Cellular Damage to the Callus Cells of Potato Subjected to Freezing

Callus cells of potato (Solanum tuberosum L.) cv. Désirée were exposed to various subzero temperatures and examined for the freezing damage. In the cells subjected to –3 °C, plasma membranes appeared to be intact, while tonoplast seemed to be damaged and organelles to be swollen. After freezing at –6 °C, the damage became severe and plasma membranes were ruptured. After exposure to –10 °C, the damage was so severe that the cell organelles could not be recognised and cytoplasm became fragmented.