Led advise needed. How many umol at canopy and photobleaching causes

Everything Ralph is saying right now about reds. Is the entire reason the Emerson effect is so important, and just another reason while people need to be playing with the out of spectrum reds MORE. Kinda crazy just a few nm in color makes a big difference…

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The facility I ran did ~400 for the cloner, 5-650 in veg, 1200 ppfd with Gavita DE’s in flower. They were 4’ on center, turned down to 1000 watts and kept 3’ off of the canopy. Running at 1150 they would get hot spots and bleaching at 4’ canopy clearance.

@vortal is right on about the metabolism and ppfd. It’s only with serious crop steering and constant attention that we were able to push it without automation.

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You’re welcome.

UV-A:
Adding UV-A can be beneficial regarding the cryptochrome action spectra, e.g., cryptochrome’s effects on plants (increased pigmentation, photosynthesis=s, transpiration, etc.). And to a lesser extent, the phototropin action spectra, e.g., increased stomatal conducnce, stalky plants, etc. However, the cryptochrome action spectrum extends into and is strongly affected by blue range photons. So UV-A isn’t critical, which is why few LED mfgs include UV-A. Plus, UV-A LEDs are costly and have a reduced life span. Overall, adding UV-A isn’t worth the hassle. And if you do add it, you only need 10-40 μmol/s/m2.

In one study, during the last two weeks of flowering Larry OG, adding narrow waveband UV-A (~390 nm) at ~66 μmol/s/m2 to ~511 PPFD was found to increase THC by 3.6%. But the UV-A also significantly reduced most terpenes and reduced biomass yield (probably due to growth reduction). In the same study, a similar increase in THC was also found by adding narrow waveband blue (~450 nm) and red (~660 nm) at ~158 μmol/s/m2 to ~511 PPFD white light. Therefore, the THC increase probably wasn’t due to UV-A photochemical response but instead due to increased photosynthetic μmol/s/m2 because 390 nm UV-A is photosynthetic. If the study used a higher PPFD of ~800-1000 without UV-A, the increase in THC would have been much greater than a merger ~2.5-3.6%. See:

Cannabis sativa L. Response to Narrow Bandwidth UV and the Combination of Blue and Red Light during the Final Stages of Flowering on Leaf Level Gas-Exchange Parameters, Secondary Metabolite Production, and Yield

UV-B:

It is not needed, and current research has found no increase in THC-A and a trivial and inconsequential increase in THC. The tiny increase in THC is likely not a result of increased biosynthesis but rather from UV-B photooxidative decarboxylation of THC-A into THC. There are no reliable and well-designed peer-reviewed studies that find UV-B increases THC. Dr. Bugbee is studying this topic, but he is doubtful. And until such a finding is realized, if it ever is, it’s simply a myth that UV-B increases THC. A legend based on a poorly designed and conducted 50-year-old paper (Lydon et al., 1987) that cannot be considered reliable. Sadly, a myth is hard to kill once cannabis ‘experts’ proclaim UV-B increases THC.

Because UV-B’s lack of effect on THC and UV-B diodes are even more costly and have an even shorter life span, there are zero reasons to add UV-B at this point. If peer-reviewed studies eventually find UV-B increases THC (or other benefits not already provided by blue photons), it would be worth considering UV-B. But don’t hold your breath.

Many other ways to increase THC exist that are easier, cheaper, safer, and proven effective - so UV-B is not only ineffective but also unnecessary.

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Nice, I love to see high PPFD for cloning! :heart_eyes: I run 150-200 PPFD for the first few days in domes, then increase to 300 PPFD once rooted. When using domes it’s hard to run high PPFD because it heats up the dome interior too much.

And FWIW, running DE HPS above the lamp’s rated wattage significantly affects the spectrum. It makes the spectrum redder. Running the wattage below its rated wattage makes the spectrum greener. That’s why growers shouldn’t adjust DE HPS wattage.

At 1150 watts, the Gavita lamp goes from ~48% red (other data) to ~54% red! And plugging 54% red into the equations I created for PPFD, using your listed 1200 PPFD, (1200*54/100) gives you ~648 μmol/s/m2 of red photons. That explains why you see photobleaching because many strains will bleach at >650 μmol/s/m2 of red. And, some canopy spots would have gotten greater than 1200 PPFD. So, those spots would have received >700 μmol/s/m2 of red, which is very likely to cause photobleaching.

