Led vs HPS growing

hybridway2

Well-Known Member
Yes, well, these IR photons carry less energy than PAR photons so if we could shift them into the 600-700nm region the increase in the curve would be diminished to ~~50%-75% of the original IR curve (very grossly estimated now - but it can be calculated quite easily...)

View attachment 4652405
^^ in this case, if the IR spike would just be half it would be perfect IMO (just like a CMH has) ^^

just to illustrate an example for the relative differences in energy-content:
View attachment 4652412

Bugbee mentioned that FR/IR photons are very energetically efficient to create and if we can take them in in a productive way, they are a nobrainer.
As for UV - which reaches down to 280nm, it's very costly, and even destructive to LED tech.
So that's why I don't have a grudge against high Kelvin-rated MH lamps, as these photons are precious from a certain point of view, esp. in combination with white CRI LED "filling in the gap beyond the Soret-peak" or "completing the spectrum to be more sunlike and less monochromatic"

View attachment 4652418

Then, the green -controversial- wavelength ... LEDs currently do not excel here at all... but there are some high CRI CMH lamps:
View attachment 4652424
^^ should have quite some penetration power ^^
Actually this lamp is designed for photography etc as it has a CRI 98 and high irradiance.

Compare this to the irradiance of the sun:
View attachment 4652428

But my fave in terms of spectrum is still the MH & HPS duallamp:
View attachment 4652438
^^ not perfect (could add some 660nm monos, and have more green) but may highly meet the 1:4 ratio of blue:red (400-500nm : 600-700nm) where net photosynthesis is highest ^^

There are some CMH lamps that come very close, or even slightly better, than this but, as you can see, most of these spectral sheets don't even show the complete range! (mind-boggling that a manufacturer of a plant-light de-values its own product - AS IF only PAR would matter!)

TBH I think all CMH or MH/HPS combos make an excellent sunlike spectrum. (LEP/ Plasma/ Mercury vapour as well...)

The sun (for comparison):
View attachment 4652450

I wonder how good LED would fare if one would build a rack that would imitate either a HPS, MH or CMH lamp spectrum-wise? Would they still crank more umols out?

Another thing to consider is that some HID lamps are deadcheap and therefore, can easily be swapped as a means to change the spectrum when needed or beneficial (flower induction, ripening, manipulating internode length etc)

Now I've made a huge case in favour of HIDs but one thing to keep in mind is that HID technology is at the end of its development whereas LED will gain each year- and actually IS already better in terms of raw umol output IF we allow ourselves to compare the raw output of different spectra against each another (actually an apple-vs-orange comparison IMO....)
Nice post!
 

hybridway2

Well-Known Member
Yes, well, these IR photons carry less energy than PAR photons so if we could shift them into the 600-700nm region the increase in the curve would be diminished to ~~50%-75% of the original IR curve (very grossly estimated now - but it can be calculated quite easily...)

View attachment 4652405
^^ in this case, if the IR spike would just be half it would be perfect IMO (just like a CMH has) ^^

just to illustrate an example for the relative differences in energy-content:
View attachment 4652412

Bugbee mentioned that FR/IR photons are very energetically efficient to create and if we can take them in in a productive way, they are a nobrainer.
As for UV - which reaches down to 280nm, it's very costly, and even destructive to LED tech.
So that's why I don't have a grudge against high Kelvin-rated MH lamps, as these photons are precious from a certain point of view, esp. in combination with white CRI LED "filling in the gap beyond the Soret-peak" or "completing the spectrum to be more sunlike and less monochromatic"

View attachment 4652418

Then, the green -controversial- wavelength ... LEDs currently do not excel here at all... but there are some high CRI CMH lamps:
View attachment 4652424
^^ should have quite some penetration power ^^
Actually this lamp is designed for photography etc as it has a CRI 98 and high irradiance.

Compare this to the irradiance of the sun:
View attachment 4652428

But my fave in terms of spectrum is still the MH & HPS duallamp:
View attachment 4652438
^^ not perfect (could add some 660nm monos, and have more green) but may highly meet the 1:4 ratio of blue:red (400-500nm : 600-700nm) where net photosynthesis is highest ^^

There are some CMH lamps that come very close, or even slightly better, than this but, as you can see, most of these spectral sheets don't even show the complete range! (mind-boggling that a manufacturer of a plant-light de-values its own product - AS IF only PAR would matter!)

