plants shouldn't react unless you put lights on for more than a few minutes. i sometimes have to tend my setup during the dark period, no probs. BUT, i never go more than 4 minutes...

and TOTAL darkness is not totally necessary, two of my previous outdoor gro's were done 50 feet from an hps night light (600w) and essentially had 24/7 in flower. it's not so much the light, as it is how much light...

love, kp