Abstract:With sand culture in greenhouse, this paper studied the effects of inoculation with arbuscular mycorrhizal (AM) fungi Glomus mosseae and G. versiforme on the utilization of insoluble phosphate AlPO4 (Al-P) by trifoliate orange (Poncirus trifoliata) seedlings. The results indicated that inoculation with AM fungi notably increased the dry matter, P content, and P absorption rate of P.trifoliata. The contribution of mycorrhiza, P uptake by plant and AM fungi, and the contribution of AM fungi in P uptake by P. trifoliata increased greatly with increasing Al-P level in the medium. Inoculation with AM fungi greatly increased the excretion of phosphatase, especially acid- and neutral phosphatase, from plant root and hyphae, but the excretion amount decreased with increasing Al-P level. The contribution of the fungi in P uptake by P. trifoliata was significantly positively correlated with the amounts of acid-, neutral-, alkaline-, and total phosphatase.