UVB grow light

[JaxsoNL5]

The reported terpene loss was most concerning to me. An extra 15% THC doesn't get me excited anyway as I think anything over 20 is largely academic and there is much more involved in the effect than THC. No doubt that intensity and period are important factors, but if UV supplementation was effective I would think the recent studies would consistently confirm it. They don't.

I totally feel you, and until there is defined research studies it’ll be a topic of debate. But until a study shows “hey we gave only small UV exposure and still there was no benefit” then the only true conclusions we can draw from the research is we have confidence that high intensity and prolonged UV exposure is detrimental to terpene development in flowering cannabis. Although it appears it may be true, none of the research I’ve seen can definitively state that low UV exposure is neither good or bad - that’s just a new hypothesis that needs to be tested.

So the interesting thing between the new researcharticles and the agromax one, timeframe! The agromax uv tube recommends short bursts spread over a few hours.

From the old research and new, I gather that timed bursts through the middle of the lighting period will be most effective. It sounds like the long intense UV exposure almost boils off the terpenes. The controlled exposure is enough to illicit the uv8r response without damaging the more fragile compounds.

Sort of how you can get a tan or a sunburn. You want to tan gently and not take all the radiation at once. It will be very interesting when more studies are done at research institutions.

Your last point is where my head has always stuck with this topic. It’s all about getting the “just right” amount, same with nutes and environment. Too much and you start getting negative effects from excess UV damage to your cells whether you’re a plant or animal - in this case the cells are those that make up the trichome stalks take the “hit” from then UV first to protect the plant. Since the trichs contain all the good stuff it makes sense that too much UV would damage the trichome cells and their contents.

Will say though, this discussion has me thinking hard about my UV regimen

 

[JaxsoNL5]

@CannabisMingus - I know tone can’t be received through text but I got nothing but respect for your view on the subject and you diving in to provide actual research. Might not seem that way because I keep responding with my opinion, but mad respect to you and all the AFN growmies putting in work.



Just enjoy engaging in topics I enjoy and with those that have different views on the matter, it’s how we learn and evolve IMO.

 

[CannabisMingus]

No worries mate - I am still trying to figure it out myself. It's all in the journey,

 

[Rick Dirte']

The kids put money in my PP account for
Christmas so I grabbed a couple of HLG 30w UVA bars to go in my 8'x4' grow space.
I'm running them on a 12/12 cycle on a separate timer from the lights (20/4). Interesting to me that HLG decided to sell UVA
bars only. As far as if it works or not? Hell I don't know. My Night Owl girls are getting frosty.

 

[DCLXVI]

It's still a very interesting discussion that pops up on here from time to time. I mean, wasn't it only a couple years ago that "blurple" lights were the latest and greatest? I'm really really green, pun intented, compared to almost everyone here but even I can see this field and hobby is growing astronomically. It is great to finally see some real world research being done with real testing and results. I genuinely hope the Federal laws here in the US change so more institutions can get to working with cannabis.

I am still beyond impressed with the level of science achieved by "stoners."

Also, I think most growers would benefit more from having an upgraded main lighting source, utilizing top tier genetics, and having a dialed nute program. Aside from some of the top guys here, like MoG, who have a killer lighting rig and perfected grow regimen, would the rest of us see a benefit from a say $100 UV light vs $100 of better seeds/water/medium?

 

[Rick Dirte']

DCLXVI I started 3 1/2 years ago and bought used Dorm Gro blurples on the auction site. I grew a lot of decent weed with them over 2 years.
When I bought my new lights, HLG 600R and a Grower's Choice ROI E680, I didn't see a big change in yield or quality. I was still learning how to grow indoors. A year and a half later and a lot of reading here and elsewhere, I'm getting better and can tell how much difference the
good lights make. Medium, nutrients, controlling environment and genetics are most important things to get a grasp of first.

 

[Wian]

Also, I think most growers would benefit more from having an upgraded main lighting source, utilizing top tier genetics, and having a dialed nute program.

Very true!

 

[CannabisMingus]

Will say though, this discussion has me thinking hard about my UV regimen

I guess my final thoughts on this (at least final for the moment ) is that for me:

1. It's still unresolved and until a better understanding of the intensity/periodicity issue arises it seems like you could easily do more harm than good.

2. The older research suggesting a benefit in terms of increased THC production may be compromised by the observation that more contemporary cultivars may be at the genetic edge of max THC production anyway. The risk that follows from that is that you could be significantly (and negatively) impact terpene profiles for marginal (2-3%?) gains, if any.

3. According to some, any UVB light that does not have adequate (or any) wavelength at around 285nm is incapable of triggering the UVR8 protein and thus enhanced THC production. At least according to Solarcure, that's what differentiates their products from others such as Agromax. There may be additional mechanisms at play with respect to high UVB spectra and their potential impact on cannabinoid levels. Alternatively, this could be wrong and is an overextended extrapolation/marketing statement by Solarcure.

4. I would think that if there was a clear connection between UVB supplementation (at whatever wavelengths) and enhanced cannabinoid production it would be easy to confirm experimentally. That seems not to be the case based on recent studies ("total equivalent Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) concentrations also decreased in LT inflorescences with increasing UV exposure level. While the total terpene content in inflorescences decreased with increasing UV exposure level in both cultivars, the relative concentrations of individual terpenes varied by cultivar. The present study suggests that using UV radiation as a production tool did not lead to any commercially relevant benefits to cannabis yield or inflorescence secondary metabolite composition.") The potential problems with this study in terms of intensity, etc. have been pointed out by others, but the study still gives me great pause.

IMHO, YMMV, etc.

 

[Olderfart]

I use UV screw ins for the last couple weeks, likely mostly or only UVA, and I I don’t know

wtf ??

whether they help.

I am, however, starting to think that a slightly bigger load in my vape is easier and cheaper, since I grow far more than I can ever use.

OTOH, my last batch of 24C is plenty strong, maybe my strongest, maybe due to the UV. I have to load lighter with it.

 

[CannabisMingus]

Thanks @DCLXVI @Olderfart - much obliged.