The Beneficial Effect of Mycorrhizae on N Utilization by the Host-Plant: Myth or Reality?
Résumé
The chapter ‘The Beneficial Effect of Mycorrhizae on N Utilisation by the Host-Plant: Myth or Reality?” aims at summarizing the present knowledge about the role of three main types of mycorrhizal associations made by ericoid, ectomycorrhizal and arbuscular mycorrhizal fungi in the nitrogen nutrition of the host plant. The capacities of these ectomycorrhizal fungi to influence N mineralization in different ecosystems and N uptake by the mycorrhizal plant are first presented. Then, labelling experiments and molecular studies that have been carried out so far to highlight N transfer from the fungal cells to the host cells are described. Finally, data enabling us to assess the importance of N transfer in the N budget of the mycorrhizal plants in “real life” are considered. From the available data in the literature, it can be concluded that the mycorrhizal fungi are able to use a variety of N sources, as their host-plants, although individual differences exist among fungal and plant capacities. Also, clear experimental evidence exists indicating that N taken up by the hyphae in the external medium is translocated throughout the hyphae towards the mycorrhizal root, leaves the fungal cells and is finally taken up by the root cell. The need for further investigation of the elucidation of the molecular mechanisms involved in the exchange of N-containing molecules at the level of root-fungus interface as well as how these mechanisms are regulated is stressed.
Domaines
Biologie végétale
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