Plant Organisation

What is the function of the stomata?

Tiny pores that open and close to allow gases (CO₂ in, O₂ out) to move in and out for photosynthesis and respiration, and control water loss through transpiration.

Why do stomata open and close?

To control gas exchange and reduce water loss; open when the plant has water, close when water is scarce.

What is the epidermis?

The outer protective layer of cells on leaves, stems, and roots that protects the plant and reduces water loss.

What is the purpose of the waxy cuticle?

A waterproof layer covering the epidermis that reduces water loss by evaporation.

How does the waxy cuticle reduce water loss?

By sealing the leaf surface, stopping water evaporating through the epidermis cells, except where stomata are present.

What is the palisade mesophyll?

A layer of tightly packed cells under the upper epidermis containing many chloroplasts, where most photosynthesis happens.

What is the spongy mesophyll?

A layer of loosely packed cells with air spaces that help gases (CO₂, O₂, water vapor) move through the leaf.

What role do the air spaces in the spongy mesophyll play?

They allow carbon dioxide to diffuse easily to palisade cells and help oxygen and water vapor move out through the stomata.