This resource provides practice for the skills of microscope use learnt in KS3 science and applied at KS4. Students learn about stomata in the context of leaf structure and their role in photosynthesis and control of water loss. It also asks students to consider why there are more stomata on the lower surface of the leaf than on the upper surface.

Tradescantia zebrina works well for this protocol because the green stomata stand out against the purple underside of the leaf, making them easy for students to identify. Tradescantia zebrina can be bought from garden centres or online and is a plant that is easy to care for and take cuttings from. For more information see the teacher and technician notes.

The written extension question asks students to think about the relationship between atmospheric carbon dioxide levels and density of stomata.