Relative transcript abundance of three genes involved in lignan biosynthesis in cells undergoing xylogenesis. Relative transcript abundance for each gene was determined by qRT-PCR. (a) Relative transcript levels in compression (black bars) and opposite (grey bars) developing xylem from four adult trees (T1-08, T2-08, T3-08, T4-08) after two months of artificial bending of the stems. (b) Relative transcript levels after 0, 7 and 15 days of transferring Pinus pinaster callus cells to induction medium (without hormones, open circles) or control medium (with hormones, closed circles). Values are means ± SE of three independent replicates. PLR: Pinoresinol-lariciresinol reductase; PCBER: phenylcoumaran benzylic ether reductase; PPDBR: phenylpropenal double-bond reductase.