Why so Much Red Spectrum Light Compared to Blue in LED Grow Lights?

Phar

Phar

Member
OK so according to official Photosynthesis breakdown the process utilises about a ration of 7:5 (430nm & 680NM peaks)

So my question is why is everyone adopting the reverse of these findings (see chart)



So Looking at the absorption rate above on Chlorophyll a line (which is the main line to consider) more blue is absorbed than red by a ration of about 7:5

So why of why is it normally the opposite of this I am seeing in many grow light spectrums? Where is the proof that during flowering more red is used as opposed to the ratio indicated for photosynthesis in the chart above of 7 to 5 ratio of blue to red absorption?
 
Phar

Phar

Member
I have seen that graph and it somewhat vague, as is definition of plant response? Most photosynthesis graphs i have seen show higher adsorption of red light hence my question! Plus it was developed in 1971 ! Everything i have red up on indicates green adsorption is negligible yet folk are still using this curve !!??

This chart (cant find data set) show similar from another post https://www.rollitup.org/t/lighting-efficiencies.760622/page-3
 
Last edited:
C

churchhaze

Well-Known Member
Phar said:
I have seen that graph and it somewhat vague, as is definition of plant response? Most photosynthesis graphs i have seen show higher adsorption of red light hence my question! Plus it was developed in 1971 ! Everything i have red up on indicates green adsorption is negligible yet folk are still using this curve !!??

This chart (cant find data set) show similar from another post https://www.rollitup.org/t/lighting-efficiencies.760622/page-3
Click to expand...
How well chlorophyll absorbs a wavelength is not the same thing as how effective the wavelength is utilized for photosynthesis. It only tells you how likely it is for that wavelength to be absorbed, vs transmitted or reflected. But if it's transmitted or reflected, chances are it will be absorbed somewhere else. When a green photon is finally absorbed, it does just as good of a job at powering photosynthesis as orange or red photons.

Blue photons are very high in energy when compared to red photons. Too much actually causes damage to tissue, and the plant responds to protect itself from the harmful excess blue.

A better answer is simply to go try using a blue dominant spectrum and tell us how well it works out for you. Most scientific studies, along with anecdotal observations, show that between 13-20% is the optimal amount of blue for plant growth.

Blue leds are actually the highest efficiency light sources available on the market, so it would be really great if we needed more blue.
 
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