Effect of storage time, site and floral morph on seed germination of the threatened distylous primrose Primula cusickiana var. maguirei

Abstract

AbstractEx situ conservation of rare plant species requires an understanding of germination requirements. We report the first successful germination trials for Maguire primrose (Primula cusickiana var. maguirei[L.O. Williams] N.H. Holmgren & S. Kelso), a threatened perennial herb narrowly restricted to a 20‐km canyon in northern Utah, USA. Seeds collected from different sites (upper or lower canyon populations) and flower morphs (pin or thrum) that had been stored for either 1 or 2 years were cold, moist stratified in darkness at 1–2°C for 270 days. Independent of treatment, time to first germination was approximately 75 days, time to 50% germination (T50) was approximately 165 days, and total germination was 55.8%. Higher mean germination was observed in seeds stored for 2 years compared with seeds stored for 1 year, as well as in seeds from pin flowers compared with thrum flowers. There was not a significant effect of site on mean germination, but there was a significant storage time × site interaction. Seeds stored for 2 years also had a lower mean T50 versus seeds stored for 1 year. In addition, seeds from upper canyon populations had a higher mean T50 than those from lower canyon populations. Our results suggest that short‐term storage should not significantly decrease seed viability, and that both flower morph and canyon location may influence germination. Evidence suggests that germination patterns are adaptive. Our results contribute to our understanding of the germination biology of P. cusickiana var. maguirei and inform future conservation efforts for this threatened species.