Effects of seed provenance on germination of herbs for agricultural compensation sites

The germination characteristics of European provenances of seven weed and grassland species which are used in agricultural compensation sites in Switzerland, for example on set-asides, were investigated along a W-E gradient (England, Germany, Switzerland, Hungary). In growth chambers the germination increment with temperature was different among the four main species and provenances tested. Consistently, the English provenances were least responsive. The germination rate of Silene alba increased most strongly with temperature, Daucus carota and Leucanthemum vulgare were intermediate, whereas Centaurea cyanus showed the lowest response to temperature. Germination of Daucus was enhanced by alternating temperatures, and this effect was significantly higher for the most distant provenances compared with the Swiss seeds. Also in Leucanthemum and Silene the foreign provenances showed a stronger effect of alternating temperatures, whereas seeds of Centaurea were not affected. In a common garden experiment Cichorium intybus, Daucus, Leucanthemum and Silene, but not Centaurea, revealed a trend towards lower germination with increasing distance of the provenance. Germination phenology of the different provenances varied in the above species and in Hypericum perforatum, except the arable weeds Centaurea and Papaver rhoeas. A principle component analysis confirmed that the overall variability among provenances was lowest in Centaurea, intermediate in Daucus and Leucanthemum, and highest in Silene. The results suggest provenance-specific adaptations which were partly correlated with the climate along the European gradient tested. Such adaptations can be used as an argument against the introduction of foreign seeds for ecological compensation sites.