Tissue Cryopreservation in Plants: What it Means for Today's Agriculture, the Potential, and the Challenges

Cryopreservation is a process by which cells, tissues, or any other material sensitive to time or chemical reactivity can be preserved using a cooling process to sub-zero temperatures. If the temperature is low enough, it is able to stop any enzymatic or chemical activity which may cause damage to the material. This method is mostly popularized by the media portrayal of scientists attempting to preserve humans through freezing and reanimating at a future time. It is also being looked into as a method for nonseed plant conservation. Cryopreservation methods are currently seeking a way to reach low temperatures without causing additional damage by the formation of ice during freezing. Traditionally, cryoprotectants (a class of molecules) have been used to coat the material to be frozen in order to prevent freezing damage. It should be noted though, that Cryopreservation alters/compromises the structure and function of cells as a general rule, unless it is proven otherwise for a specific population.

In a study conducted by Valerie C. Pense (2014), the benefits, implications, and challenges posed by  Cryopreservation of nonseed plant tissues were looked at. Cyropreservation of nonseed plant tissues can be used as a way to save the genetic material of the plant  when seeds and spores cannot be altered to fit traditional preservation methods in order to keep genetic diversity. Shoot tips (where the flowers or leaves emerge from at the tip of the stem), somatic embryos, and gametophytes can be used as separate materials for which a new plant grows, and therefore can be stored long term in liquid nitrogen. Tissue cryopreservation is especially important when dealing with species that have unbankable seeds or produce little to none, known as "exceptional species."



 Methods of collecting tissues and establishing cultures in artificial environments outside of the organism can be applied as a source of tissue cryopreservation. The applicability of using heat fusion to change the tissue into a glassy substance or using dehydration cryoprocedures has been shown for a wide range of species and types of tissues, and the natural adaptations of the species influence the cyropreservation method chosen and what tweaks must be made to them. When assisting in and growing these tissues in prepared nutrient mediums they are normally bred with clones or cells with similar genetic material, but preserving tissues from multiple genotypes can provide genetic diversity to a cryopreserved collection. This will allow collections to serve the ultimate purpose of providing materials for restoration if wild populations are lost or severely threatened.

Even with the great potential that these methods have to improve plant conservation efforts and secure species diversity for the future regardless of how we humans move forward in regards to the environment, there are also both scientific and practical challenges to their application. These must be assesed when looking at the appilicability of these methods. Where in vitro methods are well established for multiplying species and conserving their DNA, cryopreservation methods are still really based on experiments and observations regarding their application to new species. This can be quite the challenge for conservation, which deals with rare and often unstudied species, that may have unusual natural adaptations. Also, due to the labor involved, tissue cryopreservation is more expensive than traditional methods. This can limit already traditionally underfunded work with endangered plants. Scientists do hope that with collaborative efforts though, we can help meet these challenges. The potential for cyropreservation to allow for new species of plants to be used as food and to make sure that the diversity of flora is not destroyed through modern agriculture is HUGE. The hope is that with studies like the one linked above, we can better connect cyropreservation techniques with endangered plant species in order to help conserve them and have more time to figure out their specific contributions and benefits to the environment and human civilization, as well as keep them around as long as possible. 

Links: 
http://www.jstor.org/stable/10.1086/673301