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Nodulated N 2 ‐fixing Casuarina cunninghamiana is the sink for net N transfer from non‐N 2 ‐fixing Eucalyptus maculata via an ectomycorrhizal fungus Pisolithus sp. using 15 NH 4 + or 15 NO 3 − supplied as ammonium nitrate
Author(s) -
He Xinhua,
Critchley Christa,
Ng Hock,
Bledsoe Caroline
Publication year - 2005
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 - 10.1111/j.1469-8137.2005.01437.x
Subject(s) - casuarina , biology , nitrogen fixation , botany , eucalyptus , mycorrhiza , frankia , ammonium , symbiosis , root nodule , chemistry , bacteria , genetics , organic chemistry
Summary• To determine the effects of nitrogen source on rates of net N transfer between plants connected by a common mycorrhizal network, we measured transfer of N supplied as 15 NH 4 14 NO 3 or 14 NH 4 15 NO 3 in three Casuarina/Eucalyptus treatments interconnected by a Pisolithus sp. The treatments were nonnodulated nonmycorrhizal/nonmycorrhizal; nonnodulated mycorrhizal/mycorrhizal; and nodulated mycorrhizal/mycorrhizal. • Mycorrhization was 67% in Eucalyptus and 36% in Casuarina . N 2 fixation supplied 38% of the N in Casuarina . Biomass, N and 15 N contents were lowest in nonmycorrhizal plants and greatest in plants in the nodulated/mycorrhizal treatment. • Nitrogen transfer was enhanced by mycorrhization and by nodulation, and was greater when N was supplied as 15 NH 4 + than 15 NO 3 − . Nitrogen transfer rates were lowest in the nonmycorrhizal treatment for either 15 N source, and greatest in the nodulated, mycorrhizal treatment. Transfer was greater to Casuarina than to Eucalyptus and where ammonium rather than nitrate was the N source. • Irrespective of 15 N source and of whether Casuarina or Eucalyptus was the N sink, net N transfer was low and was similar in both nonnodulated treatments. However, when Casuarina was the N sink in the nodulated, mycorrhizal treatment, net N transfer was much greater with 15 NH 4 + than with 15 NO 3 − . High N demand by Casuarina resulted in greater net N transfer from the less N‐demanding Eucalyptus . Net transfer of N from a non‐N 2 ‐fixing to an N 2 ‐fixing plant may reflect the very high N demand of N 2 ‐fixing species.