Plant growth enhancement by endophytic fungi - Theory

Many definitions on fungal endophytes have been proposed to date that consider the living within healthy plant tissues as a prerogative of this issue. Mycorrhizal fungi also occur within roots that are symptomless and therefore the definition of endophyte would accommodate this group. Mycorrhizal symbionts however are usually treated separately since their lifestyles are considerably different from those of root endophytes, the structural and functional complexity of the interface with host roots being a distinguishing feature. On the contrary, the mutualistic role of non-grass endophytes is sometimes speculative and their ability to exchange nutrients hidden by the low level of specialization at the interface with host tissues. On the other hand, it is clear now that many fungal endophytes are host specific, either at the genus or family level. This implies a pivotal role of endophytes in plant evolution, made even more complex by the occurrence of different fungal species in the same root. Here we highlight the role of a fungal endophyte inhabiting peppermint plants by investigating the development of the fungus in time course and describe its effects on the root system. Thereafter, changes in essential oil content of peppermint induced by the fungus are addressed with respect to the growth response observed after root inoculation and the resulting effect on terpenoids metabolism.