Plant organisation

Plant structure

Flowering plants have a basic structure:

A diagram showing the structure of a plant.

Leaves, stems and roots are organs consisting of different types of tissues Plant leaves are the main organ for photosynthesis.

Functions of leaves

The function of a leaf is photosynthesis. Leaves are the source of all of food on Earth.

Diagram of a plant leaf

Leaves are adapted in several ways to help them perform their function.

Features of leaves

AdaptionPurpose
Large surface areaTo absorb more light
ThinShort distance for carbon dioxide to diffuse into leaf cells
ChlorophyllAbsorbs sunlight to transfer energy into chemicals
Network of veinsTo support the leaf and transport water and sugars
StomataAllow carbon dioxide to diffuse into the leaf and oxygen to diffuse out

Inside the leaf

Diagram showing how a leaf is structured and what happens during photosynthesis

The internal structure of the leaf is also adapted to promote efficient photosynthesis:

Structure of leaves

AdaptionPurpose
Epidermis is thin and transparentTo allow more light to reach the palisade cells
Thin cuticle made of waxTo protect the leaf from infection and prevent water loss without blocking out light
Palisade cell layer at top of leafTo absorb more light and increase the rate of photosynthesis
Spongy layerAir spaces allow carbon dioxide to diffuse through the leaf
Palisade cells contain many chloroplastsTo absorb all the available light
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