Figure 4.

Norway spruce monolignol genes showed expression peaks both in the summer and in the winter. A, Hierarchical clustering of all putative monolignol, laccase (LAC), and peroxidase (PRX) genes identified based on the phylogenetic analyses and expression in xylem samples. The candidate genes for lignin biosynthesis and polymerization were identified from clusters 1 and 2, respectively. B, Names of the genes in clusters 1 and 2. C and D, Expression profiles of the genes in clusters 1 and 2. E, Daily mean temperatures of sampling dates in Umeå. F, Proportions of lignin ± se in the part of the year ring that contained living tracheids. The periods of earlywood (ew) and latewood (lw) formation are indicated. Dashed lines show the date for the coldest sampling time point during the study period.