UV light supplementation, Who's using it with noticeable results?

Who's using UV with noticeable results? When do you introduce the UV into the grow? What on/off times are you using and do you change your timing as the grow progresses? How many 2' or 4' UV bulbs are you using for your size grow?

side by sides from what i remember back in the day did show marginal resin increase but it slightly reduced yeild due to the additional stress the plants experienced

If can you grow outside you won't have to supplement.

Skunkman says he never saw any positives from adding uv. I'll try to find u a link in the morning.

This is quote from sam_skunkman

I ran a test a bit like this 20 years ago.
I had several different clones of high THC varieties, and industrial hemp, and a wild cannabis variety from the mountains.
I placed each clone in rows of five so they had a chance to be exposed to too high of levels, medium, and low levels, depending on the distance from the light sources.
To cut to the chase, no increase compared to controls without UV-B.
In fact the plants closest to the lights were a bit zapped and had lower plant weights and lower Cannabinoid levels.
(In my own opinion using organic soils to increase root mass, which gives Cannabis with improved terpene yield and better Cannabis yield is much better then UV-B supplement.)

Tonygreen,
As for On page 31 if you scroll down you get into some good stuff and an interesting hypothesis about thc. They quote Lydon and Pate, but Pate did my experiments with me
setting them up and measuring the UV-B levels, as well as testing the results on our GC.
He was unable to increase the THC levels. Lydon thinks CBD can be converted to THC, but most Cannabis grown in the west has no CBD to start with. Lydon also only dosed the plants with UV-B for only 40 days, part of those when the plant was still in veg. He also said no increase in THC in hemp plants so I guess CBD does not get converted to THC by UVB?
We tried several times, zero THC increase. I have never seen any lab results that showed an increase in THC from UVB exposure, I have never seen Lydon's work replicated, except when I tried but got no increase in THC.
As for "Marijuana Optics" anyone that reads it and thinks it is science needs to stop smoking so much.
Get all three of Lydon's papers and try to repeat the work, if I remember correctly he did not even use clones for the work, for sure in the case of Lydon's 1985 Thesis, I think the 1987 paper also. I will go find the papers and re-read them....

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I can see Denali from my front window so when I did my UVB tests I started with the level calculated to be present at the top of the mountain.
The leaves were actually brown and shriveling by the second day.
Dropping the level down until the plants quit dying found no increase in THC production at all.

Between 50 uw (microwatts) and 200 uw the plants lost 3% to 20% of their yield.
Most plants left it at that, smaller and slower growth.

Some plants, while not increasing THC, delayed the onset of the high. And in addition, the high lasted longer. This happened more with select Sativa hybrids, although it is hit or miss because the breeding is done for THC levels rather than UVB sensitivity.

I use UVB from seedling to harvest, a couple weeks at the end never did make any difference, it is a whole life experience or the plant does not respond.

I like creeper weed and use 75-100 uw on all plants, the price is small. This is not enough for severe stunting but adequately creeperizes susceptible plants.

My current favorite is Obi-Wan, it sucks up UVB like a vacuum grabs popcorn.

Different Cannabinoid profile. Different high. Better high. Stronger high per mg of Cannabinoid. Higher ceiling.

Organics don't shine because of increased roots they shine because of elevating levels of contributors to the effect. Terpenes are mere influence not an actual effect, like a good song on the radio. Fats waxes acids etc, will increase the strength of your pot. Not more thc... A natural light spectrums is the icing on the cake.

Phaeton said:

I can see Denali from my front window so when I did my UVB tests I started with the level calculated to be present at the top of the mountain.
The leaves were actually brown and shriveling by the second day.
Dropping the level down until the plants quit dying found no increase in THC production at all.

Between 50 uw (microwatts) and 200 uw the plants lost 3% to 20% of their yield.
Most plants left it at that, smaller and slower growth.

Some plants, while not increasing THC, delayed the onset of the high. And in addition, the high lasted longer. This happened more with select Sativa hybrids, although it is hit or miss because the breeding is done for THC levels rather than UVB sensitivity.

I use UVB from seedling to harvest, a couple weeks at the end never did make any difference, it is a whole life experience or the plant does not respond.

I like creeper weed and use 75-100 uw on all plants, the price is small. This is not enough for severe stunting but adequately creeperizes susceptible plants.

My current favorite is Obi-Wan, it sucks up UVB like a vacuum grabs popcorn.

