qPCR results from Populus trichocarpa (cv. Muhle Larson) leaf (a,b) and root (c,d) material derived from two different short rotation forestry sites (Anderlingen vs. Wallstawe), grown under controlled adequate (+P; (a,c)) and deficient (−P; (b,d)) phosphorus nutrition using 3 reference genes (POPTR_EF1α, POPTR_RP and POPTR_18s) for normalization. Normalized gene expression (y-axis) is shown for six differentially methylated genes (x-axis): POPTR_0001s01660g as Pt01s01660, POPTR_0002s03260g as Pt02s03260, POPTR_0005s01450 as Pt05s01450, POPTR_0006s20500g as Pt06s20500, POPTR_0014s01810g as Pt14s01810 and POPTR_0014s18950g as Pt14s18950. Black triangles indicate which plant material had a higher methylation level. Data are presented as the mean ± SEM, p* ≤ 0.05, p** ≤ 0.01 and 95% confidence intervals and were obtained from 3 independent experiments.