...I don't think LST increases yield. You do that when you don't have much grow space and it allows the buds to grow upwards. Bending your plants actually stresses them to....
I believe LST (low stress training) DOES increase yield.
There are hormones called auxins that are responsible for directing the growth of a plant. The top, dominant growth contains a concentration of auxins that tells the rest of the plant:
I'm the top dog. Don't you dare try and compete with me by growing up to my level. When we TOP, FIM, LST, and even SCROG what we're doing is manipulating the distribution of auxins and allowing side shoots that would normally remain subordinate to take off and try and compete for the top dog position. With LST'ing, what you can wind up with is multiple shoots that all think they are the top dog. Instead of one large cola (main growth tip) at harvest with less significant bud sites elsewhere you can have many colas who each thinks it's the primary cola. None may be quite as large as if a single cola growth was pursued but the combination of them all can easily outweigh (literally) a single cola.
I'm no botanist but that's my understanding of what's going on.
You're right about grow space though--it keeps the plants shorter. Also, I believe LST'ing allows us to make the best use of lower wattage lights (say 400w or 250w and less) by counteracting their weaker canopy penetration abilities. With a 250w light it's better, yield-wise, to keep as much growth as possible at the same level.
And in my limited experience, LST doesn't stress the plants much if any at all. They seem to continue their vigorous growth without pause during LST.
$0.02
Use those plastic twisties to LST and some thin plant wire to then "ground" bud sites to the frame. It *can* still be a lot of work doing all that LST... but if you give some TLC now you'll get some sweet THC later!
