Germination ecology of some dune slack pioneers

The effects of temperature, light, burial and salinity on the germination of Centaurium littorale (Turner) Gilmour, Samolus valerandi L. and Parnassia palustris L. are compared. Each species exhibits an almost absolute requirement for light. Germination does not occur below a day temperature of 15°C. The enforced dormancy, imposed by salinity is too weak to prevent germination at moderate salinity levels, which may cause considerable mortality after germination. Samolus valerandi and Parnassia palustris exhibit innate dormancy, which is rapidly broken by cold stratification. None of the species is liable to induction of secundary dormancy by adverse environmental conditions. The seed variability is remarkably low, implying that under almost any set of environmental conditions the germination will be either rapid and complete, or completely inhibited. The germination behaviour is discussed in relation to habitat and seed characteristics. It is argued that very different types of germination strategies may be successful in dune slack habitats.