Excessive elongation of plants and poor development of leaves when they were grown in darkness is called

Options

A. Foolish seedling disease
B. Bolting
C. Embolism
D. Etiolation

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a specific phenomenon that occurs in plants when they are grown in darkness, characterized by excessive elongation and poor leaf development.

2. **Identifying Key Terms**: The key terms in the question are "excessive elongation," "poor development of leaves," and "grown in darkness."

3. **Analyzing the Options**:
- **Fully Seedling Disease**: This is a disease caused by a fungus that affects certain plants, particularly rice. It does not relate to the conditions described in the question.
- **Bolting**: This refers to the premature flowering of plants, which is not relevant to the growth conditions mentioned.
- **Embolism**: This involves the blockage of xylem vessels by air bubbles, which is unrelated to the growth conditions in darkness.
- **Etiolation**: This is a process that occurs in plants grown in low light conditions, leading to elongated stems and underdeveloped leaves.

4. **Conclusion**: Based on the analysis, the correct term that describes the excessive elongation of plants and poor leaf development when grown in darkness is **etiolation**.

### Final Answer:
The phenomenon described is called **etiolation**.

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