Symbiose mycorhizienne et nutrition minérale

Abstract

In French Guiana where soils are generally acidic and poor in inorganic nutrients, a characteristic feature of forests is the diversity of species. An ecological approach has shown that on the roots of the major forest species there is a prevalence of endomycorrhizae that have a particular intracellular structure (spiral hyphae). Their involvement in phosphorus uptake has been investigated experimentally in two Cesalpiniaceae. Dicorynia guianensis Amshoff seedlings are highly dependent on mycorrhizae with spiralled mycelium for their growth and phosphorus content. This type of mycelium accounts for more than 90% of fungal colonisation. On the other hand, apa (Eperua falcata Aublet) seedlings also form mycorrhizae but while the latter improve the phosphate status, they have no effect on the growth of this species. These results enhance our understanding of the role of endomycorrhizal symbioses in natural regeneration processes and open up new research horizons as to their possible involvement in maintaining forest diversity.