TBH I think all CMH or MH/HPS combos make an excellent sunlike spectrum. (LEP/ Plasma/ Mercury vapour as well...)

The sun (for comparison):
View attachment 4652450

I wonder how good LED would fare if one would build a rack that would imitate either a HPS, MH or CMH lamp spectrum-wise? Would they still crank more umols out?

Another thing to consider is that some HID lamps are deadcheap and therefore, can easily be swapped as a means to change the spectrum when needed or beneficial (flower induction, ripening, manipulating internode length etc)

Now I've made a huge case in favour of HIDs but one thing to keep in mind is that HID technology is at the end of its development whereas LED will gain each year- and actually IS already better in terms of raw umol output IF we allow ourselves to compare the raw output of different spectra against each another (actually an apple-vs-orange comparison IMO....)
The Company SunCloak that is the vertical system i used to use attempted to replicate the DE-HPS spectrum minus the ir or even n/ir with their 24k some yrs ago. My plants didn't like it much tbh so we moved to 28k.
Would be interesting to see this done again using the red phosphar diodes to get that length in the red zone.
Basically what we have now is options for a full spectrum from 380-780nm in led. And still awaiting everyone's results on those, none seam to have focused on the full spectrum though. Always lacking somewhere. But diy has the possibilities.
 
Last edited:

Grow Lights Australia

Well-Known Member
Rollitup Advertiser
LOL tbh I've discarded a response involving the subject of kindergarten & diapers.... ähem... I think some of the flames are actually caused by the hangover syndrom alot of smokers underestimate... the laughs n giggles in the evening are offset by an antagonistic neuro-electrical response - causing frustration and sour emotions in the morning if one smokes too heavily... at least, I experience this with me... so from time to time it's good to take a rest until neural tolerance is back to normal again. :peace:

***

The other problem with quantum meters seem that a spikey spectrum seems to introduce a great measuring error:
View attachment 4652328
take it with a grain of salt - as it's just a tiny study with very little hardware.

Ever since @Grow Lights Australia mentioned "Yield Photon Flux" this topic became a rich source of ideas & inspiration. I'm actually wadeing kneedeep in dry college books in order to find out where the potential cut off for Cannabis in the far-red region for photosynthetic photons truly is.

So FR can have help in the acquisition of biomass by contributing photons to photosystem I, initiate hormone/photomorphogenic responses, and also deliver some heat (which may be used to increase a plants metabolism if the growconditions aren't optimal - for example in a stone basement grow....)

But I'm not finding a precise answer, so still looking for clues.... actually these photons 700-800nm theoretically should still be able to excitate/elevate an electron. At least, cyano bacteria can absorb IR photons and do photosynthesis with it - bacteriachlorophyl b has even an absorption peak at 1020nm! (but it may not be the same process as with green landplants)...

But perhaps there is no absorption possible of these wavelengths in the light harvesting complexes of landplants...

To make some sense out of it I've just send Dr. Bugbee a letter about some of these topics so may brain can finally cool down a little XD
perhaps he reads it at the weekend...

Or maybe someone with more knowledge n experience can chime in here... guess the 730nm are a no-brainer but there are also 850nm monos available. Now HPS/CMH cranks out a boatload here. While a high-quality LED emitts twice the PAR umol than HPS - but I'm NOT experiencing that these LED also net twice the weight in harvest. More like 30%. And LED sucks if temps are just somewhere below 20°C...

Maybe IR still has some unexplored properties. As it heats from within, it may be a stimulus? If we look at the sun - there's even much more IR than what a HPS can do, and plants had more than 500mio years to adapt to this radiation.
Then, the natural sun spectrum changes to incorporate more red/darkred signalling the plants to ripen, additionally temps decrease.
All of this is a huge complex bound together and flower induction remains still partially a mystery to even the best scientists ("florigen")

:weed:
So here is what I suspect. Anything over 700nm can't be photosynthesised because it doesn't have enough energy. PS2 excites at 680nm and PS1 excites at 700nm to release their electrons. The PS2 antenna complex captures all light waves that are shorter than 680nm via pigments that absorb each wavelength and then pass that energy on to each other in a chain reaction – all the time losing a small amount of energy – until all photon energy equals lower state 680nm which exites the PS2 reaction centre that releases its own electon. The PS1 antenna complex also does this, but to a lower energy state (700nm), allowing it to also absorb 680nm energy from PS2 via the electron transport chain between PS2 and PS1.

