well i now the plants can only take n so much during a single lighting period. in 24 hour cycle the plants adapt to the constant light and are able to take in as much as they can and the recess. in an 18/6 schedule it forces the plant to take in lights for the 18 and recess and use all the nutes it has obtained during that phase of light. i feel this allows the plant to switch the light schedule with greater ease when you induce flower, 12/12. that is just my taughts as i have tried both 24 hours constant and 18/6 and i have better sucess, personally, when i swithc over the plants seem ot to get to stressed and growth triples as it should