Fig. 3

Wide-field fluorescence microscopy showed vacuole autofluorescence from ray parenchyma in sapwood (top row) and heartwood (bottom row) from an 11-year-old E. bosistoana tree. Images confirmed that wood samples were strongly autofluorescent at all visible wavelengths. Images were collected and processed with the same settings to demonstrate that heartwood cells were more fluorescent than sapwood using transmitted light (a, e), UV excitation (b, f), blue excitation (c, g), and green excitation (d, g). Scale bar 30 μm. Normalised fluorescence emission spectra (lambda scans) from vacuoles in radial parenchyma cells in sapwood using i 405 nm, j 488 nm and k 561 nm excitation. As excitation wavelength increased, emission peaks were shifted to longer wavelengths.