As photon energy can only move in one direction – reducing each time as it bounces – any photon with less energy than 680nm (PS2) or 700nm (PS1) cannot excite the reaction centre to release an electron. Therefore it can't be photosynthesised. This doesn't mean far red light (>700nm) isn't used by the plant, it's just not used for photosynthesis. However, >700nm can cause photomorphogenic responses in plants to accelerate photosynthesis by increasing leaf size (light-gathering sufaace area) and probably in other ways that I can't remember right now.

That's my basic understanding of what's going on.

1597378070762.png

1597377861621.png
 

Kassiopeija

Well-Known Member
Therefore it can't be photosynthesised.
Well, I'd dare to challenge this :cool:

Here in this video Bugbee cited strong empirical evidence and presents it in a proper scientific manner (to make the case):


@ 14:36 it's getting relevant, btw the video is from 2019 (?) so it's content newer than any my books.

(he actually made one tiny mistake and falsely outspoke PS II as I (and vice versa) so he fell for the very same "trick question" he later talked about they usually gave students LMAO If you pay attention to the way he speaks it becomes apparent he actually noticed it right away, as he swiftly paused his speech when coming to PS I! :D)

- Why McCree missed it - although the curve clearly shows that THERE IS a quantum efficiency present up to 750nm and nearly 780nm but only very small. Very ineffective, but BECAUSE PS II capped photosynthesis in McCrees BOGUS tessts.
- Why these photons only work in combination with PAR photons but not standalone.
- Observe the red lighting bolt that states "above700nm".
- Why PAR needs to be expanded to 750nm and "are effective right here" (PS I) - causing the "Emmerson Enhancement effect"... "they can substitute for traditional photons" "all these energy is used to fix CO2"

His picture actually omits the required electronVolt numbers - these are around ~0.8eV for PS II and ~0.5eV for PS I (writing now out the top of my head... but I have the accurate numbers somewhere in my books...). But one thing is certain - PS I doesn't need that much energy to begin with because the electron-transport-chain is shorter. Therefore PS II also is surrounded by more Light Harvesting Complexes.

The pics you posted are a simplification that are a good example of the electron-transport-chain but where we have to look at are actually the light-harvesting-complexes (LHC) which are filled with various pigments - not only chlorophyl but also carotenoids etc. I can't find how the FR photons are encaptured for photosynthesis but the empirical evidence (increased photosynthesisrate) cannot be attributed to a photomorphogenic effect, as these are not transmitted by chloroplasts but instead phytochromes.

If you look at the ordinate of your second pic you'll see that the necessary voltage to excitate an electron is even less than what a 700nm photon carries. Actually a single photon theoretically could drive the whole process alone (energywise) IF there wouldn't be a huge loss due to the electron jumping through this chain or having to reach a state of stable resonance within the antenna-complexes until the chain is open again, or this quantum law about "particle-partners" wouldn't be in place (but it is - as the modern physics quantum standard model dictates specific symmetry)

The losses are described to be ~70% for a red photon and ~81% for a blue photon (comparing the photon-energy vs sucrose biomasss acquisition - rest is loss.

Secondly, when scientists measure the absorption spectra of chlorophyll in vitro they first need to extract it but the solvent itself changes the absorption spectrum a little. This is why p700 stops at 700nm - but in vitro in ethanol! And one cannot measure that in a single leaf in vivo as there are hundreds of pigments consisting of various chlorophyll-subtypes, which all have a slightly different absorption-maximum, and each RC is basically surrounded by chlorophylls & carotenoids.

This diagram gives also a small hint of changed absorption rate when the pigment is extracted:
leaf-absorbtion.png
Here is what McCree did use:
Prisma-Photometer.png
(Bottom text: "Yellow light, wavelength approx. 580nm, does penetrate nearly unhindered through the chlorophyll-solvent.)

