Fig. 3

a Merged optical and ~ 1520 cm⁻¹ Raman images of in situ whole maize leaves. From left to right the images correspond to FoMV-pds silenced, FoMV, and non-inoculated leaves. The color scale at right represents the Raman scattering intensity and is the same for all images. The scale bar is 25 µm and is the same for all images. Additional in situ whole leaf Raman images are shown in Additional file 1: Fig. S2, and optical images of an expanded area around where the Raman images were collected are shown in Additional file 1: Fig. S3. b Histograms of the ~ 1520 cm⁻¹ peak maximum were generated from each pixel in the Raman images shown in a and Additional file 1: Fig. S2. The histograms were fit to a Gaussian function (red solid line). N is the number of pixels that were positive for carotenoids and N′ is the number of pixels that were null (not included in the histogram)