Spruce cell wall components

The types and relative abundances of cellulose, hemicellulose, and lignin vary among wood cell types, between earlywood and latewood, and within individual cell walls. These distributional differences affect the relative resistance of the various components to degradation and are best worked out for spruce wood tracheids and birch wood fibers, which constitute roughly 95 and 80%, respectively, of the volumes of the corresponding woods (2, 5). 

The relative abundances of the major components in different cell wall layers of spruce Picea abies) tracheids are illustrated in Figure 2. The compound middle lamella (CML) contains 14% cellulose, 27% hemicellulose. 

The percentages of total biopolymer that reside within the different cell wall layers are illustrated in Figure 3. These percentages depend both on the compositions described and on the relative volumes of the layers themselves. The relative volumes vary between earlywood and latewood, and will be discussed for earlywood. On the basis of microscopic observation (4), the CML region accounts for about 12% of the total tissue volume of spmce earlywood. This wall component contains approximately 4, 21, and 27%, respectively, of the total cellulose, hemicellulose, and lignin in spruce tracheids. The adjacent Si layer has a comparable volume and contains 9, 23, and 10% of the total cellulose, hemicellulose, and lignin, respectively. 

---