NAA is a synthetic plant hormone in the auxin family and is an ingredient in many commercial plant rooting horticultural products; it is a rooting agent and used for the vegetative propagation of plants from stem and leaf cuttings. It is also used for plant tissue culture.
The hormone NAA does not occur naturally, and, like all auxins, is toxic to plants at high concentrations
NAA is widely used in agriculture for various purposes. It is considered to be only slightly toxic but when at higher concentrations it can be toxic to animals.
NAA has been shown to greatly increase cellulose fiber formation in plants when paired with another phytohormone gibberellic acid. Because it is in the auxin family it has also been understood to prevent premature dropping and thinning of fruits from stems.
It is applied after blossom fertilization. Increased amounts can actually have negative effects however, and cause growth inhibition to the development of plant crops. It has been used on many different crops including apples, olives, oranges, potatoes, and various other hanging fruits. In order for it to obtain its desired effects it must be applied in concentrations ranging from 20–100 µg/mL.
In micropropagation of various plants, NAA is typically added to a medium containing nutrients essential to the plants' survival. It is added to help induce root formation in various plant types. It can also be applied by spraying it onto plants and which is typical in agricultural use.
It is prohibited in many areas to use it in high concentrations due to the health concerns towards humans and other animals.