Carbon investment into mobilization of mineral and organic phosphorus by arbuscular mycorrhiza

Abstract

To overcome phosphorus (P) deficiency, about 80% of plant species establish symbiosis with arbuscular mycorrhizal fungi (AMF), which in return constitute a major sink of photosynthates. Information on whether plant carbon (C) allocation towards AMF increases with declining availability of the P source is limited. We offered orthophosphate (OP), apatite (AP), or phytic acid (PA) as the only P source available to arbuscular mycorrhiza (AM) (Solanum lycopersicum x Rhizophagus irregularis) in a mesocosm experiment, where the fungi had exclusive access to each P source. After exposure, we determined P contents in the plant, related these to the overall C budget of the system, including the organic C (OC) contents, the respired CO2, the phospholipid fatty acid (PLFA) 16:1ω5c (extraradical mycelium), and the neutral fatty acid (NLFA) 16:1ω5c (energy storage) at the fungal compartment. Arbuscular mycorrhizal (AM) plants incorporated P derived from the three P sources through the mycorrhizal pathway, but did this with differing C-P trading costs. The mobilization of PA and AP by the AM plant entailed larger mycelium infrastructure and significantly larger respiratory losses of CO2, in comparison with the utilization of the readily soluble OP. Our study thus suggests that AM plants invest larger C amounts into their fungal partners at lower P availability. This larger C flux to the AM fungi might also lead to larger soil organic C contents, in the course of forming larger AM biomass under P-limiting conditions.

Mycorrhizal inoculation and phosphorus fertilization show contrasts on native species of the Brazilian Atlantic Forest and Cerrado

“…Since when P is available to plants, AMF can act as a photoassimilate drain, without resulting in gains in plant growth, because the maintenance of mycorrhizal colonization becomes a loss for the plant, once the fungi receive the photoassimilates and is not reciprocate in terms of plant growth (Johnson et al, 1997;Andrino et al, 2020).…”

Inter-annual precipitation fluctuation shapes plant communities regardless of fertilization addition and mycorrhizal suppression in desert steppe

“…Mycorrhizal root colonisation was assessed using the method described by Trouvelot (1986) (Trouvelot, 1986). The extra-radical biomass of AM fungi was measured by soil neutral lipid fatty acid (NLFA) analysis (Andrino, Guggenberger, Sauheitl, Burkart, & Boy, 2021;Cozzolino, Di Meo, Monda, Spaccini, & Piccolo, 2016;Stevens et al, 2020).…”

Common Mycorrhizae Network: A Review of the Theories and Mechanisms Behind Underground Interactions

“…Therefore, some experimental designs rely on air gaps to avoid diffusion over the soil solution flow while allowing the ingrowth of hyphae but not roots. This assures that all labeled compounds found in the receiver plant using in this system can be attributed to the mycorrhizal transport (Zhang et al, 2020;Andrino et al, 2021;Fang et al, 2021). However, these measures still do not exclude a transfer over indirect pathways, once transported resources by fungi mycelium can be released on neighboring plant compartment, leading the receiver plant to have access to resources without being connected (Figure 2).…”