Here is what I could undestand for the N/D diff temp: basically you disturb (I belive termically) the giberellin hormones build up of the plant and thus keep the internodes spacing tighter.
There is a tecnique called cold dump which instead of completely keep the diff neg or neutral for the lenght of the day you just keep the next to zero diff in the first few hours of the day.
I'm really interested in that so if anybody can give any more pointers it would be great!
It seem somone was implying the more ppf on the canopy the less stretch? I've come across so many other factors in my research for informations! IR, blue vs red ratio, Fr VS r ratio, amount of green spectrum and also temps as someone else was saying leaving! aside fenotype and strains...