Mycorrhiza

, Volume 18, Issue 8, pp 413–427

Response of plants to ectomycorrhizae in N-limited conditions: which factors determine its variation?

Authors

    • Centro de Ecologia e Biologia Vegetal—CEBVUniversidade de Lisboa, Faculdade de Ciências
  • R. J. Strasser
    • Laboratoire de BioénergétiqueUniversité de Genève
  • M. A. Martins-Loução
    • Centro de Ecologia e Biologia Vegetal—CEBVUniversidade de Lisboa, Faculdade de Ciências
Original Paper

DOI: 10.1007/s00572-008-0195-0

Cite this article as:
Corrêa, A., Strasser, R.J. & Martins-Loução, M.A. Mycorrhiza (2008) 18: 413. doi:10.1007/s00572-008-0195-0

Abstract

In the present work, the following hypotheses were tested: (1) the negative effects of mycorrhization over host plant productivity in N-limited conditions are due to N retention by the fungal partner and not due to excessive C drainage; (2) If mycorrhization results in decreased N uptake, the host plant decreases its C investment in fungal growth. The effects of mycorrhization over a wide range of combinations between N availability, N concentration in plant tissues, and degree of mycorrhizal colonization were studied in Pinus pinaster L. mycorrhizal with Pisolithus tinctorius. Several plant productivity parameters, the seedlings’ N status, chl a fluorescence (JIP test), and mycorrhizal colonization were measured. N was always limiting. A gradient of mycorrhizal effects over the host plant’s growth and vitality was successfully obtained. The mycorrhizal effects on plant growth and N uptake were very strongly and positively correlated, and no evidence was found of a C limitation to growth, confirming hypothesis 1. Indications were found that the plants continued to provide C to the fungus although the N supplied by it was increasingly lower, denying hypothesis 2. A new index, the mycorrhizal N demand–supply balance, was found to efficiently explain, and to have a curvilinear relation with, the variation in response to mycorrhization. The mycorrhizal effect on host plant growth was not related to a negative effect on its photosynthetic performance and, therefore, reflected changes in resource allocation between host plant and mycorrhizal fungus, not in plant vitality.

Keywords

Ammonium Chlorophyll a fluorescence Colonization density Cost–benefit Demand–supply Ectomycorrhizae Mycorrhizal response Nitrogen O-J-I-P test

Copyright information

© Springer-Verlag 2008