Post-dispersal embryo development, germination phenology, and seed dormancy in Cardiocrinum cordatum var. glehnii (Liliaceae s. str.), a perennial herb of the broadleaved deciduous forest in Japan

In an investigation of seed germination in Cardiocrinum cordatum var. glehnii, embryos in fresh seeds in October were underdeveloped and did not grow until September of the following year. Then, they grew rapidly and had fully elongated by early November. In the second spring after dispersal, radicles emerged under snow in late March and after snowmelt in April. Cotyledons emerged soon after radicles. In several laboratory experiments, embryos grew at 15°/5°C (light 12 h/ dark 12 h) following 25°/15°C. Radicles emerged from seeds with fully elongated embryos at 5°-15°C after cold stratification at 0°-5°C. Cotyledons emerged in 2 wk from seeds with a radicle at 15°/5°C to 30°/20°C. Although seeds require c. 18-19 mo after dispersal to germinate in nature, under controlled conditions, they required only 9 mo with a sequence of 25°/15°C → 15°/5°C → 0°-5°C → 15°/5°C. This is practical knowledge for propagation of plants from seeds. GA₃ treatment partially substituted for the high temperature requirement. Based on dormancy-breaking requirements, the seeds have deep simple morphophysiological dormancy (MPD). A literature review of seed dormancy in taxa of Liliaceae s. str. showed that phylogenetic position in this case is not a good predictor of level of MPD.