Gaseous exchange in plants
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- Created by: sophiee96
- Created on: 02-03-13 10:21
During the day what processes do plants carry out?
Respiration and photosynthesis
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How do plants get the carbon dioxide they need for photosynthesis?
Diffusion through leaves and some is gained through respiration
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What processes do plants carry out at night?
Respiration only
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What is the plants organ of gaseous exchange?
The leaf
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What four things enable gaseous exchange to take place efficiently in the leaf?
It's thin and flat with a large surface area, the spongy mesophyll tissue allows diffusion of gases, plant tissues are permeated by air spaces and stomatal pores also permit gas exchange
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Once inside the leaf the gases in the sub-stomatal air chambers do what?
Diffuse through the intercellular spaces between the spongy mesophyll cells and into the cells
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What does the direction of diffusion depend on?
Environmental conditions and the requirements of the plant
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What seven adaptations does the leaf have to ensure efficient absorption of light
Large surface area, thin, transparent cuticle + epidermis, elongated palisade cells densely arranged in layers, chloroplasts can rotate + move, intercellular air spaces in spongy mesophyll + chloroplasts arranged so long axes perpendicular to surface
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Why is important leaves have a large surface area?
To capture as much sunlight as possible
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Why is it important leaves are thin?
So light can penetrate lower layers of cells
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Why is it important the cuticle and epidermis are transparent?
So light can penetrate the mesophyll
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How are chloroplasts arranged in the palisade cells?
With their long axes perpendicular to the surface
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What is the benefits of chloroplasts being able to rotate and move within the mesophyll cells?
They are able to arrange themselves in the best position for efficient absorption of light
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What does the intercellular air spaces in spongy mesophyll allow?
Carbon dioxide to diffuse to the cells and oxygen to diffuse away
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What are stomata?
Pores located on the lower surface of a leaf, through which gases diffuse
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What is a cuticle?
The waxy covering on a leaf which reduces water loss
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What is each stomata pore bound by?
Two guard cells
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What two things make guard cells unusual?
They contain chloroplasts and have unevenly thickened walls
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Is the inner wall of the guard cell thicker or thinner?
Thicker
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What do the stomata control?
The exchange of gases between the atmosphere and the internal tissues of the leaf
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What are the diffusion gradients in and out of the leaf maintained by?
Mitochondria carrying out respiration and chloroplasts carrying out photosynthesis
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How do plants lose water and what is the name given to this process?
By evaporation through the stomata called transpiration
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What does sunlight on the upper surface of the leaf increase?
Evaporation
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Why are stomata on the lower surfaces of the leaf?
To reduce water loss
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What is the benefit of a waxy cuticle on the upper surface of a leaf?
To reduce water loss
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Why do stomata close at night?
To reduce water loss, the light intensity is insufficient for photosynthesis
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What happens when water enter the guard cells?
The swell and the pore opens
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What happens when water leaves the guard cells?
They become flaccid and the pore closes
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When the chloroplasts in the guard cells photosynthesise, what do they produce?
ATP
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What does ATP prove energy for? (when the stoma is opening)
Active transport to take up potassium ions from surrounding epidermal cells into the guard cells
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Stored starch is converted to what? (when the stoma is opening)
Malate
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What happens when the water potential of the guard cell is lowered? (when the stoma is opening)
Water enters by osmosis
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Why do the guard cells become turgid and curve apart? (when the stoma is opening)
Because the outer walls are thinner than the inner walls
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Other cards in this set
Card 2
Front
How do plants get the carbon dioxide they need for photosynthesis?
Back
Diffusion through leaves and some is gained through respiration
Card 3
Front
What processes do plants carry out at night?
Back
Card 4
Front
What is the plants organ of gaseous exchange?
Back
Card 5
Front
What four things enable gaseous exchange to take place efficiently in the leaf?
Back
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