| The paper studied native shrub---Ostryopsis davidiana in Daqing Mountain of Inner Mongolia, discussed mycorrhizal characteristic and their drought resistance mechanism, and selected superior ectomycorrhizal fungi of survival shrub-- Ostryopsis davidina by inoculating 5 different ectomycorrhizal fungi (6 strains) to it. The ectomycorrhizal synthesis were studied on Ostryopsis davidina, including Ceno- coccum geophilum (C.g for short) isolated from the roots of Ostryopsis davidina on Da- qing Mountain, 2 strains of Suillus grevillei collected under forests of Larix principis- rupprechtii and Betula platyphylla on different sites of Daqing Mountain (P-S.g and M- S.g for short), Suillus granulatus under Pinus tabulaeformis (S.g for short); 2 widespre- ad fungi--Pisolithus tinctorius (P.t270 for short) and Paxillus involutus (P.i for short) in- troduced from foreign country. Ectomycorrhizal morphology of inoculated seedlings for 4 months was observed, and ectomycorrhizal infection rates and biomass were measured. The results revealed that ectomycorrhiza were formed on roots of Ostryopsis davidina after inoculated ectomycorrhizal fungi. Ectomycorrhizal infection rates reach at least 40.80% and no infection on control. Ectoycorrhiza formed between P.i and Ostryopsis davidina or S.g and Ostryopsis davidina are yellowish to brown yellow, claw or monop- odial. Mycorrhiza between P.t270 and Ostryopsis davidina are brown to dark brown, mo- nopodial and pinnate. Mycorrhiza between 2 strains of S.g and Ostryopsis davidina are yellowish and translucency, monopodial or dichotomous. Whereas Mycorrhiza formed between C.g and Ostryopsis davidina are black, like bulb. Typical Hartig net structure was formed among the corticous cell, and the structure have difference between different fungi. No Hartig net was formed on uninoculated seedlings. All these fungi acelerate the growin- g of Ostryopsis davidina at different degree. The biomass of seedling sinoculated with P.i was2.1 times as control and the ratio of root to stem was 73.27% as control. The paper also studied drought resistance mechanism on 4 months different mycorrh- izal seedlings and measured the leaf carnification extent, water content and water poten ti- al. The results indicated that the leaf carnification extent was enhanced and trees inoculate- ed with P.t270 increased by 9.69% in contrast to control. The content of free water and bo- und water was increased on seedlings inoculated with each fungus. The ratio of bound wa- ter to free water enhanced by 35.14% on leaves of seedlings inoculated with P-S.g. The water maintenance was enhanced and the water saturation deficit was reduced. While in c- ontrast to control, 46.46% was reduced by on mycorrhizal seedlings of C.g. The wilting ti- me was postponed 44 hours. Water potential was increased on mycorrhizal seedlings. In c- ontrast to control, 200% was increased by on seedlings inoculated with C.g and Pt270. Ch- lorophyll increased and 17.62% was increased by on mycorrhizal seedlings of P.t270. Effe- ctive photosynthesis was strengthened and in contrast to control, 2 times were increased by on mycorrhizal seedlings of P.i under natural conditions, while they were 3.56 times as co- ntrol under threatening conditions. The paper further discussed the biochemical mechanis- m of ectomycorrhizal seedlings under drought resistance. The activity of SOD in plant bo- dy was enhanced and 19.41% was enhanced by on mycorrhizal seedlings of P.t270. The SOD enzyme cleared O2- effectively and reduced the level of overoxidation and lightened the damage level of membrane. Themeasurement of relative dialytic indicated that the damage extent was alleviated and 40.77% was lowered on mycorrhizal seedlings of C.g, which in close contact with the activity of SOD.
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