Phytohormones are believed to play a role in numerous responses of plants to developmental processes and various stresses, but also in the establishment and development of symbiotic interactions with arbuscular mycorrhizal (AM) fungi. Jasmonates, known as regulators in the plant response to biotic or abiotic stress, are good candidates for such a role. Therefore, the functional analysis of jasmonates is done by reverse genetic approaches in several aspects: (i) the arbuscular mycorrhizal interaction, mainly the interaction between Glomus intraradices and barrel medic (Medicago truncatula); (ii) systemic wound response between shoots and roots of tomato (Solanum lycopersicum) and M. truncatula; and (iii) the formation of adventitious roots in the cuttage of Petunia hybrida. These projects will be complemented by the development of methods to detect jasmonates on cell- and tissue-specific level. Other projects cover the modulation of carbohydrate levels in transgenic plants and its effect on biotic interactions as well as the elucidation of mechanisms involved in the autoregulation of mycorrhization.