Abstract:Anatomical differences between normal wo od and compression wood of masson pine (Pinus massoniana) were studied by means of light and scanning electron microscope. The results show that the normal wood is narrower han the compression wood in growth ring width. The transition from earlywood to latewood is abrupt in normal wood in contrast to the gradual transition in compression wood. In transverse section, normal wood tracheids appear more or less square and rectangular, whereas compression wood tracheids are round in shape with the exception of those at the vicinity of growth ring boundary. In consequence, intercellular spaces are prominent at the junction of tracheids in compression wood. Furthermore, the secondary walls of compression wood tracheids consist of only two layers, S1 and S2, in comparison with the three layers in normal wood. Helical cavities or checks present only in compression wood, spiraling around the tracheid in the same direction as the cellulose microfibrils. Finally, the factors responsible for the formation of compression wood are discussed as well.