Transpiration — final check

1. calculate

A potometer bubble's left edge was at 250 mm when the clock started. After 2 minutes the same edge was at 220 mm. Work out (a) the distance the bubble moved and (b) the rate of water uptake.

(a) Distance moved: ______________ unit ________

(b) Rate of water uptake: ______________ unit ________

2. define / describe

(a) Describe what is meant by transpiration. (b) Describe how water leaves a leaf, from the mesophyll cells to the air outside.

(a) Transpiration

(b) How water leaves a leaf

3. explain

Supplement. Explain how (a) the air spaces between the mesophyll cells and (b) the number and size of the stomata affect the rate of water vapour loss from a leaf.

(a) The air spaces

(b) The number and size of stomata

4. describe / explain

A pupil measured the rate of water uptake by one leafy shoot at four air temperatures. (a) Describe the effect of temperature on the rate. (b) Explain why the pupil used the same shoot at every temperature.

(a) The effect of temperature

(b) Why the same shoot

5. explain

Supplement. Explain the effect on the rate of transpiration of (a) a higher temperature and (b) a higher humidity.

(a) Higher temperature

(b) Higher humidity

6. explain

Supplement. Explain why a plant loses water faster on a windy day than on a still day.

7. explain

Supplement. Explain how water moves up the xylem from the roots to the leaves of a tall plant. In your answer, say (a) what happens to water in the leaves, (b) how this moves water up the xylem, and (c) what holds the water together.

(a) In the leaves

(b) How water moves up

(c) What holds the water together

8. explain

Supplement. A pot plant on a sunny windowsill wilts on a hot day. After it is watered, it stands upright again within an hour. Explain (a) why it wilted and (b) how watering makes it upright again.

(a) Why it wilted

(b) How watering helps

9. explain

Supplement. Explain why an air bubble in a xylem vessel stops water moving up that vessel.