3.3 Plants

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  • Created by: mayacm456
  • Created on: 13-03-23 17:34
What are four factors that affect transpiration rate?
Light intensity, temperature, humidity and wind
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1) What effect does light intensity have on transpiration rate?
2) Why?
lighter = faster transpiration rate. This is because
the stomata open when it gets light, so CO2 can diffuse into the leaf for photosynthesis. When it’s dark the stomata are usually closed, so there’s little transpiration.
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1) What effect does temperature have on transpiration rate?
2) Why?
higher temp. = faster transpiration rate b/c warmer water molecules have more energy so they evaporate from the cells inside the leaf faster. This increases the water potential
gradient btwn inside and outside of the leaf, making water diffuse out of the
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1) What effect does humidity have on transpiration rate?
2) Why?
lower humidity = faster transpiration rate.
If the air around the plant is dry,
the water potential gradient between the leaf and the air is increased, which increases transpiration
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1) What effect does wind have on transpiration rate?
2) Why?
windier=faster transpiration rate b/c lots of air movement blows away water molecules from around the stomata. This increases the water potential gradient which increases the rate of transpiration.
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What is transpiration a consequence of?
gas exchange
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How is transpiration a consequence of gas exchange?
plant needs to open stomata to let in CO2 so that it can produce glucose (by photosynthesis).
This also lets water out — there’s a higher concentration of water inside the leaf than in air outside, so water moves out of leaf down the water potential gradi
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How is the xylem not having end walls a good adaptation?
it makes an interrupted tube that allows water to pass up through the middle easily
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1) Are xylem vessel cells dead or alive?
2) What part of the cell do they not have?
The cells are dead, so they contain no cytoplasm
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What are xylem walls thickened with?
Lignin
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What does lignin do? (2)
supports xylem vessels and stops them collapsing inwards
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What ways can lignin be deposited in xylem walls? (2)
in a spiral or distinct rings
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the amount of lignin increases....
as the cell gets older
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How do water and ions move into and out of the vessels?
through small pits in the walls where there's no lignin
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What four parts are in phloem tissue?
phloem fibres, phloem parenchyma, sieve tube elements and companion cells
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What two parts of phloem tissue are the most important for transport?
sieve tube elements and companion cells
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What do the end walls in sieve tube elements have and why?
they have lots of holes to allow solutes to pass through
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1) Are sieve tube elements living or dead?
2) They are joined end to end to form.......
They are living cells that form the tube for
transporting solutes through the plant. They are joined end to end to form sieve tubes.
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What is unusual for sieve tube elements given that they are living cells?
Sieve tube elements have no
nucleus, a very thin layer of cytoplasm and few organelles
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Why can't sieve tube elements survive on their own?
they lack a nucleus and other organelles
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There is a companion cell for.....
every sieve tube element
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1) What do companion cells do?
2) Give an example
Companion cells carry out the living functions for both themselves and their sieve cells. Eg they provide the energy for the active transport of solutes
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1) What is the Casparian *****?
2) Where is it found?
A waxy ***** found in the cell walls in the endodermis cell layer.
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Because of the Casparian *****, what pathway does the water have to take?
the symplast pathway
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Why is the Casparian ***** useful?
Because it means the water has to go through a cell membrane. Cell membranes are
partially permeable and are able to control whether or not substances in the water get through
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Other cards in this set

Card 2

Front

1) What effect does light intensity have on transpiration rate?
2) Why?

Back

lighter = faster transpiration rate. This is because
the stomata open when it gets light, so CO2 can diffuse into the leaf for photosynthesis. When it’s dark the stomata are usually closed, so there’s little transpiration.

Card 3

Front

1) What effect does temperature have on transpiration rate?
2) Why?

Back

Preview of the front of card 3

Card 4

Front

1) What effect does humidity have on transpiration rate?
2) Why?

Back

Preview of the front of card 4

Card 5

Front

1) What effect does wind have on transpiration rate?
2) Why?

Back

Preview of the front of card 5
View more cards

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