Seed dormancy and germination in Rhexia mariana var. interior (Melastomataceae) and eco-evolutionary implications

Ninety-seven percent of the Rhexia mariana L. seeds collected in Tennessee were physiologically dormant at maturity in autumn, and they became nondorm ant during stratification. Light was required for germination, and seeds ge rminated to higher percentages on filter paper than on sand. Seeds buried i n soil in October 1992 and 1994 and exposed to natural seasonal temperature s were exhumed and tested for germination at monthly or bimonthly intervals for 30 and 32 months, respectively Seeds gained the ability to germinate t o greater than or equal to 80% at 30:15 and 35:20 degrees C during the firs t winter of burial and also at 25:15 degrees C during the second winter, bu t they did not re-enter dormancy. In contrast, seeds incubated at 20:10 deg rees C exhibited an annual cycle of moderate to high germination percentage s in winter-spring and low germination percentages in summer-autumn. Thus, germination can occur at habitat temperatures in Tennessee from April to Se ptember. This is the first report of physiological dormancy in seeds of the Melastomataceae in the temperate region. Like members of many plant famili es in temperate eastern North America, seeds of R. mariana (i) show a decre ase in the minimum temperature for germination as they come out of dormancy and (ii) exhibit some seasonal variation in the temperature range for germ ination. Thus, these dormancy or germination characteristics appear to be a daptations of species to the climatic conditions in temperate eastern North America.