2 posts were merged into an existing topic: Diy Borophyll?
I have twin hlg600rs with uvb stips going down the center of the lamp. I can say , over gotten colors I never knew existed in cannabis with this set up. Eventually I will have 4 with all uvb but keep one tent without it . For early flower , as well as the prevent any sexing mistakes.
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I do use UV but only use during the last 4 weeks of flower — FYI
Finally pulled the trigger on a uvb California light works, will report back on how it works.
Btw they have some coupon code on the site for 25% off the us system lights right now, got there small one which is usually 115$ for 85$ shipped.
They recommend 3’ above canopy which I certainly don’t have room for so I guess I’ll have to run it for short bursts and pray.
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Hello @Northern_Loki
I’m very impressed with your efforts and how well you explain your findings! Especially for those who do not have a background in these topics. It’s very kind of you to share these data.
Would you mind weighting the RAY44 UVSpec SPD with the Flint and Caldwell UVB/A action spectrum for growth responses of higher plants, and posting it here? I was planning to do so once I acquire the RAY44 from Fluence, and the MetaRail from Agricultra, but that won’t occur until later this summer. By chance, do you have the MetaRail?
The UVA/B action spectrum for growth responses of higher plants is based on the work by S.D. Flint and M.M. Caldwell from their 2003 paper: A biological spectral weighting function for ozone depletion research with higher plants, Physiologia Plantarum.
Here is the UVA/B action spectrum for growth responses of higher plants based on Flint and Caldwell’s 2003 paper (also at the bottom of this post), thanks to the National Science Foundation (NSF): http://uv.biospherical.com/Version2/doserates/Flint.txt
To this post, I have attached a few other relevant papers you may enjoy if you have not seen them.
Flint, S.D. and Caldwell, M.M. (2003), A biological spectral weighting function for ozone depletion research with higher plants. Physiologia Plantarum, 117: 137-144.
Flint, S.D. and Caldwell, M.M. (2003), Field testing of UV biological spectral weighting functions for higher plants. Physiologia Plantarum, 117: 145-153.
Flint, S.D., Searles, P.S. and Caldwell, M.M. (2004), Field Testing of Biological Spectral Weighting Functions for Induction of UV-absorbing Compounds in Higher Plants. Photochemistry and Photobiology, 79: 399-403.
Solar UV irradiation and the growth and development of higher plants, In: Photophysiology, edited by A.C. Giese, Volume 6, Chapter 4, pp. 131 - 177, 1971
Attached papers:
A biological spectral weighting function for ozone depletion research with higher plants.pdf (227.8 KB)
Field testing of UV biological spectral weighting functions for higher plants.pdf (239.2 KB)
Field Testing of Biological Spectral Weighting Functions for Induction of UV-absorbing Compounds in Higher Plants.pdf (636.9 KB)
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Good stuff. Funny thing is, I do have a Metarail but it’s in rough shape and without a power supply (got it off ebay) and, as such, have not done much with it. Those seem hard to come by.
Unfortunately, I’m behind on a number of things and have limited time at the moment to run the spectra against the action spectra … but I can supply the spectrometer data for the Fluence Ray44 fixture if that would be useful to you. Otherwise, I can probably get to it once I’m a bit more free’d up. I’ve bookmarked your post as well for future reference. Remind me.
This is a zip file containing an excel spreadsheet, change the extension to .zip
PAR_Calc_UV_Spec.zip.pdf (1.2 MB)
Alternatively, if you’re experienced with c/c++, you can extract the raw data from the first two columns in the spreadsheet and run it through the source code I have over here:
The Caldwell expression is already coded though unused / untested in the following function within that source
double spectrum::calculate_flint_action_spectra(double wavelength)
In addition, there are a couple of other routines in there as well
double spectrum::calculate_caldwell_action_spectra(double wavelength)
You’d need to call such routines and apply the action spectra to the calculated irradiance by wavelength (data from the first couple of columns extracted from the spreadsheet). And example where that is performed is in the calculation of PAR and YPF action spectras.
