Submitted to: Protoplasma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2006
Publication Date: 10/1/2007
Citation: Volk, G.M., Caspersen, A.M. 2007. Plasmolysis and recovery of different cell types in cryoprotected shoot tips of mentha x piperita. Protoplasma 231:215-226. Interpretive Summary: Mint shoot tips can be successfully cryopreserved for long term storage in liquid nitrogen. Water is removed from shoot tips during treatments with concentrated solutions containing dimethyl sulfoxide, ethylene glycol, sucrose, and glycerol. During dehydration, plant cell membranes can separate from cell walls in a process called plasmolysis. We quantified the extent of plasmolysis that occurred during the cryopreservation procedure. The smallest meristem cells plasmolyzed the least during the cryopreservation process, while the larger leaf cells in the shoot tips experienced the most plasmolysis. Shoot tips can survive the cryopreservation process, despite the severe desiccation damage that occurs within the large cells of the shoot tips.
Technical Abstract: Mint shoot tips were cryopreserved using a rapid cooling method with plant vitrification solution 2 (PVS2). PVS2 contains dimethyl sulfoxide, ethylene glycol, sucrose, and glycerol and dehydrates shoot tips to minimize the formation of intracellular ice during cooling to liquid nitrogen temperatures. We fixed and embedded shoot tips after each step of the cryopreservation procedure to quantify the extent of plasmolysis within the meristem, young leaf, older leaf, upper cortex, and lower cortex of shoot tips. The meristem cells were the smallest and least plasmolyzed and the large, older leaf and lower cortical cells were the most plasmolyzed. After culture, meristem cells were still intact up to seven days after warming while the older leaf and lower cortex cells appeared severely damaged by the cryopreservation process.