Thirdly, quantum effects can also change things dramatically, when the valence orbitals are in closer proximity of one another, less energy is needed.
To cite an extreme example with the absorptionmaximas of bacteriachlorophyl a:
In vitro: 780nm
In vivo PSII: 800nm
In vivo PSI: 850nm [!]
Screenshot_20200815-084451.png
^^ red is in vitro, blue in vivo ^^
About +50nm median error! If that happens within a plants leave under a narrowband/blurple LED the absorption rate will go down the drain... but a sunlike spectrum won't face this problem much as it delivers everywhere (which also doesn't concentrate its photons at the very same pigments...)

I do therefore believe that FR photons 700-760nm do add to photosynthesis and identify this as primairy reason why modern state LED won't pull twice the harvest than HID - and I've seen simple HPS do 1.5g/kWh but never LED 3.0g/kWh, and perhaps master HID growers like @Renfro or @Sedan do set the bar even higher?

Last but not least, FR/IR has even another benefit to "darksprouter" plants:
It increases germination rates when seeds are drenched in a constant darkred low light, somewhere around 700-1000nm, that's scientifically proven, but not many people know that.

And since the FR photons are energetically very efficient to create and penetrate very deep you may want to include as many of them in your boards as possible. Which can be problematic as it causes stretching on shade-avoider-plants. But that can be dealt with -and @Randomblame stated that in the other place already- counter it with UVA:
High Intensity Phytochrome 730nm reaction.jpg
^^ Upper text: "Effect-spectrum of a High-Intensity-Reaction: Depression of hypocotyl-stretching by etioliated sprouts...." ^^
to explain:
Dicotyl-plants like hemp naturally stretch always their "mainstem" below the cotyledons as a means to overcome rivalling grass and reach full daylight. This stretching can be countered with above spectrum, so you can offset constant FR with UV.
And perhaps even put some more FR diodes on a separate channel to be able to initiate the EOD and/or go full mongo on FR when either growing shade-plants or when stretching isn't possible anymore (bulking/ripening).

But that may be tricky to find the right balance as this high-intensity-reaction is sitting on a plateau reached by 730nmn lightstrength & length of exposure:

HIR.png
 

Attachments

Last edited:

hybridway2

Well-Known Member
So here is what I suspect. Anything over 700nm can't be photosynthesised because it doesn't have enough energy. PS2 excites at 680nm and PS1 excites at 700nm to release their electrons. The PS2 antenna complex captures all light waves that are shorter than 680nm via pigments that absorb each wavelength and then pass that energy on to each other in a chain reaction – all the time losing a small amount of energy – until all photon energy equals lower state 680nm which exites the PS2 reaction centre that releases its own electon. The PS1 antenna complex also does this, but to a lower energy state (700nm), allowing it to also absorb 680nm energy from PS2 via the electron transport chain between PS2 and PS1.

As photon energy can only move in one direction – reducing each time as it bounces – any photon with less energy than 680nm (PS2) or 700nm (PS1) cannot excite the reaction centre to release an electron. Therefore it can't be photosynthesised. This doesn't mean far red light (>700nm) isn't used by the plant, it's just not used for photosynthesis. However, >700nm can cause photomorphogenic responses in plants to accelerate photosynthesis by increasing leaf size (light-gathering sufaace area) and probably in other ways that I can't remember right now.

That's my basic understanding of what's going on.

