More THC testing – UVA vs UVB vs near-UV

Grow Lights Australia

Well-Known Member
Hey GLA thanks for pointing this out, I've not heard of this before but spent the mourning with reading... actually the link @twistedwords provided held some really good & well-researched articles, esp. on some of the physical aspects of light & spectrum. Unfortunately the guy doesn't differentiate between the different "buildplans" prevalent in todays plants, as the response to spectra may alter.... but that could be the only thing I've found so far on that...

Do you perhaps know more about what happens with 360-400nm photons when they hit the plant? Do they reach specific (which?) antennae-complexes and are able to participate to exzitate an electron in PS II? We know that FR is able to do this in PS I, and because these photons do actually partake in photosynthesis they actually are a part of "PAR". I wonder if the same could be said from violett rays?

BTW how do you manage to have the green spike in your spectrum? I've looked at lots of LED spectras lately, and there exists basically 2 different "types", one that basically has a huge gap between 490-580, and those that fill that at least with 30-50% of the max. But yours is actually even a bit more pronounced, you have a green mono there in the mix?
Hey Kassiopeija, the green hump is a function of the white phosphor LEDs we use, mainly the Nichia CRI90 2700K which has a dip between 530nm and 560nm, as well as the Seoul Semiconductor CRI95 6500K, pictured below.
Screen Shot 2019-04-30 at 16.16.35.png
We mix this LED in for the near-UV and cyan boost, but it also has a little uptick around 500nm.

Right, easy question out of the way first :D As you know I am not a botanist nor even a chemist, so this is just my understanding of the process that may or may not be entirely complete (or even correct). As always I'm happy for anyone to correct me.

So my understanding is PSII chlorophyll is made up of 50% A and 50% B, whereas PSI is 100% A, meaning Chlorophyll A has a higher weighting than B across the leaf, which you can see in the McCree Curve.

Finding an accurate graph of photosynthetic absorption isn't as easy as it looks, as there appear to be variations of the same graph. I often wondered about this until I read something the other day which might explain it: chlorophyll absorption peaks change depending on which solution they are in. For scientific purposes you need to dissolve chlorphyll in a solution to measure its absorption, but if you dissolve it in a solvent such as alcohol or some type of ether, then the absorption peaks change slightly because the chlorphyll binds with the solvent (non-free chlorophyll) vs chlorophyll dissolved in an aqueous solution (water) which is free chlorophyll.

Non-free Chlorophyll A has an absorption peak at 430nm. Free Chlorophyll A has an absorption peak at 465nm. The secondary peaks for Chl-A are 660nm in solvent and 730nm in water – right in the Far Red region.

Plants don't grow in solvents, they grow in moist air and are mostly made up of water!

The citation I have for all this is here: http://science.trigunamedia.com/sacred-geometry-not-a-leeway-to-junk-science/

Interestingly if you subscribe to the above theory, then the Chl-A "secondary" peak at 730nm is actually higher than the "primary" peak at 465nm, which may go some way to explaining why Far Red is so important for photosynthesis (in addition to, or perhaps in main part due to the Emerson Effect – but I would need to read more into).

If we ignore the theory that the graphs are wrong and just look at a typical Chlorophyll absoprtion graph such as below, we can see that Chlorophyll A has a secondary absorption peak round 400-405nm that is at least as important as the red peak at 660nm (or 730nm, whichever peak you subscribe to). Although it does depend on the graph you use. Here are two that highlight what I am saying.

1596097974180.png
1596097416199.png

I guess it depends on which graph you use, but it appears that Chl-A does absorb significant amounts of 360-400, peaking at 405nm, and that being the most important pigment in PSI and PSII it does drive photosynthesis. It's also interesting to look at the caratenoid profile which also shows absorption throughout the same range and which we know also drives PSI and PSII.

Interestingly, Chl-B peaks right in the cyan region, but very few LEDs have a good amount of cyan.

There is also something else missing fropm this debate,and that is the effect that photomorphogenic response has on photosynthesis. Shade avoidance is a good example. As a plant goes into shade avoidance, leaves increase in overall surface area (but get thinner, as the amount of biomass remains similar) and these larger leaves are able to capture more light. This makes up for the lower amount of light in the shade canopy and enables the plant to grow taller faster to reach the light canopy.

