Cryopreservation of plant cell cultures1.

The main topics of this brief overview of the cryopreservation of plant cell cultures are (a) the principles behind Cryopreservation procedures as a basis from which the appropriate method for various different cultures can be developed, and (b) the question of how far the characteristics of cell strains are preserved during the freeze-thaw cycle. Of all the species successfully cryopreserved to date, only seven have been investigated with regard to their biochemical capacities. In all these cases the cultures have been shown to retain their growth patterns and biochemical traits. Furthermore, results are available which indicate that this is also valid for long-term storage. Some details are presented on the accumulation of natural products and the biotransformation of cardenolides in frozen-thawed cell cultures. On the other hand, before it is possible to recommend universally applicable cryopreservation protocols, we must better understand the cellular events which determine the freeze-tolerance of plant cell cultures.