Active auxins
IAA
IAA is the best-studied naturally occurring active auxin. IAA biosynthesis can occur through two major routes: tryptophan (Trp)-dependent and Trp-independent pathways (reviewed by Woodward and Bartel, 2005). Several Trp-dependent auxin biosynthesis pathways contribute to IAA levels, including the IAOx pathway, the IAM pathway, and the IPyA pathway