Hj. Hawkins et E. George, Effect of plant nitrogen status on the contribution of arbuscular mycorrhizal hyphae to plant nitrogen uptake, PHYSL PLANT, 105(4), 1999, pp. 694-700
The contribution of hyphae of Glomus mosseae (Nicol. and Gerd,) Gerd. and T
rappe (BEG 107) to the acquisition of mineral nitrogen by Triticum aestivum
L. cv, Hano (wheat) was tested under conditions of low P and high N (+ N -
P) or low N (-N-P), Mycorrhizal colonisation increased the shoot dry weigh
t and plant tissue concentrations of P and cations, However, N tissue conce
ntrations of mycorrhizal plants were not increased, although nitrate reduct
ase activities were significantly higher (in vivo activity) in + N-P mycorr
hizal compared to non-mycorrhizal roots. Ser ere plant N deficiency reduced
the percentage root length colonised (but not the percentage viable coloni
sation), hyphal length, total N-15 uptake bg hyphae and dry weight of mycor
rhizal plants. Although mycorrhizal colonisation did not affect the overall
plant N status, hyphae transported 1% (-N-P) and 7% (+N-P) of the N-15-lab
elled NH4NO3 to mycorrhizal plants ol er 48 h, The higher rate of hyphal N
uptake was apparently related to the more extensive hyphal growth at the hi
gher level of plant N supply. However, the hyphal N supply was not sufficie
ntly high to sustain adequate N nutrition of the plants supplied with very
low amounts of N to the roots. Conversely, a sufficient N supply to the roo
ts was important for the development of an extensive mycelium.