Stomata and Transpiration

Question 1

What are stomata?

Answer 1

Tiny pores that are mostly found on the lower surface of leaves

Question 2

State the function of stomata.

Answer 2

To allow for gases to diffuse in and out of the leaves of a plant

Question 3

What controls whether the stomata remain open or closed?

Answer 3

Guard cells

Question 4

Describe how guard cells control whether stomata remain open or closed.

Answer 4

• When the guard cells are turgid, the stomata are open
• When the guard cells are flaccid, the stomata are closed

Question 5

List three factors that affect the rate of transpiration in a plant.

Answer 5

• Light intensity
• Air flow
• Temperature

Question 6

(Exam-style question)

Answer 6

Question 7

Explain how air flow affects the rate of transpiration.

Answer 7

• The better the air flow around a leaf, the greater the rate of transpiration
• This is because water vapour is swept away, so a low concentration of water vapour outside the leaf is maintained
• This causes diffusion to happen quickly as the water vapour moves from a high to low concentration

Question 8

Explain how temperature affects the rate of transpiration.

Answer 8

• The warmer it is, the faster the rate of transpiration
• This is because the water particles have more energy to evaporate and diffuse out of the stomata

Question 9

Name a piece of apparatus used to estimate the rate of transpiration.

Answer 9

Potometer

Question 10

Describe a method to estimate the rate of transpiration in a plant.

Answer 10

• Set up apparatus as shown, and record starting position of air bubble
• Start stopwatch and record distance moved by the bubble per unit of time - calculating the speed of air bubble gives an estimate of transpiration rate