Quote Originally Posted by fluid69
I just come across this thread that actually has some figures on the difference in root mass.

http://boards.cannabis.com/grow-faqs...ut-lights.html

here's a quote: [I]" Light Cycles

The dark cycle is very important to plants. Respiration (this is when plants are making energy from sugar to oxygen) Continues in dark but at a much slower pace, almost independent of available oxygen because the leaves are not making oxygen in the dark.
Really did not want to go down this path...again but I can't help myself, I need to comment.

This first quote is wrong scientifically: Respiration is REVERSED during the dark period. The plant STOPS taking in CO2 and giving off Oxygen (during the photoperiod regardless of length) and takes in Oxygen and gives off CO2 during the dark period. All C3 plants do this. And "sugar to oxygen" oh please dear God spare me! Read a horticultural textbook or take a class in school.
(directed at original post, not you fluid69)

Anything stated as a fact after that is useless BS.

I have been doing "asexual propagation via cuttings" (clonning is actually micro-propagation or tissue culture) for a long time and my personal observations differ a bunch from what's reported here.

Photoperiod and amount of dark period is a matter of what works best for an individual, the strain they are working with and enviromental considerations.

No one photo period is "BEST" for all situations. I use 18/6 for my mom's in one grow and 24/0 (just changed to 20/4) in another.