What type of cellular structure are amyloplasts, and what is their role in plants?

Amyloplasts are a type of plastid specifically involved in the storage of starch in plant cells. They synthesize and store starch granules, which serve as an energy reserve for the plant. This function is vital for energy metabolism, particularly when photosynthesis is not occurring, such as during the night or in non-photosynthetic tissues.

In addition to their role in starch storage, amyloplasts also play a part in gravitropism, which is the growth response of plants to gravity. By accumulating starch granules, they can act as statoliths—a specialized function that helps the plant sense its position relative to gravity. This information is crucial for orienting growth toward or away from gravitational pull, guiding roots downward (positive gravitropism) and shoots upward (negative gravitropism).

This context makes the connection clear that option B focuses on both the storage capability and the involvement in gravitropism, highlighting the multifunctional role of amyloplasts in plant biology.