Cryopreservation is the storage of living material in liquid nitrogen at around -196° C. At such low temperatures, all metabolic activity stops. This greatly increases the amount of time seeds can be held in storage before viability substantially decreases and a new collection must be made.
Cryopreservation may be utilised to store orthodox seed collections to extend the period of seed viability in storage. It is often used for intermediate and recalcitrant species that cannot tolerate cold (-20o
C) storage, or desiccation, although in this case a lot of perfecting needs to occur to ensure successful preparation, storage and recovery.
Cryopreservation has been successfully applied to several rainforest species, however this often requires the dissection of seeds so that just the embryo remains. By dissecting the seeds the material to be stored is smaller which means it freezes a lot faster as well as the added advantage of taking up less space is the storage tank. Upon removal, the embryos need to be carefully grown on using tissue culture
techniques to provide a better opportunity for survival. More information on cryopreservation can be found here