What is the primary energy reserve in plants like sweet potatoes?

The primary energy reserve in plants, including sweet potatoes, is starch. Starch is a polysaccharide composed of long chains of glucose molecules. It serves as a key storage form of energy, allowing plants to store excess glucose produced during photosynthesis. When plants need energy, they can break down starch into glucose through hydrolysis, making it readily available for cellular respiration and other metabolic processes.

Many plants, especially tubers like sweet potatoes, accumulate starch in specialized storage tissues, which not only provides energy for the plant's own growth and development but also serves as an important nutrient source for organisms that consume these plants. This characteristic is fundamental for survival during periods when photosynthesis is not possible, such as during the night or in unfavorable environmental conditions.

Other options, while important in their own right, do not serve as the primary energy reserve in plants. Proteins are essential for structural and functional roles in cells, sucrose is a transport form of sugar that can be readily utilized but is not stored in large quantities, and cellulose, which forms the structural component of plant cell walls, is not a digestible energy reserve for plants.