Role of temperature in the germination ecology of the summer annual Bidens polylepis Blake (Asteraceae)

sequentially to simulated March-October temperatures in incubators or (3) exposed to 25/15 or 30/15?C for 24 and 12 weeks, respectively. As seeds entered dormancy, they first lost the ability to germinate at 15/6?C and then at higher temperatures. Buried seeds exposed to seasonal temperature changes for 28 months in the nonheated greenhouse exhibited an annual dormancy/nondormancy cycle, with full dormancy occurring in September-November. Seeds came out of dormancy in winter (December-March), and they germinated to 8596% in light at simulated habitat temperatures from mid-April until July. Although 20-50% of the seeds germinated in darkness at simulated habitat temperatures in spring (March-June), only 2% of them germinated while buried in soil in the nonheated greenhouse. Thus, seeds have the potential to form a persistent seed bank.