View attachment 4652925

View attachment 4652924
Nice post. Here's my thing, whether we call it non-photosynthetic or primarily morphological.
From my experiences, i feel you can't have one w/o the other & still be in optimal territory. Therefore IMO,
N/ir is a must. Because we know it triggers the EmmersonEffect as well as increases plant size, stretch, stalk & leaf thickness, ect.. while still being visible (barely to us) & w/i means to produce efficiently enough to use. 730/40 is doing the trick.
Yes, i think there is still unlocked potential up to 850nm.
I too studied about pr1 + 2 but do not recall the details like you. Good job at getting scientific on it bud! We soooo need that. Even if theoretical.
Biggest thing I gained from learning about ir was how IR wavelengths, the mere presence (not the wasted heat emitted from the diode), excites the leaf or bio-mass cells to bounce around, off each other, creating friction, in turn heating up the leaf. Creating a slightly higher leaf temp then ambient if all goes well. Increasing transpiration & overall vitality/beastliness of the plant.
Yes that is all explained through pr1 +2 but I'm on laymens terms now since i gave up on studying to understand the exact science of it all. Made my head spin.
Quote "This doesn't mean far red light (>700nm) isn't used by the plant, it's just not used for photosynthesis. However, >700nm can cause photomorphogenic responses in plants to accelerate photosynthesis by increasing leaf size (light-gathering sufaace area) and probably in other ways that I can't remember right now."
Am i wrong or doesn't this all equal out to be advantageous as well as more natural. Benefitting many growers whom are working with the blue ranges in higher levels then 15% from 400-500 as many manufactures provide the 35k-4k spectrum with the 660. (HE Spectrum).
You need it. Some type of ir 730 up to 850 to get the most from your plants. Maybe not even as much as some think. Just there.
 
Last edited:

mauricem00

Well-Known Member
I have discussed with others many times that the strong points of led are truly not being utilized, most likely due to cost. A company with true science and research background will come along and analyze sunlight nm by nm and use the appropriate diodes to produce a true solar spectrum.
Till then the believers will continue to settle on spectrum deficiency in the name of saving a few watts per umole
LEDs can match the portion of the solar spectrum our plants use.but it would be extremly expensive and some of the diodes needed have short life expediencies . i have been looking into why HPS flowers so well.it seems the plants shade avoidance system causes major changes in the plant. in this operating mode the plant uses green light to drive photosynthesis as the plant adapts to low light environment and use available light more efficiently. fascinating how complex our plants are
 

Mohican

Well-Known Member
@Kassiopeija - Thanks for posting the solar spectrum. I have been searching for a reference for a long time.

What would be awesome to see is the spectrum from 2K feet up on Maui, Sea level in Huntington Beach, a mile high in Denver (away from the brown cloud), and something from the Hindu/Kush region.

This thread rocks!

I have grown LED mostly with Kessil's tuned lights. I saw a giant increase in growth when I used a light mover. I don't have a dedicated grow lab yet so I stick mainly to the outdoors:

BCRainbowDec03.png

Cheers,
Mo
 

Kassiopeija

Well-Known Member
so your saying you can tell what light was used to grow the bud you smoked? no way.
- Outdoor plants in soil (not pot): typically less opaque light green leaves designed to let the suns brutal 1700-2000ppfd shine through.
- HPS: massy expanded big buds but less dense, with less trichome density, and less elongated trichs, faster ripening
- MH/CMH: small nugs with alot of frost
- white CRI LED: heavy dense buds with more trichs than HPS but less than MH
- Flurosz: extremely healthy & beautiful overall plants (actually I wanted to provide a link here but my booksigns seemed to have dropped that, it's been a growreport from a guy growing with about 1000w Fluorescent lamps, that had extremely impressive looking plants - I do ASSUME that the great surface of CFLs (t5, t8 to do away with individual "hotspots" so a plant has it more easy.)

But ultimately, it's the spectrum causing this, and since similar lamp-types can have different spectra, it's not as clear-cut as it may appear as above listed. Not at all... more like my own thumb-rule. One has to pick up the spectrum first and then go from there.
But with some sensibilization in that region the differences become obvious after some time...

Guess the current most examples are reports from growers which add UVA to their LED setup and experience a great increase in trichome density. Clearly visible in the trich shots... not a single report where UV caused less trichs.
@Kassiopeija - Thanks for posting the solar spectrum. I have been searching for a reference for a long time.

What would be awesome to see is the spectrum from 2K feet up on Maui, Sea level in Huntington Beach, a mile high in Denver (away from the brown cloud), and something from the Hindu/Kush region.

This thread rocks!

I have grown LED mostly with Kessil's tuned lights. I saw a giant increase in growth when I used a light mover. I don't have a dedicated grow lab yet so I stick mainly to the outdoors:

View attachment 4654705

Cheers,
Mo
Nice plant & pic Mo :weed:

Well, I guess the suns true spectrum can only be observed from space (~5500K) as the atmosphere and the place of the sun in the sky changes alot.

