Biology · 6.1 Photosynthesis · Paper 5/6 practical
Leaf Starch Test. Prove the requirements.
Starch is the stored product of photosynthesis, so testing a leaf for starch shows whether it has photosynthesised. Decolourise the leaf and add iodine, then use destarched plants to prove light, carbon dioxide and chlorophyll are needed.
0610 Topic 6.1 — Photosynthesis
iodine starch test
Paper 5/6 — Practical
Step 1 of 4
Investigation
Testing
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Result
complete the test…
The 4 steps
- Boil the leaf in water — kills it & breaks the cell walls.
- Boil in ethanol (in a water bath, flame off) — removes the green chlorophyll.
- Dip in hot water — softens the brittle leaf.
- Add iodine solution — blue-black shows starch is present.
📋 Why each step / investigation
⚠ Safety & precautions
- Ethanol is flammable — turn the Bunsen off and heat the ethanol in a water bath, never directly.
- Destarch the plant first (48 h in the dark) so any starch found must be newly made.
- Always run a control and change only one factor (light, CO₂ or chlorophyll).
🎯 Syllabus reference (0610)
- 6.1 Photosynthesis — investigate the need for light, carbon dioxide and chlorophyll using starch tests (including variegated leaves); the iodine test for starch.