Fixatives are solutions of substances for preserving the morphological features of tissues similar to the alive features. They allow the processing of biological samples through histological techniques, minimizing the degradation of tissue structures. There are many fixative solutions that are chosen regarding the sample and the feature of the tissue to be studied.
The fixative FAA (formaldehyde, alcohol, acetic acid) is commonly used for plant tissues. Although the cytoplasm is not very well-preserved, it is a good fixative to preserve the plant tissue organization.
Recipe
50 ml ethanol
5 ml glacial acetic acid
10 ml of 40 % formaldehyde
35 ml ditilled H2O
Solutions
Formaldehyde: 40 % of formaldehyde in distilled H2O
Notes
The smaller samples, like thin leaves, are fixed for 12 h, whereas larger organs may be fixed for 24h, or longer.
It is convenient to perform the fixation in a vacuum device. In this way, the intra-tissular air bubbles are removed, favoring the diffusion of the fixative. This is general advice for fixation, no matter the tissue.
Products
Ethanol
Formaldehyde
Glacial acetic acid
Distilled H2O
Labware
Test tube
Bottles