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Hello Phaeton,
I used a 4ft t5 uv bulb a few times. About 95µW/cm² according to the bulb.
No idea about thc levels, and didn't really notice any creepers.
But I noticed some heart palpitation weed in the uv batches that I didn't get in non uv batches, which I didn't care for.. any observations there?
Not a clone to clone comparison either, but same strains from same seeds.

How about fatter gland heads? I seriously didn't need a scope on a couple of those uv plants.
I switched the uv t5 to a red bloom bulb and moved it down, same cmh main lamp, and the nugs under the red really plumped and hardened a bit extra. I'll stick with that before uv again.

I USE UVB FLUO TUBEZ NOTICED SOME INCREASE IN TRICHS I THINK IS GOOD TO HAVE TO COMPLETE LIGHT SPECTRUM I CHANGE EM EVERY 4 YEARS AT START U HAVE TO PUT EM FAR AWAY CUZ THEY STRONG AFTER A FEW YEARZ THEY LESS STRONG. KEEP EM IN FLOWER ROOM ALL TIMEZ

z00t said:

I USE UVB FLUO TUBEZ NOTICED SOME INCREASE IN TRICHS I THINK IS GOOD TO HAVE TO COMPLETE LIGHT SPECTRUM I CHANGE EM EVERY 4 YEARS AT START U HAVE TO PUT EM FAR AWAY CUZ THEY STRONG AFTER A FEW YEARZ THEY LESS STRONG. KEEP EM IN FLOWER ROOM ALL TIMEZ

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I'm curious how you tested for "more trichs"?
And...
What kind of trichs were there more of?


Non Glandular Cystolithic trichomes don't add oil value to the plant but they do block & disperse light.

Bump.

Anyone else has experience with using UV(B) during flowering? Did you notice any benefits?

Is it worth the investment?

I read so many conflicting opinions about additional UV lighting.

My buddy flicks on UV light in flower every so often. His yields were never too good, not terrible, just I know we could do better. Quality was great though.

CannaRed said:

Skunkman says he never saw any positives from adding uv...

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that's not exactly true. what he said he didn't find uv-b increases thc level or makes cannabis stronger. i don't remember but probably he also said uv-b doesn't increase terpens either?

what he did say though is uv-b or outdoor grown weed he likes better in terms of high and he specifically mentioned "the higher in the mountain the better" in one of hashchurches.

so i'd say uv-b dispute is not quite settled.

as to uv-b supplemental lights you have to get plants used to it by slowly increasing time. it's better start at veg with a few minutes increment each day until you have it on for a few hours by peak of flowering. otherwise they develop sunburn just like people do when suddenly exposed to high uv in tropics.

peace.

I'd think that Sams account would be repeatable.


He is, after all, working with GW Pharma and has been experimenting since the 80's.

Thoughts on this then? Obviously plants do use uv to inform themselves of what growth strategy is best.

"When it comes to UV radiation, there are several other photoreceptors responsible for absorbing those wavelengths. Cryptochromes, phototropins, and Zeitlupe (ZTL) are the three primary photoreceptors that mediate the effects of UVA. UVB light is primarily mediated by the UV-R8 monomer.

It has been proven that UV light influences photomorphogenic responses including gene regulation, flavonoid biosynthesis, leaf and epidermal cell expansion, stomatal density, and increased photosynthetic efficiency. However, don’t forget that UV radiation can also damage membranes, DNA, and proteins.

That’s why many plants undergo photomorphogenic changes designed to protect them from these rays when their photoreceptors sense the presence of radiation. For example, numerous agricultural crops can synthesize simple phenolic compounds and flavonoids that act as sunscreens and remove damaging oxidants and free radicals.

In certain crop species, these*phenolic compounds*can be extremely desirable and it can be beneficial to the farmer to enhance this aspect of production.

How can growers use UV energy without causing damage to their crops?

Although this is a fairly recent field of botanical science, there are reports of dramatic increases in essential oil production by flowering crops grown under lightbulbs with higher UV output. Modern metal halide (MH) and*ceramic metal halide*(CMH) lamps often include precisely calculated and optimized amounts of UVA and UVB output.

High UV bulbs are generally recommended for use in the last two weeks of a flowering cycle once the generative development is completely established. This allows for a crop to continually develop in size and growth vigor while also protecting the flowers and canopy with increased resin production.

Like all aspects of horticulture, balance is the key to effective UV use. Too much or incorrect ratios of*PAR/UVA/UVB will not help, but the correct amounts could encourage some incredibly useful results.

Timing is also an important part of UV application. When given UVB throughout the entire growth cycle, sensitive plants such as leafy greens often display reduced growth (plant height, dry weight, leaf area, etc.) and photosynthetic activity.

