FREEZE-PRESERVATION OF BUDS FROM SCOTS PINE TREES

A procedure has been developed for freeze-preservation of buds of the Scots pine (Pinus sylvestris L.). Instead of liquid nitrogen, cold storage in -80-degrees-C was used. The partly dormant material used in the experiments was obtained directly from a natural stand in Northern Finland and no prefreezing or cryoprotectants for preconditioning were used. Cooling velocity was 1-degrees-C/min up to a terminal freezing temperature of -39-degrees-C, after which the buds were immersed in liquid nitrogen at -196-degrees-C for 10 minutes. The material was then transferred to a deepfreezer at -80-degrees-C and stored up to 6 months. After rapid thawing, the buds were sterilized and their viability was tested by FDA staining and by culturing meristems on 1/2 MS medium for at least two weeks. All the freezing experiments were performed during March and April. The best survival of buds (90-100%) was achieved at the beginning of April, after which a pronounced decline in survival occurred obviously due to a rise in the water content of the buds.