The Effects Of Nitrogen Resource To The Biomass, Nitrogen Absorption And Nitrate Reductase Activity Of Ectomycorrhizal Fungi

Ectomycorrhizal fungi are a group of important fungi in soil. Selected ectomycorrhizal fungi could benefit potentially the growth, nutrition of the host plants as well as their resistance to drought, salt and diseases caused by insects and microorganisms after the infection of the host roots.Nitrogen is one of the most important nutrients in plant growth. Ectomycorrhizal fungi could take in and utilize NO₃^- -N, NH₄⁺-N and some organic nitrogen sources. Conclusionally, organic nitrogen is best for ectomycorrhizal fungi, NH₄⁺-N less, and NO₃ -N poorest. But NO₃ -N is the principal inorganic nitrogen absorbed and used by plant. The nitrate reductase (NR) can make NO₃ -N to be absorbed and used by plants. The nitrate reductase is first enzyme in NO₃^- -N assimilation in plants. A close relationship was found between the activity of nitrate reductase and nitrogen utilization in plants. It suggests that the activity of nitrate reductase could be used as a criterion of nitrogen assimilation during ectomycorrhizal growth in our previous experiment. The nitrate metabolism regulated by nitrate reductase is the essential and primary nitrogen metabolism system in plants.Ectomycorrhizal fungal strains involved in the present experiment were: three Lactarius deliciosus (Ld-1, Ld-2 and Ld-3, isolated from soils under Pinus Massoniana forest on Jinyun Mountain, Chongqing), Laccaria bicolor S238N (isolated from soils in centeral France in 1980s), Cenococcum geophilum SIV (isolated from pine growing soil in Spain in 1970s) and Pisolithus tinctorius 715 (isolated from an eucalyptus growing red soil in Xichang, China, in 1996). They were cultured in Pachlewski liquid mediums with NO₃ -N and NH₄⁺-N added, respectively, for several weeks. The objective of the research is to provide some scientific information for nitrogen utilization from the environment by ectomycorrhizal fungi and the isolation and culture of Lactarius deliciosus. 1. Growth and isolation of Lactarius deliciosus on PDA was better than that on Pachlewski. All selected tissues from of Lactarius deliciosus basidiocarps could grow PDA medium, indicating any tissues of basidiocarps could be used in isolation culture. According to the colors of secretion...