Now if it were possible to kick a plant into shade avoidance in full sun would this also accelerate growth? Or would it simply stress the plant? And if it did stress the plant, would it be possible to get the best of both worlds: faster growth and higher cannabinoid content?

I don't know. I kind of just thought of that then!
 

Attachments

Grow Lights Australia

Well-Known Member
Is there much information out there, separating UVA and UVB? It seems most of the time the two are intermixed in some level, but being as there is more damage potential with UVB, what about just running UVA vs UVA+UVB?

I know there is a lot of research into Far Red right now (Seems to have a lot of shaping ability), been reading up a lot on what Dr. Bruce Bugbee has to say on the topic, but in my limited experience it seems any time someone talks about UV spectrums in general it seems to be nearUV-UVB. Obviously noone wants any 100-290 C in there.
That is what we are trying to prove. That you can get similar effects using UVA or near-UV to UVB. The advantages are obvious: less energy required to make near-UV, less potential damage to plants if you accidentally overdose, longer life for LEDs, and less risk to humans working under them.
 

Grow Lights Australia

Well-Known Member
Not a problem. IMHO I keep seeing everyone trying to use a very old study on plant spectrum done in the 1970's. No one knows if that old graph is even correct. It was theoretical and not done with applied lighting because it doesn't exist. I am not picking on your lights, I am going by many years of experience.

Yes I did read your thread and your results from the analysis, but as you pointed out the grower said that it could have been from too much UV which I have seen as well with experience.

Have you tried a different spectrum of your own? One that you came up with instead up journals? Sometimes outside the box works.
I agree. And I have tried to touch on this above. But I would still be interested to know how you quantify your results.

With regards to our spectrum, we did come up with it ourselves. There are not many (if any?) manufacturers doing what we are doing with near-UV. At least there weren't when we started this. Everything was about "UVB" or deep (350ish) UVA.

We are limited to what is on the market and is cost-effective for what we are doing, but we're also playing around with a few things at the moment. I would like to post a photo of some vegging plants that one of our test growers has shared with us, but I can't go into many details other than this. What we have seen is excellent vegetative and flowering growth and we will soon be posting up results of cannabinoid testing using the same strain by one of the same growers as on Page 1 of this thread.

IMG_3096.JPG

The grower said he was very happy with the results. You can probably see by the light that it is not your average "full spectrum" white-phosphor LED grow, but it is a predominantly white board. Incidentally, this light is 2400K and there is very little stretch.
 

hybridway2

Amare Shill
I agree. And I have tried to touch on this above. But I would still be interested to know how you quantify your results.

With regards to our spectrum, we did come up with it ourselves. There are not many (if any?) manufacturers doing what we are doing with near-UV. At least there weren't when we started this. Everything was about "UVB" or deep (350ish) UVA.

We are limited to what is on the market and is cost-effective for what we are doing, but we're also playing around with a few things at the moment. I would like to post a photo of some vegging plants that one of our test growers has shared with us, but I can't go into many details other than this. What we have seen is excellent vegetative and flowering growth and we will soon be posting up results of cannabinoid testing using the same strain by one of the same growers as on Page 1 of this thread.

View attachment 4639130

The grower said he was very happy with the results. You can probably see by the light that it is not your average "full spectrum" white-phosphor LED grow, but it is a predominantly white board. Incidentally, this light is 2400K and there is very little stretch.
Did you say The voltage not matching is the reason for not using Opti's all the way?
 

Prawn Connery

Well-Known Member
Personal grow knowledge (30 years) as it works. I struggled with much more blue and short stumpy plants. One day later dialing it down to 15% and it works.

Rosenthal didn't have what we know know.

800-1000 PPFD can be too much during flowering it depends on which light cycle you are using...Which one are you using? How far are your lights from the canopy top and bottom?

Also what is your light intensity reading?

Much more than PPFD...



Hey mate, I've been growing indoors for 20 years and over 30 including outdoors and I helped develop these lights based on successive LED grows between myself and other growers who helped trial them. What do you grow under and what do you use to measure your spectrum? It looks like @Grow Lights Australia has asked you this but I didn't see you answer. I shoot for around 900-1000 PPFD and that works for me. I grow mainly sativas and they easily handle that amount of light.
 

