Figure 7.

Putative lignin biosynthesis route in Norway spruce developing xylem based on single-cell metabolomics. Red arrows indicate transport of monolignol glucosides through the membrane via, for example, secondary active transport based on a proton gradient. Purple arrows indicate transport of monolignol alcohols through the membrane via, for example, ABC transporters (Miao and Liu, 2010; Alejandro et al., 2012). Yellow arrows indicate transport of monolignol glucosides to a neighboring cell via plasmodesmata. Green arrows indicate liberation of monolignol glucosides into the apoplast after vacuolar collapse. Monolignol names in gray were not detected. Bar = 50 μm.