Generally, the effectiveness of UVB also varies both among species and among individual strains or genetics of a given species. If you’re looking to utilize UV in your garden, it’s worth discussing with your local hydroponics store about the best approach for your chosen plant species.

Overall, it’s worth discussing and researching the best applications of UV in your garden whilst catering to your specific plant’s physiological requirements.

If we use this technology correctly, we can enjoy the delicious benefits of plant sunscreen. This means your flowers will smell better, your fruit will taste superior, and your herbs will have a higher potency in the kitchen.

Enjoy the tan!"



https://www.maximumyield.com/tanning-your-plants-the-curious-effects-of-uva-and-uvb/2/2990

This thread is really interesting to me. I had read everywhere that UV increases THC potency, even in Rosenthal's Marijuana Grower's Handbook, which I've found to be accurate for other topics. I'm about to invest in supplemental UV lights for all my lights so if anyone knows of a valid test done side by side showing UV light does nothing please point me to it, because I'd rather save myself a lot of headache, money, and trouble not adding UV to all my setups.

This is what I have gathered, I really hope we can get a definitive answer from this thread sooner or later.

Pictured Is 100nm to 1000nm



The Ultraviolet (UV) spectrum ranges from about 100 nanometers (nm) and 400 nm.

UVA, from about 315 nm to 400 nm, is an extension of the deep blue light spectrum and is included in most artificial light sources. Some level of photosynthesis occurs in this range.

UVB, from about 280 to 315, is somewhat damaging to plants in high levels and causes sunburns on humans. UVB causes damage in plants in much the same way as it damages human skin, and plants created defenses against UVB in the form of a protein called UVR8.

UVC, from about 100 nm to 280 nm is highly damaging to all living things. This is often used in sterilization and killing bacteria.

Photoreceptors like phytochromes mediate many aspects of vegetative and reproductive development and are responsible for absorbing UV, blue, red and far-red light. Cryptochromes, phototropins, and Zeitlupe (ZTL) are the three primary photoreceptors that mediate the effects of UV-A.

UV-B light is primarily mediated by the UV-R8 monomer. UVR8 is a protein molecule which senses UV, and then “tells” plant cells to change their behavior. Exactly how UVR8 molecules sense UV was recently discovered and is pretty interesting. UVR8 is what chemists call a “dimer,” which simply means that it’s made of two structurally similar protein subunits. When UV light hits the two protein subunits in UVR8, their charge weakens and they break apart. After the protein subunits break apart, they head to the cell nucleus to deliver their information. One of these changes caused by this reaction is very important in your cannabis garden. UV stress stimulates cannabis’ production of chemicals via the phenylpropanoid pathway, specifically malonyl-CoA and phenylalanine. Cannabis uses malonyl-CoA to make Olivtol, which it in turn uses to make THC. So finally the specific pathway which increases Cannabis potency when exposed to UV light is understood, and we can use this information to our advantage.

There is a threshold where the damage caused by high level UVB will exceed any benefits in potency.

Black Dog LED Says:

From our own research grows, Black Dog LED has demonstrated that UVA light alone can increase THC and CBD production in Cannabis plants. The UVA increases production of secondary metabolites such as THC, CBD, terpenes and flavonoids but without the negative effects of UVB light. The combination of UVA and UVB light (from a standard "reptile bulb" fluorescent light) also increases THC and CBD production, but the inclusion of UVB in the light has noticeable detrimental effects on plant growth compared to only UVA.

From our experimentation, having about 3.5-4% UVA (as much as natural sunlight at noon) and 96-96.5% PAR light is about the right ratio for maximizing quality and canopy penetration without overly stressing the plants from too much UV. This is why we've engineered the Black Dog LED Phyto-Genesis Spectrum™ to only include UVA light, without any UVB wavelengths.

Link To Sources:

https://californialightworks.com/uvb-light-and-thc-potency/

https://www.blackdogled.com/blogwhich-is-better-uva-or-uvb/

https://alliedscientificpro.com/web/content/product.attachment/1256/product_attachment/UV%20in%20Plant%20Photobiology%20-%20White%20Paper

https://medicalmarijuanagrowing.blogspot.com/2013/02/uvb-uva-lighting-study-results.html

https://medicalmarijuanagrowing.blogspot.com/2013/06/updated-uva-uvb-medical-marijuana-study.html

https://medicalmarijuanagrowing.blogspot.com/2013/12/how-to-achieve-uniform-thc-and-cbd.html

https://medicalmarijuanagrowing.blogspot.com/2014/09/myth-or-magic-next-uva-uvb-cannabis.html

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1751-1097.1987.tb04757.x

Research papers on other plants furthering an argument it is probably important in some capacity.

