grampanew2this
Member
I have a vipar spectre with red, blue and white individually controllable lighting.....The plant loves all of them on at full...but should I turn on only my red when its budding time?
Red light best for budding?
- Thread starter grampanew2this
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grampanew2this
Member
cool, thanks
Perhaps, due to the "blue photon penalty".
There's a measurable and significant decrease in crop yield when the percentage of blue photons hitting a grow exceeds 4% in flower. At 20%, the penalty is ≈ 15% loss (going from memory)
[time passes]
The title of the paper that describes is "Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids" and, when you search in Google, the summary reads "Yield increased by 0.77% per 1% decrease in blue photons". The paper is by Dr. Bruce Bugbee and some of his students. Bugbee is a leading, arguably "the leading", expert in cannabis grow lighting and is also well renowned for his decades of experience in plant nutrition.
This research was not a breakthrough discovery.; its value is that it quantified the impact. We've known that plants grow compact and bushy when their light has a lot of blue photons while plants getting light with a lot of red photons will grow taller. That's one reason why cannabis growers used different lights over the course of a grow.
What model Vipar are you using?
There's a measurable and significant decrease in crop yield when the percentage of blue photons hitting a grow exceeds 4% in flower. At 20%, the penalty is ≈ 15% loss (going from memory)
[time passes]
The title of the paper that describes is "Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids" and, when you search in Google, the summary reads "Yield increased by 0.77% per 1% decrease in blue photons". The paper is by Dr. Bruce Bugbee and some of his students. Bugbee is a leading, arguably "the leading", expert in cannabis grow lighting and is also well renowned for his decades of experience in plant nutrition.
This research was not a breakthrough discovery.; its value is that it quantified the impact. We've known that plants grow compact and bushy when their light has a lot of blue photons while plants getting light with a lot of red photons will grow taller. That's one reason why cannabis growers used different lights over the course of a grow.
What model Vipar are you using?
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Fangthane
Well-Known Member
Possibly just bro-science that I never bothered to fully explore, but I was under the impression blue lighting in flower supposedly increased cannabinoids. Not sure how the total power in their light is divided up between white, red and blue, but presumably there would also be measurable yield penalty from losing a percentage of available wattage by switching off the blue.
Grow light vendors have been pushing UV-B for about 18 months now. The justification, that I've read, is that a research that said that the enhancement effect was equivocal because, in one test, CBD was increased while it was not increased in another. The grow light industry saw that one trial had an increase. Bugbee argues that "equivocal" means…equivocal.
[time passes]
Perhaps it was here - "How Ultraviolet Radiation Affects Plants with Dr. Bruce Bugbee". It's the "Lydon" study.
Bingo.
"UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES"
From the transcript of the YouTube video "Best Grow Lighting for Cannabis with Dr Bruce Bugbee"
21:16 um and we they do help keep plants short
21:21 but soda blue photons and blue photons we can buy blue photons much cheaper so
21:28 we haven't found a a particularly large effect of UV for reducing plant height
21:36 and now there's enormous speculation in the community on the
21:44 potential for UV photons to make more cannabinoids and
21:51 that fundamentally comes from the fact that cannabinoids absorb UV light
21:57 so if you have UV the plant would synthesize more to block these these
22:03 damaging photons and if we could show that helps that would be a very big deal
22:08 indeed we we would immediately buy UV photons we have never been able to show
22:15 they help increase cannabinoids multiple tests at different doses
22:21 so doesn't mean they can't possibly work we just haven't been able to show it in
22:27 spite of multiple tests and then our work has been recently
22:33 confirmed by a group at Guelph in Canada they weren't able to show they increased
22:39 cannabinoids either so it's hard to get proof things nothing can't happen it's
22:47 just that all we can say is in the lab we've not been able to show a beneficial
22:52 effect on increased cannabinoid synthesis so on the other end of the spectrum then we go beyond
22:59 um the par range at 700 nanometers of deep red and we start to go into far red
23:06 and and as distinct from infrared which is often confused so far red is still
23:13 dimly visible in the sort of 700 to 750 range and there are effective LEDs…
"Guelph" is Guelph University on Ontario. They've got a solid reputation in the sciences and have done a lot of cannabis research.
The yield penalty is well documented whereas an increase in cannabinoids appears to be unconfirmed so, to my way of thinking, I'd recommend dropping the blue, if possible.
rkymtnman
Well-Known Member
does he ever mention the actual wavelengths in the "blue light"?
