Variation in microfibril angle in Eucalyptus clones

The microfibril angle of the S-2 layer in wood fibres is an ultramicroscopical feature that influences important properties affecting the utilisation of timber. However, this characteristic is as yet little studied, and this is especially true of the genus Eucalyptus. The microfibril angle of the S-2 layer of the secondary wall was measured in fibres taken from eightyearold trees of 11 Eucalyptus clones growing in four sites in Brazil. The overall mean microfibril angle measured was 8.8degrees. While the angle seemed to decrease slightly from pith to bark in a nonlinear fashion, this decrease was not statistically significant. The microfibril angle showed statistically significant differences between sites and between clones, although the broad sense heritability of the microfibril angel was low (h(2)=0.293). Various theories attempt to explain the microfibril orientation, but we conclude that environmental stresses play an important role in defining the angle in Eucalyptus wood.