Seed germinability in the endangered Pulsatilla cernua (Ranunculaceae) following cold storage for up to 31 years

Abstract Pulsatilla cernua is an endangered species in Japan and its seeds are often stored for long periods. However, the shelf life of these seeds is unclear. We conducted germination tests using P. cernua seeds that had been stored in a refrigerator at approximately 6°C for up to 31 years. Germination tests were conducted at 25°C under dark conditions. We assessed seed weight, number of germinated seeds, seedling development, and time to germination over a 30‐day period for each collection year. The highest germination rate was from seeds collected in the current year (2019; 82.7%). Germination rates remained high in seeds that had been stored for up to 7 years (>46%). However, there was a marked decline in germinability after the eighth year of storage and germination was not observed in seeds that had been stored for longer than 15 years. Approximately 20% of current‐year seeds and seeds that had been stored for up to 6 years developed into seedlings, but no seedlings developed from seeds that had been stored for 7 years or longer. The germination rate and the time to germination decreased and increased, respectively, with storage time. These results show that the shelf life of P. cernua seeds in cold storage at 6°C is approximately 6 years. To facilitate the ex situ conservation of this species, the germinability of stored seeds at lower temperatures and under other germination test conditions should be explored in future studies.