Transcript How a tree grows?

How a tree grows?
Tree Basics
 Tree species are some of the largest
living organisms on earth.
 As a strict definition, trees can be
defined as woody plants that are at
least 20 feet tall at maturity
 They generally have one single
main trunk that remains
unbranched for several feet, and a
more or less well defined crown.
Bush
Tree Basics
 Trees are also perennial plants meaning
they live for many years, some even
thousands of years!
 Living in the same spot year after year is
not a simple task.
 Trees must be able to survive long dry
spells (they can't pack up and look for
water) and during the winter they must
survive cold weather.
Tree Basics
 Trees are used to make over 5,000 products
 All parts of a tree are used to make these products.
 Fruits and nuts of many trees are eaten by people and
wildlife. Apples, walnuts, acorns, and nutmeg are a few
of these products.
 Bark of trees is used to produce cinnamon, shoe polish,
and even aspirin.
 Stumps of pine trees are used in pine cleaners and in the
flavoring of orange sodas.
Tree Basics
 Foliage (or leaves) of trees are used to make waxes and
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crayons.
Bay leaves are used in cooking.
Sap of trees is used to make maple syrup.
Gums, which are found in the tree sap, are used in
hairspray, paints, soaps, cough syrups, and in ice cream.
Trunk of a tree is used to make lumber, furniture, and
other large wood products.
Branches of the tree are used to make paper products.
Tree Basics- Paper
 There are thousands of paper products that we use every
day. These products include: wrapping paper, newspapers,
books, posters, movie tickets, dollar bills, photographs,
and many more.
 Paper-making begins when trees are harvested and sent to
a paper mill on log trucks.
 The bark of the trees is peeled off and the logs are
pulverized into cereal-size pieces.
 Wood chips are then placed in “pulp cookers” with
chemicals and steam.
Tree Basics- Paper
 The hot mixture breaks down the wood chips into even
smaller pieces.
 This combination of wood fibers and water is known as
pulp.
 Pulp is cleaned, bleached, and/or dyed.
 Pulp is then sprayed onto large wire screens that allow
the excess water to drain out of the mixture.
 Paper mat that is left is dried over steam-heated rollers.
Tree Basics
 Trees are generally split into two broad groups:
 gymnosperms and angiosperms
Gymnosperms
 Gymnosperms are a taxonomic class that includes plants
whose seeds are not enclosed in an ovule.
 The word gymnosperm when translated actually means
"naked seed".
 Gymnosperms include most evergreen species such as pines,
spruces and firs.
Gymnosperm
Gymnosperms
 Some gymnosperms, including larch
and ginkgo, do lose their leaves in the
winter.
 Gymnosperms are often called
"conifers" since many of them produce
seeds in cones, as well as "softwoods"
since many of them have softer wood.
Angiosperms
Angiosperms
 Angiosperms are a taxonomic class in which mature seeds are
surrounded by an ovule.
 The word angiosperm means "covered seed".
 Most angiosperms are broadleaf, deciduous trees, which lose
their leaves in the winter.
 Members of this group include oak, maple, birch and hickory
to name just a few.
 These trees are also known as hardwoods since generally their
wood is harder than gymnosperms.
A Tree and its Trunk
 Roots absorb water and nutrients from the soil,
which are then transported up the tree trunk in cells
that act much like pipes.
 This allows the leaves to obtain water and nutrients
that are necessary for the manufacture of food from
light energy (photosynthesis).
 Food made in the leaves is then transported down to
the roots and to other parts of the tree for growth.
 The "pipes" in the trunk are known as vascular
tissue. It is this vascular tissue which we exploit to
make paper and other forest products.
A tree trunk!
 Food made in the leaves is then transported
down to the roots and to other parts of the
tree for growth.
 The "pipes" in the trunk are known as
vascular tissue. It is this vascular tissue
which we exploit to make paper and other
forest products.
 Wood is primarily made of xylem
(tracheids in conifers, vessel elements in
hardwoods) that behave very much like a
bundle of straws.
A tree trunk!
 The trunk of a tree is composed of several basic parts.
 Bark is an outer covering of dead tissue, which protects the
tree from weather, disease, insects, fire and mechanical
injury.
 Bark characteristics can vary greatly from tree to tree and can
be useful in identification.
Bark!
 Tree bark can vary greatly throughout the life of a tree, often becoming rougher as a
tree grows.
 Only a few trees (such as Beech) retain smooth bark throughout their life.
 Below are examples of just a few of the many different bark types.
Beech
Shagbark hickory
Pitch pine
Tulip-poplar
Yellow birch
Bark
 The next layer immediately inside the bark is
called the phloem.
 Phloem is a thin layer of living cells and is
responsible for transporting food around the
tree.
 Large amounts of sugar travel down the
phloem to the roots.
 Sugar may also travel up the phloem to other
parts of a tree that need energy for growth and
maintenance.
Cambium
 The next portion of the trunk is called the
vascular cambium.
 Cambium is a very thin layer of living tissue
which produces new phloem to its outside
and new xylem to its inside.
 Cambium is most active in the spring and
early summer when most tree growth is
taking place.
 Inside the vascular cambium is the largest
portion of the trunk known as the xylem.
 Cambium Growth
Xylem
 Xylem is composed of dead, thick cells that act as
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pipes for transporting water and nutrients up the
tree.
The active portion of the xylem is known as the
sapwood.
Sapwood is found near the outside of the tree.
Older xylem is known as heartwood and is found
in the middle of the trunk.
Heartwood is often darker in color and is not
very active in transport.
The darker color is caused by resins, oils and
minerals, which are deposited as the tree
grows. The xylem (sapwood and heartwood)
makes up the majority of a tree trunk.
Xylem
 On close inspection of a tree trunk one can see
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individual xylem cells.
They are arranged longitudinally.
The shape of xylem cells is what gives wood its
unique characteristics.
Pine trees and other conifers have long, narrow
xylem cells called tracheids.
This shape provides a surface that gives strength to
paper products. This is one reason why pine fiber is
so valuable to the forest products industry.
Growth Rings
 What makes these rings?
 An annual ring is one year's worth of xylem
growth.
 In most trees the xylem cells formed in the
spring are larger than those formed later in
the summer.
 The difference in size results in what appears
as a ring.