without sunlight, there could not be life on the earth. plants need sunlight for the process of photosynthesis. during photosynthesis the plants use the energy of the sunlight, water, and carbon dioxide, to create glucose (sugar). the glucose can later be used by the plant for energy or animals eat the plant and the glucose in it. plants need sunlight to grow green. without enough sunlight but with enough water, the plant grows very tall very quickly, but looks yellow and dehydrated, although when touched, the leaves are very moist.