Figure 6.

Distinct lignin monomers nonredundantly control specific mechanical properties. A, Six-week-old Arabidopsis WT plant with basal, middle, and apical stem segments showing difference in TE developmental stages and marked with the colors representing them in subsequent panels. Wiesner stained cross-sections at the bottom of each segment with close-ups of interfascicular fibers and TEs are shown. B Arabidopsis stem segment undergoing three-point bending. Flexural behavior is presented in Supplemental Movie S1. C and D, Flexural stiffness (C) and sustained elastic deformation before irreversible breaking, i.e. flexibility, (D) of WT stem segments incubated in water, air, or sorbitol determined by three-point bending; n = 4–8 stem segments per developmental stage and condition. E, Total lignin, S/G, and terminal G_CHO/total G_CHOH (measured by Raman microspectroscopy) and total G_CHO (measured using the Wiesner test) in PX, MX, and SX TEs of the different genotypes, expressed relative to the WT TEs of the respective morphotype; n = 15–50 TEs per genotype. F and G, Flexural stiffness (F) and sustained elastic deformation before irreversible breaking (G) of stem segments from WT, S-depleted fah1, and G_CHO-over-accumulating cad4 cad5 mutant plants determined by three-point bending; n = 14–30 stem segments per developmental stage and genotype. Different lowercase letters in panels (C–G) indicate significant differences according to a Tukey-HSD test (per panel; $\alpha$ = 0.05). Note that the plants for experiments shown in panels (C, D and F, G) were from different growth instances and slightly different age, explaining the slight differences in absolute stiffness.