Post on 14-May-2015
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