Plant and mycelial growthSummarized

Plant and mycelial growthSummarized plant growth data are presented in Fig. 2. Full dataare accessible in ESM Table 2. On ultramafic substrate, ectomy-corrhizal treatment with P. albus induced enhancement of plantgrowth when compared with controls (Fig. 2): in A. spirorbis thebiomass was significantly enhanced with an increase of shoot dryweight from +8.7% to +44.3% (except for plants inoculated with P. albus isolate MD09-001) and an increase of root dry weight from+10.8% to 62.3%; in E. globulus the plant shoot dry weight was sig-nificantly enhanced from +57.1% to +82.4% and the root dry weightfrom +47.4% to +56.1%, all when compared with controls. Ergo-sterol was also measured in roots as indicator of the quantity ofmycelium at the root level. In pure cultures of fungal isolates, theergosterol concentration varied from 1.1 ± 0.1 to 5.2 ± 1.2 _g mg−1of mycelium fresh weight as reported in Table 1. The conversion fac-tor of ergosterol into mycelium fresh weight was calculated usingthe mean and was 2.38 ± 0.7 _g of ergosterol mg−1of myceliumfresh weight. Full data for ergosterol content in plant roots andconversion into relative fresh mycelium biomass using the conver-sion factor are presented in ESM Table 3. Summarized values offresh mycelium biomass in the root system are presented in Fig. 3:in A. spirorbis the mycelial biomass attributable to ECM was from2.61 ± 0.06% to 6.71 ± 1.35% and in E. globulus the mycelial biomassattributable to ECM was from 1.22 ± 0.57% to 2.77 ± 0.76%.Plant mineral nutrition analysesThe major elements needed for plant nutrition (i.e. N, P, K, Caand Mg contents) were analyzed in shoots of ECM and controlplants exposed to the ultramafic substrate. Results are summa-rized in Fig. 4 while full data are reported in ESM Table 4a. Thepresence of ECM symbiosis significantly affected major elementcontents in shoot tissues when compared with controls. In shootsof A. spirorbis, significant enhancement of N content in tissues(from 33.7% to 46.5%) was observed; P assimilation was signifi-cantly enhanced from 20.3% to 57.5% (except for plants inoculatedwith isolates MD09-045 and MD09-063); K assimilation was sig-nificantly enhanced from 21.4% to 35.8%; Ca assimilation wassignificantly enhanced from 6.1% to 18.1% (except in shoots ofplants inoculated with the isolate MD09-63) and Mg was signif-icantly reduced by 16.6% on average (except in plants inoculatedwith MD09-078 and MD06-337). In shoots of E. globulus signifi-cant enhancement of N content in tissues (from 8.3% to 20.5%) wasobserved (except for plants inoculated with isolates MD09-045 andMD09-063); P assimilation was significantly enhanced from 14.2%to 45.1%; K assimilation was significantly enhanced from 27.8% to38.0%; Ca assimilation was significantly enhanced from 29.4% to48.0%; and Mg was significantly reduced by 13.5% on average. Sim-ilarly, the metals that were present at high concentrations in theultramafic