Abstract: The internal and external causes of seed dormancy of Acer griseum were studied by inhibitor bioassay method and sulfuric acid treatment. Results showed that the water-absorption of A.griseum seeds was a slow process due to its thick woody pericarp. Water content of seeds of A.griseum reached only 68% after 140 h of water-absorption treatment. The sulfuric acid treatment for 3 h did not speed up the water-absorption, but made the percarp thinner without damaging seed viability. Inhibitory substances were detected in every part of the seed, including pericarp, seed coat, cotyledon and radicle. The cotyledon extracts had the stronger inhibitory effect on seed germination percentage and radicle growth than those from the pericarp and seed coat. The main reason for seed dormancy of A.griseum was physiological dormancy of seed embryo and physical obstacle of the pericarp. How to make the hormone reaching the seed embryo through the compact pericarp was the critical to break its dormancy quickly.

Key words: Acer griseum, seed dormancy, inhibitory substances, water absorption