DISTRIBUTION OF LIGNIN IN SPRUCEWOOD AS DETERMINED BY ULTRAVIOLET MICROSCOPY

The distribution of lignin in black spruce has been determined quantitatively by the study of 0.5 μm transverse sections in a UV microscope. The average lignin concentration in the compound middle lamella was about twice that in the secondary wall. The lignin concentration of the middle lamella at the cell corners of adjacent tracheids was nearly four times that in the secondary wall but the volume of the secondary wall was much greater than the volume of the middle lamella. Thus, for earlywood, 72% of the total lignin was in the secondary wall leaving only 28% in the compound middle lamella and cell corner middle lamella regions. The corresponding values for latewood were 82% and 18% respectively. Use of oblique longitudinal sections of 0.1 μm thick permitted the resolution of the compound middle lamella. The lignin concentration in the true middle lamella was found to be equal to that in the cell corner middle lamella and the primary wall lignin content to be about twice that in the secondary wall. © 1969 Springer-Verlag.