Structure of a leaf

 

Structure of a leaf

 

Photosynthesis

Photosynthesis is how leaves make food from light, using chlorophyll to turn water and carbon dioxide into oxygen and glucose.

The photosynthesis equation is:

 

Carbon dioxide + water → glucose + oxygen

Leaves are adapted for photosynthesis in several ways.

 

Plant adaptation	Function
Broad leaves	Maximize sunlight absorption
Thin leaves	Shorten gas diffusion distance
Network of tubes	Transport water, minerals and glucose (or food)
Lots of chloroplasts	Trap sun energy with chlorophyll
Stomata	Allow gas exchange in and out of leaf
Guard cells	Control stomata opening and closing
Midrib	Strengthen and support the leaf
Petiole	Connect the leaf to the stem

 

 

Light

Leaves have a large surface area and a waxy layer to absorb and protect light. The upper part has palisade cells with many chloroplasts and a tall shape to catch more light.

 

Carbon dioxide

Leaves take in carbon dioxide from the air through stomata, small holes on the underside. Guard cells adjust the stomata size to prevent water loss. The lower part has spongy cells with air spaces to let carbon dioxide reach other cells and oxygen leave.

 

Water

Leaves get water from the roots through tubes. The roots have root hair cells that stick out into the soil and have a big surface area and thin walls to absorb water easily.

Root cells have no chloroplasts, as they are in the dark and cannot do photosynthesis.

 

🍃 Knowledge Check: Leaf Structure

How well do you know the internal anatomy of a leaf? Test yourself below!

1. Which layer of the leaf contains cells packed with the most chloroplasts?

• Spongy mesophyll
• Palisade mesophyll
• Upper epidermis

2. What is the main purpose of the air spaces in the spongy mesophyll?

• To make the leaf light enough to float
• To allow gases to diffuse through the leaf easily
• To store water for the plant

3. Through which structures does carbon dioxide enter the leaf?

• Xylem vessels
• Stomata
• Waxy cuticle

4. What happens to the stomata when a plant is short of water?

• They open wider to catch rain
• They close to prevent further water loss
• They turn into palisade cells

5. Which tissue is responsible for transporting water to the leaf cells?

• Phloem
• Xylem
• Epidermis

Check Your Answers

1. Palisade mesophyll (Positioned at the top to maximise light absorption).
2. Gas diffusion (Allows CO2 to reach cells and O2 to leave them).
3. Stomata (Small pores usually found on the underside of the leaf).
4. They close (Guard cells become flaccid to seal the pore and save water).
5. Xylem (Transports water and minerals from the roots).

 

Summary:

 

• Leaves are vital plant organs that make food by photosynthesis.
• Leaves come in various sizes, shapes and colours to suit photosynthesis.