B. Frey et H. Schuepp, A ROLE OF VESICULAR-ARBUSCULAR (VA) MYCORRHIZAL FUNGI IN FACILITATINGINTERPLANT NITROGEN TRANSFER, Soil biology & biochemistry, 25(6), 1993, pp. 651-658
Two greenhouse experiments were carried out to study the transfer of n
itrogen from berseem (Trifolium alexandrinum) to associated non-legume
s via the hyphae of VA mycorrhizal fungi using N-15 as tracer. A speci
al cuvette-membrane system was used to study the effects of restricted
and unrestricted hyphal growth between the legume and the non-legume
on nitrogen transfer. The roots of berseem plants, either inoculated w
ith the VA mycorrhizal fungus Glomus intraradices or non-inoculated, w
ere separated by a 3 cm root-free zone from the roots of the non-legum
e. In the first experiment, a split-root technique was employed to lab
el the legume with N-15. Maize was chosen as the non-legume. 50-day ol
d berseem plants were supplied with a N-15-enriched N source, which wa
s added to the outer side of the divided root system of the legume. In
the second experiment apple was the non-legume chosen, The legume was
labelled with N-15 by injection into the leaf petioles after a 51-day
growth of berseem. Both methods of N-15-labelling of the legume were
effective in enriching all plant parts with N-15. Transfer of N-15 fro
m berseem to the non-legume infected by the VA mycorrhizal fungus was
significantly higher than in the non-infected non-legume over a 28-day
period. However, the patterns of N-15 transfer differed between the t
wo experiments. By correcting the value of N-15 in mycorrhizal receive
r plants for the background values in the corresponding non-mycorrhiza
l treatments, 4.7% of the N-15 content of berseem was transferred to a
pple. In contrast, the amounts of N-15 transferred to mycorrhizal maiz
e were smaller with 0.1% of the N-15 derived from berseem.