Potometer

Question 1

What are potometers used for

Answer 1

estimate the rate of transpiration of a plant​.

Question 2

How do potometers estimate the rate of transpiration of a plant​

Answer 2

measure water uptake by the plant

Question 3

Assumption of potometers

Answer 3

water uptake by the plant is directly related to water loss by the leaves.

Question 4

Limitations of the potometers

Answer 4

Not all the water taken up by the plant is used for transpiration– for example some is used in cells to maintain turgidity.

● Some water is used in photosynthesis

● The plant is dying once you cut off its roots – it may take up less water as it begins to
die.

Question 5

Method to use a potometers

Answer 5

1. Cut a shoot underwater to prevent air from entering the xylem. Cut it at a slant to increase the surface area available for water uptake.
2. Assemble the potometer in water and insert the shoot under water, again to prevent air from entering
   3. Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water.
3. Check the apparatus is watertight and airtight, using screws or petroleum jelly.
4. Dry the leaves
5. Allow time for the plant to acclimatise and then shut the tap.
6. 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 water.
7. Record the starting position of the air bubble.
8. Start a stopwatch and record the distance moved by the bubble at regular time intervals, e.g. every 30 mins.