From molecular decline to regeneration failure: seed aging in European beech (Fagus sylvatica) challenges the conservation of forest reproductive material.

European beech (Fagus sylvatica L.) is a keystone species in temperate forests in Central and Western Europe. However, its regeneration is increasingly constrained by erratic seed production, climate variability and poor storage of its partially desiccation-sensitive seeds. Rapid loss of viability during seed storage poses a major obstacle to the conservation. This review synthesizes current knowledge of the physiological, biochemical and epigenetic processes involved in the aging of beech seeds. Oxidative stress emerges as a central driver: the accumulation of reactive oxygen species (ROS) after seed shedding disrupts membrane integrity, impairs mitochondrial respiration and accelerates programmed cell death, whereas controlled ROS levels also act as essential signaling molecules during germination. Mitochondrial decline progressively reduces energy supply during hydrated storage, while epigenetic instability, particularly DNA hypomethylation, weakens macromolecular repair and germination potential. The decrease in protective molecules, including dehydrins and raffinose family oligosaccharides, together with other aging-related processes, contributes to the rapid decline in beech seed viability during conventional moist storage at low temperatures. We argue that effective conservation strategies must integrate early molecular diagnostics (e.g., ROS accumulation, DNA methylation, mitochondrial respiration) with improved drying, freezing and cryopreservation protocols. By explicitly linking cellular mechanisms of seed aging to regeneration failure and forest-scale resilience, this synthesis underscores the urgent need for adaptive management to safeguard the regeneration potential and ecosystem resilience of Fagus sylvatica in a rapidly changing climate.