**6. Conclusions**

While numerous studies have demonstrated that proline can be used to improve the survival of plant cells and organs following cryopreservation, there is little definitive evidence as to the mode of action of proline. More research is required to determine how proline protects plant cells at the cellular level and to determine how other treatments that confer cryotolerance, such as ABA pretreatments interact with proline metabolism and could hence improve the cryotolerance of plant cells. However, despite our lack of knowledge with respect to the mode of action of proline, this amino acid continues to be of great value as a cryoprotectant that can be used with a wide range of cell types from many different organisms.
