Mechanism of Calcium and Phosphate Release from Hydroxy‐Apatite by Mycorrhizal Hyphae

Abstract

The role of vesicular‐arbuscular mycorrhiza (VAM) in facilitating the uptake of sparingly soluble nutrients from the soil has been well documented. Uncertainty remains regarding the mechanism controlling the dissolution of tightly bound P such as in phosphate rock. We studied the differential Ca and P uptake by the external mycelium of VAM in maize (Zea mays L.) grown in an acid tropical soil supplied with hydroxy‐apatite (HA). Three experiments were conducted in modified double‐pot systems where Ca was adequately provided through a nutrient solution and P in the form of apatite through a compartment only accessible to the hyphae. The results showed that in this system: (i) plant uptake of the apatite P occured only with VAM formation, (ii) the P release from the apatite was accompanied by a stochiometrically equivalent buildup of exchangeable Ca in the hyphal compartment, and (iii) the released apatite P was quantitatively recovered by the maize . It appears that the hyphae drove the apatite dissolution by mass action through the selective absorption of P, thereby overcoming the counter‐ion effect due to the Ca accumulation in the soil.

Substantial biologically mediated phosphorus depletion from the surface of a Middle Cambrian paleosol

“…Targeted attacks on minerals have been previously reported for mycorrhizal fungi (Ness and Vlek, 2000;Bonneville et al, 2009). Hallmarks of a mycorrhizal attack on apatite include removal of P from soil solution via uptake, with concomitant increase in Ca 2+ near the dissolving apatite crystal (Ness and Vlek, 2000).…”

“…Hallmarks of a mycorrhizal attack on apatite include removal of P from soil solution via uptake, with concomitant increase in Ca 2+ near the dissolving apatite crystal (Ness and Vlek, 2000). Argillans are a very prominent component of the soil fabric just above the last appearance of apatite.…”

Harnessing Plant Growth Promoting Rhizobacteria Beyond Nature: A Review

“…Biofertilizing PGPR sometimes enhances plant growth indirectly by stimulating the relationship between the host plant and beneficial rhizospheric fungi such as arbuscular mycorrhizae (AM). Although AM by themselves are well known to enhance the uptake of various soil nutrients (especially P) (Marschener, 1998;Ness and Vlek, 2000). Studies showed that their coinoculation with some PGPR could enhance the relationship between plant and fungal symbionts.…”

Influence of Microorganisms on Phosphorus Bioavailability in Soils

“…Most agricultural crops are potential host plants for arbuscular mycorrhizal (AM) fungi. In addition to an exudation of carboxylates, phosphatases and plant hormones, mycorrhiza increase the exploitation of the soil volume by the hyphal network, which increases the active adsorption surface and spreads beyond the phosphate depletion zone (Lange Ness and Vlek 2000;Martin et al 2001). Mycorrhizal hyphae have a higher affinity for phosphate as expressed in the Michaelis-Menten equation by a lower Km value and absorb P at lower solution concentrations than roots do (Lange Ness and Vlek 2000).…”

“…In addition to an exudation of carboxylates, phosphatases and plant hormones, mycorrhiza increase the exploitation of the soil volume by the hyphal network, which increases the active adsorption surface and spreads beyond the phosphate depletion zone (Lange Ness and Vlek 2000;Martin et al 2001). Mycorrhizal hyphae have a higher affinity for phosphate as expressed in the Michaelis-Menten equation by a lower Km value and absorb P at lower solution concentrations than roots do (Lange Ness and Vlek 2000). AM fungi store phosphate in the form of orthophosphate, polyphosphate and organic P in their vacuoles and transfer it to the roots of the host plant (Ezawa et al 2002).…”