The key difference between the epidermis and periderm lies in their location and the developmental stage of the plant they cover. Both are dermal tissues forming an outer layer of a plant, but they are not present at the same time nor on the same plant parts.
Epidermis vs. Periderm: Key Differences
| Feature | Epidermis | Periderm |
|---|---|---|
| Location | Outer layer of leaves, young stems, and young roots. | Outer layer of roots and stems that have undergone secondary growth. |
| Development | Primary growth tissue. | Secondary growth tissue. |
| Stage of Plant | Present in young, non-woody plants. | Appears in older, woody plants. |
Detailed Explanation
Epidermis
The epidermis is the outermost layer of cells in young plants and its parts, like:
- Leaves: Protects the leaf tissue from water loss and mechanical damage.
- Young Stems: Forms a protective barrier as the stem is developing.
- Young Roots: Facilitates water and nutrient absorption from the soil.
It is the first line of defense for the plant, and it's typically a single layer of cells. The epidermis can also have specialized cells like stomata (for gas exchange) and trichomes (for protection).
Periderm
The periderm, on the other hand, develops in older plants that have undergone secondary growth. It is a complex tissue that replaces the epidermis. Specifically, the periderm appears in:
- Older Stems: In woody stems, it forms the bark that protects the plant.
- Older Roots: It provides a barrier to protect the internal root tissues as they thicken.
The periderm is comprised of multiple layers, including cork cells, which are dead at maturity and have thick, water-repellent walls. This makes the periderm more robust than the epidermis, which is important for long-term protection in older plants.
Key Takeaway from the Reference:
Both the epidermis and periderm are dermal tissues that make up an outer part of plants. The epidermis is the outer layer of leaves, young stems, and young leaves, whereas the periderm is the outer layer of roots and stems that have undergone secondary growth.
