“…In contrast, P. alpina was not colonized by R. irregularis either on the vegetated roof or in the lab (data not shown), suggesting that P. alpina might not be a suitable host for R. irregularis , although it has been reported as a known mycorrhizal plant ( Cripps and Eddington, 2005 ). P. alpina is a stress-resistant plant species that may not need mycorrhizal colonization for growth promotion ( Mao and Huff, 2012 ; Steiner et al., 2012 ; Pecetti et al., 2015 ). By not forming mycorrhizal symbiosis, P. alpina could save 4–20% of photosynthates, which is normally transferred to the symbiont ( Wright et al., 1998 ).…”