UVB lights?

Discussion in 'Growing Marijuana Indoors' started by 13ronin, Feb 10, 2009.

  1. Just popping around here and bumped into a couple people talking about using UVB lights in their grows? Why? I can't seem to find any dedicated posts on it in the stickies and have never heard of it till now. What are the benefits it gives?
  2. #2 BigBadBuds, Feb 10, 2009
    Last edited by a moderator: Feb 10, 2009
    The rationale i've read is this...THC acts as UV blocker and strains that come from tropic regions, with more UV exposure, produce more THC.

    The british used hemp to make their ropes and sails for ships, they began growing it in more tropic colonies becuase the labor and land was more abundant. What happend after a few seasons was that the crop began to grow shorter, less branchy with more resin then what they prefered to use to make the material they needed.

    I'm not so sure that a UVB bulb will help a plant produce more THC, but it will help breeders select the plants that produce more THC and use them for seed production.

    There is a thread somewhere on GC that explains it better then i can recollect. I will try to find it and post the link here.

  3. go hit search on GC, all growing forums, or go to youtube and search the same thing

    "THC, UV-B, and ME"

    its a video, youtube, from "The Grow Show" with Marijuana Man. He goes WAY in depth in that video. Explains THC synthesis, other cannabinoids relationship to THC, and how UV-B light effects all of it.

    and believe me, it effects ALL of it. Go watch that vid, read the thread its linked in here on GC, and then go buy yourself a uv-b CFL.
  4. Cool vid, i'm convinced.

  5. yeah, its an awesome vid. tons of great info, and the dude actually presents it well and explains everything in incredible detail. real easy to digest
  6. I am not convinced that UVB produces more THC. The idea that UVB improves THC content appears to have derived from only one scientific study (see below):

    [Lydon, J., A. H. Teramura and C. B. Coffman (1987) UV-B radiation effects on photosynthesis, growth and cannabinoid production of two Cannabis sativa chemotypes. Photochem. Photobiol. 46, 201-206.]

    It appears to me that all of the interest in using UVB to improve THC yield stems from that one study. The video by Marijuana Man, the forums dedicated to UVB lights, and other articles all use the same study as a reference. The articles, forums, and stories about UVB has been growing ever since. This is how urban myths are created.

    Don't get me wrong, I'm not saying that UVB light doesn't cause an increase in THC, only that I don't see any good evidence for it.

    I think it's important to realize that one study does not make a convincing case. Many a scientific study that first appeared convincing turned out completely wrong upon further investigation. For a scientific fact to be established, the study needs to be repeated, and the more the better. Unfortunately, in another study by Brenneisen (1984) "showed only a minor difference in UVB absorption between THC and CBD, and the absorptive properties of CBC proved considerably greater than either. Perhaps the relationship between the cannabinoids and UV-B is not so direct as first supposed." (see: Chemical ecology of Cannabis by David W. Pate)

    Now if CBD and CBC works as good or better than THC for UVB blocking, then what need of THC? Nature does waste resources for unnecessary chemical production. I suspect that THC has another purpose (see below). Moreover, at least one grower grew cannabis from seed all the way to vegetation by using *only* UVB lights, long before stalked trichomes became apparent. The leaves turned dark green with a slivery finish which suggests that cannabis has another method of protecting itself from UVB: by reflection. Moreover this protection (if that is what it is) appears to have come from the leaf itself instead of trichomes.

    It's also interesting to note that THC *absorbs* UVB. How in the world does this protect the plant? Absorption means heat and this doesn't make sense to me how this can protect the plant. Wouldn't you want a reflector instead of an absorber?

    The other claimed increase of THC by the application of UVB comes from amateur growers who swear that UVB light works. Unfortunately, anecdotal evidence is not considered scientifically trustworthy simply because of unreliable test methods, placebo effects, and psychological variability.

    Also the theory about UVB in environmentally friendly areas for cannabis does not make sense to me. Marijuana Man, for example, points out that UVB radiation occurs greater in tropical and mountainous areas where it's known that high THC cannabis grows. Well, yes there indeed is some correlation, but as many scientists warn: correlations do not prove causations. This is one of the most ignored fallacies made by humans.

    Moreover, the correlation does not always work. For example, many have pointed out that some Mexican and Brazilian weed is very poor in THC even though it grows in a tropical climate high in UVB.

    I think there is a much stronger correlation for high THC than UVB and that is LOW humidity. Now, of course this correlation also does not prove causation, but if you want correlations, low humidity, I think, serves a stronger case than UVB for increasing THC.

    Note that humidity tends to decrease with altitude. Mountains, not only provide more UVB but also dry conditions. Many deserts also have high UVB, but also low humidity. Poor Mexican weed, however, is gown, many times in low altitude humid climates. Perhaps that is why it is considered a poor smoking weed.

    So why would low humidity increase THC? Because it appears that one of the purposes of glandular trichomes is to protect the plant from desiccation. The sticky oil coats the leaves and protects the plant from becoming too dry, (similar to the way cacti protect themselves). And whenever you have more trichomes, you also get more THC along with the ride. As for the purpose of THC, that is still under study, but some suggest that it is there to intoxicate (or kill) small predators that might eat the cannabis leaves.

    It's also interesting to note that the evolution of cannabis has spread from Indo-China, India, Arabia, Moroco, Afghanistan, all arid dry areas. Most of the best strains are naturally grown in dry arid climates, even where there is little UVB.

