Cryopreservation of Medicinal Plant Seeds: Strategies for Genetic Diversity Conservation and Sustainability

The depletion of medicinal plant resources leads to the irreversible loss of their genetic diversity. The preservation of medicinal plant germplasm using cryobanks is crucial for maintaining the sustainability of these resources. This study examined the efficacy of cryopreservation on 164 medicinal plant seeds, identified general principles for preserving medicinal plant seeds at ultra-low temperatures, and established a cryobank for dry-sensitive medicinal plant seeds. Over 90% of orthodox seeds were unaffected by freezing, with optimal conditions being a 5-10% moisture content and direct freezing. Intermediate seeds were best frozen with a 7-15% moisture content, and those with a lower initial moisture content were best suited to direct freezing. While recalcitrant seeds' freezing was most influenced by moisture content, there was no specific range. Direct freezing is appropriate for recalcitrant seeds possessing a hard seed coat and a firm seed kernel, whereas seeds with a brittle or soft seed coat are better suited for vitrification or stepwise freezing methods. There was no significant correlation between alterations in physiological and biochemical indicators and microscopic structures of seeds before and following liquid nitrogen freezing, as well as their storage characteristics. The findings of this research offer evidence in favor of the extended conservation of plant seeds and the extensive utilization of ultra-low temperature technology and provides an example of protecting the genetic diversity of plant resources.