Practical B6

Use a potometer (bubble and weight potometer) to investigate the factors affecting the rate of water uptake by a plant.

Bubble potometer procedure

  1. Set up a bubble potometer (under water and using petroleum jelly).
  2. Note the position of the bubble.
  3. Leave for a period of time.
  4. Note the new position of the bubble.
  5. Calculate the rate of bubble movement over this period of time.
  6. Reset the apparatus.
  7. Repeat steps 2-6 under the same conditions to increase the reliability of the experiment.
  8. Adjust the environmental conditions.
  9. Repeat steps 2-7 for the new environmental condition.
  10. Record results in a table.

Weight potometer procedure

  1. Set up a weight potometer.
  2. Measure the mass of the container and plant.
  3. Leave for a period of time.
  4. Measure the new mass of the container and shoot.
  5. Calculate the rate of change of mass over this period of time.
  6. Repeat steps 1-5 under the same conditions to increase the reliability of the experiment.
  7. Adjust the environmental conditions.
  8. Repeat steps 1-6 for the new environmental condition.
  9. Record results in a table.

Washing line method

Use the washing line method to investigate the factors affecting the rate of water loss from leaves.

Procedure

  1. Remove a number of leaves from a plant.
  2. Smear petroleum jelly over the cut stalks to make them waterproof.
  3. Measure the mass of each leaf.
  4. Using paperclips hang the leaves on a line of string (held up by 2 retort stands).
  5. If investigating the effect of temperature on water loss by a leaf, hang half of the leaves at a high temperature and the other half at a low temperature.
  6. After a period of time, find the new mass of each leaf.
  7. Calculate the average loss of mass at each temperature.
Move on to Video
next