I find it funny how many people present their responses as "de-facto."
Here's something to think about -
To the people claiming "PLANTS NEED A DARK PERIOD, BLAH BLAH BLAH..." I would wonder - WHY does a plant need a dark period?
What are the SPECIFIC reasons? Not just, "That's how it is in nature."
Some SPECIFIC DETAILS that outline WHY a dark period is required would be nice, especially if you are trying to convince anyone.
The dude above that outlined Ed Rosenthal seems to get it.
Some of the responses hurt my head as far as rationale or from a standpoint of anyone that has had a biology class.
THEY DO MOST OF THEIR GROWING AT NIGHT? LOL! Yes, they DO grow at night, but they can only grow with the STORED energy they have. (By 'stored' energy I mean the energy that was not used during daylight hours...)
Every grower I know uses 24/0 when possible. More light = more growth, provided optimum conditions.
I would put money on the 24/0 cycle producing more growth.