Quote Originally Posted by Weezard

The UV is not necessary.

Cannabis will grow, flower, and become extremely potent with 0 UV.
Necessity aside for a moment, do you think that it's even helpful?

I thought some might be, as it was supposed to stimulate repair, help regulate morphology, and maybe boost disease resistance. One thing I read (plant photobiology
E. P. SPALDING & K. M. FOLTA) said;

[UV-b] induces DNA damage repair responses as well as a suite of
unrelated outcomes. These range from increases in cyto-
plasmic Ca2+ (Frohnmeyer et al. 1999), induction or patho-
genesis-related transcripts (Green & Fluhr 1995),
hypocotyl growth inhibition (Shinkle et al. 2004), and sto-
matal opening (Eisinger et al. 2000; Eisinger, Bogomolni &
Taiz 2003).

Quote Originally Posted by Weezard
And the far red, 730nm., is counterproductive unless it is applied at the appropriate times.
It's function is phytochrome conversion.
Far red can be used to hasten flowering when applied for an hour at "light's out".
As I understood it some far red helps to maintain the balance of the two conformations of one of the phytochromes (can't remember which, will look), which makes them healthier. Of course healthier is a biased word, and the authors of those papers were talking about general food crops.

From what you're saying the plant would be more vigorous if this balance was not maintained for most of the time. Frankly it seems unusual to me that an organism evolved in a particular environment would thrive just as well in an environment missing one of it's constituents, but then I had that reaction to the idea of a 24/0 light cycle which did turn out to work.

I'd really like to hear if anyone has done more specific experiments on these questions. Should do them myself and stop complaining I suppose.