The Pfr effect is well documented and tested in plant science. A number of respected growers (including some on RIU) have tested, observed and verified that it does what its supposed to do. I haven't yet seen anybody do a full side by side just for this that could even remotely be considered a valid scientific test.but is it really worth the time, effort, and money, to have to mess around with another light for 5-15 minutes a day??
Sounds like diminishing returns to me. However, I look forward to seeing someone test this idea.
I use it to ensure that my long flowering sativas (the ones that just keep on growing) finish in a reasonable amount of time. much better than shortening my light period to an 11/13 day/night cycle. It works.
http://rollitup.org/t/the-far-red-thread.867665/