Structural, histochemical and chemical characterization of normal, tension and opposite wood of Subabul (Leucaena leucocephala (lam.) De wit.)

Structure, histochemistry and chemical composition of tension (TW), opposite (OW) and normal wood (NW) of Leucaena leucocephala have been studied using histological, histochemical and biochemical methods. TW vessels are longer and have a larger diameter than NW vessels, and the rays are shorter and thinner. The G-layer replaced S3 and parts of S2 wall layers in TW fibres. TW further contained less lignin that also had a lower syringyl-to-guaiacyl ratio. The lignin was also more condensed. The content of α-cellulose was high in TW. TW contains hemicelluloses and pectins composed of more galactose, and less xylose, mannose, 4-O-methylglucuronic acid and galacturonic acid compared to that of OW. This study suggests that in the TW of Leucaena, the amount and composition of lignin, hemicelluloses and pectins differ considerably from that in OW and NW.