Fig. 9

Results of the three chemical imaging methods. The first row shows the chemical images based on multivariate calibration model coupled with calibration transfer (a–c), and the color legend on the right side of the figure represents the concentration of lignocellulose; the second row shows the chemical images with single band (d–f) and the color legend represents the spectral intensity at well-defined characteristic band; and the third row shows the result of chemical dyeing method (g, h). The slice in g is dyed with methylene blue (AR, Sinopharm Chemical Reagent Corporation, China), and the slice in h is dyed with phloroglucinol (AR, Sinopharm Chemical Reagent Corporation, China). The first column shows the distribution of cellulose (a, d, g); the second column shows the distribution of lignin (b, e, h); and the third column shows the distribution of hemicellulose (c, f). For the pseudo-color maps in the first row, the numbers on the right side of the color bar indicate the percentages of lignocellulosic content; for the pseudo-color maps in the second row, the numbers on the right side of the color bar indicate the absorbance intensity