Environmental adaptation and cell differentiation processes are factors that influence the anatomical elements of wood. The objective of this study was to investigate the effect of water deficit on lignin composition in anatomical elements and on the characteristics of vessel-neighboring cells. Six-year-old dones of Eucalyptus urophylla and Eucalyptus grandis x Eucalyptus camaldulensis from wet and dry regions were used. All regions received a rainfall exclusion treatment. Cell wall width, cell wall thickness, and form factor of fibers close to and far from vessels were measured. In the same cells, lignin was measured in the middle lamella and vessels by a fluorescence technique. The vessel differentiation process affected cell wall thickness and lignin composition in neighboring cells. Lignin composition was increased in vessels compared to fibers or vasicentric tracheids. Middle lamella lignin was not affected by vessel differentiation or water deficit in either eucalyptus done. E. grandis x E. camaldulensis is originally from a dry climate region and, therefore, did not suffer alterations in lignin when subjected to water stress conditions; however, this clonexhibited a higher number of vasicentric tracheids. E. urophylla is originally from a humid climate region and, when subjected to water deficit, showed increased wood lignin composition, which seems to be a strategy for better use of water resources. Alterations in lignin composition of vessel, vasicentric tracheid, and fiber cell walls resulting from exposure to water deficit conditions vary according to eucalyptus species.
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