Rocket Soul wrote: ↑Mon Jun 24, 2019 5:26 pm
On 280ish / 360ish UV: theres some info if you google stomata aperture action spectrum (cant remember which one and no time to double check). They talk about the "3-finger action spectrum with several peaks, 280 / 360 being 2 of them. Granted its not cannabinoides but usually nature follows down the same paths.
Theres also info if you look up uvr8 (gene? Receptor? Random knows as usual...)
If this was already posted then sorry, havent caught up on the whole thread.
That would be this study into the UV action spectra, yes?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC58848/
But that's only a study into stomatal opening response to different wavelengths - not cannabinoid production. You did mention that, of course. And we know that secondary metabolite production as a defence mechanism is triggered by light saturation. So obviously, the more sensitive a pigment is to light, the sooner it is saturated, and the sooner the defence mechanism is triggered. That would be one assumption.
UVR8 activation (by UVB) as a catalyst to cannabinoid precursor chemicals is explained here:
https://www.maximumyield.com/uvb-a-crit ... is/2/17478
The Max Yield article doesn't mention that UVR8 is most sensitive at 285nm, but that is the case.
All good so far. The article also mentions the Maryland study that found a 33% increase in THC when the plant was exposed to 385nm, but no corresponding increase in CBD (in fact, no increase in CBD at all).
So it appears THC levels can be increased through UVA alone, but CBD levels are influenced (apart from genetics) mostly by UVB levels. That is, if we draw this conclusion from the above studies.
What is interesting about the first study is that, yes the 280nm response is 2.5x that of 420nm, but 420nm is 2.5x more responsive than 360nm - meaning 420nm is more efficient at regulating stomata than 360nm. (Also, if you read the study, the 285nm response is linked to the 459nm response - when either of those pigments are saturated, it doesn't increase photosynthesis by targetting the other one.)
However, if you go to yet
another study, you discover that two LED samples produced higher levels of cannabinoids than HPS, even though HPS produced higher yields:
https://www.karger.com/Article/Fulltext/489030
The kicker is that in this ^ study, the total amount of cannabinoids produced by all forms of light was the same! That is to say, HPS had lower levels of THC, but higher plant yields; LED had lower plant yields, but higher THC levels.
Does this mean that when a plant switches from primary metabolites (growth) to secondary (terpenoids), there is an equal trade-off? Well, the study seems to point to that . . .
But what I find most interesting is the LED sample that produced the highest THC, CBD and overall cannabinoid levels had a small amount of UVA, but the highest amount of blue (400-500nm). The highest yielding light with the lowest cannabinoids (HPS) also had a small amount of UVA, but the lowest amount of blue.
Have a look at the spectrum of NS1 - the highest cannabinoid producing LED light:
Look at that nice little bump around 405nm. And look at all the deep red. Kinda reminds me of this, LOL! (The original High Light spectrum)
![original.png](./download/file.php?id=3033&sid=af1f6eceab29c6e3797815027eae41ae)
- original.png (33.62 KiB) Viewed 1005 times
It appears the shorter blue wavelengths - likely including UVA - inhibit plant growth, but stimulate secondary metabolites, possibly as a defence against the higher amounts of radiant energy.
So what are we to conclude? That 285nm appears to be the most efficient way to stimulate cannabinoid production - but is also potentially the most damaging to plant DNA and detrimental to primary metabolism - and that 360-385nm UVA produces more THC, but not more CBD, however can probably be compensated for by high frequency blue around 420nm which
does appear to also target CBD - much like 285nm, which apparently triggers the same receptors/pigments as blue between 420 and 459nm (which have similar responses).
That's not gospel of course, but it's what I'm reading into all of this.