Prawn Connery

Well-Known Member
I agree. And I have tried to touch on this above. But I would still be interested to know how you quantify your results.

With regards to our spectrum, we did come up with it ourselves. There are not many (if any?) manufacturers doing what we are doing with near-UV. At least there weren't when we started this. Everything was about "UVB" or deep (350ish) UVA.

We are limited to what is on the market and is cost-effective for what we are doing, but we're also playing around with a few things at the moment. I would like to post a photo of some vegging plants that one of our test growers has shared with us, but I can't go into many details other than this. What we have seen is excellent vegetative and flowering growth and we will soon be posting up results of cannabinoid testing using the same strain by one of the same growers as on Page 1 of this thread.

View attachment 4639130

The grower said he was very happy with the results. You can probably see by the light that it is not your average "full spectrum" white-phosphor LED grow, but it is a predominantly white board. Incidentally, this light is 2400K and there is very little stretch.
LOL! I recognise those plants. It's a little bit blurple but is also true full-spectrum white. I won't say anymore but the growth surprised me.
:bigjoint:
 

dbz

Well-Known Member
LOL! I recognise those plants. It's a little bit blurple but is also true full-spectrum white. I won't say anymore but the growth surprised me.
:bigjoint:
I find with lights that utilize near uv and uva along with strong reds you tend to see more blurple in the pics but when physically working with the plants they seem to have a more whitish light. I think the result in the pictures is spectrum that we aren't seeing ourselves but the camera captures.

The IR and UV just don't show up to us when looking at the plants which make pictures a little less clear than being there physically with the plant.
 

Grow Lights Australia

Well-Known Member
I find with lights that utilize near uv and uva along with strong reds you tend to see more blurple in the pics but when physically working with the plants they seem to have a more whitish light. I think the result in the pictures is spectrum that we aren't seeing ourselves but the camera captures.

The IR and UV just don't show up to us when looking at the plants which make pictures a little less clear than being there physically with the plant.
Yes. I've also seen those lights and they have a pinkish hue but are still white. I have the spectographs here and that one is around CRI 83 and I was slightly off as it's 2500K.
 

Kassiopeija

Well-Known Member
Obviously noone wants any 100-290 C in there.
plants have an extreme stomatal opening response when exposed to UVB:
F4.medium.gif
the response peaks at 280nm... I think this is perhaps due to a survival-response when exposed to a potentially harmfull heavy-energy radiation - to opens stomatas to maximum and thereby trade loss-of-water with increased cooling as a means of self-protection.
Nevertheless, it seems like blue light can greatly do this job, too... so there is little need to expose plants to a full daytimes phase to UVB - as that would also only trigger a heavy adaptation-phase afterwhich UVB wouldn't be that efficient in causing a physiological plantreaction...

Hey Kassiopeija, the green hump is a function of the white phosphor LEDs we use, mainly the Nichia CRI90 2700K which has a dip between 530nm and 560nm, as well as the Seoul Semiconductor CRI95 6500K, pictured below.
the spectrum you posted is very interesting in that it resembles natural light to some extend:

this is a measurement of direct sunlight which passed through a light forrest canopy:
Abb-3_Spektrum-blauer-Himmel-25000-K_800er.jpg
^^ so this is the spectrum that bushes get in their middle, or the plants at the bottom of the forrest, but not cannabis

here's the direct sunlight graphs, from a region with high UV output (snow reflection) - one can see the affinity (sunlight) from specific "dents" (basically every color has its own distinct dent...):
Abb-2_Spektrum-blauer-Himmel-25000-K_800er.jpg
^^ it's why the sun is ~5500k in colour and plants can deal naturally with a great amount of high-energetic rays...

I think that particular diode seems to emanate light which is like a good combination of both these spectra... However, I cannot use them, as they contain blue which means leaves will adjust themselves towards that light... I need 8-16 550nm for sidelight/ intra-canopy light addition... but the monos aren't efficient and given the fact that 550nm transpierces alot through leaves, one could must up quite some strength to see results/"photonic input".

