Fig. 2: Side view of the experimental box in the Permeable treatment.

A top view of the box is provided in Supplementary Fig. 3. In a, the donor plant is on the left and the receiver plant is on the right. The chambers are separated by a permeable barrier with a 3 mm air gap (no media present inside the air gap), across which DSE hyphae are visible in the inset (b). Panel c is an annotated version of Panel b highlighting the hyphal structures connecting the donor and receiver chambers with overlay lines. See Fig. 1 for a conceptual diagram of these boxes. Scale bars represent 10 mm for a and 4 mm for b and c.