    It's also noteworthy that cannabis usually flowers in Autumn or early winter where the days are shorter and the sunlight contains very little UVB. If THC is to protect the plant from UVB, then why-oh-why doesn't it produce THC mostly during the summer months when UVB is the greatest? It doesn't make sense.

    Moreover, indoor growers around the world produce high THC plants without using UVB at all. At all! However, the best growers do decrease humidity in the last few weeks of flowering to increase THC levels. So it seems to me that humidity has a much stronger correlation for high levels of THC than UVB.

    And could not the Lydon, et al, study have inadvertently created a dry leaf condition by exposing the plants to high levels of UVB? I think it's something to think about.
  7. sweet jesus, smart people stuff makes my head hurt...

    nice read thanks for sharing ...
  8. #8 amoril, Feb 13, 2009
    Last edited by a moderator: Feb 13, 2009
    youre a smart guy, but I think youre making some poor assertions. you posted way too much, so im gonna go line-by-line, so to speak....

    well, its one study vs. none disproving it. Ill address your example lower, but Ive read it previously, and feel that its much less applicable to 'pharmaceutical-grade' cannabis.

    this study is testing the three cannabinoid varietes in cannabis, THC, CBC and CBD. however, the sample of cannabis they used is hemp-grade, meaning it has an incredibly lowered cannabinoid content overall. Gas chromotography results on that test showed like 2% THC as the BEST result, others as low as 1.4 iirc. I dont know about you, but i'd pass on that shit, more headache than stone. But to each their own. Now, if this is the cannabis you want to base your assumptions on, please go ahead and do so. Me? Ill go with something a little closer to "potent"

    the study you site is your source for this argument, and I dont agree with the warrant there. Also, given the sample set within the study (assuming it were applicable), I dont think there's enough evidence to assume that CBC or CBD are more efficient at blocking UV-B light, only to say that they are similar. Given that, they do each have different characteristics and reactions with predator (this is one of the uses for the trichomes, protection from predators). Having more than one present cannabinoid may provide more coverage, so to speak.

    ok, the reflection wasnt the leaf. It was, 99.9% sure, trichomes. Just because "stalked" trichomes arent present, the assumption that resin glands ARENT present is false. They are there. The fact that they were mroe obvious than normal indicates that the UV-light was in fact forcing resin glands to propogate at an earlier point.

    the dark green could very easily be from an abundance of nitrogen mixed with the wrong spectrum (probably a terrarium light at 5000k or lower)

    well, good luck finding a plant that naturally reflects UV-b light. wont happen. What does happen is the plant has adapted a method to protect its seed from penetration and genetic mutation by uv light. Fruit comes in a lot of forms, and for a lot of reasons. Think about an apple. Now, think of the trichomes as the apple, around the seeds, and you see where im going.

    The cannabinoids do absorb the light, and that does transfer into a little heat. Note, a little. Not nearly as much as is already being produced by your lights. If you reflect light, you dont get the energy from it (perfectly reflected light maintains its energy level, therefor the plant gets NONE of it, like green spectrum light). Cannabinoids go through conversions into various forms, THC being our favorite. the energy for this has to come from somewhere, it just happens to be from light.

    precisely why I feel that your friends exclusive UV light grow was flawed. Did he use flouro/cfl, or halogen bulbs? total watts? color temp? what grow medium? was it pH balanced? LOTS of things could have contributed to his *individual* experience.

    Yes, one grower's results are very anecdotal. However, Ill agree with TONS of *very experienced* growers who all have noticed the effects of UV light on their otherwise consistent crop.

    if there is a correlation between humidity and thc, its more likely an indirect one. As in, low humidity but with an ample water supply, weed will transpire at an accelerated rate, speeding up overall metabolism, and possibly result in more THC production.

    However, I cant come up with a logical thought process to deduce how low humidity would increase THC directly. If you feel that it does, please do a side-by-side. Clones, same light/nutes, one in a room with moderate-high humidity, and one in a room with a dehumidifier. I bet that unless you provide more water to the de-humid plant, your results will change your mind ;)

    Logical fallacy. You skipped a few steps. Most of the mexican weed Ive smoked is decent through mindblowing. Im relatively close to the border though, maybe that plays a role. But id imagine bad mexican weed has less to do with growing conditions and more to do with care given to it, especially during the harvest. Sun-dried and brick cured weed isnt so nice, ya know?

    Ask any old school stoner who keeps up with todays strains, and theyll tell you the best shit they ever smoked was either thai, colombian, mexican, or jamaican. All humid (for the most part).

    the purpose of THC is under study, that is correct. However, trichomes as a dessicant is less so. To be effective as a dessicant, an oil would have to coat the leaf, as you said. However, this doesnt happen naturally.

    If there is no outside stimulus (ie, too much wind, you touch it), the resin stays within the glandular head of the trichome. When you say the oil coats the leaf, that implies to me that the trichomes have probably been handled too much, otherwise they will cover a small percentage of the surface area of the leaf. They may act as a buffer, kinda like hair works on us, but thats more as an insulator, and only minimally effective. You gotta remember, transpiration happens at the leaf, and the trichomes push away from that.

    well, arid environments have a lower air density as well. Less air mass/ per volume. Simple diffusion. When this occurs, the rate of penetration of ALL light increases substantially, as in more light penetrates the atmosphere and gets to your plant. this means that UV light is also increased

    it does produce THC in the summer. It produces it throughout its life cycle, just in low amounts. It steps the production up to protect its genetic line, when its budding. It buds when the light cuts because it detects the shortening day, and as such imminent death. As a survival tactic, it flowers to reproduce, and as such promotes cannabinoid production at an accelerated rate to protect its seeds.

