Blue light at night the controversy rages

MoPho said:

Do you use the far red both at lights out and before lights on? How long do you leave the far red on for? 10/15/30 minutes? Do you use the 13.5-10.5 schedule right when you flip or do you slowly ease into that schedule from 12/12?

Thanks
MP

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Cryptochromes are photolyase-like blue light receptors originally discovered in Arabidopsis but later found in other plants, microbes, and animals. Arabidopsis has two cryptochromes, CRY1 and CRY2, which mediate primarily blue light inhibition of hypocotyl elongation and photoperiodic control of floral initiation, respectively. In addition, cryptochromes also regulate over a dozen other light responses, including circadian rhythms, tropic growth, stomata opening, guard cell development, root development, bacterial and viral pathogen responses, abiotic stress responses, cell cycles, programmed cell death, apical dominance, fruit and ovule development, seed dormancy, and magnetoreception. Cryptochromes have two domains, the N-terminal PHR (Photolyase-Homologous Region) domain that bind the chromophore FAD (flavin adenine dinucleotide), and the CCE (CRY C-terminal Extension) domain that appears intrinsically unstructured but critical to the function and regulation of cryptochromes. Most cryptochromes accumulate in the nucleus, and they undergo blue light-dependent phosphorylation or ubiquitination. It is hypothesized that photons excite electrons of the flavin molecule, resulting in redox reaction or circular electron shuttle and conformational changes of the photoreceptors. The photoexcited cryptochrome are phosphorylated to adopt an open conformation, which interacts with signaling partner proteins to alter gene expression at both transcriptional and posttranslational levels and consequently the metabolic and developmental programs of plants.

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DocTim420 said:

Since cannabis produces significantly greater quantities of THC & CBD when exposed to UV-B exposure, one wonders why this spectrum is largely absent in most grower's flower environment.

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Thule said:

It doesn't. THC is not higher in UVB treated plants, potency might be though.

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DocTim420 said:

Two points. First, isn't "greater quantities of THC" and "potency", more or less, the same thing? And secondly, how does your opinion square with the following research?

Pate, D.W., 1994. Chemical ecology of Cannabis. Journal of the International Hemp Association 2: 29, 32-37.

"Another stress to which plants are subject results from their daily exposure to sunlight. While necessary to sustain photosynthesis, natural light contains biologically destructive ultraviolet radiation. This selective pressure has apparently affected the evolution of certain defenses, among them, a chemical screening functionally analogous to the pigmentation of human skin. A preliminary investigation (Pate 1983) indicated that, in areas of high ultraviolet radiation exposure, the UV-B (280-315 nm) absorption properties of THC may have conferred an evolutionary advantage to Cannabis capable of greater production of this compound from biogenetic precursor CBD. The extent to which this production is also influenced by environmental UV-B induced stress has been experimentally determined by Lydon et al. (1987). Their experiments demonstrate that under conditions of high UV-B exposure, drug-type Cannabis produces significantly greater quantities of THC. They have also demonstrated the chemical lability of CBD upon exposure to UV-B (Lydon and Teramura 1987), in contrast to the stability of THC and CBC. However, studies by Brenneisen (1984) have shown only a minor difference in UV-B 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. Two other explanations must now be considered. Even if CBD absorbs on par with THC, in areas of high ambient UV-B, the former compound may be more rapidly degraded. This could lower the availability of CBD present or render it the less energetically efficient compound to produce by the plant. Alternatively, the greater UV-B absorbency of CBC compared to THC and the relative stability of CBC compared to CBD might nominate this compound as the protective screening substance. The presence of large amounts of THC would then have to be explained as merely an accumulated storage compound at the end of the enzyme-mediated cannabinoid pathway. However, further work is required to resolve the fact that Lydon's (1985) experiments did not show a commensurate increase in CBC production with increased UV-B exposure."

And...

Lydon, J., Teramura, A. H. and Coffman, C. B. (1987), UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES. Photochemistry and Photobiology, 46: 201–206. doi:10.1111/j.1751-1097.1987.tb04757.x

"The concentration of Δ9-tetrahydrocannabinol (Δ9-THC), but not of other cannabinoids, in both leaf and floral tissues increased with UV-B dose in drug-type plants. None of the cannabinoids in fiber-type plants were affected by UV-B radiation."

Think about it, the cannabis plant is responding to an attack on it's leaf tissue caused by UV-B, by increasing trichome development (protection) on the affected plant tissues. Kinda simple of you think about it.

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Thule said:

First point, probably less. A lower THC strain can subjectively feel stronger. Has to do with terpenes and their entourage effect with the cannabinoids present.

