Light by itself has no influence on growth. In fact high intensities of light may even retard the growth of a plant. Plants grown in complete darkness however show etiolating i.e., yellowing of the leaves due to poor development of chlorophyll. Absence of light, leads to elongation of internodes, tenderness in stem and poor development of mechanical tissues. On the other hand, plants grown in the presence of light are strong statured. Light also helps in morphogenesis. Duration of ligh affects the flowering process and this is called photoperiodism.