Astragalus resilience: Heat shock effect on seed dormancy and germination in endangered species

Many Astragalus species exhibit physical dormancy and understanding their seed dormancy is crucial for conservation efforts. Previous studies have revealed that impermeable seed coats inhibit germination in these species, but little is known about the ecological context of this dormancy. We focused on Astragalus maritimus and A. verrucosus, two threatened endemic species in Sardinia living in fire-prone ecosystems, to explore the ecological implications of heat shock on dormancy release and germination.We investigated under laboratory conditions the effects of different heat shock treatments (40–140°C) for varying durations (5 and 10 minutes), to simulate different fire conditions. Results showed a reduction of germination compared with control test only at high heat shock temperatures (120–140°C) in both species. Most seeds remain dormant (viable, not imbibed seed) after the simulation of fire in the soil, from 80% at 40°C – 5 min to 20% at 120°C – 5 min for A. verrucosus. While A. maritimus dormant seeds varying from 84.2% at 40°C – 5 min to 40% 100°C – 10 min. At higher temperatures of heat shock, the percentage of dead seed increases, A. verrucosus ranged from 55.4% at 120°C – 5 min to 99% at 140°C – 10 min and for A. maritimus this ranges varied from 54% at 100°C – 10min to 92% 140°C – 10 min. In conclusion, heat shock caused by fire is not able to break the physical dormancy. However, they can survival the fire pass and develop soil seed bank that persists after fires and delay germination until the occurrence of break dormancy conditions.