Relationships behveen microorganism and plants -a reviewRelationships between microorganisms and plants are considered to be an important part of microbial ecology. At present, their study is more concerned with the rhizosphere and less with the phyllosphere. Different microecological aspects of these relationships, furthermore the relationships between individual groups of microorganisms and also biochemical effects of microorganisms on plants are thoroughly examined. Nitrogen fixing bacteria, mycorrhizal fungi and phytopathogenic microorganisms are emphasized because of their particular importance for plant growth. Modem working methods (i.e. scanningelectron microscopy, radiometry, gas chromatography, etc.) are widely used. For a closer examination of very complex problems, the micro-organisms-plants relationships should be consequently considered to be a part of an open ecological system with mostly continual nutrient cycling.