For comparison, at 1000 watt, ~48% red, and 1200 PPFD, on average your canopy recieved (1200*48/1000) = 576 μmol/s/m2 of red. So, even at spotes with higher PPFD, the red μmol/s/m2 was likely below 650.

One critical environmental factor most growers underrate and don’t measure is air speed voleicy. At high PPFD, it must be at least 1 m/s at the canopy, but 2 m/s is better. And intracanopy must be >0.3 m/s. Otherwise, the leaves will overheat, and bad things will happen, or at least growth and health will suffer.

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All the information provided is awesome. And without getting into all the math of %'s of red and such, I just look at a max ppfd of 1200 to 1500 with co2. Most people don’t have everything dialed in to that point and waist their money on co2.

I’ve used Fulton Lights that had IR on all the time and UV controlled separately. The yields were big, much larger than lights without either. I’ve also used lights that the IR/UV were controlled together, separate from the rest of the light. I must say, the Fulton with the constant IR had better yields, although the other light worked much better during veg and the yields were still better than without IR/UV. With that said…

I think a light with IR and UV, not only controlled separately from the main light, but also separately from each other, is the way to go. Are they necessary for good yields and great flower, no. But used properly, they can sure help.

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I agree a max PPFD of 1200 is a good target for most growers. At that PPFD, 1000-1200 ppm CO2 is ideal. I also agree ~1500 ppm is the max CO2 anyone should use (specifically, 1600 ppm), but only with very high PPFD, and there’s never a reason to exceed 1600 ppm CO2. People forget elevated CO2 brings adverse effects, including reduced transpiration and uptake of mass flow nutrients caused by reduced stomatal conductance.

But, FWIW, science disagrees with you regarding UV and cannabis. Far-red (701-760 nm) does has significant photobiological effects. Still, we only want a limited amount (<5% to total PPFD), and we don’t want any IR beyond 760 nm. For an in-depth discussion on far-red, check out my comments in this thread:

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You call out some great ways we could have improved when I was there. I’m not mad about it!

The Gavita rep told me that their DE fixtures were rated to run at all wattages without significant color change and the lamps break in over 6 months for the ideal color spectrum (for a HPS). This is in contrast with single end lamps like Hortilux that change color temperature and intensity after 4 cycles.

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I wish I could have visited your grow. I’m sure it was terrific :metal:.

But the Gavita rep was ignorant or lying :frowning:. Those data I shared on spectrum shifts with input wattage modulation aren’t from Gavita; they’re from a 3rd party.

It does take 100 hours of operation to reach burn-in. After that point, the lamps and spectrum don’t change without modulating the input wattage (or after its useful life span of ~10,000 hours, or 90% of burn-in PPFD). Those data I shared on spectrum shift were collected after the burn-in period.

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So much evidence I have physically observed is contrary to this study(400umol and you try to supplement :joy::rofl:). Nature itself has 10+% UV… some of the LOUDEST landraces with the BEST genetic traits come from places with a higher than normal UV index. The Kush Mountains, Cape of Africa, Alaskan Bush, etc.

In vitro gene expression is litterally controlled by ultra violet light. It is THE defense response to give you the best results. UV light exposure is a secondary effect. The Harmful raya never even reach the surface of the leaf. The UV is florescent into 400+nm it’s the magic of the cannabinoids… How do you think alot of new chroma works, and fraction finders.

I’m going to go ahead and toot my own horn by saying on average I am testing better and producing more baggable material per square foot utilizing out of spectrum Blues and Reds.

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Thanks for your expertise and resource sharing!

If we were hitting 55-60 grams per square foot (with 8-9 weeks veg) with under-driven (more red spectrum), I wonder how much it would affect quality and yield with properly powered lamps.

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FWIW, sunlight at ~4,500 feet above sea level (Logan, Utah) has 0.1% UV-B and 5.5% UV-A (unweighted). At high mountain elevations (9600 feet), UV-A is ⪅2.2%, and UV-B is ⪅0.1.5% (unweighted).

The problem with assuming outdoor plants are better because of UV is the lack of controls and the scientific method. All research so far, except for a poorly conducted study in 1987, found UV-B does not affect THC.

