Viability and Spore-liberation of Conchocelis-phase, Porphyra tenera, Freeze-preserved in Sea Water

摘要

There are distinct differences between thallus- and Conchocelisphases of Porphyra tenera KJELLMAN in general ecological aspects, especially in degree of drying injury. Though the thallus-phase of this alga shows high frost-resistance, it may be considered that the Conchocelis-phase is affected unfavorably by freezing and freeze-preservation. The present report deals with the frost-resistance of Conchocelis of Porphyra tenera, using the free- and shell-living materials. The liberation of conchospores from the shell-living Conchocelis freezepreserved at low temperatures was also observed. The results obtained are summarized as follos: When the Conchocelis-filaments were frozen and freeze-preserved in sea water, they showed lower frost-resistance than the leafy thalli. In the freezing of free- and shell-living Conchocelis-filaments, the former showed higher survival-rates of branches and conchosporangial cells. On the other hand, conchosporangial cells showed higher resistivity than cells of branches against freezing injury. Of those conchosporangial cells, mature divided sporangia survived well after freeze preservation at -20℃, and could tolerate without remarkable damage at least for 1 month. In the freezing at various cooling rates, ranging from 0.05℃/min to 40℃/min, the survival of Conchocelis-cells was less in rapid cooling than in slow cooling. The survival of Conchocelis-cells frozen at various low tempera-tures decreased according as temperature lowered. Furthermore, the survived cells of long preserved Conchocelis gradually decreased in number during freeze-preservation. Some shell-living Conchocelis, freeze-preserved for 1 month at -20℃ and then thawed, liberated numerous conchospores for the following several days.