can one plant yield a pound
You wont get a pound LST or not. There is simply not enough light coverage. There is a 3' diameter of goo spectrum light on a 400. 3' in all directions, so with a reflector you will get about 80% of the concentration in the first 2' and after it drops way off.
It would take 16 colas each weighing an ounce. If you think you can get 16 colas in 3' space, have them all even in height, and know your shit, then grow it and post it. But i'm saying naw on this.