Cryopreservation of Marine Unicellular Algae. II. Induction of Freezing Tolerance

Abstract

The induction of freezing tolerance in marine unicellular algae of Chorella, Nannochloris, Phaeodactylum and Platymonas was assayed by measurements of algal viability following storage in liquid N2. Resistance to freezing was induced and developed in cryo-sensitive algae during growth under limiting conditions of low temperature and nutrient deficiency. Algae grown at 4.degree. C for 4 wk developed high resistance to freezing. Deficiency of nutrients such as NO3, PO4 and bicarbonate slowed the rate of growth and increased significantly the ability of the cell to survive freezing in liquid N2. Reduced metabolic growth of active cells apparently causes augmentation or modification of the cell membrane which serves to increase the resistance to freezing injury.