I want to combine them with 8-16 630nm, 660nm & 730nm.... so the sidelight wavelengths would be differentially captured by either the first, second, 1-5th leave (grossly estimated), or equally spread throughout the growroom. Thereby decreasing lightstress on individual leaves and penetrating actually much deeper.... NOT with raw blunt force! shuning trauma, instead going the gentle spectrum-intelligent way! :D

Did you take a look at the other companies diodes? They claim to have these broadband-monochromatic diodes that, e.g. engulf the whole red and even some far-red and thereby help avoid these monochromatic gaps. I wonder if such a broadband diode exists for green & yellow?

So my understanding is PSII chlorophyll is made up of 50% A and 50% B, whereas PSI is 100% A, meaning Chlorophyll A has a higher weighting than B across the leaf, which you can see in the McCree Curve.

Finding an accurate graph of photosynthetic absorption isn't as easy as it looks, as there appear to be variations of the same graph. I often wondered about this until I read something the other day which might explain it: chlorophyll absorption peaks change depending on
welll all I can tell you here is that there are many so-called chlorophyll subtypes - which have slightely altered absorption peak, and these are actually labelled accordingly, e.g. Chl A672. They have a slightely different molecular structure but the central complex remains the same. This is one way how plants can respond to the offered light spectrum & optimize the absorption. So this can help to explain why alot of the quantitised data from studies do have some natural flux to it - esp. in general with plants or living things.

Interestingly if you subscribe to the above theory, then the Chl-A "secondary" peak at 730nm is actually higher than the "primary" peak at 465nm, which may go some way to explaining why Far Red is so important for photosynthesis (in addition to, or perhaps in main part due to the Emerson Effect – but I would need to read more into).
I would like to get to the bottom of what actually causes this Emerson-effect? Like the plant internal mechanism that is reponsible for the increase in raw photosynthesis? My understanding of how the electrons are shuffled around in the two photosystems may hint towards a better synchronization of PS II with I and a higher PS rate because of faster electron-transport or lesser waste as heat. However, this is actually something which also happens in the antenna-complexes, and that seems to be such a complex structure, that it seems next to impossible to do "some math" on it to get it right...

I've had voices yelling at me claiming the conventional Samsumg white CRI diodes do already trigger this E.-effect at maximum and any addition with supplemenal FR may actually further decrease the efficiency, meaning the optimized balance between PS II & I gets disrupted. HOWEVER, if spectrum is responsible for this harmonization, then this may change significantly after passing the first leaf. We cannot "timefreeze" the spectrum...

So the premier goal is to actually offer whatever photons we can to increase leaf-photosynthesis, and this should hold true for all leaves the plants did grow - and not just some topleaves , because the lamp emanates a light that is greatly absorbed int he first 30% of a single leaf:

Sylvania.png
(Sylvania Linear)

^^ leaf bleach at close range ??? Compared to other technologies in creating light, this spectrum looks like less-rich than the others...
There is also something else missing fropm this debate,and that is the effect that photomorphogenic response has on photosynthesis. Shade avoidance is a good example. As a plant goes into shade avoidance, leaves increase in overall surface area (but get thinner, as the amount of biomass remains similar) and these larger leaves are able to capture more light. This makes up for the lower amount of light in the shade canopy and enables the plant to grow taller faster to reach the light canopy.

Now if it were possible to kick a plant into shade avoidance in full sun would this also accelerate growth? Or would it simply stress the plant? And if it did stress the plant, would it be possible to get the best of both worlds: faster growth and higher cannabinoid content?

I don't know. I kind of just thought of that then!
if a leaf doesn't get enough light-saturation for an extended period of time - a plant may withdraw it. So to simply help deliver more photons onto these leaves may prevent that and also help diminish or minimize some of the photomorphogenetic responses from leaves which are usually exposed to such a spectrum.
So I wonder what would happen if we took 5 healthy-green cannabis leaves and placed them each 5cm apart in a row and blasted a lamp at them and measured what kind of spectrum remained after each consecutive crossing of a leaf? With the goal to increase the total net light-saturation of all 5 leaves.

But I do believe that a plant that is exposed to increased amounts of far-red photons is always going to stretch considerably, have long internodes... and while that may not seemed wanted by indoor growers, the exposition to this type of light always seemed to increase dry-harvest weight. I have tried S-HPS with an increased blue output but it didn't change the stretch at all...
 

