Abstract:Protected by DMSO, the suspension cell line derived from the protoplast culture of Brassica campestris var. pekinensis can be stored in liquid nitrogen (-196℃) for a long term. The addition of sorbitol and mannose can increase and decrease the protection, respectively. The medium also has an effect on cryopreservation. The relative survival rates of cells are little different in different days of cryopreservation. The highest rate of relative survival of cryopreserved cells reaches 75.4%. When the cryopreserved cells are thawed and resuspended, regrowth immediately occurs after just one day of lag period. Resuspended for six days, the cells increase 300–500%. It is much better for recovery of growth to resuspend in the dark than in the light. Like the non-cryopreserved control, the cryopreserved cells can be normally digested, producing a number of viable protoplasts which can be actively divided and form calli.