The range is 401-500nm is mentioned in the text but 400-500nm is in one of the graphics so I'll go with 400-500 (it's easier to type, too).
It was good to re-read the paper.
From the Abstract:
"LED technology facilitates a range of spectral quality, which can be used to optimize photosynthesis, plant shape and secondary metabolism. We conducted three studies to investigate the effect of blue photon fraction on yield and quality of medical hemp. Conditions were varied among studies to evaluate potential interactions with environment, but all environmental conditions other than the blue photon fraction were maintained constant among the five-chambers in each study. The photosynthetic photon flux density (PPFD, 400 to 700 nm) was rigorously maintained at the set point among treatments in each study by raising the fixtures. The lowest fraction of blue photons was 4% from HPS, and increased to 9.8, 10.4, 16, and 20% from LEDs. There was a consistent, linear, 12% decrease in yield in each study as the fraction of blue photons increased from 4 to 20%. Dry flower yield ranged from 500 to 750 g m-2. This resulted in a photon conversion efficacy of 0.22 to 0.36 grams dry flower mass yield per mole of photons. Yield was higher at a PPFD of 900 than at 750 μmol m-2 s-1. There was no effect of spectral quality on CBD or THC concentration. CBD and THC were 8% and 0.3% at harvest in trials one and two, and 12% and 0.5% in trial three. The CBD/THC ratio was about 25 to 1 in all treatments and studies. The efficacy of the fixtures ranged from 1.7 (HPS) to 2.5 μmol per joule (white+red LED). Yield under the white+red LED fixture (10.4% blue) was 4.6% lower than the HPS on a per unit area basis, but was 27% higher on a per dollar of electricity basis. These findings suggest that fixture efficacy and initial cost of the fixture are more important for return on investment than spectral distribution at high photon flux."
and "Results":
"As percent blue increased from 4 to 20%, flower yield decreased by 12.3%."
"Blue photon fraction had no effect on final cannabinoid concentration"
and I didn't know/had forgotten:
"Increasing the fraction of blue photons is typically associated with decreased leaf expansion and thus reduced photon capture"
rkymtnman
Well-Known Member
is this a trial on hemp???
thc at less than 1%?
check out a chlorophyll absorption chart for cannabis and you'll see a huge blue spike.
i'm not a Doctor like Bugbee but i'm calling BS on no blue in bloom
Yes. That's no secret. He's in the US and federally funded. It's cannabis cannabis that's been bred to have a low THC yield and it's used in research in the US because cannabis cannabis is a Schedule I drug.
I don't know which figure you're referring to. I've seen lots of graphics that show what McCree discovered 50+ years ago. They're variations on a theme because plants haven't fundamentally changed in the last 5 decades and, yes, blue photons result in a lot of photosynthesis.
I'm not arguing "no blue". If there's 0% blue, you'll get deformed growth (can't cite that - it's in a paper on my computer and I'm not interested in digging it up).
On the other hand, I've presented evidence that shows that there's a significant loss in yield when the % of blue photons exceeds 4% in flower. And I've only delved into a couple of sources. A reader who takes the time to use that Google-thing will find dozens of research papers on the topic.
If you have data that differs from what Bugbee and others have documented, publish it here and/or send it to Bugbee and see what he says.
For what it's worth, you will get better results with a modern white light.
30-40 watts/square foot is common. Go by actual watts, ignore all the misleading "equivalent" BS.
An example from the same company.
ViparSpectra KS3000 320W LED Grow Light
Discover ViparSpectra online store. Buy high quality LED grow lights, grow tents and grow tools. Free shipping. Fast delivery. Best customer service.
www.viparspectra.com
rkymtnman
Well-Known Member
this graph here would tell me that there is a massive blue and orange-ish spike for chlorphyll absoption. wouldn't you agree??
rkymtnman
Well-Known Member
i'm guessing this was your source?
Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids
LED technology facilitates a range of spectral quality, which can be used to optimize photosynthesis, plant shape and secondary metabolism. We conducted three studies to investigate the effect of blue photon fraction on yield and quality of medical hemp. Conditions were varied among studies to...
i've been reading bits and pieces so far.
Completely. Just like McCree discovered.
It's good info to have but has no bearing on the observed, documented, published, and reproduced results that I've discussed.
