AS CH2.2 Adaptions for gas exchange (plants)

Question 1

Why do plants require oxygen?

Answer 1

For respiration

Question 2

Why do plants require CO2?

Answer 2

For photosynthesis

Question 3

What type of transport allows plants to obtain carbon dioxide through the leaves?

Answer 3

Diffusion

Question 4

What structures do plants have to make gas exchange more efficient?

Answer 4

• Waxy cuticle covers the leafs surface to reduce water loss and diffusion of gases
• Stomata opens during the day to allow gas exchange, and closes at night or dry conditions to reduce water loss

Question 5

Why are the size of the stomata controlled by the guard cells that surround it?

Answer 5

To reduce water loss via transpiration

Question 6

What is the stomatal opening mechanism?

Answer 6

1. Guard cells photosynthesize producing ATP
2. Energy released from ATP is used to actively transport potassium ions into guard cells
3. Triggers insoluble starch to be converted into soluble malate ions
4. Water potential of guard cells are lowered so water enters the cells by osmosis
5. Guard cells expand, its outer wall stretches more than the thinner wall, creating a pore between guard cells
6. The reverse happens at night