Within the attached files you'll find some information about natural UVB occurences.

The UV rating in Tibet occasionally exceeded the scale (although that is made for humans... but I take it Cannabis evolved with lots of UV)
The other .pfd is about a scientific lamp designed to mimic the suns UV spectrum curve - under normal weather (comparing Florida) and then they shifted it some nm more towards UVB to simulate what happens to the spectrum if, e.g. a bird drops a seed out of its natrual habitate onto a mountain, where UV will be unnaturally high for such a plant.

Anyway, here are a few different sun spectra:

Blue sky in an ice landscape: (snow/ice is also identified in the Tibetan .pdf to be a major contributing factor to UV)
Abb-2_Spektrum-blauer-Himmel-25000-K_800er.jpg
^^ extremely blueshifted ^^

A cloudy/foggy day:
Abb-1_Spektrum-nebeliger-Wintertag-7000-K_800er.jpg
^^ this spectrum is actually giving me a headache, considering the slight breakin of yellow, plus cyan/blue is so pronounced... but that's how it is, the molecules in our atmosphere shape & influence what light passes through - but still, it is the most balanced of the 4 ^^


In a forrest (with still some direct light exposure:
Abb-3_Spektrum-blauer-Himmel-25000-K_800er.jpg
^^ green pronounced, so there is alot of reflected light ^^

Dawn/ dusk:
Abb-4_Spektrum-Sonnenuntergang-3300-K_800er.jpg
^^ sending plants to sleep; but also awakening them??? ^^
 

Attachments

hybridway2

Well-Known Member
Well, I'd dare to challenge this :cool:

Here in this video Bugbee cited strong empirical evidence and presents it in a proper scientific manner (to make the case):


@ 14:36 it's getting relevant, btw the video is from 2019 (?) so it's content newer than any my books.

(he actually made one tiny mistake and falsely outspoke PS II as I (and vice versa) so he fell for the very same "trick question" he later talked about they usually gave students LMAO If you pay attention to the way he speaks it becomes apparent he actually noticed it right away, as he swiftly paused his speech when coming to PS I! :D)

- Why McCree missed it - although the curve clearly shows that THERE IS a quantum efficiency present up to 750nm and nearly 780nm but only very small. Very ineffective, but BECAUSE PS II capped photosynthesis in McCrees BOGUS tessts.
- Why these photons only work in combination with PAR photons but not standalone.
- Observe the red lighting bolt that states "above700nm".
- Why PAR needs to be expanded to 750nm and "are effective right here" (PS I) - causing the "Emmerson Enhancement effect"... "they can substitute for traditional photons" "all these energy is used to fix CO2"

His picture actually omits the required electronVolt numbers - these are around ~0.8eV for PS II and ~0.5eV for PS I (writing now out the top of my head... but I have the accurate numbers somewhere in my books...). But one thing is certain - PS I doesn't need that much energy to begin with because the electron-transport-chain is shorter. Therefore PS II also is surrounded by more Light Harvesting Complexes.

The pics you posted are a simplification that are a good example of the electron-transport-chain but where we have to look at are actually the light-harvesting-complexes (LHC) which are filled with various pigments - not only chlorophyl but also carotenoids etc. I can't find how the FR photons are encaptured for photosynthesis but the empirical evidence (increased photosynthesisrate) cannot be attributed to a photomorphogenic effect, as these are not transmitted by chloroplasts but instead phytochromes.

If you look at the ordinate of your second pic you'll see that the necessary voltage to excitate an electron is even less than what a 700nm photon carries. Actually a single photon theoretically could drive the whole process alone (energywise) IF there wouldn't be a huge loss due to the electron jumping through this chain or having to reach a state of stable resonance within the antenna-complexes until the chain is open again, or this quantum law about "particle-partners" wouldn't be in place (but it is - as the modern physics quantum standard model dictates specific symmetry)

The losses are described to be ~70% for a red photon and ~81% for a blue photon (comparing the photon-energy vs sucrose biomasss acquisition - rest is loss.

