ULTRASTRUCTURAL-STUDY OF THE EFFECT OF FREEZING-THAWING ON THE GAMETOPHYTE OF THE BROWN ALGA UNDARIA-PINNATIFIDA

Attempts have been made to develop cryoconservation procedures that would allow indefinite storage of gametophytes of the food alga Undaria pinnatifida. Through the use of glycerol as a cryoprotectant, small volumes (200-300-mu-l) of gametophyte suspensions can grow after a freezing-thawing cycle, but a high mortality rate was observed when larger volumes were treated. Investigations into the cause of the freezing injury at the cellular level were made, using electron microscopy. The structure of most cells was highly altered, probably due to cytotoxic leakage of vacuolar contents to the cell cytoplasm. The arrangement of thylacoids was considerably modified. Nevertheless, in some cells there was little modification, probably related to the presence of numerous lipid droplets.