**1. Introduction**

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and fatty acid composition in banana meristems caused by sucrose-induced acclimation and its effects on cryopreservation. *Physiologia Plantarum* 128:pp. 80-94.

> The plant genetic resources is preserved by pollen, seed, branch, bulb, or tissue culture at the gene bank. Since these need to be updated periodically (several months ~ several years), I point out the problems involving the great labor and space spent for the maintenance of plant genetic resources.

> Cryopreservation is a storage method of plant genetic resources at ultra-low temperature, for example, that of liquid nitrogen (LN; -196 oC). It is a preservation method that enables plant genetic resources to be conserved safely, and cost-effectively.

> For successful cryopreservation, it is essential to avoid intracellular freezing and induce the vitrification state of plant cells during cooling in LN. In addition, the cryopreservation method should be a simple protocol for everyone to use easily. Since the 1970's, cryopreservation techniques have been researched using different plant organs, tissues and cells. As a result, different cryopreservation procedures have been developed (for example, slow-prefreezing method, vitrification method, dehydration method). With the development of these cryopreservation methods, tissues of tropical plants, which have been conventionally thought to be not cryopreserved, also were successfully preserved in LN (Bajaj, 1995; Towill & Bajaj, 2002). In this Chapter, I describe different types of cryopreservation methods.

> In addition, I often ask my colleagues why cryopreservation of plant tissue did not succeed irrespective of the method. As the cause, it is possible that there is a problem in the character of plant species (stress resistance and polyphenol production), or the ways used in the cryopreservation technique. Then, I also would like to present some knowledge about some improvements for making cryopreservation of plant genetic resources more successful in this chapter.
