Xylem,Phloem,Transpiration,Stomata

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  • Created by: Aleena
  • Created on: 26-04-18 20:20
What are Phloem vessels made of?
Phloem vessels are made of living cells called sieve tube elements.These have perforated end-pates to allow substances to flow thru them..
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Do sieve tubes elements have a nucleus?
No, so they have a companion cell to carry out its living function as well as its own
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What substances do Phloem vessels transport?
Phloem vessels transport food substances (mainly sugars) both up and down the stem to growing and storage tissues
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What directions do substances flow in Phloem vessels?What is the special name of this?
Up and down- we call this movement of food substances around the plant as Translocation
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What are Xylem vessels made of?
Xylem vessels are made of dead cells joined end to end- with no end walls between them and the lumen (hole). Th ethick side wall are made of cellulose, further strengthened by a material called Lignin-strong and stiff-supports plant
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What substances do Xylem vessels carry?
Xylem vessels carry water and minerals from the roots thru the shoots to the leaves
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What do we call the transportation of water and minerals?
Transpiration Stream
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What is Transpiration?
The loss of water from a plant, due to evaporation/diffusion of water form the plant's surface
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In what part of plant does Transpiration occur the most?
Transpiration occurs mostly in the leaves
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Why is there a constant Transpiration Stream?
Due to transpiration, there's a slight shortage of water in the leaves, so more water from the rest of the plant is drawn up thru the xylem vessels to replace the water lost-that causes more water to be drawn up from roots-always constant t.stream
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Is transpiration a side effect of photosynthesis?Explain?
Yes, cos leaves have Stomata for effiecient gas exchange but that means water vapour can also escape due to evaporation/diffusion cos usually there's more water in than outside the plant.
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Give the 4 benefits of Transpiration.
1)Constant stream of water from ground-keeps plant cool 2)provides plant with constant supply of water for photosynthesis 3)water creates turgor pressure in cells-supports plant 4) minerals needed by plant can also be transported with water
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What are the four factors that affect the rate of Transpiration?
Light Intensity,Temperature,Windiness and Humidity
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How does an increase in light intensity affect the rate of transpiration?
Rate of Transpiration increases cos More light=increases rate of photosynthesis=stomata open to let CO2 enter in-so water can escape thru stomata as it's open. But when its dark, photosynthesis can't happen so stomata are closed-so water can't escape
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How does an increase in temperature affect the rate of of transpiration?
The warmer it is, the higher the rate of transpiration because the water particles have more energy to evaporate and diffusion out of the stomata
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How does a decrease in air movement(when its less windy) affect the rate of Transpiration?
air around a leaf is still,water vapour just surrounds leaf & doesn't move away.This means there's a higher concentration of water particles outside the leaf as well as inside it-diffusion doesn't happen as quickly-rate of transpiration decreases
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What happens to the rate of transpiration when the air around the plant is windy?
If its windy then transpiration is faster cos the water vapour gets swept away, maintaining a low concentration of water in the air outside the leaf
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Does the rate of transpiration increase in humid conditions?
no, when its humid the rate of transpiration decreases-so transpiration is faster in dry conditions
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What are 3 ways plants have adapted to reduce water loss?
1)Leaves usually have waxy cuticle covering upper epidermis-keeps upper surface of leaf waterproof 2)Most stomata are found-lower surface of leaf-more dark & cooler-slows rate of diffusion of water out of leaf
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What are 3 ways plants have adapted to reduce water loss?continued...
The bigger the stomata & more stomata a leaf has, more water plants loose. So, plants in hot climates really need to conserve water-they've fewer & smaller stomata on the underside of leaf & no stomata on upper epidermis
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What type of cells control the opening and closing of the stomata?
Guard cells control the opening and closing of the stomata
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When do stomata automatically close?
When water supplies are low the stomata close automatically.Also, they're light-sensitive so open for photosynthesis during the day and close at night
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What adaptations make guard cells efficient for their job?
Guard cells have a special kidney shape which opens when it becomes turgid and closes when it becomes flaccid.The thin outer walls & thickened inner walls make this opening closing function work properly.
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Why do stomata open?
Stomata open to allow gases in and out for photosynthesis
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What is the singular for Stomata?
Stoma
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Card 2

Front

Do sieve tubes elements have a nucleus?

Back

No, so they have a companion cell to carry out its living function as well as its own

Card 3

Front

What substances do Phloem vessels transport?

Back

Preview of the front of card 3

Card 4

Front

What directions do substances flow in Phloem vessels?What is the special name of this?

Back

Preview of the front of card 4

Card 5

Front

What are Xylem vessels made of?

Back

Preview of the front of card 5
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