Download 9.3 Water/Sugar Transport in Plants p. 331 – 340

9.3 Water/Sugar Transport in Plants
p. 331 – 340
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Water transport in xylem vessels
Sugar transport in phloem vessels
Uptake of water in roots
NO PUMP!!!! So what happens?
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Root pressure (osmosis)
Cohesion/adhesion of water
Transpiration
• Water enters the root due to osmosis
• Water moves up the xylem by
cohesion/adhesion of water
• Water leaves the leaves through
transpiration
Plant Vascular System
Interconnected tubes
 Extend throughout plant
 Made of Xylem and Phloem = specialized
TISSUES that transport water, minerals and
sugars throughout the plant
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Xylem
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Transports water and dissolved minerals
from soil to leaves
Start out as living cells then DIE
 Only the cell walls remain
 Cells linked end to end to make long
tubes called XYLEM VESSELS
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Xylem Vessels
Xylem Vessels
Several cell types: tracheids and vessel
elements
Phloem
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Transport sugar (sap) from leaves to rest
of plant
Phloem Vessels
Live cells
 Arranged end to end in long connecting
tubes
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SPECIALIZED PHLOEM CELLS
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Sieve tubes and companion cells are
specialized to carry sap (sugar water)
How does water move through the
plant without a pump????
H20 absorption in roots
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Root hairs increase surface area for
osmosis
1. Root Pressure
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Soil outside root is hypotonic to root cell
so water enters cell by osmosis
2. Cohesion of Water Molecules
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Water sticks to other water molecules
and forms a long chain of water
molecules and pull each other along
3. Adhesion of Water Molecules
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Water sticks to inside walls of xylem
4. Transpiration of water out of leaves
The water concentration is higher inside
the leaf cells than outside (in air)
 Therefore, water moves from an area of
high concentration (HYPOTONIC inside
the cells) to an area of lower
concentration (HYPERTONIC outside the
cells)
 As water molecules move out, they “pull”
the string of water molecules up through
the xylem
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Transpiration - animation
http://techalive.mtu.edu/meec/module01/Transpiration.htm
VIDEO CLIPS: WATER TRANSPORT
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VIDEO 1 – Water transport in plants
http://www.youtube.com/watch?gl=CA&hl=en&v=J1PqU
B7Tu3Y
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VIDEO 2 – Vascular System
http://www.youtube.com/watch?gl=CA&hl=en&v=w6f2BiFi
XiM
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VIDEO 3 - Transpiration
PHLOEM TRANSPORT – SUGAR
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1. Glucose is produced in the leaves
(palisade cells and spongy mesophyll cells)
PHLOEM TRANSPORT
2. Sugars are actively transported from the
LEAVES to the PHLOEM tissue
What does “active transport” mean?
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a)
b)
PHLOEM TRANSPORT
3. Once the sugars are “pumped” into the
phloem tissue, the water follows due to
osmosis
 After the sugars have left the phloem
tissue, what is the tonicity of the palisade
cells in relation to the phloem tissue?
 Which way does the water flow?
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PHLOEM TRANSPORT
4. After the water flows INTO the
phloem tissue, pressure is very high (ie –
many particles in a confined space)
 Pressure gradients always try to reach
equilibrium – therefore, the sap/water
moves from high pressure to low
pressure (ie – DOWN the phloem tubes
to the roots)
 The pressure in the root cells is relatively
low compared to the phloem tubes
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PHLOEM TRANSPORT
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http://www.pearsoned.ca/school/science1
1/biology11/sugartransport.html
Malpighi’s Experiment – Tree Girdling
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In 1686, Italian scientist Marcello Malpighi
wanted to find out what would happen if
he removed a ring of phloem tissue from
a tree.
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He learned that a swelling developed
above the ring and a sweet-tasting fluid
oozed out of this swelling.
He also discovered that his trees became
weakened and died soon after the ring
was removed.
 Why did the trees die?
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ASSIGNMENT: Check Your Understanding
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