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�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 (�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 slowcooling, avoidance of storage at certain subzero temperatures, and controlled imbibition following cryopreservation, particularly for endospermic seeds that are high in lipid.
