Germination behaviour of forbs native to the southwestern United States following exposure to short-term seed bank conditions (−20°C)

Abstract

AbstractSeeds are increasingly being stored in seed banks for ex situ conservation, food security, and restoration reserves. Although it is hypothesized that seeds of many species can survive the dry, freezer conditions (−20°C) of seed banks for many years, shelf life is unknown for many species. In particular, changes to dormancy and germination requirements following freezer storage have not yet been studied extensively. To improve our understanding of how seed dormancy and germination respond to seed banking conditions, we evaluated seed of six restoration-priority species in the southwestern United States, which is a region of increasing restoration need. Germination tendencies of seeds that were and were not exposed to a −20°C treatment for 4–6 months were evaluated under 22 cold-moist stratification and incubation treatments to broadly assess changes to dormancy and germination requirements and speed. Direct or indirect (via interactions with stratification and/or incubation treatments) differences in dormancy breaking and germination were observed in seeds for four of the six species studied. Specifically, storage temperature accounted for differences in the final germination proportion, germination during stratification, and/or rate of germination in five of the six species. Notably, seeds of the one species that exhibit a combination of physiological and physical dormancy showed significant differences in all germination measures. However, while significant differences were found between seeds exposed to short-term seed bank storage and those that were not, these differences were small and may not be biologically meaningful, indicating that seed banking these species should not change how they are used for restoration or reintroduction purposes.