Breaking deep epicotyl physiological dormancy in Chionanthus retusus (Oleaceae) seeds

Abstract

Given that the cause and the method of dormancy release in Chionanthus retusus seeds are unclear, in this study, C. retusus seeds with a hard endocarp (seed dispersal unit) were used for endocarp permeability determination, germination test after endocarp removal and isolated embryo culture to detect the cause of radicle dormancy. Endosperm removal, cold moist stratification, warm moist stratification and GA3 treatment of rooted seeds were used to detect the cause of epicotyl dormancy. The results indicated that C. retusus seeds have non-deep physiological dormancy and deep epicotyl physiological dormancy, the release of which was closely related to the length of the emerged radicle. Rooted seeds with a radicle length < 3 cm could not be effectively released from epicotyl physiological dormancy by endosperm removal, GA3 soaking or cold/warm stratification treatments, whereas those > 3 cm could be significantly promoted for release from epicotyl physiological dormancy by endosperm removal and cold moist stratification treatments. The highest shoot emergence rate of rooted seeds (radicle length > 3 cm) was achieved after 120 days of cold moisture stratification treatment. These results could improve our understanding of seed dormancy and promote the conservation and use of C. retusus.