Measuring and calibrating in microscopy: Measuring chloroplast speed

This activity provides an opportunity for students to practise calibrating a microscope whilst exploring the dynamic nature of cells.

Cytoplasmic streaming occurs in many large plant cells. This is thought to be an adaptation to increase the rate of mixing the contents of the cytoplasm. In the pondweed Egeria densa the chloroplasts move along with this cytoplasmic streaming. This allows the dynamic nature of living cells to be observed, for the speed of chloroplast movements (and therefore cytoplasmic streaming) to be calculated, and for students to get a sense of ‘what counts as fast’ at a subcellular level.

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