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SUMMARYShort-tt-rtn effects of benomyl on the arbuscular mycorrhizal fungus GInmus caledonium (Nico!. & Gerd.) Trappe and Gc-rdfman associated with Cucumis sativiis L. were studied by measuring cfFtcts on fungal P transport and on fungal alkaline phosphatase activity. Mycorrhizai plants were grown in three-compartment systems where nylon mesh was used to separate a root-free hypha! compartment (HC) and a root-Fhyphal compartment (RHC) from the main root compartment (RC). Non-mycorrhizal control plants were grown in similar growth units. After 6 wk benom\] was applied to the plants in three ways: as soil drenches to RHC or HC, or as a spray to the leaves. Benomyl was added in three concentrations. Equal amounts of ''^P and ''''P were added to the HC and to the RHC respectively, immediately after the application of benomyl. Plants were harvested 4-6 d later. Hyphal transport of ^^P from the HC was inhibited when benomy] was applied to the HC at 10 //g g"' soii, whereas the uptake of •' •' P from RHC (roots-Khyphae) was reduced onl\ at the highest dose of application to the RHC (100 //g g"^ soil). In contrast to the marked reduction of benomyl on fungal P transport, the activity of fungal alkaline phosphatase inside the roots was unaffected by benomyl.

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