EFFECTS OF A MYCOPHAGOUS COLLEMBOLA ON THE SYMBIOSES BETWEEN TRIFOLIUM-SUBTERRANEUM AND 3 ARBUSCULAR MYCORRHIZAL FUNGI

We examined the effect of the mycophagous Collembola Folsomia candida Willem on the symbioses between Trifolium subterraneum L. and three ar buscular mycorrhizal (AM) fungi. Mycorrhizal and non-mycorrhizal plant s were grown in pots with a central mesh bag which constituted a root- free soil compartment (RFSC) where the soil was labelled with P-32. Th is allowed us to study hyphal P transport as affected by the presence of Collembola in the soil with roots. The hyphal P transport was monit ored by measuring the P-32 content in leaflets sampled from the latest fully developed trifoliate leaf after 3, 4, 5 and 6 wk. Measurements on each plant after 6 wk furthermore included total contents of P-32 a nd P-31, root length and length of hyphae inside the mesh bag. The pre sence of F. candida reduced the average hyphal P-32 transport from the RFSC by 12% and the average AM hyphal length in the RFSC was reduced by 30%. The root dry weights of mycorrhizal plants were also reduced b y the presence of Collembola. The reduction in total hyphal P-32 trans port was not revealed by the data from the time-course study using lea flet samples, which demonstrates the uncertainty of analyses of AM fun gal activity based solely on measurements of leaf materials. The resul ts from this work suggest that F. candida grazed on roots and/or hypha e of AM; however, shoot yields were unaffected by this grazing. In con clusion, Collembola seemed to have little effect on the functioning of AM fungi.