ABSTRACT
In order to maintain the dynamics of any crop species it is essential to have an inflow of genes into breeding populations from other resources. The required pool of genetic variability has been provided in the past by the primitive cultivars and wild relatives of crop plants. Tissue cultures can also be preserved by maintaining them at low temperature. At this temperature, the growth is slowed down, but not completely stopped. Grape plants could be stored for 15 years at 9°C by yearly transfer to fresh medium. Low-pressure storage is practiced for increasing the shelf-life of meat, poultry, fish, vegetables, cut flowers, and potted plants. Although pure water becomes ice at 0°C, cell water needs a much lower temperature because of freezing point depression due to salts and organic molecules present in a cell sap. Evolution of latent heat occurs during cooling of any biological material. This must be taken into consideration; otherwise it can result in considerable damage.
