goldslinger wrote:More roots, more absorbtion, better growth.
I wonder if this is the correlation?
NAA is just a rooting hormone, no nutritional value or stimulus on anything else?
NAA is an auxin; like allied compounds (IBA, IAA), it inspires root growth. Kind of like with drugs that work on the mammalian autonomic nervous system (the old "alpha, beta, constriction, dilation thing), there are no absolutely pure forms of auxins and cytokinins- although some come very close. There's usually some overlap in effects.
But! For getting plants to throw better roots, NAA is tough to beat. Rule of thumb with all hormones: start at 1 ppm (1 mg/L), and work outwards to one order of magnitude (0.1 mg to 10.0 mg/L) until the desired effect is achieved. With some exceptions, this range works for most plant hormones in most crops.