Preparing Fixative

We utilize a common fixative referred to as FAA to preserve our tissue samples.  FAA is a solution of Formalin/Glacial Acetic Acid/Ethanol/DI water in the following percentages:  10% Formalin / 5% Glacial Acetic Acid / 50% ethanol (use 95% EtOH) / 35% DI water.  This fixative, along with others, are described by Ruzin (1999), but the amount of ethanol can be adjusted for your needs.  For example, if the proportion of ethanol is too high for your tissue it can cause dehydrate and result in tissue shrinkage, altering the dimensions of some tissues (like the mesophyll layer in leaves).

Once the fixative solution has been prepared, we place a small amount of the solution in small plastic containers (keep in mind we are usually studying small-leaved plant species) and then put the tissue in the solution.  In order to ensure the fixative has completely infiltrated the tissue we place the sample/solution in a bell jar and evacuate the chamber until the liquid begins to boil.  At this point we release the vacuum, and the repeat this cycle several times.  After a few cycles we put the bell jar under vacuum until the liquid boils and then seal the jar so that it remains under vacuum for 24 hours.

Citation:

Ruzin. 1999. Plant Microtechnique and Microscopy. Oxford University Press. New York.  322 pp.