Contribution of arbuscular mycorrhizal fungi to utilization of organic sources of phosphorus by red clover in a calcareous soil

Abstract

A glasshouse pot experiment investigated the uptake by arbuscular mycorrhizal (AM) fungi associated with red clover of three organic sources of P added to a sterilized calcareous soil of low P availability. Each pot was separated into a central compartment for plant growth and two outer compartments for external mycelium using 30-m nylon mesh to restrict the roots but allow hyphal penetration. Plants in the central compartments were inoculated with the AM fungus Glomus versiforme and uninoculated controls were included. Plants were harvested on three occasions: 5, 7 and 10 weeks after sowing. Application of each of the three organic P sources (lecithin, RNA and sodium phytate) or inorganic P (KH 2 PO 4 ) at 50 mg P kg −1 to the outer compartments of mycorrhizal and uninoculated pots increased the yield, P concentration and total P uptake of red clover compared with pots to which no P was applied, with no differences among P sources in non-mycorrhizal plants but differences observed in mycorrhizal plants both 7 and 10 weeks after sowing suggesting differences in availability of the four P sources to AM mycelium. The contribution of external mycelium to plant uptake of applied P increased with time. The three organic P sources made smaller contributions to plant P nutrition than KH 2 PO 4 at the first and second harvests. At the third harvest, the contribution from KH 2 PO 4 was 23%, while those from lecithin, RNA and sodium phytate were 23, 17 and 31%, respectively. This suggests that with the mediation of AM fungi, soil organic P sources can make a contribution to host plant P nutrition comparable to that of soluble orthophosphate.

Chromium immobilization by extraradical mycelium of arbuscular mycorrhiza contributes to plant chromium tolerance

“…Thirdly, there may be different strategies for P absorption and translocation between non-mycorrhizal and mycorrhizal plants. AM symbiosis can mobilize P in the soil, or directly take up and transport P to plants (Feng et al, 2003;Karandashov and Bucher, 2005), while non-mycorrhizal root can only absorb mobile P in the soil (Schachtman et al, 1998). Moreover, P in the mycelium mainly exists in the form of polyphosphate (poly P) (Kuga et al, 2008) and its transfer across the symbiotic interface is regulated by mycorrhiza-specific phosphate transporters (Karandashov and Bucher, 2005), while in the non-mycorrhizal roots there is no such regulation.…”

Carbon and phosphorus exchange may enable cooperation between an arbuscular mycorrhizal fungus and a phosphate‐solubilizing bacterium

“…Second, microscopic and molecular analysis showing bacterial colonization on the surface of AMF hyphae and spores demonstrates that an intimate relationship between AMF and microbes exists (Toljander et al, 2006;Scheublin et al, 2010;Agnolucci et al, 2015). These bacteria can also influence AMF fitness (Frey-Klett et al, 2007) and ecological function (Hodge et al, 2001;Feng et al, 2003;Cheng et al, 2012;Zhang et al, 2014b). Consequently, microbes are recognized as a third part of the AM symbiosis, not just soil-borne 'free riders' (Jansa et al, 2013).…”

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“…The P content in winter was generally higher than in spring except for Gleyic Regosol (in both surface and subsurface mineral horizons). ALLOUSH andCLARK (2001) andFENG et al (2003) described significant linkages of the phosphorus uptake to the soil biological acitivity. The application of the method modified on the seasonal P dynamics showed similarly that the uptake of phosphorus at the time of the accelerated ecophysiological processes in plants is so rapid that the measurable content of the element is lower than its amount at the time of low temperatures when the biological activity of the soil considerably diminishes.…”