Correct Answer: A
Explanation:
The most important auxin found in plants is indole-3-acetic acid (IAA) The similarity of chemical structure of IAA and tryptophan suggested a connection between these. Considerable research has shown that tryptophan, one of the protein amino acids, is a precursor of auxin biosynthesis. Overall, the conversion of tryptophan to IAA can occur by:
(1) a transamination followed by a decarboxylation;
(2) a decarboxylation followed by a transamination; or
(3) formation of IAA via an oxime (C=NOH) and nitrile (CN).