Phosphorus Inflow into Two Species of Clover Root with Different Morphology Colonized by AM Fungi

The effects of arbuscular mycorrhizal (AM) fungi on growth and phosphorus (P) inflow into two species of clover plant with different root morphology were studied. The experiment was arranged as a randomized complete block design consisting of a 2×3×3 factorial combination of two clover species (Trifolium alexandrinum L. and Trifolium pratense L.), three mycorrhiza states (without mycorrhiza, Glomus intraradices and Glomus mosseae) and three harvests (20, 40 and 60 days after transplanting) with 4 replications. In this experiment, plant dry matter, root colonization and P uptake in terms of P inflow and mycorrhizal P response (MPR) were determined.  Results showed that mycorrhizal growth response (MGR) of T. alexandrinum was greater than that of T. pratense. This was mainly attributed to the higher root length of T. alexandrinum which provides a greater surface area for colonization compared to T. pratense. The highest P inflow was observed during the first harvest period (0-20 d). In this harvest period and during the treatment with T. alexandrinum, P inflow into non-colonized roots, roots colonized by G. mosseae and G. intraradices were 1.9, 6.8 and 8.01 pM m-1 s-1, respectively being 3.6 and 4.2 times greater than the control plants. The greater effect of G. intraradices compared to G. mosseae on increasing P inflow might be due to the superior ability of G. intraradices to spread into the soil and absorb more P beyond the P depletion zones around the roots and/or might be due to the higher intensity of arbuscules and intra-radical hyphae per unit length of colonized root. In conclusion, T. alexandrinum was more responsive to mycorrhizal colonization than T. pratense which, in turn, resulted in better P nutrition of T. alexandrinum colonized by G. intraradices.