Comparison of Dimensions and Fibril Angles of Loblolly Pine Tracheids Formed in Wet or Dry Growing Seasons

Diameter and wall thickness of tracheids and the fibrillar angle in their S2 layers were investigated at five relative heights within two increment sheaths of one dominant loblolly pine (Pinus taeda L.). The sheaths investigated were formed during extremes of soil moisture availability. In both increment sheaths the radial and longitudinal trends of the respective anatomical features were similar; however, the sheaths differed in the degree and rate at which their size changed from the apex to the base of the tree. Soil moisture conditions directly affected the width of the annual rings, tracheid diameter, and wall thickness but not the fibril angle of tracheid walls.