Investigating Temperature & Wind Speed (Cambridge (CIE) IGCSE Biology): Revision Note

Investigating the effect of temperature & wind speed on transpiration rate

Method

• Dry the leaves of the shoot (wet leaves will affect the results)

• Cut a shoot underwater to prevent air entering the xylem and place in tube

• Set up the apparatus as shown in the diagram and make sure it is airtight, using vaseline to seal any gaps

• Remove the capillary tube from the beaker of water to allow a single air bubble to form and place the tube back into the water

• Set up the environmental factor being investigated

• Allow the plant to acclimatise to the new environment for 5 minutes

• Record the starting location of the air bubble

• Leave for a set period of time

• Record the end location of air bubble

• Change the wind speed or temperature (only one - whichever factor is being investigated)

• Reset the bubble by opening the tap below the reservoir

• Repeat the experiment

• The further the bubble travels in the same time period, the faster the rate of water uptake (used as an estimate of transpiration rate)

• Environmental factors can be investigated in the following ways:

  • Temperature: temperature of room (cold room and warm room)

    • As temperature increases, the rate of transpiration also increases (opens in a new tab)

  • Wind speed: use an electric fan to mimic different wind speeds

    • As wind speed increases, the rate of transpiration also increases