A book on training for long distance running observes that there's no medal given out for having the highest VO2max. What counts is who crosses the finish line first. Similar issue here - the fact that P (photosynthesis) increases under certain conditions is not the issue. To me, it's about increasing crop quality and yield.
Having said that, I think understand where you're coming from because I was under a similar misunderstanding for a while. Here's the skinny…
When I started growing, I dug into "the research" to learn what I could about grow lighting. The Bugbee videos were, and are, a good source of info but I started to look for the research behind what Bugbee was talking about. it took some time to start finding and digesting what I found.
[had to turn on dictation]
The Chandra paper discusses the research done at the University of Mississippi regarding temperature, light levels, and CO2 concentrations for cannabis. It is considered the seminal paper in that field.
The different curves in the graphic below are the net photosynthesis rate at different temperature levels. Note that the temperatures are in the legend and they are in degrees Celsius.
Once you go above 500 nmol, the Pn curve starts to roll off and it really flattens at 1000µmols. It's not that the curve turns negative, rather, it's that the rate of increase starts to decrease. That's the law diminishing returns in action.
The Chandra paper is a very informative piece of research and the graphic leaves a very strong impression. But it's also a bit of a deterrent because, things really change at PPFD's about 500 µmol. At almost any temperature, doubling the PPFD's does not result in much of an increase in Pn. So what gives?
The big issue is I'm not harvesting net photosynthesis. I want to increase the quality and yield of my cannabis crop. Dr. Bugbee talks about cannabis using more and more light and, as he says in one, YouTube video, "we ve never found a maximum". So what's the big deal with adding more light if photosynthesis essentially rolls off so much after about 1000 micromols?
It took me a couple of months to find a paper that discusse what happens when you turn up the lights.
This issue is discussed in "Frontiers in Plant Science - Yield, Potency, and Photosynthesis in Increasing Light Levels". This paper is well worth the read.
This text is quoted from the last few pages of the paper:
"DISCUSSION
Cannabis Inflorescence Yield Is
Proportional to Light Intensity
Cannabis yield increased linearly from 116 to 519 g·m−2 (i.e., 4.5 times higher) as APPFD increased from 120 to 1,800 μmol·m−2 ·s−1 (Figure 7A). Note that yields in the present study are true oven-DWs. Since cannabis inflorescences are typically dried to 10–15% moisture content to achieve optimum marketable quality (Leggett, 2006), dividing DW by the proportion of marketable biomass that the DW comprises (e.g., for 15% moisture, divide DW by 0.85) will estimate marketable yield. The harvest index increased linearly from 0.560 to 0.733 and (i.e., 1.3 times higher) as APPFD increased from 120 to 1,800 μmol·m−2 ·s−1 (Figure 7B). The apical inflorescence density increased linearly from 0.0893 to 0.115 g·cm−3 (i.e., 1.3 times higher) as APPFD increased from 120 to 1,800 μmol·m−2·s−1 (Figure 7C).
Cannabidiolic acid (CBDA) was the dominant cannabinoid in the dried inflorescences; however, there were no APPFD treatment effects on the potency of any of the measured cannabinoids (Table 1). Due to linear increases in inflorescence
yield with increasing LI, cannabinoid yield (g·m−2) increased by 4.5 times as APPFD increased from 120 to 1,800 μmol·m−2·s−1
Myrcene, limonene, and caryophyllene were the dominant
terpenes in the harvested inflorescences (Table 2). The potency of total terpenes, myrcene, and limonene increased linearly from 8.85 to 12.7, 2.51 to 4.90, and 1.05 to 1.60 mg·g−1 inflorescence DW (i.e., 1.4, 2.0, and 1.5 times higher), respectively, as APPFD increased from 120 to 1,800 μmol·m−2 ·s−1 . There were no APPFD effects on the potency of the other individual terpenes.
[snip]
Effectively, within the range of practical indoor PPFD levels— the more light that is provided, the proportionally higher the increase in yield will be. Therefore, the question of the optimum LI may be reduced to more practical functions of economics and infrastructure limitations: basically, how much lighting capacity can a grower afford to install and run?"
That's great info to have and, going back to the misconception that I had - per Chandra, Pn starts to roll at 500µmols and even more at 1kµmols. But, as stated in the discussion "However, the yield results of this trial demonstrated cannabis’ immense plasticity for exploiting the incident lighting environment by efficiently increasing marketable biomass up to extremely high—for indoor production—LIs (Figure 7A)."
That threw me for a loop - the fact that the Pn was flattening did not mean that the yield and quality curves were flattening.
