Cell wall organization of cortical parenchyma of angiosperms observed by the freeze etching technique

Naked swarmers of both Cladophora rupestris and Chaetomorpha melagonium have been examined by the freeze-etching technique. The swarmers of Cladophora, collected just after settling, reveal several layers of granules external to the plasmalemma and internal to the so-called ‘fibrous-layer’. Chaetomorpha swarmers collected just before settling show extrusion of vesicles through the plasmalemma. The structures associated with the membranes are discussed in relation to known features of these swarmers already observed by sectioning. The role of granules in the synthesis of cell wall microfibrils is strengthened though the spatial arrangement of the granules seen in this investigation does not completely fulfil the ‘ordered granule’ hypothesis. Description of, and comments on, features related to cell wall synthesis, particularly the Golgi and vacuolar systems, are given.

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Structures Formed by Cryoprotective Agents Used in Freezc-Etching

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066292 ◽

1971 ◽

Vol 29 ◽

pp. 448-449

Author(s):

G. G. Cocks ◽

C. E. Cluthe

Keyword(s):

Aqueous Solution ◽

Polyethylene Oxide ◽

Liquid Nitrogen Temperature ◽

Ice Crystals ◽

Etching Technique ◽

Structural Constituent ◽

Cryoprotective Agents ◽

Quick Freezing ◽

Freeze Etching ◽

Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

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Ultrastructure of Chlamydomonas eugametos as revealed by freeze-etching: cell wall, plasmalemma and chloroplast membrane

Journal of Ultrastructure Research ◽

10.1016/s0022-5320(74)80065-1 ◽

1974 ◽

Vol 47 (2) ◽

pp. 125-141 ◽

Cited By ~ 12

Author(s):

D.F. Bray ◽

Kazuo Nakamura ◽

J.W. Costerton ◽

E.B. Wagenaar

Keyword(s):

Cell Wall ◽

Chloroplast Membrane ◽

Chlamydomonas Eugametos ◽

Freeze Etching

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The nature of reaction wood. IV. Variations in cell wall organization of tension wood fibres

Australian Journal of Botany ◽

10.1071/bt9550177 ◽

1955 ◽

Vol 3 (2) ◽

pp. 177 ◽

Cited By ~ 53

Author(s):

AB Wardrop ◽

HE Dadswell

Keyword(s):

Cell Wall ◽

Tension Wood ◽

Secondary Wall ◽

Degree Of Crystallinity ◽

Tropical Species ◽

Normal Wood ◽

Reaction Wood ◽

Gelatinous Layer ◽

Wood Fibres ◽

Cell Wall Organization

The cell wall organization, the cell wall texture, and the degree of lignification of tension wood fibres have been investigated in a wide variety of temperate and tropical species. Following earlier work describing the cell wall structure of tension wood fibres, two additional types of cell wall organization have been observed. In one of these, the inner thick "gelatinous" layer which is typical of tension wood fibres exists in addition to the normal three-layered structure of the secondary wall; in the other only the outer layer of the secondary wall and the thick gelatinous layer are present. In all the tension wood examined the micellar orientation in the inner gelatinous layer has been shown to be nearly axial and the cellulose of this layer found to be in a highly crystalline state. A general argument is presented as to the meaning of differences in the degree, of crystallinity of cellulose. The high degree of crystallinity of cellulose in tension wood as compared with normal wood is attributed to a greater degree of lateral order in the crystalline regions of tension wood, whereas the paracrystalline phase is similar in both cases. The degree of lignification in tension wood fibres has been shown to be extremely variable. However, where the degree of tension wood development is marked as revealed by the thickness of the gelatinous layer the lack of lignification is also most marked. Severity of tension wood formation and lack of lignification have also been correlated with the incidence of irreversible collapse in tension wood. Such collapse can occur even when no whole fibres are present, e.g. in thin cross sections. Microscopic examination of collapsed samples of tension wood has led to the conclusion that the appearance of collapse in specimens containing tendon wood can often be attributed in part to excessive shrinkage associated with the development of fissures between cells, although true collapse does also occur. Possible explanations of the irreversible shrinkage and collapse of tension wood fibres are advanced.

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Recent progress in the freeze-etching technique

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1971.0042 ◽

1971 ◽

Vol 261 (837) ◽

pp. 121-131 ◽

Cited By ~ 159

Keyword(s):

High Vacuum ◽

Molecular Size ◽

Etching Technique ◽

Structural Distortions ◽

Shadow Casting ◽

Structural Details ◽

Freeze Etching ◽

The One ◽

Insight Into ◽

Made In

The freeze-etching technique must be improved if structures at the molecular size level are to be seen. The limitations of the technique are discussed here together with the progress made in alleviating them. The vitrification of living specimens is limited by the fact that very high freezing rates are needed. The critical freezing rate can be lowered on the one hand by the introduction of antifreeze agents, on the other hand by the application of high hydrostatic pressure. The fracture process may cause structural distortions in the fracture face of the frozen specimen. The ‘double-replica’ method allows one to evaluate such artefacts and provides an insight into the way that membranes split. During etching there exists the danger of contaminating the fracture faces with condensable gases. Because of specimen temperatures below —110 °C, special care has to be taken in eliminating water vapour from the high vacuum. An improvement in coating freeze-etched specimens has resulted from the application of electron guns for evaporation of the highest melting-point metals. If heat transfer from gun to specimen is reduced to a minimum, Pt, Ir, Ta, W and C can be used for shadow casting. Best results are obtained with Pt-C and Ta-W . With the help of decoration effects Pt-C shadow castings give the most information about the fine structural details of the specimen.

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The maturation of cell wall structure during germination of Bacillus polymyxa spores

Canadian Journal of Microbiology ◽

10.1139/m70-150 ◽

1970 ◽

Vol 16 (9) ◽

pp. 883-887 ◽

Cited By ~ 10

Author(s):

R. G. E. Murray ◽

Myrtle M. Hall ◽

J. Marak

Keyword(s):

Cell Wall ◽

Intermediate Layer ◽

Single Layer ◽

Regular Structure ◽

Wall Structure ◽

Bacillus Polymyxa ◽

Rectangular Array ◽

Crack Open ◽

Freeze Etching ◽

Primordial Cell

Sections of germinating spores of Bacillus polymyxa show that the primordial cell wall consists of a single layer. The intermediate layer and an outer rectangular array of macromolecules found on vegetative cells do not appear until the spore coats crack open about 60 min after initiation of germination. The initial areas of the new components appear in patches under the cracks in the coats. Within 10 min the wall is completed and takes on the profile seen in the vegetative cell. Negative staining and freeze-etching techniques show the regular structure to be identical with that previously shown for mature cells, although the subunits are more readily visible in negatively stained preparations.

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