Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Interactions between root symbionts, root pathogens and actinorhizal plants. | 765s Ann. Sci. For. 1989 46 suppl. 765s-771s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Interactions between root symbionts root pathogens and actinorhizal plants A. Akkermans D. Hahn and F. Zoon Department of Microbiology Wageningen Agricutural University Wageningen The Netherlands Introduction Actinorhizal trees with nitrogen-fixing acti-nomycetes Frankia sp. as microsymbionts in root nodules play an important ecological role as pioneer plants on nitrogen-poor soils. Up to 200 perennial species all trees and shrubs distributed over about 20 genera have been found to be nodulated with Frankia as the nodule symbiont. Some of those . Alnus spp. in temperate regions and Casuarina spp. in subtropical and tropical regions have great potentials for biomass production and erosion control Silvester 1977 . The growth of such plants is largely dependent upon the presence of proper Frankia strains in the soil. Although Frankia has been found in many types of soil particularly in soils where its host plants have been grown previously Fraga-Beddiar 1987 Houwers and Akkermans 1981 Rodriguez-Barrueco 1968 inoculation of the plants with selected Frankia strains can give a positive response with respect to plant yield. Pot and field experiments have indicated that the effect of inocula tion of plants with Frankia is dependent upon the environmental conditions including the interaction with other soil microorganisms van Dijk 1984 Houwers and Akkermans 1981 Maas et al. 1983 Oremus 1980 Oremus and Otten 1981 . These results indicate that plant growth is often limited by factors other than N2 fixation. Each soil ecosystem comprises a large number of different types of organisms with a complex network of interactions. Tree growth is therefore affected by interaction with many different types of organisms. In soil the roots are in close contact with pathogenic fungi nematodes and insects but also with symbiotic organisms such as mycorrhizal fungi rhizo-bacteria and .
