Cryo-sectioning

Cryo-ultramicrotomy (sectioning frozen material) is really only useful for small, densely cytoplasmic cells, such as those found in root tips. In this method, the sample is generally cryo-protected by infiltration of 2M sucrose after lightly fixing in glutaraldehdye. After freezing, the material is sectioned and so the method does not remove all artefacts of chemical fixation and, indeed, may introduce new ones. It is, however, useful in that it avoids any dehydration series used in a typical embedding regime necessary for sectioning, and has shown an improved immunolabelling response over resin embedded material, although the ultrastructure is not always well-preserved.