Figure 4.

Lignin structure differently alters the resistance of specific TE morphotypes in annual plants. A, Traces of 25 representative perimeters for each TE type in transverse cross-sections from stems of Arabidopsis loss-of-function mutants altered in lignin structure. The outline color indicates the circularity of each respective TE. B, Schematic explanation of circularity and convexity of TEs. Any deviation from a perfect circle will decrease circularity, whereas only inward collapse of the perimeter will decrease convexity. C, Convexity and perimeter of PX, MX, and SX TEs in different phenylpropanoid biosynthesis mutants; n = 50 TEs per morphotype and genotype. Different lowercase letters indicate significant differences according to a Tukey-HSD test (per panel; $\alpha$ = 0.05). D–F, Structural equation models of the factors influencing TE convexity and circularity in the PX (D), MX (E), and SX (F) of Arabidopsis. Blue arrows and positive standardized coefficients indicate significant positive effects, red arrows and negative standardized coefficients indicate significant negative effects. Dashed arrows indicate predictors that were included and improved the model, but whose specific effects were not statistically significant. Grayed out variables had no significant effect on TE convexity.