Transpiration — return questions

1. define

What is transpiration?

2. state

Complete the sentences about how water leaves a leaf.

Water … from the surfaces of the

… cells into the air spaces.

The water vapour then … out of the leaf

through the ….

3. calculate

In a potometer the bubble moved 36 mm in 3 minutes. What is the rate of water uptake?

Rate of water uptake: ______________ unit ________

4. explain

Supplement. Identify two features of a leaf's structure that let it lose water vapour quickly, and explain how each one helps.

Feature 1 and how it helps

Feature 2 and how it helps

5. describe

How does the rate of transpiration change as the temperature of the air goes up (within a moderate range)?

Circle one answer.

• It increases
• It stays the same
• It decreases

6. explain

Supplement. Match each change to the reason it changes the rate of transpiration.

Write the number of the matching option.

1. The concentration gradient is shallow, so water vapour diffuses out more slowly
2. Water molecules have more kinetic energy, so they evaporate and diffuse faster
3. Water vapour is carried away from the leaf, keeping the concentration gradient steep

• Higher temperature: ______
• Higher wind speed: ______
• Higher humidity: ______

7. state

You test the effect of temperature on a leafy shoot with a potometer. State two things you would keep the same.

8. explain

Supplement. Explain what is meant by the transpiration pull.

9. state

Supplement. Complete the sentences about wilting.

A plant wilts when it loses water by … faster

than its roots … water.

Its cells become …, so they no longer hold the leaves and stems up.

10. identify

Supplement. What holds the water in a xylem vessel together as a column?

Circle one answer.

• The lignin that lines the walls of the xylem
• Forces of attraction between water molecules
• Valves between the cells of the xylem vessels
• Sugar dissolved in the water, making it sticky