4. Plant-Fungal Interactions: Special Secondary Metabolites of the Biotrophic, Necrotrophic, and Other Specific Interactions

Our environment is pervaded by a plethora of small exotic molecules, which are released without intermission by almost all organisms, like plants, microbes, or even animals. Plants and fungi are especially rich sources of these low-molecular-weight compounds, which are called secondary metabolites, and whose physiological functions are still mysterious in many cases. The number of the described compounds exceeds 100,000, and these molecules do not possess apparent importance in the producer’s life but regulate, modulate, induce, hinder, or even kill organisms other than the producer. Of course, these often unexpected substantial biological effects make these molecules so interesting and valuable. In this chapter, secondary metabolites from a plant and fungal interactions are surveyed considering hormones, antifungal metabolites, as well as the metabolites of mutualistic interactions observed between plants. Special secondary metabolites from biotrophic, necrotrophic, and specific interactions are also presented here, and their physiological and ecological roles and significances are discussed.