    Also, there's something to be said for what kind of light is penetrating the atmosphere. Stretching (similar to red-shift in astronomy) comes into play, as well as angle, but what results is a higher ratio of UV light to visible light in the fall/winter, even though overall light is decreased. Note that equitorial strains (also known as the most potent) will flower through the winter and into the spring.

    just because you arent adding specified UV-B lights, there are still definately amounts of it present. LEDs can certainly be tuned out of the spectrum, but iirc HPS, MH, Flourescent, halogen, incandescant all produce at least some UV light.


    for those that dont want to read, here's the summary. You missed the point in uv-light. Its not to produce more THC within a single resin gland (although it may). The known benefit is in overall resin gland production. Many of the cannabinoids inside the gland absorb UV light, so indeed there may be some other variable that contributes more solely to THC production.

    However, UV-light does in fact promote resin gland production. Assuming each resin gland contained 1 part THC, would you want 100 resin glands or 1,000,000 in your bowl? id take the latter, thanks.

    Why am I so sure that my statement is true? There is just one study, and loads of anecdotal evidence supporting it. Because it makes sense.

    Im a mathematician with a decent background in physics, and I can assure you that an object like the resin gland can certainly take light from any point on its surface and reflect it to a single point, its how your dishnetwork tv works. So, to think that a plant uses them to shield UV-light from their seeds makes sense :

    -UV-light penetrates many semi-pourous substances, and is able to cause cellular damage.

    -Resin glandular heads are able to focus light to a single point, interestingly enough its the upper base of the stalk, where THC is synthesized.

    -Substances synthesized in this disc-cell are capable of absorbing UV-light.

    these are the kinds of correlations scientists like. clear, solid, step by step. the end result satisfies the original need.

    im not claiming that UV-light increases the percentage of THC vs. other cannabinoids. Humidity could play a factor in that. but using that assumption backwards to assume that UV-light has no role is ludicrous.

    Simply put, UV light increases the production of trichs. Trichs make THC. More trichs means more THC. simple, yes?
  9. #9 proteus, Feb 15, 2009
    Last edited by a moderator: Feb 15, 2009
    Amoril, I appreciate your beliefs about UVB and THC but I think you have misunderstood my argument. You claim that I am "making some poor assertions," but if you read my post carefully, I'm not making assertions but rather doubts about the claims of UVB and THC production. I did, however, state assertions from others. And I did make speculations but speculations are not assertions, (but it's revealing that you grab hold of speculations that support your belief but deny those that go against your beliefs).

    I claim no knowledge about the role of THC. I also proposed a counter claim to show that low-humidity during the flowering stage of cannabis shows a greater correlation to THC content than does UBV radiation. I am also not making any claims about low-humidity either (just the correlations), but I do state what others think about this.

    Again, I submit that I see little compelling argument for a case of increased THC by UV-B radiation and you have brought nothing new to the table. This does not mean that further research won't reveal a connection, only that has yet to be established by good scientific standards, (and one study is not good enough for a scientific establishment of a fact).

    However, I note that you make many assertions that either disagree with scientific research or need further clarification. For example, you wrote: "good luck finding a plant that naturally reflects UV-b light. won't happen." That's quite a bold claim and reflects ignorance of the many studies of flowering plants that show very strong reflection of UV radiation. Regardless of what you believe about this, it says nothing at all about a case supporting UVB and THC.

    As for your comment about the Brenneisen study, the point of my bringing it up was to show that other researchers think that other cannaboids show as good or better at UVB absorption than THC. I fail to see how CBC or CBD in hemp-grade makes a difference. Surely you must realize that drug-grade cannabis contains both CBC and CBD too, no?

    I admire your skepticism that you "don't think there's enough evidence to assume that CBC or CBD are more efficient at blocking UV-B light..." I wouldn't rely on one study either. But yet you appear more than willing to buy into the one study on the UBV-THC connection but reject the Brenneisn study. I find that revealing.

    In another of your assertions, you claim: "Just because 'stalked' trichomes arent present, the assumption that resin glands ARENT present is false. They are there. The fact that they were mroe [sic] obvious than normal indicates that the UV-light was in fact forcing resin glands to propogate at an earlier point."

    Of course I did not make any assumptions about what resin glands aren't present, but you're claiming facts here. On what scientific evidence? Sources please.

    And then you claim: "The cannabinoids do absorb the light, and that does transfer into a little heat. Not, a little. Not nearly as much as is already being produced by your lights."

    Where are you getting your information about UVB heat transfer vs. heat from other lights? Sources please. And are you not aware that adding a UVB source ADDS to the heat given off by the other lights, not to mention the lumen increase which could produce a healthier plant and, thus, could help increase yield (and greater THC content)?

    As for your belief that my "friend's" use of exclusive UV light grow was flawed, you failed to give a reason why you think it was flawed. I am puzzled.

