Explain how the investigation could indicate that chlorophyll is needed for photosynthesis. Include the role of chlorophyll in your explanation.

Chlorophyll is the green pigment found in the chloroplasts of leaves. It gives leaves their green colour and aids in the process of photosynthesis by trapping light needed for it.
The variegated leaf experiment is used to investigate that chlorophyll is needed for photosynthesis:
- Take a variegated leaf
- Take another leaf and don’t do anything to it (it’s going to act as a control plant)
- Place the leaves in different Petri dishes containing moist cotton wool
- Leave the Petri dishes in the sun for about 6 hours
- Carry out the iodine test for starch on both leaves by placing 2-3 drops of iodine solution on both leaves
- You’ll find that the control turns dark blue/black while the variegated leaf is stained yellow on the white parts but dark blue/black on the green parts.
The blue/black color shows that starch is present in the leaf meaning photosynthesis took place. The yellow color is just the color of iodine solution.
The white parts do not contain starch because there is no chlorophyll to trap sunlight needed in the process of photosynthesis. This shows that chlorophyll is necessary in the process of photosynthesis.