VARIATIONS IN WOOD ANATOMY AND FIBER BIOMETRY OF EUCALYPTUS GLOBULUS GENOTYPES WITH DIFFERENT WOOD DENSITY

Six 15-year-old Eucalyptus globulus trees, ranging in wood density from 474 to 575 kg.m(-3), were sampled at breast height for anatomical study and fiber measurement. Vessel and fiber dimensions showed an increase from pith to bark, while vessel frequency decreased. Cell wall thickness, fiber length, runkel ratio and coarseness were significantly superior in the high-density genotypes (group A) in almost each section along the radius analyzed. Average cell wall thickness for samples of group A was 3.35 mu m, while in group B (the low-density genotypes) was 2.86 mu m. The average runkel ratio and coarseness in groups A and B were 0.73 and 7.6 mg/100 m, 0.56 and 6.7 mg/100 m, respectively. Lumen width was significantly different among the groups, being higher in group B, but no significant differences were found for vessel features. Pooled data showed significant correlations between wood density and cell wall thickness (r = 0.52), coarseness (r = 0.40) and runkel ratio (r = 0.41), while coarseness has a close relation with almost each variable evaluated, showing an effect of cambial age on anatomical variations. Also significant and positive correlations were found for coarseness vs density, wall thickness vs coarseness, fiber length vs density, density vs wall thickness, runkel ratio vs density and coarseness vs fiber length at different sections along the radius analyzed.