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23 Cards in this Set
- Front
- Back
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Which factors affect the rate of water loss? |
Leaf number, number/size/position of stomata, waxy cuticle, light, temperature, humidity, wind, water availability. |
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How does the number of leaves affect the rate of water loss? |
More leaves mean a larger surface area, so more water is lost by transpiration |
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How does the number, size and position of the stomata affect the rate of water loss? |
More stomata cause more water to be lost quickly. If stomata are on the lower surface, water vapour is lost slower. |
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How does the waxy cuticle affect water loss? |
The thicker it is, the more evaporation is reduced as it's impermeable to water. |
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How does light affect the rate of water loss? |
In light, the stomata open to allow more gas exchange for photosynthesis. This allows more water to be lost via evaporation. |
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How does humidity affect the rate of water loss |
Increased humidity, decreases evaporation from the leaf as there's a smaller water vapour potential gradient |
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How does wind affect the rate of water loss? |
More wind removes more water vapour from the leaf surface. This increases the water vapour potential gradient and so, increases the rate of transpiration |
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How does water availability affect the rate of water loss? |
Decreased water availability causes the stomata to close which prevents gas exchange, so less photosynthesis occurs and less water is lost. |
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What is transpiration? |
The loss of water vapour from the aerial parts of the plant, such as through the stoma in the leaf. |
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Which 3 processes does water movement through the leaf involve? |
1)Osmosis form the xylem to mesophyll cells. 2)Evaporation from the surface of the mesophyll cells into the inter cellular spaces. 3)Diffusion of water vapour from the inter cellular spaces out through the stoma. |
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What does the transpiration stream mean? |
As water is lost from the xylem in the leaf, it's replaced from below. Water will move through the xylem from the roots to replace water which has been lost. |
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Why is transpiration important? |
Water in leaves is required for photosynthesis. Water is required for cell elongation and growth. Water keeps cells turgid. Evaporation keeps the plant cool The flow of water carries useful mineral ions up to the plant. |
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Why do stomata need to be open? |
To allow gas exchange, providing CO2 for photosynthesis. |
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What are xerophytes? |
Plants which can survive in dry places |
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What are xerophytic adaptations? |
Smaller leaves, thicker waxy cuticle, stomata closing when hot, hair on leaves, stomata in sunken pits, rolled leaves, loss of leaves, high salt concentration in cells. |
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How do smaller leaves reduce water loss? |
It reduces the surface area, decreasing water loss by transpiration. |
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How does a thicker waxy cuticle reduce water loss? |
It reduces evaporation from the leaf as it's impermeable to water, so it acts as a barrier |
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How do stoma closing when hot reduce water loss?
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It reduces transpiration when water availability is low |
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How does hair on leaves reduce water loss? |
It traps a layer of water vapour close to the surface of the leaf, decreasing the water vapour potential gradient. |
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How do stoma in sunken pits reduce water loss?
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It traps a layer of water vapour in the pit close to the surface of the leaf, decreasing the water vapour potential gradient |
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How do rolled leaves reduce water loss?
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They trap a layer of water vapour in the rolled leaf, decreasing the water vapour potential gradient. It also decreases surface area. |
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How does the loss of leaves reduce water loss? |
There are less stomata through which water can be lost via transpiration. |
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How does a high concentration of salt in cells reduce water loss?
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It decreases the water potential gradient in cells so less water is lost between cells. |
