Quantitative real-time PCR of P . abies WOX gene expression in different tissues (±SEM) . A. Relative expression of PaWOX2, PaWOX8/9, PaWOX8A and PaWOX8B. B. Relative expression of PaWOX3, PaWOX4, PaWOX5 and PaWOX13. The Y-axis is presented as natural logarithm. Absence of staples indicates no expression detected. PEM, proembryogenic masses; EE, early embryos; LE, late embryos; ME, mature embryos; ST, shoot tips; YN, young needles; ON, old needles; RT, root tips; CM, cambium.