in the green alga Chlamydomonas reinhardtii, as well as starchless mutants with perfectly formed pyrenoids, eventually discredited this hypothesis.

It was not before the early 1970s that the proteinaceous nature of the pyrenoid was elucidated, when pyrenoids were successfully isolated from a green alga, and showed that up to 90% of it was composed of biochemically active RuBisCO. In the following decade, more and more evidence emerged that algae were capable of accumulating intracellular pools of DIC, and converting these to CO₂,