THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE IV. THE EFFECT OF MYCORRHIZAL INFECTION ON UPTAKE OF 15N FROM LABELLED SOIL BY VACCINIUM MACROCARPON AIT.

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Abstract
SUMMARY: Moorland soil was labelled with 15N by long incubation with glucose and [15N] ammonium sulphate. Excess ammonium was then removed by acid‐washing and the soil sterilized by gamma‐irradiation. The distribution of label between four N fractions of the soil was determined.Shoots of mycorrhizal plants of the cultivated cranberry, Vaccinium macrocarpon Ait., grown on this soil for 6 months, were heavier, contained more nitrogen and a greater concentration of N on a dry‐weight basis than those of non‐mycorrhizal plants. Species of Trichoderma and Aspergillus, isolated from moorland soil, did not similarly stimulate growth of sterile plants.The 15N‐excess (atom per cent) of shoots from mycorrhizal Vaccinium plants was lower than that of shoots of uninfected plants. The endophyte neither affected growth nor 15N enrichment of Festuca ovina L. nor caused net mineralization in infected soil. The hypothesis that mycorrhizal roots can absorb nitrogen compounds unavailable to non‐mycorrhizal plants is discussed.