Regarding N and P assimilation improvement, our results are in agreement with common knowledge about the role of ECM in the assimilation and the recycling of the two elements (Read and PerezMoreno, 2003). Concerning the other major elements (Ca, Mg and K), our data indicate that K and Ca assimilations were improved in most of the ECM symbioses tested, while Mg was reduced. Recent
data about Ca, Mg and K assimilation in ECM roots suggest that the fungal sheath might act as an apoplastic barrier for the entry of these elements in the root cortex (Bücking et al., 2012). Our study suggests that in ultramafic soils, ECM helped the plant in finding deficient elements such as K and Ca and regulated the excess supply of Mg.