Colonisation by arbuscular mycorrhizal fungi changes the relationship between phosphorus uptake and membrane potential in leek (Allium porrum) seedlings

The effect of colonisation by arbuscular mycorrhizal (AM) fungi on the rela tionship between phosphorus (P) uptake and root membrane electric potential difference (p.d.) was investigated in leek (Allium porrum L.). Plants were grown, with or without the AM fungus Scutellospora calospora (Nicolson and Gerdemann) Walker and Sanders, in soil. P uptake and root p.d. were correl ated; plants with the highest P concentration in the shoot had the most neg ative p.d. This relationship was strong in non-mycorrhizal leeks (r(2) = 84 -98%), but weaker in mycorrhizal leeks (r(2) = 55-64%), consistent with the idea that in mycorrhizal roots the fungal hyphae are the principal site of P uptake.