When dilute iodine solution is poured over a decolourised green leaf, a blue-black colour is produced. This shows that the green leaf contains :

Options

A. glucose
B. cellulose
C. starch
D. sucrose

Answer

**Step-by-Step Solution:**

1. **Understanding the Experiment**: When a dilute iodine solution is poured over a decolorized green leaf, a blue-black color appears. This indicates a chemical reaction is taking place.

2. **Identifying the Leaf's Condition**: The term "decolorized" means that the green pigment (chlorophyll) has been removed from the leaf. This is usually done to ensure that any color change observed is due to the iodine solution and not the chlorophyll.

3. **Role of Iodine Solution**: Iodine is known to react with starch. When iodine comes into contact with starch, it produces a characteristic blue-black color. This is a well-known test for the presence of starch.

4. **Photosynthesis and Starch Formation**: During photosynthesis, plants convert carbon dioxide and water into glucose using sunlight. The glucose produced can be converted into starch for storage. Therefore, if the leaf is green (indicating it has chlorophyll), it is capable of photosynthesis and can produce starch.

5. **Conclusion**: Since the blue-black color appears when iodine is applied to the decolorized green leaf, it indicates that starch is present in the leaf. Thus, the green leaf contains starch.

**Final Answer**: The green leaf contains starch.

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