WHAT ARE PYRENOIDS IN SPIROGYRA?
Pyrenoids occur in many of the algae and are associated with the chloroplasts. Some of them are known to contain Rubisco, the enzyme that catalyzes the incorporation of inorganic CO2 into carbohydrate. In these algae, pyrenoids probably function to fix carbon.
In other algae, such as Spirogyra, pyrenoids are the sites of carbohydrate (typically starch) storage.