-Tension (TW) and opposite wood (OW) of Eucalyptus globulus trees were analyzed for its chemical characteristics and Kraft pulp production. Lignin content was 16% lower and contained 32% more syringyl units in TW than in OW. The increase in syringyl units favoured the formation of β-O-4 bonds that was also higher in TW than in OW (84% vs. 64%, respectively). The effect of these wood features was evaluated in the production of Kraft pulps from both types of wood. At kappa number 16, Kraft pulps obtained from TW demanded less active alkali in delignification and presented slightly higher or similar pulp yield than pulps made with OW. Fiber length, coarseness and intrinsic viscosity were also higher in tension than in opposite pulps. When pulps where refined to 30°SR, TW pulps needed 18% more revolutions in the PFI mill to achieve the same beating degree than OW pulps. Strength properties (tensile, tear and burst indexes) were slightly higher or similar in tension as compared with opposite wood pulps. After an OD 0 (EO)D 1 bleaching sequence, both pulps achieved up to 89% ISO brightness. Bleached pulps from TW presented higher viscosity and low amount of hexenuronic acids than pulps from OW. Results showed that TW presented high xylans and low lignin content that caused a decrease in alkali consumption, increase pulp strength properties and similar bleaching performance as compared with pulps from OW.Keywords: Eucalyptus globulus, Reaction wood, Kraft pulping, Xylans and Lignin structure. CARACTERÍSTICAS QUÍMICAS E POLPAÇÃO KRAFT DE MADEIRA DE TRAÇÃO DE Eucalyptus globulus LABILL

In this work, six different genotypes of Eucalyptus globulus were selected on the basis of their differences in wood density and pulp yield. The trees were separated into two groups of three genotypes each: group I (samples Eg1, Eg2, and Eg3) presented wood density values of 547-573 kg/m 3 and pulp yields of 52.7-54.6%; group II (samples Eg4, Eg5, and Eg6) presented wood density of 471-485 kg/m 3 and pulp yields of 49.8-52.3%. Chemical characterization showed that genotypes of group I also presented high glucose and low lignin content as compared with genotypes from group II. Xylans content was lower in samples of group I than group II. Kraft pulps from group I presented high retention of xylans in comparison with pulps from group II. This behavior was associated with a high degree of substitution (DS) of the xylose units with methylglucuronic acids in wood and in kraft pulps in samples of group I compared with group II. Xylans isolated from wood samples of group I also presented slightly higher molar mass than xylans from group II. Results showed that xylans from a single species presented differences in their retention and structure that affected the pulp yield of E. globulus.