In the same way that Drew the wrong conclusion, it sounds like you see photosynthesis dramatically increasing under blue light and you conclude it would be better to have blue in flower. But that's not the case if you want to increase crop quality or yield.
The research shows that those attributes decrease as % blue >4%. And that's what we've seen in the real world. Legacy growers used blue heavy lights in seedling and veg and then switched to red heavy in flower. With the advent of the white LED, there's a strong cost argument to use white LED's but two companies, that I'm aware of, make separate veg and flower lights (HLG and Chilled). Further, companies are starting to market tunable lights and, for at least a couple of reasons, that is one thing that we'll see more and more of. Sure, those could be considered marketing gimmicks but there's that pesky research that says differently.
If the increase P doesn't result in more of the good stuff, what is it doing? It's used in veg because it builds lots of stems and leaves and it results in a plant morphology that is referred to as "short and bushy". Low plants make it easier to grow in racks and plants grown under blue heavy light will tend to have a more even canopy so it's easier to light the plant evenly.
Yet another Bugbee video screenshot (the photo is of Paul Kasuma who was a Bugbee understudy-check out his research).
In short, I think I understand where you're coming from. I read the Chandra paper and didn't see the value of high PPFD >1k but, as usual, there's more to the issue than meets the eye.
Yup.i'm guessing this was your source?
Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids
LED technology facilitates a range of spectral quality, which can be used to optimize photosynthesis, plant shape and secondary metabolism. We conducted three studies to investigate the effect of blue photon fraction on yield and quality of medical hemp. Conditions were varied among studies to...journals.plos.org
i've been reading bits and pieces so far.
rkymtnman
Well-Known Member
to be honest, most of that info is very interesting, but for a small grower, i'm not so much interested in less yield but better quality.
and i've read/learned/seen that high blue values lead to better quality. everything from a MH vs HPS grow light from start to finish, but 315LEC with alot of blues, from 10000K finishing bulbs, to growers switching their leds to all blue for the last 2 weeks (heliospectra).
and i guess my main question is how does a small grower analyse my light to see if my light is close to 4% blue?
don't think i'm trying to prove i'm right, more so just questioning my long held beliefs that blue is very important for veg and bloom
cobshopgrow
Well-Known Member
@Delps8 i am very thankfull for Chandras and Bugbees work and would agree that its the best info out there.
but let me throw this article in to this discussion.
on a quick read i would say they support the high PPFD/yield theorie.
“We maxed out our load,” Sanders says. “We learned that the best value was around that 1,800 micromole level for cannabis. As we start increasing from 1,000 micromoles up to 1,800, we saw about a 1% increase in yield for every 1% increase in light intensity. That started to diminish from 1,800 to 2,500.” While yield increased up to 2,500 PPFD, it was more bell curve than linear beyond 1,800 PPFD. "
but the red blue thing is a bit contradicting (quite a U turn, TOCC to bugbee).
"TOCC’s next study is focused on effects of different light spectra at various PPFDs. The best yields to date have been with Fluence’s broad-spectrum R4 lighting. Type 1 (high-THC, low-CBD) cannabis grown at 1,500 PPFD under R4 showed 17% higher yields in dry bud weight as compared to R6. Higher fractions of red light (corresponding with higher R numbers) tracked lower yields for the company. "
one thing to consider is the bleaching.
"“Photobleaching seems to be an interaction between light intensity and light quality,” Westmoreland says. “It seems that a higher fraction of red makes plants more prone to photobleaching. It also tends to happen just at the high light intensity, regardless of the fraction of red.” He suggests photobleached tips are most likely above 60% to 70% red. "
just so we can continue to turn our circles, not saying anyone is right or wrong.
@Moflow , stuff for you.
but let me throw this article in to this discussion.
on a quick read i would say they support the high PPFD/yield theorie.
“We maxed out our load,” Sanders says. “We learned that the best value was around that 1,800 micromole level for cannabis. As we start increasing from 1,000 micromoles up to 1,800, we saw about a 1% increase in yield for every 1% increase in light intensity. That started to diminish from 1,800 to 2,500.” While yield increased up to 2,500 PPFD, it was more bell curve than linear beyond 1,800 PPFD. "
but the red blue thing is a bit contradicting (quite a U turn, TOCC to bugbee).
