Auxin indole-3-acetic acid (IAA) is one of the most significant naturally occurring phytohormones in the plant kingdom and is involved in the regulation of almost all differentiation and developmental processes in plants. Despite extensive research, the biosynthesis of this essential hormone is still not fully understood. This study examined potential key enzymes of IAA biosynthesis at the genetic and biochemical levels to assess their significance within the various discussed biosynthetic pathways. This work supports the assertion that multiple, possibly redundant IAA biosynthetic pathways, depending on age, tissue, and environmental factors, regulate de novo biosynthesis in plants.