How Plants Respond to Light

Plants use light for photosynthesis and photomorphogenesis. Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy. Photomorphogenesis refers to how plants modify their growth in response to light spectrum. One example of photomorphogenesis is a plant bending toward a light source. Light also affects plants’ developmental stages, such as germination and flowering. The light that plants predominately use for photosynthesis ranges from 400–700 nm. This range is referred to as Photosynthetically Active Radiation (PAR) and includes red, blue and green wavebands. Photomorphogenesis occurs in a wider range from approximately 260–780 nm and includes UV and far-red radiation. Chlorophyll a and b are a plant’s primary photosynthetic pigments. It’s important to note that chlorophyll most strongly absorbs red light (600–700 nm) and blue (400–500 nm) and minimally absorbs green light (500–600 nm).