IN VITRO PRESERVATION AT LOW TEMPERATURE OF ROSE PLANTLETS USABLE FOR DIRECT ACCLIMATIZATION
The best preservation was obtained under low light intensity (2–3 Wm-2, 8h.) in comparison with darkness. For short storage period (below 6 months), lowering the temperature from 4°C to 2°C was detrimental unless sucrose concentration was enhanced to 45 gl-1 in the standard medium. Increasing sucrose concentration was particularly useful for preservation and acclimatization when shoots were stored 6 days after subculture (R6) on rooting medium, or when low temperature was applied immediately after subculturing (R0) for the 2 month storage only. It was possible to preserve plantlets of the two varieties during 6 months, according to the stage of storage (R0 or R6), stimulation of root growth (8 days) was needed before acclimatization. In the greenhouse, plant growth was at least similar to the control.