Seed germination of gypsophytes and gypsovags in semi-arid central Spain

Seed germination under controlled conditions was studied for six restricted gypsophytes and five gypsovags, three with calcareous preferences and two of salt optima, most of them local endemics of the central Iberian Peninsula. The main aim of this study can be briefly summarized as: is germination of these plants one of differential factors acting on the high biological selective availability of gypsum soils or are these plants similar at this biological stage to surrounding plants, not edaphisms? Our results suggest that both gypsophytes and gypsovags present the typical germination strategies of semiarid Mediterranean plants: efficient responses at low temperatures, multipurpose strategies and heteromorphism within and among seed populations, and clinal variation in seed dormancy. These two types of edaphisms do not differ significantly in their germinability behaviour and the detected variability can be easily explained by the taxonomic groups to which these plants belong. It seems patent that gypsum has acted interactively at the seedling and mature stages of these plants, but it has not forced different strategies at the germination stage. (C) 1997 Academic Press Limited.