UV B to increase THC

[BBFan]

Great post RT.
Thanks.

 

[Rolling Thunder]

From what I've read and been told, the UVB does 2 things- 1, it forces the plant to create more trichs to protect the calyxes from getting burned, and 2, it increases the conversion to THC from THCA and other cannabinoids.

In the ninth link, you will discover a 10.5 year old internet thread on the role of uvb in THC conversion. It contains a brief abstract of a controlled experiment conducted by ncga, regarding how much uvb supplementation to give your ladies. Ncga concludes that they should receive it throughout both the entire veg and flowering cycle, for maximum THC production. It is an interesting proposal, to say the least, and one well-worth some serious consideration.

The 'UV-B and It's Effects' link, designated above as link no. nine, is not so much a thread, strictly speaking, as it is a collection of posts originally made on the old Bcga website, over ten years ago now. It can be ascertained from several of the comments that Vic High, Soul, OT1 and ncga, had all been working with UV-B supplementation for several years, probably beginning in the early to mid 90's. I suspect that the 1987 Lydon study may have had something to do with that, which is referenced by both Clarke and Knuc:

"Pate (1983) indicated that in areas of high ultraviolet radiation exposure," (as Knuc duly notes,) "the UVB (280-320 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 UVB has also been experimentally determined by Lydon et al. (1987)."

Now, the 'ncga' controlled experiment made a very interesting discovery, relating to and developing upon your first point, BBFan, quoted above: "UVB ... forces the plant to create more trichs to protect the calyxes." For those who haven't looked at it (the ncga abstract) yet, it was a 3 year controlled experiment, consisting of 7 different controlled grows, begun in '93 and completed in '96, or thereabouts. This is the sum of what he (or they) discovered:

'Ncga's Brief Observations:-

"The bulb should be replaced every year. There seamed to be some drop off in the results after the first year but the results were still better than without UVB.

"I noticed that some plants had a hard time acclimating to the UVB. At first these low tolerance plant exhibited a lot of leaf curl or sunburn when introduced to the UVB. However the younger leaves quickly adapt to the UVB light.

"It is important to introduce the plants at a young (short) age so a most of the plant is exposed over a long period of time. The results are not as prominent over the entire plant and is less noticeable.

"In other words, a plant started with most of it exposed over its life to the UVB. The lower shoots if exposed when young will have more resin on them than those that were not exposed at a young age."[End of Ncga's Observations]

Not sure what 'ncga' stands for but I have often imagined it meant something like "North Carolina Grower's Association;" and that the grower known as 'ncga' was likely a member of that co-op, or maybe even one of its founders. If anyone knows for sure, please let us all know!

At any rate, whatever criticism might be made of the experiment, I think it has some merit and should be taken into consideration by all; and most especially by those who are yet unconvinced of the benefits of UV-B, to cultivating a more potent indoor bud.

Ncga directly observed, first-hand, over a period of 3 years, that "the lower shoots, if exposed when young, will have more resin on them than those that were not exposed at a young age." Now, this is a very interesting and useful observation, I think, as it is a strong argument for supplementing the plants with UV-B during the veg period as well; and not just when the trichomes begin to visibly form.

As Clarke states, light energy "is collected and utilized by the plant in a long series of reactions resulting in the formation of THC acids (MB, p. 135) It is reasonable to believe these chemical reactions to UV-B begin even during the veg period, when the plant is sizing up its enviroment, and pre-programing its defense mechanism for trich production. There is no question in my mind that the plant begins to react against UV-B from the very moment of its first exposure to it!!

It is very likely the chemical reaction to the UV-B is stored away, and that the more of it the plant has accumulated before the onset of its bloom, the more trichome it will produce. Continued reflection upon this leads me to believe it is somewhat irrational or unreasonable to think UV-B exposure during the veg period does not set or pre-program the plant for far greater trich production.

