The glucose made in photosynthesis is used in several ways. Some is used for respiration, which releases energy for the plant's cells.
Glucose can be converted into starch for storage. Starch is insoluble, so it does not dissolve in the cell and is a good store. You can test for starch with iodine solution, which changes from orange-brown to blue-black. Glucose can also be used to make fat or oil for storage. Plants make cellulose from glucose, and cellulose strengthens the cell wall.
Plants also use glucose to make amino acids, which are joined together to make protein. To do this, plants need nitrate ions, which they absorb from the soil.