secondary growth occurs due to activity of

Options

A. cork cambium
B. vascular cambium
C. intercalary meristem
D. both A and B

Answer

To answer the question "secondary growth occurs due to activity of," we need to identify the correct types of meristematic tissues involved in secondary growth. Here’s a step-by-step solution:

### Step 1: Understand Secondary Growth
Secondary growth refers to the increase in thickness or girth of a plant, which is primarily seen in woody plants. This growth is different from primary growth, which increases the length of the plant.

**Hint:** Secondary growth is mainly responsible for the increase in the diameter of stems and roots.

### Step 2: Identify the Types of Cambium
There are two main types of cambium involved in secondary growth:
1. **Cork Cambium (Phellogen)**: This is a meristematic tissue that produces the outer protective layer of the plant, known as cork. It is responsible for the formation of the periderm, which replaces the epidermis in older stems and roots.

2. **Vascular Cambium**: This is another meristematic tissue that forms between the xylem and phloem. It is responsible for producing secondary vascular tissues, which include secondary xylem (wood) and secondary phloem.

**Hint:** Think about what tissues are responsible for the thickening of stems and roots.

### Step 3: Differentiate Between Types of Meristematic Tissues
- **Cork Cambium**: Involved in the formation of cork and protective tissues.
- **Vascular Cambium**: Involved in the formation of vascular tissues (xylem and phloem).

**Hint:** Remember that both cork cambium and vascular cambium contribute to the secondary growth process.

### Step 4: Consider Other Types of Meristematic Tissues
- **Intercalary Meristem**: This type of meristem is found at the base of leaves or internodes and is involved in primary growth, not secondary growth. It helps in elongation rather than thickening.

**Hint:** Focus on the types of meristematic tissues that contribute to thickness rather than length.

### Step 5: Conclusion
Based on the above analysis, secondary growth occurs due to the activity of both cork cambium and vascular cambium. Therefore, the correct answer to the question is both A (Cork Cambium) and B (Vascular Cambium).

**Final Answer:** Secondary growth occurs due to the activity of cork cambium and vascular cambium.

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