Questions
2
The upper surface is covered with a layer of wax that stops water passing through. The
underside has stomata, which are openings leading to the air spaces inside a leaf.
Water vapour can diffuse out from the air spaces, through the stomata.
Think like a scientist: Investigating transpiration
1
Whether the leaves were exposed to the air or not.
2
The soil was covered in both. Learners should also have tried to keep the temperature
the same for both plants and to use two plants of the same size. They should have
ensured there was the same quantity of water in the soil in each pot and that the light
intensity was the same.
3
Answers will depend on the learners’ results. They are likely to find that the loss of mass
was much greater in the plant that did not have a bag covering its leaves.
4
Water vapour was lost from the leaves of the plant that did not have its leaves covered,
by transpiration. The water vapour that was lost from the leaves of the other plant was
trapped inside the bag and could not escape.
Think like a scientist: Which side of a leaf loses most water?
1
This will depend on the learners’ results. The most likely sequence (in increasing ability
to conserve water) is: leaf with no petroleum jelly; with petroleum jelly on upper surface
only; with petroleum jelly on lower surface only; with petroleum jelly on both surfaces.
2
The upper surface has few (or no) stomata, but the underside has stomata, through
which water vapour can diffuse out from the air spaces.
3
It is unlikely that the two leaves would lose exactly the same mass. The leaves were
probably different masses to start with and contained different quantities of water. One
leaf may have been in a slightly draughtier place than another. Learners may make
other suggestions, depending on what happened in their experiment.