WOOD PRODUCTS EXAM I

Vessels

Type of cell responsible for hardwoods being described as “porous”

Early wood and late wood

2 types of cell configuration that comprise a growth ring

Cellulose, Hemicellulose, Lignin

3 compounds that compose cellular structures

Microfibrils

Bundles of cellulose and hemicellulose that are oriented in the same direction in a layer of the secondary cell wall

Pits

Openings between conductive and/or parenchyma cells that permit exchange of water and/or food products

Which xylem has a more orderly appearance?

Softwoods

Which cell type is most common in softwoods?

Trachied

A vessel is composed of what cell type?

Parenchyma

Ring porous

Diffuse porous

Semi-diffuse porous/semi-ring porous

Which has thicker cell walls in softwoods, late wood or early wood?

Latewood

Anisotropism

Wood exhibits different properties when viewed from different angles

Made of parenchyma cells, living part of the wood where water and nutrients are transported

Sapwood

Heartwood

Dead parenchyma cells

Cellulose role in wood production

Provides structural support (in cell wall)

Hemicellulose role in wood production

Primary component of middle lamella (void between cells) of cell, provides support and structure to the cell wall

Lignin role in wood production

Acts as an adhesive (glue) in cell wall, holding together cellulose and lignin, reason for stiffness of wood

Why mature wood is longitudinally stable?

Because of the microfibril angles in the three secondary walls

Simple pit

Parenchyma to parenchyma

Border pit

Conductive to conductive

Half border pit

Parenchyma to conductive

Pit membrane modification in softwood bordered pit pairs

Torus/margo found mostly in softwoods

What causes differences in texture?

Size of vessels, diffuse porous (fine) vs. ring porous (coarse)

Tracheids role in softwood structure

Tracheids compose 95% of wood cell types in softwoods, provides structure and moves xylem sap

Resin canals (and epithelial cells)

Resin canals move and put out sap, epithelial cells form resin canals (not present in hardwoods)

Uniseriate

Cells arranged in single row

Fusiform

Wide in middle and thinner at each end

Homocellular

Made up of one type of ray cell: all ray procumbent cells or all ray upright cells

Hetrocellular

Made up of 2 types of ray cells: ray procumbent cell and ray upright cell found in the same ray

Types of cells in hardwoods

Parenchyma, fibers, vessel elements, tracheids

Vessels

Made of vessel elements, move xylem sap (water)

Tyloses

Parenchyma cells balloon out cytoplasm after death to fill vessels, forming tyloses

Parenchyma

Starch storage

Trachieds

Move water

Juvenile wood

Wood produced in lateral cambium is close to apical meristem

What can be done to make juvenile wood less of a problem in wood utilization?

Make stands denser to get lateral cambium away from apical meristem

Reaction wood

Produced when main stem or a branch is subjected to unusual orientations or mechanical stresses

Two types of reaction woods and where do they occur with respects to species group and location on the tree?

Compression on softwood (inside bend)

Tension on hardwoods (outside bend)

Why is each type of reaction wood longitudinally unstable?

G-layer is loose and provides no reistance to shinkrage or swelling in other secondary cell wall layers