Phenotypic plasticity
Plant phenotype was modified by both the abiotic environment and the
presence of the microbiome. Root length responded strongly to the
abiotic environment (F3,21=80.09, p<0.001),
increasing in length by 2.1x in low nutrient conditions, although this
response was stronger in high light conditions (Fig. 3c). There was
considerable variation in root length among genotypes
(F7,128=12.06, p<0.001), which interacted with
environmental condition (F21,128=3.47,
p<0.001), indicating that the plastic response in phenotype to
environmental conditions differed among genotypes (GxE). Systematically
across all environmental conditions, roots were shorter when the
microbiome was present (F1,7=52.45, p<0.001),
(Fig. 3c).
Frond phenotype was also modified by the environmental condition. Fronds
grown in low light conditions were visibly darker green in colour than
those grown in high light (Fig. 3a). Frond area responded to
environmental condition (F3,21=21.20, p<0.001)
and was on average 1.1x times larger when grown in high nutrient
conditions compared to low nutrient conditions (Fig 3b). There was
considerable variation in frond area among genotypes
(F7,128=19.44, p<0.001) although these all
responded similarly to the environment, (no genotype x environment
interaction) (F21,128=1.27, p>0.05). The
presence of the microbiome resulted in systematically smaller fronds
(F1,128=50.05, p<0.001) across all
environmental treatments (Fig. 3b), and for all genotypes. The extent of
this varied among genotypes resulting in a marginally significant
microbiome x genotype interaction (F7,128=2.09,
p<0.049). Furthermore, the GxE was mediated by the microbiome
resulting in significant 3-way interactions
(F21,128=2.19, p=0.004).