To solve the question of finding the odd one out with respect to the part of the plant used for food storage under unfavorable conditions, we will analyze each of the given options: potato, colocasia, ginger, and turnip.
### Step-by-Step Solution:
1. **Identify the Plant Parts Used for Food Storage**:
- **Potato**: The potato is a modified stem known as a tuber. Tubers are specialized for storing food, primarily starch, which the plant can utilize during unfavorable conditions.
- **Colocasia**: In colocasia, the modified part is a corm, which is also a type of stem. Corms store carbohydrates and serve as a food reserve for the plant.
- **Ginger**: Ginger has a modified stem called a rhizome. Rhizomes are underground stems that store nutrients and can sprout new plants, serving as a food storage organ.
- **Turnip**: The turnip is a modified root, specifically a taproot. Taproots store food in the form of carbohydrates and are the main storage organ for the plant.
2. **Comparison of the Options**:
- Potato, colocasia, and ginger all have modified stems (tuber, corm, and rhizome, respectively) that are used for food storage.
- Turnip, on the other hand, has a modified root (taproot) that serves the same purpose.
3. **Determine the Odd One Out**:
- Since potato, colocasia, and ginger all involve modified stems for food storage, while turnip involves a modified root, the odd one out is clearly **turnip**.
### Conclusion:
The correct answer is **turnip**, as it is the only option that uses a modified root for food storage, while the others use modified stems.
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