Movement of water through roots

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  • Created by: elyornais
  • Created on: 20-03-15 10:25
What is the root hair cell?
The exchange surfaces in plants that are responisible for the absorption of water and mineral ions.
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Give 2 reasons why the root hairs are efficient exchange surfaces.
They provide a large surface area as they are very long and occur in thousands. They have a thin surface layer- materials move over easily
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How is water absorbed through the root hairs?
The soil solution that surrounds them have a high water potential while the root hairs and other cells have sugars, amino acids and mineral ions dissolved in them so have a lower water potential. Water moves by osmosis down this gradient.
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What are the two ways that water travels after being absorbed into the root hair cell?
- The apoplastic pathway(apoplast) -The symplastic pathway(symplast)
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How is water drawn into the root cortex?
Water is drawn into endodermal cells, pulls more water along behind it (cohesive properties of water molecules) creates a tension that draws water along the cell walls of the cells of the root cortex.
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Why is there little resistance to the pull of water along cell walls?
There are many water-filled spaces in the mesh-like structure of the cellulose wall.
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Where does the symplastic pathway take place?
Across the cytoplasm of the cells of the cortex.
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What is the symplastic pathway?
Tiny openings called plasodesmata, each one is filled with a thin strand of cytoplasm. There is a continuous column of cytoplasm from root hair cell to xylem.
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How does water move along the symplastic pathway?
Water enters by osmosis increases WP of root hair cell.->Root hair cell now has a higher WP than first cell in cortex.->osmosis->first cell in cortex now has higher WP than its neighbour-osmosis->carries on to each cell->WP gradient all the way.
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How is water forced into living protoplast from the apoplastic pathway?
The waterproof band that makes up the casparian strip prevents water from getting further along the cell wall.
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How does water get into the xylem?
Active transport of salts from the endodermal cells. Requires energy so only occurs in living cells. Carrier proteins in the cell surface membrane.
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What is the force that helps move water up the plant?
Root pressure.
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How does temperature affect root pressure?
Increases with a rise in temp, decreases with low temp.
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What do metabolic inhibitors, such as cyanide, do to the root pressure?
Prevent most energy release by respiration and cause root pressure to cease.
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What does a decrease in oxygen do to root pressure?
Causes a reduction in root pressure.
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Other cards in this set

Card 2

Front

Give 2 reasons why the root hairs are efficient exchange surfaces.

Back

They provide a large surface area as they are very long and occur in thousands. They have a thin surface layer- materials move over easily

Card 3

Front

How is water absorbed through the root hairs?

Back

Preview of the front of card 3

Card 4

Front

What are the two ways that water travels after being absorbed into the root hair cell?

Back

Preview of the front of card 4

Card 5

Front

How is water drawn into the root cortex?

Back

Preview of the front of card 5
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