- Distinct, rounded, proteinaceous bodies
- It consists of a central, viscous granular proteinaceous core surrounded by tightly packed minute plates of starch.
- Thylakoid system pass through pyrenoid
- Site of starch formation.
- During starvation, the size of pyrenoids diminishes and finally disappears later reappear on return of favorable condition.
- Some considered as reserve proteins.
- Some considered as specific organ of cell.