    Then you called me on a claimed logical fallacy and that I skipped a few steps about my statement of poor Mexican weed, which I stated as "many times" it's poor not ALL. So just what logical fallacy did I commit? Indeed there are examples of excellent Mexican weed. Perhaps the best known is Acapulco Gold. But note that Acapulco is on the west coast in the desert area where the humidity is just right for growing weed and in the winter it's dry. Eastern Mexico, however, tends to have high humidity all year round (and as old timers will tell you, in the 70s, much of the Mexican weed was grown there and transported across the Texas border. It was generally considered a poor weed). And yes, some great weed comes from Colombian, Jamacian and Thai too, but as cannabis connoisseurs will tell you, the best is gown in the mountains where the growing conditions (including lower humidity) exist. Again, I submit that low-humidity has a correlation to THC, greater than than that of UVB. Whether or not either is right is open to further research.

    In another assumption, you claim that "trichomes as a dessicant is less so. To be effective as a dessicant, an oil would have to coat the leaf, as you said. However, this doesnt happen naturally."

    Anyone who has experience with living cannabis outdoors will tell you the best cannabis has very sticky leaves. Your assertion also goes against lots of research on this. In fact there are many plant studies that show one of the main purposes for glandular trichomes are to release hydrophobic oils to protect plants from desiccation. Of course you can choose to ignore these studies to make a case for your beliefs. But in doing so it weakens your argument.

    And yes you're right that "transpiration happens at the leaf". However when you say that "trichomes push away from that," on what evidence do you base this on? Are you not aware that the oils coat the top surface and not the bottom and that the stomata on cannabis are on the bottom surface of the leaf?

    As for my comment on the spread of cannabis from Indo-China, etc., and your assertion that UV light increases with lower air density, it's interesting that most of these countries are above the tropics where UV light is less intense. However even if there was high UV content, it does nothing against the correlation of low-humidity with high THC content, which is the point!

    In another assertion, you claim that there are "are still definately [sic] amounts of it [UVB] present. LEDs can certainly be tuned out of the spectrum, but iirc [?] HPS, MH, Flourescent, halogen, incandescant all produce at least some UV light."

    Well expert growers will tell you that you need only HPS lights to get cannabis through the veg and flowering and as long as you have good genetics and growing conditions, you can achieve high THC content. This is not just speculation. The very little UVB in HPS bulbs (if any) would be blocked by the glass in the bulb or the glass in the lamp cover. This is a very compelling argument that you don't need UVB at all to achieve high THC levels in cannabis. You can chose to ignore that too.

    Then you claimed that I "missed the point in uv-light. Its not to produce more THC within a single resin gland (although it may). The known benefit is in overall resin gland production."

    I fail to see how I missed the point. I wrote that "whenever you have more trichomes, you also get more THC." I said nothing about THC within a single resin gland.

    You wrote, "if there is a correlation between humidity and thc, its more likely an indirect one." Well I agree, and I thought I explained it in my post. As in many other plants, dry conditions spur the production of glands that release hydrophobic oil to protect against water loss. I suspect, as others do, that cannabis works similarly.

    Talking about unfounded assertions, you reveal your position by boldly asserting: "UV-light does in fact promote resin gland production. . . . Why am I so sure that my statement is true? There is just one study, and loads of anecdotal evidence supporting it. Because it makes sense."

    Well, now there's a grand assertion! I understand you believe this but you have not provided the slightest evidence to make your case. It may seem to make sense to you but it doesn't make a bit of sense to me.

    Lastly you wrote: "Simply put, UV light increases the production of trichs."

    Well we know that you need light to produce trichomes, but you have not established that UV light increases trichomes over other spectrums of light. Sorry.

    Now please understand that I don't wish to dissuade you or anyone else from your beliefs. After all, the placebo effect is very real and if someone believes that adding a UVB light will improve THC content and they they believe it gives them a good high, then, hey, that's what it's all about isn't it? :)

    However, I'm not interested in beliefs. I want to know, and beliefs have little to do with facts. Scientific investigation is the best way to achieve knowledge about nature, not anecdotal evidence. Facts are very difficult to establish and one study is not enough to establish a reliable fact. Many people believe in UFOs, ghosts, and pseudo-science nonsense, (and the UVB-THC hypothesis) with only the slightest anecdotal evidence, but I am not one of them.

    "Everyone is entitled to an opinion, but none of us is entitled to our own facts."

    --Daniel Patrick Moynihan
  10. im not going to quote anything direct to save space, this is outta control.

    I grant that other cannabinoids are as/more viable as THC at uv-b reception/absorption. If you pay attention, the video also acknowledges that. The argument is that it promotes the development of the resin glands. Not that it increases THC directly. the video recommends NOT using the uv-b bulb for the last few weeks of flowering, probably for the reason that youre pointing to (i think he even references the second study).

    More (quantity) developed resin glands = more potential THC. simple. thats your goal.

    the reason I so easily jump behind the study supporting this theory is that it was easily verified by myself. Using the same genetic pool, both visible trichs and end product potency was increased by substituting a 26w 6500k cfl for a 26w UV-b 10.0 5000k bulb. your mileage may vary, but mine was consistent with both the study and the consensus of veteran growers who experimented themselves.

    why is that different from the second study (brennenstein?) Im not stating that the study itself was flawed. Im saying its not very applicable to what we (im assuming all of us) want to do, create the most potent plant, not the most fibrous. we arent concerned with the hemp phenotype, nor with many of its characteristics. The study in question is using hemp-grade cannabis.

