Investigating Transpiration
Biology: Cambridge International A Level, topic 7.1.3
Investigating Transpiration Rate
The rate of transpiration can be influenced by a number of factors. An experiment can be set up using a potometer to estimate transpiration rate. The steps involved are:
Apparatus
1) Assemble the potometer
- A potometer is a piece of equipment that is used to estimate the volume of water taken up by a plant in a given time.
- The potometer is filled with water and a cutting of a shoot is placed inside.
- The shoot must be cut and placed into the potometer while underwater to ensure no air enters the xylem.
2) Form the air bubble
- Remove the end of the capillary tube from the water beaker.
- Wait for a bubble of air to form in the capillary tube.
- Place the capillary tube back into the water.
- The air bubble is used to record the volume of water used by the shoot.
3) Record bubble movement
- Mark the starting position of the air bubble.
- Use a stopwatch to record the distance moved by the air bubble in a given time period.
4) Calculate transpiration rate
- Calculate the rate of movement of the bubble per hour.
- The rate of bubble movement is equal to the transpiration rate.
5) Change the variable
- The experiment can be repeated by changing a different variable each time (e.g. temperature or light).
- It is important to only change one variable at one time and to keep all other conditions constant.
- Changing one variable allows the effects of an environmental factor on transpiration rate to be compared.
Test yourself on Investigating Transpiration
Steps Involved in Investigating Transpiration Rate
Which of the following statements about transpiration rate are true?
How is the transpiration rate calculated?