619 PB 325 Respiration as an indicator of health in excised, dormant vegetative apple buds subjected to cryopreservation treatments
cryopreservation of dormant, vegetative apple buds at the National Seed Storage Laboratory is used to maintain a base collection for germplasm held in the National Clonal Germplasm Repository for apple and grape, Geneva, NY, and is performed by a method previously reported1. Growth of buds after grafting is now used to test for survival after exposure to and storage at very low temperatures (ca.-160°C). We are interested in determining if measures of respiration can be used to assess 1. the status of buds and bark used for preservation, 2. survival after different treatments related to cryopreservation, and 3. the extent of sublethal injury after treatments. A Licor 6252 CO2 analyzer was used to measure respiration. Reproducible measurements of respiration required at least 2-3 buds. Buds from winter harvested twigs (ca 45-48% moisture content) that were briefly warmed to room temperature respired at a rate of 34 umoles CO2 g-1 (dw) hr-1. Survival of buds is enhanced if twigs are dried prior to cooling. We found such treatments reduced respiration over non-dried controls. Respiration increased as the bud was rehydrated. Buds from dried twigs slowly cooled to low temperatures had levels of respiration after warming and rehydrating similar to undried, unfrozen controls. Buds from undried twigs directly placed at -196°C and warmed gave little CO2 production.