Sorry to bother you, but you seem to be the person to come to for advice. I'm just looking for an explanation of why lighting is discussed "per plant"? If I had a 4 foot flourescent bulb, why would it matter if I had one plant under it or three? As long as they are not casting shadows on each other, aren't they still getting the same amount of rays straight from the source? I get the same tan on the beach, if I'm alone, or there are hundreds of people around.