Opium is extracted from flowers/fruits of white poppy plants.

Explanation

**Step-by-Step Solution:**

1. **Identify the Source of Opium**: Understand that opium is derived from the white poppy plant, scientifically known as *Papaver somniferum*.

2. **Determine the Part of the Plant Used**: Recognize that opium is harvested from the latex of the plant. This latex is produced when the plant's immature seed pods (fruits) are scored or cut.

3. **Understand the Harvesting Process**: The harvesting occurs typically 5 to 10 days after the petals of the flowers have fallen off. At this stage, the seed pods are still immature, and the latex can be collected.

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