The structure of a leaf

The leaves are the organ for photosynthesis. It is where photosynthesis takes place. The structures of leaves are adapted for efficient photosynthesis as shown in the table below.

Adaptation Function
Large surface area Most leaves are broad and so have a large surface area allowing them to absorb more light.
A thin shape A thin shape means a short distance for carbon dioxide to diffuse in and oxygen to diffuse out easily.
Chlorophyll This chemical gives the leaves their green colour and transfers light energy to chemical energy.
Veins Networks of veins support the structure of the leaf and transport substances to and from the cells in the leaf.
Stomata These are small holes on the underside of the leaf that allow gases to diffuse in and out.



The cellular structure of a leaf

Layer & Adaptation Function
The cuticle is a waxy, waterproof layer which cuts down the water lost by evaporation and protects against parasitic fungi.
Upper Epidermis:
A single layer of cells that are transparent and contain no chloroplast allowing light to pass straight through.
Palisade Layer:
Contains chloroplasts
This layer is made up of palisade cells which contain chloroplasts. This is where most of the photosynthesis takes place.
Vein: The vein contains tubes called the xylem and phloem. The xylem brings water and salts to the leaf for photosynthesis. The phloem transports the dissolved foods away.
Spongy Layer:
Irregularly shaped cells with air spaces between them.
This layer consists of irregularly shaped cells with large air spaces between them allowing gas exchange (diffusion) between stomata and photosynthesising cells.
Lower Epidermis:
Contains lots of tiny holes.
This layer contains lots of tiny holes or pores called stomata at regular intervals. These allow gases to diffuse in and out of the leaf.