Proanthocyanidins (PAs) as the end products of the flavonoid biosynthetic pathway mainly accumulate in seed coat but their biological function is largely unknown.In this study, we examined their anti-oxidant ability in seed coat and germination variations under low and high oxidative stresses in PA-deficient mutants of Arabidopsis.Compared with wild-type, the germination rate of PA-deficient mutants was higher under low oxidative stress, while under high oxidative stress the germination rate of PA-deficiency mutants was lower.Pharmacology experiments were used to confirm the anti-oxidative ability of PAs in vivo in Arabidopsis seed, which was further supported by complementation analysis.Additionally, PAs inhibit seed germination mediated by ABA signaling under oxidative stress was investigated by using ABA signaling mutants.Our results show that oxidative stress and ABA signaling collaborated to determine the difference of germination between wild-type and PAs-deficiency mutant seed.