Does gypsum influence seed germination?

Flora inhabiting gypsum outcrops in arid environments shows a high level of specialization. However, the processes involved are still unclear, specifically at the key stage of germination. Here, to assess whether gypsum could chemically influence seed germination, we tested the germination of species according to 3 functional groups: gypsophiles, gypsovags, and calcicoles. A total of 24 taxa were selected, all occurring in gypsum and limestone substrates, under a semiarid and dry Mediterranean climate. Three levels of gypsum (CaSO4 center dot 2H(2)O) solution (low = 0.5 g/L, medium = 1 g/L, and high = 2.4 g/L) and 1 control treatment of distilled water were tested. Results depended on the particular species rather than on the functional group. We found that gypsum favored germination in some species (Lepidium subulatum L. and Gypsophila struthium L.), whereas significant negative effects appeared for only 1 species (Rosmarinus officinalis L.). In contrast, most of the species studied responded neutrally to gypsum solutions. Our results suggest that chemical features of gypsum could offer an advantage at the germination stage for certain species, rather than posing a constraint for seed germination.