Same can be done in the excel spreadsheet but it’s more difficult to comprehend since it’s just my working spreadsheet and not intended to send around, work backwards from the graphs within the first sheet to see how the PAR or YPF masks work.
Also, if you haven’t seen, here is some general spectrometer results that were the output from the excel worksheets and the source code, over here:
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@all,
According to these recent papers, I’m sorry to say that UV-B irradiation is unlikely to increase cannabinoid biosynthesis. However, UV-B and UV-A do affect (increase and decrease) other secondary metabolites (e.g., terpenoids), pigments, and, e.g., important cryptochrome-mediated photobiological and morphological responses.
The old paper on UV-B and cannabis by Lydon et al. (1987) that many companies and people use to justify claims of THC increase is likely untrustworthy. The authors’ use of filters may not have been effective, thereby skewing their results by adding UV-A. Also worth noting is the paper quantifies UV-B irradiance using UV-Bbe (i.e., the CIE erythema action spectrum) rather than using unweighted UV-B or a relative quantum response of higher plants to UV-B. Biologically effective UV-B (“UV-Bbe”) is generally UV-B weighted using the action spectrum for vitamin D synthesis by humans.
Please refer to the two following papers and my comments. I attached the second paper this post; the first is too large (but I included the full text link below). I also attached a few of other on-topic papers you may enjoy:
#1
Rodriguez-Morrison, V., Llewellyn, D., & Zheng, Y. (2021). Cannabis inflorescence yield and cannabinoid concentration are not increased with exposure to short-wavelength ultraviolet-B radiation. Frontiers in Plant Science, 12. doi.10.3389/fpls.2021.725078
Before ultraviolet (UV) radiation can be used as a horticultural management tool in commercial Cannabis sativa (cannabis) production, the effects of UV on cannabis should be vetted scientifically. In this study we investigated the effects of UV exposure level on photosynthesis, growth, inflorescence yield, and secondary metabolite composition of two indoor-grown cannabis cultivars: ‘Low Tide’ (LT) and ‘Breaking Wave’ (BW). After growing vegetatively for 2 weeks under a canopy-level photosynthetic photon flux density (PPFD) of ≈225 μmol⋅m–2⋅s–1 in an 18-h light/6-h dark photoperiod, plants were grown for 9 weeks in a 12-h light/12-h dark “flowering” photoperiod under a canopy-level PPFD of ≈400 μmol⋅m–2⋅s–1. Supplemental UV radiation was provided daily for 3.5 h at UV photon flux densities ranging from 0.01 to 0.8 μmol⋅m–2⋅s–1 provided by light-emitting diodes (LEDs) with a peak wavelength of 287 nm (i.e., biologically-effective UV doses of 0.16 to 13 kJ⋅m–2⋅d–1). The severity of UV-induced morphology (e.g., whole-plant size and leaf size reductions, leaf malformations, and stigma browning) and physiology (e.g., reduced leaf photosynthetic rate and reduced Fv/Fm) symptoms intensified as UV exposure level increased. While the proportion of the total dry inflorescence yield that was derived from apical tissues decreased in both cultivars with increasing UV exposure level, total dry inflorescence yield only decreased in LT. The total equivalent Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) concentrations also decreased in LT inflorescences with increasing UV exposure level. While the total terpene content in inflorescences decreased with increasing UV exposure level in both cultivars, the relative concentrations of individual terpenes varied by cultivar. The present study suggests that using UV radiation as a production tool did not lead to any commercially relevant benefits to cannabis yield or inflorescence secondary metabolite composition.
Regarding the above study, one point to consider is that the authors didn’t use high irradiance, limiting themselves to a peak of 400 PPFD in the flowering phase. The low PPFD is bound to increase the adverse effects of UV-B and UV-A on plant growth. PPFD must be high when supplementing UV, especially UV-A. Therefore, this paper is probably of limited real-world value, but that doesn’t negate their findings that UV-B didn’t increase cannabinoid biosynthesis.
