Primary metabolite mobilization and hormonal regulation during seed dormancy release in Cornus japonica var. chinensis

The combination of gibberellin acid (GA) soaking with moist chilling plays a pivotal role in seed dormancy breaking. However, knowledge involving physiological and biochemical mechanisms for such a response is limited. This work focused on the effects of GA₃ and moist chilling on overcoming seed dormancy as well as the response of endogenous hormones and nutrient reserves to dormancy release in Chinese dogwood (Cornus kousa var. chinensis). Seeds subjected to GA₃ soaking and moist chilling exhibited a high germination percentage (average 97%), and the combination of 500 mg·L^?1 GA₃ soaking for 3 days followed with moist chilling for 50 days was more effective than other treatments. For GA₃ treatments, lipids were initially hydrolyzed during the first stage of moist chilling (0–20 days), resulting in the increase of starch and soluble sugars, while proteins were kept relatively stable. During the second stage (20–50 days), contents of lipids, starch, soluble sugars, and proteins decreased by 46%, 82%, 61% and 59%, respectively. Abscisic acid (ABA) contents and ratios of ABA to GA₃ in GA₃ treatments decreased by nearly 70% and over 90%, respectively, when dormancy was terminated. However, endogenous GA₃ contents in all treatments significantly increased with prolonged moist chilling. The present results provide insight into the metabolic mechanism involving hormonal regulation and mobilization of reserves during the release of seed dormancy in Chinese dogwood.