Improvement in Flavonoids and Phenolic Acids Production and Pharmaceutical Quality of Sweet Basil (Ocimum basilicum*L.) by Ultraviolet-B Irradiation

https://www.mdpi.com/1420-3049/21/9/1203

*

Irradiation for 8-h led to higher TFC, TPC and individual flavonoids and phenolic acids than for the other durations (4, 8, and 10-h) except for cinnamic acid, which was detected at higher concentration when irradiated for 6-h. Irradiation for 10-h significantly decreased the secondary metabolite production in sweet basil leaves. CHS activity was induced by UV-B irradiation and highest activity was observed at 3.60 W/m2*of UV-B irradiation.

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The effects of UV-B stress on the production of terpenoid indole alkaloids in Catharanthus roseus hairy roots.

https://www.ncbi.nlm.nih.gov/m/pubmed/19479674/

In nature, plants generate protective secondary metabolites in response to environmental stresses. Such metabolites include terpenoid indole alkaloids (TIAs), which absorb UV-B light and serve putatively to protect the plant from harmful radiation. Catharanthus roseus plants, multiple shoot cultures, and cell suspension cultures exposed to UV-B light show significant increases in the production of TIAs, including precursors to vinblastine and vincristine, which have proven effective in the treatment of leukemia and lymphoma. Here, the effect of UV-B light on C. roseus hairy roots was examined. Analysis of alkaloid concentrations up to 168 h after UV-B exposure shows significant increases in the concentrations of lochnericine and significant decreases in the concentration of hörhammericine over time (ANOVA, P < 0.05).

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This one is a review but really interesting:

Effects of UV-B-Mediated Induced Secondary Metabolites on Plant Defenses Against Herbivores

Interactive effects of UV-B light with other abiotic factors on plant growth and production of plant secondary metabolites.Under high Photosynthetic active radiation, UV-B light increases the net plant photosynthesis in several plant species. Higher production of flavonoids can be induced under both UV-B and high PAR in young and old plant leaves. UV-A radiation has a positive effect on the photosynthesis when plants are exposed to UV-B. Higher epidermal flavonoids are detected in plants under both UV-A and B radiations in some plant species. Exposition of plants to blue light prior or subsequent to UV-B also increases the acclimation responses to UV-B by reducing the degradation of photosynthetic pigments. Antagonistic responses between UV-B radiation and low-Red:far-red ratios have been reported. UV-B can inhibit the shade avoidance associated responses under low-Red:far-red ratios. Likewise, a low-Red:far red ratio can reduce the UV-B-mediated induction of plant flavonoids. Increased temperature increases acclimation of plants to UV-B, though it can reduce the UV-B-mediated induction of plant phenolics. Under combined UV-B radiation and increased temperature, however, higher emission of the plant volatile isoprene can be detected in some plant species. Similarly, under UV-B and water stress conditions, a positive effect on plant survival is reported. Production of UV-B-induced flavonoids can be modulated by the application of UV-B prior or subsequent to water stress.

Interactive Effects of UV-B Light with Abiotic Factors on Plant Growth and Chemistry, and Their Consequences for Defense against Arthropod Herbivores

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Suggesting the benefits of UV supp. might differ depending on some of the factors detailed in the above study, like blue light conc. or water stress or Red:Far red like conc. etc

Just food for thought really. I kinda think now, having just spent a few hours going through research papers, that UVA/B might actually change terpenes, flavonoids and sesquiterpenes etc into other forms which suggests to me UV may cause quite specific changes in taste in different genetics depending on how sensitive/reactive the chemistry was in that line to UV and if the rest of your grow setup actually allows the plants to use the UV for anything beneficial as we perceive it.

It's not going to be a single band UV light. I think it'll need to be more full spectrum UV not just one single band in whatever nanometer. The UV lights I've seen don't cover enough of the spectrum is why I'd say some/most don't see improvement. A UV test from 20 years ago doesn't really count in my mind either. Hortilux MH Blue is the best thing at this time not supplemental UV lights. UV, Blue and possibly Far Red may need to be boosted to see the same benefits seen from the MH blue. Some LED's are getting close to going full spectrum UV very soon I'd say. I swear by the MH Blue but must admit I think it's the UV and Blue light that gives the boost I'm looking for. The MH Blue does have that Far Red that seems to be the in thing with the grow light companies recently?