Gas Exchange In Plants

Question 1

Describe the structural adaptations of gas exchange structures in plants.

Answer 1

1. Many mesophyll cells lining the intercellular air spaces in the leaf provide a large surface area for gas exchange
2. The cell wall, cell membrane and leaves are thin so provide a shirt diffusion pathway
3. Respiration and photosynthesis maintain diffusion gradients by using and producing carbon dioxide and oxygen
4. Leaves contain many stomata which increases rate of gas exchange

Question 2

What are xerophytes?

Answer 2

Plants which live in extreme conditions so have extra structural adaptations to prevent water loss from the stomata

Question 3

Describe the structural adaptations of the leaves of xerophytes.

Answer 3

1. Thick waterproof cuticle which makes leaves impermeable to water so reduces evaporation.
2. Sunken stomata so water molecules build up around the stomata so that the water potential gradient is lowered between the leaf and air which reduces evaporation from the stomata.
3. Fewer stomata so less area for evaporation
4. Small leaves so lower surface are for evaporation
5. Hair on leaves which traps water vapour so reduces the water potential gradient which reduces the rate of evaporation
6. Rolled leaves which causes a build up of water on the surface reducing the water potential gradient thus reducing the rate of evaporation

Question 4

Describe the other structural adaptation xerophytes have.

Answer 4

1. Swollen stems which act as water reservoirs for the plant
2. Extensive root networks which take advantage of rain fall and water found lower down in the soil