Abstract: Drought resistance of Cinnamomum camphora seedlings inoculated with different AM fungi (Glomus etunicatum and G.lamellosum) under drought stress in Karst soil was studied in this paper. The 80 d-old seedlings were exposed to four drought stress treatments of 60 days: severe (35%~45% of field capacity, FC), moderate (50%~60% of FC), mild (65%~75% of FC) and well watered (80%~90% of FC). Biomass accumulation of individual plants and osmoregulation in the leaves were measured in this paper. The results showed that: (1)Biomass of seedlings significantly increased after the AM fungus inoculation. The order of effects on biomass showed moderate>mild>well watered>severe in all water treatments, G.etunicatum>G.lamellosum as well. There were significant differences in seedlings biomass between well watered condition and severe water stress but not between moderate and mild water stress. (2)It represented a better mycorrhizal dependency of plants under moderate water stress compared with all the other water conditions while differences in dependency were significant under severe stress but the others were not, mycorrhizal dependency of C.camphora inoculted G.etunicatum was higher than G.lamellosum in all water treatments. (3)Compared with non-inoculated plants, concentration of soluble sugar, soluble protein and proline were higher while malondialdehyde was lower in leaves of inoculated plants. There was a tendency of G.lamellosum>G.etunicatum>ck for soluble sugar, soluble protein and proline in leaves under well watered condition, however it changed G.etunicatum>G.lamellosum>ck while water decreased. The concentration difference in malondialdehyde was not significant. However, it decreased rapidly in G.etunicatum compared to G.lamellosum while enhancing water stress. The ranks of malondialdehyde contents were G.etunicatum<G.lamellosum<ck with the enhancement of water stress. There were significant differences among three inoculation treatments under severe water stress. Analysis of correlations of metabolic substances showed that there was extremely significant correlation between soluble sugar and proline while significantly negative correlation between protein and malondialdehyde in host plants leaves. (4) The differentiation of AM fungus on drought resistance was distinct when water stress was aggravated. As a whole, drought resistance of G.etunicatum was better than G.lamellosum species in Karst area restoration.

Key words: AM fungi, Cinnamomum camphora, water stress, drought resistance