Final answer:
Grana or granum is used to describe stacks of thylakoids in chloroplasts.
Step-by-step explanation:
Stacks of thylakoids are described as grana or granum. These terms refer to the structures found within chloroplasts, which are responsible for photosynthesis in plants. Thylakoids are flattened membrane sacs that contain chlorophyll, the pigment that captures light energy. When thylakoids are stacked on top of each other, they form grana or granum.
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