Survival of mint shoot tips after exposure to cryoprotectant solution components

Many plant species can be cryopreserved by treating shoot tips with complex cryoprotectant solutions before rapidly cooling them to liquid nitrogen temperatures. Plant vitrification solution 2 (PVS2), a commonly selected cryoprotectant, can be lethal with extended exposure times. To determine potentially toxic combinations, we have exposed mint shoot tips to one-, two-, three-, and four-component solutions of PVS2 chemicals (30% glycerol, 15% ethylene glycol, 15% dimethyl sulfoxide, and 0.4 M sucrose) at 0 and 22 degrees C. Overall, solution exposures at 22 degrees C were more damaging than exposures at 0 degree C. Solutions with glycerol, particularly in combination with ethylene glycol and dimethyl sulfoxide, were also damaging. Cryoprotectant solutions PGluD (10% PEG8000, 10% glucose, and 10% dimethyl sulfoxide) and PVS3 (50% glycerol, 50% sucrose) were less damaging than PVS2 at 22 degrees C. When plant cryoprotectants are characterized on a toxicological and biophysical basis, less damaging cryoprotectant solutions could be developed.