Some strains will flower when they hit a certain maturity, as stinky said. I have heard of some strains flowering based on location to the equator as well. Except These plants took longer to flower the farther they were from there natural location. These were land race pure IBL to. I think It really depends on genetics, if a plant is ready to flower, than its gonna flower. No matter the amount of light. Its genetically programmed to do what ever it can, to continue the circle of life and re procreate.