Figure 2

(a) Micrograph of toluidine blue stained cross section of the wildtype sorghum coleoptile. (b) Visible image from Raman microscopy of lower right-hand area of section showing epidermis and cortical cells with the investigated area of 137 × 119 μm as marked on panel a. (c) The KMC results, with the average Raman spectra for the main classes, including highest (green), medium (blue) and lowest (grey green) dhurrin content and the highest content of carotenoids (red). Raman intensities were normalized for C-H stretching region (2800–3015 cm⁻¹) in order to compare the dhurrin content in different classes. (d) Assignment of bands; (e–j). Integration Raman maps obtained with a sampling density of 1 µm were made for the following. (e) C-H stretching band in the region of approx. 2800‒3050 cm⁻¹ showing organic constituents present. (f,g) The bands at around 1164 cm⁻¹ and 1530 cm⁻¹, assigned to C-C and C=C vibrations of carotenoids, respectively. (h–j) The strongest bands of the dhurrin observed at 867, 1613 and 2249 cm⁻¹, respectively. The yellow colour corresponds to the highest relative intensity of the integrated band. All material was prepared using cryosections.