1. Tree Trunk zones Wood zones Growth rings Cellular anatomy Microfibril Chemical Ultrastructural Levels of scale in study of wood structure

2. Wood Chemistry WOOD Holocellulose CelluloseHemicellulose(s) Lignin(s)ExtractivesAsh

3. Crystals in longitudinal parenchyma (Côté)

4. Crystals in wood rhomboidalstyloidraphidesdruses (Kollmann and Cote)

5. Wood Extractives Pathological vs. Physiological Aliphatics Terpenes and terpenoids Phenolics Resin acids Fats Waxes Terpenes Flavanoids Lignans Stilbenes

6. Structure of monosaccharides commonly found in the cell wall

7. Glucose

10. Cellobiose

11. 1-4 glycosidic bond Cellulose

12. Hemicelluloses – sugar monomers

13. 13 Cellulose and Hemicellulose(s) Glucose Mannose Mannose Mannose Galactose Acetyl Glucose Glucose Cellulose Xylose Xylose Xylose Xylose Acetyl Glucoronic acid 7 Hardwood xylan Softwood galactoglucomannan

14. Cellulose Hemicellulose (softwood) Hemicellulose (hardwood) Cellulose and Hemicellulose(s)

15. Hemicelluloses vs. Cellulose Additional sugar monomer types Lower degree of polymerization (150-200) Additional chemical functional groups Branched chain structure Less crystalline 15

16. Lignin – Phenyl propane unit 16

17. softwoods & hardwoods hardwoods

18. Lignin – inter-phenyl propane unit linkages

20. Representative structure of lignin (Adler)

21. Another lignin model structure!!

22. Cell Wall Constituents PolymerCelluloseHemicellulose(s)Lignin(s) Monomer(s)GlucoseVarious monosaccharides Phenyl propane ShapeStraight chainBranched chain3-D OrderCrystallineSemi-crystallineAmorphous % of Wood45-5020-35 Degree of Polymerization 10,000150-20050-500

23. SoftwoodHardwood Cellulose 45 – 50% Hemicellulose(s) 18 – 25%25 – 35% Lignin(s) 25 – 35%20 – 25% Chemical composition of wood

24. Ranges of scale in cell wall structure

25. Cellulose --- Glucose ------- Glucose ------- Glucose ------- Glucose ---

26. Cellulose

27. Glucose vs. Mannose

28. H OH

29. Relative sizes of atoms

30. Adjacent glucose units can come close enough together to permit extensive hydrogen bonding to occur. Adjacent mannose units cannot come together as closely as glucose units and less hydrogen bonding occurs. Glucose vs. Mannose

31. Cellulose covalent bonds intra-molecular hydrogen bonds inter-molecular hydrogen bonds

32. Wood Ultrastructure - Microfibril

34. Lamella

36. Cell Wall Layers True middle lamella Primary wall Secondary wall S1 S2 S3 Lumen

37. Cell Wall Layers (Côté)

38. Cell wall layers LayerLamellae%ӨSpiralityOrder TML---Variable--- None P---5 Poor S14-6750-70°S + ZGood S230-1508510-30°ZHigh S32-4360-90°S + ZFair (Princes Risborough Laboratory)

40. 40 Cell wall topochemistry (Panshin & de Zeeuw) Distribution of the principle chemical components within the various layers of the cell wall Distribution of lignin in cell walls of hardwood fibers (darker = more lignin )

41. Chemical pulpingMechanical pulping Lignin distribution – effects on pulping yields

42. O H O H O H O H O H O H Water in cell wall O H O H O H O H O H O H O H H O H H O H H O H H O H H O H H

43. Microfibril angle and wood shrinkage S 2 Ɵ relatively small Leads to little longitudinal shrinkage S 2 Ɵ relatively large Leads to more longitudinal shrinkage