Wood is an extremely complex biological material, which can show macroscopic similarities that make it difficult to discriminate between species. Discrimination between similar wood species can be achieved by either anatomic or instrumental methods, such as near infrared spectroscopy (NIR). Although different spectroscopy methods are currently available, few studies have applied them to discriminate between wood species. In this study, we applied a partial least squares-discriminant analysis (PLS-DA) model to evaluate the viability of using direct fluorescence measurements for discriminating between Eucalyptus grandis, Eucalyptus urograndis, and Cedrela odorata. The results show that molecular fluorescence is an efficient technique for discriminating between these visually similar wood species. With respect to calibration and the validation samples, we observed no misclassifications or outliers.

RESUMO Amostras de madeiras de marupá (Simarouba amara) e andiroba (Carapa guianenis) foram submetidas ao ataque dos fungos Trametes versicolor (podridão branca) e Gloeophylum trabeum (podridão parda). A colorimetria foi empregada para determinar as cores das madeiras antes e após o ataque dos fungos. Para acompanhar a variação do teor dos compostos químicos foi utilizada a técnica de espectroscopia de refletância difusa no infravermelho médio. Ambas as espécies foram consideradas não resistentes ao fungo de podridão branca. Para o fungo de podridão parda, a andiroba foi considerada resistente e o marupá não resistente. Ambas as espécies de madeira se apresentaram mais escuras após o ataque do fungo Gloeophyllum trabeum. Já o ataque do fungo Trametes versicolor causou clareamento na madeira da andiroba e escureceu ligeiramente o marupá. Os resultados da análise dos espectros de infravermelho mostraram que em ambas as espécies de madeira houve redução na intensidade das bandas de celulose, hemiceluloses e lignina após o ataque do Trametes versicolor, e redução somente na intensidade da banda de celulose após o ataque do Gloeophyllum trabeum.

ABSTRACT Wood samples of marupá (Simarouba amara) and andiroba (Carapa guianenis) were submitted to Trametes versicolor (white rot) and Gloeophylum trabeum (brown rot) fungi attack. Colorimetry was used to determine the color of the wood before and after wood decaying fungi. To evaluate the changes in chemical compounds levels in the wood samples, the diffuse reflectance medium infrared spectroscopy was used. Both wood were nonresistant against white rot fungus, while with brown rot attack andiroba was resistant and marupá was not. After Gloeophyllum trabeum attack both woods changed to a darken color, and after Trametes versicolor attack andiroba changed to a lighter color and marupá darkened slightly, The analysis showed a reduction in the peak intensity of cellulose, hemicellulose and lignin, for both species, after Trametes versicolor attack and a reduction in the peak intensity of cellulose after Gloeophyllum trabeum attack.