Abstract: The effects of antioxidant system on the ultradry seed of Brassica caulorapa Pasq. were investigated. Ultradry treatment did not cause any changes in seed germination percentage and vigor index in the seed of B .caulorapa. Further more , it improved the storability of the seed during 30 days of accelerated ageing. Ultradry treatment enhanced superoxide generation rate , but did not affect the level of malondialdehyde (MDA) and the activities of antioxidant enzymes such as superoxide dismutase (SOD) , catalase (CAT) , guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) in B . caulorapa seed. After 10 days of ageing treatment at 50 ℃, both the superoxide generation rate and the MDA content were lower in ultradried seed than in the control . The content of ascorbic acid (AsA) was higher in ultradried seed than in the control . Once rehumidified and imbibed , the antioxidant enzymes in the ultradried seed played a very important role to scavenge the ultimate product of lipid peroxidation reduced during seed storage in order to maintain the seed germination ability. A more stable antioxidant system was maintained in ultradried seed , which should account for the high vigor of the ultradried seed.

Key words: Ultradry, Brassica caulorapa Pasq., Seed, Antioxidant system