Rocket Soul

Well-Known Member
plants have an extreme stomatal opening response when exposed to UVB:
View attachment 4640035
the response peaks at 280nm... I think this is perhaps due to a survival-response when exposed to a potentially harmfull heavy-energy radiation - to opens stomatas to maximum and thereby trade loss-of-water with increased cooling as a means of self-protection.
Nevertheless, it seems like blue light can greatly do this job, too... so there is little need to expose plants to a full daytimes phase to UVB - as that would also only trigger a heavy adaptation-phase afterwhich UVB wouldn't be that efficient in causing a physiological plantreaction...


the spectrum you posted is very interesting in that it resembles natural light to some extend:

this is a measurement of direct sunlight which passed through a light forrest canopy:
View attachment 4640038
^^ so this is the spectrum that bushes get in their middle, or the plants at the bottom of the forrest, but not cannabis

here's the direct sunlight graphs, from a region with high UV output (snow reflection) - one can see the affinity (sunlight) from specific "dents" (basically every color has its own distinct dent...):
View attachment 4640039
^^ it's why the sun is ~5500k in colour and plants can deal naturally with a great amount of high-energetic rays...

I think that particular diode seems to emanate light which is like a good combination of both these spectra... However, I cannot use them, as they contain blue which means leaves will adjust themselves towards that light... I need 8-16 550nm for sidelight/ intra-canopy light addition... but the monos aren't efficient and given the fact that 550nm transpierces alot through leaves, one could must up quite some strength to see results/"photonic input".

I want to combine them with 8-16 630nm, 660nm & 730nm.... so the sidelight wavelengths would be differentially captured by either the first, second, 1-5th leave (grossly estimated), or equally spread throughout the growroom. Thereby decreasing lightstress on individual leaves and penetrating actually much deeper.... NOT with raw blunt force! shuning trauma, instead going the gentle spectrum-intelligent way! :D

Did you take a look at the other companies diodes? They claim to have these broadband-monochromatic diodes that, e.g. engulf the whole red and even some far-red and thereby help avoid these monochromatic gaps. I wonder if such a broadband diode exists for green & yellow?


welll all I can tell you here is that there are many so-called chlorophyll subtypes - which have slightely altered absorption peak, and these are actually labelled accordingly, e.g. Chl A672. They have a slightely different molecular structure but the central complex remains the same. This is one way how plants can respond to the offered light spectrum & optimize the absorption. So this can help to explain why alot of the quantitised data from studies do have some natural flux to it - esp. in general with plants or living things.


I would like to get to the bottom of what actually causes this Emerson-effect? Like the plant internal mechanism that is reponsible for the increase in raw photosynthesis? My understanding of how the electrons are shuffled around in the two photosystems may hint towards a better synchronization of PS II with I and a higher PS rate because of faster electron-transport or lesser waste as heat. However, this is actually something which also happens in the antenna-complexes, and that seems to be such a complex structure, that it seems next to impossible to do "some math" on it to get it right...

I've had voices yelling at me claiming the conventional Samsumg white CRI diodes do already trigger this E.-effect at maximum and any addition with supplemenal FR may actually further decrease the efficiency, meaning the optimized balance between PS II & I gets disrupted. HOWEVER, if spectrum is responsible for this harmonization, then this may change significantly after passing the first leaf. We cannot "timefreeze" the spectrum...

So the premier goal is to actually offer whatever photons we can to increase leaf-photosynthesis, and this should hold true for all leaves the plants did grow - and not just some topleaves , because the lamp emanates a light that is greatly absorbed int he first 30% of a single leaf:

View attachment 4640054
(Sylvania Linear)

^^ leaf bleach at close range ??? Compared to other technologies in creating light, this spectrum looks like less-rich than the others...

if a leaf doesn't get enough light-saturation for an extended period of time - a plant may withdraw it. So to simply help deliver more photons onto these leaves may prevent that and also help diminish or minimize some of the photomorphogenetic responses from leaves which are usually exposed to such a spectrum.
So I wonder what would happen if we took 5 healthy-green cannabis leaves and placed them each 5cm apart in a row and blasted a lamp at them and measured what kind of spectrum remained after each consecutive crossing of a leaf? With the goal to increase the total net light-saturation of all 5 leaves.

