Allelopathy is due to secretion of

Options

A. pheromone
B. toxin
C. nectar
D. vitamins

Answer

### Step-by-Step Solution:

1. **Understanding Allelopathy**:
- Allelopathy is a biological phenomenon where one organism releases chemicals into the environment that can affect the growth, survival, and reproduction of other organisms.

2. **Identifying Allelochemicals**:
- The chemicals responsible for allelopathy are known as allelochemicals. These substances can inhibit the growth of neighboring plants and organisms.

3. **Examples of Allelopathy**:
- A well-known example of allelopathy is the black walnut tree, which releases a chemical called juglone. This chemical is toxic to many plants, including tomatoes, peppers, eggplants, and potatoes.

4. **Mechanism of Action**:
- The allelochemicals can be released through various parts of the plant, such as leaves, roots, or decaying plant material. These chemicals can inhibit germination and growth of other plants in the vicinity.

5. **Conclusion**:
- Based on the understanding of allelopathy and the examples provided, we conclude that allelopathy is primarily due to the secretion of toxins.

### Final Answer:
Allelopathy is due to the secretion of **toxins**.

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