Movement of water up stems and transpiration

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  • Created by: elyornais
  • Created on: 22-03-15 15:16
How is water lost by evaporation replaced?
By water reaching the mesophyll cells from the xylem by apoplastic or symplastic pathway
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What are the two main factors responsible for the movement of water up the xylem?
Root pressure and cohesion-tension.
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How does cohesion-tension work?
Water evaporates from leaves. H2O molecules form H bonds between each other +stick together. Water forms continuous pathway along mesophyll cells+down xylem.Water pulled as result of transpiration.This puts xylem under tension.
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At what time of day is transpiration rate greatest and what effect would this have on the diameter of a tree trunk?
During the day. There is more tension(negative pressure) in the xylem so diameter shrinks in size.
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What would happen if a xylem vessel broke and air entered it?
The plant can no longer draw up water because the continuous column of water is broke and molecules can't stick together.
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How does light effect transpiration?
Stomata open in light because photosynthesis happens in light. When stomata is open, water moves out of the leaf. Increase in light intensity=increase in rate of transpiration.
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What effect does temperature have on transpiration.
Temp rise increases kinetic energy and speed of movement of water molecules. Increases the rate of evaporation=rate of transpiration increases. Also decreases humidity of air outside leaf so decreases water potential.
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What effect would increased air movement have on transpiration.
Increased rate of transpiration.
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What are Xerophytes?
Plants that are adapted to living in areas where their water losses due to transpiration may exceed their water uptake.
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What is the purpose of a thick cuticle?
reduce water loss.
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How does rolling up leaves reduce water loss?
Protects the lower epidermis from outside and traps a region of still air within the rolled leaf. This region becomes saturated with water so there's no water potential gradient, transpiration is reduced.
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What does a thick layer of hairs on leaves do?
Traps moist air next to the leaf surface. Reduces the water potential gradient and less water is lost by transpiration.
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What is another feature that can trap moist air next to the leaves?
Stomata in pits or grooves.
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How can surface area be reduced to prevent water loss by transpiration?
Smaller surface area to volume ratio of the leaves.
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Other cards in this set

Card 2

Front

What are the two main factors responsible for the movement of water up the xylem?

Back

Root pressure and cohesion-tension.

Card 3

Front

How does cohesion-tension work?

Back

Preview of the front of card 3

Card 4

Front

At what time of day is transpiration rate greatest and what effect would this have on the diameter of a tree trunk?

Back

Preview of the front of card 4

Card 5

Front

What would happen if a xylem vessel broke and air entered it?

Back

Preview of the front of card 5
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