In the 1970s, Dr Carleton Turner at the University of Mississippi found that there was a variation in the amount of THC in a sample, depending upon the time that the plant was taken. The most potent point was just before dawn after nighttime darkness.
Then, in 2000, Dr Paul Mahlberg of Indiana University showed that THC was produced extracellularly, on the inside of the glandular membrane, which would allow for its daily recycling.
The idea of using a dark period to increase THC before harvest warrants some investigation. An extended dark period right before harvest might very well increase THC content. I have done a couple of grows this way (24 / 48 hour ) I could not compare or test this experiment . I guess it's like letting a piece of meat " rest " after cooking it.