Question

This is the precursor of Indole-3-acetic acid
A. Methionine
B. Tryptophan
C. Glycine
D. Isopentenyl pyrophosphate

Answer 1

Hint:
Indole-3-acetic acid (IAA) is the most common naturally occurring plant hormone of the auxins class and often auxins and IAA are used interchangeably. It is a derivative of indole containing a carboxymethyl substituent.

Complete answer:
The most naturally occurring auxin, IAA, is synthesized from the amino acid tryptophan. The first step in the biochemical synthesis of IAA is the removal of the amino group from Trp by that enzyme aminotransferase to generate indole-3-pyruvate (IPA). Then, oxidative decarboxylation occurs in IPA catalyzed by monooxygenase to produce IAA. This process of auxin synthesis is highly conserved throughout the plant kingdom and is essential for almost all developmental processes.
Methionine is the precursor of ethylene hormone in plants. Ethylene is produced in gaseous forms which play an important role in inducing the ripening process for many fruits. It acts as a plant growth regulator and promotes senescence and abscission.
Glycine is one of the most widely used amino acids in plant nutrition and is used for the production of amino chelate fertilizers. The cell walls of higher plants are rich in glycine proteins.
Isopentenyl pyrophosphate is the precursor of isoprenoids. This precursor of isoprenoids is used by organisms for the synthesis of terpenes and terpenoids. Isoprenoids play a major role in the physiological processes of plants and animals.
Thus, the correct answer is:- Tryptophan.

Option ‘B’ is correct

Note:
IAA is produced naturally by plants in the cells of buds and in the cells of young leaves. IAA is mutagenic to mammalian somatic cells and possibly carcinogenic. It also may cause reproductive and birth effects in humans.