See this on the BBC Four Botany: A Blooming History for a clearer picture when using with students.

This video clip from the BBC (from the TV series Botany: A Blooming History) looks at the work of Benson and Calvin investigating photosynthesis in the 20th century.

The work of Benson and Calvin on the biochemistry of the light independent reactions of photosynthesis is explained. Using radioactive carbon to supply algae in the 'lollipop' apparatus with labelled carbon dioxide allowed the subsequent tracing of the carbon compounds they produced. The process of chromatography and the production of x-ray chromatograms which enabled the scientists to identify the chemicals are shown. This is the basis of the knowledge we have of the Calvin-Benson cycle, but it took over 10 years to establish in its entirety.

This can be used as an introduction for higher level students to the light independent reactions of photosynthesis and the Calvin-Benson cycle. The idea of scientists using the innovations from other areas of science and applying them in a new context can also be discussed. The use of radioactive isotopes in tracing pathways can be highlighted. This can also be developed in terms of diagnosis of disease, the following of pathways in other organisms etc.