Two-hundred-year seed survival of Leucospermum and two other woody species from the Cape Floristic region, South Africa

The ability of orthodox seeds to survive long-term dry storage is a key prerequisite for ex situ seed conservation in genebanks. However, only a few credible observations of seed survival for >= 200 years have been reported. In this paper, seed survival is shown for three species under suboptimal storage conditions for a documented time of >= 203 years and carbon dated at 218-270 years. Two species that germinated are in the Fabaceae (Liparia sp. and Acacia sp.). A water-impermeable seed coat, and hence an inability to equilibrate with ambient relative humidity, may contribute to long-term survival of these species. The third species that germinated (Leucospermum sp.) does not have a water-impermeable seed coat, and long-term survival may be linked to an oxygen-impermeable barrier in the seed. These results for species from the Cape Floristic Region, South Africa, suggest adaptation for extreme longevity in seeds of species of seasonally dry, Mediterranean environments.