`C_(4)` cycle was discovered in

Options

A. Groundnut
B. Sugarcane
C. Chrysanthemum
D. Apple.

Answer

To answer the question regarding the discovery of the C4 cycle, follow these steps:

### Step-by-Step Solution:

1. **Understanding the C4 Cycle**: The C4 cycle, also known as the Hatch-Slack pathway, is a photosynthetic process that occurs in certain plants, allowing them to efficiently fix carbon dioxide in high temperatures and low carbon dioxide concentrations.

2. **Historical Context**: The C4 cycle was first studied in detail by researchers Kotschak and Hart, who were investigating the carbon fixation process in plants.

3. **Identifying the Plant**: Among the options provided (groundnut, sugarcane, chrysanthemum, apple), sugarcane is widely recognized as one of the primary plants where the C4 cycle was discovered and studied.

4. **Key Discoveries**: Kotschak and Hart supplied carbon dioxide to the leaves of sugarcane and identified that the first stable compound formed was oxaloacetic acid, a 4-carbon compound. This was crucial in establishing the C4 pathway.

5. **Further Research**: The detailed studies conducted by Hatch and Slack in 1966 further elucidated the mechanisms of the C4 cycle, leading to its naming as the Hatch-Slack pathway.

6. **Conclusion**: Based on the historical findings and research, the correct answer to the question is that the C4 cycle was discovered in sugarcane.

### Final Answer:
The C4 cycle was discovered in **sugarcane**.

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