Gas Exchange: Plants Flashcards
What is the relationship between photosynthesis and respiration in plants?
The oxygen produced by photosynthesis can be used by respiring cells and the carbon dioxide produced by respiration can be used in photosynthesis.
Why must gas exchange occur with external air aswell as those produced in respiration or photosynthesis?
Because the rates of photosynthesis change throughout the day based on conditions such as light level.
What happens to the rate of photosynthesis compared to respiration in plants at night?
It is lower than respiration.
When is external gas exchange necessary?
When the rates of photosynthesis and respiration are different.
When are the rates of photosynthesis and respiration the same?
They are only the same for a very small time, (maybe a few minutes).
How are the leaves adapted for rapid diffusion of gases?
1) Many stomata - short diffusion distance.
2) Many interconnecting air spaces - in spongy mesophyll so gases are in contact with mesophyll.
3) Large surface area of mesophyll cells - allows rapid diffusion.
At what part of the plant does gas exchange occur in mostly?
The leaves.
What happens to the rate of photosynthesis compared to respiration in plants in the day?
It is higher than respiration.
What are stomata?
Small pores found on the underside of a leaf.
What surrounds the stomata?
Guard cells.
Where can you find stomata?
They are located in the lower epidermis.
What is the function of the stomata?
Their openings control the rate of gas exchange and limit the water loss through transpiration.
What controls the stomatal openings?
Guard cells.
What is the relationship between the cuticle and water loss?
The waxier the cuticle, the less water escapes.
What is the function of a thick, waxy cuticle?
It forms a waterproof barrier to reduce water loss.
What adaptations do the plants have to limit water loss?
- Thick, waxy cuticle.
- Rolling up the leaves.
- Hairy leaves.
- Stomata in pits and grooves.
- Reduced leaf SA:V.
What does a reduced SA:V ratio mean for water loss?
The slower the rate of diffusion, thus the rate of water loss.
How does rolling up the leaves aid water retention?
The stoma are found in the lower epidermis, rolling the leaves helps to trap a region of still air full of water vapour and thus a very high water potential, causing no water potential gradient meaning less water loss.
How is the SA:V ratio reduced by the leaf?
This is achieved through small circular leaves rather than broad, flat leaves.
How do hairy leaves help water loss?
The hairy leaves trap still, moist air next to the leaf surface, this reduces water potential gradient which reduces water loss.
How do stomata in pits and grooves help water loss?
This traps still, moist air outside the leaf which again reduces water potential gradient.
Where is the main gas exchange surface within the leaf?
The surface of mesophyll cells.
What key feature of gas exchange is held in the lower epidermis?
Stomata.
What happens to the guard cells when the cell is losing too much water?
They get dehydrated, lose water and come flaccid, closing the pore.
