The aim was to show that light is necessary for photosynthesis.
Appendix A – Photosynthesis and Visible Light
During the process of photosynthesis, carbon dioxide plus water in the presence of sunlight, enzymes and chlorophyll produce glucose and oxygen as waste product.
Figure 24. Red light generated the highest rates of photosynthesis.
In addition to using chlorophylls and carotenoids for photosynthesis, plants use these and other photopigments for a wide variety of functions. The phytochromes Pr and Pfr, for example, respond to 660 nm red and 735 nm infrared radiation respectively, and in doing so induce seed germination and flowering, regulate leaf expansion and stem elongation, and trigger photoperiod and shade avoidance responses (see Appendix A).
Blue and Red Light in Photosynthesis - excite Deutschland
The measured rate of photosynthesis as a function of absorbed wavelength correlates well with the absorption frequencies of chlorophyll a, but makes it evident that there are some other contributors to the absorption.
Why is Blue and Red Light important
Photosynthesis is the ability of plants toabsorb the energy of light, and convert it intoenergy for the plant. To do this, plants havepigment molecules which absorb the energy of lightvery well. The pigment responsible for mostlight-harvesting by plants is chlorophyll, a greenpigment. The green color indicates that it isabsorbing all the non-green light-- the blues(~425-450 nm), the reds and yellows (600-700 nm). Red and yellow light is longer wavelength, lowerenergy light, while the blue light is higherenergy. In between the two is green light(~500-550 nm). It seems strange that plantswould harvest the lower energy red light insteadof the higher energy green light, unless youconsider that, like all life, plants first evolvedin the ocean. Sea water quickly absorbs thehigh-energy blue and green light, so that only thelower energy, longer wavelength red light canpenetrate into the ocean. Since early plants andstill most plant-life today, lived in the ocean,optimizing their pigments to absorb the reds andyellows that were present in ocean water was mosteffective. While the ability to capture thehighest energy blue light was retained, theinability to harvest green light appears to be aconsequence of the need to be able to absorb thelower energy of red light.