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Kinetics of NO 3 ‐ net fluxes in Pinus pinaster , Rhizopogon roseolus and their ectomycorrhizal association, as affected by the presence of NO 3 ‐ and NH 4 +
Author(s) -
GOBERT ANTHONY,
PLASSARD CLAUDE
Publication year - 2007
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2007.01705.x
Subject(s) - pinus pinaster , pinus <genus> , botany , ectomycorrhiza , forestry , biology , environmental science , mycorrhiza , geography , symbiosis , paleontology , bacteria
ABSTRACT The impact of mineral N supply, N‐free or NO 3 ‐ with or without NH 4 + , on the subsequent uptake of NO 3 ‐ by maritime pine seedlings associated with the ectomycorrhizal fungus Rhizopogon roseolus was studied using ion‐selective microelectrodes. NO 3 ‐ net fluxes into N‐starved non‐mycorrhizal short roots (NMSRs) were low and measurable only over the NO 3 ‐ concentration range of 0–70 µ M. The simple kinetics observed in those roots may reflect the dominant operation of a high‐affinity NO 3 ‐ transport system (HATS) which is constitutive. NO 3 ‐ pretreatment increased the NO 3 ‐ net fluxes and led to a complex kinetics that may reflect the operation of other HATS. A simple kinetics was observed in plants pre‐incubated at high NH 4 + concentration. In contrast, NO 3 ‐ uptake kinetics presented only one saturation phase in the fungus, whether associated with the plant or not. NO 3 ‐ uptake was greater after a pretreatment in N‐free or NO 3 ‐ solution, but NH 4 + pretreatment led to a threefold reduction in NO 3 ‐ uptake. These results suggest that the regulation of NO 3 ‐ transport systems varies between the host and the fungal partner. This variation is likely to contribute to the positive effect of mycorrhizal association on N uptake in plants when the N supply is low and fluctuating.