Dormancy, Germination and Mortality of Seeds in a Chalk-Grassland Flora

SUMMARY (1) Seeds of thirteen herbaceous species from chalk grassland in The Netherlands were buried in their natural habitat. Samples were exhumed at regular intervals over 3 years. Mortality and germination in situ were recorded. The surviving seeds were tested for germination in light and darkness and with different temperature regimes. (2) Seed mortality was low, except in Gentianella germanica and Origanum vulgare. In Carlina vulgaris, Leontodon hispidus and Scabiosa columbaria disappearance of seeds was mainly caused by germination in the soil. (3) Freshly harvested seeds of Arenaria serpyllifolia and Linum catharticum had an absolute light requirement for germination which was retained during burial. Burial induced a light requirement for germination in Origanum vulgare. (4) All species that germinated showed some degree of primary dormancy and seasonal change in secondary dormancy. This was most pronounced in shortlived species. (5) The seasonal change in secondary dormancy of surviving seeds was most evident either from germinability in light (Arenaria, Daucus carota and Linum), in darkness ( Carlina, Leontodon, Plantago lanceolata and Scabiosa), or both (Centaurea scabiosa). The response of the seeds to temperature also varied seasonally. (6) The amplitude of seasonal change in dormancy tended to decrease during the 3-year of burial in some species (Arenaria, Linum and Daucus). (7) Rhinanthus minor and R. alectorolophus seeds only germinated in late winter and were dormant during the remainder of the year.