Fig. 6. Fungal navigation in complex structures.

Certain structures in the chips proved notoriously difficult for fungal hyphae to navigate past (a–c), and different growth strategies were applied by the fungi to increasing their foraging range past these obstacles (d–f). a Rounded turns confused the growth direction of hyphae (here P. cf. subviscidae) and led them to grow back towards their origin (red arrowhead). b Corner-trapped hyphae (here G. confluens). The tip was not able to navigate out of the corner, and the hyphae instead elongated behind the tip in a folding manner. c Sharp angles restricted hyphal advancement of many species (as seen in Fig. 3, here P. cf. subviscidae) and in some cases led hyphae to turn back towards their original growth direction. d Branching increased the likelihood that a newly formed tip found the passage for progression (red arrowhead). In that case, the apex switched to this tip (here P. cf. subviscidae). e Hyphae hitting solid chip parts could apply tip force. Some species (here L. gentianeus) were able to break through the bonding of the chip and continue to grow between the PDMS and the glass slide in its original direction (red arrowheads), instead of following the maze pattern. f G. confluens altered its growth morphology from thicker, flexible runner hyphae (young growth morphology, left red arrowhead) to thinner hyphae with frequent lateral short branches (old growth morphology, right red arrowhead). The white arrows indicate growth direction.