Lesson 1, Topic 1
In Progress

THE PROCESS OF EVAPOTRANSPIRATION

KEY WORDS: Evapotranspiration Transpire Transparent Transpiration Evaporation Evaporates.

Activity: Breath out or blow air onto a transparent surface: What Do You Observe? : You will observe that you blow air onto the transparent surface, water vapour from your mouth forms on the surface of the glass. The water vapour forming on the surface of the glass shows that as we respire (breath out), we breath out water vapour.

Just as we release water vapour when we respire (breath out), plants also transpire (breath out) through a process called evapotranspiration.

How Do Plants Transpire? Watch this video to observe how plants transpire: How Do Plants Breathe? [Fun-tastic Photosynthesis] – YouTube

Activity: 1.2 To show how plants transpire(breathe out) 

Materials needed: A young potted plant, a transparent plastic wrap bag and rope or rubber band. 

steps to follow: 

work in groups 

.Set-up the potted plant and make sure there is no water on the leaves. 

2. Cover the plant with the transparent plastic bag up to the stem as shown in the picture . 

3. Tie the end of the plastic bag with the rubber 

4. Leave the set- up for three hours and observe what happens. 

Observation and discussion After three hours, you will observe 

that the plastic bag looks foggy. 

Meaning that water has gathered on the surface of the leaves and the inner surface of the plastic wrap bag. 

This happens because, water in the soil changes to gas as the ground 

Plant covered with transparent plastic wrap bag 

surface warms up. The water then Evaporation: travels through the roots to the stem. The Water travels through the roots, to the stem and to the leaves.  

Water vapour escapes from the leaves (Transpiration).  Let us study an example of an experiment below.

What is evapotranspiration?: Evapotranspiration is a word gotten from two words These words are: 1. Evaporation and 2. Transpiration. 1. Evaporation: It is the process by which liquid changes to water vapour. When the sun shines, the land and the water bodies such as rivers, and lakes get heated. As they are heated some of the rises into the atmosphere. When this happens we say water has evaporated. Evaporation also takes place in plants. This happens when the liquid of the plants loose water through a process called Transpiration.

2. Transpiration: It is the process by which plants lose water from the leaves into the atmosphere.

Plants take in water from the soil. As they take in water from the soil, the water moves from the roots through the stem and to the leaves. Some of the the water in the water in the leaves evaporates into the atmosphere.