Elevation impact on seed germination requirements for two Asteraceae species

Abstract

Elevation and latitude correlate with environmental factors that drive natural selection. Climate-change projections in the Great Basin suggest higher temperatures and increasingly lower annual winter snowfall, especially at low elevations. The transition from dormancy to germination represents a vulnerable stage of plant phenology, given the high susceptibility to death in newly germinated seedlings. Consequently, mechanisms involved with this phenomenon and its timing play an essential role in plant population fitness. This study investigates seed dormancy and germination for 2 co-occurring Asteraceae/Compositae species: arrowleaf balsamroot (<i>Balsamorhiza sagittata</i> (Pursh) Nutt.) and shiny mule’s ear (<i>Wyethia amplexicaulis</i> (Nutt.) Nutt.) from the same geographic area (near Provo Canyon, Utah) across an elevation gradient of 1584 m to 2438 m (5200–8000 ft). In laboratory experiments, seeds received increasing periods of cold stratification at 2 °C (35.6 °F) (from 4–20 wk) followed by incubation at 10 to 20 °C (50–68 °F). Shiny mule’s ear seeds from low (1584 m [5200 ft]) and mid (2011 m [6600 ft]) elevations required 8 wk of cold stratification while seeds from the highest elevation required 12 wk to reach 50% germination. Seeds of arrowleaf balsamroot from all elevations reached 50% germination after 16 wk of cold stratification although germination rate varied by elevation. These results suggest that selection pressure in contrasting environments results in variable dormancy-breaking durations, with implications for propagation, projected climate change, and seed sourcing in restoration efforts. Brown A, Allen PS. 2023. Elevation impact on seed germination requirements for two Asteraceae species. Native Plants Journal 24(1):45–53.