SOFTENING OF PLANT SPECIMENS (EQUISETACEAE) TO IMPROVE THE PREPARATION OF PARAFFIN SECTIONS

A method is presented for softening the hard tissues of stem and strob ile of Equisetum giganteum allowing the preparation of representative histological slides suitable for teaching and research. Segments of ae rial portions of the Equisetum giganteum shoot system were fixed with formaldelhyde:ethanol:acetic;acid (5:10:5) for 24 hr at room temperatu re, washed in distilled water and immersed in a mixture of 5% hydroflu oric acid and 0.5% sulfuric acid for: 1 hr at room temperature, Hydrof luoric acid has a higher affinity for silica components, and the sulfu ric acid acts as a catalyst favoring the separation of calcium silcate s. This simple, inexpensive-and rapid method allows paraffin sections to be prepared while preserving the topographic microanatomy by decrea sing technical artifacts produced by conventional softeners, and prese rving PAS-positive polysaccharides.