Seeds in suspension: Cell type-specific control of seed dormancy and germination initiation

Seed dormancy and germination are interconnected developmental processes that determine the timing of seedling establishment. Dormancy is an intrinsic inhibition of growth under otherwise permissive conditions, whereas germination corresponds to the resumption of embryo growth following dormancy release. Despite their interdependence, these processes are often conceptually conflated. Traditional research approaches have treated seeds as a tripartite structure, overlooking the extensive cellular heterogeneity within each compartment and cell type-specific mechanisms that underpin these transitions. This review synthesizes emerging evidence and recent advances in single-cell and spatial transcriptomic insights to propose a cell type-resolved framework. We highlight how cell populations within the embryo, endosperm, and seed coat differentially contribute to dormancy establishment, maintenance, release, and germination. The embryo functions as a site of signal integration, where spatially defined gibberellin biosynthesis and abscisic acid transport systems regulate the transition from dormancy to growth. The endosperm acts as both a hormonal regulatory center and mechanical constraints, coordinating ABA metabolism, inter-tissue signaling, and micropylar weakening required for radicle emergence, while the seed coat contributes to structural and biochemical constraints established during development. Revisiting the concept of a germination decision-making center in the embryonic radicle vasculature, we interpret this region as a spatially localized integration hub where antagonistic hormonal pathways converge, rather than a discrete control center. This cell type-specific perspective reframes dormancy and germination as emergent properties of coordinated interactions among specialized cellular domains, providing a foundation for predictive and mechanistic models of seed behavior.