Effects of inoculation with arbuscular mycorrhizal fungi on AlPO₄ uptake by Poncirus trifoliata

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.