Secondly, when scientists measure the absorption spectra of chlorophyll in vitro they first need to extract it but the solvent itself changes the absorption spectrum a little. This is why p700 stops at 700nm - but in vitro in ethanol! And one cannot measure that in a single leaf in vivo as there are hundreds of pigments consisting of various chlorophyll-subtypes, which all have a slightly different absorption-maximum, and each RC is basically surrounded by chlorophylls & carotenoids.

This diagram gives also a small hint of changed absorption rate when the pigment is extracted:
View attachment 4654079
Here is what McCree did use:
View attachment 4654081
(Bottom text: "Yellow light, wavelength approx. 580nm, does penetrate nearly unhindered through the chlorophyll-solvent.)

Thirdly, quantum effects can also change things dramatically, when the valence orbitals are in closer proximity of one another, less energy is needed.
To cite an extreme example with the absorptionmaximas of bacteriachlorophyl a:
In vitro: 780nm
In vivo PSII: 800nm
In vivo PSI: 850nm [!]
View attachment 4654144
^^ red is in vitro, blue in vivo ^^
About +50nm median error! If that happens within a plants leave under a narrowband/blurple LED the absorption rate will go down the drain... but a sunlike spectrum won't face this problem much as it delivers everywhere (which also doesn't concentrate its photons at the very same pigments...)

I do therefore believe that FR photons 700-760nm do add to photosynthesis and identify this as primairy reason why modern state LED won't pull twice the harvest than HID - and I've seen simple HPS do 1.5g/kWh but never LED 3.0g/kWh, and perhaps master HID growers like @Renfro or @Sedan do set the bar even higher?

Last but not least, FR/IR has even another benefit to "darksprouter" plants:
It increases germination rates when seeds are drenched in a constant darkred low light, somewhere around 700-1000nm, that's scientifically proven, but not many people know that.

And since the FR photons are energetically very efficient to create and penetrate very deep you may want to include as many of them in your boards as possible. Which can be problematic as it causes stretching on shade-avoider-plants. But that can be dealt with -and @Randomblame stated that in the other place already- counter it with UVA:
View attachment 4654154
^^ Upper text: "Effect-spectrum of a High-Intensity-Reaction: Depression of hypocotyl-stretching by etioliated sprouts...." ^^
to explain:
Dicotyl-plants like hemp naturally stretch always their "mainstem" below the cotyledons as a means to overcome rivalling grass and reach full daylight. This stretching can be countered with above spectrum, so you can offset constant FR with UV.
And perhaps even put some more FR diodes on a separate channel to be able to initiate the EOD and/or go full mongo on FR when either growing shade-plants or when stretching isn't possible anymore (bulking/ripening).

But that may be tricky to find the right balance as this high-intensity-reaction is sitting on a plateau reached by 730nmn lightstrength & length of exposure:

View attachment 4654156
- Outdoor plants in soil (not pot): typically less opaque light green leaves designed to let the suns brutal 1700-2000ppfd shine through.
- HPS: massy expanded big buds but less dense, with less trichome density, and less elongated trichs, faster ripening
- MH/CMH: small nugs with alot of frost
- white CRI LED: heavy dense buds with more trichs than HPS but less than MH
- Flurosz: extremely healthy & beautiful overall plants (actually I wanted to provide a link here but my booksigns seemed to have dropped that, it's been a growreport from a guy growing with about 1000w Fluorescent lamps, that had extremely impressive looking plants - I do ASSUME that the great surface of CFLs (t5, t8 to do away with individual "hotspots" so a plant has it more easy.)

But ultimately, it's the spectrum causing this, and since similar lamp-types can have different spectra, it's not as clear-cut as it may appear as above listed. Not at all... more like my own thumb-rule. One has to pick up the spectrum first and then go from there.
But with some sensibilization in that region the differences become obvious after some time...

Guess the current most examples are reports from growers which add UVA to their LED setup and experience a great increase in trichome density. Clearly visible in the trich shots... not a single report where UV caused less trichs.

Nice plant & pic Mo :weed:

Well, I guess the suns true spectrum can only be observed from space (~5500K) as the atmosphere and the place of the sun in the sky changes alot.

Within the attached files you'll find some information about natural UVB occurences.

