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| Cross Sections of Lichens and Mosses |
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With a little practice it is possible to obtain cross sections of satisfactory thickness by manual cutting. There is no need to buy an expensive microtom. Only a razor blade (cut in half), a stereomicroscope and PEG 1500 (polyethylenglycol) as embedding medium is needed. Begin with the dry material. Prior to cutting the dry material is placed into a 20 % aqueous solution of PEG 1500 for 24 h. Then the wet, with PEG-solution saturated, leaf or a part from it is laid on a slide. Allow to dry for 24 h. After that the material is impregnated with PEG and at the same time it is pasted a bit onto the slide. Now we can start the cutting under the stereomicroscope. The left forefinger is laid on the material and once a relative broad piece is cut off along the fingertip. In this way a straight cutting edge is obtained and from this you begin. The left forefinger is now withdrawn a little bit or you just push the razor blade a bit tighter to your fingertip. Then cut off the thin section by moving the razor blade along your fingertip. A little practice is still needed and with the time you will develop a certain sensitiveness. The sections are transferred into a 10 % solution of PEG 1500. This is to avoid a too quick dissolving of the PEG that could damage the section. Cross sections of lichens can be enclosed in Euparal without any staining. When dealing with mosses you might want stain the section and in this case the section investigated directly in water. Literature concerning the embedding in PEG can be found here: Halle W (1959): Die Verwendung von wasserlöslichen Polywachsen als Einbettungsmittel in der histochemischen und histologischen Technik. Mikrokosmos Band 48, Seite 275 Türler S (1972): Ein ideales Einbettungsmittel? Erfolge und Schwierigkeiten mit Polyäthylenglykol. Mikrokosmos Band 61, Seite 91 Theiler R (1973): Polyäthylenglykol als Hilfsmittel beim Gefrierschneiden. Mikrokosmos Band 62, Seite 59 Krauter D (1979): Das Kosmos-Mikrotom. 3. Wahl der Objekte. Durchtränkung mit Paraffin oder Polyäthylenglykol. Mikrokosmos Band 68, Seite 144 Jentzen A (1988): Erfahrungen mit Histowachs. Mikrokosmos Band 77, Seite 57 Pareto A (1989): Rasches Einbettungsverfahren für krautige Pflanzenteile in Polyäthylenglykol. Mikrokosmos Band 78, Seite 255 Pareto A (1989): Polyethylenglykol als besonders gut geeignetes Einbettungsmedium für trockene Samenschalen von Leguminosen. Mikrokosmos Band 78, Seit 337 Gruber M (1989): Einbettung von Pflanzenteilen in Polyethylenglykol. Herstellung von perfekten Dünnschnitten mit dem Handmikrotom. Mikrokosmos Band 78, Seite 124 |