as photosynthesis occurs...the plant uptakes nutrition...however, after it is full, it stops eating. So, that answers your thoughts about uptaking more just because the light is on...besides, you do feed at night in hydro...basically to keep the rootzone from drying out, and in case the plant get's hungry...just on a more limited basis. Like humans, if they don't sleep, they stress out. make sense? peace

I suggest you read a bit on photosynthesis and photoperiods...It will help you understand better.