"TOCC’s next study is focused on effects of different light spectra at various PPFDs. The best yields to date have been with Fluence’s broad-spectrum R4 lighting. Type 1 (high-THC, low-CBD) cannabis grown at 1,500 PPFD under R4 showed 17% higher yields in dry bud weight as compared to R6. Higher fractions of red light (corresponding with higher R numbers) tracked lower yields for the company. "
one thing to consider is the bleaching.
"“Photobleaching seems to be an interaction between light intensity and light quality,” Westmoreland says. “It seems that a higher fraction of red makes plants more prone to photobleaching. It also tends to happen just at the high light intensity, regardless of the fraction of red.” He suggests photobleached tips are most likely above 60% to 70% red. "
just so we can continue to turn our circles, not saying anyone is right or wrong.
@Moflow , stuff for you.
Prawn Connery
Well-Known Member
Bruce Bugbee has never grown a high THC cannabis plant – Utah University only grows CBD strains. He also sells Apogee light meters, so never forget what his TRUE agenda is. To sell more light meters! He also contradicts himself a lot . . . but I digress.
There are some missing pieces of info in some of the above posts, namely that those high PPFD levels are being acheived with supplementary CO2. If you try growing at 1500-2000 PPFD in average atmospheric conditions (400PPM CO2) instead of 1000-1200PPM CO2 your plants are going to suffer.
A lot of people think that more CO2 facilitates more efficient photosynthsis – and it does – but the real benefit is that CO2 quenches chloroplasts (prevents them from overheating) so that they can absorb more photons. And that's why you can hit your plants with higher PPFD levels.
PPFD is not only CO2 dependent, it is strain dependent. Sativas can handle higher levels of light than indicas. They have skinnier leaves – less surface area – and a more open structure that allows light to penetrate instead of capturing most of the photons in the upper canopy, where it is concentrated. Large-scale defoliation makes things worse, because it increases light concentrations in any given area as there are fewer fan leaves to absorb the photons and protect the stems – which turn red from stress pigments (anthocyanins) produced in response to the added light stress.
Researchers only think too much red light causes bleaching – they haven't proven it yet – but if it does, it could be as simple as the RGB ratio oversaturating the pgiments in chloroplasts with too much red light. In other words, chloroplasts are made of pigments that absorb different colors, but once those pigments start to saturate, excess photons are converted to heat instead of being photosynthesised and so leaf temperatures start to increase.
Most grow lights have 20% or less blue, but many have 50-60% or more red light, so it is feasible that this heavy red weighting is providing more red photons than can be photosynthesised compared to blue. If the light had a higher blue weighting, then we can assume that excess blue photons are going to bleach a plant faster than excess red photons, becaue blue photons carry about 50% more energy than red photons – which means each blue photon has 50% more latency.
The difference in "quality" between high red and high blue or UV lights on cannabis can be attributed to several schools of thought:
Cell contraction (UV, blue) negatively affects yield. If a plant produces the same amount of THC but less yield, the THC percentage gos up.
Cell expansion (far red, or rather increased far red:red ratio) positively affects yield, which has the potential to decrease THC levels if the plant does not produce more cannabinoids along with the extra yield.
But what if we combined the two? High levels of red – and especially far red – with moderate levels of blue and UVA? Do we see an increase in both yield and potency? Would a comparison between natural sunlight – which contains UV and high levels of far red – and indoor LED light – which usualy lacks these spectra – be a good comparison?
The fact is, outdoor cannabis – if grown in optimal conditions – will be more potent than indoor cannabis: https://ecs-botanics.com/weed-grow-outdoor-vs-indoor/#:~:text=They've executed this experiment,, higher in THCv, etc.
Why? UV. And it doesn't have to be UVB, either – sunlight only has a very small percentage of UVB, as most of the UV is at the UVA end of the spectrum.
We've done our own tests that show the addition of UVA compared to no UVA increases THC levels without impacting yield. However, the addition of extra blue photons does affect yield, as we have seen when comparing a ~3000K light to a ~3500K light.
But is it because of the cell contraction properties of blue light that yields suffer or is it something few people have thought to discuss? Namely, if you keep a plant compact, light can't penetrate to areas that are shaded compared to plants with more open structures that are going to grow bigger because they get more light to more areas of the plant?
Could it be as simple as that?
There are some missing pieces of info in some of the above posts, namely that those high PPFD levels are being acheived with supplementary CO2. If you try growing at 1500-2000 PPFD in average atmospheric conditions (400PPM CO2) instead of 1000-1200PPM CO2 your plants are going to suffer.
