# To Study the Transpiration Rate of a Plant (Gou Qi) by Using the Bubble Photometer.

Topics: Leaf, Water, Evaporation Pages: 5 (1073 words) Published: May 1, 2012
Biology 1st Group Lab Report

Objective:
- To study the transpiration rate of a plant (Gou Qi) by using the bubble photometer.

Assumption:
- The rate of transpiration is equal to the rate of water uptake of the plant(Gou Qi) .

Theory:

|Independent Variable |Dependent Variable |Controlled Variable | |The environmental conditions: |　Rate of water uptake by transpiration of the |Time taken for the movement of the air bubble | |Normal |plant(Gou Qi) |(5MIN -> 10MIN) | |Higher light intensity | |Type of the plant(Gou Qi). | |Greater air movement | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

How can we measure the dependent variable?

We measure the dependent variable according to the formula below: Rate = the distance move(final–initial)
Time
Unit : cm/ min

How can we vary the independent variable?

We can vary the environmental conditions by:
Normal: Under room temperature, normal light intensity, with natural wind Higher Light Intensity: Put a table lamp 50cm far from the plant (Gou qi). Greater air movement: Put a fan 100cm far from the plant (Gou qi). Materials and Apparatus:

◆ The plant (Gou qi) x1
◆ A basin of water
◆ Scissor
◆ Bubble photometer x1
➢ U shape tube
➢ Rubber tubing
➢ Syringe
◆ Rubber Ban
◆ Stop watch
◆ Ruler
◆ Fan

Procedure of setting and testing the experiment:
1. Wrapped the stem of the plant(Gou qi) by using the thread-seal tape. 2. The bubble photometer was filled with water.
3. The stem of the plant(Gou qi) was cut under water. The stem was fitted onto the rubber tubing on the photometer under water. 4. An air bubble was introduced at the end of the capillary tube. (Push the water inside the syringe to reset the position of the air bubble) 5. Wait for the bubble to move to the graduated part of the capillary tube for 5 minutes. 6. The initial position/water level (cm) of the air bubble was recorded. 7. The final position/water level (cm) of the air bubble was recorded again after 5 minutes. 8. Repeat step 4 to step7 with new environmental conditions (higher light intensity and greater air movement). Result:

A table showing distance moved by water level(cm)
|　 |Distance moved by water level (cm)...
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