BioCoach Activity

Concept 4: Dermal Tissues

The dermal tissue system protects the soft tissues of plants and controls interactions with the plants' surroundings.

The epidermis is a dermal tissue that is usually a single layer of cells covering the younger parts of a plant. It secretes a waxy layer called the cuticle that inhibits water loss.

Some of the many types of cells in the epidermis are shown below.

Epidermis from onion

Most epidermal cells lack chloroplasts.

Epidermis from onion

Guard cells contain chloroplasts and regulate gas exchange between the inside of the leaf and the surrounding air.

Epidermal hairs lower water loss by decreasing the flow of air over the plant surface, which in turn, slows the loss of water from the plant.

Glandular hairs prevent herbivory by storing substances that are harmful to insects.

Root hairs increase water uptake by increasing the surface area of the cell.

In older stems and roots, the epidermis may be replaced by the periderm, which provides protection while permitting gas exchange.

The outer layer of periderm, cork tissue, is composed of dead cells whose cell walls are impregnated with a waxy material, suberin.