The effect of multiple fire cues on germination of groundplum milkvetch (Astragalus crassicarpus Nutt.)

Abstract

Groundplum milkvetch (Astragalus crassicarpus Nutt. [Fabaceae]) is a native herbaceous forb found in the Great Plains of North America that has high seed dormancy. Previous research found that despite 100% viability, no seeds germinated without treatments to alleviate dormancy (scarification with sandpaper). The goal of this project is to expand on that research and examine the efficacy of additional treatments to alleviate dormancy in groundplum milkvetch seeds. Treatments were designed to mimic fire cues (dry heat, flaming, and smoke) along with a control (no treatment) and scarification. Historically, the Great Plains had frequent fires to which native plants were exposed so it is a reasonable question to ask if fire cues promote germination. We found that the seeds responded to treatment. Final germination percentage was greatest in seeds treated with dry heat or scarification. Smoke treatment did not impact germination differently than the control. Flaming resulted in a faster rate (seeds per day) of germination but longer time to germination compared to the control. Results suggest that groundplum milkvetch seeds did sense and respond to temperature-driven fire cues, but not chemical-driven (smoke), and that dry heat may be the best treatment to promote germination of groundplum milkvetch seeds.