    Additionally, the second study doesnt exclude the recommendation of using uv-light. if, as im suggesting, uv-light promotes the development of resin glands, then it stands to believe that not using the UV light the last few weeks would be embracing the brennesein study's results. my argument is with your suggestion that the study implies a contradiction with the argument that uv-light increases thc. our suggestion to use the uv-light stems from a thoroughly tested indirect relationship. Thoroughly tested by 1 scientific study and countless grow ops.


    as a dessicant. Yes, grown outdoors, many leaves are sticky. as such, i see the logic behind the theory. but the reason they are sticky is from outside interference. something has brushed the leaf at some point, and caused the resin gland to burst. note, its possibly high wind, I dont know, but I know ive kicked some fans pretty high up my own and under a microscope they arent ruptured.

    it seems that if it were required to regulate moisture levels, the plant would naturally release the resin on its own AND that the resin would be more present throughout the entire life cycle, especially during vegetative growth when it has the highest exposure to dehydration.

    on that note, the trichomes/resin glands are very present on fan leaves at every stage, they just arent developed and as such produce only minimal amounts of resin. I dont need to cite a study for this, and I can haphazardly assert it....I have a pocket microscope, and they can be observed VERY easily in early vegetative growth at 100x magnification.


    you said uv-light --> increased trich development doesnt make sense to you. The gland forms a stalk, elevating the head above the plant material. In the process, a globular head is formed. this increases the exposed surface area of the gland, which coupled with the slight elevation actually serves to filter/shield the plant material below it, mostly from light (i say that because they're relatively easily disturbed).

    the globular shape of the resin head is remarkably uniform. look at it w/ your microscope, or look at good pics. they are the same, proportionally. this is because each head is able to focus the light entering its surfact to a single point. this, combined with its amazing coverage, is what leads to the correlation. obviously, trichomes serve as some sort of a light filter/absorption.

    note that if it were as a dessicant, it would probably be on the lower side of the leave, where transpiration actually occurs. Im sure it may serve a secondary function such as this, but in my opinion, thats a leap to say its the primary function/relationship.


    heres what vibe im getting. you dont think something can be considered a fact until a university puts its' stamp on it. Youre going to have a hard time finding double-blind, university grade research on cannabis. its illegal almost everywhere. and the research that is being done now is to learn about the shit like possible uses/effects, much less attention to production type research.

    however, you think the greeks did things so much more scientifically than a lot of todays growers? I dont. yet, they were able to establish many things as fact.

    Ill leave it at this. many of todays growers are brilliant people, who have come to apply themselves to cannabis. To say that the majority of us are fooled by a placebo effect is somewhat an insult. in my own experience, i noticed substantial trich development on ONE side of my plants only the first 2 weeks after adding my UV light.

    were there trichs everywhere on the plant? sure. were there more on the areas that faced the light? you better believe it. the difference between slight coverage and frosting at 5 weeks flowering. call it a placebo if you want, but im giving advice here.

    do i have a university backing me? not with anything related to cannabis.

    If you want to find out for yourself, set up 4 grows. 2 with UV lights, 2 without. in one of of the sets of 2, keep humidity around 15-20%, in the other set keep it around 50-70%. see what your results are, but keep in mind, you may be fooled by placebo effect, so what you see may be wrong....

    Apparantly the conclusions I/we have drawn from our experiences are the victim of the same fiesty culprit, our desire to believe ourself.

    as for me, im gonna go on ahead and keep my humidity normal and my UV-light on. and im going to smoke my heavily frosted buds. may you do the same.
  11. It's interesting to see that Marijuana Man used one particular scientific data to show that THC is derived from CBD. But like I said, a study or two does not make it into a scientific fact. Other research claims that THC is derived straight from CBG (not from CBD). (see Advances in Hemp Research, by Paolo Ranalli). Here is an excerpt:

    "Thc was long thought (e.g., Mechoulam, 1970) to be produced by the plant from cannnabidiol (CBD), which, in turn, is derived from cannabigerol (CBG) generated from noncannabinoid precursors (Fellermeier and Zenk, 1998; Turner and Mahlberg, 1988. This hypothetical scheme has also been tentatively supported by experimental evidence (e.g., Shoyama, Hirano, and Nishioka, 1984). However, recent work by Taura, Morimoto, and Shoyama (1995) has demonstrated CBG to be the direct biogenetic precursor of THC, at least in some strains."

    So here's another example of one idea supported by several studies contradicted by another study. Like I said, it takes a lot of research to uncover the truth about nature.

    Also Marijuana Man is claiming that UVB is used to *manufacture* THC. That was the point of the microscopic photos of the trichome gland. He later also states his *belief*(not knowledge) that people will "notice that it is growing more trichomes and filling them up with THC." Where he is getting his information on this is not stated. His only method of determining the THC level was how stoned he got! This kind of wishful thinking is not science.

    It's also interesting to to see the color graph Marijuana Man uses for UVB distribution on earth. He doesn't provide sources or who did the graph. According to his graph, high UVB intensity occurs only in the Northern hemisphere! I challenge that graph. Australia is well known for extremely high levels of UVB (along with high skin cancer rates). Antarctica also, because the ozone layer is virtually absent there, has high levels of UVB, yet Marijuana Man's graph shows Antarctica virtually absent of UVB. Clearly something is wrong with his hypothesis. It looks like psudo-science nonsense to me.

