抄録
In order to obtain fundamental data for use in establishing an effective cryopreservation method, seasonal changes in resistance to freezing and survivability of cryopreserved pear leaf bud apices were examined. The survival rate of cryopreserved apices, excised, treated with cryoprotectants ( 8 % v/v DMSO and 3 % sucrose), cooled from 0℃ to-40℃ at a rate of 0.5℃/min, immersed in LN_2, thawed in warm water (38℃) and cultured, was high for apices treated in winter and low for spring. It decreased from March to April and increased from October to December. Seasonal changes of survivability by cryopreservation paralleled those of freezing resistance. A varietal difference in the level of resistance to freezing was found amoug apices collected in winter. The survivability by cryopreservation of apices excised from twigs, col-lected in winter and stored for 1-7 months at 0℃, was maintained at a high level. The fact that the rate of rosette-forming apices was relatively low in each material, suggested that dome tissue might be damaged by freezing.