But I do believe that a plant that is exposed to increased amounts of far-red photons is always going to stretch considerably, have long internodes... and while that may not seemed wanted by indoor growers, the exposition to this type of light always seemed to increase dry-harvest weight. I have tried S-HPS with an increased blue output but it didn't change the stretch at all...
Measuring spectrum after passing thru leaves have been done a few times around here. Heres one of my favorite posts from Malocan:
I think there was another example but i cant remember who...
 

Prawn Connery

Well-Known Member
LEDs don't give off much infra-red at all – most of their heat is in the form of convective heat. IR interacts with water molecules (makes them vibrate) in such a way that it transfers its energy much more efficiently than visible electromagnetic waves, which heats them up faster. That's why IR feels hotter than other light. So the IR you are referring to from a HPS lamp is this type, especially at 800+nm. LEDs have very little beyond 700nm, though High Lights have a little more than other typical LEDs.

So to answer your question – which I'm sure GLA won't mind – I would say there would be only a small amount of difference between a High Light board and a typical Samsung CRI80 3000K board, or even an R-spec type board with added 660nm.

Having said that, as you know those plant photos above are mine and IMO the extra near-UV in that spectrum has certainly performed well in winter here. I commented in another thread where @mauricem00 mentioned UVA helps transport Ca and I believed he might have been on to something, as VPD was very low during that grow so one explanation for the fast, healthy growth could have been the extra UVA and near-UV in the spectrum.

Some growers do add HPS or CMH to their LED grows in winter to provide extra warmth. I don't, but winters are mild here compared to other places. It still gets down to 5C or so here.
 
Last edited:

Prawn Connery

Well-Known Member
plants have an extreme stomatal opening response when exposed to UVB:
View attachment 4640035
the response peaks at 280nm... I think this is perhaps due to a survival-response when exposed to a potentially harmfull heavy-energy radiation - to opens stomatas to maximum and thereby trade loss-of-water with increased cooling as a means of self-protection.
Nevertheless, it seems like blue light can greatly do this job, too... so there is little need to expose plants to a full daytimes phase to UVB - as that would also only trigger a heavy adaptation-phase afterwhich UVB wouldn't be that efficient in causing a physiological plantreaction...


the spectrum you posted is very interesting in that it resembles natural light to some extend:

this is a measurement of direct sunlight which passed through a light forrest canopy:
View attachment 4640038
^^ so this is the spectrum that bushes get in their middle, or the plants at the bottom of the forrest, but not cannabis

here's the direct sunlight graphs, from a region with high UV output (snow reflection) - one can see the affinity (sunlight) from specific "dents" (basically every color has its own distinct dent...):
View attachment 4640039
^^ it's why the sun is ~5500k in colour and plants can deal naturally with a great amount of high-energetic rays...

I think that particular diode seems to emanate light which is like a good combination of both these spectra... However, I cannot use them, as they contain blue which means leaves will adjust themselves towards that light... I need 8-16 550nm for sidelight/ intra-canopy light addition... but the monos aren't efficient and given the fact that 550nm transpierces alot through leaves, one could must up quite some strength to see results/"photonic input".

I want to combine them with 8-16 630nm, 660nm & 730nm.... so the sidelight wavelengths would be differentially captured by either the first, second, 1-5th leave (grossly estimated), or equally spread throughout the growroom. Thereby decreasing lightstress on individual leaves and penetrating actually much deeper.... NOT with raw blunt force! shuning trauma, instead going the gentle spectrum-intelligent way! :D

Did you take a look at the other companies diodes? They claim to have these broadband-monochromatic diodes that, e.g. engulf the whole red and even some far-red and thereby help avoid these monochromatic gaps. I wonder if such a broadband diode exists for green & yellow?


welll all I can tell you here is that there are many so-called chlorophyll subtypes - which have slightely altered absorption peak, and these are actually labelled accordingly, e.g. Chl A672. They have a slightely different molecular structure but the central complex remains the same. This is one way how plants can respond to the offered light spectrum & optimize the absorption. So this can help to explain why alot of the quantitised data from studies do have some natural flux to it - esp. in general with plants or living things.


I would like to get to the bottom of what actually causes this Emerson-effect? Like the plant internal mechanism that is reponsible for the increase in raw photosynthesis? My understanding of how the electrons are shuffled around in the two photosystems may hint towards a better synchronization of PS II with I and a higher PS rate because of faster electron-transport or lesser waste as heat. However, this is actually something which also happens in the antenna-complexes, and that seems to be such a complex structure, that it seems next to impossible to do "some math" on it to get it right...

