A secondary compound is not a part of the plants -

Options

A. Defence against herbivores
B. Normal metabolism
C. Evolution
D. embryology

Answer

To solve the question "A secondary compound is not a part of the plants," we need to analyze the concept of secondary compounds (or secondary metabolites) in plants and determine which option does not fit into this category.

### Step-by-Step Solution:

1. **Understand Secondary Compounds**:
- Secondary compounds, also known as secondary metabolites, are organic compounds that are not directly involved in the normal growth, development, or reproduction of plants. Examples include alkaloids, terpenes, and phenolics.

2. **Identify the Role of Secondary Compounds**:
- These compounds serve various functions, primarily related to the plant's defense mechanisms against herbivores and pathogens. They can deter feeding or inhibit the growth of pests.

3. **Examine the Options**:
- The question likely provides multiple-choice options. We need to evaluate each option to determine which one does not relate to secondary compounds.

4. **Analyze Each Option**:
- **Option 1: Defense mechanism against herbivores**: This is correct as secondary metabolites often serve this purpose.
- **Option 2: Normal metabolism**: This is the key option. Secondary metabolites are not part of the normal metabolic processes of plants; they are produced in response to specific stimuli.
- **Option 3: Evolution**: Secondary metabolites can play a role in the evolution of plant species, but they are not a direct part of the plant's structure or function.
- **Option 4: Hemorrhology**: This term relates to the study of blood and is not relevant to plant secondary metabolites.

5. **Determine the Correct Answer**:
- Based on the analysis, the option that states "normal metabolism" is correct as it indicates that secondary compounds are not part of the normal metabolic processes in plants.

### Final Answer:
The correct answer is **normal metabolism**.

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