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Unlike animals, plants don’t have a pump to push around fluid through their bodies. Water can move through the xylem because of transpiration.

Year 9 iGCSE - Biology



Transpiration is the loss of water from a plant’s leaves. The water lost creates a difference in concentrations.

This causes an uptake of water from the roots.

The constant flow of water from the roots, through the xylem and out of the leaves is called the transpiration stream.

As water diffuses from the soil into the root hairs through osmosis.

Before the water enters the xylem it must travel through cells, until it reaches the centre of the root. Once inside the xylem, it travels up the plant.

The stomata on the surface of leaves allow carbon dioxide to diffuse in for photosynthesis. As well as water lost to the environment.

Guard cells around the stomata allow the plant to control the amount of CO2 and H2O lost.

Quick Questions

1. Define transpiration

2. What is a transpiration stream

3. Explain the roles of the Xylem and Phloem

Quick Questions

1. Define Osmosis

2. Explain the role of the Stomata

3. How do the guard cells help the plant.

4. Where are the guard cells located


2. Circle the following

a. Increasing humidity increases/decreases rate of transpiration.

b. Increasing temperature increases/decreases rate of transpiration.

c. Increasing light intensity increases/decreases rate of transpiration.

d. Increasing wind increases/decreases rate of transpiration.

3. What adaptations do plants have to reduce water loss?

4. What effects rate of transpiration?

5. Explain why temperature effects rate of transpiration?

6. Explain why wind effects rate of transpiration?

7. Where are stomata found and what do they do?

8. Describe a simple experiment to measure transpiration