S U M M A K ^•Oas exchnnj^e and c;irl">on ;illoc:ition piilterns were sttidied in two popiihitums of I'diiictiiii rolorotiiiii, :in .Mrica C-4 grass. The pUints were grown ni split-root pots, eontammg partially sterihzed soil, with one side either inoculated (I) or not inoculated (NI) with a \-esieuliir-iirbuscuhir (\'.A) ni\ corrliizal fungus, (iigaspora margarita. Net carbon exchange rates (CER) and stomatal conductances were measured with conventional gas exchange apparatus, and carbon assimilation, translocation, and allocation were measured using photosynthetically-fixed "CO,.Mycorrhizal infection on one half of the split-root system caused a 20",, increase in CI'"R. llie eflect on CHR was less in tillers on the opposite side of the plants from the infected balf of the roots. The rate at «hich photosynthates were stored in the leaves was 45",, higher. Sink activity (concentration of labelled photosynthates in stem phloem tis.sue) more tban doubled in 1 versus NI plants. CICR and stomatal conductances, along with most of the carbon allocation patterns, were nearly identical between the NI (control) bigb grazing and low grazing ecotypes. However, V.-\ m\corrhizal fungi catised a greater storage ot photosynthates in the low grazing ecot\|ic.