Fig. 5.

Probing molecule orientation in spruce cuticle by mapping with different laser polarization. a The same region of interest was mapped with laser polarization direction parallel (0°) and perpendicular (90°) with respect to the cuticle surface b Raman spectra are extracted selectively from the epicuticular wax layer and the underneath cuticular layer. In the top layer higher intensities are observed for C–H stretches of waxes (2900 cm⁻¹) at 0° laser polarization (blue spectrum), while C–C stretching of waxes and aromatic ring stretches are most intense with 90° (red spectrum). In the cuticular layer beneath no orientation dependence is observed as the spectra are identical. c Schematic representation of the orientation of waxes and coumaric acid in the cuticle. The aliphatic chains and aromatic rings are oriented perpendicular to the surface in the wax layer, while compounds in the cuticular layer are not oriented, comprising an amorphous structure