Breaking of Two Types of Dormancy in Seeds of Polygonatum odoratum Used as Vegetables

Abstract

When freshly mature seeds of Polygonatum odoratum Druce var. pluriflorum Ohwi were planted in October and grown outdoors, no radicle emerged until the next summer and no green shoot emerged until the second spring. Radicle emergence (germination) was induced by cold stratification, so that radicle dormancy was completely terminated by stratification at 5°C for 60 days. Radicle dormancy of nonchilled seeds was partially broken by treatment with 5 mM ethephon. The optimum temperature range for germination after the termination of radicle dormancy was 17 to 25°C. The cold stratification of seeds, removed from fruits, improved germination than a similar treatment on intact fruits. Air-drying seeds for about a week before cold stratification had little effect on their germination. Seeds kept moist at 21°C after the termination of radicle dormancy almost stopped growing after 90 days of incubation because the epicotyl became dormant (epicotyl dormancy). Hence, no green shoot emerged aboveground unless the seedlings were chilled again to terminate epicotyl dormancy. Therefore, the type of dormancy in P. odoratum seeds resembles double dormancy described by Barton and Schroeder (1942). The optimum temperature range for shoot emergence after the termination of epicotyl dormancy was 17 to 29°C. Warm stratification after cold stratification and exposure to a second chilling greatly affected the time shoots emerged. Higher percentages of early and total shoot emergence were obtained when seedlings were kept either at 21°C for 120 days after the termination of radicle dormancy and then chilled at 5°C for 90 days to terminate epicotyl dormancy or kept at 21°C for 90 days and then chilled at 5°C for 120 days.