Ectomycorrhizal (EM) colonization, vitality index and root density of <i>P. × canescens</i>.

Root density was determined as root mass per liter of soil volume. Significant differences are indicated by different letters (ANOVA, followed by TukeyHSD, p≤0.05). Values indicate mean ± SE, (n = 7–9). CCR, COMT and CAD refer to transgenic poplar lines with suppressed activities of cinnamoyl coenzyme A reductase, caffeic acid O-methyl transferase, and cinnamyl alcohol dehydrogenase, respectively. *no significant differences were detected by TukeyHSD.