Cold stratification remodels carbohydrate metabolism to lower heat requirements for epicotyl dormancy release in...

Epicotyl dormancy represents a distinct form of seed dormancy in temperate tree species. This physiological mechanism delays shoot emergence relative to root growth until the seeds fulfill their specific heat requirement. While previous research has predominantly focused on seed germination, seedling emergence plays a more critical role in forest ecosystems by directly influencing population establishment. Cold stratification is known to facilitate the release of epicotyl dormancy in some species, yet its impact on the heat requirements for seedling emergence remains poorly understood. In this study, we proposed the heat requirement for the first time in epicotyl dormancy release and emergence and investigated the effects of cold stratification on the heat requirements for epicotyl dormancy release and seedling emergence in Chinese cork oak. Using a thermal time model, we demonstrated for the first time that cold stratification reduces the heat requirement for seedling emergence. Physiological analyses revealed decreased starch content alongside increased soluble sugar levels, following cold stratification. Transcriptomic and proteomic data further indicated that genes associated with secondary metabolite biosynthesis and carbohydrate metabolism were significantly enriched, suggesting a metabolic shift that reduces heat requirements. Our findings provide a novel model for calculating the heat requirements of seedling emergence in Chinese cork oak and offer new insights into the role of cold stratification in optimizing seedling establishment. This study advances our understanding of the physiological and molecular mechanisms underlying epicotyl dormancy release and highlights the importance of cold stratification in epicotyl dormancy.