Effects of storage temperature and pre-treatments on seed germination of Primula mallophylla and P. sertulum (Primulaceae), two narrowly-distributed endemic species from southwest China

Primula mallophylla and P. sertulum are wild ornamental species of south-west China, but the responses of their seeds to storage have not been determined. When seeds were dry-stored for 24 months at room temperature (RT) (ca. 21°C) and at 4°C, germination increased during the first six months, but then decreased over the following 18 months. The decrease in germination was slower for seeds stored at 4°C than for those stored at RT. When seeds of these two species were dry-stored at -20°C for 24 months, germination percentage was significantly higher than that of the control seeds by the sixth month; the high germination percentages persisted at 24 months. In addition, pre-germination treatments (i.e., immersion in 100 µmol L -1 GA 3 for 24 hours, cold stratification for 30 days or both) improved the final germination and reduced mean germination time of P. mallophylla seeds stored for 12 months at RT, but not those of P. sertulum . Taken together, storing seeds at -20°C is feasible and convenient for both primrose species; thus, it is possible to safely store seeds for future research and conservation.