Freeze-Preservation of Porphyra Thalli in Viable State―I.Viability of Porphyra tenera Preserved at Low Temperature after Freezing in the Sea Water and Freezing under Half-Dried Condition

摘要

Some physiological studies on the freezing of algae had been reported. Recently many investigators have made researches on the preservation of micro-organisms for culture collections, and it seems likely that the freezing or freeze-drying is logical technique for maintainning viable cultures of cells, and has been successful in many instances. However, on marine algae, these experiments are rare in the literature. In this study, the author experimented on the freeze-preservation of thalli of Porphyra tenera and observed the viability of freeze-thawed thalli under the microscope. The results are summarized as follows: 1. When the cell of Porphyra thalli was injured by freezing, at first the plastid was scatterd, and then the cell expanded in size, finally shrinking up. 2. The vegetative and rhizoidal cells of thalli showed higher resistivity against freezing than the carposporangial cells. On the other hand, the survivals of neutral spores were more than those of carpospores and free living Chonchocelis-filaments. 3. From the results of freeze-preservation at various temperatures, the percentage of survival cells was higher, in freezing at -20℃ or over, than in deep-freezing at about -75℃. Furthermore, in deep freezing, the number of survival cells were less in rapid cooling than in slow cooling. 4. During freeze-preservation at -18～-20℃, most of cells frozen in the sea water were dead after 30 days storage, whereas many cells frozen under half-dried condition remained fully viable after 4 months. 5. The survivals of thalli frozen in the presence of glycerol did not increase, while glucose protected thalli against injury of freezepreservation.