Cryopreservation of Bryophytes and Ferns

Although not as widely studied, bryophytes (mosses and liverworts) and ferns1 have requirements for ex situ conservation and germplasm storage similar to those of vascular seed plants. Cryostorage of tissues or spores of endangered nonseed plants can provide a back up to threatened wild populations, while genetically valuable research lines can be maintained in a stable and cost-effective fashion using liquid nitrogen (LN) storage. Spore banks and in vitro collections provide methods for economically maintaining a large number of genotypes of both groups of taxa, and cryostorage can greatly increase the potential longevity and stability of these collections.

Many of the same methods applicable to tissues of seed plants are adaptable for the cryopreservation of tissues of bryophytes and ferns. Nonseed plants, however, have several characteristics that make them particularly good candidates for cryopreservation and which provide more flexibility in approaches than with seed plants. First, both bryophytes and ferns have pronounced gametophyte and sporophyte stages. In the case of ferns, this provides two very different tissues that can be adaptable to cryopreservation: pieces of gametophytes and shoot tips of sporophytes. Second, in both ferns and bryophytes, the gametophyte stages are highly regenerative and can reproduce vegetatively from fragments. Finally, some bryophytes and ferns have vegetative tissues that are naturally desiccation tolerant. This adaptation can be useful in providing tissues that can more easily survive the reduction in water that is needed in many cryopreservation protocols. In addition, spores of both bryophytes and ferns can be used for cryostorage. This chapter will provide a brief review of the various types of tissues that can be used for cryopreservation of bryophytes and ferns and the different methods that were used to successfully recover living tissues after exposure to low temperatures.