Gas exchange in a leaf
- Created by: Laura
- Created on: 02-05-14 15:49
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- Gas exchange in a leaf
- As oxygen and carbon dioxide are produced in a plant it reduces the need to exchange with the external air
- Structure of a plant leaf and gas exchange
- No living cell in a plant is far from the external air and therefore a source of oxygen and carbon dioxide
- Diffusion takes place in air which makes it more rapid than in water
- There is a short, fast diffusion pathway. Also a plant has a very large surface area compared with its volume
- Gas exchanges through the surface of a leaf via diffusion so no transport system is needed
- Thin, flat shape provides a large surface area
- Many, small pores called stomata mostly in the lower epidermis
- Numerous interconnecting air-spaces that occur throughout the mesophyll
- Stomata
- Miniature pores which occur mainly, but not exclusively, on the leaves, especially the underside.
- Each stomata is surrounded by a pair of special cells called guard cells.
- These cells can open and close the stomatal pore. In this way they can control the rate of gaseous exchange. This is important because terrestrial organisms lose water by evaporation
- They completely or partially close stomata at times when water loss would be excessive
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