Fig. 3. Phenotypic consequences of growth in four modified environmental conditions for Lemna minor, with and without its natural microbiome. A) Photo of a single genotype grown in four environmentalconditions without the microbiome. B) Variation in frond area (mm2) C) Variation in Root length (mm). Each box and whisker represent the variation among 8 independent populations (3 replicate flasks were averaged for each of the 8 genotypes). Boxes represent the upper and lower quartiles, whiskers represent max and min values, and outliers are shown as points.
Average colony size, i.e., the number of attached fronds, changed markedly with the abiotic environment (F3,128=162.49, p<0.001), with smaller colonies in high nutrient and light conditions and larger colonies when these resources are in shorter supply. We regressed colony size on growth rate and found that the slower growing the population, the greater the number of fronds that remain attached (F3,188=96.7, p<0.001, m= -36.7, R2=0.60) (Fig. 4). However, this also depended on the presence of the microbiome. In general, the presence of the microbiome decreased colony size. Although the slope of the relationship between colony size and growth rate was the same whether the microbiome was present or absent, the intercept was significantly different (p=0.001), such that for the same growth rate, plants with their intact microbiome exhibited smaller colony sizes (Fig. 4).