Measuring and calibrating in microscopy: Measuring stomatal density

In this activity, developed to provide a purpose to practising measuring and calibrating skills, students explore what happens to stomatal density as leaves grow.

Do the leaves make more stomata as they grow? Do the stomata that are present just spread out as other epidermal cells multiply and increase in size? Do the leaves retain the same stomatal density as they grow?

Due to the colour of the lower epidermal cells and the cells associated with stomata in Tradescantia zebrina, no preparation is needed and leaf discs, cut simply with a holepunch, can be placed directly on a microscope slide for viewing without a coverslip.

Before you start with this specimen, it could be a good idea to build students’ measuring and calibrating skills through our paper-based activity.