Cryopreservation is the ultra-low temperature storage applied for plant conservation by the Botanic Gardens and Parks Authority.
The following article is reproduced with permission by Anja Kaczmarczyk from the bi-monthly 'Breakthrough' Science Newsletter which is coordinated by the Kings Park Science team.
Fig. 1. Cryostorage at Kings Park and Botanic Garden.
What is cryopreservation?
Cryopreservation means the storage of biological material at ultra-low temperature in or above liquid nitrogen at temperatures of -130°C (vapour phase) down to -196°C in the liquid phase. The material has to be stored in such a way that it is still viable upon rewarming to ambient temperatures (Fig. 1).
Why do we store plant tissue at those cold temperatures?
Cryopreservation is applied for long-term conservation of plants, where seeds are not available, not storable (desiccation sensitive) or where specific genetic characteristics need to be conserved as in the case of heterozygous plants of specific plant varieties.
Fig. 2. Lomandra sonderi tissue culture plants.
Storage at ultra-low temperatures has the advantage of being cheaper and less labour intensive compared with maintaining plants in tissue culture or in the field/greenhouse.
Once the plant tissue is successfully stored (intracellular water has to turn into a glassy state and ice formation has to be avoided), only refilling of liquid nitrogen is needed and otherwise samples can be preserved for theoretically indefinite periods as they will not change over time.
Current research project
Fig. 3. Lomandra sonderi shoot tips regrowing after storage in liquid nitrogen.Kings Park's research in this area is part of an ARC-Linkage project focusing on the development of cryopreservation protocols for plant species important in post mining restoration. This research project was started at Curtin University and Kings Park and Botanic Garden in 2009.
Plant species for which cryopreservation protocols are currently developed are Loxocarya cinerea (Restionaceae), Lomandra sonderi (Asparagaceae) and Lepidosperma squamatum (Cyperaceae), all native and endemic to southwest Western Australia. In Lomandra sonderi a successful protocol has been developed (Fig. 2, 3), where shoot tips are used as explants and a droplet vitrification method (Fig. 4).
Next to the development and optimization of the cryopreservation protocols we are also determining the composition of the membranes as they are the primary site of cryo-injury. The membrane composition data are given to another research group at Curtin University to establish molecular membrane models. Those models can help us to understand the function of membranes and can provide us information on their interaction with commonly used cryoprotectants.
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| Fig. 4. Foils holding shoot tips in droplets of cryoprotectant ready for storage in liquid nitrogen (a), two foils are transferred into each cryovial (b), which are stored in a big dewar for the long-term (c). | ||
With these results, we might be able to better understand, why one plant species is easier to cryopreserve than another, and ultimately improve the conservation of Western Australian biodiversity.
Further information
Please contact Anja Kaczmarczyk for further information or enquiries about cryopreservation used by the Botanic Gardens and Parks Authority.