Cryopreservation of desiccation-tolerant seeds

The cryopreservation of desiccation-tolerant seeds depends on two key steps: specimen dehydration in an environment that ensures the attainment of water contents below the high-moisture freezing limit; and transfer and maintenance at a subzero temperature that may be optimized in relation to the seed-lot moisture content and species. Temperatures about 70 degrees C below the glass transition temperature (Tg-70) or lower are recommended for seed storage. For fully desiccation-tolerant (type I) seeds, cryopreservation success tends to be independent of cooling regime and subzero (degrees C) temperature treatment when the seeds are dry. However, to maximize recovery of partially desiccation-tolerant (type II) seeds there can be a requirement for slow cooling, avoidance of storage at certain subzero temperatures, and controlled imbibition following cryopreservation, particularly for endospermic seeds that are high in lipid.