Submitted to: CryoLetters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2000
Publication Date: N/A
Interpretive Summary: Wild currant shoot tips were analyzed for water content during a liquid nitrogen (freezing) process. Shoot tips enclosed in tiny beads were quickly cooled in liquid nitrogen (-320oF) and all cellular water turned to a glass. However on rewarming the glass destabilized and formed ice crystals. When the shoot tips or the alginate beads were cooled and rewarmed separately this ice crystal formation did not occur. The posibility exists that temperature and moisture differences occur within the shoot tip/alginate bead complex resulting in the ice formation when they are rewarmed. The study showed that either cold acclimation or pregrowth of shoots on a high sugar medium will prepare the shoot tips for freezing in liquid nitrogen.
Technical Abstract: DSC analysis was performed at three points in the cryopreservation process on encapsulated-dehydrated meristems of Ribes ciliatum. Meristems were excised from shoots pre-treated with either sucrose or glucose, encapsulated in alginate beads, dehydrated in sucrose solutions, air dried, and plunged in liquid nitrogen. Thermal analysis revealed glass transitions during cooling of air-desiccated meristems; however, on rewarming a small endothermic event was detected suggesting glass destabilization can occur. Interestingly, this did not occur in alginate beads or meristems when these components were cooled and rewarmed separately. The possibility exists that thermal and moisture gradients may arise within the alginate bead/tissue complex and we propose that the heterogeneous composition of the meristems and the surrounding alginate may promote ice nucleation on rewarming.