#2
Llewellyn, D.; Golem, S.; Foley, E.; Dinka, S.; Jones, M.; Zheng, Y. Cannabis Yield Increased Proportionally With Light Intensity, but Additional Ultraviolet Radiation Did Not Affect Yield or Cannabinoid Content. Preprints 2021, 2021030327 (doi: 10.20944/preprints202103.0327.v1).
Cannabis (Cannabis Sativa L.) is now legally produced in many regions worldwide. Cannabis flourishes under high light intensities (LI); making it an expensive commodity to grow in controlled environments, despite its exceptionally high market value. It is commonly believed that cannabis secondary metabolite levels may be enhanced both by increasing LI and by exposing crops to ultraviolet radiation (UV). However, there is sparse scientific evidence to guide cultivators. Therefore, the impact of LI and UV on yield and quality must be elucidated to enable cultivators to optimize their lighting protocols. We explored the effects of LI, ranging from 350 to 1400 μmol m-2 s-1 and supplemental UV spectra on cannabis yield and potency. There were no spectrum effects on inflorescence yield, but harvest index under UVA+UVB was reduced slightly (1.6%) vs. the control. Inflorescence yield increased linearly from 19.4 to 57.4 g/plant and harvest index increased from 0.565 to 0.627, as LI increased from 350 to 1400 μmol m-2 s-1. Although there were no UV spectrum effects on total equivalent Δ9-tetrahydrocannabinol (T-THC) content in leaves, the neutral form, THC, was 30% higher in UVA+UVB vs. control. While there were no LI effects on inflorescence T-THC content, the content of the acid form (THCA) increased by 20% and total terpenes content decreased by 20% as LI increased from 350 to 1400 μmol m-2 s-1. High LI can substantially increase cannabis yield and quality, but we found no commercially-relevant benefits of adding supplemental UV radiation to indoor cannabis production.
The critical distinction in the second paper (Llewwllyn, et al., 2021) is THC-A, the acid form of THC that comprises the vast majority of total-THC (i.e., THC-A + THC) within inflorescence (flowers), was not increased from UV-B irradiation. They also found THC, the neutral form that gets us “high,” increased by 30%, which sounds like a lot until we consider THC comprises a tiny portion of the total-THC. Therefore, the reported increase in THC is pretty inconsequential. I suspect the increase of THC may be caused by UV-B photooxidative decarboxylation of THC-A into THC, because total-THC was not increased. It’s also worth noting that this paper is in pre-print and is not peer-reviewed (yet).
Attached papers:
Current status and recent achievements in the field of horticulture with the use of LEDs.pdf (397.4 KB)
Hoogenboom, J. (2022). Horticultural Management and Environment Control Strategies for Cannabis (Cannabis sativa L.) Cultivation (thesis). University of Guelph, Guelph.
^^^ This is 
% and impressive thesis, including her results on CO2 supplementation.
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Awesome, thank you! I will do so and share in your Lighting Spectral Data thread once completed. I would be willing to loan you the new MetaRail v2.0 for your analysis once they are purchased (not until later this year).
That’s funny about the Caldwell action spectrum. I was going to share it in my post but I figured the updated version with Flint was enough. And know I think about it, I can remove the full action spectrum I included in my first post considering you have it already.
Excellent! I haven’t seen that, but I will read it tomorrow. I found this forum earlier today when searching for spectrometer data for the Fluence SPYDR 2H. That search lead me to your stellar thread on the SYPDR 2P, which then lead me to this thread.
If you haven’t tested Gavita DE HPS 1000W yet, I’ll share spectrometer data in your SPD thread, from 357 to 830 nm on <1 nm increments.
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Here’s an email response from Agricultra regarding their MetaRail. The study mentioned in the email is referring to the first one I posted regarding UV-B and cannabinoids (Rodriguez-Morrison, Llewellyn, & Zheng, 2021) [emphasis mine].
I am somewhat familiar with the study you mention. There were more issues I had with the study Design of Experiment other than what you rightly point out. As I also recall the UV light also had a noteworthy amount VIS light associated with it which is a considerable flaw. Lastly, we would not run UV with the VIS spectrum this tends to give poor results…although not always it depends on the dose, intensity etc. We offer access to the knowledge gained in our field trials to those that purchase our lights.