That study seems outdated. "evolutionary advantage to Cannabis capable of greater production of this compound from biogenetic precursor CBD." We now know CBD is not the precursor of THC, but CBG is. If they got that wrong I can't put much value on the rest of it.

I'll have to read up on different sources to be sure, but the last time I checked there was no evidence of UVB having a positive effect on THC concentration, (resin maybe?) in fact the opposite was indicated as UV radiation degrades THC.

Reading this thread now, as I recall the Skunkman measured lower THC levels from UV treated clones, but perceived them stronger

https://www.icmag.com/ic/showthread.php?t=93829&highlight=ultraviolet&page=23
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DocTim420 said:

Thule, I believe the controls in the two studies I linked compared "apples to apples", the same strain was examined (UV-B treated vs no UV-B), so...although your conclusion that, "A lower THC strain can subjectively feel stronger" may be true, it really has nothing to do with this discussion. Things like different cultivator styles/techniques, grow mediums, amount of lumens, organic vs synthetics, etc...also affect the differences between two specimens...hence "a lower THC strain can subjectively feel stronger".

Nothing to do with this discussion? It was the answer to your question "[FONT=Arial, Helvetica, sans-serif]Two points. First, isn't "greater quantities of THC" and "potency", more or less, the same thing?"

It seems we have a different definition for potency. Potency is not the raw THC percentage, it is the intensity of the effect. One bud can be 20% THC and another only 15%. Still the 15% bud might be considered more potent by everyone who smokes it. Outdoor is usually perceived as stronger as the same stuff grown indoors, even though the indoor might have more THC.
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IMO, the ceiling (maximum) THC% is limited by the plant's DNA, while the floor (minimum) THC% is limited by the cultivator's abilities (or lack thereof). Simply said, it is impossible to take 9% THC strain, grow it and then have it magially test 25% THC--but the reverse is true, a 25% THC can easily test 9% if horrifically grown.

Agreed

Back to the UV-B discussion--so...let me understand where you are coming from. You suggest I am wrong when I say, "cannabis produces significantly greater quantities of THC & CBD when exposed to UV-B exposure", but instead of presenting peer reviewed published science...you rely on "stoner logic"?

Said differently, all you have to support your opinion, "THC is not higher in UVB treated plants" are conclusions of an old stoner on ICMag? Come on man, you gotta do better than that.

I said I will look into other studies. That takes time. I suggest you take a less hostile tone in the meantime.

The last time I went trough the studies the consensus seemed to be that higher UV does not make for not higher THC. If you can provide me with something peer reviewed and a little newer than 1994 I'm ready to check my facts.

I have had several discussions with Skunkman, and let's just say, he and I agree and disagree on many things; he is old fucker like me (both set in our ways) but in our discussions, he exhibited difficulty in believing/accepting things he never experienced personally. You might say, having a discussion with a person that puts more credence to "his personal experiences" than "facts"...makes for a very difficult discussion.

That said, I will give him credit for his knowledge, as he will forget more things about cannabis that many on ICMag will learn during their lifetime...but I definitely challenge Skunkman if he concluded tissues from UV-B treated plants exhibited lower THC%. Would love to see his data and procedures and have it replicated by professionals.

BTW, when you said, "THC is not higher in UVB treated plants, potency might be though", what are you trying to say? What does the word "potency" mean? In this instance, I think "potency" means: when comparing two or more items, the item having a greater amount of "active ingredient" (usually expressed as a percentage of weight) is considered "more potent" than the others. Example, two flower sample sent to the lab, each weighing 10 grams. Test results: 25% THC for one 15% for the other. That means amount of THC (active ingredient being tested) measured 2.5 grams in one sample and 1.5 grams (15% of 10 grams) in the other.

Potency = how high a standard sized joint gets you

So if "THC is not higher" (your words) in UV-B treated plants, then what active ingredient (potency) increased? You should be able to measure the increase (25% vs 15%), thereby removing the subjectivity variable (I think this one is more dank than that one).

So what increased if THC did not? Hmmmmm.

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Thule said:

The terpene profile changed.

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Phaeton said:

UVB testing was done for two years in a separate room designed strictly for side by side testing of lighting.

UVB supplements are now used for all stages of growth, 10 uw for clones, 50 uw for veg, and 100 uw for budding plants.

At no time during any of the testing did UVB increase plant size or the percentage weight of oil extracted by hexane.
One of the chemicals produced to protect from UVB caused a delay of effects from THC and a slightly longer duration of effect. Enough so that the UVB is standard even though the end effects result in roughly ten percent less harvest weight.

Just to be clear, only four strains of Marijuana were tested, a tiny tiny sample size and it would be most unusual for this to be a hard and fast universal rule.
More of a tendency of some strains.

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