and some input from another well known head who knows stuff..(colonnuggs)
Returning to the more orthodox version of the cannabinoid biosynthesis, the role of ultraviolet light should be reemphasized. It seems apparent that ultraviolet light, normally supplied in abundance by sunlight, takes part in the conversion of CBD acid to THC acids. Therefore, the lack of ultraviolet light in indoor growing situations could account for the limited psychoactivity of Cannabis grown under artificial lights.
Light energy has been collected and utilized by the plant in a long series of reactions resulting in the formation of THC acids. Farther along the pathway begins the formation of degradation products not metabolically produced by the living plant.
These cannabinoid acids are formed through the progressive degradation of THC acids to CBN acid (cannabinolic acid) and other cannabinoid acids.
"The degradation is accomplished primarily by heat and light and is not enzymatically controlled by the plant."
CBN is also suspected of synergistic modification of the psychoactivity of the primary cannabinoids, THCs. The cannabinoid balance between CBC, CBD, THC, and CBN is determined by genetics and maturation.
THC production is an ongoing process as long as the glandular trichome remains active.
Variations in the level of THC in the same trichome as it matures are the result of THC acid being broken down to CBN acid while CBD acid is being converted to THC acid.
If the rate of THC biosynthesis exceeds the rate of THC breakdown, the THC level in the trichome rises; if the breakdown rate is faster than the rate of biosynthesis, the THC level drops.
Clear or slightly amber transparent resin is a sign that the glandular trichome is still active. As soon as resin secretion begins to slow, the resins will usually polymerize and harden. During the late floral stages the resin tends to darken to a transparent amber color.
If it begins to deteriorate, it first turns translucent and then opaque brown or white. Near-freezing temperatures during maturation will often result in opaque white resins. During active secretion, THC acids are constantly being formed from CBD acid and breaking down into CBN acid
edit to how they are arrived
THCA (THC acids as you put it) is not formed from CBDA.
THCA is formed from CBGA, CBDA is also formed from CBGA, as is CBCA.
CBGA (Cannabigerolic acid) is the precursor to most other cannabinoids.
It goes: Geranyl phosphate --> Olivetolic acid --> Cannabigerolic acid --> [THCA / CBCA / CBDA]