Here's why:

* Photosynthesis: Leaves are the primary sites of photosynthesis in plants. During photosynthesis, leaves use sunlight, water, and carbon dioxide to produce glucose (a simple sugar) and oxygen.

* Energy Storage: Glucose is a form of chemical energy that plants use for growth, development, and other life processes.

* Conversion: The glucose produced in leaves can be further converted into other forms of energy storage, such as starch, which is stored in the plant's roots, stems, and seeds.

So, while the food initially exists as glucose, it can be transformed into different forms for the plant's needs.