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Nitrogen assimilation in Lolium perenne colonized by the arbuscular mycorrhizal fungus Glomus fasciculatum
Author(s) -
FAURE SANDRINE,
CLIQUET JEANBERNARD,
THEPHANY GAELLE,
BOUCAUD JEAN
Publication year - 1998
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.1998.00127.x
Subject(s) - lolium perenne , shoot , nitrate reductase , nitrogen assimilation , nitrate , biology , mycorrhiza , glutamine synthetase , glomus , glutamate synthase , botany , phosphate , nitrogen cycle , assimilation (phonology) , agronomy , glutamine , nitrogen , chemistry , poaceae , symbiosis , amino acid , biochemistry , spore , bacteria , philosophy , ecology , genetics , organic chemistry , linguistics
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 15 N incorporation into free amino acids were measured. After a 4‐h labelling period with [ 15 N]nitrate, 15 N 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 15 N 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 m M 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.