[somewhatshocked]

Thought some of you may be interested in reading this article about why plants are green. It's a brief explanation of a report in the journal Science.

Not gonna include an excerpt so as not to ruin it for anyone. But you may find it worthwhile - especially if you're a lighting nerd.

 

[Deanna]

All right, I’ll bite: so, what does that mean in terms of the light we supply? Could it also mean that we are wrong, for example, when we supply only red and blue, such as with the common “grow-lights” for terrestrial plants? Yet, the hydroponics industry seems to maximize growth by out-sizing the reds and blues relative to the greens.

I was surprised to see that plants actually absorb/utilize as much as 90% of the middle of the visible spectrum. If that is where most energy exists, wouldn’t 90% in the high-energy middle still be more than 100% at the weaker ends of the spectrum? Maybe the message is that we need to re-define what the photosynthetic usable radiation (PUR) curve is, if it is not primarily blue and red.

I’m in the LED side of lights and, I think, these are trying to reduce green/yellow energy in favor of red/blue. Maybe it’s better to match the relative sunlight (we can’t match actual PAR - sunlight is too strong) at every point along the visible curve and let the plants pick their flavor, i.e.; maybe we are starving them for essential green energy and should be providing light in an EI format at every nanometer. If it really is a stability optimizing process, it seems that we provide stable green simply because of the full control that we have over our lights (no clouds forming over our water).

Has anyone tried adding an overlay of heavy green to existing lighting?

 

[Plinkploop]

All right, I’ll bite: so, what does that mean in terms of the light we supply? Could it also mean that we are wrong, for example, when we supply only red and blue, such as with the common “grow-lights” for terrestrial plants? Yet, the hydroponics industry seems to maximize growth by out-sizing the reds and blues relative to the greens.

I was surprised to see that plants actually absorb/utilize as much as 90% of the middle of the visible spectrum. If that is where most energy exists, wouldn’t 90% in the high-energy middle still be more than 100% at the weaker ends of the spectrum? Maybe the message is that we need to re-define what the photosynthetic usable radiation (PUR) curve is, if it is not primarily blue and red.

I’m in the LED side of lights and, I think, these are trying to reduce green/yellow energy in favor of red/blue. Maybe it’s better to match the relative sunlight (we can’t match actual PAR - sunlight is too strong) at every point along the visible curve and let the plants pick their flavor, i.e.; maybe we are starving them for essential green energy and should be providing light in an EI format at every nanometer. If it really is a stability optimizing process, it seems that we provide stable green simply because of the full control that we have over our lights (no clouds forming over our water).

Has anyone tried adding an overlay of heavy green to existing lighting?

My low tech saw better growth when I upped my green and lowered my blue. I just played around with my finnex and dialed in a higher green at "sunrise" and "sunset" and no red at "sunset". A lot of the newer terrestrial grow bulbs are including low green content as well. I've noticed this in the past 2 years. I just picked up a cheap led grow bulb and there's 2 green leds in the middle. Maybe this will be a trend?

 

[jeffkrol]

We

All right, I’ll bite: so, what does that mean in terms of the light we supply? Could it also mean that we are wrong, for example, when we supply only red and blue, such as with the common “grow-lights” for terrestrial plants? Yet, the hydroponics industry seems to maximize growth by out-sizing the reds and blues relative to the greens.

Yes this has been dis-proven..
see Bugbees research:

 

[Deanna]

jeffkrol

So, we need infrared, now, as well as green. According to my Seneye, my Twinstar (like every other LED I've owned - although the Twinstar is superior), I have green that is lower intensity than the blue, but a little higher than red, so, the 90% utilization of the green spectrum is from a very weak base. Then, spectral transmission drops to zero by the time the white light ends at 700nm, so there is no hope of getting the near-IR of 700-750.

Do you know of a way to, essentially, match the wavelengths of the sun, but not necessarily with the same intensity, perhaps a supplement to the standard LED's we now have? Have you seen spectral curves for those new "Sun Filled" GE lights you mentioned in another post?

 

[jeffkrol]

After watching a bunch of his videos my "conclusion" is inconclusive.
IR has mixed effects depending on species and none included aquatics.
Other studies showed benefits only
when light intensities reached photosaturation .
That may gave some benefit to aquatics that have low par saturation points
Then again those low points are still high compared to common light output .

There was also some that concluded you inly git vebefits by applying fr 15 min before and ir 15 min at the end if the photoperiod.
Not sure where that came from though
Fr has been known to initiate flowering (do we need that?) and to stretch plants

Another unknown is the aquatic environment is backwards to the terrestrial one w/ high blue ratio signalling "shade". Reds being attenuated at even modest depths.
Point is nothing found us really currently studied in nor applied to aquatics.
Think of the differences in form of emergents which must involve a massive reconfiguration of biosystems (personal thought).

As to leds there are "Emerson effect" strips you can buy

Bud Booster Emerson Effect Sun Board 48 LED Strip 660nm 730nm IR Quantum Grow
$20.67/eaFree Shipping

Or 730nm diodes.
660's tail into ir though believe it is under like 1%
Those " full spectrum" blue plus red phosphor diodes seem to tail in more than the 660s do. At least on paper.

I run pure 660 for a period during initial lights on and pure 660 prior to lights off. Mostly because I like it.

 

[jeffkrol]

My current thinking really sort of ignores ir for the reasons stated in the above ramblings.
I lean to uv and it's possible benefits for pigment production and the anomaly that some pigments require red light to be produced.
About the opposite of common thinking
Heavy blue (uv) or high intensity.

Most mercury emission bulbs have some uv.
Again here there are proven benefits to "some" plants as to increases in " flavonoids" or aromatics.
Then there is which uv?
And which could apply to submerged plants ( light attenuation again and a different " world)

Interactive Effects of UV-B Light with Abiotic Factors on Plant Growth and Chemistry, and Their Consequences for Defense against Arthropod Herbivores

Ultraviolet-B (UV-B) light plays a crucial role in plant–herbivorous arthropods interactions by inducing changes in constitutive and inducible plant defenses. In particular, constitutive defenses can be modulated by UV-B-induced photomorphogenic responses and changes in the plant metabolome. In...

www.frontiersin.org

.

Actually awaiting his work on uv.

 

[Deanna]

Then infrared occasionally ...maybe. Besides, it's hard enough to push red through water. IR must be even harder than red. Still leaves the question around whether or not there is value in a higher PAR value for the green, as opposed to the typical dip that is artificially created between blue and red.

Look forward to your reporting on the UV, once the study is completed.

 

[jeffkrol]

Bugbee's doing the work on uv.

Well my new build uses pc amber,
lime, cyan, royal blue and 3 deep reds.

I have no shortage of photons between 490 and 625.

Even big companies screw up.. Someone forgot to code the x100

 

[Phil Edwards]

That's really interesting Jeff, thanks for sharing.