Seed Dormancy in the Prairie Forb Echinacea angustifolia Var. Angustifolia (Asteraceae): Afterripening Pattern During Cold Stratification

Abstract

Cold stratification was required to break dormancy in seeds of Echinacea angustifolia var. angustifolia, a widely distributed taxon of prairies and barrens in the midcontinental United States. The temperature requirements for germination of E. angustifolia seeds coming out of dormancy differ from those reported for 15 other species of Asteraceae, which first began to germinate at high (30/15, 35/20) or at medium (20/10 C) temperatures. As seeds of E. angustifolia began to afterripen, they germinated over a range of thermoperiods including 15/6, 20/10, 25/15, and 30/15 C. After 8 wk of stratification, seeds germinated to 63%-91% at 15/6, 20/10, and 25/15 C. Thus, even when seeds are not fully afterripened, they can germinate to high percentages at low spring temperatures, whereas those of other spring-germinating composites must be nondormant to germinate well at low temperatures.