I've had voices yelling at me claiming the conventional Samsumg white CRI diodes do already trigger this E.-effect at maximum and any addition with supplemenal FR may actually further decrease the efficiency, meaning the optimized balance between PS II & I gets disrupted. HOWEVER, if spectrum is responsible for this harmonization, then this may change significantly after passing the first leaf. We cannot "timefreeze" the spectrum...

So the premier goal is to actually offer whatever photons we can to increase leaf-photosynthesis, and this should hold true for all leaves the plants did grow - and not just some topleaves , because the lamp emanates a light that is greatly absorbed int he first 30% of a single leaf:

View attachment 4640054
(Sylvania Linear)

^^ leaf bleach at close range ??? Compared to other technologies in creating light, this spectrum looks like less-rich than the others...

if a leaf doesn't get enough light-saturation for an extended period of time - a plant may withdraw it. So to simply help deliver more photons onto these leaves may prevent that and also help diminish or minimize some of the photomorphogenetic responses from leaves which are usually exposed to such a spectrum.
So I wonder what would happen if we took 5 healthy-green cannabis leaves and placed them each 5cm apart in a row and blasted a lamp at them and measured what kind of spectrum remained after each consecutive crossing of a leaf? With the goal to increase the total net light-saturation of all 5 leaves.

But I do believe that a plant that is exposed to increased amounts of far-red photons is always going to stretch considerably, have long internodes... and while that may not seemed wanted by indoor growers, the exposition to this type of light always seemed to increase dry-harvest weight. I have tried S-HPS with an increased blue output but it didn't change the stretch at all...
Nice post!

I reckon a lot of cannabis varieties benefit from a moderate amount of stretch as it not only increases the overall surface area exposed to light, but the photomorphogenic response increases leaf size that can absorb more photons. While UV and blue are known to inhibit stretch (I guess it depends on the blue wavelength) I believe it's the red to far red ratio that affects it most.
 

Kassiopeija

Well-Known Member
Measuring spectrum after passing thru leaves have been done a few times around here. Heres one of my favorite posts from Malocan:
I think there was another example but i cant remember who...
nice thanks for the link Rocket Soul

so green/yellow & FR have been reduced in irradiance to grossly approxed 40% by crossing the first or 2nd leaf
the reduction of blue & red was to 0.5%-1%right at the very first leaf - which is a significant difference between these wavelengths.

however, he seems to have not ruled out refractionated straylight that comes in from the side of the leaves - as the loss with each consecutive leaf seems to decrease by much - going from only 50% to almost no loss in the case of red, blue & green, whereas FR actually gains (!?!) some strength from crossing the 2nd leaf (00.1 --> 0.14) and then stays there (0.14 --> 0.14)

edit:
however, these leaves are from palms or ferns it seems, these are usually more thicker and I wonder how much of the red/blue is still retained after piercing 20-30cm into a dense cannabis canopy?
 

Rocket Soul

Well-Known Member
nice thanks for the link Rocket Soul

so green/yellow & FR have been reduced in irradiance to grossly approxed 40% by crossing the first or 2nd leaf
the reduction of blue & red was to 0.5%-1%right at the very first leaf - which is a significant difference between these wavelengths.

however, he seems to have not ruled out refractionated straylight that comes in from the side of the leaves - as the loss with each consecutive leaf seems to decrease by much - going from only 50% to almost no loss in the case of red, blue & green, whereas FR actually gains (!?!) some strength from crossing the 2nd leaf (00.1 --> 0.14) and then stays there (0.14 --> 0.14)

edit:
however, these leaves are from palms or ferns it seems, these are usually more thicker and I wonder how much of the red/blue is still retained after piercing 20-30cm into a dense cannabis canopy?
My take away from the test is that the plant like to absorb 680nm and blue, and wont absorb far red really well
 

ANC

Well-Known Member
I see all these light with each manufacturers making claims as to what the extra colours are supposed to do,. What I never see is side by side grows showing a difference. In my experience adding whatever amount you were going to spend in funky colours, in simple 3000K LEDs rather would yield more and cover more floor.
 
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