Abstract:In order to understand the response to combined stresses of cadmium (Cd) and naphthalene (Nap), the germination and growth of mangrove plant Avicennia marina seedlings were studied cultured on sand in greenhouse. The results showed that the inhibition effect of seedling germination under Cd-Nap combined stress was more obvious than that under Cd stress. The survival rate increased at early stress stage, and then decreased at later stress stage. After cultured for 45 days, the inhibition effect of Cd on leaf size, stem height and biomass relieved treated with 10 mg L-1 Nap, while inhibition effect on root growth enhanced. Compared to treatment with 25 mg L-1 Cd, the area, length, width of leaf, stem height and biomass treated with 10 mg L-1 Nap-25 mg L-1 Cd increased by 9.6%, 7.9%, 7.4%, 5.1% and 20.2%, respectively, while root length decreased by 11.1% compared to treatment with 150 mg L-1 Cd. When cultured for 90 days, the inhibitive effect of Cd-Nap stress on leaf size, stem height and root growth was stronger than that of Cd stress, but there was no significant difference in biomass. Therefore, with extension of combined stress time, the antagonistic effect of Cd-Nap on A. marina seedling growth turned into synergistic effect.