B4.8 Evaporation and transpiration

Question 1

What is the purpose of the stomata?

Answer 1

To allow air into the leaves

Question 2

How does the stomata maintain a steep concentration gradient?

Answer 2

CO2 diffuses into the air spaces and then into the cells down a concentration gradient - at the same time oxygen produced by photosynthesis is removed from the leaf by diffusion into the surrounding air

Question 3

What controls the size of the stomata?

Answer 3

Guard cells

Question 4

What is transpiration?

Answer 4

When the stomata are open - plants lose water vapour through them as well - water vapour evaporates from the cells lining the air spaces and pass out the leaf through the stomata by diffusion - known as transipiration

Question 5

What is the transpiration stream?

Answer 5

More water is pulled up the xylem to take the place of the water that has evaporated

Question 6

What is the transpiration stream driven by?

Answer 6

The loss of water by evaporation out of the stomata