Growth benefits provided by different arbuscular mycorrhizal fungi to Plantago lanceolata depend on the form of available phosphorus

Abstract

Strains of arbuscular mycorrhizal fungi (AMF) differ markedly in the growth benefits they provide to plants. We investigated whether these differences depend on the chemical form of inorganic phosphorus. The closely related AMF Glomus custos and Rhizophagus irregularis were compared using Plantago lanceolata as the host plant, grown in quartz sand with either soluble orthophosphate or sparingly soluble hydroxyapatite as a sole source of phosphorus. In a growth experiment with AMF-inoculated plants in a climate chamber, sampling at 3-wk intervals enabled a detailed time-resolved analysis of shoot and root phosphorus concentrations and growth performance of P. lanceolata. The ability of AMF to enhance plant growth and deliver phosphate depended strongly on the identity of the available phosphorus source. In orthophosphate-amended substrate only modest differences in plant growth performance (dry matter accumulation and allocation, phosphorus acquisition) were observed between the two AMFs, despite evident AMF root colonization as shown by strain-specific mtLSU qPCR analysis. The treatment with hydroxyapatite however, created stringent growth-limiting conditions and significantly increased the growth benefit provided by R. irregularis over G. custos and the non-mycorrhizal treatment. Plants with R. irregularis could acquire much more phosphorus from apatite compared to G. custos. There were also differences in shoot-to-root dry matter allocation and plant tissue phosphorus concentrations between the R. irregularis and G. custos treatments. Our observations suggest that in experiments on the symbiosis between plants and mycorrhizal fungi more attention should be paid to the chemical form of phosphorus in soil. 2−), may contribute significantly to the total phosphorus content of a soil, up to 75-90%, especially in the

Mycorrhizal fungi control phosphorus value in trade symbiosis with host roots when exposed to abrupt ‘crashes’ and ‘booms’ of resource availability

“…First, we utilised apatite, a form of rock P that is difficult for plant roots to obtain directly, but that arbuscular mycorrhizal fungi can help break down (Reynolds et al ., 2006; Pel et al ., 2018). Our aim was to use a form of phosphorus that was difficult for the host to take up directly (Reynolds et al ., 2006; Pel et al ., 2018), essentially increasing the ‘bargaining’ position of the fungi (Noë & Kiers, 2018). Past work on split‐root systems has shown that root systems colonised with arbuscular mycorrhizal fungi are better able to take up of apatite compared with noncolonised roots (Whiteside et al ., 2019).…”

“…Apatite is difficult for plant roots to dissolve directly, however arbuscular mycorrhizal fungi can help break down apatite (Reynolds et al ., 2006; Pel et al ., 2018). Past work has shown that arbuscular mycorrhizal fungi can increase the dissolution and uptake of apatite, even under sterile conditions when no other microbes are present (Reynolds et al ., 2006; Pel et al ., 2018; van’t Padje et al ., 2020). We constructed three colours of QD‐apatite (cyan (490 nm), yellow (576 nm) and red (666 nm)) that were equal in size and mass.…”

Mycorrhizal Fungi Respond to Resource Inequality by Moving Phosphorus from Rich to Poor Patches across Networks

“…We tagged hydroxyapatite, a form of rock phosphate [ 44 , 45 ], with fluorescent nanoparticles. Specifically, we used two spectrally different carboxyl terminated quantum-dots (QDs) with 488 nm cyan and 666 nm red emission (Crystalplex, Pittsburg PA, USA).…”

Temporal tracking of quantum-dot apatite across in vitro mycorrhizal networks shows how host demand can influence fungal nutrient transfer strategies

“…Past work has shown that arbuscular mycorrhizal fungi can increase the dissolution and uptake of apatite [63,64]. While the apatite uptake mechanism for arbuscular mycorrhizal fungi is still unknown, fungi generally use endocytic pathways to take up large particles [65][66][67].…”