Potometer

• Potometer


  A special piece of apparatus used to measure water uptake by a plant
• Water uptake by the plant

  Related to water loss from the leaves (transpiration)
• The water taken up by a plant is not all lost through transpiration (e.g. some is used up in photosynthesis and some may be lost from parts of the potometer that aren't sealed)
• How to use a potometer

  1. Cut a shoot underwater to prevent air from entering the xylem

  2. Cut there are air bubbles in the apparatus or it at a slant to increase the surface area available for water uptake

  3. Assemble the potometer in water and insert the shoot under water, so no air can enter

  4. Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water

  5. Check that the apparatus is watertight and airtight

  6. Dry the leaves, allow time for the shoot to acclimatise and then shut the tap

  7. Remove the end of the capillary tube from the beaker of water until one air bubble has formed, then put the end of the tube back into the water

  8. Record the starting position of the air bubble

  9. Start a stopwatch and record the distance moved by the bubble per unit time, e.g. per hour

  10. Keep the conditions constant throughout the experiment, e.g. the temperature and air humidity
• Calculating the speed of air bubble movement

  Allows you to measure water uptake