The purpose of the first author's dissertation research is to compare seed dormancy-breaking and germination requirements of the three closely related species Aristolochia macrophylla, A. tomentosa (eastern U.S.), and A. californica (California). However, only results for A. macrophylla will be presented in this talk. Aristolochia macrophylla is a deciduous, woody vine found in mesic forests of the Appalachian Highlands Physiographic Division from southwestern Pennsylvania south to northern Georgia. Seeds of A. macrophylla have linear, underdeveloped embryos [1.99mm ± .08 (mean ±SE) in length] that more than double in size before they germinate. Embryos in fresh seeds incubated at 35/20, 30/15, 25/15, 20/10, and 15/6°C in light and in dark for 90 days grew in all regimes, but the fastest growth rate was at 25/15°C. Highest germination percentages occurred at 25/15°C, where 47 and 39% of the seeds germinated in light and dark, respectively, after 30 days and 70 and 45%, respectively, after 90 days. Twenty-three percent of the seeds that did not germinate in darkness at 25/15°C did so after they were transferred to light at this temperature regime. Further, 59% of the seeds that failed to germinate in light at 25/15°C did so after 12 wk of cold stratification, resulting in 85% total germination. Thus, some freshly-matured seeds in the population had morphological dormancy (MD) and others a combination of MD and physiological dormancy (PD), i.e., morphophysiological dormancy. PD was broken by cold stratification at 5°C, but embryos did not grow at this temperature. Fresh seeds cold stratified for 12 wk in light germinated to 96 and 95% in light and dark, respectively, after 60 days at 25/15°C, and those cold stratified in dark germinated to 95 and 74%, respectively. Preliminary data suggest that the seed dormancy-breaking requirements of A. macrophylla differ considerably from those of A. californica.

Key words: Appalachian endemic, Aristolochia, morphological dormancy, morphophysiological dormancy, seed germination, underdeveloped embryos