Slow-speed freezing of chemically unfixed biological tissues and long-term storage of frozen samples for cryoscanning electron microscopy.
We describe a procedure in which plant tissue as well as a yeast culture on agar are frozen with slow cooling rates for observation of surface structures in a cryoscanning electron microscope. A system is also presented for long-term storage of frozen specimens under liquid nitrogen, in which the material is maintained for direct observation. Some small tools are described, which are essential for making preparations using slow-speed freezing and for the storage of prepared samples. Three examples of preparations with different complications are given: the "sculptures" on the surface of a leaf of Allium schoenoprasum, an early stage of flower development of Allium cernuum, and a part of an agar-grown colony of Arxula adeninivorans. In our experience, it is possible to store fully hydrated samples under the described conditions for more than a year without damaging the fine structures.
Adler
K
K
Institut für Pflanzengenetik und Kulturpflanzenforschung Gatersleben, Sachsen-Anhalt, Germany.
Kruse
J
J
Kunze
G
G
D000490:Allium / Q000648:ultrastructure; D005615:Freezing; D008855:Microscopy, Electron, Scanning; D016707:Tissue Fixation; D015003:Yeasts / Q000648:ultrastructure