Interactions between higher plants and micro-organisms in natural ecosystems are among the most common and useful types of interaction between genetically distant organisms. Examples are associations of flowering plants with fungi forming Glomeromycota arbuskularną mycorrhizae , as well as more specialized legume endosymbiosis of soil bacteria belonging to the species of Rhizobium . Research paleontological fossils and phylogenetic estimates indicate that mycorrhizae can occur at the same time as terrestrial plants . On this basis, some scholars suggest that the colonization of land was all made ​​possible by a symbiosis of plants and mushrooms . A key role in the establishment of the molecular dialogue between the partners plays a symbiotic exchange of low molecular weight compounds signaling . These induce a multi-step and complex process of establishing a symbiotic relationship in which participates significant number of protein factors . Studies in recent years have shown that the establishment of the symbiosis between legumes and root nodule morphogenesis play an important role plant hormones cytokinins .