Avanços metodológicos na análise da distribuição de lignina na parede celular e caracterização anatômica de madeiras nativas da Amazônia

Abstract

Wood from native species of the Amazon Forest exhibits high structural and chemical complexity, whose understanding is still limited by the scarcity of available information. This dissertation aimed to evaluate methodologies for lignin analysis using fluorescence microscopy, as well as to characterize wood anatomy and analyze the distribution and fluorescence intensity of lignin in different cellular regions in wood from native Amazonian species, based on the application of the validated technique. In the first chapter, different chemical treatments and image processing methodologies were tested for the analysis of cellular lignin using fluorescence microscopy, aiming to validate the technique through the relationship between total lignin content in wood and the fluorescence intensity emitted in histological sections. Seven species were analyzed: melancieira (Alexa grandiflora Ducke), angelim saia (Parkia pendula (Willd.) Benth. ex Walp.), guaruba (Vochysia maxima Ducke), angelim pedra (Hymenolobium petraeum Ducke), freijó (Cordia sagotii I.M. Johnst.), pequiá (Caryocar villosum (Aubl.) Pers.), and angelim vermelho (Dinizia excelsa Ducke). Total lignin content in wood was obtained using the Klason method, and four treatments were used for fluorescence intensity analysis: in natura autofluorescence, autofluorescence without extractives, basic fuchsin, and Mäule. Images were processed using the ImageJ software, in which three image processing methodologies were tested. The results indicated that autofluorescence in sections without extractives, analyzed using an automated background subtraction method, showed the best performance and high correlation with total lignin content, ensuring speed, reproducibility, and standardization of the results. In the second chapter, wood anatomical characterization and the analysis of lignin distribution and fluorescence intensity in different cellular regions were performed. The anatomical analysis revealed high interspecific variability in the dimensions, frequency, and organization of vessels, fibers, rays, and intervessel pits. Lignin analysis showed a predominance of guaiacyl units in vessel walls and in the middle lamella, whereas fibers exhibited interspecific variations in lignin composition. Fluorescence intensity was higher in the middle lamella, followed by vessel and fiber walls. Overall, the results demonstrate that each Amazonian species combines vessels, pits, fibers, rays, and lignin in a functionally integrated manner, expressing distinct anatomical strategies that support hydraulic performance and the mechanical resistance of wood