Fig. 5

a–d Optical images, ~ 1520 cm⁻¹ Raman images of fractured maize leaves, and histograms of the ~ 1520 cm⁻¹ peak location generated from each pixel within the Raman images. The fracturing process splits the leaf into two halves lengthwise. For each panel, the top optical and Raman image corresponds to one side of the fractured leaf, and the bottom optical and Raman image corresponds to the other side of the fractured leaf. Two areas at the half-leaf-length position were analyzed for the FoMV-pds leaf: a variegated white area and b a green area. The scale bar is 25 µm. The histograms were fit to a Gaussian function (red solid line). c, d represent the area measured for the FoMV and non-inoculated fractured leaves, respectively. N is the number of pixels that were positive for carotenoids and N′ is the number of pixels that were null (colored gray and were not included in the histogram)