Effects of heavy metals on nitrogen uptake by Paxillus involutus and mycorrhizal birch seedlings |
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Authors: | Blaudez Botton Chalot |
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Institution: | University Henri PoincaréNancy I, Faculty of Sciences, Laboratory of Forest Biology, UA INRA 977, P.O. Box 239, 54506 Vand?uvre Cedex, France |
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Abstract: | The effects of the heavy metals Cu, Cd, Ni, Pb and Zn on (14)C]methylamine and (14)C]aminoisobutyric acid uptake were studied in the free-living fungus Paxillus involutus and in mycorrhizal and non-mycorrhizal birch roots. The uptake of both N sources by P. involutus was inhibited by the five metals tested. However, Cu(2+) and Pb(2+) had a greater inhibitory effect. Non-competitive inhibitions were determined between heavy metals and (14)C]methylamine uptake. (14)C]Methylamine uptake was reduced by one third by 2 μM Cd(2+) and Cu(2+) in non-mycorrhizal roots, whereas that of mycorrhizal roots was not affected. However, it was reduced by 30 to 80% by 200 μM Cd(2+) and Cu(2+) irrespective of the mycorrhizal status. (14)C]Aminoisobutyric acid uptake in mycorrhizal roots was not significantly affected by Cd(2+) and Cu(2+), whereas that of non-mycorrhizal roots was decreased by 77% at 200 μM Cu(2+). (14)C]Aminoisobutyric acid uptake was 4.5 to 6 fold higher in mycorrhizal roots, compared with non-mycorrhizal roots, even under metal exposure. The high efficiency of N acquisition by mycorrhizal birch seedlings under metal exposure might be regarded as a mechanism of stress avoidance. |
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Keywords: | [14C]Aminoisobutyric acid [14C]Methylamine Ectomycorrhizal birch Heavy metal Nitrogen uptake Paxillus involutus |
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