The storage form of glucose in plants is starch . Starch is a polysaccharide. The leaves of a plant make sugar during the process of photosynthesis. Photosynthesis occurs in light ( photo = light), such as when the sun is shining. The energy from the sunlight is used to make energy for the plant. So, when plants are making sugar (for fuel, energy) on a sunny day, they store some of it as starch. When the simple sugars need to be retrieved for use, the starch is broken down into its smaller components. They literally save some energy for a rainy day!