ZIMSEC O Level Combined Science Notes: Investigating water loss in plants
Aim: To determine how plants loose their water
Materials: plants or branches from plants, weighing balance, containers, water, oil/Vaseline.
- Select three small, leafy branches from a plant. Make sure the branches are roughly the same size.
- Cut the branches and put the stems in water immediately
- Half fill three containers with water.
- Place one stem with all its leaves into a container labeled A
- Place another branch with all the leaves removed in a container labeled B
- Place a third branch in with the stem covered in vaseline/oil into a container labeled C
- Place a thin film of oil over the surface of the water in each container.
- Weigh each container and record the masses in a table
- Weigh the containers at regular intervals over the course of a few days
- Calculate the percentage loss in weight for each branches
- The branch in container A losses the most water followed by the plant in container labeled C.
- There is hardly any change in the mass of container B
- This is because water is lost via the leaves through the process of transpiration
- The plants in A and B have all their leaves so they loose the most water
- This is because 95% of the water that enters into plants is lost through the leaves via the process of transpiration
- Very little water is lost through the stems because there is hardly any difference between the water lost by plants A and C
- The oil layer minimises water loss through the process of evaporation
- Most water is lost through the leaves
- This is called transpiration
- Very little water is lost through the stems
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