Figure legends
Fig. 1. Experimental design. (a) We grew two host plants ofMedicago truncatula in an elongated box divided into three
compartments by nylon mesh. The focal plant grew in the focal
compartment and was inoculated with Rhizophagus irregularisstrain A5 (A5). The partner plant grew in the partner compartment and
was inoculated with either A5, R. irregularis strain B12 (B12) orRhizophagus aggregatum (Agg). Only the central compartment was
supplied with phosphorus (P) in the form of apatite. (b) We grew two
host roots of in-vitro Daucus carota on a rectangular
plate. The focal host root grew in the focal compartment, and was
inoculated with A5. The partner plant grew in the partner compartment
and was inoculated with either A5, B12 or Agg. The fungal hyphae from
both root systems could cross over the plastic barrier into the central
compartment, but the plastic barrier prevented the diffusion of
nutrients. We imaged the central compartment in three locations (black
squares) to study fungal architecture. (c) Side view of anin-vitro plate in which the central compartment was covered with
a cellophane sheet to allow for 2D fungal imaging. (d) Side view of anin-vitro plate without cellophane sheet. The fungal hyphae could
cross over the plastic barrier into the medium of the central
compartment. We then added quantum-dot apatite to the partner
compartment to quantify the transfer of quantum-dot tagged apatite from
partner roots across the fungal network and into focal roots.
Fig. 2. Boxplot of intraradical colonization of focal roots and
ratio of intraradical colonization of focal plant to partner plant in
the whole plant greenhouse experiment. (a) Lower intraradical
colonization of focal roots when the fungal network was composed of
less-related, non-selfing fungal strains. (b) Focal and partner were
colonized equally when network was composed of one strain (A5-A5), there
was higher colonization of the focal root when there was a non-selfing
partner fungus. Black dotted line indicates a 1:1 ratio. Box-plots with
different letters indicate significant difference
(p < 0.05), top and bottom of the box indicate the first and
third quartile, and the whiskers indicate the minimum and maximum
values. n A5 = 8, n B12=9,n Agg=9.
Fig. 3. Boxplots of extraradical fungal abundance and
extraradical to intraradical investment ratio in the root organ
cultures (a) Total extraradical fungal abundance (sum of all three
compartments) is significantly influenced by the fungal strain in the
partner compartment, with higher fungal abundance when the network is
less related. (b) We found a bias towards intracellular growth when
networks were selfing (A5-A5), but more extracellular growth when
networks were not selfing. Box-plots with different letters indicate
significant difference (p < 0.05), top and bottom of the box
indicate the first and third quartile, and the whiskers indicate the
minimum and maximum values. n A5=12,n B12=11, n Agg=17.
Fig. 4. Physical architecture of extraradical network .
Extraradical mycelium in the fungus-only compartment is plotted from the
partner compartment barrier (left) (a), (d), (g) to the center (right)
(c), (f), (i), for the three partner fungal strains. (a)-(c) A5 grows a
denser and more complex network towards the center of the central
compartment, increasing the surface area and theDm . (d)-(f) B12 decreases in density and
complexity towards the center of the central compartment. (g)-(i) Agg
shows the highest density and complexity near the partner compartment
and the least towards the center of the central compartment.
Fig. 5. Boxplots of fungal network efficiency and dry root
weight of root organ cultures (a) Quantum-dot-apatite (QD) transfer to
the focal roots was less efficient when associated with a less-related
fungal network. n A5=12,n B12=8, n Agg=12. (b) We
found that the total root mass (focal + partner root) was lower when the
fungal network was less related. n A5=12,n B12=12, n Agg=17.
Box-plots with different letters indicate significant difference
(p < 0.05), top and bottom of the box indicate the first and
third quartile, and the whiskers indicate the minimum and maximum
values.