Temperature-driven dormancy loss shapes subsequent germination thermal requirements in Centaurium somedanum

Abstract Seed dormancy is a key mechanism regulating germination timing by determining how seeds respond to environmental cues. However, the extent to which temperatures experienced during dormancy loss alter subsequent germination thermal requirements remains poorly understood. We investigated this process in Centaurium somedanum , a narrow endemic of calcareous mountain springs in northern Spain, with non-deep simple morphophysiological dormancy. Seeds from eight populations were stratified for 0, 6 or 12 weeks at 0, 5 or 10 °C and then incubated across a range of constant temperatures. Cumulative germination curves were fitted using log-logistic models, final germination was analysed with mixed-effects models, and thermal thresholds were estimated from regressions of germination rate against temperature. Prolonged cold stratification, especially at 0 °C, produced the highest final germination and the fastest subsequent germination responses, whereas stratification at 5 or 10 °C was less effective. After 12 weeks at 0 °C, germination followed a unimodal thermal response, with mean cardinal temperatures of 5.4 °C ( T b ), 17.6 °C ( T o ) and 29.5 °C ( T c ). These results show that cold exposure acts as a mechanism controlling dormancy loss before thermal-time accumulation can proceed. Thus, regeneration in C. somedanum depends on a sequential interaction between winter cold and subsequent favourable temperatures.