Figure 7.

OPLS model correlating average number of cell wall layers to Raman microspectroscopic features in three tissues: interfascicular fibers (IF), fascicular fibers (FF), and hypocotyl secondary xylem fibers (HF). A, Scatterplot showing separation according to the number of cell wall layers (predictive component) and tissue type (orthogonal component). B, The corresponding loadings plot and representative wild-type (WT) spectra for the three tissues. The spectral bands with more than 50% correlation levels (red dashed lines) are marked by band numbers. Bands at 900, 1,040, 1,150, 1,330, 1,460, and 1,505 cm⁻¹ are proportionally more intensive when there are more cell wall layers, whereas bands at 1,270 cm⁻¹ and a shoulder at 1,565 to 1,570 cm⁻¹ are proportionally more intensive when there are fewer cell wall layers. The model details are as follows: 820 spectra, one + three (predictive + orthogonal) components; R2X(cum) = 0.928; R2Y(cum) = 0.383; Q2(cum) = 0.377. AU, Arbitrary units.