Gas exchange in plants Flashcards
1
Q
Which gases to plants take in and out?
A
- Take in oxygen for respiration
- Take in carbon dioxide for photosynthesis
- Oxygen diffuses out from photosynthesis
- Carbon dioxide produced in respiration diffuses out
2
Q
Similarities between gas exchange in plants and insects?
A
- No living cell is far from external air, so can obtain O2 and CO2
- Diffusion takes place in the gas phase (more rapid than in air)
3
Q
Describe the diffusion pathway
A
Short and fast diffusion pathway
4
Q
Describe the surface area to volume ratio of a leaf
A
- Very large, so gases move in and out by diffusion
5
Q
How are leaves adapted for gaseous exchange?
A
- Thin flat shape with large surface area to volume ratio
- Many small pores, called stomata, mostly in the lower epidermis
- Numerous interconnecting air-spaces in the mesophyll
6
Q
What are stomata?
A
- Stomata are minute pores which occur mainly on the leaves underside
7
Q
Describe the stomata
A
- Each stoma is surrounded by a pair of guard cells, which open and close it
8
Q
Why do guard cells control the stomata?
A
- To control the rate of gaseous exchange
- Closing the stomata at times when water loss might be excessive
9
Q
When does oxygen diffuse into the leaf?
A
- When photosynthesis is not occurring eg at night, as it is constantly being used in respiration. Carbon dioxide diffuses out
10
Q
When does carbon dioxide diffuse into the leaf?
A
- When photosynthesis is taking place carbon dioxide diffuses into the leaf, oxygen diffuses out
