Describing the external and internal structure of a leaf

BIOLOGY GRADE 10 External and Internal Structure of a Leaf Describing the external and internal structure of a leaf

Leaf Structure

All leaves have the same basic structure – a midrib, an edge, veins and a petiole.
The main function of a leaf is to carry out photosynthesis, which provides the plant with the food it needs to survive.
Plants provide food for all life on the planet.

The structure of a leaf has adaptations so that it can carry out photosynthesis effectively.

A leaf needs:

a way to transport water to the leaf, and glucose to other parts of the plant
a way to exchange carbon dioxide and oxygen
the ability to absorb light energy efficiently

What are the features of a leaf?

Photosynthesis is a vital process that occurs in the leaves of a plant. During photosynthesis, the leaves use light energy to convert carbon dioxide and water into oxygen and glucose. The glucose acts as a source of food for the plant.

Leaves have several features that play an important role in photosynthesis:

A large surface area helps the leaf to absorb as much sunlight as possible.
Leaves are thin, minimising the distance for carbon dioxide to travel into leaf cells.
A midrib provides strength throughout the leaf, keeping it upright and sturdy in the wind.
Chlorophyll is the green pigment that absorbs sunlight.
Veins transport water and glucose around the plant.
The petiole attaches the leaf to the plant’s stem.
Stomata are tiny openings or pores, which allow carbon dioxide to enter and oxygen to exit the leaf.

Feature	Function
Large surface area	Maximise light absorption
Thin	Short distance for carbon dioxide to diffuse into leaf cells
Cuticle	A waxy waterproof layer which reduces water loss, it is transparent to allow light through the leaf

Absorbing light energy

Light absorption happens in the palisade mesophyll tissue of the leaf. Palisade cells are column-shaped and packed with many chloroplasts. They are arranged closely together so that a lot of light energy can be absorbed. Cross section of a leaf showing Waxy cuticle, Upper epidermis, Palisade mesophyll, Spongy mesophyll containing Air space. The Lower epidermis contains Guard cells with chloroplasts surrounding Stoma.