With regard to the production of specific compounds, however, cell cultures often show a remarkable instability. The cryopreservation of plant cells is still a routine laboratory method but it is necessary to optimize the individual steps of the cryopreservation procedure. Butenko et al. (1984) who cryopreserved ginseng cells for the first time, used a pretreatment which combines low temperatures (+4° C) with a high sucrose concentration (20 per cent). The use of sucrose as a preculture additive and a cryoprotectant seems to be advantageous as it is not toxic for the cells even at very high concentration.
Seitz and Reinhard (1987) developed a cryopreservation procedure for P. ginseng cell cultures which makes long term storage of selected strains possible. Sorbitol was used as a short term preculture additive with or without supplementary DMSO as a cryoprotectant. Cell strains of similar appearance but different ginsenoside productivity do not differ in their response to the cryopreservation method used.
Yoshimatsu et al. (1996) successfully cryopreserved ginseng hairy root segments obtained by infecting petiole segments with A. rhizogenes. For cryopreservation, a vitrification method was applied. The hairy roots regenerated from cryopreserved root tips grew well and showed the same ginsenoside productivity and patterns as control hairy roots cultured continuously at 25° C. Moreover, the PCR analysis proved the presence of T-DNAs in the regenerated hairy roots.
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