Page 95 - Biology Form Two

Biology for Secondary Schools

Activity 4.4: Demonstrate transpiration Types of transpiration
There are three types of transpiration,
Materials as explained below:
Potted plant, knife, polythene bag, Stomatal transpiration
weighing scale, and rubber bands
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This occurs through the stomata on the
Procedure leaves. It accounts for approximately
1. Set up the experiment, as shown 90% of the water loss in plants.
in Figure 4.18.
Cuticular transpiration
This occurs through the cuticle of
Potted plant leaves. The cuticle is a waxy layer that
covers the surface of leaves. A thick

Rubber band cuticle prevents excessive loss of water.
Lenticular transpiration
Polythene bag This occurs through the lenticels.
Lenticels are pores found on the bark
of stems or roots in woody plants.

Factors affecting the rate of
Figure 4.18: Experimental set-up to transpiration
demonstrate transpiration The rate of transpiration in plants is

affected by plant features as well as
2. Weigh the potted plant and record environmental factors.
its weight.

3. Leave the set-up in location where Plant features
it can easily access the sunlight Plant features that affect the rate of
transpiration include the following:
4. Weigh the potted plant after 7 days (i) The size of the leaves: A large
and then calculate the change in leaf has more stomata than a small
weight. leaf. Therefore, plants with large

5. Write a short report of what you leaves lose more water than those
have observed. with smaller leaves.

Question (ii) An extensive root system: Plants
What caused the change in the weight that have extensive roots absorb
of the potted plant after 7 days? more water and can therefore lose
more water than those with fewer
roots.

Student’s Book - Form Two 89

05/10/2024 15:36:35
BIOLOGY FORM 2 NEW.indd 89 05/10/2024 15:36:35
BIOLOGY FORM 2 NEW.indd 89