Besides the THC myth, there’s no other reason to use UV-B for indoor crops (besides seedlings). Any positive effects from UV-B are better attained through other means (regarding the photobiological effects of UVR8 and LOV photoreceptors.). It’s easy to overapply UV-B, which leads to reduced growth and photosynthesis, for example.

UV-A is beneficial for several reasons (i.e., phototropin and cryptochrome responses). However, we get those same benefits from 400-450 nm blue. So in most cases, UV-A isn’t necessary either.

I am not saying what you believe is incorrect, but without the scientific method and controlled experimentation, it’s only a belief.

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Thanks :slight_smile:

If you had reduced % red, you could have increased your PPFD, which leads to a significant increase in yield (up to about 1500-1600 PPFD compared to 1200 PPFD). With all other factors optimized and heavy yielding strains, ~80-85 g/SF all day long (85 g/SF = ~3lb/light at 4’ on center over 16 SF).

With really heavy strains, 1500-1600 PPFD, high CO2, crop steering, high air velocity, ~1.0-1.15 leafVPD, rockwool (or hydroponics) for multiple irrigation events per day, and pushing nutrients hard, you could have seen >90 g/SF.

That doesn’t even include biostimulants and cutting-edge technologies to further increase photosynthesis and yield.

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Correct assuming that is an average amount of UV. However when you change elevation, humidity, and other environmental factors, you increase the total index.

You can simply observe, test, and correlate genetic superiority to regions with higher than normal UV index. It’s seriously a no brainer. Like is evolution and the data lieing to us? UV region genetic are THE backbone of our current gene pool. It’s the one consistent environmental factor.

Everything we do indoors, we mimic from outdoor. We just increase the inputs that give us the outputs we want, even to unnatural levels. A majority of the things we do to these plants are a defense response. Heavy feed(increased productions), defoliation(internodal growth, budding/propagation) etc. etc. Giving the plant just what it needs to survive… Leaves you with well you know.

There are a lot of studies coming out. However you could always just try using the aforementioned wavelengths for yourself. I have a feeling once anyone uses high intensity UV A/B and FR will never go back.

Also these studies are almost always mediocre. Research scientists are not cannabis growers. They also are typically not a botanist a majority of those studies have a lot of moot data or are not conducted very well.

You can find studies that are explicitly pinning alot of the cryptochrome mechanisms to UVB light specifically.

https://www.nature.com/articles/s41467-020-15133-y

Obviously the study isnt revolved around cannabis, because mapping cannabis hasn’t been done yet.

However there eis most definitely something to be said about UV and it’s ability to force the expression of desirable traits.

Is it wierd that cry1 and cry2 protiens lack DNA repair?
Why wouldn’t the BLUE LIGHT protiens have dna repair? Why do they bind to damaged cells? What type of blue light damages DNA?

End rant

This isn’t perfect just FYI because usually the rating is %luminous wattage rather than umol of flux. Longer wavelength photons carry less energy and therefore 70% red in watts could be closer to 85% red in umol. Just FYI

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Great point! Thank you for mentioning it. :pray:

I’m used to having SPD data in photon flux ((Φq) PF; μmol/s) from an integrating sphere or photon flux density (PFD; μmol/s/m2) from a spectroradiometer. It slipped my mind SPDs are typically derived from absolute radiant flux (Φe) in W/nm or radiant flux density. For example, the SPDs in published studies and academic papers are often in PF of PFD units, not radiant flux. I’m not aware of SPDs derived from luminous flux (Φv) for grow lamps and LEDs (in the last decade).

These SPD data are all in photon flux units, not radiant flux:

Note that Dr. Bugbee presents B/G/R as a total of 100% (PPF), while UV and far-red are given as a percent of total PPF:

Here are datasets from a 2021 study in photon flux density units. Note that these authors provide the data as a percent of total PFD (280-800 nm). To compare these with Dr. Bugbees, we need to integrate blue through red (as % of PPFD), then find % of B/G/R of % PPFD, followed by finding UV and far-red as % of PPFD:

I plan to create a thread to compare and analyze SPD charts from any lamp or LED when I have a day or two of free time. Including converting SPD ranges (UV/B/G/R/FR) as W/nm to μmol/s.

