Breaking of Two Types of Dormancy in Seeds of Edible Polygonatum macranthum

Abstract

When freshly harvested mature seeds of Polygonatum macranthum Koidz. were planted in October and grown outdoors, no radicle emerged until the following summer and no shoot emerged until the second spring. Radicle emergence was induced by chilling moist seeds at 17°C or below ; radicle dormancy was completely terminated by stratification at 5°C for 60 dyas. The optimum temperature range for germination after the termination of radicle dormancy was about 21°C. The cold stratification of excised seeds improved germination over a similar treatment on intact fruits. Air-drying seeds for about 3 days before cold stratification delayed germination. Seeds, kept moist at 21°C after the termination of radicle dormancy, almost stopped growing after 60 dyas of incubation because the epicotyl became dormant. In this case, no shoot emerged unless the seedlings were chilled again to terminate epicotyl dormancy. Therefore, the type of dormancy in P. macranthum seeds resembles the one in P. odoratum (Takagi, 2001). The optimum temperature range for shoot emergence after the termination of epicotyl dormancy was 25 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 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.