Lignin Distribution in Cell Walls

To determine the distribution of lignin from bromine analysis, it is essential to know the reactivity of bromine toward lignin in different morphological regions. For black spruce (Picea mariana), Douglas-fir (Pseudotsuga menziesii) and loblolly pine (Pinus taeda), the lignin in the secondary wall of tracheids is 1.7 

The substitution in Eq. (1) of the data for Vj, kMI lML/ls, and 1 /1, gives the weight concentration of lignin in the secondary wall (Cs) from which the 

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De Micco, V. Aronne, G. Combined histochemistry and autofluorescence for identifying lignin distribution in cell walls. Biotech. Histochem. 2007, 82, 209-216. 

Table 12.1 shows PALF chemical composition obtained from previous studies. It can be seen that the content of cellulose was in the range of 67.12-82% hemi-celluloses 9.45-18.80%, hoUocellulose 80-87.56%, lignin 4.4—15.4%, pectin 1.2-3%, fat and wax 3.2-4.2%, and ash 0.9-2.7%. Differing composition may be attributed to factors including source of fibers, age of fibers, climate conditions, and the process to obtain the fibers. Chemical composition, lignin distribution, and cell wall structure of PALF were analyzed in Abdul Khalil et al. (2006). Using transmission electron microscopy the authors confirmed that PALF cell wall structure... 

It is well known that the structure, distribution and properties of protolignin in cell walls vary according to cell type and morphological location. This is based upon extensive studies on topochemical properties of lignin using various methods such as ultraviolet microscopic photometry (1,2), bromination-SEM-EDXA (3) and other physical or chemical analyses of isolated tissue fractions (4). 

Russ JC (1974) X-ray microanalysis in the biological sciences J Submicrosc Cytol 6 55-79 Sachs IB, Clark IT, Pew JC (1963) Investigation of lignin distribution in the cell wall of certain woods J Polym Sci Part C 2 203-212... 

Although electronic absorption spectroscopy in its reflectance variation has been used to assess the distribution of lignin across the cell walls of tracheids (J6, 17), no method based on electronic or IR spectroscopy has been developed to enable quantitative determination of the lignin content of wood surfaces. 

An important characteristic of these wood cells is the heterogeneous distribution of cellulose, hemicelluloses and lignins over the cell walls. For example, lignins are located mainly in the middle lamellae (ML) and glue the individual fibers together. A smaller quantity is also distributed throughout the secondary wall with a higher concentration in the S3 layer. 

Figure 4. The distribution of lignin within different cell wall components of birch wood. (Constructed from data in ref. 4.)...

Such a study has been performed on a model plant system, the Nitella flexilis cell wall [1, 2, 3]. This freshwater alga has giant intemodal cells whose easily isolated cell walls constitute a simplified model of higher plant cell walls it has no lignin and its pectin is not methylesterified. Isolated cell walls are cut in pieces and distributed in different lots over the whole exchange isotherm to reduce variability between experimental points. 

Cellulose, hemicelluloses, and lignin are the main components of cell walls in woody plants. For a long time, these plant polymers have stimulated the interest of many plant botanists and biochemists in terms of their biosynthetic pathways, functional interrelationships, and anatomical distribution. 

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