Yeah i'm also wondering if these examples do anything, but either way i am going to give the yeast thing a try, i will mix up a 2litre bottle of 1/2 warm water, 2 tablespoons salt, and 4 tablespoons sugar.......and i have no experience with this at all but i know that the mix i said will activate the yeast and produces gases i just don't know the effect.Another thing is, i am going to place the bottle just above my plant and i will attach a hose to it pointing to my plant because i beleive c02 is heavy than air, then bring the co2 down the entire plant, and again i don't know if this works, i'm just gonna try it.