SMT202 Exam 2

SMT202 Ilona Peszlen Wood Anatomy Exam 2

What Direction is Primary Growth?

Up

Apical Meristem

From the Tips- Roots and Shoots. Produces primary tissues

Lateral Meristem

Side

Vascular Cambium

Growth in Diameter

Cork Cambium

Growth in Bark

Secondary Growth

Outward

Primary Tissues

Epidermis

Cortex

Primary Phloem

Primary Xylem

Pith

Where does Vascular Cambium Grow

Between Xylem and Phloem

What are the two types of cambium initials

Fusiform initial

Ray initial

Ray initial

beginning of rays. Horizontal growth

Fusiform inital

Vertical Growth

Perclinal division

division that splits cambium cells into one cambium and one xylem

increases diameter

Anticlinal division

division that splits cambium cells into two cambium

increases circumference

Wood Cell Growth Process

Cambium

Enlarge

Secondary Wall

Ligninification

Death

How many rings of Juvenile Wood

8-25 rings

What factors influence the amount of Juvenile wood

Species

Genotype

Age

Environment

Growth Conditions

Juvenile Wood Specific Gravity

LOWER specific gravity

Juvenile Wood Longitudinal Shrinkage

HIGHER Longitudinal Shrinkage

Juvenile Wood Radial Shrinkage

LOWER radial shrinkage

Juvenile Wood Density

LOW density

Juvenile Wood Strenth

WEAK

Juvenile Wood Chemical Properties

High Moisture

Higher Lignin and hemicellulose

Low cellulose

Juvenile Softwood

Short thin trachieds

Low Density

Larger MFA

High lignin, low cellulose

Juvenile Hardwood

Short thins FIBERS

Low Density

High Holocellulose

How is Heartwood Formed

When Sapwood Stops Conducting Water

What can cause Sapwood Blockages

Air Bubbles

Pit Asperation

Tyloses

Extractives

What factors control Parenchyma death

Spatial Control

Temporal Control

Spatial Control

How far from cambium

Temporal Control

Age of the Cell

Extractives

Organic compounds made by parenchyma cells

Effects Wood Permability+Toxicity

Good Effects of Extractives

Good Color

Durability

High Compressive Stability

Bad Effects of Extractives

Hard to Pulp

Tannins corrode metal

Colors mitigate while drying

Interferes with paint, glue, etc drying

Cell Wall Element %

Carbon 49%

Hydrogen 6%

Oxygen 44%

Nitrogen >0.1%

Ash <0.1%

Cell Wall Organic Polymers %

Cellulose 50%

Hemicellulose 25%

Lignin 25%

Cellulose

Most Abundant Polymer on Earth

Long Straight Chain 10um

Strong Along Axis

Hemicellulose

Branched Chain Polymer

Variable in composition

Made of Sugar Units

Lignin

Made of Phenylpropane

Stable but difficult to isolate

Resistant to decay

Provides Structure

What are Microfibrals

Cellulose fiber structures

Cellulose in 1 Fibral

40-100 Cellulose

Fibrals in a Microfibral

4-6 Fibral

Compound Middle Lamella

Intercellular Substance made of primary walls and true middle Lamella

Pectin + Lignin

.2-2 um

Primary Wall

Thin and Stretchable

Microfibrals randomly arranged

Hemicellulose, Pectin, Lignin

Secondary Wall

Made of 3 Layers- S1,S2,S3

S2 largest layer 5-10um

Cellulose, Hemicellulose, Lignin

Size of Secondary Wall Layers

S1: 4-6 Lamella

S2: 30-150 Lamella

S3: 0-6 Lamella

Tertiary Wall

Not always present

Warty Layer- Softwoods

Gelatinous Layer- Hardwoods

Microfibral Angle (MFA)

Primary: Random

S1: 50-70 degrees

S2: 10-20 degrees

S3: 60-90 degrees

Reaction Wood

Forms as a Reaction to an event

Returns Stem to original angles

Compression Wood

Forms in Softwoods

Lower side of the tree

Higher Lignin 8-9%

Lower Cellulose 10%

Cellular Properties of Compression Wood

Rounded Trachieds

EW Trachieds have thicker cell walls

Short Trachieds with smaller pits

no S3

Physical Properties of Compression Wood

Higher Density 10-40%

High Compression Strength

Lower tensile and impact bending

Warps while drying

Tension Wood

Hardwoods

Wider Growth Rings

Adds G-Layer

G-Layer

Gelatinous Layer

Forms inside or replaces S3

Tension Wood Chemical Properties

Less Lignin 8-9%

More Cellulose 5-10%

Tension Wood Physical Properties

Higher Density 5-10%

Higher Longitudinal Shrinkage 1-2%

Collapses while Drying