Freeze-Drying of Plant Tissues

Abstract

FREEZE-DRYING has proved a valuable technique in cytological investigations of animal cells and tissues, but it has not met with the same success when applied to plants¹. Frozen-dried animal tissues are usually embedded in de-gassed paraffin wax which is later removed from the sections with xylol. Unfortunately, infiltration of frozen-dried plant tissue with molten paraffin or ester wax has proved extremely difficult, if not impossible. Previous failures may have been due to the large vacuoles and intercellular spaces which make plant cells particularly liable to damage during infiltration. These capillary spaces fill with air when frozen-dried tissues are brought from the vacuum chamber into the atmosphere and, even when subsequent infiltration is done in vacuo, the trapped air probably prevents complete impregnation. Another likely cause of damage is the removal of lipoidal substances from the membranes in plant protoplasm by molten paraffin wax and fat solvents.