ROLE OF TEMPERATURE AND LIGHT IN THE GERMINATION ECOLOGY OF BURIED SEEDS OF POTENTILLA-RECTA

Fresh, mature seeds of the perennial weed, Potentilla recta L. (Rosaceae), were buried in early July of 1984 and 1985 and exposed to natural yearly temperature cycles. At monthly intervals for 28 (1984 seeds) and 25.5 (1985 seeds) months, seeds were exhumed and tested in light and darkness at 12/12 h alternating temperature regimes of 15/6, 20/10, 30/15 and 35/20-degrees-C. At the time of burial, 2-38% of the seeds germinated in light at 15/6 and 20/10-degrees-C, but none germinated at any of the other test conditions. During summer, seeds after-ripened, and by October they germinated to 41-87% in light at all thermoperiods. Seeds never gained the ability to germinate in darkness. Although buried seeds subsequently were exposed to low winter and high summer temperatures, they did not re-enter dormancy or exhibit cyclic changes in germination responses. Thus, buried seeds can potentially germinate during any month of the growing season, if a disturbance brings the seeds to the soil surface and moisture is nonlimiting. However, only 23 to 50% of the exhumed seeds germinated at the July and August temperature (35/20-degrees-C) in July and August.