Seed of the threatened annual legume, Astragalus contortuplicatus, can survive over 130 years of dry storage.

Long-term seed viability is of crucial importance for short-lived species, since persistent seed banks can buffer the fluctuations in the establishment of plants from year to year. Temporarily flooded habitats are an unpredictable environment for plants, and for some species the only chance they have of surviving is the formation of persistent seed banks. Astragalus contortuplicatus is an annual species of periodically flooded habitats and is considered an endangered species in Hungary. Altogether 1993 seeds of this species were tested in a germination experiment: 1200 were freshly harvested and 793 were collected from herbarium specimens of various ages. Seed viability was tested using the germination method. The freshly harvested seeds were used for selecting the best out of seven frequently used dormancy-breaking methods for this species. The highest percentage of germination was recorded for the combined treatment of scarification and light. Thus, this method was used to test the viability of the seeds collected from herbarium specimens. The oldest seeds that germinated were 131 years old. Until now there are no records of seeds of herbaceous legumes germinating that are more than 100 years old. This record is the 9th oldest of all the literature records of viable seeds originating from biological collections. All the seeds that germinated developed into healthy, fertile plants, the seeds of which also readily germinated. Fitted linear regression showed a significant negative relationship between seed age and percentage germination. Based on this linear regression the calculated theoretical maximum viability is 309 years. Our results suggest that seeds of A. contortuplicatus stored in collections can be successfully used in this species’ reintroduction for conservation purpose, to areas in which the plants were collected.