    Moreover, his hypothesis about good marijuana growing in tropical areas is also flawed because weed is not grown there naturally in the wild because of UVB or any other natural reason, but rather because the illegal marijuana cartels and drug growers have taken advantage of the geographical and social situation. It's difficult to grow acres of marijuana plants in populated northern countries simply because of the difficulty due to stricter law enforcement. This, of course is changing, and many plants are now grown in mid and northern areas of California, Canada, and even in the mid-west, not to mention that the indoor "hobby" grows are quickly spreading around the world. Lots of high-level THC marijuana is grown in these low UVB areas. And some off the highest known THC plants in the world are grown in indoor grow rooms or greenhouses without UV lights at all. In a few years (if not already) the majority of top marijuana may be grown indoors without UVB at all. Do you really think Marijuana Man will revise his graph to show where the highest THC productions are grown? I doubt it.

    As for the stalked glandular trichomes and their "magnifying" abilities to focus on the mid layer to create THC, this is also unsupported by evidence. He's talking out of his head. Do you realize that about 30% of all plants have trichomes? Glandular trichomes exist on many plant leaves and they look exactly like those on cannabis leaves. Lots of studies have been made and they are well known to protect the plant from dehydration and pests. None of them produce THC. To imply that cannabis glandular trichomes are there to build lens to make THC is streching the credibllity of reasoning. I mean, really!

    Like I said, the entire hypothesis doesn't make a bit of sense.

    As for your reason for jumping "behind the study supporting this theory is that it was easily verified by myself." Oh really? You say that visible trichs and end product potency was increased by substituting a 26w clf for a 26wUV-b bulb. How do you know that UVB did it or it the plant was simply stressed by the damaging influence of UVB? Many growers think that stress stimulates the growth of trichomes and there are lots of other ways to stress a plant without UVB and they are cheaper and safer. As for increased potency, how do you know? Are you just assuming that more trichs produced more potency? If so, that's a poor assumption. Experienced growers know that you can have a plant with hugh numbers of trichs but with very little THC in them. Even if UVB did increase the number of trichomes, how do you know that the UVB didn't help destroy the THC in them? How do you know? Or if you're determining potency by another method, how do you know how much THC has been increased? Do you own a gas chromatograph instrument or are you simply using your subjective head high? HOW DO YOU KNOW? I'm sorry but subjective opinions are hardly evidence for UVB and THC production.

    To actually determine whether or not UVB has a role in THC production, either by growing more trichomes or within the trichome head, you have to do controlled studies by eliminating all other possibilities. You just can't do a grow with a uvb light and proclaim success because of your eyes and mind. Science is done by measurements and determining tolerances and it require many experiments, not just one or two.

    In your guess that resin glands don't burst on their own, that only degrades your hypothesis. If, indeed, the purpose of THC is to protect the plant from damaging the plant, I suggest revise your mythical position. Hey, you don't want exposed leaf cells open to raw UVB now do you? :)

    I am puzzled by your slur on science about in comment that something cannot be considered a fact until a "university puts its stamp on it." Indeed laws are preventing research from being done on cannabis, but so what? We will just have to wait then. You can't force the truth about nature because of social limitations. However, science does not depend on universities. Anyone can do good science, but it takes discipline, the right measuring instruments, controls, documentation and peer review. But you're not going to do it by simply adding a uvb bulb and proclaiming a truth by subjective reasoning, sorry.

    I am not trying to discourage people from using UVB lights, but if you want to KNOW, I suggest that these growers not only document their grows but document the controls and the instruments they are using, and then submit their work for publication so others can review it. Unfortunately, chemical measuring instruments are expensive and most indoor growers don't have the money, the time, or the interest to really find out what is going on. So far all ll I have seen is wild guesses, and lots of pseudoscience. The slightest suggestion that something may improve THC is all they need. This is exactly the kind of reasoning people use for claiming the validity of horoscopes, magnet therapy, spoon bending, and other nonsense.

    Lastly you post a link to Ed Rosenthal's site about UVB lights. Note that he is saying nothing new, using the same implied one study reference on UVB. But Ed is, indeed, an experienced grower, and he is not fooled. He understands that one study in not enough by his penultimate sentence:

    "Not much research has been conducted on using them to produce higher THC values."

    Somewhere else on his website, Ed also points out another observation about bringing indoor plants into outside sunshine. As many amateur growers discover, if they suddenly expose their indoor plants to direct sunlight, they notice that the plants begin dying. Ed explains this as the plant not having enough time to adapt to the damaging effects of UV light. Plants grown outdoors from seed, however, don't have this problem. Clearly then plants have learned to protect themselves from UV at a very early stage, long before glandular trichomes develop. This doesn't occur just in marijuana but in plants with no THC at all, even in plants with no glandular trichomes at all!. Millions of plants (including hemp-grade cannabis), just don't need THC to protect them from UVB.