Because we use discrete UV diodes for each channel the normalized SPF is pretty basic. There is a peak at 285 with very narrow shoulders on either side and there is another peak at 385 with narrow shoulders. Peak value of UVB approx 0.5 W/m^2 and a peak value of around 15 W/m^2 for UVA.
Yes you will need a diming controller for the lights, the drivers are Dali based, there are a couple of options for you.
Yes each channel (UVA & UVB) can be operated separately or together.
No, each channel is discrete (285nm for UVB and 385nm for UVA). There is no overlap between the two UV Ranges unless you run the two channels together.
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Skimming this currently, pretty good. Some of the observations confirm prior work and there are also some interesting new observations under her trial conditions. (one thing I’m surprised with though is her running a numbers of trials at a low-PH of 5 or less).
Some of these papers could be up for individual and topical discussion under the advanced techniques category, FWIW.
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Hey Northern_Loki , I will keep that in mind. I have many recent studies from 2018 to 2022 that would do well as individual threads in that category. Once I have a little free time, I could add some threads. And maybe do a Zotero dump to share all the studies and white papers I have on these topics (many hundreds).
I also found the pH work interesting. A few considerations for low pH nutrient solutions include:
- Macros and micros that have increased or reduced uptake at lower pH, including those which can easily cause phytotoxicity, including Cu, Zn, Mn, and B.
- The effect pH plays on various chelators and their chelation strength.
- For rockwool users, Grodan warns that pH below 5.0 may degrade the rockwool fibers.
I run rockwool at pH 5.25 to help keep silicon in the orthosilicic acid form and help prevent Pythium spp. but I also run about 1:15 NH4+:NO3- to ensure the soilless solution pH does not drift below pH 5.0. I’m about to have a group call with the eastern US rep for Grodan and a Grodan Technical Advisor, and I plan to ask about running pH below 5.0
You may enjoy these studies if you haven’t seen them before. And I promise this is the last off-topic post I will make in this thread 
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So I’ve got the hlg30 uva for my next flower run, I’m considering throwing in either a solacure or cali light uvb at the top of the tent, I can maintain a short enough canopy(probably, maybe😅) would this be overkill? Or will I grow the frostiest buds I’ve ever seen?
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Depends. UVA can be left on 12/12 through whole flower cycle and is said to Increase trichome production. UVB is much more damaging and need to be done in short bursts. Some say it has the potential to increase potency if used correctly. So there will likely be some trial and error to dial it in.
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@EugeneDebs420 , I have and use that supplement light. I had it in a grow room 5x8. The frost on the one side of room was noticeable Imo. Right now it doesn’t work with my setup but I think you will be happy
Solacure recommends 15 mins on 45 mins off during lights on during flowering… now this makes sense…at 1st glance… it seems like they just want you to burn lights up faster… but then you consider the triggering that needs to be caused causing the plant to grow more trichomes or more on each already existing trichome… either way… it makes sense… 15 on… trigger it… 45 off… grow the trichomes … 15 on trigger it. 45 off… resin production… I think they are on to something with this method 
because if you leave it on… then your just melting away what you previously grew… kind of 1 step forward 2 steps back… seems like just enough to trigger the need for resin production (plant sunscreen) is best for increasing trichomes and sizes of existing trichomes… just want to trigger this reaction over and over without actually hurting/degrading existing trichomes… this is talking uvb by the way… I feel like uva is more of a strengthener…
So I’ll be getting a reptile uvb bulb for my 2x2
So far I’ve understand that the 10 version means 10%uv
Not sure ty split on uvb
Any suggestions?
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Thanks also gonna tag @Tao who was dropping the knowledge here
Just looking for a cheap uvb option, so probably bulb(coz I don’t have a light to put a tube in)
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If your lookin cheap go secondhand eBay etc for Arcadia t5 holder
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They do
Bloomspect has them
UV
And cheap
Good lights
Used mine 3 years so far
Even the new units have it.
I picked up several just for uv
30ish bucks a pop for the
250 watt equivalent
Amazon
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