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What is karrikin and how does smoke affect seed germination?

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Cluster of bright red seeds emerging from the cone-shaped fruit of a magnolia grandiflora, surrounded by large, glossy green leaves. — Seed Fruit and seeds of the southern magnolia (*Magnolia grandiflora*). The fruit is an aggregate of follicles, and each follicle bears a single red seed.

Karrikin is a chemical compound that acts as a stimulant for seed germination. While its precise mode of action remains somewhat obscure, it is known that karrikin can substitute for light to trigger the germination process in certain plant species.1

Smoke plays a critical role in the life cycles of many plants adapted to fire-prone environments, often referred to as pyrophytic plants. For these species, smoke and charred plant matter provide essential chemical signals that break seed dormancy. Some plants are so specialized that they will only sprout in the presence of these fire-related cues, allowing them to remain dormant in the soil seed bank for decades until a wildfire occurs. By responding to these signals, these plants are able to capitalize on the post-fire environment, where competition is reduced and the soil is enriched by ash.2