Methods of breaking seed dormancy in the endangered species Iliamna corei (Sherff) Sherff (Malvaceae), with special attention to heating

Iliamna corei (Sherff) Sherff, an herbaceous perennial plant listed by the U.S. Fish and Wildlife Service as endangered, is known only from a single site, on Peters Mountain in Giles County, Virginia. Seed dormancy in this species is due to a water-impermeable seed coat. Dormancy was broken in a high percentage of seeds by mechanical scarification, dipping in boiling water, dry-heating, and soaking in concentrated sulfuric acid. However, soaking in absolute ethanol, shifting from low to high temperature regimes, or alternate freezing and thawing did not break seed dormancy. Fire was effective in breaking dormancy of seeds on the soil surface, but not in those covered with 3 cm of soil. Seeds matured and sown in 1989 in greenhouse flats and burned each June from 1990 to 1995 had germinated to the following percentages by September 1995: buried and nonburned-2%, nonburied and nonburned-3%, buried and burned-3%, and nonburied and burned-39%. After five heating (to 80-90 °C)/incubation (25/15 °C) cycles, germination in flats from the burning experiment had increased to the following: buried and nonburned-60%, nonburied and nonburned-61%, buried and burned-45%, and nonburied and burned-71%. Furthermore, at least 65% of 1,800 seeds were viable and germinable after more than 3 years in the 'seed bank'. Thus, seeds of I. corei (1) require fire to germinate, (2) are capable of forming a long-lived seed bank, and (3) exhibit a continuum with regard to degree of seed coat dormancy. These results and those of others on the biology of I. corei and two of its closely related species, I. remota Greene and I. rivularis (Dougl.) Greene, were used to modify Buttrick's (1992) conceptual model of the population dynamics of I. corei in relation to fire and canopy development.