The main function of the leaves on a plant is to facilitate photosynthesis, a process that converts sunlight into chemical energy. Leaves contain chlorophyll, the pigment responsible for capturing light energy, which, combined with water and carbon dioxide, allows plants to produce glucose and oxygen. Additionally, leaves play a crucial role in gas exchange and transpiration, helping regulate water uptake and maintaining overall plant health. Through these functions, leaves are essential for a plant's growth and survival.