Sunlight and water both support the production of chemical nutrients inside the cells of a plant. Sunlight is critical in the process during which water molecules are broken apart inside the pigmented cells of the plant. Water also transports the nutrients throughout the plant and supports its structure.
This dependency on light to transfer electrons during photosynthesis, also known as Hill Reaction, remains mysterious to scientists. What is known is that during the reaction between the plant's cells and the sun's light, water molecules are broken apart, creating energy in the form of chemical food for the plant, as well as expelling extra "ionized" hydrogen atoms as waste in the form of the very oxygen that supports all life on earth. This makes the importance of water to a plant's life quite clear. Without it the plant would not be able to produce the food it needs to survive.
Plants need water for more than just food production, however. It is also needed to transport nutrients throughout all the plant's cells, from the roots to the leaves, for example. By keeping the plant's cells full and rigid, water also plays a critical role in supporting the physical integrity of a plant.
Water and sunlight are not the only ingredients that plants need to produce food. In addition to light and moisture, plants need carbon dioxide from the air, which is converted into sugars in a process known as the Calvin Cycle.