Differential NO dependent patterns of NO uptake in Pinus pinaster, Rhizopogon roseolus and their ectomycorrhizal association.

•  A different NO dependent pattern of NO uptake at low [NO ] (0-0.1 mM) is shown in Pinus pinaster and in the ectomycorrhizal fungus Rhizopogon roseolus. In ectomycorrhizal symbiosis, the fungal pattern is pre-eminent. •  Net NO uptake rates were deduced in plant and fungus from solution depletion measurements. Net NO fluxes were estimated at the surface of mycorrhizal and nonmycorrhizal short roots, using NO selective microelectrodes. •  In NO starved seedlings, maximum NO uptake rates were reached after 3 d of incubation in 0.05 mM NO . In R. roseolus mycelia, NO uptake rates did not change after withdrawing NO for up to 7 d, or after adding NO for 3 d. Net NO fluxes in nonmycorrhizal short roots were increased twofold by a 3-d exposure to NO whereas in ectomycorrhiza they were similar irrespective of the NO pretreatment, but always higher than the fluxes measured in nonmycorrhizal roots. •  Ectomycorrhiza have a greater capacity to use NO than nonmycorrhizal short roots, whatever the NO concentration in the solution. This may give mycorrhizal plants a greater ability to use fluctuating concentrations of NO in the soil solution.