jamesw said:
Good article - I'm familiar w/ it and understand the material. What it implies though is that the ONLY "useful" light is the wavelengths that stimulate:
chlorophylls a, c², and peridinin (the light-harvesting carotenoid, a pigment related to chlorophyll) and ~620-700nm which is the red absorption bandwidth of chlorophylls a and c².
I don't agree w/ that.
Cheers
James
What you quoted above is probably true for Plants and Chlorophyll which is why most grow lights appear reddish. What I got out of it is that there are 3 important light ranges that almost cover the entire visible spectrum as stated in the article;
PUR (Photosynthetically Usable Radiation) should also be considered. PUR is that
fraction of PAR that is absorbed by zooxanthellae photopigments thereby stimulating photosynthesis. PUR are those wavelengths falling between 400-550nm and 620-700nm.
*A: 400-500 NM range - Phototropic response; having a tendency to move in response to light. Basically this is the Chlorophyll containing plant or algae "moving" to respond to a positive light source to begin the process of photosynthesis (initial growth of plants, zooxanthellae, etc.).
*B: 580-750 Range - Photosynthetic response; the process which begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls.
*C: 450-500 and 650-700 Range - Chlorophyll synthesis is the chemical reactions and pathways by the plant hormone cytokinin soon after exposure to the correct Nanometers wave length (about 670 NM) of light resulting in the formation of chlorophyll, resulting in continued growth of a plant, algae, zooxanthellae and the ability to “feed” and propagate, and without this aspect PAR (670 NM light energy), zooxanthellae and plants cannot properly “feed” propagate. The results of the lack of this high PAR “spike” would be stunted freshwater plant growth, and eventually poor coral health in reef tanks
So, although C is the most important A and B are needed as well. In addition other parts of the spectrum support other specific forms of life (cyano). The benefit of LED is that specific light spectrums can be acheived to reduce negative life forms. Since I switched to LED Cyanobacteria is gone (although perhaps is was already going away due to other processes).
A, B and C are below;
