Fig. 1

Key features of the colonization of roots by PAC species. Key steps in the colonization of roots by PAC species (V. Queloz, unpublished). Figure 1a, b. Surface colonization and appressoria/hyphopodia formation of P. subalpina on Cistus incanus roots. Figure 1c. Cross-section of Pinus strobus root colonized by PAC stained using borax, methylene blue and toluidine blue and counterstained with basic fuchsine. The fungus completely colonizes the cortical tissue up to the endodermis. Accumulation of phenolic compounds in the vascular cylinder is evident by the presence of dark granular structures. Figure 1d. Example of intracellular colonization of P. subalpina in C. incanus cortex (arrow)