Cryopreservation of Shoot-Tips and Meristems

The ability to regenerate whole plants from cryopreserved, meristematic shoot tissues provides a useful method for conserving plant genetic resources. This technique is especially important for vegetatively propagated species, or, for plants that produce recalcitrant seeds. Within this chapter, methodology is presented for those vegetative, meristematic tissues (apical and axillary shoot-tips, nodes, and buds) that have the potential to develop new shoots and regenerate whole plants after cryogenic storage. The term “shoot meristem” is frequently used erroneously in the context of cryopreservation. The shoot meristem is anatomically defined as a structure that contains the apical dome, and the youngest, unexpanded leaf primordia directly associated with the dome meristem. In practice, it is the larger shoot-tip used in “meristem cryopreservation.” This structure comprises the meristem apex, subjacent tissue, and several larger, and often expanded, leaf primordia. Shoot-tip size and origin (e.g., apical or axillary) are critical factors in influencing the ability of tissues to survive cryopreservation. It is also possible to freeze nodal stem cuttings containing an axillary meristem and the dormant, and/or cold hardened buds of woody perennial species.