For Advanced Hobbyists - Importance of Green Light in Photosynthesis

[Dana Riddle]

Shawn Wilson (lighting expert in Canada) forwarded this journal reference to me.
https://academic.oup.com/pcp/article/50/4/684/1908367
In a nutshell, green light can promote photosynthesis better than red light in conditions of intense white light. Although the research is directed at terrestrial plants, the importance of green light in aquatic ecosystems could be critical, and could help explain why early LED units with lots of whitish light mixed with green light could grow corals. Food for thought.

 

[mcarroll]

Very interesting! Will have to dive into this later.

 

[Dana Riddle]

Awaiting your thoughts!

 

[chefjpaul]

Photosynthesis is photosynthesis....or is it?
Very interested in learning this one.

 

[gcarroll]

Very interesting! If I recall correctly, Shawn was the Canadian Orphek rep. Isn't Orphek the LED manufacturers who railed against the other companies who included green LEDs in the lights as they chose to exclude them. Now all of a sudden half a decade after others included them, they are now including them. Hmmm.

 

[Dana Riddle]

Very interesting! If I recall correctly, Shawn was the Canadian Orphek rep. Isn't Orphek the LED manufacturers who railed against the other companies who included green LEDs in the lights as they chose to exclude them. Now all of a sudden half a decade after others included them, they are now including them. Hmmm.

I don't know about all that, but a review of peridinin's absorption bandwidth would have laid that issue to rest!

 

[oreo54]

Hmmm.. Most seems to imply the benefit is green light (in high sunlight) can penetrate deeper in the leaf tissue.
Structural differences may not make it apply to corals.


Suspect green is chosen over cyan just due to availability and "convention" for the most part.
Peridinin has a pretty wide absorption band per this. Always thought cyan was a better choice to add "green" anyways,
It (cyan) would be in short supply w/ white/green LEDs..

Green LED's do notoriously spread more than most other "colored" LED's and efficiency is low. Thus: Lime..(phosphor corrected green)

 

[mcarroll]

Structural differences may not make it apply to corals.

This really gets into some aspects the structural features of coral:
The in situ light microenvironment of corals

Here are some of the quotes I highlighted back in 2016:

(yes there's a big about green you'll like....and I'm "Ed:" on the comments)

Light is strongly scattered at the water–tissue interface and within the coral tissue, where photon trapping and redistribution leads to significant enhancement in the local scalar irradiance compared with the incident downwelling irradiance (Ku ̈hl et al. 1995; Wangpraseurt et al. 2012a).

Additionally, reflective, fluorescent, or both host pigments are synthesized by many corals, which further alters the intensity and spectral quality of light due to, for example, intense scattering and red-shifted emission (Salih et al. 2000).

Finally, photons that pass through the tissue are backscattered by the aragonite skeleton, further enhancing tissue scalar irradiance and thus photon availability for zooxanthellae photosynthesis (Enriquez et al. 2005; Marcelino et al. 2013).

Spectral scalar irradiance at the upper surfaces of faviid corals (E0) differed markedly from the incident downwelling irradiance (Ed; Fig. 3). Depending on the wavelength in the PAR region, the E0 : Ed ratio varied between 0.8 and 2.4, with the most pronounced enhance- ment at wavelengths 500–640 nm and . 680 nm (Fig. 3a–c).

[Ed: 500-640 nm is green of plant and human-color-vision “fame”, and 680nm is far-red like the light emitted from chlorophyll.]

it will be useful to compare differences between coenosarc and polyp tissue because they differ in total light exposure and spectral quality (Figs. 3, 4; Wangpraseurt et al. 2012a) and can exhibit different patterns of photoacclimation (Ralph et al. 2002).

 

[oreo54]

Lot in that..
http://onlinelibrary.wiley.com/doi/10.4319/lo.2014.59.3.0917/epdf

 

[mcarroll]

Lot in that..
http://onlinelibrary.wiley.com/doi/10.4319/lo.2014.59.3.0917/epdf

Yawp....it's deep.

 

[Dana Riddle]

Re: The question of red light absorption for shallow water corals. Resonance transfer will stimulate P-680 (Photosystem II) and P-700 (Photosystem I) at depth where little or no red light is available.

Hmmm.. Most seems to imply the benefit is green light (in high sunlight) can penetrate deeper in the leaf tissue.
Structural differences may not make it apply to corals.


Suspect green is chosen over cyan just due to availability and "convention" for the most part.
Peridinin has a pretty wide absorption band per this. Always thought cyan was a better choice to add "green" anyways,
It (cyan) would be in short supply w/ white/green LEDs..

Green LED's do notoriously spread more than most other "colored" LED's and efficiency is low. Thus: Lime..(phosphor corrected green)

 

[saltyfilmfolks]

Please define..... “white”.




Can’t wait to read this. ;Bookworm

 

[mcarroll]

Please define..... “white”.

How about an answer unencumbered by lots of words?

This is the white light part of the sun's Spectrum:

Here's the whole Solar spectrum from 296 nm to 1300 nm:

(According to NOAO)

 

[Abhishek]

Very interesting Dana ! As I already mentioned to you, this actually makes me wonder whether my understanding all this while was a little screwed . Years ago and even now many people will swear by the capability of Iwasaki 6500K or xm 10000K bulbs to grow acroporas and it was evident that they had highest PARs . Me and many others were of the opinion that the high PAR grew faster acroporas !

What if it was the actual increased UV spectrum emitted and the increased green spectrum emitted by these bulbs were the true reasons for enhanced photosynthesis and with proper balance of nutrients resulted in faster growth in acroporas !

Am sure I can dig up old Sanjay's website for a spectrum chart of these bulbs but pretty sure they had spikes in the green spectrums .

Regards,
Abhishek

 

[saltyfilmfolks]

How about an answer unencumbered by lots of words?

This is the white light part of the sun's Spectrum:

Here's the whole Solar spectrum from 296 nm to 1300 nm:

(According to NOAO)

Lol.
Nerd.

 

[Dana Riddle]

Since this paper examines the effects of red, green, and blue light, I'm assuming 'white light' is due to additive color mixing of those 3 colors. I don't see where that is clearly defined in the paper however, maybe I just missed it.

 

[Daniel@R2R]

Great stuff! I wonder how this is likely to affect the way future LED fixtures layout their colors.

 

[ksed]

Shawn Wilson (lighting expert in Canada) forwarded this journal reference to me.
https://academic.oup.com/pcp/article/50/4/684/1908367
In a nutshell, green light can promote photosynthesis better than red light in conditions of intense white light. Although the research is directed at terrestrial plants, the importance of green light in aquatic ecosystems could be critical, and could help explain why early LED units with lots of whitish light mixed with green light could grow corals. Food for thought.

So why are green houses still using primary blue and red lighting?
Would they have not experimented with green?

 

[Sallstrom]

So why are green houses still using primary blue and red lighting?
Would they have not experimented with green?

Something to do with power consumption maybe? I think red is the "best" in that aspect, but need to refresh my memory before I promise anything

/ David

Ps @Lasse , this is a tread for you

 

[oreo54]

Well first, the "science" is new.
Secondly, due to the cost of LEd's it went w/ MAX PAR at min "waste" PAR
3rd they eventually included some white since people can't diagnose "black"plants
Things are still in flux.. you will prob see more whites in real hort.
Bottom line. Matter of economics originally..