A comparative study of the seed germination biology of a narrow endemic and two geographically-widespread species ofSolidago(Asteraceae). 3. Photoecology of germination

Abstract

AbstractRegardless of whether or not seeds of the geographically-widespreadSolidago altissimaandS. nemoraliswere exposed to light in autumn, those ‘dispersed’ in autumn (15/°C) or winter (5°C) required 12 weeks of light in winter to germinate to ≥80% in darkness in spring (2 weeks at 20/10°C). On the other hand, seeds of the narrow-endemicS. shortiidispersed in autumn and exposed to ≥2 weeks of light in early winter germinated to ≥77% in darkness in spring, and those dispersed in winter and exposed to ≥6 weeks of light germinated to ≥82%.S. altissimaandS. nemoralisseeds not exposed to light during any season germinated to only 0–1% in darkness in spring, whereasS. shortiiseeds germinated to 45–56%. Seeds ofS. altissimaandS. nemoraliskept in darkness in autumn and winter needed a 1-day (14-h photoperiod) light exposure in spring to germinate to ≥75% in darkness, whereas those ofS. shortiirequired only one 5-s exposure. Cold-stratified (nondormant) seeds ofS. altissima, S. nemoralisandS. shortiiexposed to light with a high far-red/red ratio germinated to significantly higher percentages than dark controls and freshly-matured and lab-stored seeds. Results of this study suggest that a soil seed bank ofS. shortiishould be smaller and be depleted at a faster rate than those ofS. altissimaandS. nemoralis, and portions of the seeds of the three species can germinate in the far-red-enriched light under plant canopies.