicotungstic acid – chromic acid suggests that a glycoprotein is present in the matrix surrounding intercellular hyphae. Possible roles for the extracellular matrix, including hyphal cohesion, cell–cell communication, and protection against desiccation, are discussed.

The surface of Erysiphe graminis and the production of extracellular material at the fungus – host interface during germling and colony development

1995 ◽  
Vol 73 (2) ◽  
pp. 272-287 ◽  
Author(s):  
T. L. W. Carver ◽  
B. J. Thomas ◽  
S. M. Ingerson-Morris
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Erysiphe Graminis ◽  
Colony Development ◽  
Extracellular Material ◽  
Fungal Enzymes ◽  
Temperature Scanning ◽  
Germ Tubes ◽  
Scanning Electron

Low temperature scanning electron microscopy was used to study the development of Erysiphe graminis DC f.sp. avenae Marchal from germination through infection to sporulation of the fungal colony. To clarify resolution of the fungus–host interface and facilitate interpretation of fungal surface structures, epicuticular waxes were removed from host leaves before inoculation. Whereas conidia were covered in spinelike protrusions or globular bodies, young germ tubes, appressoria, and hyphae were initially smooth walled, but by 15 h after inoculation, wartlike bodies, resembling globular bodies on conidia, were present on first appressorial lobes; these increased in number, eventually covering the appressorium surface and appearing on contiguous hyphae. Wartlike bodies also appeared at junctions of hyphal branches, on hyphal appressoria, and on conidiophore basal cells. Their function, if any, is unknown. The meristematic zone, at the apex of the conidiophore basal cell, remained smooth walled, but globular bodies appeared on the wall of young conidia as soon as the limiting septum had formed. Observations with the fungus in situ revealed the presence of amorphous extracellular material around primary germ tubes and appressorial lobes. Extracellular material was also present beneath appressorial germ tubes and hyphae but it was hidden unless the fungus was displaced. It could not be seen beneath conidia. The extracellular material appeared to be adhesive, sticking the fungus firmly to the host surface. Removal of the fungus showed that the extracellular material was deposited close to the tip of developing germ tubes and hyphae. It was particularly thick around primary germ tubes and appressorial lobes, and a discrete ring of extracellular material was often visible around penetration pores (holes in the leaf surface seen beneath primary germ tubes and appressorial lobes). In addition to its adhesive properties, the extracellular material may act as a matrix in which fungal enzymes are sited and focused for attack on the host. Key words: Erysiphe graminis, low temperature scanning electron microscopy, extracellular material, fungal adhesion, fungal surface morphology.

Intracellular structures of rapid frozen biological samples observed by high-resolution low-temperature Scanning Electron Microscopy

1989 ◽  
Vol 47 ◽  
pp. 736-737
Author(s):  
T. Inoué ◽  
H. Koike
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Liquid Nitrogen ◽  
Specimen Preparation ◽  
Chemical Fixation ◽  
Brown Adipose ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) is useful to avoid artifacts such as deformation and extraction, because specimens are not subjected to chemical fixation, dehydration and critical-point drying. Since Echlin et al developed a LTSEM, many techniques and instruments have been reported for observing frozen materials. However, intracellular structures such as mitochondria and endoplasmic reticulum have been unobservable by the method because of the low resolving power and inadequate specimen preparation methods. Recently, we developed a low temperature SEM that attained high resolutions. In this study, we introduce highly magnified images obtained by the newly developed LTSEM, especially intracellular structures which have been rapidly frozen without chemical fixation.[Specimen preparations] Mouse pancreas and brown adipose tissues (BAT) were used as materials. After the tissues were removed and cut into small pieces, the specimen was placed on a cryo-tip and rapidly frozen in liquid propane using a rapid freezing apparatus (Eiko Engineering Co. Ltd., Japan). After the tips were mounted on the specimen stage of a precooled cryo-holder, the surface of the specimen was manually fractured by a razor blade in liquid nitrogen. The cryo-holder was then inserted into the specimen chamber of the SEM (ISI DS-130), and specimens were observed at the accelerating voltages of 5-8 kV. At first the surface was slightly covered with frost, but intracellular structures were gradually revealed as the frost began to sublimate. Gold was then coated on the specimen surface while tilting the holder at 45-90°. The holder was connected to a liquid nitrogen reservoir by means of a copper braid to maintain low temperature.

Criteria for the evaluation of low-temperature Scanning Electron Microscopy

1986 ◽  
Vol 44 ◽  
pp. 902-903
Author(s):  
Alan Beckett
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Conformational Changes ◽  
Chemical Vapour ◽  
List Type ◽  
Dimensional Changes ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) has been evaluated with special reference to its application to the study of morphology and development in microorganisms. A number of criteria have been considered and have proved valuable in assessing the standard of results achieved. To further aid our understanding of these results, it has been necessary to compare those obtained by LTSEM with those from more conventional preparatory procedures such as 1) chemical fixation, dehydration and critical point-drying; 2) freeze-drying with or without chemical vapour fixation before hand.The criteria used for assessing LTSEM for the above purposes are as follows: 1)Specimen immobilization and stabilization2)General preservation of external morphology3)General preservation of internal morphology4)Exposure to solvents5)Overall dimensional changes6)Cell surface texture7)Differential conformational changes8)Etching frozen-hydrated material9)Beam damage10)Specimen resolution11)Specimen life

scholarly journals Low-temperature scanning electron microscopy in fungus-nematode interaction

Scanning ◽  
1993 ◽  
Vol 15 (1) ◽  
pp. 37-42 ◽  
Author(s):  
E. Den Belder ◽  
A. Boekestein ◽  
J. W. J. Van Esch ◽  
F. Thiel
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Temperature Scanning ◽  
Scanning Electron
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