    I'm sorry but you have done nothing to improve your case.
  12. A note about quality

    The idea that one should try to increase the percentage of THC to a maximum level is understandable from a naive standpoint but It has always seemed to me similar to an alcoholic looking for a bottle of port with the highest content of alcohol. As connoisseurs will tell you, its not the amount but the quality that counts. Marijuana growers, including medical marijuana is chosen for the type of high, not just THC percentages. Indica will give a body high, sativa, a head high, and combining the two will get you what you want etc. So to try to increase THC levels via UV bulbs which could possibly degrade quality seems silly to me.

    However, if you really, really want to increase THC levels, there are almost certain methods of achieving it and all without the need for UVB bulbs at all. Moreover they are safer, cheaper and without the chance that it may degrade quality.

    1. First and foremost: choose a seed from a strain with good genetics that has proven to achieve high THC levels. It always amazes me that amateurs will balk at spending $20 or more on good seed but they will spend hundreds of dollars and added electricity costs for UVB bulbs on a hypothesis that has little scientific support.

    2. Growing conditions. You can't get strong weed if you don't grow in conditions that allow it to express its maximum phenotype. This means the right temperature, the right humidity levels, enough light (lumens being more important than spectrum), balanced nutrients, the right media to grow in, fresh air, etc.

    3. Using carbon dioxide during the flowering stage has been proven to increase yield, not only in cannabis but in hundreds of other plants. If you increase bud yield so does THC increase. It's a sure thing.

    According the many growers some of the ideal conditions are as follows:

    CO2 level at 1200ppm during flowering.
    Max leaf canopy temperature for max photosynthesis: 82F
    Nute temp at around 65F to 75F.
    Humidity 40% to 60%, with lower humidity at the end of flowering.
    Room temperature around 75%

    And if you want even higher percentage of THC to plant material, you can make hash or water cure your buds.

    Now I know that sodium lights, dehumidifiers and CO2 devices and balanced nutrients aren't as sexy as reptile lights and UVB LEDs but they are virtually guaranteed to increase not only THC yield but quality as well. So I would suggest that instead of putting time and effort into an unproven hypothesis, that people invest in the equipment that is *known* to increase yield and quality. Please note that once the plant's maximum phenotype is expressed, adding UVB lights simply can't increase past the limitations of its genes. At this point, UVB might only degrade the plant. Who knows? Why gamble on speculation when there are known methods that do work? Think about it.

    Now if you're really interested in the question about whether or not UVB has an affect on increasing THC, that's an entirely different thing. In this case, by all means experiment. But don't expect good results. To just assume that it will increase THC is only introducing bias. There are more chances that UVB will degrade THC than the other way around. After all, it's known that UVB is damaging to cells.
  13. ok, we both grant the trichs use as a protection/defense mech, although you maintain it may have more to to with being a dessicant ...

    anyhow, UV light and proteinase inhibitors (auditory defense systems)



    its the damage to cells we are after, it promotes a response, the development of trichs.

    if you want to think no uv light is going to benefit your grow, go ahead. the rest of us can go on doing everything we can to maximize our grow.

    and yes, substituting 26w of CFL light for 26w of UV enhanced CFL light has made a difference in my ~400w, 4 plant grows (HPS + cfl lighting).

    Have you actually used a UV light yourself, and basing your claims on your own experiences, or are you just 'reasoning' that it wont be a good idea? Just wondering, Im offering first hand experience.
  14. im going to try to grow for my first time and i was wondering will a norm. light bulb work cause i dont have grow lights:confused: plz answer as soon as possible
  15. If you mean by "norm. light" an incandescent light, yes, it should work as long as it's bright enough but it's probably the worst choice because incandescents are not efficient and they put out a lot of heat per watts, which could overheat your plants. They are also expensive to use compared to other lights.

    There are better choices such as CLFs, long tube fluorescents, MH (metal halide) and HPS (high pressure sodium) bulbs.
  16. amoril, that article is very interesting but I don't know what relevance it has to UVB and THC. It's well known that UV light is necessary for the production of vitamin D, for example, so it's certainly likely it has other purposes. It's also well known that many plants utilize UV to attract pollen carrying insects. However, the article is about UV light not UVB.

    You claim you substituted (not added) a CFL for a UV enhanced CFL. Yeah, right, how convenient is that now that you understand that adding a UVB would contribute to lumen output and it is *that* which could cause further growth (if any). Just saying it made a difference has absolutely no bearing on whether or not UVB ends up with more THC.

    Look, just making a claim or just saying so is not a convincing argument. People deceive themselves all the time. This is especially true for people who want to believe something is true and you have clearly demonstrated a bias toward using UVB. You have demonstrated no scientific rigor. Sorry man, no ill respect, but I just do not believe you.

    People who believe will find evidence for their belief, even when that evidence doesn't exist.

    "You can't convince a believer of anything; for their belief is not based on evidence, it's based on a deep-seated need to believe."

    --Carl Sagan
  17. you didnt answer the question. have you just reasoned that it wont work, or actually tried it yourself?

    ill prepare a more developed arg. later, I have to tend to my garden at the moment. priorities must be in order :)
  18. #19 ricard0, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009
    Now i'm not going to jump in between these two Mensa members (<--- meant to be complimentary), but.....

    I've seen amoril around for a while now and i must say that i personally respect his experienced-based advice.

    proteus, these will be your first posts i've had the tedious honor to peruse...... thoroughly.

    You both provide points worthy of debate. I'd like to point out that although gas chromatographs and mass spectrometers are fine and dandy, science made it quite a ways on observation, logical deduction and common sense. It may not sound very technical and the source may not have a lab coat on, but the power of observation is key here i believe.

