The skin of a plant

The idea

The epidermis, a tightly packed single layer of flat cells, is the plant's protective outer layer; its waxy cuticle reduces water loss and resists injury and parasites, and root hairs increase its surface area for absorption.

A raincoat for a leaf

A leaf stands in hot sunshine all day. Water inside it could easily dry out.

What would protect it best?

• A waxy, tightly packed outer layer
• A layer with big gaps between cells
• No outer layer at all

Cuticle and root hairs

Make the cuticle of the leaf thicker. Then look at a root and switch on its root hairs.

Epidermis: the protective tissue

The epidermis is the outermost layer of the plant body. It is a tightly packed, single layer of flat, rectangular cells. It protects the plant from mechanical injury, water loss, harmful microorganisms and extreme conditions. Its cells are covered with a waxy layer of cutin called the cuticle.

In plants of a very dry habitat the cuticle may be thick, to reduce water loss. The cuticle also protects against injury and invasion by parasites. In roots, root hairs arise from epidermal cells and increase the surface area for absorption of water and minerals.

Notes

The epidermis is a tightly packed single layer that protects the plant. Its waxy cuticle reduces water loss. Root hairs increase the surface area for absorption.

Check yourself

The epidermis is…

A plant lives in a very dry habitat. Its cuticle is probably…

Why do root hairs help a plant?

• many layers of loosely packed round cells. That is not the epidermis.
• a layer of dividing cells at the root tip. That is meristematic tissue.
• a tightly packed single layer of flat, rectangular cells — correct. Yes.
• missing, to let water out. A missing cuticle would waste water.
• thick, to reduce water loss — correct. Yes.
• made of dead cells that fall off. The cuticle is a waxy layer of cutin.
• They make food by photosynthesis. Root hairs absorb; leaves make food.
• They stop water from entering the root. They help water to enter.
• They increase the surface area for absorbing water and minerals — correct. Yes.