Contributions to the Chemistry of the Plant Cell Wall Vi. Further Studies on the Location of Lignin in the Cell Walls of Wood

The Cell Walls of Higher Plants: Their Composition, Structure and Growth

“…This group of substances, like the other cell-wall components so far discussed, has no precise definition and relates to material detected by biological staining techniques (Dadswell & Wardrop, 1955; Harlow, 1939; Mehta, 1925u, b), absorption of ultraviolet light (maximum at about 2800 a) (Buchanan, Brauns & Leaf, 1949; Lange, 1 9 5 4~) or the use of arbitrary chemical procedures for its isolation.…”

“…The latter did not retain the original cell wall shape as did that in the middle lamella region but disintegrated as a fine powder. Ritter suggested that the lignin was deposited around the fibrils of cellulose, Harlow (1932) confirmed that most of the lignin in the wall was concentrated around the middle lamella region, but disagreed about the state of the lignin in the region of the secondary layers. He showed that generally lignin was found in the secondary wall, more being present in softwood than in hardwood fibres and that it was possible to dissolve out the polysaccharides keeping the lignin residues of these regions intact.…”

“…(iii) Stains and other microscopic techniques with tissue sections. T h e comprehensive work of Harlow (1939) and Mehta (1925 a, b) on the use of stains and solubility tests on plant tissues indicates the limitations in specificity of some of the common stains employed and shows that the detection of pectic substances by ruthenium red (Carre PL Horne, 1927;Mangin, 1893) although fairly reliable must be carried out with solubility tests and other experiments (Kerr & Bailey, 1934). Ruthenium red will stain compounds similar to pectin which contain carboxyl groups and this includes some of the hemicelluloses such as xylans.…”

“…To the histologist the criteria for the identification of cellulose are dependent upon birefringence or dichroism produced by certain dyes, sometimes supplemented with a few solubility tests (Harlow, 1939) which can be performed on the tissue section itself (Frey-Wyssling & Muhlethaler, 1951 ; Mehta, 1925b; Mericle & Whaley, 1953). This at the best indicates that the structures observed contain cellulose molecules of an indefinite chemical composition mixed with material of an indefinite nature.…”