Green Light

Since chlorophyll does not absorb green light as readily as other wavelengths, many have written off the green waveband as being less important to plant growth. This lower chlorophyll absorption rate, compared to blue and red light, is what makes most plants appear green. Depending on the plant, leaves generally reflect 10-50% of green waveband photons. In contrast to assumptions, studies of green light in crop production have concluded that green light is important to photosynthesis, and especially in a plant’s lower leaves. Around 80% of green light transmits through chloroplasts, whereas leaves absorb approximately 90% and transmit less than 1% of red and blue light. So what does this all mean? When light is plentiful, chlorophyll reaches a saturation point and can no longer absorb red and blue light. Yet, green light can still excite electrons within chlorophyll molecules located deep within a leaf, or within chloroplasts lower in the plant’s canopy. And so, green light enhances photosynthetic efficiency—potentially increasing crop yields, during bright light conditions. Additionally, the ratio of green to blue and red wavelengths signals to the plant a leaf’s canopy position. This can induce morphological changes to maximize light absorption. Green light also plays a role in regulating stomatal aperture (opening and closing of plant pores that make gas exchange possible). Greenhouse applications require less supplemental green light since plants receive adequate green light from solar radiation.  Indoor environments may benefit more from supplemental green light since no sunlight is present.