A lot of people think that more CO2 facilitates more efficient photosynthsis – and it does – but the real benefit is that CO2 quenches chloroplasts (prevents them from overheating) so that they can absorb more photons. And that's why you can hit your plants with higher PPFD levels.
PPFD is not only CO2 dependent, it is strain dependent. Sativas can handle higher levels of light than indicas. They have skinnier leaves – less surface area – and a more open structure that allows light to penetrate instead of capturing most of the photons in the upper canopy, where it is concentrated. Large-scale defoliation makes things worse, because it increases light concentrations in any given area as there are fewer fan leaves to absorb the photons and protect the stems – which turn red from stress pigments (anthocyanins) produced in response to the added light stress.
Researchers only think too much red light causes bleaching – they haven't proven it yet – but if it does, it could be as simple as the RGB ratio oversaturating the pgiments in chloroplasts with too much red light. In other words, chloroplasts are made of pigments that absorb different colors, but once those pigments start to saturate, excess photons are converted to heat instead of being photosynthesised and so leaf temperatures start to increase.
Most grow lights have 20% or less blue, but many have 50-60% or more red light, so it is feasible that this heavy red weighting is providing more red photons than can be photosynthesised compared to blue. If the light had a higher blue weighting, then we can assume that excess blue photons are going to bleach a plant faster than excess red photons, becaue blue photons carry about 50% more energy than red photons – which means each blue photon has 50% more latency.
The difference in "quality" between high red and high blue or UV lights on cannabis can be attributed to several schools of thought:
Cell contraction (UV, blue) negatively affects yield. If a plant produces the same amount of THC but less yield, the THC percentage gos up.
Cell expansion (far red, or rather increased far red:red ratio) positively affects yield, which has the potential to decrease THC levels if the plant does not produce more cannabinoids along with the extra yield.
But what if we combined the two? High levels of red – and especially far red – with moderate levels of blue and UVA? Do we see an increase in both yield and potency? Would a comparison between natural sunlight – which contains UV and high levels of far red – and indoor LED light – which usualy lacks these spectra – be a good comparison?
The fact is, outdoor cannabis – if grown in optimal conditions – will be more potent than indoor cannabis: https://ecs-botanics.com/weed-grow-outdoor-vs-indoor/#:~:text=They've executed this experiment,, higher in THCv, etc.
Why? UV. And it doesn't have to be UVB, either – sunlight only has a very small percentage of UVB, as most of the UV is at the UVA end of the spectrum.
We've done our own tests that show the addition of UVA compared to no UVA increases THC levels without impacting yield. However, the addition of extra blue photons does affect yield, as we have seen when comparing a ~3000K light to a ~3500K light.
But is it because of the cell contraction properties of blue light that yields suffer or is it something few people have thought to discuss? Namely, if you keep a plant compact, light can't penetrate to areas that are shaded compared to plants with more open structures that are going to grow bigger because they get more light to more areas of the plant?
Could it be as simple as that?
Prawn Connery
Well-Known Member
In response to the OP's question, it all depends on how big your light is compared to your grow area.
If the fixture is big enough, then red and white light (which also contains blue) should be optimal. But if you don't have enough light to begin with, then turn everything up, as the extra blue photons will likely increase your yields by way of providing more total light.
There's an old saying that photons > spectra, but once you have the opitmal amount of light then spectra > photons. It's all about the balance.
Prawn Connery
Well-Known Member
From what I have read, it was strain dependent. Interestingly, this research appears to correspond with exactly what I was saying about concentrations of red light in chloroplasts.
David Hawley, PhD on LinkedIn: ICL Spectrum Results
A little Fluence research update here. We've been exploring for a while now if inter-canopy lighting (ICL) makes sense for cannabis production, and we've got…
The taller plants where not as affected as the shorter strain. So that tells me the shorter strain was oversaturated with red as it would have absorbed more light at the top of the canopy with less light penetration to other parts of the plant – and other chloroplasts – that woud have shared the load.
The taller plants that received a more even distribution of light were less affected by the increase in blue light as we can assume the red light was not concentrated in one or fewer areas.
The same rings true if we assume the taller plants were more sativa: ie; less surface area to absorb photons, and hence less oversaturation of photons in the choloplasts.
That link also has some interesting info on UV. Other lighting companies are starting to understnd what we've observed for years – far red and UVA and the keys to quality and yield.