Explanation:

The growth of a plant toward any stimulus is called tropism, and the growth of a plant toward a light stimulus is called phototropism - photo means light. Seedlings of plants grow straight upward in dark environments in order to reach the sunlight above ground. Once they break through the surface, they start bending toward the light because the growth of cells on the dark side is faster than the cells on the light side. However, if the amount of light is the same on all sides of the plant, then it will continue to grow straight upward instead of bending.