Weight potometer experiment

Weight potometer experiment

1. In a weight potometer the mass of water lost is measured by recording the loss in mass over a period of time

   • Four leafy shoots are used.
     • A: one left untreated
     • B: top surface covered in vaseline
     • C: lower surface covered in vaseline
     • D: Leaves removed from shoot
     • E: CONTROL/ no shoot

2. Once the shoots are in the water, put cooking oil carefully onto the surface of the water

3. Then weigh the tubes

   • and weigh them again after 48hrs

4. RESULTS

   • Tube A lost the most mass
     • No stomata were covered so there was nothing to prevent water loss so the water loss was greatest
   • Tube D lost the least mass (not including E)
     • There were no stomata for the water to evaporate out of so water loss was minimised and the plant did not lose much mass
   • The difference between tubes B and C...
     • Tube B lost more mass than C because the lower surface of the leaf contains more stomata, so as it is covered in C it will conserve more weight and have a lower change in mass.
   • Why was oil put over the surface of the water in the flasks?
     • To prevent any water evaporating from the flask, not the stomata
   • What is the function of tube E?
     • Control - to prove that it was the varying leaves affecting their mass
   • What must be kept constant?
     • Volume of water, temperature of water, species of leaf, light intensity, humidity