Hey, What exactly does the 36 hr dark period do for the plants before flowering?

Thanks
morebuds4me Reviewed by morebuds4me on . First grow - GRAPEFRUIT 250 HPS in a cupboard. 3 fem. grapefruit and 1 hindu kush ( prob. male ;) ) I've been trying to scoure the net for any info. about gf. The one I have is a 75% c99 cross with a 'fruity' sativa. My plan is to harvest a little early as to maintain this plants original head high character. For Veg: Starting 24hrs for a week then reducing to /18/16 each subsequent week followed by a 36hour dark period prior to flowering Flowering: 12/12 for ~2months I'm planning on transplanting from Rating: 5