When ncga says that: "The results are not as prominent over the entire plant and is less noticeable," I take him to mean there that the enhanced trich formation, as a direct result of supplemental UV-B, is not as prominent or noticeable when it is introduced later, or even at the onset of trich formation. The earlier it is introduced, as ncga observes, the greater the difference it makes, over the entire plant and not just the top of its main cola.

At any rate, I thought the information under the `UV-B and It`s Effects` link would be of some interest to you all, for a variety of reasons, not least of which are the statements it contains by a few of the more advanced growers on the scene today, such as OT1, Soul, and Vic High, not to mention ncga. They were all insightful remarks, to be sure, but I was struck more by OT1`s observations and the findings of ncga`s controlled experiment.

OT1 is very keen to point out that potent equatorial drug cultivars are adversely affected by the stark absence of adequate UV-B light, indoors. He argues that the removal of the UV-B photon from the indoor light stream will cause a potent drug cultivar to mutate, or drift away from its genetic programing within a short span of four or five consecutive indoor generations.

In this connection, Joe Knuc observes that it is the pure equatorial sativas that stand to gain the most from supplemental UV-B, indoors! It is observed at one point that the Dutch seed companies realized their prized strains were experiencing a noticeable decline or drop-off in potency, which they could not attribute to any other limiting factor, except the missing UV-B photon. Once they discovered this, they introduced UV-B supplementation to their indoor crops.

So let us observe, then, that UV-B supplementation was already widely practiced in the Dam over ten years ago; and I suspect even more widely today, a full decade later! And it is very likely this experimentation has been going on even much longer than that, as King intimated; from at least 1987, with the publication of Lydon's definitive study. Btw, KK, please pardon my unfortunate oversight in failing to thank you earlier for your very interesting post. I share BBFan`s sentiment(s), in regard to your elaborating further on the details of your program/system:-

Sounds like a great set-up. I have a few questions. What are your lumens per square in that flower schedule? Do you switch the T-5's from cool to warm when you introduce the 12/12 schedule, or keep them blue? How are you delivering the UVB? What type of bulb? I'm using a reptile flood that has a pretty good rating but does generate heat that I have to battle?

I, too, am keen to learn the answers to the above questions; and others, concerning the LED`s. After all, it isn`t everyday we get to hear from someone with university level horticultural training! It was very interesting to read, for example, your observation about the decades old horticultural practice of supplementing indoor crops with UV-B lighting.

With regard to the LED`s, though, you appear to rate them very highly, mainly on account of their superior light spectrum; so I am naturally curious as to why you have`nt traded in the HPS yet for a 300w LED? Are you moving at all in the direction, or do you plan to carry on with the status quo, in terms of your current light set-up? I'd also like to know why you have decided not to supplement the CO2 levels, seeing the extent to which you have gone with the lighting?

RT


(Edited one word, changing "of" to "from," in rthe fourth paragraph from the bottom.)

 

[BBFan]

Again, another excellent post RT and thank you for helping disseminate the information for us.

I have not yet seen a response from King, but would be interested to see his follow up comments.

 

[Rolling Thunder]

Thanks, BBFan. I'm just glad to be of some minor assistance! Incidentally, when surfing the web earlier today, I came across a very interesting thread (somewhere else) on this subject, which will likely be of great interest to yourself as well. It's entitled: 'UV-B Lights?' @ hXXp://forum.grasscity.com/general-indoor-growing/336317-uvb-lights.html

 

[BBFan]

Thanks RT- I'll definitely check it out.

 

[leafminer]

Well, if you want to try the effects and don't mind the risk of UV burns or death through electric shock, remove the outer bulb from an HPS discharge lamp. But don't blame me if your plants curl up and die.

 

[Rolling Thunder]

Well, if you want to try the effects and don't mind the risk of UV burns or death through electric shock, remove the outer bulb from an HPS discharge lamp. But don't blame me if your plants curl up and die.

:holysheep:

 

[BBFan]

Well, if you want to try the effects and don't mind the risk of UV burns or death through electric shock, remove the outer bulb from an HPS discharge lamp. But don't blame me if your plants curl up and die.

Thank you very much for your concern and your constructive post! :aok: