Seed dormancy and germination in Oenanthe stolonifera as affected by temperature and gibberellic acid

Our aim was to investigate the dormancy type of water dropwort seeds for developing seed germination methods in the future. The mature fruit is a schizocarp with sponge-like and thickened ribs. However, the seeds were able to absorb moisture normally. In this study, less than 14% of seeds germinated without any pretreatment after 4 weeks at 20, 25, or 25/15 °C (12/12 h). However, there was a further increase in germination percentage after 10 weeks of incubation at 5/5, 15/6, 20/10, and 25/15 °C. The seeds germinated at higher ratios under relatively colder temperature regimes. Embryo growth in the seeds occurred at both warm and cold temperatures. However, water dropwort seeds require a period of cold temperatures for embryo growth to be completed. The germination percentage was significantly higher in GA3-treated seeds, even though the absolute difference was relatively low. In water dropwort, GA can overcome seed dormancy but cold temperature alone for 8–10 weeks may effectively break seed dormancy and increase germination percentage. Based on these results, we propose that most water dropwort seeds showed intermediate complex morphophysiological dormancy and some seeds had morphological dormancy at the time of dispersal. These results provide useful information for seed propagation and a practical production plan for cultivation of water dropwort.