The UV rating in Tibet occasionally exceeded the scale (although that is made for humans... but I take it Cannabis evolved with lots of UV)
The other .pfd is about a scientific lamp designed to mimic the suns UV spectrum curve - under normal weather (comparing Florida) and then they shifted it some nm more towards UVB to simulate what happens to the spectrum if, e.g. a bird drops a seed out of its natrual habitate onto a mountain, where UV will be unnaturally high for such a plant.

Anyway, here are a few different sun spectra:

Blue sky in an ice landscape: (snow/ice is also identified in the Tibetan .pdf to be a major contributing factor to UV)
View attachment 4654947
^^ extremely blueshifted ^^

A cloudy/foggy day:
View attachment 4654946
^^ this spectrum is actually giving me a headache, considering the slight breakin of yellow, plus cyan/blue is so pronounced... but that's how it is, the molecules in our atmosphere shape & influence what light passes through - but still, it is the most balanced of the 4 ^^


In a forrest (with still some direct light exposure:
View attachment 4654948
^^ green pronounced, so there is alot of reflected light ^^

Dawn/ dusk:
View attachment 4654949
^^ sending plants to sleep; but also awakening them??? ^^
Great, informative posts! Thank you for taking the time to help.
 

hybridway2

Well-Known Member
From what I have seen, i have a tough time growing w/o n/ir unless the spectrum is slammed with 660nm. The only light i have like that is the Bar-8 PROTOTYPE. IT also has acrylic/plastic diffusion covers in which i feel play a large part in successful growing under HO, LED.
With this light it becomes harder to distinguish between the plants getting n/ir to that specific light. Sure, the morphological responses is slightly different. I needed to do it over n over to finally notice. That light is your Basic HE Spectrum used by many except its got about 22% more 660 then the normally accepted, popular HE spectrum (35-4k + 660nm.)
If others felt they would be able to accomplish the same type of plant response is beyond me. There in not nearly enough 660 in many of the new lights to combat that 450 spike in 35 or 4 k. This leads to Bosnia effects in some strains I'm seeing. Very low stretch that in turn causes a suffering in yeilds as well as bag appeal.
I personally would like to add some monos in the 750-810 ranges. Especially now that UVA is going to be much more pronounced in my garden.
Not to jump off exact topic here but could someone explain to me why led companies & diy'rs alike all seam to neglect 470-480nm.? I mean its only the color of our sky, why wouldn't that become the blue to fill before jumping to much else? Fill your primary par spectrum before focussing outside of it, no? Or both. I can say i love having 470nm in my lights. Spring time in there. I've heard of stomata opening more from this range being used. Can only imagine the synergistic effects it has.
W/O it, one is growing with what scientists describe as "The Cyan Gap".
IMO, Usually, if its good for humans, its good for our plants. The basics of course.
 
Last edited:

Kassiopeija

Well-Known Member
Not to jump off exact topic here but could someone explain to me why led companies & diy'rs alike all seam to neglect 470-480nm.? I mean its only the color of our sky, why wouldn't that become the blue to fill before jumping to much else? Fill your primary par spectrum before focussing outside of it, no? Or both. I can say i love having 470nm in my lights.
So white CRI diodes focus on the 2 most efficient absorption peaks of both chlorophyl a+b - which is called the "Soret peak"
220px-Chlorophyll_spectrum.png
This is were absorption of PS light is very strong - but focusing solely on this may exert a high burden at the very first leaf were the full radiation hits.
Scientists have made some studies (with blue, green and red wavelengths) and arrived at the conclusion that at 20% blue + 80% red the photosystems run best. If, for example, one would exclude blue completely out of the spectrum and focus only on the most efficient photonpump (660nm) then plants wouldn't grow well at all...

And since Cannabis grows more like a bush and not liek a small low plants we'll have to bring a light to the table which enlights more than just the top leaves.

Cyan at 490nm is actually critical for human contrast seeing, under some LED lights (such as Sanlight) leaves get a strange color... guess it has to do with the conversion materials of why there is always this "cyan gap".

Plants build metabolites to catch some of these wavelengths and some of these substances are actually quite powerful health anti-oxidants, as you can see here:
Fig9.png
ofc, irrelevant for Cannabis, as it's combusted anyway - but for vegetables... they also have a tendency to make food more "bitter" esp. on plants that don't need that much sun.
 
>
Top