Basically, an updated and improved version of Knna’s “bulbs comparison tool.” My method includes computer digitization of SPDs, not the hand method as Knna used. Hence, it greatly improves the digitization process’s accuracy, simplicity, and speed. Plus, Knna’s spreadsheet assumed lamp mfgs reported luminous flux. In contrast, today, they report photosynthetic photon flux. I have included updated and improved photobiological characteristics (e.g., far-red fraction and B:G of stomatal conductance action spectra) and technical performance characteristics. Hopefully, this coming weekend, but maybe not that soon.

Anyone can share SPDs in the thread, and I will digitize and analyze it for them.

I will use the SPD ranges in μmol/s to find the max PPFD based on photobleaching threshold of 700 μmol/s/m2 red [700(/% red/100)] for their specific luminaire. And at that point, they can use the simple equation I shared in this thread (PPFD*% red/100) to calculate the red range μmol/s/m2 at any PPFD if they want to use greater than 700 μmol/s/m2 red.

Ideally, we could collect a large dataset of red range μmol/s/m2. Under various environments, PPFD, and strains to develop guidance for growers who want to maximize PPFD without photobleaching.

I appreciate your comments and enjoy discussing these topics with you. :slight_smile:

Regarding ambient UV, before you posted this, I clarified the UV values (basing them % 280-800 nm). Previously, I used Dr. Bugbee’s values (based on % of PPF). See the following bullet point.

  • FWIW, sunlight at ~4,500 feet above sea level (Logan, Utah) has 0.1% UV-B and 5.5% UV-A (unweighted). At high mountain elevations (9600 feet), UV-A is ⪅2.2%, and UV-B is ⪅0.1.5% (unweighted).

The UV index isn’t the same thing as unweighted UV. Or the relative quantum response of UV-Bbe and UV-Abe weighted by the action spectrum for growth responses of plants. The UV index is UV weighted by the erythema action spectrum, based on the susceptibility of caucasian skin to sunburn. It would be best if you didn’t use the UV index as a guide for UV photon flux density for cannabis.

You have a point that most “research scientists are not cannabis growers,” but most growers aren’t scientists. So, growers who claim UV is God’s gift are doing so by belief, not robust experimentation. I would take the data from a published research study over what growers claim every day of the week. Plus, I don’t think it’s accurate to claim “these studies are almost always mediocre” and a “majority of those studies have a lot of moot data.”

I tested UV-B many years ago. But the technology was not suitable for plants (high-power reptile lamps), so the results can’t be trusted. Plus, back then, we didn’t have access to labs to quantify cannabinoids and terpenoids.

I plan to run controlled experiments with UV-B and UV-A once I have a spectroradiometer and the Conviron precision R&D plant growth chambers installed in our facility, the same kind used in plant research.

I would guess that because blue light doesn’t damage DNA, UV-B does. It’s the same reason blue light cryptochromes and red light phytochromes increase UV-B tolerance: UV-B damages cells. So the plants have to protect themselves from UV-B. That should tell you UV-B isn’t such a great thing for plants, especially plants that for generations have been grown indoors (so they aren’t acclimated to UV-B exposure). UV-B will always reduce growth rate and yield unless the photon flux density is so low it has no effects (like from a DE HPS). From the study you linked:

Cryptochrome blue-light and phytochrome red-light signalling are known to induce expression of genes that largely overlap with UVR8-induced genes. These co-induced genes include those associated with UV-B tolerance, such as CHS and FLS ; those encoding phenylpropanoid biosynthetic enzymes, which are important for the synthesis of flavonol glycosides that function as sunscreen metabolites; and PHR1 and UVR3 , which encode photolyases important for DNA damage repair5,17,30. This indicates that, in addition to cry1 negative regulation of UVR8 activity, cry1 as well as phyB may contribute to UV-B tolerance alongside UVR8

Regarding UV action spectra:

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UV indexing (based on human sunburning) is just the easiest way for me to articulate variable UV intensity quickly(mostly for third party and myself).

I’m kinda quirky and very unprofessional. I have a copywriter … Shrugs

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Last UV + FR run.

