plants have internal clocks, the response to light is dependent of what "time" of day it is....under 24 hours of light no plant will flower...this is due to an increased sensitivity to light during the time its supposed to be dark (last 12 hours of every 24)....plants put under constant darkness for days still exhibit these responses to light during their "dark" phase...they get their clock input from many different sources so there is no way to manipulate things to a longer "day"...just my 2 cents from some basic research