Translocation

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  • Created by: ElishaG
  • Created on: 05-04-17 19:56
What is translocation?
The mass flow of sucrose in the phloem from a 'source' to a 'sink'.
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What is mass flow?
The movement of a body of sugars from an area of high pressure to an area of low pressure.
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What is a source?
Area of the plant that is producing sucrose and causing the sap to be under high pressure in the phloem.For example, a photosynthesising leaf in summer.
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What is a sink?
A part of the plant that is using sucrose. Therefore the sap in the phloem is at low pressure e.g. growing root in summer.
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What are the three stages of translocation?
1)Active loading.2)Mass Flow.3)Active unloading.
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Describe the 4 stages of active loading.
1)Companion cells actively transport H+ out of cell.2)Conc. gradient set up, H+ ions diffuse back to companion cells through protein.3)Sucrose carried through protein into companion cell by facilitated diffusion.4)Sucrose moves to sieve tube elements
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How does the sucrose get to the sieve tube elements?
Via the plasmodesmata.
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Describe the 2 stages of mass flow.
1)Sucrose lowers water potential of sieve tube element.2)Causes water to enter by osmosis from xylem-increases hydrostatic pressure and forces water and sucrose along phloem.
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Describe the 2 stages of active unloading.
1)Sucrose actively unloaded from sieve tube element into sink cell (root).2)When sucrose leaves phloem, water potential increases and it leaves by osmosis- decreases hydrostatic pressure, this creates a pressure gradient.
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LOOK AT DIAGRAM FOR TRANSLOCATION,,,,,
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Other cards in this set

Card 2

Front

What is mass flow?

Back

The movement of a body of sugars from an area of high pressure to an area of low pressure.

Card 3

Front

What is a source?

Back

Preview of the front of card 3

Card 4

Front

What is a sink?

Back

Preview of the front of card 4

Card 5

Front

What are the three stages of translocation?

Back

Preview of the front of card 5
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