ROLE OF TEMPERATURE AND LIGHT IN THE GERMINATION ECOLOGY OF BURIED SEEDS OF WEEDY SPECIES OF DISTURBED FORESTS .2. ERECHTITES HIERACIFOLIA

At maturity in September, about half the seeds (achenes) of Erechtites hieracifolia (Asteraceae) collected in Kentucky were dormant (did not germinate at any test condition), whereas the others were conditional ly dormant (germinated only at a narrow range of test conditions). See ds sown on top of soil in an unheated greenhouse in September failed t o germinate in autumn because temperatures were below those required f or germination; however, they germinated at comparable temperatures th e following spring. Seeds buried in soil in September 1987 and exposed to natural seasonal temperature changes were nondormant (germinated o ver full range of test conditions) by April 1988, but they entered con ditional dormancy by October 1988. Each October through 1995, exhumed seeds exhibited conditional dormancy. Since 89% of the seeds were viab le after 8 years of burial, it appears that although seeds of this spe cies are wind dispersed, they also have the potential to form a long-l ived seed bank. Thus, soil disturbance at any time from May to Septemb er could result in establishment of plants from seeds in the seed bank .