Germination phenoology and mechanism of seed dormancy on northern landscaping plants that need two years from seed dispersal to germination

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In northern part of Japan, there are several aesthetic native plant species and some of them have the seeds which need two winters from seed dispersal to cotyledon emergence. The goal of the study was to reveal the germination ecophysiology and seed dormancy mechanism of such seeds.Seeds of Cardiocrinum cordatum var. glehnii have underdeveloped embryo when seeds are dispersed. It took 18 mo from seeds dispersal to radicle emergence and 19 mo for cotyledon emergence in nature and they have deep simple morphophysiological dormancy. However, temperature sequence 25/15℃ (60d)→15/5℃ (30d) →0℃ (120d) →15/5℃ using incubator shortened the period from sowing seeds to radide emergence to 7 or 8 mo. Seeds collected in autumn, stored at 5℃, and sown by June in the following year germinated more than 88% in the next spring. On the other hand, seeds sown in August in the following year or later germinated to low percentages in the next spring. Seeds of C. cordatum var. glehnii need temperature sequence high-moderate-low-moderate for embryo growth and germination, however, seeds sown in August or later were not exposed to enough period of high temperature and then only a part of them germinated. These results are the first report on seed dormancy of genus Cardiocrinum in the world and contribute to the field of seed ecophysiology; further they are valuable information for the artificial propagation.Seeds of Trillium camtschatcense also have small and underdeveloped embryo. Embryos in the seeds dispersed in late July grew during the next summer and radicles emerged soon after the embryo growth. Cotyledon emerged in the spring after winters. temperature treatments were applied to the seeds to determine the temperature requirement for germination. However, we still did not find the effective temperature treatment.