Uranium uptake and translocation by the arbuscular mycorrhizal fungus, Glomus intraradices, under root-organ culture conditions

Uranium (U) uptake and translocation by the arbuscular mycorrhizal (AM) fungus Glomus intraradices were studied under root-organ culture conditions with Agrobacterium rhizogenes-transformed carrot (Daucus carota) roots as host. Two-compartment Petri plates were used to spatially separate a root compartment (RC) and a hyphal compartment (HC); root growth was restricted to the RC while extraradical hyphae grew in both RC and HC. The HC was labelled with 0.1 μM²³³U at different pH conditions. At the end of the experiment, U was measured in the RC and in the HC. The U absorption by the AM fungus was observed. It included; U uptake by the mycelium developing in the HC, and U translocation from the HC to the RC. The magnitude of this uptake and translocation was highly influenced by the pH of the growth medium, while translocation was highly correlated with the number of hyphae crossing the partition separating the two compartments. These results are the first to show that an AM fungus can take up and translocate U towards roots.