Transpiration

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Biology Lab Report
(F.4)
* Objective: To study the transpiration of a leafy shoot using the bubble potometer

* Materials and apparatus:
* Bubble potometer
* Leafy shoot
* Scissors
* Basin with water
* A fan
* Plumbing tape

* Method:
Normal Condition:
1. The bubble potometer was filled with water.
2. The stem of a leafy shoot was cut under water.
3. The bottom of the stem was wrapped by plumbing tape.
4. The stem was fitted onto the photometer under the water. 5. The plant was allowed to equilibrate for 5 minutes.
6. The initial position was recorded when it was stable.
7. Its position was again recorded after 10 minutes.
Greater Air Movement (Under a fan):
1. The bubble potometer was filled with water.
2. The stem of a leafy shoot was cut under water.
3. The bottom of the stem was wrapped by plumbing tape.
4. The stem was fitted onto the photometer under the water. 5. The set up was placed under a fan.
6. The plant was allowed to equilibrate for 5 minutes.
7. The initial position was recorded when it was stable.
8. Its position was again recorded after 10 minutes.

* Results:
Distance moved by water level (cm)|
Normal Condition| Greater Air Movement|
0.8| 0.8|
0.95| 1.05|
1.7| 1.75|
2| |
2.1| |
3| |
Average: 1.76| Average:1.2|

* Discussion:
* Why is it necessary to allow the plant 5 minutes to equilibrate before taking readings? It is to make sure that the plant adopts the environment. To leave the reading position stable so as to decrease the reading error. * Compare and explain the transpiration rate of the leafy shoot when it is in still air and under a fan. In real, the rate of transpiration under greater air movement should be higher than that in normal condition. Under greater air movement, water vapour coming out of the leaf.is blown away rapidly. This maintains a high concentration gradient of water...
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