What is the sequence of tissue from outside to inside in periderm ?

Options

A. Phellem - phelloderm - phellogen
B. Phellem - phellogen - phelloderm
C. Phellogen - phellem - phelloderm
D. Phelloderm - phellogen-phellem

Answer

To determine the sequence of tissues from outside to inside in the periderm, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Periderm**:
- The periderm is a protective tissue that replaces the epidermis in stems and roots of perennial plants during secondary growth.

2. **Identifying the Layers**:
- The periderm consists of three distinct layers: phellem, phellogen, and phelloderm.

3. **Outer Layer - Phellem**:
- The outermost layer of the periderm is called **phellem** (also known as cork).
- It is a protective layer that is dead at maturity and is air-filled.

4. **Middle Layer - Phellogen**:
- The middle layer is known as **phellogen** (or cork cambium).
- This layer is a meristematic tissue that produces the phellem towards the outside and the phelloderm towards the inside.

5. **Innermost Layer - Phelloderm**:
- The innermost layer is called **phelloderm**.
- It consists of living parenchyma cells and is located just inside the phellogen.

6. **Final Sequence**:
- Therefore, the correct sequence of tissues from outside to inside in the periderm is:
- **Phellem (outermost) → Phellogen (middle) → Phelloderm (innermost)**.

### Summary of the Sequence:
- **Phellem** (outer layer)
- **Phellogen** (middle layer)
- **Phelloderm** (innermost layer)