Fig. 8

The spectra of regression coefficients of partial least squares discriminant analysis (PLS-DA) models for each group in second derivative spectra based on wood block and tablet samples. Each arrow indicate the following; encircled one 7000 cm⁻¹ assigned to the amorphous regions in cellulose, encircled two 5980 cm⁻¹ aromatic skeletal due to lignin, encircled three 5800 cm⁻¹ furanose or pyranose due to hemicellulose, encircled four 5464 cm⁻¹ semi- or crystalline region in cellulose, encircled five 5220 cm⁻¹ water, encircled six 4890–4620 cm⁻¹ cellulose, encircled seven 4404 cm⁻¹ cellulose and hemicellulose, encircled eight 4280 cm⁻¹ semi- or crystalline regions in cellulose