Some experiments were carried out using Croton sp. plants to understand the process of photosynthesis. It was observed that the leaves of the plant exposed to light for longer duration accumulated more starch. However, due to presence of pre-formed starch in the leaves, it was difficult to find the net productivity on a fixed exposure to light source. Therefore, it was necessary to obtain starch free leaves in the plant before starting the experiment.
After a period of illumination, the leaves were boiled in alcohol to make them colourless. Which of the following could be used to test the end product stored in the leaves?

Options

A. Cobalt chloride paper
B. Litmus paper
C. Iodine solution
D. Copper sulphate solution

Explanation

To solve the question regarding the testing of the end product stored in the leaves of Croton sp. plants after conducting photosynthesis experiments, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Experiment**: The experiment involves Croton sp. plants where the leaves are exposed to light to observe starch accumulation. However, pre-formed starch in the leaves can interfere with the results, so starch-free leaves are required for accurate measurement.

2. **Preparation of Leaves**: After exposing the leaves to light, they are boiled in alcohol. This process removes chlorophyll and makes the leaves colorless, allowing for a clearer test for starch.

3. **Identifying the Test for Starch**: To determine the presence of starch in the leaves, we need to use a specific reagent that reacts with starch.

4. **Evaluating the Options**:
- **Cobalt Chloride Paper**: This paper is used to test for humidity, not for starch.
- **Litmus Paper**: This paper is used to test whether a solution is acidic or basic, not for starch.
- **Iodine Solution**: This is the correct reagent for testing starch. When iodine is added to a starch solution, it turns blue-black, indicating the presence of starch.
- **Copper Sulfate Solution**: This solution is used to test for the presence of water, not for starch.

5. **Conclusion**: Based on the evaluation of the options, the correct answer is iodine solution, as it is used to test for the presence of starch.

### Final Answer:
The end product stored in the leaves can be tested using **iodine solution**.

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