One can theoretically wake up photosynthesis system 1 with 660nm "deep red" , if you already have that spectrum in your lights supposedly that is sufficient. I use & supplement 660 nm & 730 nm all day , supposedly that uses both photosynthesis systems 1 & 2. UV for Carotenoids. I also have full spectrum led lights, qb and cob, they also contain deep red.. not enough 730 far red tho, hence the supplementation. 15-20 minutes eod, so last 15 minutes with lights on then I cut all lights but 730nm for another 15 min.
Too much only in the far red causes it too think it's in shade & can get branchy. So obviously it's for supplemental to existing lighting. I run both to fill in the screen faster for scrog, or that's what I tell myself I've heard others say that 730 during all day doesn't do much, but it's more cultivar/strain specific.
I also supplement in veg & flower, so they get used to the process? But i only short them time in flower, by 1hr extra of light. Not all of flowering either, I adjust slowly to replicate nature. In veg I supplement with uva as well as being sure to have 660nm & 730nm at 18/6 or 18/5.75 because 15 minutes of 730nm.
For preflower I decrease lights 2.5 hr or so every week till I'm at 12/12, a soft switch.. in flower stage I then start 13/11 to 13.5/ 10.5 for a few weeks and then go back to 12/12 for finish & 11/13 for flushing then 2 days of dark. I supplement uvb in last 3-4 weeks once I'm happy size wise & run more blue spectrum.
