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Biology practical

Transpiration and wind speed

Set up a potometer with a leafy shoot, time an air bubble along its scale with a fan at different distances, and plot how the rate of water uptake changes.

What you will do

  1. 01Cut the stem of a leafy shoot under water and fit it into the potometer, then seal the joint with petroleum jelly.
  2. 02Use the reservoir to bring the air bubble back to the start of the scale.
  3. 03Put the fan a distance d from the shoot, switch it on, and wait a minute for the shoot to settle.
  4. 04Read the position of the bubble, time two minutes, and read it again.
  5. 05Repeat for at least five distances from about 20 cm to 100 cm. Plot the rate against d and draw a smooth curve.