7.1.3

Investigating Transpiration

Test yourself

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:

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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.
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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.
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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.
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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.
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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.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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