Effect of host shoot clipping on carbon and nitrogen sources for arbuscular mycorrhizal fungi

Abstract

The effect of clipping of the host-plant shoot on the sources of carbon and nitrogen for the arbuscular mycorrhizal (AM) fungus Gigaspora margarita was determined by measuring 13C in spores and hyphae in cocultures of C3 and C4 plants and by differential 15N labeling. C3 and C4 plants, which have different δ13C values, were grown in the same container separated by a series of hyphal compartments. The C3 and C4 plants were applied with 14N- and 15N-urea, respectively. After clipping of the C3 shoots, spore δ13C gradually approached that of the C4 roots. Hyphal δ13C paralleled that of spores. Spore % 15N was similar to that of mineral N in the C4 plant compartment. Thus C in G. margarita coming from the clipped plants decreased with time. This demonstrates that C in AM fungi comes from living plants, whilst the N in spores comes mostly from the soil.