Indole Acetic Acid (IAA)
is a plant hormone or growth regulator, well known for causing curvature in roots and shoots, resulting in phototropism and geotropism. It is also called auxin
, and there are a number of similar compounds called auxins.
It is used in 'rooting powder' as a stimulant to root growth in cuttings, and it is known to cause growth of undifferentiated cells - 'callus' - in plant tissue culture.
However when sprayed on the outside of dicotyledonous - 'broadleaved' - plants it causes uncontrolled growth resulting in death, but it does not affect monocots in the same way.
The two-ring indole group
is also found in the amino acid tryptophan, and acetic acid
is also known as ethanoic acid.