Hj. Hawkins et E. George, Reduced N-15-nitrogen transport through arbuscular mycorrhizal hyphae to Triticum aestivum L. supplied with ammonium vs. nitrate nutrition, ANN BOTANY, 87(3), 2001, pp. 303-311
This study compared the influence of NH4+ or NO3- nutrition on the contribu
tion of extraradical hyphae of the arbuscular mycorrhizal fungus Glomus mos
seae (Nicol. and Gerd.) Gerd. and Trappe (BEG 107) to NH4+ or NO3- uptake b
y Triticum aestivum L. 'Hano' (summer wheat) with sufficient or insufficien
t N supply in semi-hydroponic culture. Roots and root-distant hyphae were s
patially separated in compartmentalized pots. Although NH4+-fed plants supp
lied with sufficient N had higher N concentrations than their NO(3)(-)(-)fe
d counterparts, this did not favourably affect colonization rates, hyphal l
ength densities or N-15 amounts transported via hyphae to the plants. Ammon
ium supply did not result in higher P or reduced carbohydrate concentration
s in the plants, so these factors could not explain the reduced hyphal leng
ths. It was concluded that the effect of NH4+ supply on hyphal length may b
e related to the reduced root growth and/or a direct effect of NH4+ on hyph
al growth. Plant N deficiency reduced the percentage root length colonized,
hyphal length, total N-15 uptake by hyphae and dry weight of both NO3- - a
nd NH4+- fed mycorrhizal plants. This was more obvious for NO3--fed plants
because plant biomass and hyphal lengths of NH4+-fed plants were relatively
low in mycorrhizal plants irrespective of the IV concentration supplied. (
C) 2001 Annals of Botany Company.