Prepare a leaf cross-section slide and use a virtual microscope to discover how leaf tissues help a plant absorb light and exchange gases.

What can pupils see inside a leaf that they cannot see from its surface? In this KS3 biology practical, pupils prepare a wet mount, bring a thin leaf section into focus and use visible clues to identify its layers. They then draw what they see and explain how each structure helps the leaf function.

What pupils do

• Prepare the slide. Add a drop of water, place the thin leaf section in the drop and slowly lower the coverslip at an angle to reduce trapped air bubbles.
• Focus the microscope. Start with the 4× objective and use coarse focus to sharpen the cell outlines. Centre the specimen before switching to the 10× objective, then use fine focus to see the chloroplasts.
• Identify the tissues. Look for the flat, transparent cells of the upper epidermis, the tall palisade cells packed with chloroplasts and the irregular spongy mesophyll cells with air spaces between them.
• Record and explain. Complete an observation table with the name, appearance and function of each part. Use it to label a scientific drawing and explain how light reaches the palisade cells and how gases move through the leaf.

Where it fits in your scheme of work

Use this practical alongside White Rose Science Year 8 Plants for the Adaptations of the leaf lesson. It also supports Exploring Science, including Exploring Science International, and AQA Activate lessons on leaf structure, photosynthesis and gas exchange.

Classroom use

Project the specimen and pause before revealing the labels. Ask pupils to sketch two neighbouring layers and identify each from one visible clue. “The cells are tall and packed with green chloroplasts” gives pupils evidence for identifying the palisade layer and a starting point for explaining its role in photosynthesis.