Allocation of plant carbon to foraging and storage in arbuscular mycorrhizal fungi

Foraging strategies, the cost-benefit associated with the search for new resources, have only begun to be explored in arbuscular mycorrhizal fungi (AMF). We show the use of C-13-labelling, via shoot photosynthesis, of the 16: 1omega5 fatty acid biomarker (the dominant and rather specific fatty acid in AMF storage lipids) to study the immediate patterns of carbon allocation to fungal lipids in response to inorganic and organic nutrient amendments. Signature fatty acid measurements, the incorporation of the label and complementary hyphal length density measurements showed that the extraradical mycelium of AMF proliferated in response to all the amendments provided whereas its development into unamended sand was minor in all treatments. We demonstrate the foraging capacity of AMF, linked to plant carbon, through their hyphal proliferation and accumulation of energy reserves. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.