Question

Find an odd one out or the pair which is not correctly matched?
(a) Adenine derivative- kinetin
(b) Carotenoid derivative- ABA
(c) Terpenes- IAA
(d) Indole compounds- IBA
(e) Gas- ethylene

Answer 1

Indole-3-acetic acid is an acetic acid monocarboxylic acid in which a group of 1H-indol-3-yl has been substituted by one of the methyl hydrogens. It has a function as a hormone of animals, a metabolite of humans, a metabolite of plants, a metabolite of the mouse, and an auxin. It is a monocarboxylic acid and an indole-3-acetic acid component.

Complete answer:
The precursors to IAA are Tryptophan and Indole. Terpenes are commonly steroid precursors. Some insects that emit terpenes from their osmeteria, such as termites or swallowtail butterflies. They also have a heavy scent.
IAA is primarily produced in the apex (bud) cells and the very young leaves of a plant. IAA can be synthesized by plants via many independent biosynthetic pathways. Four of them originate from tryptophan, but independent of tryptophan, there is also a biosynthetic pathway. From tryptophan through indole-3-pyruvic acid, plants primarily generate IAA. IAA is also produced in Arabidopsis thaliana from tryptophan through indole-3-acetaldoxime.

Additional information:
In rats, along with tryptophol, IAA is a result of both endogenous and colonic microbial metabolism from dietary tryptophan. This was first found in Trypanosoma brucei gambiense-infected rats. The protein intake association was confirmed in 2015. There was no excretion of IAA by humans. Since the 1950s, human cells have been known to generate IAA in vitro, and the IL4I1 essential biosynthesis gene has been identified.

So, the correct answer is ‘Terpenes- IAA’.

Note:
IAA has several different effects, like all auxins, such as causing cell elongation and cell division with all resulting plant growth and development outcomes. On a larger scale, IAA acts as a signaling molecule essential for plant organ production and growth coordination.