UVB to increase terpenes?

[Mañ'O'Green]

FWIW, I vertically installed (4) 24w T5HO 10.0 herp tubes that run approx. 30% UVA and 10% UVB. I just installed them so "first light" will be the last 4 weeks of flower of my current grow (day 17). Planning on ramping up to 4 hours/day in 30min. increments and watching closely.

The reason I didn't go the Agromax route is that I run a small (2x2.5x7') tent and the bulbs would be inches away from the plant. Too risky IMHO. I have no idea whether these herp tubes will be intense enough to cause an increase in cannabinoids/terpenes but we'll see.

On a side note, ran across some posts on another forum stating that in order for UVB to activate the gene that causes the THC increase, the output needs to extend down to 290 nm which Agromax and other bulbs (allegedly except for one) do not do. This may be inaccurate but I am drilling down on this and will share what I find, if anything. HTH, IMHO, YMMV, etc.

Those should work fine. Yes you definitely need distance from the plant canopy with the AgroMax.

 

[CannabisMingus]

The protein is UVR8 which is most sensitive at 285nm, near the lower limit of UVB. (according to wiki UVR8 - Wikipedia ). The manufacturer I was thinking of was Solacure: Cannabis (solacure.com)

However, just because it's most sensitive at 285nnm doesn't necessarily mean it will not activate at higher wavelengths I assume. Needs more research. Maybe @Mañ'O'Green has already been down this rabbit hole.

 

[DCLXVI]

Solacure is a pretty respectable company from what I remember.

 

[Mañ'O'Green]

The protein is UVR8 which is most sensitive at 285nm, near the lower limit of UVB. (according to wiki UVR8 - Wikipedia ). The manufacturer I was thinking of was Solacure: Cannabis (solacure.com)

However, just because it's most sensitive at 285nnm doesn't necessarily mean it will not activate at higher wavelengths I assume. Needs more research. Maybe @Mañ'O'Green has already been down this rabbit hole.

LEDs can get very narrow for the spectrum but not so with fluorescent. I suspect that UVR8 is not the only protein in the cannabis system effecting the terpene and THC.

Light is measured scientifically in wavelength units. The wavelength of visible light ranges from 400-700 nanometers (nm), a nanometer is a billionth of a meter. Light waves ranging from 10-400 nm are known as UV light. The Sun is a source of UV light, which is commonly subdivided into UV-A, UV-B and UV-C light. UV-C light is almost entirely absorbed by the atmosphere surrounding the earth. UV-A light measures between 400-320nm, UV-B is between 320-290 and from 290-100nm is UV-C.

I know for a fact that the two lights I am using improved my buds!

 

[CannabisMingus]

I suspect that UVR8 is not the only protein in the cannabis system effecting the terpene and THC.

I suspect you are right.

Also, UVB actually extends down to 281 I think but it's a continuum. Given that UVC is completely absorbed by the atmosphere, and 280-290 is just right above that, I would imagine the absorption of 280--290 nm by the atmosphere to be almost total. I assume UVB atmospheric absorption is inversely proportional to wavelength but what the hell do I know.

 

[Bruce Campbell]

Stupid internet rabbit holes....here's what I was able to find in the literature:

• Most of the literature mentions of UVB refer back to a single 1987 study by Lydon that found a 30% increase in THC (i.e., from 25% THC to ~32% THC) from UVB exposure for a single outdoor photo strain from Jamaica. This was intended to confirm a hypothesis by Pate (1983) who noted that cultivars grown at higher altitudes (which may have higher UVB exposure) tended to have higher THC and, therefore, THC may function to protect the plant from UVB.
• The study hasn't really been repeated, just often cited, since then. I found one study that looked at effects of far red and UVA (but not UVB) and found that far-red had a better effect on THC and CBD. It also indicates the relative proportions of each wavelength in the overall spectrum may be just as important as the individual intensities of each wavelength.
• There are two recent studies published this year by the same authors (here and here) that found no increase in THC or yield from UVB, although it did modify the terpene profile. All the data for total CBD was reported as "below detection limit" for whatever test method they were using, so they didn't really check effect on CBD. The second study added a second cultivar, which showed a decrease in THC and CBD with UVB, as well as increased tissue damage. I.e., it sounds like the reduction in THC/CBD was more likely due to general overall damage from UVB for that strain, which indicates UVB causes more of a general stress type response than a direct mechanistic response on cannabinoid production.
• MIGRO discusses types of UV lights and effects on plants (here, here and here). He kind of takes an on-the-fence stance, defers to discussions with Bugbee and Runkle, and just sticks to showing you differences in UV spectrums for various lights if you want to try it yourself.
• And, of course, Bruce Bugbee really wants to sell you a sensor!

Most of the academic recommendations for UVA/B are mainly related to non-potency benefits - e.g., hardier plants, can help fight pathogens, improve appearance / more trichomes, etc - but there's still no robust scientific basis for potency or yield benefits. There's also always the possible "yield-dilution" effect - if you cause a plant to focus on increasing cannabinoid concentration, it usually does so at the expense of producing less overall bud mass. Combine that with possible cultivar-by-cultivar variations, as well as photo vs. auto differences, and the concluding statement is usually always, "And, so...more research is needed."

 

[Cerebral Goo]

Hey guys so just wondering if anyone here has tried using uvb light fixture in the last few weeks of flowering to increase terpenes and essential oils?

Hey Stev, I used an Agromax, the same one MOG uses. It was my first autoflower grow and first indoors in 30 years so I can't verify how much it helped or not. I grew all Mephisto strains and what I can verify is that I'm really stoned! Used one 4' bulb in a 4x4. I started at 3 minutes a day at the start of the third week till harvest and ramped it up 2 minutes a day. The last two weeks I did one hour a day at 15 minute increments during mid light cycle which was 20/4
I missed the time frame to run the UVA, but will be using that this round as well.

Sorry, but didn't see this until now and that I couldn't be more helpful!

 

[GMEtotheMoon]

Been eyeing a California light works t5 strictly for this purpose. Still doing my research on the topic however. Following!

 

[WildBill]

I run a t5 uv light. I could not tell you if it improved things but it definitely did not hurt. My most recent grow turned out very well and the prior one had a pest problem that the UV light seemed to kill them all. Interesting but anecdotal.

I run this fixture with the UV bulb option:

GrowBright 2 Foot T5 Grow Light - Single | HTG Supply

The GrowBright Single-Lamp 2 Foot T5 Fixture is perfect for a wide variety of indoor garden lighting uses. Get it now with fast & discreet shipping guaranteed at HTG Supply!

www.htgsupply.com

This bulb: It's an option on the lamp.

AgroMax Pure UV T5 Bulb - 2 Foot | HTG Supply

AgroMax Pure UV Bulbs are specially designed to produce large amounts of UV light for growing plants indoors. Available at HTGSupply for a great price.

www.htgsupply.com

agromax bulb info

AgroMax Pure UV T5 Bulb – AgroMax

agromax UV article:

New Grow Hack Increases THC Levels By 28% – AgroMax

I have the same setup X 2 in my 4X4

Been eyeing a California light works t5 strictly for this purpose. Still doing my research on the topic however. Following!

Too expensive! The above is better.

 

[DCLXVI]

I'm probably going to upgrade to some solacure UV tubes for my new 4x4. The LED light in there is one of the bar style contraptions with adjustable bars. Going to slip the UVs in between. If you email them, they have a narrow ballast option to make it even easier. I'm thinking two 4' tubes, one on each end. I believe the sanitizing effect alone is pretty helpful, I know UVC is the real germ killer but lots of "stuff" can't handle an increased UV blast.