Q.31 Which of the following is(are) auxins?
(A) 1-Naphthaleneacetic acid
(B) Indole-3-butyric acid
(C) 2,4-Dichlorophenoxyacetic acid
(D) Indole-3-acetic acid
All options (A), (B), (C), and (D) are auxins, commonly tested in CSIR NET Life Sciences exams on plant growth regulators.
Option Analysis
1-Naphthaleneacetic acid (NAA): This synthetic auxin mimics natural auxins, promoting root formation in cuttings and used in plant propagation.
Indole-3-butyric acid (IBA): Occurs naturally in plants as an auxin precursor converted to IAA via β-oxidation; widely used synthetically for rooting.
2,4-Dichlorophenoxyacetic acid (2,4-D): A potent synthetic auxin herbicide that causes uncontrolled growth in broadleaf weeds by mimicking IAA signaling.
Indole-3-acetic acid (IAA): The primary natural auxin in plants, regulating cell elongation, tropisms, and development.
Which of the following are auxins? This key CSIR NET question tests knowledge of plant hormones, focusing on 1-Naphthaleneacetic acid, Indole-3-butyric acid (IBA), 2,4-Dichlorophenoxyacetic acid (2,4-D), and Indole-3-acetic acid (IAA).
Auxins Overview
Auxins regulate plant growth through cell elongation, root initiation, and tropisms. IAA is the main natural form, while synthetics like NAA, IBA, and 2,4-D replicate these effects.
Natural vs Synthetic Auxins
| Type | Examples | Key Roles | Source |
|---|---|---|---|
| Natural | IAA, IBA | Cell expansion, root development | Plant endogenous |
| Synthetic | NAA, 2,4-D | Rooting hormone, weed control | Lab-made |
CSIR NET Exam Insights
All four options qualify as auxins per standard biology curricula. IAA and IBA occur naturally; NAA and 2,4-D are synthetic but auxin-active. Practice similar MCQs for Part B/C success.
