Transport and Transpiration
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Transcript of Transport and Transpiration
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Transport and water relations
in plants
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Transport of water and food in
plants
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How does water get in?
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The roots
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How does it travel around the
plant?
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Water and plant cells
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Hydrostatic skeleton
The pressure of eachcell wall against itsneighbour results in
stiffness that allows theplant to stay upright.
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If cells dont
have
enough
water in
them thenthe plant
wilts.
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What is Transpiration?
The loss of water vapour throughEVAPORATION from the
stomata, on the underside of theleaves
http://www.cornwallwildlifetrust.org.uk/images/jpgs/transpiration_b.jpg -
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3 Forces help water
to travel through
the plant Osmotic pressure
as water enters
the root hairs
Cohesion
between water
molecules
Transpirationevaporation from
the stomata
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Stomata and Guard cells
Stomata are small pores
(holes) on the underside of
leaves
The cells to either side of
them are known as guard cells
These cells open or close the
stoma depending on how
much water is being lost from
the plant by transpiration
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Distribution of stomata
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Experiment to investigate
stomatal distribution
Use nail polish to make an impression of
the leaf When its dry, peel it off and view under a
medium power objective
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How guard cells work
Guard cells open to
allow gas exchange
They close to control
water loss
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When its wet
water enters the cell byosmosis
the outer walls can
expand but the inner
walls can not.
As the outer walls
enlarge, the inner walls
are pulled apart.
This opens the stoma
When its dry
Water leaves the cell by
osmosis
The guard cells shrink the stoma closes
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The potometer
A potometer can be used to
measure the rate of transpiration.
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Rate of transpiration
As the leaf loses water, so the air bubble
moves. The distance moved over a time
period is measured.
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The drier the air, the faster the transpiration rate!
Transpiration rate
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Plants have a transport system made upof tubes called xylem and phloem.
Xylem carries water and mineral salts from
the roots up the stem to the leaves. Phloem carries dissolved food from the
leaves to all parts of the plant.
Water passes into the root hairs from the
soil water by osmosis.
Summary
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Mineral salts are taken up by active
transport.
Leaves lose water to the air by
transpiration.
Transpiration is controlled by the openingand closing of stomata.
Environmental factors like wind, humidity
and temperature can affect transpiration.