Germination Ecophysiology of an Eastern Deciduous Forest Herb Stylophorum diphyllum

Abstract

Stylophorum diphyllum (Michx.) Nutt. is an herbaceous polycarpic perennial that grows in mesic deciduous forest from western Pennsylvania and southern Ontario to Wisconsin S to southwestern Virginia, northern Alabama, northern Arkansas and Missouri. Seeds are dormant at dispersal in late May and early June. Dormancy is due to a rudimentary (i.e., underdeveloped) embryo which requires incubation at low moist temperatures (stratification) for growth. In the habitat, embryo elongation occurs during the cold season and seeds germinate in early spring. A warm pretreatment is not required for subsequent embryo growth and germination. Embryos in freshly matured seeds averaged 0.41 mm long but after 10 weeks of chilling at 5 C they averaged 1.41 mm. Germination of seeds incubated continuously at 5 C began after 11 weeks and after 19 weeks 80 %O had germinated. Seeds stratified for 6 weeks and then transferred to (12/12 hr) daily thermoperiods of 15/6 and 20/10 C germinated to 75 and 65 %O, respectively, whereas 12 weeks of stratification were required before a comparable percentage of seeds would germinate at 25/15 C. Seeds of S. diphyllum fit Nikolaeva's definition of morphophysiological complex dormancy.