250w UVA 250w UVB 500w FR

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Nice pics :metal:

Do you have a control to compare those data to? Once I create the SPD comparison and analysis thread, if you provide the SPDs for the UV and FR luminaires and UV and far-red measurements I can tell you the approximate photon flux density you’re providing.

https://www.apogeeinstruments.com/red-far-red-sensor/

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I don’t really have a control to compare to. I work with a lot of growers, and a majority of them still use HID. Which isn’t even worth the comparison. Another issue is I exclusively grow from seed, and rarely grow the same thing twice.

I have made iterations, to my lighting, and I actually started using UV with CFL setups, and a high photon flux environment. Eventually moving to CMH, Kessil H380 and then custom bars. (Working on a fully integrated solution now. With better diode spacing and placement)

I do take a lot of spectral data, with my environmentals, and crop steer with growlink. I appreciate the offer. Pretty much all my experience with UV has been positive. It’s going to be hard to convince myself from paper that all my experience is wrong.

One more UV picture

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Nice pic :fire:…do you always grow regs? :wink:

I’m not saying you’re wrong. Nor have you proven you’re correct. However, without controlled experimentation, you cannot say that UV positively affects your garden compared to not using UV.

Without using the scientific method, “confirmation bias” is a significant factor:

Confirmation bias - Wikipedia.

Confirmation bias is the tendency to search for, interpret, favor, and recall information in a way that confirms or supports one’s prior beliefs or values. People display this bias when they select information that supports their views, ignoring contrary information, or when they interpret ambiguous evidence as supporting their existing attitudes. The effect is strongest for desired outcomes, for emotionallycharged issues, and for deeply entrenched beliefs. Confirmation bias cannot be eliminated, but it can be managed, for example, by education and training in critical thinking skills.

Another bias that you should consider is “observation bias.” Meaning drawing a conclusion by simply observing the plants without measuring or quantifying effects:

Observer bias - Wikipedia.

Observer bias is one of the types of detection bias and is defined as any kind of systematic divergence from accurate facts during observation and the recording of data and information in studies.

The definition can be further expanded upon to include the systematic difference between what is observed due to variation in [multiple] observers, and what the true value is. [E.g., two people may not give the same quailty rating to a flower’s visual appear, for example.]

And a third concern specific to botany is the “observer effect.” Whereby touching the plants, moving plants, watering by hand, getting the way of fans (reducing air velocity), etc., affect plant growth and skew the results:

The observer effect in plant science

What is known of observer effects

Plants have been widely documented to respond to mechanical stimuli such as wind and touch. Well-known and long-studied examples of these are carnivorous plants (e.g. Darwin, 1893), but nonspecialized plants are also sensitive and responsive to mechanical perturbation. Studies on this phenomenon, called ‘thigmomorphogenesis’ (Jaffe, 1973), have been conducted for several decades, revealing complex signaling and response pathways (Braam, 2005). Common thigmomorphogenetic responses include altered shoot elongation vs radial expansion ratios, delayed flowering, changes in chlorophyll content, etc. (see Biddington, 1986 and Cahill et al., 2002 for a review and a concise overview, respectively). In nature, such changes usually occur in response to wind and as a result of contact with neighbouring plants. Humans can unwillingly mimic these effects when studying plants, as several studies have shown that the mere act of touching plants by hand can have significant effects (Braam & Davis, 1990; Cahill et al., 2001). Moreover, in a considerable number of plant studies, measurements are not limited to touching plant tissue but include destructive sampling of leaves, roots, etc. It is apparent that if such (repeated) plant measurements, whether destructive or nondestructive, affect plant functioning, this could have far-reaching implications. Nevertheless, the attention given to such ‘observer effects’ in plant science has been limited.

Implications

If studying plants indeed implies involuntarily altering their morphology and/or physiology, then two main problems could arise. First, in studies on the state of nature (e.g. ozone damage in European forests, Ferretti et al., 2007), the presence of an observer effect could cause such assessments to deviate from reality, leading to erroneous conclusions. Second, in studies with an experimental treatment, a further problem arises if handling plants results in different effects in the different treatments (as already suggested by Cahill et al., 2001). Such a treatment × handling interaction would again distort the study’s results and conclusions, as it implies inflation or understatement of the treatment effects. As treatment studies are often future oriented (e.g. investigating the effects of elevated CO2 concentrations or increased temperatures), this could subsequently lead to an incorrect impact assessment of several global changes.

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