WOOD MATERIALS TECHNOLOGY

4th Edition

Chapter 9How Trees Grow

Parts of a tree

Leaves

Branches

Trunk

Roots

Function of various partsRoots - anchor the tree and absorb moisture and

minerals from the soil, and protect the tree from weather insects and animal attack.

Trunk - supports the branches and is the main source of wood we use

Bark - protects the wood on the inside from attack

Leaves - used to produce food for the tree to grow

Photosynthesis Green colouring in leaves

is called chlorophyllSun shines on chlorophyll

in presence of CO2 + H2O causes a chemical reaction called Photosynthesis to occur

Photosynthesis produces glucose (food for the tree) and oxygen

Transpiration Transpiration is the

loss of water from the leaves by evaporation

Transpiration is where Carbon Dioxide is taken from the air by the leaves, the leaves give out oxygen.

It occurs through tiny pores called stomata found on the underside of leaves

When there is little water available in the soil the stomata closes

Stages of growth of the young tree

Seed germinatesShoot grows to the surfaceRoot grows down into the soilSeedling develops roots and leavesSeedling grows into a sapling

Annual ringsAnnual rings show the age of the tree – 1 ring per year

− spring/summer = rapid growth & larger cells− autumn/winter = slower growth & smaller cells

Parts of the trunk

Bast:A thin moist layer of inner barkNew bark cells are produced as the old cells die off

Cambium layer:This is a layer of cells under the bark.This is where the growth of the tree occursEach year the cells are added to the outside of the tree

forming a growth ring.

SapwoodAs the tree grows layers of cells are added to the sapwood It is light coloured wood in the trunk outside the

heartwood

Heartwood Darker colour than sapwoodFound beside the pith close to the centre

of the treeProvides support for the treeHeartwood is more durable and resistant

to fungal and insect attack than sapwood

PithPith is found in the centre of the trunk and

is made up of original sapling cells

What is the name given to the darker wood in the centre of the trunk?

− The heartwood

Name the processes occurring in a tree

The living tree

− Photosynthesis− Transpiration