feedback from growers about how you think about the LED and what you believe LEDs could do better.
The spectrum currently is based on a number of historic misconceptions and doesn't fully warrant the research of the last +20 years. It's basically just white light amended by a few isolate monochromatic diodes to push efficiency further and deliver some "full" spectrum lightrays for additional secondairy pigment buildup.
3500k + 660nm + (730 + 385 or 400nm) That's it, the only thing that changes are the used ratios relative to these.
In other words, they basically are the same and there is no alternative in sight due to a lack of efficient monochromatic diodes.
However, there are several scientific investigations available and these show/proof that:
- 340 (+-10nm) can improve photosynthesis rate by greatly transmission through a leaf and induce blue etc fluorescence near the guardcells (stomata opens). It also already touches slighty into the UVR8 monomer absorption. The other normally used UVA wavelengths 365 385nm will actually have an opposite effect!
- Investigations into the trapping kinetics of Photosystem I show ultrafast exciton extinction of photons 690-715nm as these are absorbed directly by its Reaction Center (RC) p700. Whereas the todays 730nm diode farred tail at around 745nm already considerably slows down trapping rate.
Now Emerson, Rabinovitch, Govindjee et al -recently Bugbee - have shown that a light recipe being comprised of, at least, 20% photons 680-780nm would result in an optimal photosystem 1<>1 stoichiometry, but the today's used 730nm diodes already excites the phytochrome too much. The Pfr antagonism is even at ~695nm, too with red 660nm greatly opposing it. But this wavelength also preferrentially excitates Photosystem 2 over 1, thus will not lead to a good PS2<>1 balance.
So it stands to reason a 690-710nm diode should do this task.
- The 'Cyan Gap' at ~490nm that's a remnant of the times when manufacturers believed the chlorophyll solvent absorption spectras hold also true in nature. But there are several reasons why this wavelength should be included as well:
- colour-trueness esp. increased contrast-richness
- carotenoids also deliver excitons to the chlorophyll funnel
- higher photosynthesis rate with 490nm vs 440nm in isolate experiments
- The whole UVA/blue region 320-500nm is filled with various photoreceptors and secondary pigments (anti-oxidants) that filter much of said radiation but show great beneficial potential for human food, it stands to reason one shouldn't exclude these wavelengths but instead deliver them in a broad range, but only very soft.
But there are no broadrange UVA diodes.
>> Some of these wavelengths (490 vs 450nm, and 700 vs 660nm) are comprised of photons with lower energy value (frequency) and thus, could be fabricated by a novel monochromatic diode with a higher quantum flux thus increasing efficiency two-fold (if used).