    Since i've never used UVB light (save for the small amount provided by my CMH), i can't personally weigh in on the topic. That said, i've seen many respected members here and on others boards who at some point did not grow with supplemental UVB, but then they did. Not too many of them going back. That says alot to me, scientific fact or not.

    Do you think folks would keep using them if they didn't notice some tangible results? Or worse, doing harm to the plants? That's a tad presumptuous IMO.

    "UVB bulbs fried my weed, popped my trichs and cost extra $$, but i'm gonna continue to not only use them myself, but also recommend others do so as well". That either implies stupidity on ones part, or malice on another's.

    I don't need a professor of any tutelage to write me a prescription for common sense. Just my $.02.
  19. #20 amoril, Feb 17, 2009
    Last edited by a moderator: Feb 17, 2009
    had a link i wanted to share as well.... http://www.ukcia.org/research/opticsandthc.pdf

    its an article intended for use by medicinal patients only, seeking the pain-relief narcotic CBN effects.

    in reading the footnotes, there are several important ideas to take note of

    the first is the first footnote, where it clearly explains the math behind the refraction/magnification of the light going through the sphere and even points out the chromatic abberation, allowing for spectral integrity. good stuff. from the second note, we can infer that if THC is only present in the resin gland, that is where it is synthesized and that the resin gland is not connected to the plant material directly. thats gonna be useful later...

    they then give measures of uvb radiation at a couple of locations around the world, great for correlations if thats your bag. There's a more interesting note of my own related to this, but ill point it out lower.

    LOADS of great info on parthenocarpia, for anyone not familiar with long/short days, and their impact on fully realized potential potency. really a good read all around.


    now, my two problems with your assertions. First is that IF the primary function of the trichome in cannabis was to serve as an antidessicant, it should be present during the greatest exposure to light, veg. growth. while they are present, they certainly are NOT as active. Im 100% positive that there are moisture retention benefits, but to imply that it is the primary function, or even the controlling stimulus, seems to be overlooking more plausible answers.

    im going to admit, that after a TON of reading the last few days, I believe more now in UV light than I did before this conversation, but that I may have had the concept slightly wrong.

    UVB light, per photon, has more energy than UVA or any band of 'visible' light, photon for photon. how many photons are present is entirely different.

    that said, it appears that the higher energy state of UVB light is what allows for the higher production of THC, for possibly several reasons.

    the first, energy required to convert CBG -> CBD -> THC. higher energy levels in UVB allow for greater conversion. note that trichs are translucent to UVB light, and serve to bend the light, focusing all of it at the cells responsible for this synthesis.

    second, i believe the study was Pate in '83, since you so like studies, where they noted that in areas of high UVB, cannabinoid production actually skips a step and goes CBG -> THC. so, now we have some CBG -> CBD -> THC (chemical ecology of cannabis). And some CBG -> THC (pate) probably from the deterioration rate of CBD vs. THC. it seems that the extra energy is allowing for more overall synthesis

    third, the slight stressing to the plant (if in fact UVB is damaging to plant, im not convinced that it is). Rollitup had a really cool grow where a guy was using a 300w UV bulb, which created radiation levels of both UVA and UVB much higher than any found naturally on earth. The plant did fine. If it does stress the plant, obviously cannabis can adapt easily to it, and the resulting adaptation may be a good thing.


    now, heres what i really think of humidity. First, if there is a benefit, it seems more likely a stress related one. For example, a plant in an arid environment doesnt inherently recieve any additional stimulus from its surroundings (as would UVB light provide more energy/photon). The plant *may* respond to the dry stress by promoting trich development, but it doesnt seem likely that it would promote activity within this trichome.

    gotta remember, trichs arent connected with the same phloem/xylum type shit as plants, and as such particulate diffusion is probably minimal, if it exists at all(ive found evidence that phenol glucoside is transported into the disc cell through the stalk). instead, the trich acts as a closed system, producing its cannabinoids from energy it is able to collect/utilize on its own. Simply removing moisture from the plant may increase the number of trichs if this is true, but wont give you more THC. this explains why cannabinoids arent found in plant matter, but only connected to it.

    plant controls resin gland/trich development, but trich is on its own after that is my current hypothesis. good luck proving it, but oh well... i digress when i get stoned


    something interesting that hit me while i was with my ladies. Areas of low humidity (arid) WILL have a higher UV light penetration level. Not necessarily the other way around. Low humidity implies reduced amounts of particulate matter in the air, which means less reflection/refraction from the atmosphere, and voila, more UV.

    your correlation that the best weed comes from equatorial dry lands just reinforces this. Absolute most UV possible. A humid equatorial environment will recieve less direct UV and less UV overall (although there will be higher ambient UV levels (in the shade) because of refraction).

    however, to bunk the theory that humidity is the greater sole factor, consider that regardless of humidity, cannabis grown on mountains/higher elevations above 45 deg. north latitude produce almost no cannabinoids. itll grow, but it wont be dank. why arent the scottish highlands and the northern rocky mountains the shit for weed? theyve got the elevation, and more arid climatolgy, and yet they arent known for mindblowing weed.

    however, being in a dry (reduced ppm of contaminants), highly elevated, equatorial environment will provide the absolute most UV naturally available, and this happens to be what is considered the precious.

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