Karrikin 1 Modulates Germination and Growth of Invasive Solidago gigantea: Potential for Ecological Management and Photoblastism Research

Outside their native habitat, goldenrods (Solidago spp.) threaten ecosystem biodiversity through aggressive vegetative reproduction and by establishing dense stands. Climate-driven fire risks and illegal grassland burning increase exposure to smoke-derived compounds such as karrikins (KARs), which are known to regulate germination and development in many species but have never been studied in goldenrods. Understanding KARs’ effects on seeds and rhizomes is essential for predicting invasion dynamics and designing effective management strategies. This study aimed to determine whether karrikin 1 (KAR1) influences seed germination and rhizome bud development in Solidago gigantea, thereby affecting its invasiveness and offering a potential method of control. Two geographically isolated populations were analyzed using seeds, soil, above-ground plant biomass and rhizomes. Germination tests evaluated whether KAR mimics light and gibberellic acid (GA), a known germination stimulant. Greenhouse trials assessed rhizome response, while field experiments monitored whole-plant performance over two years. KAR stimulated seed germination comparably to light and GA and promoted seedling emergence from the seed bank, but it inhibited rhizome sprouting by about 15%. It also enhanced the emergence of other species, suggesting broad physiological activity and the potential to influence early-season plant community dynamics. These findings highlight KAR’s potential as a management tool for invasive goldenrod and provide new insights into smoke-derived compounds as ecological regulators.