Leaf Cross Section Diagram IGCSE Biology 0610

Leaf Cross Section Diagram: Layers and Adaptations

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

Key diagram

A leaf cross section shows the upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, stomata, guard cells and vascular bundle. Each layer is adapted for efficient photosynthesis and gas exchange.

The leaf cross section is one of the most commonly examined diagrams in IGCSE Biology. Students must be able to label each layer, explain how its structure is adapted for photosynthesis or gas exchange, and describe the movement of gases through the leaf.

Drawing the layers in order

From top to bottom, draw: (1) a thin line for the waxy cuticle, which reduces water loss; (2) a single row of flat cells for the upper epidermis, which is transparent to let light through; (3) a layer of tall, tightly packed cells for the palisade mesophyll, packed with chloroplasts; (4) a layer of irregularly shaped cells with air spaces for the spongy mesophyll; (5) a single row of cells for the lower epidermis with gaps for stomata flanked by guard cells.

Adaptations for photosynthesis

The palisade mesophyll is the main site of photosynthesis. These cells are tall and packed with chloroplasts near the top of the leaf, closest to the light source. The upper epidermis is transparent and thin, allowing maximum light to reach the palisade layer. The vascular bundle (midrib) runs through the spongy mesophyll, with xylem bringing water and phloem transporting sugars away.

Gas exchange through the leaf

Carbon dioxide enters through open stomata on the lower epidermis, diffuses through the air spaces in the spongy mesophyll and reaches the palisade cells. Oxygen produced during photosynthesis diffuses out along the same route. The air spaces provide a large internal surface area for gas exchange.

Guard cells control the opening and closing of stomata. When turgid, they curve apart and the stoma opens. When flaccid, they close the stoma, reducing water loss.

Vascular bundle in the leaf

Within the midrib, xylem vessels transport water and dissolved mineral ions into the leaf. Phloem carries dissolved sugars (sucrose) away from the leaf to other parts of the plant. In a cross-section diagram, the xylem is typically drawn on top (towards the upper surface) and phloem below.

Label checklist

Check these labels are present and correctly positioned before finishing your drawing.

✓ Waxy cuticle
✓ Upper epidermis
✓ Palisade mesophyll
✓ Spongy mesophyll
✓ Lower epidermis
✓ Stomata
✓ Guard cells
✓ Air spaces
✓ Vascular bundle (xylem and phloem)

Try a diagram question (3 marks)

Explain how the palisade mesophyll layer is adapted for photosynthesis. [3]

Show the answer and marking guidance

Cells are tall and tightly packed, positioned near the upper surface of the leaf to receive maximum light.
Cells contain many chloroplasts, which absorb light energy for photosynthesis.
Chloroplasts contain chlorophyll, the pigment that absorbs light energy.

Original Cambridge-style practice written for this site.

Common diagram mistakes

Check these against your own drawing before moving on.

Labelling the waxy cuticle as the upper epidermis.
Drawing stomata on the upper surface instead of the lower epidermis.
Forgetting air spaces in the spongy mesophyll layer.
Not showing the palisade cells as taller than the spongy mesophyll cells.
Omitting the vascular bundle entirely.