Insoluble fiber is primarily found in what parts of plants?

Insoluble fiber is primarily found in the cell walls of plants, which are most abundant in seeds and stems. This type of fiber does not dissolve in water and plays a critical role in promoting digestive health by adding bulk to the stool and assisting with regular bowel movements. The structure of seeds and stems offers a higher concentration of cellulose, a primary component of insoluble fiber, as these parts provide rigidity and support to the plant.

Roots, fruits, leaves, flowers, branches, and bark also contain various types of nutrients and fibers; however, they are not as significant sources of insoluble fiber as seeds and stems. Roots and fruits often provide soluble fiber, while leaves and flowers can vary widely in their fiber content. Thus, while the other choices contribute to a plant's overall fiber content, seeds and stems are the key components associated with insoluble fiber.