I found this on a ganja website, seems uvb is good for thc production, dosn't state about seedlings but? so guess I will have to grow it out and see.
Mick
"Article: UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH AND CANNABINOID PRODUCTION OF TWO Cannabis Sativa CHEMOTYPES.
By: JOHN LYDON, ALAN H. TERAMULA and C. BENJAMIN COFFMAN.
Department of Botany, University of Maryland, College Park, MD 20742, USA.
My estimated conclution: "Add 2 x 23w UVB lights / m2 to your grow room and increase THC levels up to 30% in buds."
Read this science article regarding UVB lights effect on drug type cannabis originated from high heigted tropical areas with highly elevated UVB levels. In experiments with plants they have shown an increase of THC concentration levels in leaves from in a range from 22% - 48% depending on UVB intensity. In flower trichomes they got an increase between 15% - 32%. Thats staggering news! Now, this is laboratory conditions with UVB lights flitered to emitt in 300 nm wavelenght UVB light. It's widely known that THC UVB absorption properties range between 280 - 315 nm, so that is important. There's no longer any doubt in my mind that UVB boosts the THC potency of drug type cannabis, and that dont having UVB light is not realising the full potential of our dear plants! Time for a change imho!
What id like to do is to get an estimate on how indoor growers could reproduce this results at home. To get an estimate on what lights, how much lights, and so on, wich could be beneficial. According to the scientists they used 240w UVB, but i dont know on how big of an area. The scientists says that 13,4 KJ / m2 is the level of UCB used in their trials, and that is as much as the UVB levels in 3000m altitude in mountains where strong marijuana is found to grow. According to the article marijuana grown in these UVB rich areas has a 33% increased THC content compared to the same marijuana grown at sea level.
Looking at wikipedia, i found that 1w = 3600 J (3,6KJ), but that seems a bit high compared to the ammount used by scientists, so I devided it to 0,36 KJ instead thinking i made some error somewhere. If i divide 240w (amount UVB scientist used) in 5m2, i get roughly 72w/m2, wich is around 14KJ according to my estimates, and that fits exactly and seems to be a fair estimate, so i think im on the right track here! Then, a 13w UVB light would give 4,5 KJ. Thats what i use, and that seems a bit lesser than needed. 2 x 23w UVB / m2 in the right spectrum should to the trick to produce massively strong cannabis with approximately up to 30% increased THC production in buds! I noticed the UVB bulb I use has the perfect spectrum for cannabis, repti glo 10.0. They come in 13w and 23w strength, and is avalible in sorted zoo shops.
Repti glo 10.0 UV spectrum chart:
It need to be stressed that UVB light is harmful to humans and plants that dont have developed defences to it (like cannabis has). When having such a bulb in the grow room, it need to be switched of when entering to room. Cancer is a known effect of UVB light exposure."
