FREEZING TOLERANCE OF BULB SCALES OF LILY CULTIVARS - EFFECTS OF FREEZING AND STORAGE DURATION AND PARTIAL DEHYDRATION

Effects of freezing duration, previous storage duration of bulbs at -2 degrees C, and partial dehydration of scales on freezing tolerance of lily (Lilium hybrids) scales were studied for a series of cultivars. Freezing tolerance of scales was estimated by measuring ion leakage an d recording seals bulblet regeneration. Both methods gave similar resu lts. Freezing tolerance decreased with freezing duration. A longer pre vious storage duration of the bulbs at -2 degrees C tended to reduce f reezing tolerance of the scales. Dehydration of the scales to 10-20% l oss of water content significantly increased freezing tolerance. Furth er dehydration to 30-40% loss of water content did not further increas e freezing tolerance. Nucleation temperatures, temperatures during cry stallisation and melting temperatures of the scales were recorded for the cultivar <<Enchantment>>. Nucleation occurred at higher temperatur es after a longer previous storage duration of bulbs, indicating a red uced capacity to remain supercooled. The increased freezing tolerance of dehydrated lily scales could partly be explained by a decreased mel ting temperature of the scales. We conclude long term storage of lily bulbs at -2 degrees C to be safer after partial dehydration to 10-20% loss of the original water content.