Nondeep complex morphophysiological dormancy in seeds of Osmorhiza claytonii (Apiaceae)

Under natural conditions, embryo growth begins in late September and early October and continues until mid- to late February, with the peak in Ocrober and November. Most seeds germinate between mid-Frebruary and late March. Embryos did not grow in seeds incubated for 24 wk at 30/15 (warm stratification) or 5°C (cold stratification). However, in seeds given 12 wk at 30/15 and then 12 wk at 5°C, embryo length increased 1246% while seeds were at 5°C. Zero to seven days of warm followed by 24 wk of cold stratification resulted in 2-27% germination of fresh seeds, whereas 2-12 wk of warm followed by 24 wk of cold stratification in 80-98% germination. Warm plus cold stratification was required for embryo growth and germination of seeds that remained undispersed for a year in the field. GA, was partially effective in substituting for warm stratification. -from Authors