Obviously, we all know that light plays a key factor in the non-autoflowering varieties, but what are some of the chemical signaling pathways underlying that?
Here is a place to start.
Plants flower for reproductive purposes. Usually something environmental serves as a trigger. The plant senses that the season is ending (i.e. less light, more cold), or it takes advantage of a scarce resource (i.e. water, nutrients). In the case of nutrients for cannabis, Dyna-Gro has found that a jolt of phosphorous for a short time helps induce flower production. This is why on our feed chart we recommend a high rate of Mag-Pro during transition. Advanced Nutrients does the same with their Bud Blood.
The florigen protein is encoded by Flowering Locus T (FT), which is activated primarily by photoperiod (consistent from year to year) and temperature cues. Numerous other environmental factors, such as water and nutrient availability, lead to premature activation of FT. FT is expressed in leaves and the protein (florigen) translocates to the shoot apical meristem and partners with the Flowering Locus D protein to activate genes for reproductive structures. It is a reasonable hypothesis that auto-flowering strains constitutively express FT, and as soon as a plant is competent to flower, flowering begins regardless of the photoperiod.