ABSTRACT
Growing populations and their greater longevity continue to increase the demand for both more food and fresh water. The phyllospheres and endospheres of plants can be considered as extensions of soil systems because they are inhabited by organisms for which the soil is also a habitat. The diverse populations of microbes that live in the phyllosphere – bacteria, fungi, yeasts, and others – provide the plant with various nutritional services and support its development in exchange for the water and energy that they receive from the plant. The structure of phyllosphere communities reflects the migration, survival, and growth of microbial colonizers, influenced by multiple environmental factors, by physical and chemical properties of the leaf, as well as by the relative fitness of the different species for living in these situations. Arbuscular mycorrhizal fungi are obligate plant symbionts, i.e., they cannot complete their life cycle when not resident in plant roots where they live as endophytes.
