Germination traits and seed‐bank dynamics of a biennial plant, Oenothera glazioviana Micheli

A study was conducted on the germination traits and seed‐bank dynamics of Oenothera glazioviana (=O. erythrosepala ), which sets seed in August in sand‐dune systems in Japan. More than 90% of freshly matured seeds germinated over a wide range of temperature in light, but less than 10% did so in continuous darkness. Stratification (chilling under moist conditions) was ineffective in diminishing the light‐requirement for germination. When fresh seeds were imbibed for 24 h including a 12‐h light period, followed by 7‐day air‐drying, 94% of them became germinable in the dark at 25°C, but remained dormant at less than 15°C. of seeds collected in March from capsules of dead plants, 58% germinated in the dark at 25°C. After four cycles of alternatc 1‐day wetting followed by 2‐day drying or 1.5‐day wetting followed by 1.5‐day drying under a 12‐h photoperiod, the fraction of viable seeds declined from 76% to 40% and 22%, respectively, due to germination during the wet periods. Seed‐bag experiments were conducted in the field, using seeds given and not given a light‐stimulus. Forty percent of the light‐stimulated seeds germinated in the soil, whereas the seeds without a light‐stimulus remained dormant throughout the experiment. When seeds were placed on the soil surface or at a depth of 0.5‐1 cm, the proportion of germinable seeds declined during late spring and autumn, but not during winter and early spring. The seed‐bank size of a natural population just prior to current seed dispersal was 2–3% of the seed production in the previous year, suggesting a high turnover rate of the seed‐bank.