Experiment 1: Testing for starch in food (bread, potato etc) and in a leaf.
|Materials Tested||Colour change||Labelled diagram (or photographs)|
|Leaf||only the green part of the leaf turns dark blue.|
EXPERIMENT 2: Is light needed for photosynthesis?
In the experiment above, the middle part of the leaf is covered by a piece of aluminium foil while the stalk is still attached to the plant. The plant is left under the sunlight to allow the photosynthesis process to continue to take place and glucose is made in the uncovered part of the leaf. This glucose is converted into starch and stored in the leaf. (Glucose is a simple molecule and these molecules combined to make large complex molecules called starch).
What is happening to the covered part of the plant?
Glass is transparent and allows light energy to travel through it. However, aluminium is opaque and does not allow light to travel through it. This part of leaf covered by aluminium will not receive the needed sunlight and the leaf will not be able to carry the photosynthesis process. This means the covered part of the leaf will not be able to make starch while the uncovered part of the leaf continues to make starch.
What is photosynthesis?
Photosynthesis refers to the process where plant takes in the carbon dioxide produced by all breathing organisms and reintroduces oxygen into the atmosphere. Photosynthesis is the process used by plants, algae and certain bacteria to convert energy from sunlight and turn it into chemical energy.
Chemical equation of photosynthesis:
- Why part of the leaf is covered with a piece of aluminium foil?
- Why was the plant left in the sun?
- What happens when the leaf is tested for the presence of starch?
- Explain why a part of the leaf covered by the foil will not show the presence of starch?
- How does this experiment support the idea that sunlight is needed for photosynthesis?