Figure 1.

Seasonal variation in cambial activity and wood formation on the anatomical and RNA-Seq levels during one year in Hissjö, Sweden. A, Light microscopy sections from four different sampling dates representing different stages of cambial activity. Viability of the cells was assessed by nitroblue tetrazolium (NBT) staining. Images were taken (from left to right) on May 11, 2012; June 13, 2011; July 11, 2011; and September 6, 2011. c, Cambium; ew, earlywood; lw, latewood; p, phloem; plw, latewood of the previous growing season. Bars = 100 µm (first, third, and fourth images) and 200 µm (second image). B, Scheme of sample collection. Green rectangle, Summer months June, July, and August; brown rectangle, autumn months September, October, and November; blue rectangle, winter months December, January, and February; and yellow rectangle, spring months March, April, and May. C, PCA plot of the sequencing reads showing tissue type separation, the clustering of biological replicates, and the effect of time in a three-dimensional space. Different sampling points are represented by letters from A to W. Cambium/phloem and xylem samples are marked with green and magenta, respectively. A semantic summary (less than log₁₀ P < −1.3) of GO term enrichment for the genes with highest loadings is given next to each component (Comp.).