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Abstract

Sapium sebiferum, a highly ornamental and bioenergy plant, is propagated by seed. Its seed coat contains germination inhibitors and needs long time stratification for germination. In this experiment, we discovered that S. Sebiferum seed coat (especially tegmen) and endospermic cap contained high levels of proanthocyanidins (PAs). Seed coat and endospermic cap removal induced seed germination whereas exogenous application with seed coat extract (SCE) or PAs significantly inhibited this process, suggesting that PAs in the seed coat played a major role in regulating seed germination in S. sebiferum. We further investigated how seed coat extract affected the expression of the seed germination-related genes. The results showed that SCE treatment upregulated the transcription level of the dormancy-related gene, abscisic acid (ABA) biosynthesis and signalling genes and gibberellins (GA) suppressing genes. SCE decreased the transcript levels of ABA catabolic, GA biosynthesis, reactive oxygen species (ROS) and nitrates signalling genes. Exogenous application of nordihydroguaiaretic acid (NDGA), gibberellic acid (GA 3), hydrogen peroxide (H 2 O 2) and potassium nitrate (KNO 3) recovered seed germination in SCE supplemented medium. In this experiment, we highlighted the role of PAs, and its interactions with the other germination regulators, in the regulation of seed dormancy in S. Sebiferum.