Dendroid nature of trees - Formation

of wood - Role of cambium - anticlinal

& periclinal division.

Alex K George

I MSc. Forestry

WOOD:

Nature's Best Building Material

• One of the oldest construction materials

– easily produced & handled

– widely used

• Only naturally renewable building material

Wood is orthotropic, elasto-plasitc, hygroscopic,

organic (50% C; 44% O; 6% H; 0.1% N)

material

Structure of a Tree• root system

– anchor

– absorption of moisture &

minerals

• trunk

– support crown

– transport

– * structural timber

• crown

– produce food, seed

Orthotropic Material/ anisotropic

Orthotropic means that

wood has unique and

independent properties in

the directions of three

mutually perpendicular

axes-

longitudinal, radial, and

tangential.

Orthotropic Material

The properties of wood

parallel to the grain are

higher than those

perpendicular to the grain.

Formation of wood

• Growth and development of higher plants is

governed by cell division (mitotic).

1. Apical meristem – tips – height

2. Lateral meristem – cylindrical column –

below bark – vascular cambium – diameter

VS: thin meristematic layer located between

xylem and phloem.

• Division of cambial cells – Sachs (1878)

1. Periclinal division – radial direction (inside and

outside)

2. Anticlinal division – circumference (side)

Periclinal division of cambial cells to produce

secondary xylem occurs far more frequently than

divisions yielding secondary phloem.

Component cells of cambium: squared brick (c.s)

1. Fusiform initials – elongate and tapering

in vertical orientation – divide to

a. vessel elements

b. fibers

c. axial parenchyma

2. Ray initials – cuboidal – divide to

a. ray

b. ray parenchyma

Thank you.