Symbiotic associations are of great importance in agriculture and forestry, especially in plant nutrition and plant cultivation with associations of rhizospheres being responsible for the biodegradation of many pesticides and crop protection products. In the field of environmental protection, the development and function of the ectotrophic and ect-endotrophic mycorrhiza (symbiotic association of the mycelium of a fungus with the roots of a seed plant) of coniferous and deciduous trees has assumed great significance in the search for the causes of the Continental Waldsterben (dying of the forests). Symbiosis of Plants and Microbes provides a lucid introduction to the subject for undergraduates and graduates. The emphasis is on describing the variety of symbiotic relationships and their agricultural and environmental applications.