ABSTRACT
• Ion dynamics are important for cell nutrition and growth in fungi and plants. Here, the focus is on the relationship between the hyphal H+ fluxes and the control of presymbiotic growth and host recognition by arbuscular mycorrhizal (AM) fungi.

• Fluxes of H+ around azygopores and along lateral hyphae of Gigaspora margarita during presymbiotic growth, and their regulation by phosphate (P) and sucrose (Suc), were analyzed with an H+-specific vibrating probe. Changes in hyphal H+ fluxes were followed after induction by root exudates (RE) or by the presence Trifolium repens roots.

• Differential sensitivity to P-type ATPase inhibitors (orthovanadate or erythrosin B) suggests an asymmetric distribution or activation of H+-pump isoforms along the hyphae of the AM fungi. Concentration of P and Suc affected the hyphal H+ fluxes and growth rate. However, further increases in H+ efflux and growth rate were observed when the fungus was growing close to clover roots or pretreated with RE.