Abstract
Shoot apices aseptically isolated from dormant buds of a Japanese pear (Pyrus serotina REHD. var. culta) were frozen at the temperature of liquid nitrogen. In dormant pear shoot apices, it was not necessary to use a cryoprotectant to maintain their viability during the exposure to liquid nitrogen and about 80% of the shoot apices survived the immersion in liquid nitrogen following prefreezing below -40°C, regardless of the rewarming procedure applied. Shoot apices treated with 10% dimethyl sulfoxide (DMSO) solution were prefrozen at -40°C and then immersed in liquid nitrogen for a period of 40 days. When rewarmed rapidly in water at 38°C, they appeared to be alive.
