Short-term cell death in tissues of Pulsatilla vernalis seeds from natural and ex situ conserved populations.

Pulsatilla vernalis is a IUCN listed species that occurs in mountain and lowland habitats. The seeds collected from different populations are remarkably diverse in their viability depending on locality or year of collection. We aim to analyse seed viability, among others, by investigation of the percentage of alive, dying, and dead cells in embryos and endosperm when comparing the seeds from a wild lowland population and ex situ cultivation of plants of lowland and Alpine origin. The cell death was detected by staining with two fluorescence probes, one penetrating only the changed nuclear membranes, the other penetrating also the unchanged cells. 54.5% of Alpine origin seeds were presumably capable of germination if they were sown after collection, however, four months later only 36.4% had healthy embryos. In the case of lowland wild plants it was 31.8% and 18.2%, and from ex situ, 27.3% and 13.6%, respectively. 27.3% of Alpine origin seeds had embryo in torpedo stage (9.1% in the case of lowland seeds). Mean weight of the former was 2.9 mg (2.0 mg in lowland ones). Our results confirm the significance of seed origin and seed weight on viability, and that Pulsatilla seeds have a short 'germination time window'.