Tree Trunk zones Wood zones Growth rings Cellular anatomy Microfibril Chemical Ultrastructural...
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Transcript of Tree Trunk zones Wood zones Growth rings Cellular anatomy Microfibril Chemical Ultrastructural...
TreeTrunk zones
Wood zones
Growth rings
Cellularanatomy
Microfibril
Chemical
Ultrastructural
Levels of scale in study of wood structure
Wood Chemistry
WOOD
Holocellulose Lignin(s) Extractives Ash
Cellulose Hemicellulose(s)
Crystals in longitudinal parenchyma
(Côté)
Crystals in wood
rhomboidal styloid raphides druses
(Kollmann and Cote)
Wood Extractives
• Pathological
vs.
Physiological
• Aliphatics
Terpenes and terpenoids
Phenolics
• Resin acids
Fats
Waxes
Terpenes
Flavanoids
Lignans
Stilbenes
Structure of monosaccharidescommonly found in the cell wall
Glucose
Glucose
Glucose
Cellobiose
1-4 glycosidic bond
Cellulose
Hemicelluloses – sugar monomers
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Cellulose and Hemicellulose(s)
Glucose Mannose Mannose Mannose
Galactose Acetyl
Glucose Glucose Glucose Glucose
Cellulose
Xylose Xylose Xylose Xylose
Acetyl Glucoronic acid7
Hardwood xylan
Softwood galactoglucomannan
Cellulose
Hemicellulose (softwood)
Hemicellulose (hardwood)
Cellulose and Hemicellulose(s)
Hemicelluloses vs. Cellulose
• Additional sugar monomer types
• Lower degree of polymerization (150-200)
• Additional chemical functional groups
• Branched chain structure
• Less crystalline
15
Lignin – Phenyl propane unit
16
softwoods & hardwoods
hardwoods
Lignin – inter-phenyl propane unit linkages
Lignin – inter-phenyl propane unit linkages
Representative structure of lignin
(Adler)
Another ligninmodel structure!!
Cell Wall Constituents
Polymer Cellulose Hemicellulose(s) Lignin(s)
Monomer(s) Glucose Various monosaccharides
Phenyl propane
Shape Straight chain Branched chain 3-D
Order Crystalline Semi-crystalline Amorphous
% of Wood 45-50 20-35 20-35
Degree of Polymerization
10,000 150-200 50-500
Softwood Hardwood
Cellulose 45 – 50% 45 – 50%
Hemicellulose(s) 18 – 25% 25 – 35%
Lignin(s) 25 – 35% 20 – 25%
Chemical composition of wood
Ranges of scale in cell wall structure
Cellulose
--- Glucose ------- Glucose ------- Glucose ------- Glucose ---
Cellulose
Glucose vs. Mannose
Glucose vs. Mannose
H
OH
Relative sizes of atoms
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
Cellulose
covalent bonds
intra-molecular hydrogen bonds
inter-molecular hydrogen bonds
Wood Ultrastructure - Microfibril
Wood Ultrastructure - Microfibril
Lamella
Lamella
Cell Wall Layers
True middle lamella
Primary wall Secondary wall
S1
S2
S3Lumen
Cell Wall Layers
(Côté)
Cell wall layers
Layer Lamellae % Ө Spirality Order
TML --- Variable --- --- None
P --- 5 --- --- Poor
S1 4-6 7 50-70° S + Z Good
S2 30-150 85 10-30° Z High
S3 2-4 3 60-90° S + Z Fair
(Princes Risborough Laboratory)
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)
Chemical pulpingMechanical pulping
Lignin distribution – effects on pulping yields
OH
OH
OH O
H
OH
OH
Water in cell wall
OH
OH
OH
OH
OH
OH
OH
H
OH
H
OH
H
OH
H
OH
H
OH
H
Microfibril angle and wood shrinkage
S2Ɵ relatively smallLeads to little longitudinal shrinkage
S2Ɵ relatively largeLeads to more longitudinal shrinkage