The spectrum action curve you have posted, and that you may find on most botanic books, is just a sum of the absortion of the different pigments present in the higher green plants.

But it notably differ from what is observed actually on live plants, that uses green way better than that, along with other differences.

There is some things that explain that difference:

-Pigments arnt distributed homogeneously along leaves, but stratified.

-They arnt present of the same relation, and almost never at the 1:1:1 (Chl a: Chl b: carotenoids) that is used to obtain the action curve. It varies with the tipe of light, for plant specie, light intensity that they receive on the long term...

-And the most important: absortion of lab's extracted pigment on solution is very different to absortion of those same pigment in vivo. The process is still very unkown, but the fact is same pigment molecule may absorb the better light of a given wavelenght depending of its orientation (into the leave) and depending to the protein its binded. For example, the central Chlorofill a molecules on the Photosynthetic Reaction Center have a max of 680nm (Photosystem II) and 700nm (Photosystem I), while its the same molecule. Max absorbance from 650 to 720nm of the same molecule has been reported.

So the action spectrum curve you posted is a virtual creation, from unrealistic lab's extractions, while McCree and Inada curves were obtained measuring the photosynthetic response of in vivo plants.
knna Reviewed by knna on . Building LED lights from facts, no theories I was going to post this at the Perfect LED Grow Light thread, but as some of what im going to post was posted 2 years ago on the stickied thread about LEDs and people still continue developing lights from wrong ideas, i think a thread about this topic is largelly needed. The main problem is related to efficacy of spectrums. When the firsts LED experiments at Overgrow, we work on the hypothesis that blue and red light are more effective. It was an appealing hypothesis that promises large Rating: 5