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Nitrogen assimilation in Lolium perenne colonized by the arbuscular mycorrhizal fungus Glomus fasciculatum
To investigate nitrogen assimilation in Lolium perenne L. colonized by the arbuscular mycorrhizal (AM) fungus Glomus fasciculatum (Thax. sensu Gerd.), nitrate uptake, key enzyme activities, and 15N incorporation into free amino acids were measured. After a 4-h labelling period with [15N]nitrate, 15N...
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Published in: | The New phytologist 1998-03, Vol.138 (3), p.411-417 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
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Summary: | To investigate nitrogen assimilation in Lolium perenne
L.
colonized by the arbuscular mycorrhizal (AM) fungus
Glomus fasciculatum (Thax. sensu Gerd.), nitrate uptake,
key enzyme activities, and 15N incorporation into free
amino acids were measured. After a 4-h labelling period with [15N]nitrate,
15N content was higher in roots and
shoots of AM-plants than in those of control plants. Glutamine synthetase
(GS)
and nitrate reductase (NR)
activities were increased in shoots of AM-plants, but not in roots. More
label was incorporated into amino acids
in shoots of AM plants. Glutamine, glutamate, alanine and γ-aminobutyric
acid were the major sinks for 15N in
roots and shoots of control and AM plants. Interactions between
mycorrhizal colonization, phosphate and nitrate
nutrition and NR activity were investigated in plants which received
different amounts of phosphate or nitrate.
In shoots of control plants, NR activity was not stimulated by high levels
of phosphate nutrition but was
stimulated by high levels of nitrate. At 4 mM nitrate in the
nutrient solution, NR activity was similar in control
and AM plants. We concluded that mycorrhizal effects on nitrate assimilation
are not mediated via improved
phosphate nutrition, but could be due to improved nitrogen uptake and translocation. |
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ISSN: | 0028-646X 1469-8137 |
DOI: | 10.1046/j.1469-8137.1998.00127.x |