Abstract:The study used seeds of Paeonia rockii treated with different concentrations of gibberellic acid (GA3) to investigate the effects of rooting. Meanwhile, the seed coat surface decoration of P. rockii was observed by scanning electron microscopy (SEM) and endosperm structure by fluorescence inversion microscopy and transmission electron microscopy (TEM). Our purpose is to investigate the effect of GA3 on the hypoderm of P. rockii seeds, the changes of seed coat and endosperm structure and effect of rooting during axle dormancy release. (1) GA3 treatment could effectively promote the rooting of P. rockii seeds. 300 mg/L GA3 treatment was the best to promote rooting with the highest rooting rates of 62.33% and made the first seed rooting time shorter 14.66 days than that of control treatment. (2) Scanning electron microscopy (SEM) showed that the seed coat of P. rockii contained wax. During seed maturation, the wax content increased obviously, the mesh on the seed coat surface disappeared gradually, and the seed coat shrank obviously. (3) The results of optical microscopy showed that the endosperm cells of P. rockii seeds with GA3 treatment contained more amyloid and proteasome, which accumulated gradually during seed germination and provided enough nutrients for seed germination. (4) Transmission electron microscopy (TEM) showed that seeds with GA3 treatment macromolecule nutrients in the endosperm gradually decomposed, mitochondria, endoplasmic reticulum, golgi apparatus appeared, and its hypocotyl dormancy was broken and cell wall was thinner and ablated later, which was conducive to nutrient transport. It can be seen that GA3 treatment can effectively accelerate the change of seed coat structure and endosperm cell metabolism, and promote seed germination. 300 mg/L GA3 treatment for 24 hours can perform the best rooting efficiency.